Final Technical Report 

Fires Experienced and Halon 1301 Fire Suppression Systems in 

Current Weapon Systems 

1A/1 

February 2003 

Sponsored by: 

The Department of Defense 

Strategic Environmental Research and Development Program 

This project was not sponsored nor performed under the auspices of any particular program 

office, and is intended to serve only as a research tool to assist in improving the quality and 

relevance of current fire protection research to the operational military aircraft community. 

It is not an official or formal trade study or assessment of the merits of modifying the existing 

fire protection system design of the platforms specifically, nor is it intended to be such. 

Interpretations and simplifications have been made by the investigators in executing this 

project, to comply within the project scope and purposes for the R&D community and 

sponsors. 

The views and conclusions contained in this document are those of the authors and should 

not be interpreted as representing the official policies, either expressed or implied, of the 

Strategic Environmental Research and Development Program, 46 OG/OGM/OL-AC, or any 

other part of the U.S. Government. 

This research is part of the Department of Defense's Next Generation Fire Suppression 

Technology Program, funded by the DoD Strategic Environmental Research and 

Development Program. 
ii 

REPORT DOCUMENTATION PAGE Form Approved 

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

February 2003 

3. REPORT TYPE AND DATES COVERED

Final Report June 2000 – February 2003 

4. TITLE AND SUBTITLE

Fires Experienced And halon 1301 Fire Suppression Systems In Current Weapon 

Systems 

5. FUNDING NUMBERS

SP0700-96-D-4000 

6. AUTHOR(S)

A.E. Finnerty, P.J. Peregino, L.J. Vande Kieft, J.R. Tucker, D.E. Weiland, R.S. 

Sheinson, R.G. Gann, M.V. Bennett, J.A. Wheeler 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION 

 REPORT NUMBER

Booz•Allen & Hamilton Inc. 

4141 Colonel Glenn Hwy, Suite 131 

Dayton, OH 45431-1662 

 

SURVIAC TR-00-007 

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING / MONITORING 

 AGENCY REPORT NUMBER

46 OG/OGM/OL-AC 

2700 D Street Bldg 1661 

Wright Patterson AFB, OH 45433-7605 

 

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION / AVAILABILITY STATEMENT

Unlimited distribution 

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 Words) 

The goal of the Next Generation Fire Suppression Technology Program (NGP) is to develop and demonstrate retrofitable, economically 

feasible, environmentally-acceptable, and user-safe processes, techniques, and fluids that meet the operational requirements currently 

satisfied by halon 1301 systems in aircraft, ships, land combat vehicles, and critical mission support facilities. The results will be 

specifically applicable to fielded weapon systems and will provide dual-use fire suppression technologies for preserving both life and 

operational assets. 

The purposes of this project were: to characterize and tabulate the nature, frequency, consequences (including personnel injuries), and 

severity of fires previously and currently attacked using halon 1301; to derive a small set of representative (model) fires (using the 

analyses described above) for other elements in the Program; and to compile characteristics and limitations of the systems that new fire 

suppression technologies will replace or into which they will be retrofitted. The descriptions of the environments of the current 

systems compiled during this program will serve as boundary conditions for the new technologies to be developed in subsequent 

Elements of the NGP. 

14. SUBJECT TERMS 

halon 1301, Next Generation Fire Suppression Technology Program, aircraft, ground vehicle, ship, 

15. NUMBER OF PAGES

104

fire, engine nacelle, auxiliary power unit, dry bay, crew compartments, fuel tanks 16. PRICE CODE

17. SECURITY CLASSIFICATION 

 OF REPORT

UNCLASSIFIED 

18. SECURITY CLASSIFICATION 

 OF THIS PAGE

UNCLASSIFIED 

19. SECURITY CLASSIFICATION 

 OF ABSTRACT

UNCLASSIFIED 

20. LIMITATION OF ABSTRACT 

SAR 

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. Z39-18 

298-102
iii

TABLE OF CONTENTS 

Section Page

1.0 EXECUTIVE SUMMARY...........................................................................................................................1

1.1 TASK OBJECTIVES .......................................................................................................................................4

1.2 TECHNICAL PROBLEMS ...............................................................................................................................5

1.3 GENERAL METHODOLOGY ..........................................................................................................................5

1.4 TECHNICAL RESULTS ..................................................................................................................................5

1.5 IMPORTANT FINDINGS AND CONCLUSIONS..................................................................................................5

1.6 SIGNIFICANT HARDWARE DEVELOPMENTS .................................................................................................6

1.7 SPECIAL COMMENTS ...................................................................................................................................6

1.8 IMPLICATIONS FOR FURTHER RESEARCH.....................................................................................................6

2.0 BIBLIOGRAPHY .........................................................................................................................................6

3.0 DETAILED DESCRIPTION OF THE PROJECT....................................................................................6

3.1 INTRODUCTION............................................................................................................................................6

3.1.1 Goal of the Next Generation Fire Suppression Technology Program (NGP) .......................................6

3.1.2 Purposes of This Project........................................................................................................................6

3.1.3 Sources of Data on DoD Fire Experience .............................................................................................7

3.1.4 Model Platforms ....................................................................................................................................7

3.2 FIRE/EXPLOSION EVENTS ENCOUNTERED ON CURRENT WEAPONS PLATFORMS.......................................12

3.2.1 Ground Vehicle Crew Compartments..................................................................................................12

3.2.2 Aircraft Dry Bays.................................................................................................................................22

3.2.3 Aircraft Engine Nacelles......................................................................................................................27

3.2.4 Aircraft Fuel Tanks..............................................................................................................................34

3.2.5 Shipboard Machinery and Storage Spaces ..........................................................................................36

3.3 MODEL FIRES AND FLAMES FOR USE IN RESEARCH ON ALTERNATIVES TO HALON 1301........................39

3.3.1 Mist Fireball Explosion .......................................................................................................................39

3.3.2 Spray Flame.........................................................................................................................................39

3.3.3 Obstructed Pool Fire ...........................................................................................................................39

3.3.4 Inert Atmosphere .................................................................................................................................39

3.4 DESCRIPTION OF REPRESENTATIVE HALON 1301 SYSTEMS IN CURRENT WEAPONS PLATFORMS .............39

3.4.1 Ground Vehicle Crew Compartment Halon 1301 System Configurations...........................................40

3.4.2 Aircraft halon 1301 System Configurations.........................................................................................48

3.4.3 Shipboard Machinery and Storage Spaces halon 1301 System Configurations ..................................71

4.0 TECHNICAL PROBLEMS .......................................................................................................................83

5.0 RECOMMENDATIONS ............................................................................................................................83

6.0 CONCLUSIONS..........................................................................................................................................83

7.0 REFERENCES............................................................................................................................................84
iv

LIST OF FIGURES 

Figures Page

FIGURE 1. PROJECTILE PENETRATION OF A WING LEADING EDGE...............................................................................25

FIGURE 2. M992 FAASV AMMUNITION RESUPPLY VEHICLE FIRE EXTINGUISHING SYSTEM SCHEMATIC...................42

FIGURE 3. M1 TANK FIRE EXTINGUISHING SYSTEM SCHEMATIC .................................................................................45

FIGURE 4. M2, M3 BRADLEY FIGHTING VEHICLES FIRE EXTINGUISHING SYSTEM SCHEMATIC...................................47

FIGURE 5. C-130 FIRE EXTINGUISHING SYSTEM SCHEMATIC. .....................................................................................51

FIGURE 6. F/A-18C/D FIREXX BOTTLE INSTALLATION.............................................................................................54

FIGURE 7. F/A-18C/D HALON BOTTLE AND DISCHARGE PIPING INSTALLATIONS BOTTOM VIEW. .............................55

FIGURE 8. HALON BOTTLE AND DISCHARGE PIPING INSTALLATIONS SIDE VIEW........................................................56

FIGURE 9. C-17 FIRE EXTINGUISHING SYSTEM SCHEMATIC (86 IN3). ..........................................................................59

FIGURE 10. H-60 FIRE EXTINGUISHING COMPONENTS LOCATION...............................................................................62

FIGURE 11. H-60 ENGINE FIRE EXTINGUISHER INSTALLATION....................................................................................62

FIGURE 12. H-60 ENGINE FIRE EXTINGUISHER INSTALLATION....................................................................................63

FIGURE 13. CH-47 FIRE EXTINGUISHING SYSTEM SCHEMATIC. ..................................................................................66

FIGURE 14. F-16 FUEL INERTING SYSTEM SCHEMATIC................................................................................................69

FIGURE 15. FUEL INERTING EQUIPMENT......................................................................................................................70

FIGURE 16. HALON TANK ASSEMBLY..........................................................................................................................71

FIGURE 17. DDG 51 (ARLEIGH BURKE) CLASS: AEGIS GUIDED MISSILE DESTROYER FIRE EXTINGUISHING SYSTEM 

SCHEMATIC.........................................................................................................................................................75

FIGURE 18. . LHD 1 (WASP) / LHA 1 (TARAWA) CLASS: AMPHIBIOUS HELO/LANDING CRAFT CARRIERS FIRE 

EXTINGUISHING SYSTEM SCHEMATIC.................................................................................................................82
v

LIST OF TABLES 

Tables Page

TABLE 1. M1/M1A1 FIRE INCIDENT DATA..................................................................................................................13

TABLE 2. DETAILED BREAKDOWN OF GROUND VEHICLE FIRE INCIDENTS, 1988-1990...............................................14

TABLE 3. CREW SURVIVABILITY CRITERIA. .................................................................................................................21

TABLE 4. CATEGORIZATION OF WING DRY BAYS........................................................................................................23

TABLE 5. CATEGORIZATION OF FUSELAGE DRY BAYS. ...............................................................................................23

TABLE 6. SHIPBOARD HALON 1301 DISCHARGES ........................................................................................................37

TABLE 7. SHIPBOARD HALON 1301 SYSTEM PERFORMANCE.*....................................................................................37

TABLE 8. M992 FAASV AMMUNITION RESUPPLY VEHICLE FIRE SUPPRESSION SYSTEM CONFIGURATION. ...............40

TABLE 9. M1 TANK FIRE SUPPRESSION SYSTEM CONFIGURATION...............................................................................43

TABLE 10. M2, M3 BRADLEY FIGHTING VEHICLES FIRE SUPPRESSION SYSTEM CONFIGURATION. .............................46

TABLE 11. C-130 FIRE SUPPRESSION SYSTEM CONFIGURATION..................................................................................49

TABLE 12. F-18C/D FIRE SUPPRESSION SYSTEM CONFIGURATION. ............................................................................52

TABLE 13. C-17 FIRE SUPPRESSION SYSTEM CONFIGURATION....................................................................................57

TABLE 14. H-60 FIRE SUPPRESSION SYSTEM CONFIGURATION. ..................................................................................60

TABLE 15. CH-47 FIRE SUPPRESSION SYSTEM CONFIGURATION.................................................................................64

TABLE 16. F-16 FIRE SUPPRESSION SYSTEM CONFIGURATION. ...................................................................................67

TABLE 17. DDG 51 (ARLEIGH BURKE) CLASS: AEGIS GUIDED MISSILE DESTROYER HALON 1301 SYSTEMS. ...........71

TABLE 18. DDG 51 (ARLEIGH BURKE) CLASS: AEGIS GUIDED MISSILE DESTROYER HALON 1301 SYSTEM 

DESCRIPTION. .....................................................................................................................................................72

TABLE 19. DDG 51 (ARLEIGH BURKE) CLASS: AEGIS GUIDED MISSILE DESTROYER FIRE SUPPRESSION SYSTEM 

CONFIGURATION.................................................................................................................................................72

TABLE 20. SYSTEM ACTIVATION/SEQUENCE OF EVENTS.............................................................................................76

TABLE 21. LHA – 4 USS NASSAU HALON 1301 SYSTEMS. .........................................................................................76

TABLE 22. LHD – 3 USS KEARSARGE HALON 1301 SYSTEMS....................................................................................77

TABLE 23. LHD 1-4, LHD 5-7, AND LHA HALON 1301 HALON 1301 SYSTEM DESCRIPTION......................................78

TABLE 24. LHD 1 (WASP) / LHA 1 (TARAWA) CLASS: AMPHIBIOUS HELO/LANDING CRAFT CARRIERS FIRE 

SUPPRESSION SYSTEM CONFIGURATION.............................................................................................................79

TABLE 25. SYSTEM ACTIVATION/ SEQUENCE OF EVENTS............................................................................................83
1

1.0 Executive Summary 

 The goal of the Next Generation Fire Suppression Technology Program (NGP) is to 

develop and demonstrate retrofitable, economically feasible, environmentally-acceptable, and 

user-safe processes, techniques, and fluids that meet the operational requirements currently 

satisfied by halon 1301 systems in aircraft, ships, land combat vehicles, and critical mission 

support facilities. The results will be specifically applicable to fielded weapon systems and will 

provide dual-use fire suppression technologies for preserving both life and operational assets. 

 The purposes of this project are: 

• To characterize and tabulate the nature, frequency, consequences (including 

personnel injuries), and severity of fires previously and currently attacked using halon 

1301. 

• To derive a small set of representative (model) fires (using the analyses described 

above) for other elements in the Program. 

• To compile characteristics and limitations of the systems that new fire suppression 

technologies will replace or into which they will be retrofitted. The descriptions of 

the environments of the current systems compiled during this program will serve as 

boundary conditions for the new technologies to be developed in subsequent 

Elements of the NGP. 

 There are a large number of platforms that have halon 1301 fire-suppression systems. 

Obtaining information on all of these would be difficult, costly, and unnecessary. Therefore, the 

Military Services identified a small subset of these platforms whose halon systems are 

representative of the range of fire suppression needs: 

• Ground vehicles: M992 (FAASV), M1 tank, and M2/M3 (BFSV) 

• Aircraft: C-130, F/A-18 C/D, C-17, H-60, CH-47, F-16 

• Ships: DDG 51, LHD 1/LHA 1 

 In order to characterize and tabulate the nature, frequency, consequences (including 

personnel injuries), and severity of fires previously and currently attacked using halon 1301, the 

Safety Centers of the Services and the Survivability/Vulnerability Information Analysis Center 

(SURVIAC) were contacted for both noncombat and combat data, respectively. Items such as 

fire zone, fire incidence rate, hazards to be protected against by halon 1301 system, flame 

suppression time requirements, and the current system tests were investigated. 

 Ground vehicles experience a wide variety of fires. The nature of these fires in peacetime 

is somewhat different from that experienced in combat. In peacetime, the significant 

contributors to crew compartment fires include the fuel in the hull cells next to the driver, 

hydraulic fluid in the turret hydraulic system, hydraulic fluid in the main gun recoil mechanism, 

the fuel-fed personnel heater, and ammunition stowed in the turret and the hull. The most 

common types of fires to occur in combat vehicles are the mist fireball explosion, pressurized 

hydraulic spray fires, and dry bay fires. Combat fires are initiated by a variety of weapons 
2

(mines, air attack weapons). Hot fragments or incendiaries produced from ballistic impacts 

ignite the fuel and hydraulic components where the fluids may be released in a spray of droplets. 

From 1988 through mid-1991, there were 178 peacetime incidents. The automatic fire 

extinguishing system was effective thirty-four percent (61 out of 178) of the time for the 

M1/M1A1. The frequency of fire incidents is a function of the exposure of the vehicle to 

combat. The single most lethal damage mechanism to ground vehicles in combat is fire. Fires 

can be initiated by a variety of weapons, and in all cases, they can cause a rapid kill of the 

vehicle and its crew. Internally stowed munitions such as gun rounds and missiles, fuel tanks, 

and hydraulic systems all provide substantial fire sources. Because fire can kill so quickly, 

rapid-reacting fire suppression systems have been developed. 

 The majority of peacetime aircraft dry bay fires are due to an equipment failure in a 

fuselage dry bay or failure of the engine or starter that results in damage to a fuselage dry bay. A 

large number involved wing fire damage due to equipment failures. Combat dry bay fires are 

usually created when a ballistic projectile impacts a dry bay in flight, rupturing fuel system 

components and generating tremendous ignition energy. Although this is the assumed primary 

initiation means, other initiation sources such as overheated, shorting electrical circuits in 

avionics bays, some other form of impact (i.e., bird strike), or burning stored munition 

propellants can also be responsible in rare instances. Data from Southeast Asia (SEA) suggest 

that fifty-eight percent of the twenty-four C-130 incidents were related to dry bay fires. The 

C-130 incidents were reported in which engines and/or adjacent bays were damaged by gunfire, 

creating numerous ignition sources, leaking fuel, and resultant fires in the leading and trailing 

edges. Dry bay fires can result in loss of aircraft assets either in combat or noncombat 

operations. 

 Aircraft engine nacelles have fluid lines that are routed within the enclosure on the 

exterior of the machinery, to provide fuel, oil or hydraulic/brake fluid for the machinery (all of 

which are flammable). In a typical peacetime fire scenario, one of the fluid lines leaks, and 

sprays or streams the flammable fluid onto the hot machinery, which results in a fire. Most 

engine nacelle incidents occurred during peacetime. Nonetheless, the potential of a combatinduced engine nacelle fire definitely exists and is currently being considered in several ballistic 

engine nacelle programs. However, fire protection systems are certified to the safety hazard and 

not to a combat induced hazard. Peacetime aircraft engine nacelle fire incidents are maintained 

by the Safety Centers of the various Services. SURVIAC maintains numerous combat databases. 

Data from these repositories are discussed in this report. Aircraft engine nacelle fires can result 

in loss of aircraft assets either in combat or noncombat operations. 

 Ullage (the void space above the fuel level in a fuel tank) in aircraft fuel tanks can have a 

potentially explosive fuel-air mixture. If initiated by a combat threat, an explosion can result. 

Fuel tank explosions are a result of ullage deflagrations where the combustion overpressure 

generated exceeds the structural strength of the tank. With large ignition sources, combustion 

will occur and overpressures will vary according to the threat level, tank volume, and oxygen 

concentration. If the combustion wave propagates throughout the ullage with near stoichiometric 

fuel/air mixture, a pressure increase of over 790 kPa (100 psig) (eight times atmospheric 

pressure) is theoretically possible. Fuel tank explosions are not frequent during peacetime. They 

are more a function of a combat incident. Historically, fuel fire and explosion is a major cause of 
3

aircraft losses in combat. Data from Southeast Asia show over half of the aircraft combat losses 

involved fuel fires and explosions. While other factors might also have contributed to the loss 

(e.g., pilot killed, loss of control, etc.), this fact, nonetheless, indicates the fuel system is a very 

significant contributor to an aircraft’s vulnerability. Therefore, to increase survivability, various 

techniques are used to reduce the vulnerability of the aircraft’s fuel system to this significant 

threat effect. 

 Fires in MMRs, AMRs, engine enclosures, and generator rooms result from the ignition 

of a pressurized fuel (diesel/hydraulic or lubricating oil) leak or ignition of fuel-soaked insulating 

material. Leaks onto hot surfaces result in three-dimensional spray fires with cascading liquid 

flow on complex surfaces and into flaming pools. Fires in FLSRs and paint issue rooms result 

from burning fuel cascading over highly obstructed and fuel loaded shelves and into flaming 

pools. The LHD class has high pressure steam plants. The steam plants have high temperature 

piping that can provide possible ignition and reignition sources. Further, these pipes are slow to 

cool. While turbine and diesel propulsion plants have high temperature surfaces, these cool 

much faster. Unvented high-pressure steam remains in the steam plant piping after engine shut 

down. Peacetime fire incidents data are discussed in this report. No combat data were available. 

The Navy started installing halon on ships in the 1970s following several disastrous machinery 

spacey fires where fuel and lube oil were released under pressure. 

 Previous research, development, testing and evaluation have led to the identification of 

ways to provide halon-equivalent fire protection for some platforms. However, some of the most 

important platforms (and the types of fires most commonly experienced) remain. They are: 

• Crew compartments of ground vehicles (In the case of ground combat vehicles, the 

justification for the cost of automatic halon fire-extinguishing systems rests on the 

ability of these systems to extinguish the mist fireball explosion. This is a rapid 

growth fire caused by the release and ignition of large quantities of fuel or hydraulic 

fluid, mist, vapor, spray, etc. in an occupied compartment.), 

• Dry bays in aircraft (An in-flight fire in a dry bay typically occurs when a ballistic 

projectile impacts the dry bay, rupturing fuel system components and generating 

tremendous ignition energy.), 

• Engine nacelles in aircraft (Engine nacelle fire protection systems are designed to 

protect against fire events such as those caused by ruptured or leaking fuel, hydraulic 

fluid, or oil lines within the nacelle. In these circumstances, flammable fluid can leak 

onto the hot engine case or accessory components and ignite.), 

• Storage compartments in ships (Fires in shipboard flammable liquid storerooms 

(FLSRs) and paint issue rooms result from burning fuel cascading over highly 

obstructed and fuel loaded shelves and into flaming pools.), 

• Machinery spaces in ships (Fires in shipboard main machinery rooms (MMRs), 

auxiliary machinery rooms (AMRs), engine enclosures, and generator rooms result 

from the ignition of a pressurized fuel (diesel/hydraulic or lubricating oil) leak or 

ignition of fuel soaked insulating material. Leaks onto hot surfaces result in threedimensional spray fires with cascading liquid flow on complex surfaces and into 

flaming pools.), and 
4

• Fuel tanks in aircraft (Ullage, the void space above the fuel level in a fuel tank, in 

aircraft fuel tanks can have a potentially explosive fuel-air mixture. If initiated by a 

combat threat, an explosion can result.). 

 During the course of the NGP, a large number of experiments will be conducted and 

considerable effort will be devoted to computer modeling of the fire phenomena in order to 

ensure the applicability of the new fire suppression technologies. A small set of model fires has 

been constructed to enhance the effectiveness of these studies. These model fires capture the 

essence of the fires actually experienced by the weapons systems. The mist fireball explosion 

captures the essence of both the ground vehicle crew compartment and the dry bay fires. An 

appropriate laboratory apparatus for studying this model is an opposed flow diffusion flame 

(OFDF). This spray flame simulates fires that might occur in engine nacelles and dry bays. An 

appropriate laboratory apparatus for studying this model is the Dispersed Liquid Agent Fire 

Suppression Screen (DLAFSS). The obstructed pool fire simulates fires that might occur behind 

clutter in engine nacelles, storage compartments and shipboard machinery spaces. Appropriate 

laboratory apparatus for studying this model are the Transient Application, Recirculating Pool 

Fire apparatus (TARPF) and the cup burner. The inert atmosphere simulates conditions that are 

desirable in fuel tank ullage, where an ignition source should not generate a sustained ignition of 

a fuel/air mixture. An appropriate laboratory apparatus for studying this model is ASTM 

E 2079. 

 Characteristics and limitations of the systems that new fire suppression technologies will 

replace or into which they will be retrofitted were compiled. The descriptions of the 

environments of the current systems compiled during this program will serve as boundary 

conditions for the new technologies to be developed in subsequent Elements of the NGP. The 

system configuration (number of fire zones, extinguisher requirements, distribution system 

requirements, modification potential, etc.), system schematic, and the current halon 1301 system 

activation/sequence of events were examined. 

1.1 Task Objectives 

 The objectives of this project are: 

• To characterize and tabulate the nature, frequency, consequences (including 

personnel injuries), and severity of fires previously and currently attacked using halon 

1301. 

• To derive a small set of representative (model) fires (using the analyses described 

above) for other elements in the Program. 

• To compile characteristics and limitations of the systems that new fire suppression 

technologies will replace or into which they will be retrofitted. The descriptions of 

the environments of the current systems compiled during this program will serve as 

boundary conditions for the new technologies to be developed in subsequent 

Elements of the NGP. 
5

1.2 Technical Problems 

 There is a need to find replacement extinguishing agents to the currently used halons 

because production has been banned due to environmental concerns. However, to date such 

replacement chemicals have shown reduced performance relative to halons. Development of 

appropriate new technologies requires knowledge of the fires of concern and the characteristics 

and limitations of the systems they will replace or into which they will be fit. 

1.3 General Methodology 

 To accomplish the stated objectives, a methodology was developed which characterized 

the nature of fires attacked using halon 1301, derived a small set of model fires, and compiled 

the characteristics and limitations of the existing systems. 

 In order to characterize and tabulate the nature, frequency, consequences (including 

personnel injuries), and severity of fires previously and currently attacked using halon 1301, the 

Safety Centers of the Services and the Survivability/Vulnerability Information Analysis Center 

(SURVIAC) were contacted for both noncombat and combat data, respectively. Items such as 

fire zone, fire incidence rate, hazards to be protected against by halon 1301 system, flame 

suppression time requirements, and the current system tests were investigated. 

 A small set of model fires has been constructed to enhance the effectiveness of these 

studies. These model fires capture the essence of the fires actually experienced by the weapons 

systems. These were developed with the assistance of the basic research community and the test 

community. 

 Characteristics and limitations of the systems that new fire suppression technologies will 

replace or into which they will be retrofitted were compiled. These were developed using 

various resources: program offices, technical manuals, and previous studies. 

1.4 Technical Results 

 The descriptions of the environments of the current systems compiled during this 

program will serve as boundary conditions for the new technologies to be developed in 

subsequent Elements of the NGP. 

1.5 Important Findings and Conclusions 

 This effort resulted in numerous important findings and conclusions, which will be useful 

to future fire research. These included: generation of model fires to be used in computer 

modeling, types of fires encountered, hazards to be protected against by the halon 1301 system, 

methods used to certify current halon 1301 systems, characterization of the current system and 

the fire zone which it protects, and the modification potential for retrofit platforms. 
6

1.6 Significant Hardware Developments 

 None. 

1.7 Special Comments 

 None. 

1.8 Implications for Further Research 

 With limited resources in the future, considerable effort will be devoted to computer 

modeling of the fire phenomena. In order to ensure the applicability of the new fire suppression 

technologies, a small set of model fires was constructed to capture the essence of the fires 

actually experienced by the weapons systems. 

2.0 Bibliography 

 None. 

3.0 Detailed Description of the Project 

3.1 Introduction 

3.1.1 Goal of the Next Generation Fire Suppression Technology Program (NGP) 

 Unwanted fires are a principal cause of the loss of military ground vehicles, aircraft, and 

ships. Halon 1301, CF3Br, had become the fire suppressant of choice for nearly all of these 

platforms. Unfortunately, this chemical has been found to be a potent depleter of stratospheric 

ozone, and its production has ceased under both international treaty (the 1987 Montreal Protocol 

for Substances That Deplete the Ozone Layer and its subsequent amendments) and U.S. 

legislation (the Clean Air Act of 1990). 

 Prior Department of Defense research, development, testing and evaluation has identified 

alternative approaches for some of the applications of halon 1301. However, replacement 

technologies have been particularly difficult to find for some critical applications. The Next 

Generation Fire Suppression Technology Program (NGP) was initiated in 1997, with the goal to 

develop and demonstrate retrofitable, economically feasible, environmentally-acceptable, and 

user-safe processes, techniques, and fluids that meet the operational requirements currently 

satisfied by halon 1301 systems in aircraft, ships, land combat vehicles, and critical mission 

support facilities. The results will be specifically applicable to fielded weapon systems and will 

provide dual-use fire suppression technologies for preserving both life and operational assets. [1] 

3.1.2 Purposes of This Project 

 The purposes of this project are: 
7

• To characterize and tabulate the nature, frequency, consequences (including 

personnel injuries), and severity of fires previously and currently attacked using halon 

1301. 

• To derive a small set of representative (model) fires (using the analyses described 

above) for other elements in the Program. 

• To compile characteristics and limitations of the systems that new fire suppression 

technologies will replace or into which they will be retrofitted. The descriptions of 

the environments of the current systems compiled during this program will serve as 

boundary conditions for the new technologies to be developed in subsequent 

Elements of the NGP. 

3.1.3 Sources of Data on DoD Fire Experience 

 For details concerning the sources of data used for this effort, please address requests to: 

U.S. Army U.S. Air Force U.S. Navy 

U.S. Army Research 

Laboratory 

AMSRL-WM-TB 

Aberdeen Proving 

Ground, MD 21005 

46 OG/OGM/OL-AC 

2700 D Street Building 

1661 

Wright Patterson AFB, 

OH 45433-7605 

U.S. Naval Research Laboratory 

Code 6185 

Bldg. 207, Rm. 307 

4555 Overlook Avenue, S.W. 

Washington, DC 20375-5342 

U.S. Naval Air Systems 

Command 

Code 4.3.5.1 

Building 2187 

Patuxent River, MD 

3.1.4 Model Platforms 

 Previous research, development, testing and evaluation have led to the identification of 

ways to provide halon-equivalent fire protection for some platforms. The remaining applications 

are fire suppression in: 

• Crew compartments of ground vehicles, 

• Dry bays in aircraft, 

• Engine nacelles in aircraft, 

• Storage compartments in ships, and 

• Machinery spaces in ships. 

 In addition, halon 1301 is used to inert the ullage in some aircraft fuel tanks. 

 There are a large number of platforms that have halon 1301 fire-suppression systems. 

Obtaining information on all of these would be difficult, costly, and unnecessary. Therefore, the 

Military Services identified a small subset of these platforms whose halon systems are 

representative of the range of fire suppression needs: 

• Ground vehicles: M992 (FAASV), M1 tank, and M2/M3 (BFSV) 

• Aircraft: C-130, F/A-18 C/D, C-17, H-60, CH-47, F-16 

• Ships: DDG 51, LHD 1/LHA 1 
8

3.1.4.1 Ground Vehicles 

 Engine compartment fires in ground combat vehicles are being addressed by a separate 

Army program; hence, the NGP is only explicitly addressing crew compartments of ground 

combat vehicles now protected by halon 1301. However, new fire suppression technology 

developed under the NGP may well be applicable to such types of fires. 

 The single most lethal damage mechanism to ground vehicles in combat is fire. Fires can 

be initiated by a variety of weapons, and in all cases, they can cause a rapid kill of the vehicle 

and its crew. Internally stowed munitions such as gun rounds and missiles, fuel tanks, and 

hydraulic systems all provide substantial fire sources. Because fire can kill so quickly, rapidreacting fire suppression systems have been developed. 

 The particular requirements that exist for an agent in ground vehicles are that it suppress 

fires quickly in a highly cluttered volume and allow safe occupation of the space by personnel 

after discharge. The principal cause of incapacitation and death of combat vehicle occupants 

from peacetime fires is not burning but carbon monoxide (CO) poisoning. Since lethal CO 

concentrations can form quickly in the enclosed space of these vehicles, the fire must be 

suppressed within about 250 milliseconds (ms). The interior of a typical ground vehicle is filled 

with people, equipment, and structures that interfere with line of sight from the agent dispensers 

to some possible fire point sources. This means that the agent must be three-dimensional, that is, 

able to fill an irregular volume despite obstructions. The crew must remain in the vehicle after 

discharge, so the concentration of the fire suppression and its combustion byproducts must be 

lower than the concentrations acutely hazardous to humans. The replacement agent must meet 

all these requirements. [2] 

3.1.4.1.1 Field Artillery Ammunition Support Vehicle: M992 

(FAASV) 

 The FAASV is an aluminum, tracked resupply vehicle for the Palladin 155 mm selfpropelled Howitzer. The vehicle is powered by a conventional diesel engine. The crew 

compartment is a large aluminum box that contains ninety 155 mm Howitzer projectiles, the 

required propellant charges, and two Copperhead 155 mm warheads. There is a hydraulic 

system to aid in the movement and transfer of the ammunition into and out of the vehicle. The 

hydraulic fluid reservoir in the crew compartment contains approximately 50 liters (L) of 

hydraulic fluid. There are also several additional liters of fluid in the rest of the system. The 

composite (fiberglass) fuel cell is separated from the crew compartment by an aluminum 

bulkhead. Fuel may enter the crew compartment as a result of a projectile penetrating the 

bulkhead. The M992 FAASV has a halon 1301 extinguishing system for both the engine and 

crew compartments. 

3.1.4.1.2 Abrams M1 Main Battle Tank 

 The M1 tank is a steel, tracked battle tank. It is propelled by a turbine engine with 

multifuel capability. The tank has a four-man crew in a small, crowded compartment. The crew, 

except for the driver, is located in the turret that rotates with the main gun. The driver is in a 
9

small subcompartment in the hull of the vehicle. Movement between these two compartments is 

restricted to certain turret positions. The driver is located between two polyethylene fuel tanks in 

the front of the vehicle. A 1.3 cm (one-half inch) thick bulkhead separates the driver from the 

fuel tanks. There is an elaborate hydraulic system in the turret of the vehicle. The pumps and 

reservoirs are in the hull. The M1 tank has a halon 1301 extinguishing system for both the 

engine and crew compartments. 

3.1.4.1.3 Bradley Fighting Vehicle, M2 and M3 (BFVS) 

 The Bradley is an aluminum, tracked fighting vehicle powered by a conventional diesel 

engine. The crew compartment is an aluminum box designed to carry five soldiers when used in 

the scout mode or an infantry squad of soldiers when used in the armored personnel mode. The 

main fuel cell is on the floor in the crew compartment, directly under the turret basket. This 

molded nylon fuel cell is partially protected by an externally mounted steel plate, covering the 

bottom front half of the vehicle. A second, smaller nylon fuel cell is attached to the hull wall on 

the right-hand side, just below the turret ring. This second fuel cell is emptied first; therefore, 

the probability of its involvement in fuel fires would be lower than for the primary fuel cell. 

There is a small hydraulic system in the crew compartment. This system is used to lift and lower 

the rear exit ramp. This system is not considered to be a fire problem due to the small amount of 

hydraulic fluid involved and its placement in the vehicle. [3] The Bradley has a halon 1301 

extinguishing system for both the engine and crew compartments. 

3.1.4.2 Aircraft 

 There are three aspects of an aircraft that are vulnerable to fire and for which halon 1301 

systems are currently used: fire suppression in dry bays and engine nacelles and inerting against 

fire initiation in the ullage of fuel tanks. There is limited use of other halons (1011 – CH2BrCl 

and 1202 – CF2Br2) for total flooding. These are also ozone-depleting chemicals, and their 

replacement is included under the NGP umbrella. 

 Fire extinguishing systems are used on military and commercial aircraft to protect engine 

nacelles (the region surrounding the exterior of the jet engine case and shrouded by an outer 

cover, and typically ventilated) and dry bays (which can include wing leading/trailing edges, 

landing gear, avionics, and weapons bays). Halon-based inerting systems are also provided on 

some aircraft to provide inerting in fuel tank ullage. Auxiliary power units (APUs), which 

provide ground, supplementary or emergency power, are also frequently protected using 

extinguishing systems, either as stand-alone units or in conjunction with the engine nacelle fireextinguishing system. Each of these systems is fixed in configuration. Engine/APU 

extinguishing systems and inerting systems are typically activated remotely to totally flood the 

compartment in question with fire extinguishant, whereas dry bay fire extinguishing systems are 

activated automatically upon detection of a ballistically-induced fire/explosion event. 

 The Military Services have identified four fixed-wing and two rotary wing platforms for 

inclusion in this project. The fixed wing aircraft of interest for the NGP are the F/A-18, C-17, C130, and F-16. The rotary aircraft of interest for the NGP are the H-60 and CH-47 helicopters. 
10

3.1.4.2.1 C-130 

 The C-130 Hercules primarily performs in the intratheater portion of the airlift mission. 

The aircraft is capable of operating from rough dirt strips and is the prime transport for 

paradropping troops and equipment into hostile areas. [4] For fire protection, the C-130 utilizes 

three halons (1301, 1011, and 1202) onboard. The distribution system for the halon 1202 engine 

system is significantly different from the halon 1301 system. The high rate discharge (HRD) 

halon 1301 system utilizes open-end nozzles and relies on the high velocity of the agent 

discharge for proper dispersal within the nacelle. Consequently, high vapor pressure agents such 

as halon 1301 are best suited for HRD applications. In contrast, the conventional system utilizes 

perforated tubing for agent distribution with consequent penalties of restricted flow and general 

high total system weight. Low vapor pressure agents such as halon 1011 are best suited for the 

latter application. Halon 1202, an intermediate volatility extinguishant, has been used 

successfully in both types of systems. The C-130 has long and unique distribution system runs 

since the bottles are housed under the left wing and distribution lines must be routed from the 

bottles to the left engines on the left side wing, plus they must pass through the fuselage to the 

engines on the right wing. [5] 

3.1.4.2.2 F/A-18 

 The F/A-18 C/D is a single- and two-seat, twin-engine multimission tactical aircraft. It is 

the first tactical aircraft designed from its inception to carry out both air-to-air and air-to-ground 

missions. [6] A single-shot halon 1301 HRD-type fire extinguishing system on the aircraft 

provides fire protection for both engine nacelles, both airframe mounted accessory drive 

(AMAD) bays, and APU compartment. 

3.1.4.2.3 C-17 

 The C-17 Globemaster III is the newest, most flexible cargo aircraft to enter the airlift 

force. The C-17 is capable of rapid strategic delivery of troops and all types of cargo to main 

operating bases or directly to forward bases in the deployment area. The aircraft is also able to 

perform tactical airlift and airdrop missions when required. [4] The C-17 has a stand alone APU 

and has a large halon 1301 discharge system. It has larger engines than fighter aircraft. The fire 

suppression bottles are located on the wing and result in the bottles being exposed to vast 

temperature extremes. 

3.1.4.2.4 H-60 

 Over 1,500 Army BLACKHAWKs, made to fly soldiers into combat, now serve with 

active duty and National Guard units around the world. [7] The H-60 is a representative rotary 

aircraft widely used by all three Services. A dual-shot halon 1301 HRD-type fire extinguishing 

system on the aircraft provides fire protection for both engine nacelles and the APU 

compartment. The dual-shot functionality allows activation of both bottles on either engine 

nacelle and the APU compartment. 
11

3.1.4.2.5 CH-47 

 The primary mission of the Chinook is the transportation of troops, artillery, ammunition, 

fuel, water, perimeter protection/barrier materials, supplies and equipment to the battlefield. 

Other roles include medical evacuation, aircraft recovery, parachute drop, search and rescue 

missions, disaster relief, fire fighting and heavy construction. [6] A dual-shot halon 1301 HRDtype fire extinguishing system on the aircraft provides fire protection for both engine nacelles. 

Similar to the H-60, the dual-shot functionality allows activation of both bottles on either engine 

nacelle. 

3.1.4.2.6 F-16 

 The F-16 Fighting Falcon is a single-engine, compact, multirole fighter aircraft. It is 

highly maneuverable and has proven itself in air-to-air combat and air-to-surface attack. It 

provides a relatively low-cost, high-performance weapon system for the United States and allied 

nations. [4]. The F-16 is one of two aircraft that uses halon 1301 as fuel tank inertant. 

3.1.4.3 Watercraft 

 There are a number of types of watercraft using halon 1301, and the fire suppression 

system designs and use protocols can vary significantly from ship to ship within a given type. 

The Navy has selected two generic classes of ships for inclusion in this project, as they represent 

different continuing challenges for halon retrofit. 

3.1.4.3.1 DDG 51 (Arleigh Burke) Class: Aegis Guided Missile 

Destroyer 

 The DDG 51 is representative of the newer ships where halon 1301 was the suppression 

agent of choice during the design of the ship. The following compartments are protected by 

halon 1301: MMRs, AMRs, FLSRs, paint issue rooms, pump rooms, and generator room. There 

is enough space onboard to accommodate a two-shot halon 1301 system for each MMR, AMR 

and generator room. 

3.1.4.3.2 LHD 1 (WASP)/LHA 1 (Tarawa) Class: Amphibious 

Helo/Landing Craft Carriers 

 The LHDs can be separated into LHD-1 through LHD-4, and LHD-5. While LHD-5 

compartments are likely to have dampers in the ventilation ducts, the other ships probably do 

not. The following compartments are protected by halon 1301: MMRs, AMRs, FLSRs, paint 

issue rooms, pump rooms, and generator room. [8] 
12

3.2 Fire/Explosion Events Encountered on Current Weapons Platforms 

3.2.1 Ground Vehicle Crew Compartments 

3.2.1.1 Fire Zone Definition 

3.2.1.1.1 M992 FAASV Ammunition Resupply Vehicle 

 The principal combustibles in the M992 ground vehicle crew compartment are 

ammunition (ninety 155 mm Howitzer projectiles, and two Copperhead 155 mm warheads), 

hydraulic fluid (approximately 50 L (13.2 gal)), and personnel heater. Batteries are less of a 

threat, but cause a large portion of fires of fires in peacetime/training environments. Minor 

contributors to the fire threat include various filters (fuel, air, oil), rubber lines, insulation and 

seals. [2] 

3.2.1.1.2 M1 Tank 

 The principal combustibles in the M1 ground vehicle crew compartment are hull fuel 

(969 L (256 gallons)), hydraulic system (75.7 liters (20 gallons)), recoil mechanism (24.6 L 

(6.5 gal) hydraulic fluid), ammunition, and personnel heater. Batteries are less of a threat, but 

cause a large portion of fires in peacetime/training environments. Minor contributors to the fire 

threat include various filters (fuel, air, oil), rubber lines, insulation and seals. [2] 

3.2.1.1.3 M2, M3 Bradley Fighting Vehicles 

 The principal combustibles in the M2/M3 ground vehicle crew compartment are fuel 

(662 liters (175 gallons)), ramp hydraulics, batteries (4), turret batteries (2), ammunition, and 

personnel heater. Minor contributors to the fire threat include various filters (fuel, air, oil), 

rubber lines, insulation and seals. It is also possible that electrical fires could be initiated by 

electrical components (i.e., generator, etc.) shoring in the engine compartment. [2] 

3.2.1.2 Fire Incidence Rate 

3.2.1.2.1 Noncombat Fire Data 

3.2.1.2.1.1 Engine Compartment 

 Examination of fire data from the Army Safety Center shows that most of the accidental 

or peacetime fires experienced by ground vehicles have been in engine compartments. These 

fires are usually caused by ignition of fuel, oil or hydraulic fluid on a hot surface. There may be 

a leak or a pressurized spray of a flammable liquid near a hot exhaust manifold, engine 

combustor, etc. The AFES have not been very successful in extinguishing these fires. In most 

cases, the crew has used both the first and second engine compartment shots, and then whatever 

portable extinguishers were available. Then the local Fire Department was called to inject foam 

into the engine compartment. This has extinguished even the worst engine compartment fires. 
13

The Army has already developed low cost alternatives to halon 1301 systems for engine 

compartment fires. Thus they are not addressed by the NGP. 

3.2.1.2.1.2 Crew Compartment 

 In peacetime, the significant contributors to fire in the M992 FAASV crew compartment 

include ammunition stowed in the turret and hull, the fuel-fed personnel heater, fuel in the hull 

cells next to the driver, and the hydraulic fluid in the turret hydraulic system, in the main gun 

recoil mechanism, and in the ammunition handling system. Minor contributors to the fire threat 

include seat cushions, canvas equipment covers, personnel uniform items, vehicle logbooks and 

manuals, and electrical components which short out. [2] Since both personnel and ammunition 

in the crew compartment are exposed, fires must be extinguished immediately. 

 The M1/M1A1 crew compartment faces a fire threat from fuel or hydraulic lines which 

might fail or from electrical shorts which might occur in various components located in the turret 

and driver’s compartment. Additionally, the possibility exists that ammunition stowed in the 

M1/M1A1 could be ignited. [2] 

 An examination of data from peacetime fire incidents experienced by ground vehicles 

reveals several facets pertinent to this study. In Table 1, peacetime fire incident data for the 

M1/M1A1 tank for the years 1988, 1989, 1990 and the fires six months of 1991 have been 

summarized. These data show that the AFES system was only activated 71 percent of the time 

for M1/M1A1 fires and was adequate to extinguish the fire by itself only 34 percent of the time. 

Thirteen percent (13 percent) of the fires involved V-Packs which are part of the engine air 

cleaner system and, because they are fibrous material, are very difficult to extinguish. In fact, 

they often have to be fully immersed in water to be extinguished. Halon 1301 is generally 

ineffective against the V-Packs because they are smoldering type fires and it is difficult to apply 

Halon in the necessary concentrations for the required period of time. Fires which occurred in 

the battery compartment accounted for 15 percent of the total fires. Halon 1301 is also 

ineffective versus this type of fire. 

Table 1. M1/M1A1 Fire Incident Data. 

Year Total Cases Number 

Detected 

AFES 

Activated 

V-Pack 

Involved 

Batteries 

Involved 

AFES 

Effective 

1988 51 28 43 12 6 21 

1989 55 24 43 4 9 19 

1990 41 22 28 4 7 16 

1991* 21 9 12 4 5 5 

Total 178 83 126 24 27 61 

* First six months 

 The significant contributors to fire in the M2/M3 crew compartment include the fuel in 

the cell under the turret, hydraulic fluid in the ramp hydraulic system, batteries under the driver 

and under the turret, the fuel-fed personnel heater, and ammunition stowed in the turret and the 

hull. Minor contributors to the fire threat include seat cushions, canvas equipment covers, 

personnel uniform items, vehicle logbooks and manuals, and electrical components which might 

short out. [2] 
14

 A detailed breakdown of peacetime fire data for 74 additional incidents which occurred 

during the period 1988 to 1990 was also examined. These data, summarized in Table 2, covered 

various tanks (no M1/M1A1), infantry vehicles, and self propelled artillery vehicles. The data 

included the location of these fires (engine compartment, crew compartment, and other) and type 

of fire (diesel fuel, hydraulic oil, transmission oil, electrical, engine oil and other). A breakdown 

of this type of data for the M1/M1A1 tank only exists for these first six months of 1991; 

therefore, it was not included. 

Table 2. Detailed Breakdown of Ground Vehicle Fire Incidents, 1988-1990. 

 Tanks Infantry Vehicles SP 

Arty 

Total 

Type Engine Crew Other Engine Crew Other Engine Engine Crew Other 

Fuel 16 1 2 2 3 1 19 2 4 

Engine 5 5 

Hyd Oil 1 1 

Trans Oil 2 2 

Electrical 10 3 2 3 10 3 5 

Other 12 4 3 1 1 2 13 5 5 

Total 44 7 6 5 3 8 1 50 10 14 

 These data provide several interesting insights into peacetime fires in ground vehicles. 

First, they show that regardless of vehicle type, engine compartments were the most common 

location for fires (68 percent). Of the engine compartment fires at least 27 out of 50 (54 percent) 

were hydrocarbon fires (Class B) and ten (20 percent) were electrical fires (Class C). The 

remaining 26 percent of the fires were of an undetermined type. Further, at least 45 percent of 

all fires were hydrocarbon fires (Class B) and 25 percent of all fires were electrical in nature. 

 The fire incident data led to several conclusions about peacetime fires in ground vehicles. 

First, engine compartment fires clearly offer the largest peacetime threat. It therefore seems 

appropriate that the engine compartment is receiving the highest priority for replacement of 

halon 1301. Next, most fires are of the hydrocarbon type, so the replacement agent which is 

selected should be very effective against Class B fires. There is a problem with smoldering 

Class A type fires (V-Packs), and therefore a coating agent should be considered. Finally, a 

significant percentage of fires are electrical. This means that an ideal would be one which can 

suppress and/or extinguish Class C fires. 

3.2.1.2.2 Combat Fire Data 

 Fires can be started due to weapon attack on a fuel cell, hydraulic fluid reservoir, or 

pressurized hydraulic lines. The types of fires may be pool fires or spray fires. 

3.2.1.2.2.1 Engine Compartment 

 In combat, the most significant cause of fire is from ballistic impacts against fuel 

components. Fires in this case are characterized by fuel being released into the engine from 

damaged fuel cells, fuel lines, fuel pumps and similar components. A fire may be ignited by hot 
15

fragments and incendiary from the threat or by fuel which contacts hot engine surfaces. In either 

case, the optimum fire extinguishing agent should be able to not only suppress the immediate fire 

but also prevent reignition either by cooling of hot surfaces or by placing a barrier of agent 

between the hot surfaces and the fuel. 

3.2.1.2.2.2 Crew Compartment 

 There are no data available describing a combat-induced mist fireball explosion in a crew 

compartment and the role of halon 1301 in attempting to extinguish the fire. The reports which 

describe the testing of the halon 1301 system against mist fireball explosions in crew 

compartments are classified or of limited distribution. However, models have been fabricated 

which describe the essential physio-chemical features which have been elucidated by crew 

compartment fire tests. 

 Since the fuel main tank is positioned so low in the hull on the M2, M3 Bradley Fighting 

Vehicles, it would probably not be struck by flat trajectory rounds. The most likely attack modes 

are mines and air-attack weapons. The external steel plate under the front half of the hull will 

provide only limited protection against large antivehicle mines. Many air-attack weapons are 

capable of defeating the armor of aluminum vehicles. [2] 

 The most significant threat to the crew compartment during combat is from ammunition 

fires caused by ballistic impacts. No currently available replacement agent will be capable off 

rapidly suppressing such a fire. In recognition of this problem, the M1/M1A1 tank ammo is all 

stowed in special compartments behind blast doors designed to contain any ammunition fires and 

prevent their spread to the crew or engine compartments. The remaining possibilities of fire in 

combat derive from ballistic impacts to the fuel and hydraulic components where the fluids may 

be released in a spray of droplets and are ignited by hot fragments or incendiary. 

 Data on fires that occurred as a result of combat incidents are not releasable. It is 

expected that such data would show a larger percentage of fires to have occurred in the crew 

compartments due to ballistic impacts on hydraulic components, fuel system components and 

ammunition. As a percentage of all fires, electrical fires could be expected to increase somewhat 

because of shorts occurring in severed wiring. Smoldering Class A fires would be a problem not 

only in V-Packs but also in items such as seat cushions and crew personnel equipment (i.e., 

packs, sleeping backs, etc.). [2] 

3.2.1.3 Hazards to be Protected against by Halon 1301 Systems 

 The available data show that ground vehicles experience a wide variety of fires. These 

include: 

• Class A fires involving air filters, canvas, paper, 

• Class B hydrocarbon fuel fires fed by vehicle fuel, hydraulic fluid, lubricants, and 

miscellaneous materials such as paint, 

• Class C electrical fires including batteries, and 

• Class D ammunition fires. 
16

 Also, the nature of these fires in peacetime is somewhat different from that experienced 

in combat. It may be difficult to find a single agent which can handle all of these fires under all 

conditions; the best solution may be a combination of agents or protection concepts. For 

example, one method might be best for the fully developed Class A/B fires in the engine 

compartment, a second for electrical fires, a third for smoldering Class A fires, and a fourth for 

crew area protection involving fires initiated by ballistic impacts. [2] 

 The most common types of fires to occur in combat vehicles are the mist fireball 

explosion, pressurized hydraulic spray fires, and dry bay fires. 

Mist Fireball Explosion

 The mist fireball explosion occurs when a weapon perforates the armor (outer skin) of a 

vehicle and then passes through a fuel cell or hydraulic reservoir which is in an occupied 

compartment. As the penetrator traverses through the fuel cell, energy is transferred to the 

liquid. A pressure wave is formed at the tip of the penetrator, and a cavity is formed at the tail of 

the penetrator as it moves through the liquid. When the cavity collapses, a pressure wave is 

formed in the wake of the penetrator. 

 In the case of a kinetic energy penetrator (a bullet or metallic fragment), the pressure in 

the liquid due to the cavity collapse can exceed the pressure at the front of the penetrator. Thus, 

when a liquid filled metallic container (fuel cell) is perforated by a bullet or fragment, the 

container usually bulges outward at both the entrance and exit holes. 

 In the case of a shaped charge jet traversing a fuel cell, the pressure from the high-speed 

jet on the material at the entrance hole of the container is larger than the pressure due to cavity 

collapse. The container bulges outward only at the jet exit hole. The container usually bulges 

inward at the jet entrance hole. 

 The pressure waves (and the interaction of their reflections off the container walls) cause 

fuel to spurt out both the entrance and exit holes of the fuel cell. The fuel (or hydraulic fluid) 

exits as a mist consisting of vapor, droplets, and streams of liquid. The mist continues to spurt 

fuel from the holes as long as the pressure waves are present throughout the liquid. 

 In many cases the seams of the fuel cell may be split allowing a pool of fuel to form 

while the mist is present in the compartment. The pool of fuel is important for the formation of a 

sustained fire in the vehicle. 

 The ignition source required for igniting the fuel mist will normally not be provided by a 

shaped charge jet or bullet. The shaped charge jet is moving so fast that there is insufficient 

contact time between the jet and the fuel air mixture for ignition to occur. A bullet is normally 

not hot enough to serve as an ignition source. A tracer, a pyrophoric, or incendiary component 

of a kinetic energy penetrator may ignite the mist if the component remains in the vicinity of the 

fuel-air mixture. The spall ejected from metal which has been struck by the penetrator is the 

usual ignition source. 
17

 The fuel mist which comes out of the container is in the (approximate) form of an 

expanding cone. In general, it travels in the path of the penetrator. Thus, a fuel cloud follows 

the penetrator. When the penetrator strikes an object, perhaps the far wall of the vehicle, the 

penetrator, in perforating the wall, will eject hot spall from the wall material. This spall will 

move back into the interior of the vehicle along the approximate path of the penetrator. When 

the fuel mist and the hot spall collide, the mist fireball explosion occurs. A large portion of the 

volume of the compartment may be involved in the fireball. The pressure associated with the 

fuel explosion is enough to force open hatches of a combat vehicle. 

 The initial fireball may be sufficient to transfer ignition to the pool of fuel that can form 

if the seams of the container split or if the entrance and exit holes in the container are large 

enough. Combustion of the pool of fuel will cause a sustained fire in the vehicle. This normally 

leads to the loss of the vehicle. The conditions which lead to the mist fireball explosion can 

occur at both the entrance hole of the liquid container and the exit hole. 

 In general, large (overmatching) weapons, thin-walled liquid containers, high liquid 

temperatures and metallic surfaces in the compartment favor the mist fireball explosion. Easily 

ruptured containers and warm surfaces in the compartment favor formation of a sustained fire. 

 The Army has determined that if the mist fireball explosion can be suppressed within 

250 ms from the time the weapon strikes the vehicle, there will not only be no sustained fire, but 

personnel present in the compartment will receive no worse than first degree burns (comparable 

to a mild sunburn) on exposed skin. Therefore, the requirement is that the mist fireball explosion 

be extinguished within 250 ms. Current halon 1301 automatic fire extinguishing systems can 

meet this requirement, often exceeding it by 100 ms. 

Pressurized Hydraulic Spray Fires

 The pressurized hydraulic spray fire occurs when a pressurized hydraulic fluid line is 

ruptured by a weapon attack or simply fails due to negligence or fatigue. The high pressure (up 

to 27.6 MPa (4,000 pounds per square inch (psi))) spray is readily combustible even at 

temperatures well below the flash point of the fluid. Since low viscosity is a requirement of a 

good hydraulic fluid and since low viscosity fluids readily produce fine sprays, all flammable 

hydraulic fluids can readily generate a blow-torch-like flame when ignited. 

 The supply of hydraulic fluid in an aircraft or ground vehicle will normally be many 

gallons. The burning spray will continue as long as the pumps can maintain pressure, or until the 

reservoir is depleted of fluid unless pressure fuses are present in the system. This entails great 

danger to personnel if the spray is in an occupied compartment. Even in an unoccupied 

compartment, the fire can cause severe damage. Both aircraft and ground vehicles are at risk. 

 There are no data on the maximum time personnel may be exposed to sprays of burning 

hydraulic fluid, but it assumed that these fires must be extinguished within the 250 ms 

requirement for the mist fireball explosion fires. 
18

 Pressurized fuel systems normally have pressures much lower than those employed in 

hydraulic systems. While a combustible spray will be formed if a pressurized line is ruptured, 

the rate of flow of the fuel should be much less than that of hydraulic fluid. Therefore, while 

there is a severe fire problem with the leak, if ignited, the problem should be less severe than 

with hydraulic fluid. Therefore, the 250 ms extinguishment time is presumed sufficient for fires 

involving leaks of pressurized fuel in occupied compartments. 

Dry Bay Fires

 Dry bays are found on both aircraft and ground vehicles. This is a compartment that does 

not have any flammable material stored in it. However, a flammable material such as a fuel cell 

or hydraulic fluid is adjacent to the dry bay separated by only a bulkhead. The dry bay fire is 

similar to the mist fireball explosion even though it occurs in a compartment which does not 

contain a fuel cell or hydraulic fluid. A shaped charge jet, bullet, or fragment which attacks the 

fuel cell or hydraulic fluid system can also perforate the bulkhead, allowing combustible fluid to 

enter the dry bay. The liquid will be in the form of a mist. This mist can be ignited by hot spall, 

pyrophoric, incendiary or tracer components of the projectile. This scenario also occurs when 

the attacking weapon enters the dry bay first and then perforates the bulkhead and the fuel cell. 

An overpressure is created in the fuel cell and fuel is spurted into the dry bay through the 

entrance hole. 

 The explosion of the mist can create pressures high enough to cause major structural 

damage to lightweight structures such as aircraft. There is a high probability of a sustained fire 

due to the flow of combustible liquid into the dry bay. This flow can be through the hole in the 

bulkhead caused by the penetrator, or the flow may be through a bulkhead ruptured by the 

pressure of the mist explosion. The sustained fire, with or without structural damage, can result 

in loss of an aircraft or ground vehicle. 

 In the case of an occupied dry bay, it is necessary to extinguish the fire within 250 ms, for 

the safety of personnel. However, this time may be too long in the case of aircraft. Damage to 

the structure may occur even if the fire is extinguished within 250 ms. 

3.2.1.3.1 M992 FAASV Ammunition Resupply Vehicle 

 The fuels used in the M992 (FAASV) are JP-8, diesel, and Jet A1. Under operating 

conditions, fuel temperature can reach 70 oC (158 °F). A typical flash point for JP-8 and Jet A1 

is approximately 50 oC (122 °F), but can be as low as 38 oC (100 °F). For diesel fuel, a typical 

flash point is approximately 65 oC (149 °F), but can be as low as 53 oC (127 °F). Conventional 

hydraulic fluid is used in this vehicle. The flash point is 93 oC (199 °F) or higher. The expected 

working temperature of this fluid is approximately 77 oC (171 °F). Sprays of this material are 

extremely flammable even at temperatures below the flash point. 

3.2.1.3.2 M1 Tank 

 The fuels used in the M1 tank are JP-8, diesel, and Jet A-1. Under operating conditions, 

fuel stored in the front of the vehicle is at ambient temperature which can be as high as 63 oC 
19

(145 °F). A typical flash point for JP-8 and Jet A1 is approximately 50 oC (122 °F), but can be 

as low as 38 oC (100 °F). For diesel fuel a typical flash point is approximately 65 oC (149 °F), 

but can be as low as 53 oC (127 °F). The hydraulic fluid used in this vehicle is “fire resistant”, 

its flash point being approximately 215 oC (420 °F). The expected working temperature of this 

fluid is approximately 77 oC (171 °F). Sprays of this material are extremely flammable even at 

temperatures well below the flash point. 

3.2.1.3.3 M2, M3 Bradley Fighting Vehicles 

 Fuels used in the Bradley fighting vehicles are JP-8, diesel, and Jet A-1. Under operating 

conditions, the fuel in the smaller tank is used before the fuel in the larger tank. The halon 

systems are not capable of extinguishing fires of the ammunition stored on the vehicle. 

Therefore, only hydrocarbon fires are addressed by the halon system. Therefore, the fuel fires in 

the crew compartment would probably involve the main tank. 

3.2.1.4 Flame Suppression Time Requirements 

 As noted above, full fire suppression within 250 ms is required for crew compartment of 

fire to other combustibles, such as ammunition, and to prevent second-degree burns on exposed 

skin of the crew. A knockdown of the fire is not acceptable since manual follow-up would take 

too long. 

 For the FAASV and the M1, reflash is not considered to be a problem because there are 

no hot surfaces in the crew working area, and the halon is retained for eight seconds until the 

exhaust fan automatically engages. By this time the hot spall will have cooled sufficiently to 

provide only a poor ignition source. The main gun ammunition with combustible cartridge cases 

is stored in a separate compartment, sealed from the crew compartment of the tank. A fire of 

short duration in the crew compartment is not considered to be a likely ignition source for the 

ammunition. However for the M2/M3, reflash is considered to be a problem in the case of attack 

by a land mine. In all probability there will be an external fuel fire under the vehicle and unless 

the vehicle can drive away or be removed from the fire, the fire will likely enter it. Therefore, 

the fire extinguishing system must inert the crew compartment until the vehicle can be moved 

away from the fire. [3] 

3.2.1.5 Current System Tests 

 The crew compartment fire suppression test fixture was built from a combat vehicle hull 

and turret to evaluate the performance of high speed automatic fire extinguishing systems (FES) 

for occupied areas. It is equipped with instrumentation to determine suppression speed and the 

ability of the FES to protect the crew from burns, blast pressure and toxic chemical injuries. 

 A range of ballistic threats can be used to simulate battle damage. Armor protection and 

other material, such as fuel tanks or hydraulic reservoirs, are positioned in the path of the 

penetrator for testing. Combustible fluids can be pressurized and heated to any desired condition. 

A remote controlled pressurizing blower is provided for ventilation and NBC overpressure 
20

system simulation. To reduce test setup and post-test repair time, the fixture is fitted with 

replaceable components including armor windows, hydraulic reservoirs and fuel tanks. 

 FES performance and crew survivability is assessed by a comprehensive instrumentation 

suite which includes high speed video/film, transient pressure, temperature and toxic combustion 

products measuring devices inside the normally occupied spaces. 

http://www.atc.army.mil/brochures/fireprot/images/imagename.jpgViewing ports have 

been cut into the sides of the test bed through which video and high-speed cameras view and 

record the events. Fine-wire thermocouples and heat flux gages are suspended inside the crew 

compartment to measure time versus temperature and time versus energy transients. Infrared 

sensors have been installed to monitor and record fire intensity levels, and may be used to 

discharge extinguishing agents upon reaching a pre-determined intensity level. Piezo-electric 

pressure gages are used to measure crew area air pressure during the events. 

 Toxic fumes instrumentation is under development to measure oxygen depletion and 

toxic fumes by-products resulting from the decomposition of fluorinated extinguishing agents 

and the combustion of hydrocarbon fuels. 

 Extinguisher locations and distribution system designs can be easily changed as required 

to improve performance. Simulated "clutter" (equipment, ammunition containers, dummies, etc.) 

can be positioned as desired to increase realism. Test scenarios can be defined and extinguishers 

may be activated by fire sensors or at a pre-selected time after initiation of the threat. Multi-shot 

systems can also be evaluated. 

 A backup CO2 extinguishing system is provided for asset protection, in the event that the 

test system fails to extinguish a test fire. 

 The standardized fuel cell for the testing has been determined to be a 2.5 ft3, reinforced 

aluminum fuel tank are fabricated from 0.32 cm (1/8 in.) thick aluminum sheets. The fuel tank is 

placed on the rear, right sponson of the crew compartment, as close to the right side wall of the 

vehicle as possible. Ten gallons (37.9 L) of JP-8 fuel, heated to approximately 76.7 °C (170 °F), 

is poured into the tank. A replaceable aluminum armor window has been bolted onto the side of 

the test bed vehicle adjacent to the fuel cell. A shape-charge munition is placed outside the 

removable window, pointed in the direction of the fuel cell and center of the crew compartment. 

Initiation of the warhead allows the shape-charge jet to penetrate the wall and fuel cell, initiating 

the fuel-mist fire inside the crew compartment. Extinguishing agent is discharged based on a predetermined time delay following initiation of the warhead. 

 Fire suppression testing with shape-charge munitions is ultimately the final test of 

whether or not an extinguishing system is effective in combating explosively-formed fuel-mist 

(EFFM) fires. 

 Unfortunately, tests conducted with shape-charge munitions are expensive, time 

consuming and destructive. Aberdeen Test Center (ATC) personnel have developed a ballistic 

fireball simulator (BFSim) to be used to test candidate fire suppression systems and agents by 
21

expediting hardware evaluation and reducing test time and costs when compared to actual 

ballistic tests. 

http://www.atc.army.mil/brochures/fireprot/images/imagename.jpgThe BFSim uses highpressure nitrogen gas (up to 8.27 MPa (1200 psi)) to rapidly force hot JP-8 (82.2 °C (180 °F 

plus)) through a small diameter, multi-orifice spray nozzle into the crew area of the test bed 

vehicle. The fuel is sprayed into the test bed compartment then ignited with a high energy spark 

device. The spray is initiated and ignited at the desired location (generally either the entry point 

or the opposite wall) after a pre-determined delay. The time delay between spray start and 

ignition can be varied, along with the configuration of the nozzle and spray pressure. As the 

fireball expands, an IR detector senses the fire, and discharges the fire extinguishing system at a 

pre-set intensity. The fuel spray is stopped at a pre-set time. The simulator decreases test turn 

around time by eliminating damage from explosive charge, while providing a credible challenge 

to automatic fire extinguishing systems. The BFSim crew test bed is outfitted with the same 

instrumentation as for the ballistic test. 

 When promising results are obtained for the BFSim tests, final testing is conducted 

against an actual ballistic threat. [9] 

 General purpose outdoor test ranges designed for very large scale fire, vulnerability, 

survivability, explosive and lethality tests. The real estate area covers 132 Acres (535,000 m2

). 

Current crew compartment tests are performed at the Poverty Island Outdoor Range Complex. 

The structure consists of outdoor test pads with hardened instrumentation enclosures and means 

for liquid test effluent collection. There are no size and weight limitations. Fire and explosion 

limitations are dependent to atmospheric weather conditions. Several thousands of pounds of 

explosive and several hundreds of gallons of fuels can be addressed. [10] 

 The crew compartments of the M992, M1, and the M2/M3 range in volume from 7.1 to 

19.8 m3 (250 to 700 ft3) and employ from 7 lb of halon 1301 in a single shot to 21 lb in each of 

two shots. 

 The Army Surgeon General has established the guidelines shown in Table 3 as the 

minimum acceptable requirements of automatic fire extinguishing systems for occupied vehicle 

compartments. These parameters have been established at levels that would not result in 

incapacitation of the crew from the fire and its extinguishment, allowing them to take corrective 

action and potentially to continue their mission. 

Table 3. Crew Survivability Criteria. 

Parameter Requirement 

Fire Suppression Extinguish all flames without reflash 

Skin Burns Less than second degree burns (<1316 °C-s (2400 °F-s) over 10 heat flux <16.3 J/cm2

(3.9 cal/cm2

) 

Overpressure Less than 80 kPa (11.6 psi) 

Agent Concentration Not to exceed LOAEL (Lowest Observed Adverse Effects Level) 

Acid Gasses Less than 1000 ppm peak 

Oxygen Levels Not below 16 percent 
22

 The crew test fixture was constructed from an excess ground vehicle hull and turret. The 

fixture had an interior volume of approximately 12.7 m3

 (450 ft3). Three “tin” mannequins and a 

four-unit TOW missile rack were added to simulate partial vehicle stowage. The cargo and turret 

hatches and ramp door were secured during each test while the driver’s hatch was allowed to pop 

open to relieve internal overpressures while minimizing airflow. 

 Instrumentation included high-speed and standard video, 1-micron infrared detectors, 

heat flux gages, thermocouples, and pressure gages. Four types of instrumentation measured 

acid gas exposure levels: ion selective electrodes (grab bag sampling), sorbent tubes, midget 

impingers, and FT-IR analyzers. The FT-IR was the only one of those methods that reported 

levels of the gases themselves, as opposed to fluorine or bromine ions. Gas species tested for 

included oxygen (as O2), hydrogen fluoride (HF), hydrogen bromide (HBr), and carbonyl 

fluoride (COF2), nitrogen oxide (NO), nitrogen dioxide (NO2), carbon oxide (CO), and carbon 

dioxide (CO2) levels were also monitored during certain gas generator tests. 

 Two test scenarios conducted include fuel spray fires and ballistic penetrations. The 

spray fire was generated with approximately 1.1 L (0.3 gal) of JP-8 of JP-8 heated to 82.2 to 

87.8 °C (180 to 190 °F) and pressurized to 8.27 MPa (1200 psi) using a specially designed 

nozzle. Fuel flow continued for approximately 1.2 s with the igniter energized for the duration 

of the spray to simulate the reignition sources present during the ballistic event. The spray fires 

were monitored with three one-micron infrared detectors. The extinguishing system was 

activated automatically after an 11 s delay from the time the fire energy reached a predetermined 

threshold. Ballistic fires were generated by firing a 6.9 cm (2.7 in.) shaped charge through an 

70.8 liters (18.7 gallon (2.25 ft3

)) capacity aluminum fuel cell filled with 41.6 L (11 gal) of JP-8 

heated to 73.9 °C (165 °F). The fire extinguishing system was activated 25 ms after warhead 

initiation to eliminate the variability of the detection system. [11] 

3.2.2 Aircraft Dry Bays 

 The use of dry bay fire protection systems on selected aircraft is warranted due to the 

combat threat environment and the mission profile of the aircraft. These systems have been 

verified recently by live fire testing using ballistic threats to assure performance in the actual fire 

extinguishing of such events. Generally, rotary-wing dry bays are much smaller than fixed-wing 

dry bays with the exception of the CH-47. 

3.2.2.1 Fire Zone Definition 

 Dry bays are defined as void volumes within the mold line of the aircraft, excluding air 

inlets, engine compartments, and exhaust nozzles. Dry bays can include wing leading/trailing 

edges, landing gear wheel wells, avionics equipment and weapons bays, and related zones where 

a catastrophic rupture of flammable fluid and an ignition supply, such as from a ballistic impact, 

can create a sustained fire. Dry bays frequently contain fluid lines (fuel, hydraulic, coolant), 

bleed air ducts, and electrical cables and may contain avionics, flight control actuators, hydraulic 

accumulators and liquid oxygen dewars. [12] 
23

 The four common types of dry bays and their physical characteristics are categorized in 

Table 4 and Table 5. Two of the four bay types are located in the wing. Wing leading 

edge/trailing edge (forward and aft portion of the wing) bays are characteristic of both 

fighter/attack and transport aircraft, while midchord (compartment between fuel cells in wing) 

bays are found primarily in transport aircraft. The two types of fuselage bays, fuel cell boundary 

bays and equipment bays, are characteristic of fighter/attack aircraft. Equipment bays can be 

subdivided into forward equipment bays, aft equipment bays, ammunition storage bays and 

engine accessory bays. 

Table 4. Categorization of Wing Dry Bays. 

Types Leading Edge/Trailing Edge Midchord 

long, narrow rectangular, nearly cubic 

relatively uncluttered with sections 

isolated by ribs 

relatively uncluttered, open volume 

contain hydraulic lines, control 

cables and wire bundles, and bleed 

air ducting 

contain fuel lines, fuel system 

components 

 located between fuel tanks or with 

one side wall common to fuel tank 

Characteristics 

common to both fighter/attack and 

transport aircraft 

found primarily in transport aircraft 

Table 5. Categorization of Fuselage Dry Bays. 

Types Fuel Cell Boundary Equipment 

shallow bays separated at close 

intervals by rigs and stringers 

size and shape varies with contents 

and location; usually large; 

sometimes partitioned with bulk 

heads, ribs, and stringers 

vary from empty to almost full medium to dense clutter 

contain lines, wiring and control 

cables 

usually ventilated 

located below or beside fuel tank subtypes: 

• forward equipment bay 

located between cockpit 

and forward fuel tank 

• ammunition storage bay 

usually located between 

fuel tanks 

• engine accessory bay 

located below and beside 

engines and aft fuel tank 

• aft equipment bay located 

between engines 

Characteristics 

common to fighter/attack aircraft common to fighter/attack aircraft 
24

3.2.2.2 Fire Incidence Rate 

3.2.2.2.1 Noncombat Fire Data 

 Noncombat fire data were examined to identify fires that resulted from failure of or 

damage to dry bay equipment. These data were divided into six typical dry bay configurations: 

fuselage, engine pylon (mainly on transport aircraft; suspends the engine from wing; contains 

fuel lines going to the engine), wing leading edge (forward portion of the wing), wing root (point 

of attachment of wing to the fuselage), tail (contains hydraulic lines for actuators) and wheel well 

(contains tires, hydraulic lines, etc.). The majority of mishaps occur due to an equipment failure 

in a fuselage dry bay or failure of the engine or starter that results in damage to a fuselage dry 

bay. Of the remaining mishaps, a large number involved wing fire damage due to equipment 

failures. [13] These may include overheating, shorting electrical circuits in avionics bays, some 

other form of impact (i.e., bird strike), or burning stored munition propellants can also be 

responsible in rare instances [12]. 

3.2.2.2.2 Combat Fire Data 

 Combat fires are usually created when a ballistic projectile impacts a dry bay in flight, 

rupturing fuel system components and generating tremendous ignition energy. [12] 

 Figure 1 illustrates the sequence of events by which a dry bay fire can be ignited from the 

impact of an armor piercing incendiary (API) or high explosive incendiary (HEI) projectile into a 

wing leading edge. 

 During a projectile or fragment entry into an aircraft, the skin surface is usually torn and 

radial cracks may form. This effect is referred to as skin petaling. The damaged skin surface can 

protrude into the aircraft (entrance damage), or into the surrounding airflow (exit damage), 

creating a flame-holding region for any fires that develop. Projectile penetration into an aircraft 

can also result in pieces of the skin surface material, referred to as spall, being ejected at high 

speeds along the path of the projectile. Spall can also become penetrators and may introduce 

additional fluid into the dry bay. 

 If the proper skin thickness and impact obliquity angles are present, impact of the HEI 

projectile with the target skin will initiate the projectile’s fusing sequence, which in turn will 

detonate the projectile’s high explosive. An approximate 425 μs delay will occur after impact 

before the selected projectile detonates. This delay allows the projectile to travel farther into the 

target before it explodes, thereby increasing its damage capability. The detonation breaks the 

projectile shell apart and expels a large number of small fragments capable of penetrating electric 

wire bundles and perforating fuel tanks, hydraulic lines and coolant lines. The fragments 

penetrate into adjacent fuel tanks and hydraulic and coolant lines, thereby releasing combustible 

fluids into the dry bay. These fluids can be ignited by either the incendiary (ignited aluminum 

particles) of the projectile or sparking due to fragment impacts on metallic surfaces. They also 

may perforate the aircraft skin(s) allowing airflow (containing oxygen) to enter into the dry bay. 

Overpressures created from the detonation of the projectile can significantly damage adjacent 

fuel tanks, crush and/or sever hydraulic and coolant lines, as well as remove aircraft skin. 
25

Figure 1. Projectile Penetration of a Wing Leading Edge

 Warhead fragments damage aircraft components primarily through penetration and 

perforation effects in the same manner as small armor piercing projectiles. Depending upon the 

material impacted, a fragment typically generates incandescent particles or vapors, known as 

impact flash or vaporific flash, which can ignite nearby combustible fluids. The intensity of the 

flash is dependent on the material type and thickness of the impact panel and the mass, material 

type, and striking velocity of the warhead fragment. An impact velocity of greater than 1220 m/s 

(4,000 ft/s) is typically required before vaporific flash is experienced. A fragment impacting the 

skin at sufficiently high speed can also result in breakup of the fragment into a number of smaller 

fragments which individually are inherently less lethal than the original fragment. However, light 

aircraft components (i.e., hydraulic lines) may be vulnerable to these smaller fragments. In 

either case, a single fragment, or a number of smaller fragments, could penetrate the tank wall 

and release a spray of fuel into the dry bay. Interaction of the vaporific flash, fuel spray, and 

available oxygen can result in a dry bay fire. [14] 
26

 Data from Southeast Asia (SEA) suggest that 58 percent of the 24 C-130 incidents were 

related to dry bay fires. The C-130 incidents were reported in which engines and/or adjacent 

bays were damaged by gunfire, creating numerous ignition sources, leaking fuel, and resultant 

fires in the leading and trailing edges. [13] 

 Since the C-17, F-16, H-60, and F-18 platforms were not in service during SEA, no SEA 

combat data exist. 

 No discernable dry bay fire incidences in the SEA data for the CH-47 platform were 

located. 

3.2.2.3 Hazards to be Protected Against by Halon 1301 Systems 

 The principal modes of failure of the fuel system are fire and explosion. The most 

critical hydraulic system failures were those in which damage to lines or pumps resulted in fires. 

Fuel system related losses were classified as direct fires and explosions, vapor mist explosions in 

the ullage, liquid fed fires in the dry bays, indirect fires caused by leakage from damaged lines, 

or from fuel tanks damaged by hydrodynamic ram effects. Protection of dry bays is equal in 

importance in vulnerability reduction to direct protection of the fuel system from fire and 

explosion. 

3.2.2.4 Flame Suppression Time Requirements 

 Fluid ignition requires the interaction of an ignition source, a flammable fluid, and 

oxygen. However, fluid ignition is a time-based event, and each ingredient must be introduced 

in the proper sequence and with the proper quantity for a sufficient duration to assure ignition 

occurs. If the proper conditions are present, three to five ms are required to initiate a dry bay 

fire. [14] 

 Given an ignition source in a flammable mixture, the flame front starts at the source and 

propagates throughout the mixture until it reaches either a solid boundary or a mixture that will 

not support combustion. The velocity at which the flame front travels depends upon the amount 

and rate of energy released. A relatively large and rapid energy release by the combustion 

process causes a supersonic wave or flame front with a rapid rise and large increase in the 

pressure, called the overpressure. This phenomenon is referred to as a detonation. A relatively 

small and slow energy release causes a subsonic flame front with a slow rise and low increase in 

the overpressure. This is called a deflagration. Aviation fuels typically deflagrate with 

overpressure normal less than 1.38 MPa (200 psi). Detonations and deflagrations may or may 

not lead to a fire. When the combustion overpressure is sufficiently large enough to damage or 

destroy portions of the aircraft structure, the combustion process is referred to as an explosion. 

[15] Dry bay fires are typically the result of a deflagration. Because of this, successful fire 

suppression efforts should be accomplished within approximately 200 ms. 

 Live fire test data typically show dry bay fires to be quenched within 200 ms. Fast 

quenching is preferred due to the effect of agent dilution by the entering airflow induced by the 

battle damage. However, there is no set specification for fire suppression time. [16] 
27

Recommendations for these requirements were developed in the Aircraft Engine Nacelle/APU 

and Dry Bay Fire Extinguishing System Design Model. 

3.2.2.5 Current System Tests 

 Dry bay fire protection systems are a relatively new concept that will be fielded on 

selected aircraft in production now or in the future that warrant its use due to the combat threat 

environment and the mission profile of the aircraft. These systems have been verified recently 

by live fire testing using various ballistic threats to assure performance in the fire extinguishing 

of such events. 

 Rapid fire detection and discharge of fire suppression chemicals provide the potential for 

the greatest success of effective fire suppression against ballistic threats. The speed of response 

of both the sensor and the suppressor enable the concept to effectively respond to projectileinduced fires. [13] 

3.2.3 Aircraft Engine Nacelles 

3.2.3.1 Fire Zone Definition 

 The engine nacelle is defined as the region surrounding the exterior of the jet engine case, 

shrouded by an outer cover, and typically ventilated. [5] The engine nacelle varies in shape and 

size, but is typically annular with a length and diameter of the same order as the engine it 

encases. Fuel and hydraulic lines, pumps, and lubrication systems are located within the nacelle 

volume. Ventilation is provided to prevent the buildup of combustible vapors, and drain holes 

are located on the underside to reduce the amount of fluid that could pool in the event of a leak. 

[17] APUs are machinery units that provide supplemental, auxiliary, or emergency power to all 

or some subsystems of the aircraft. [12] 

3.2.3.2 Fire Incidence Rate 

3.2.3.2.1 Noncombat Fire Data 

3.2.3.2.1.1 C-130 

 The data given for the C-130 are peacetime incidents from the Incident Data Analysis 

Report, July 1994, Booz•Allen & Hamilton Inc. These data were made available by the USAF 

Safety Center and cover the time period of 1983 through 1993. There were 115 reported 

incidents (An incident is not necessarily a confirmed fire.) with 94 confirmed fires. In eleven of 

these incidents, halon 1011, 1201, or 1301 was used for extinguishment. There were eleven 

confirmed fires. Of these, seven occurred inflight and four occurred on the ground. [18] 
28

3.2.3.2.1.2 F-18 

 The F/A-18 fire history was obtained from Fixed-Wing Aircraft Fire Protection, halon 

1301 Fire Suppression Systems Effectivity Analysis, September 30, 1994, NAWCADLKEMISC-05-SR-0146. Excerpts from this report are given below. 

 Thirteen percent of F-18 fire incident aircraft were lost or destroyed due to fire. Eightysix percent of all aircraft losses (6 of 7 losses) were due to engine fires. Forty-seven of 54 F-18 

fire incident aircraft (87 percent) were not destroyed by fire incidents (An incident is not 

necessarily a confirmed fire.). 

 The F-18 engine halon fire suppression was used in 17 of 55 F-18 fires and was 

successful in extinguishing 12 fires. Therefore, the overall effectivity of F-18 engine halon 1301 

fire suppression system was 71 percent, when the system was utilized. The engine halon fire 

suppression system was used only in engine fires; no fire suppression was attempted in any fire 

occurring in the AMAD bays. Only in-flight engine fires were extinguished. The effectivity of 

the engine halon fire suppression system during in-flight fires was eighty percent, and this 

effectivity was the same for each engine. No ground engine fires were extinguished in two 

attempts using the engine halon fire suppression system. 

 In the five fires in which the engine halon fire suppression system failed to extinguish 

fires, three of the fires resulted in loss of aircraft, and two were extinguished by ground efforts 

after the aircraft landed. One of these two fires occurred in the AMAD bay and was fed by a 

massive fuel leak in the bay. 

 Based on the data contained in the F-18 aircraft fire incident narratives, 48 of 55 F-18 

aircraft fires (87 percent) were extinguished. Twenty-two percent of these fires were 

extinguished by the F-18 engine halon fire suppression system. Analysis of the Safety Center 

data indicates that this system is an effective fire protection system when used. 

• The F-18 engine halon fire suppression system extinguished 71 percent of F-18 

aircraft fires. 

• The F-18 engine halon fire suppression system extinguished 80 percent of F-18 

aircraft in-flight fires. 

• One area in which the engine halon fire suppression system has been unsuccessful is 

in extinguishing ground engine fires. The system was used unsuccessfully in two 

ground engine fires. Analysis of the Safety Center data also revealed several trends 

regarding F-18 aircraft fires: 

• Eighty-six percent of all aircraft losses were the result of engine fires. 

• Eighty-two percent of all fires occurred in areas protected by the F-18 engine 

halon fire suppression system. This supports the conclusion that the system is 

implemented to provide fire protection in those areas most susceptible to fire. 

• Seventy-three percent of all fires were engine fires. Inflight engine fires also 

accounted for 78 percent of all in-flight fires. 
29

• There were four fires that occurred in the AMAD bays, plus an additional fire that 

occurred in both an engine and AMAD bay. Even though the AMAD bays are 

protected by the engine halon fire suppression system, no fire halon suppression 

was attempted in any of these fires. The fire that occurred in both an engine and 

AMAD bay caused the engine system halon bottle to vent rendering the aircraft 

without any fire protection agent. 

• Eighty-two percent of fires occurred in flight, and seventy-eight percent of inflight fires were engine fires. Eighty-seven percent of all fires and of all in-flight 

fires were caused by material failures. Areas susceptible to material failures 

included high-pressure compressors, afterburner liners and spraybar pigtails, and 

the AMAD bay (hydraulic pump failures and source of several fuel leaks). 

 The overwhelming fraction of peacetime aircraft losses comes from inflight engine fires. 

[19] 

3.2.3.2.1.3 C-17 

 The C-17 made its maiden flight on Sept. 15, 1991, and the first production model was 

delivered to Charleston Air Force Base, S.C., on June 14, 1993. The 17th Airlift Squadron, the 

first squadron of C-17s, was declared operationally ready Jan. 17, 1995. The Air Force is 

programmed to receive a total of 120 C-17s by the year 2005. [4] 

 No aircraft have been lost or destroyed by fire. There have been no engine fires reported. 

[20] 

3.2.3.2.1.4 H-60 

 The H-60 fire history was obtained from Rotary-Wing Aircraft Fire Protection, halon 

1301 Fire Suppression Systems Effectivity Analysis, May 26, 1994, NAWCADLKE-MISC-05-

SR-0132. Excerpts from this report are given below. 

 Five of the six H-60 aircraft fires were successfully extinguished; another H-60 aircraft 

was lost at sea. 

 The H-60 engine halon fire suppression systems were utilized successfully in two of three 

APU ground fire incidents (An incident is not necessarily a confirmed fire.). The reserve 

capability was utilized unsuccessfully in the incident that the engine halon fire suppression 

system failed to extinguish an APU fire. Therefore, when used to extinguish APU ground fires, 

the H-60 engine halon fire suppression system was 67 percent effective. No fire suppression was 

attempted in either of the two in-flight engine fires, one of which resulted in loss of aircraft. 

 Based on the data contained in the H-60 aircraft fire incident narratives, five of six Hsixty aircraft fires (eighty-three percent) were extinguished. Fifty percent of these fires were 

extinguished by the H-60 halon fire suppression systems. However, all extinguished fires were 

APU fires that occurred on the ground. Analysis of the Safety Center data indicates that the 

halon fire suppression systems were 75 percent effective when used. 
30

 Three of the six H-60 fire incidents occurred in the APU. Two occurred during 

maintenance activities and one occurred during preflight checks. Two of these APU fires were 

the result of residual fuel in the APU combustion section from previous start attempts. The 

manner in which these fires occurred suggests that procedures for performing maintenance or 

start-up could be addressed to promote less reliance on the halon fire suppression systems by 

preventing fires as part of the procedures [21]. 

3.2.3.2.1.5 CH-47 

 Noncombat data regarding aircraft lost, destroyed or not destroyed by fire, how fires were 

extinguished, incidents where halon fire suppression systems were not utilized or unknown, and 

where and why CH-47 fires occurred were not available at the time of this report. 

3.2.3.2.1.6 F-16 

 The data given are peacetime incidents from the Incident Data Analysis Report, July 

1994, Booz•Allen & Hamilton Inc. These data were made available by the USAF Safety Center 

and cover the time period 1983 through 1993. There were 149 incidents (An incident is not 

necessarily a confirmed fire.) with 111 confirmed fires. There were 56 total incidents that 

occurred in the engine, jet fuel starter, or tailpipe areas. There were 49 confirmed fires. Of 

these, 29 incidents occurred inflight with 22 being confirmed fires. Of these, 27 incidents 

occurred on the ground, and all were confirmed fires. [18] 

3.2.3.2.2 Combat Fire Data 

 Most engine nacelle incidents occurred during peacetime. However, the potential of a 

combat-induced engine nacelle fire definitely exists and is currently being considered in several 

ballistic engine nacelle programs. It is important to note that the current halon 1301 engine 

nacelle fire extinguishing systems are certified only to a safety related hazard not a threatinduced one. 

3.2.3.3 Hazards to be Protected against by Halon 1301 Systems 

 Engine nacelle fire protection systems are designed to protect against events such as 

ruptured or leaking fuel, hydraulic fluid, or oil lines within the nacelle. In these circumstances, 

flammable fluids can leak onto the hot engine case or accessory components and ignite. These 

systems can also protect against the results of catastrophic events such as thrown turbine blades 

that instantaneously rupture fuel sources or overheating components that can initiate fluid fire 

scenarios. The first step in such cases is to shut down the engine, when the proximity fire 

detector confirms a fire is present and the pilot is satisfied that a true fire event has occurred. 

Even with the engine shut down and flammable fluid supply turned off, up to a minute or more 

of fuel and other flammable fluids flowing into the fire zone can occur, sometimes under highpressure, depending upon the location and nature of the failure and the capability to remotely 

arrest the flow near the point of damage. Under these conditions, a supply of fuel can be 

maintained for a lengthy period to create robust fire conditions that, left unchecked, can heat and 

burn through surrounding structure and threaten the welfare of the aircraft, creating fire 
31

conditions in collateral areas before the fuel is drained, thereby weakening key structures. In 

addition, impacts into the engine nacelle by ballistic projectiles in combat can also create failure 

conditions and resultant fires (provided that the engine case is not penetrated, which could result 

in catastrophic engine failure becoming the more immediate threat). [12] An additional fire 

hazard associated with the aircraft engine nacelle arises from the fact that even after 

extinguishment is achieved, a substantial potential exists for reignition of the fire from hot 

surfaces. Hot surface reignition remains a threat as long as fuel vapor and air can come in 

contact with sufficiently hot surfaces. Suppression of the hot surface reignition fire hazard in the 

engine nacelle requires an additional amount of agent over that required for flame 

extinguishment in order to maintain extinguishment until the hot surfaces cool. [17] 

 APUs are used to provide supplemental, auxiliary, or emergency power to all or some of 

the subsystems of the aircraft, either on the ground or in flight. These units function and 

generate power independently from the normal aircraft engine systems. The power units may be 

miniature turbines or other power generating equipment, but are typically smaller than the 

normal jet engine propulsion systems. These compartments must be protected against potential 

fires, since the possibility of fuel, hydraulic fluid, or oil leakage onto the hot power unit and 

equipment or catastrophic unit failure can create fire scenarios just as in the engine nacelles. For 

many military aircraft, the engine fire protection system is plumbed to be alternatively used in 

the auxiliary power unit compartment, since in most cases the engine fire protection system’s 

capacity is more than adequate for the smaller volume of the APU bay. In some cases, however, 

the APU compartment may have a larger free volume than an individual engine nacelle or 

otherwise require a greater quantity of extinguishant than the nacelle, so great care must be taken 

to assure that sufficient capacity is designed for either use. APU compartments can be 

ventilated, so provision must be made for dilution of extinguishant by ventilation airflow during 

discharge. In many cases, however, the ventilation system is designed to be closed during 

discharge, hopefully sealing off the compartment. For many military transport and most 

commercial aircraft, an independent fire protection system is designed for a remote APU 

compartment, which may be located within the cabin or cargo section, or in the tail section. 

These systems must then be designed separately from engine nacelle systems. 

 An engine nacelle or auxiliary power unit has hot operating components and uses fuel or 

flammable fluids under normal operating conditions. The zones are considered primary fire 

zones, because merely a failure in a flammable fluid system, which can rupture and spray fluid, 

can result in ignition on a normally hot component surface, initiating a fire. [12] 

3.2.3.3.1 Effect of Airflow 

 An engine nacelle fire is typically a turbulent diffusion flame stabilized behind an 

obstruction in a moderately high-speed airflow (that range from 0.57 kg/s (1.25 lb/s) to 1.25 kg/s 

(2.75 lb/s)). The fuel source for a fire in the nacelle is most often leaking pipes carrying jet fuel 

or hydraulic fluid; the fire can usually be described as either a spray fire or a puddle or pool fire. 

 Pool fires are more difficult to extinguish than spray fires. In addition, it has been 

observed that under conditions of increasing airflow velocities, the required concentration of 

extinguishing agents for both pool and spray fires decreases. These results have been 
32

rationalized in terms of flame stability and structure; the pool fire flames are believed to have a 

“premixed” structure and are more stable than the “diffusion” structure spray flames, and both 

types of flame are believed to be less stable (more easily extinguished) at high airspeeds. 

Premixed flames require higher extinguishing concentrations than diffusion flames. [22] 

 Typically, there is airflow through the nacelle to provide cooling of hot surfaces and to 

sweep out combustible vapors. While serving these important functions, the airflow also dilutes 

the extinguishing agent after a discharge, and carries it out of the nacelle rapidly. The number of 

air exchanges per unit time (volumetric air flow/net volume) depends on the aircraft design and 

may be as high as one per second. Clearly, the amount of agent required to achieve a specified 

concentration in the nacelle depends on the airflow and the nacelle free volume. The nacelle free 

volume is defined as the total nacelle volume minus the volume due to clutter. 

3.2.3.3.2 Pool Fires 

 A pool fire resulting from a puddle of jet fuel or hydraulic fluid can pose the most serious 

fire hazard under certain conditions in an engine nacelle. In airflow, the stability of a pool fire, 

which incorporates a premixed flame, can be greatly enhanced if an obstacle at the leading edge 

of the pool is present. In some nacelle configurations, obstacles in the form of structural ribs or 

other bluff bodies are present at locations where combustible liquids could form a puddle. Fire 

suppression tests in configurations such as these have shown that the stabilizing effect of a baffle 

in front of a pool fire can be very significant. Test results show that under similar air flow and 

baffle height conditions, a baffle-stabilized pool fire is dramatically more difficult to extinguish 

than a baffle-stabilized spray fire where the baffle is located in the middle of the flow field. 

3.2.3.3.3 Spray Fires 

 A fuel spray represents a unique combustion situation that incorporates a diffusion flame. 

A ruptured high-pressure fuel, lubricant, or hydraulic fluid line can supply a steady flow of fuel 

for a fire stabilized behind obstacles in the engine nacelle. Small droplets quickly evaporate and 

the momentum from the spray efficiently entrains the air necessary for combustion. 

Extinguishment of the burning spray occurs when a critical amount of agent becomes entrained 

within the combustion zone. Flame stability in this case is also influenced by parameters other 

than the rate of agent entrainment such as the airflow rate and temperature, the fuel type, the 

pressure, and the type of agent employed. 

3.2.3.3.4 Hot Surface Ignition 

 After suppression of a nacelle fire, hot fuel vapor may exist at levels that are flammable, 

leading to the possibility of reignition of the fire. A puddle of hydraulic fluid or jet fuel from a 

leaking fuel line will vaporize as heat is transferred from a nearby hot metal surface. Under 

normal engine operating conditions, hot metal surfaces that could cause reignition exist along the 

interior wall of the nacelle that separates the jet engine combustor from the nacelle. In addition, 

hot metal surfaces may be engendered by the heat of the fire itself. Reignition then arises from 

contact of the reactive fuel/air mixture with the hot metal surface. 
33

 Conditions that lead to hot surface reignition fires are controlled by the time and 

temperature history of the reactive mixture and to a lesser extent, by the type of metal surface 

and the chemical composition of the fuel. Test have shown that when a hot (700 °C (1300 °F)) 

metal surface is present, fire suppression requires almost an order of magnitude more agent than 

if the hot surface is not present, presumably due to reignition. Strategies to prevent reignition 

include removing fuel vapor, reducing surface temperatures either through design changes or 

active cooling, and inerting the fuel/air mixture with additional suppressant. 

3.2.3.3.5 Clutter 

 The total mass of agent to be stored in the engine nacelle fire extinguisher is normally 

based on the amount needed to quench the worst case anticipated fire hazard. For engine 

nacelles with ribs and other obstructions, this is a baffle-stabilized pool fire. But engine nacelle 

fires can occur either in the form of a pool or a spray. In either type of fire, flame stability is 

enhanced by flow field obstacles (or clutter), which act as flame holders. It is well known that if 

a flame is established behind a flow obstacle or bluff body, a recirculation zone will form. The 

presence of the recirculation zone enhances flame stability, although flame “blow-out” will occur 

if air flows past the obstacle at sufficiently high velocities. 

 Also by definition, a smooth nacelle has no circumferential ribs protruding into nacelle 

free volume; ribs are often incorporated into the nacelle to provide structural rigidity. A rough 

nacelle has circumferential ribs protruding less than 15 cm (6 in) into the nacelle; a deep frame 

nacelle has circumferential ribs greater than 15 cm (6 in) protruding into the nacelle, or a 

configuration with cavities 15 cm (6 in) or more in depth. A smooth nacelle may contain clutter 

such as electronic housings, hydraulic and fuel lines, transducers, and clamps that may create 

flow disturbances. 

 The time required for an agent to entrain into the recirculation zone is a key parameter in 

the effectiveness of suppression with respect to baffle-stabilized flames. This characteristic 

mixing time or residence time is extremely important in developing fire protection strategies and 

system designs, because it influences the free-stream agent concentration and duration required 

to obtain extinction of the flame. Agent entrainment into a baffle-stabilized combustion zone is 

governed by the free-stream flow velocity, the baffle size and shape, and the free-stream agent 

concentration/duration. The agent concentrations required for suppression of baffle-stabilized 

fires can be a factor of two larger than agent concentrations required to extinguish cup burner 

flames burning the same fuel [17]. 

3.2.3.4 Flame Suppression Time Requirements 

 This specification is verified by experiment under realistic conditions. [12] Actual 

suppression test requirements do not exist. It is believed that if extinguishment can occur within 

seconds that the success rate is increased. 
34

3.2.3.5 Current System Tests 

 All of these engine nacelle systems are “certified,” or approved, in a given design 

configuration for a particular fire zone application and aircraft. The current specifications for 

halon 1301 require a minimum of six percent concentration by volume in air be present 

simultaneously at all points in the engine nacelle for a minimum of 500 ms. This specification is 

verified by experiment under realistic conditions. [12] 

3.2.4 Aircraft Fuel Tanks 

3.2.4.1 Fire Zone Definition 

 Ullage (the void space above the fuel level in a fuel tank) in aircraft fuel tanks can have a 

potentially explosive fuel-air mixture. If initiated by a combat threat, an explosion can result. 

Currently two aircraft systems (F-16 and F-117) use halon 1301 to inert these fuel tanks and 

prevent these phenomenon from occurring. [24] 

 Several other fuel tank inerting approaches exist. These include utilization of foam, 

nitrogen inertion, and a solid propellant gas generator system. Foams are a fully passive system 

used to suppress flame spread in the fuel tank ullage. The nitrogen inerting system is a moderate 

weight active explosion-proofing mechanism that operates on the principle of oxygen dilution of 

the ullage and the fuel at a level below the concentration required to propagate fire. One 

example of a nitrogen inerting system is the on board inert gas generating system (OBIGGS). 

OBIGGS filters N2 directly from engine bleed air. OBIGGS eliminates the need to service either 

nitrogen or halon bottles. The use of liquid nitrogen (LN2) inerting is another nitrogen inerting 

system. A third example of a nitrogen inerting system involves the use of gaseous nitrogen 

(stored in bottle form). Solid propellant gas generators might also provide a solution to the fuel 

tank inerting problem. A solid propellant gas generator system used for extinguishing a fuel tank 

explosion is in the early stages of conceptual development. [25] 

3.2.4.2 Fire Incidence Rate 

3.2.4.2.1 Noncombat Fire Data 

 Fuel tank explosions are not frequent during peacetime. They are more a function of a 

combat incident. 

3.2.4.2.2 Combat Fire Data 

 Historically, fuel fire and explosion is a major cause of aircraft losses in combat. Data 

from Southeast Asia show over half of the aircraft combat losses involved fuel fires and 

explosions. While other factors might also have contributed to the loss (e.g., pilot killed, loss of 

control, etc.), this fact, nonetheless, indicates the fuel system is a very significant contributor to 

an aircraft’s vulnerability. Therefore, to increase survivability, various techniques are used to 

reduce the vulnerability of the aircraft’s fuel system to this significant threat effect. [24] 
35

 No Southeast Asia data exist for the F-16 or the F-117, since neither existed during that 

conflict. No combat data for aircraft whose fuel tanks were inerted by halon 1301 (F-16 or the 

F-117) were available. 

3.2.4.3 Hazards to be Protected Against by halon 1301 System 

 Fuel tank explosions are a result of ullage deflagrations where the combustion 

overpressure generated exceeds the structural strength of the tank. With large ignition sources, 

combustion will occur and overpressures will vary according to the threat level, tank volume, 

and oxygen concentration. If the combustion wave propagates throughout the ullage with near 

stoichiometric fuel/air mixture, a pressure increase of over 790 kPa (100 psig) (eight times 

atmospheric pressure) is theoretically possible. The current halon inerting system must also 

provide protection from in-tank arcing due to lightning, electrostatic discharge, and combat 

threats. 

3.2.4.4 Flame Suppression Time Requirements 

 The current halon 1301 inerting systems provide protection for about 8 minutes. After 

that time the bleed-air into the ullage will have diluted the inertant below its effective 

concentration. Therefore, the pilot activates the system by releasing the halon shortly before 

entering combat. To prevent the deflagration pressure from returning the fuel tank, the 

quenching must occur within about 200 ms, similar to the required time limit for the mist fireball 

suppression in dry bay fires. However, in the inerting case, the agent is already deployed. Thus 

detection and dispersion time intervals do not consume part of the total suppression time 

requirement. 

3.2.4.5 Current System Tests 

 The Air Force Research Laboratory uses the W-Tank (380 liter (100 gallon rectangular 

tank)) to certify fuel tank inerting systems. 

 Tank overpressure is the criterion used to determine the effectiveness of the inerting 

agent, as it is the sudden pressure pulse that can result in failure of the fuel tank. The inertant 

physically extracts heat. By the dilution provided by the inertant, there is less fuel and air to 

react. 

Many common parameters that affect tank overpressure are given below. 

• Fuel temperature--affects ullage fuel vapor composition; 

• Ullage temperature--affects reaction rate, vapor transfer to ullage; 

• Ullage pressure--affects final peak pressure value; 

• Total energy release of ignition source--affects time to peak pressure, energy required 

to be dissipated via greater inertant; 

• Inertant type--affects estimated heat extraction rate of reaction (physically and 

possibly chemically); and 
36

• Inertant concentration--affects rate of heat extraction. [26] 

3.2.5 Shipboard Machinery and Storage Spaces 

3.2.5.1 Fire Zone Definition 

 The following compartments are protected by halon 1301: main machinery rooms 

(MMRs), auxiliary machinery rooms (AMRs), flammable liquid storerooms (FLSRs), paint issue 

rooms, pump rooms, and generator room for both the DDG 51 (Arleigh Burke) Class: Aegis 

Guided Missile Destroyer and the LHD 1 (WASP)/LHA 1 (Tarawa) Class: Amphibious 

Helo/Landing Craft Carriers. 

3.2.5.2 Fire Incidence Rate 

3.2.5.2.1 Noncombat Fire Data 

 The Naval Research Laboratory (NRL) identified forty-two halon 1301 fire suppression 

incidents between 1982 and 1997 primarily from NAVSEA on Navy Safety Center investigation 

reports. Of the 42 incidents, 26 provided detailed accounts, twelve provided no information, and 

four provided few details, but said that the fires had been extinguished with halon. Although for 

the majority of the fire incidents a single shot of halon 1301 extinguished the fire, two incidents 

(out of 26) required a second shot of halon to achieve suppression. In incidents that required 

additional agents (halon, AFFF, or other) release, it was found that fuel soaked lagging was often 

a key contributor to agent failure. There were also six reflash incidents. Two of the fires used 

the secondary halon for suppression and occurred in a Gas Turbine Module (GTM) and in a 

diesel generator compartment. AFFF hoses were used on the remaining fuel of the reflash 

incidents by the ship fire party during reclamation procedures. One of these fires occurred in a 

main machinery room and the other three occurred in a diesel generator compartment. The 

occurrence of reflashing is due to the reduction of agent concentration due to compartment 

leakage, agent decomposition. 

 There were four incidents, which occurred in GTMs, where both the fires and second 

shots were ineffective in extinguishing the fire. All four incidents occurred in GTMs that were 

protected by 27.2 kg (60 lb) of halon 1301 per shot. NAVSEA recognized the limitations of the 

GTM total flooding system and increased the total flooding agent capacity by over 50 percent 

per shot, to 43.1 kg (95 lb) of halon 1301 per shot. Other modifications were also made. All 

GTMs currently under construction (e.g.; DDG-51 Class ships) are being built with the 43.1 kg 

(95 lb) per shot halon 1301 system. A large number of GTMs, however, are still protected by 

CO2. Because the objective of this report is to identify halon 1301 discharges, no CO2 GTM fire 

suppression data have been collected. 

 An update to the NRL study was also available. This report identified an additional six 

reported halon 1301 discharge incidents. A total of five of the discharges were to achieve fire 

suppression. The primary shot of halon was sufficient for three of the fires in which other agents 

were required for suppression or reflashes occurred. A reflash occurred in one fire which was 

suppressed with AFFF and one used AFFF in conjunction with a halon discharge to suppress the 
37

fire. One halon discharge was used to protect a paint locker space which had a fully involved 

fire exterior of the space. 

 The total estimated quantity of halon discharged from 1982 to 1997 for suppression is 

16,500 kg (36,000 lb), and for accidental, malicious, and other types of non-fire related 

discharges is 6,500 kg (14,000 lb). [27] 

 It may be sufficient (but not desirable) in the case of multiple simultaneous incidents for 

some of the smaller unoccupied compartments protected by halon for the fire to be controlled 

and isolated. They would be dealt with after larger operational issues have been addressed. 

 Table 6 summarizes halon 1301 use from 1982 to 1997, excluding agent used during ship 

acceptance testing. Table 7 summarizes halon 1301 fire suppression performance. 

Table 6. Shipboard Halon 1301 Discharges 

Reported halon 1301 Discharge Incidents* Number of Incidents Estimated Halon Discharged 

in kg (lbs) 

Fire Suppressions 42 16,500 (36,000) 

Accidental discharges/ other 14 6,500 (14,000) 

Total Reported Incidents 56 23,000 (50,000) 

* An incident may involve a single or dual shot discharge. 

Table 7. Shipboard Halon 1301 System Performance.* 

halon 1301 Suppression Performance Number of 

Incidents 

Fire Location (Compartment or 

Enclosure ) 

Suppressions by primary halon, no reignitions 14 Diesel Generator (SSDG), GTM, 

Paint Locker 

Reflashes suppressed by secondary halon 2 SSDG, GTM 

Reflashes suppressed by AFFF 4 MMR, SSDG 

Suppressions by secondary halon (not suppressed by 

primary) 

2 GTM, SSDG 

System Failures (unsuccessful fire suppression) ** 4 GTM 

* Only the 26 incidents where sufficient data were available are used in this table. 

** Unsuccessful fire suppressions after two shots were discharged. 

3.2.5.2.2 Combat Fire Data 

 These data were not compiled. 

3.2.5.3 Hazards to be Protected Against by halon 1301 System 

 Fires in MMRs, AMRs, engine enclosures, and generator rooms result from the ignition 

of a pressurized fuel (diesel/hydraulic or lubricating oil) leak or ignition of fuel-soaked insulating 
38

material. Leaks onto hot surfaces result in three-dimensional spray fires with cascading liquid 

flow on complex surfaces and into flaming pools. 

 Fires in FLSRs and paint issue rooms result from burning fuel cascading over highly 

obstructed and fuel loaded shelves and into flaming pools. [8] 

 The LHD class has high pressure steam plants. The steam plants have high temperature 

piping that can provide possible ignition and reignition sources. Further, these pipes are slow to 

cool. While turbine and diesel propulsion plants have high temperature surfaces, these cool 

much faster. Unvented high-pressure steam remains in the steam plant piping after engine shut 

down. 

3.2.5.4 Flame Suppression Time Requirements 

 Current suppression times are of the order of minutes. 

 The fire suppression system has a reignition protection of 15 minutes hold time 

(minimum time from agent discharge to compartment reentry). Reflash in machinery spaces as 

well as other compartments is a serious consideration. During reclamation procedures, agent 

concentration will decrease and additional oxygen will be available. 

3.2.5.5 Current System Tests 

 The Navy utilizes the following intermediate and full-scale test facilities to assist in the 

development of fire suppression systems. 

 The Full Scale Fire Test Facility (ex-USS Shadwell, LSD-15) is a 139.3 m (457 ft), 

8,165,000 kg (9,000 ton) landing ship dock, located at the U.S. Coast Guard's Fire and Safety 

Test Detachment, Little Sand Island, Mobile, Alabama. All aspects and ship systems important 

to damage control are maintained on the ship, i.e., ventilation, fire main, heating and air 

conditioning, electrical, lighting, and internal communication systems. Three damage control 

lockers are also maintained. [28] 

 The Chesapeake Bay Fire Test Facility is concerned with all aspects of shipboard fire 

safety, particularly as related to fight decks, submarines and interior ship conflagrations. The 

emphasis is on providing facilities for intermediate scale, credible evaluations of firefighting 

agents, systems and training concepts under more realistic, shipboard conditions. In many cases, 

the facility provides a vital link between laboratory testing and full scale, proof of concept on the 

ex-USS SHADWELL. [29] 

 Halon concentration uniformity is frequently not well characterized. Based on NRL 

testing aboard the ex-USS SHADWELL, variations of at least ± 20 percent are to be expected; 

typical variation can be far broader. Agent distribution tests in a Cruiser (CG 47 - 

TICONDEROGA Class) Main Machinery Room (MMR) measured agent concentration variation 

as a whole number factor. [8] 
39

3.3 Model Fires And Flames For Use In Research On Alternatives To halon 1301 

 During the course of the NGP, a large number of experiments will be conducted, both at 

laboratory scale and in realistic test fixtures. Further, considerable effort will be devoted to 

computer modeling of the fire phenomena in order to ensure the applicability of the new fire 

suppression technologies. 

 To aid this, we have constructed a small set of model fires. These capture the essence of 

the fires actually experienced by the weapons systems, as documented earlier in this paper. 

3.3.1 Mist Fireball Explosion 

 This captures the essence of both the ground vehicle crew compartment and the dry bay 

fires. An appropriate laboratory apparatus for studying this model is an opposed flow diffusion 

flame (OFDF). [30] 

3.3.2 Spray Flame 

 This simulates fires that might occur in engine nacelles and dry bays. An appropriate 

laboratory apparatus for studying this model is Dispersed Liquid Agent Fire Suppression Screen 

(DLAFSS). [31] 

3.3.3 Obstructed Pool Fire 

 This simulates fires that might occur behind clutter in engine nacelles, storage 

compartments and shipboard machinery spaces. An appropriate laboratory apparatus for 

studying this model is the Transient Application Recirculating Pool Fire (TARPF) apparatus. 

[32] 

3.3.4 Inert Atmosphere 

 This simulates conditions that are desirable in fuel tank ullage, where an ignition source 

should not generate a sustained ignition of a fuel/air mixture. An appropriate laboratory 

apparatus for studying this model is ASTM E 2079. [33] 

3.4 Description of Representative Halon 1301 Systems In Current Weapons 

Platforms 

 This section compiles characteristics and limitations of the systems that new fire 

suppression technologies will replace or into which they will be retrofitted. The descriptions of 

the environments of the current systems compiled during this program will serve as boundary 

conditions for the new technologies to be developed in subsequent Elements of the NGP. 
40

3.4.1 Ground Vehicle Crew Compartment Halon 1301 System Configurations 

3.4.1.1 M992 FAASV Ammunition Resupply Vehicle 

3.4.1.1.1 System Configuration Description 

 The M992 FAASV has a halon 1301 extinguisher system for both the engine and crew 

compartments. There are six which serve the crew compartment. Two crew compartment 

bottles may be activated manually. Manual activation is accomplished using pull handles located 

in the driver’s compartment and outside the vehicle. There are four optical sensors in the crew 

compartment which sense the flash from a ballistic event and activate the extinguishers. [2] 

 Table 8 displays the fire suppression system configuration for the M992 FAASV 

Ammunition Resupply Vehicle. 

Table 8. M992 FAASV Ammunition Resupply Vehicle Fire Suppression System 

Configuration. 

 M992 FAASV Ammunition Resupply Vehicle 

Crew Compartment 

 Vehicles 1-344 Vehicles 345 and greater 

GENERIC 

Number of vehicles 664 (fielded units at the end of 1999) 

Service cycle refill (years) n.a. 

Fire types (pool fires, mist...) Mist fireball explosion, pressurized hydraulic spray fire, dry bay fire 

Estimated halon use/year/vehicle (kg (lb)) n.a. n.a. 

FIRE ZONE 

# of fire zones 3 (hydraulic reservoir, fuel cell, pressurized hydraulic lines) 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) n.a. n.a. 

Fire zone volume (cm3 (in3)) n.a. n.a. 

Fire zone free volume (m3 (ft3)) n.a. n.a. 

EXTINGUISHANT 

# of halon systems 2 (two 4.5 kg (10 lb) bottles for 

each independent discharge) 

3 (three 3.2 kg (7 lb) bottles for 

each independent discharge) 

Extinguisher trigger mode Automatic 

Extinguisher volume (cm3 (in3)) Range from 204 to 1224 in3

Size of extinguishant container (cm, cm, cm (in, in, 

in)) 

n.a. n.a. 

Storage compartment for extinguishant bottle (cm, cm, 

cm (in, in, in)) 

n.a. n.a. 

Free volume in storage compartment (cm3 (in3)) n.a. n.a. 

Normal charge and pressure of extinguisher container 

(MPa (psi)) 

n.a. n.a. 

Max extinguisher container pressure (MPa (psi)) n.a. n.a. 

Extinguisher container percent filled (%) n.a. n.a. 

Extinguisher container orientation (upright with valves 

at bottom) 

upright 

Extinguisher container weight without Halon (kg (lb)) n.a. n.a. 

Halon wt (kg (lb)) 4.5 kg (10 lb) 3.2 kg (7 lb) 

Extinguisher container location (inside/outside fire 

zone) 

Two bottles are attached to the 

bulkhead at the front of the 

compartment and two are located 

approximately in the middle of 

the crew compartment. 

Two bottles are attached to the 

bulkhead at the front of the 

compartment and four are located 

approximately in the middle of 

the compartment. 

Strategy for use Vehicles numbered 1 – 344 use a Vehicles numbered 345 and 
41

 M992 FAASV Ammunition Resupply Vehicle 

Crew Compartment 

dual-shot system for the crew 

compartment. Each independent 

discharge involves two 4.5 kg 

(10 lb) halon bottles (9 kg (20-lb) 

total). For each activation, one 

of the bottles attached to the 

bulkhead and one of the bottles 

in the middle of the compartment 

are discharged. 

above also have a two-shot 

system for the crew 

compartment, however, each 

independent discharge uses three 

3.2 kg (7 lb) bottles (9.5 kg (21-

lb) total). For each activation, 

one of the bottles attached to the 

bulkhead and two of the bottles 

in the middle of the crew 

compartment are discharged. 

 # of shots 2 

 Manual/automatic Automatic 

 Procedure for activation 4 optical sensors 

 Time to release halon 1301 The system specification does not list the interval from detection of 

the fire until start of discharge. 

The halon will probably be fully discharged within 100 ms. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method Cone placed in front of discharge nozzle. 

Extinguisher discharge rate (kg/min (lb/min)) n.a. n.a. 

Distribution system plumbing 

 Inner diameter (cm (in)) 

 Length (cm (in)) 

 Shape (bends, elbows) 

# and nature of nozzles/pipe terminations 

The only plumbing associated with the fire extinguishment system is a 

cone placed in front of the discharge nozzle to improve the halon 

distribution. There is no additional plumbing. 

MODIFICATION POTENTIAL 

Potential for increased number or increased size of 

storage bottles 

It may be possible to find room for larger and/or more numerous 

bottles if an agent less volume efficient than halon were used. 

Restriction on alternative fluids 

(very/modestly/slightly) 

n.a. 

Access of current distribution plumbing for retrofit 

(Please rate with percent of ease (e.g., 20 percent of 

the plumbing is difficult to access, 80 percent of the 

plumbing is easy to access.)) 

n.a. 

Access & available space for additional distribution 

plumbing or nozzle modification (Please rate with 

percent of ease (e.g., 20 percent of the plumbing is 

difficult to access, 80 percent of the plumbing is easy 

to access.)) 

The crew working volume is very large. The halon distribution 

system was changed to modify distribution of the agent. It is possible 

to add nozzles although they are not used in the current systems 

because of time delays associated with most nozzles. 

How tight is the bottle space? n.a. 

Is the plumbing readily accessible for replacement? n.a. 

Is the plumbing readily accessible for adding another 

distribution part? 

n.a. 

Is the plumbing readily accessible for changing the 

pipe end? 

n.a. 

Extinguisher Growth Potential n.a. 

OTHER 

Suppression success fraction n.a. 

Extinguisher system manufacturer n.a. 

Evidence of halon distribution characteristics (from 

certification tests)—design concentration required for 

extinguishment 

7 percent - Halon concentration will be a function of location within 

the compartment. 

Range of expected operating temperatures for the 

bottle and the plumbing (oC (oF)) 

Any system in a vehicle must survive –45 oC (-49 oF). The system 

must function properly at –32 oC (-26 oF) and above. The bottles are 

all in the crew compartment, and thus are not exposed to the high 

temperatures associated with engine compartments. The maximum 

temperature to which the bottles will be exposed is approximately 

63 oC (145 oF). 

n.a. – not available
42

3.4.1.1.2 System Schematic 

 Figure 2 displays the fire suppression system configuration for the M992 FAASV 

Ammunition Resupply Vehicle. 

Figure 2. M992 FAASV Ammunition Resupply Vehicle Fire Extinguishing System 

Schematic 

3.4.1.1.3 Sequence of Events 

 Fires are detected automatically through use of discriminating dual-band infrared sensors. 

When a weapon, e.g., a shaped charge jet defeats the armor and penetrates the crew 

compartment, the hot spall from the armor and ionized hot air emit intense electromagnetic 

radiation. (The adjective “discriminating” implies that when the sensor sees the intense 

electromagnetic radiation, the fire detection shuts down for 5 ms.) The fire sensor sees this and 

shuts down to allow the initial radiation to decay. The sensor then reactivates and if it still sees a 

strong signal, it causes the rest of the extinguishing system to function, releasing halon. The 

assumption is that the long-term signal is caused by the combustion of hydrocarbon components 

while the initial signal will be present whether or not the weapon has encountered a source of 

hydrocarbons. Thus, the sensor discriminates between the initial event of penetration and the 

presence of a fire. Once the reactivated sensor detects the fire, a signal is sent to the control box, 

which operates the solenoidal valve of the halon reservoir. If the shaped charge jet passes 

through the fuel cell and into the crew compartment, the mist fireball is expected to be several 

feet in diameter by the time the fire suppression system releases halon. A similar situation 

applies to the hydraulic system that is in the crew compartment. 
43

3.4.1.2 M1 Tank 

3.4.1.2.1 System Configuration Description 

 The M1/M1A1 tank has a halon 1301 extinguisher system for both the engine and crew 

compartments. One bottle serves the crew compartment. Each bottle contains 7.0 pounds of 

halon 1301. The bottle may be activated either manually or automatically. Manual activation is 

accomplished using pull handles located in the driver’s compartment. There are three optical 

sensors in the turret and one in the driver’s compartment. These sensors are designed to sense 

the flash from a ballistic event and activate the extinguishers. Table 9 displays the fire 

suppression system configuration for the M1 Tank. 

Table 9. M1 Tank Fire Suppression System Configuration. 

M1 Tank 

Crew Compartment 

GENERIC 

Number of vehicles 403 USMC 

Service cycle refill (years) n.a. 

Fire types (pool fires, mist...) Mist fireball explosion, pressurized hydraulic spray fire, dry bay fire 

Estimated halon use/year/vehicle (kg (lb)) n.a. 

FIRE ZONE 

# of fire zones 3 (hydraulic reservoir, fuel cell, pressurized hydraulic lines) 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) n.a. 

Fire zone volume (cm3 (in3)) n.a. 

Fire zone free volume (m3 (ft3)) n.a. 

EXTINGUISHANT 

# of halon systems 3 

Extinguisher trigger mode Automatic 

Extinguisher volume (cm3 (in3)) Range from 204 to 1224 in3

Size of extinguishant container (cm, cm, cm (in, in, 

in)) 

n.a. 

Storage compartment for extinguishant bottle (cm, 

cm, cm (in, in, in)) 

n.a. 

Free volume in storage compartment (cm3 (in3)) n.a. 

Normal charge and pressure of extinguisher container 

(MPa (psi)) 

n.a. 

Max extinguisher container pressure (MPa (psi)) n.a. 

Extinguisher container percent filled (%) n.a. 

Extinguisher container orientation (upright with 

valves at bottom...) 

upright 

Extinguisher container weight without Halon (kg 

(lb)) 

n.a. 

Halon wt (kg (lb)) 3.2 kg (7 lb) 

Extinguisher container location (inside/outside fire 

zone) 

Stored within the crew compartment. 

Strategy for use The entire series has the same size and location of halon bottles. Two 

of these bottles are used for independent releases within the engine 

compartment. The third bottle is used for the single-shot crew fire 

extinguishment. This bottle has a nozzle designed to ensure 

simultaneous flow of halon to the front of the vehicle where there two 

fuel cells are and to the rotatable turret basket which houses the other 

three crew members and an extensive hydraulic system. 

 # of shots 3 

 Manual/automatic Automatic with manual 3rd shot (used by crew) 

 Procedure for activation 4 optical sensors 
44

M1 Tank 

Crew Compartment 

 Time to release halon 1301 The system specification lists the interval from detection of the fire 

until start of discharge as 10 - 15 ms. The halon will be fully 

discharged within 100 ms. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method Nozzle 

Extinguisher discharge rate (kg/min (lb/min)) n.a. 

Distribution system plumbing 

 Inner diameter (cm (in)) 

 Length (cm (in)) 

 Shape (bends, elbows) 

# and nature of nozzles/pipe terminations 

The only plumbing associated with the fire extinguishing system is a 

nozzle used to direct the halon discharge. There is no additional 

plumbing. 

MODIFICATION POTENTIAL 

Potential for increased number or increased size of 

storage bottles 

The crew working volume is very small. It has been repeatedly stated 

that there is insufficient room in the crew compartment for additional 

bottles or larger bottles. 

Restriction on alternative fluids 

(very/modestly/slightly) 

n.a. 

Access of current distribution plumbing for retrofit 

(Please rate with percent of ease (e.g., 20 percent of 

the plumbing is difficult to access, 80 percent of the 

plumbing is easy to access.)) 

n.a. 

Access & available space for additional distribution 

plumbing or nozzle modification (Please rate with 

percent of ease (e.g., 20 percent of the plumbing is 

difficult to access, 80 percent of the plumbing is easy 

to access.)) 

It should be possible to modify nozzle design although any time 

delays associated with different nozzles may not be acceptable, 

especially if the fire is not extinguished within 250 ms. 

How tight is the bottle space? n.a. 

Is the plumbing readily accessible for replacement? n.a. 

Is the plumbing readily accessible for adding another 

distribution part? 

n.a. 

Is the plumbing readily accessible for changing the 

pipe end? 

n.a. 

Extinguisher Growth Potential n.a. 

OTHER 

Suppression success fraction n.a. 

Extinguisher system manufacturer n.a. 

Evidence of halon distribution characteristics (from 

certification tests)—design concentration required for 

extinguishment 

7 percent - Halon concentration within the crew compartment 

probably varies by a factor of at least two. 

Range of expected operating temperatures for the 

bottle and the plumbing (oC (oF)) 

Any system in a vehicle must survive –45 oC (-49 oF). The system 

must function properly at –32 oC (-26 oF)and above. The bottles are 

all in the crew compartment, and thus are not exposed to the high 

temperatures associated with engine compartments. The maximum 

temperature to which the bottles will be exposed is approximately 63 

oC (145 oF). 

n.a. – not available

3.4.1.2.2 System Schematic 

 Figure 3 displays the fire suppression system configuration for the M1 Tank. 
45

Figure 3. M1 Tank Fire Extinguishing System Schematic 

3.4.1.2.3 Sequence of Events 

 These fires are also detected automatically through use of dual-band infrared sensors. 

When a weapon, e.g., a shaped charge jet defeats the armor and penetrates the crew 

compartment, the sensor sees the event and sends a signal to the control box which operates the 

solenoidal valve of the halon reservoir, releasing the halon. If the shaped charge jet passes 

through the fuel cell and into the crew compartment, the mist fireball is expected to be several 

feet in diameter by the time the fire suppression system releases halon. A similar situation 

applies to the hydraulic system that is in the crew compartment. 

3.4.1.3 M2, M3 Bradley Fighting Vehicles 

3.4.1.3.1 System Configuration Description 

 The Bradley Fighting Vehicle has a halon 1301 extinguisher system for both the engine 

and crew compartments. There is one fire extinguishing bottle which serves the engine 

compartment. That bottle is located forward of the driver in the crew compartment and contains 

7.0 lb of halon 1301. The engine fire bottle is manually activated from the driver’s position or 

by a pull handle outside of the vehicle. There are two bottles each with 5.0 lb of halon 1301 to 

serve the crew compartment. These bottles may be activated either manually or automatically. 

There are four optical sensors in the crew compartment. These sensors are designed to sense the 

flash from a ballistic event and activate the extinguishers. These also are two portable 

extinguishers in the crew compartment each with 2.75 lb of halon 1301. 

 Table 10 displays the fire suppression system configuration for the M2, M3 Bradley 

Fighting Vehicles. 
46

Table 10. M2, M3 Bradley Fighting Vehicles Fire Suppression System Configuration. 

 M2, M3 Bradley Fighting Vehicles 

Crew Compartment 

GENERIC 

Number of vehicles 1602 

Service cycle refill (years) n.a. 

Fire types (pool fires, mist...) Mist fireball explosion, pressurized hydraulic spray fire, dry bay fire 

Estimated halon use/year/vehicle (kg (lb)) n.a. 

FIRE ZONE 

# of fire zones 3 (hydraulic reservoir, fuel cell, pressurized hydraulic lines) 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) n.a. 

Fire zone volume (cm3 (in3)) n.a. 

Fire zone free volume (m3 (ft3)) n.a. 

EXTINGUISHANT 

# of halon systems 2 

Extinguisher trigger mode Automatic 

Extinguisher volume (cm3 (in3)) Range from 204 to 1224 in3

Size of extinguishant container(cm, cm, cm (in, in, 

in)) 

n.a. 

Storage compartment for extinguishant bottle (cm, 

cm, cm (in, in, in)) 

n.a. 

Free volume in storage compartment (cm3 (in3)) n.a. 

Normal charge and pressure of extinguisher container 

(MPa (psi)) 

n.a. 

Max extinguisher container pressure (MPa (psi)) n.a. 

Extinguisher container percent filled (%) n.a. 

Extinguisher container orientation (upright with 

valves at bottom...) 

upright 

Extinguisher container weight without Halon (kg 

(lb)) 

n.a. 

Halon wt (kg (lb)) 2.8 kg (5 lb) 

Extinguisher container location (inside/outside fire 

zone) 

Both the M2s and M3s have the same size and location of halon 

bottles. The bottles stored within the crew compartment, closely 

spaced, immediately adjacent to each other, approximately in the 

middle of the compartment. 

STRATEGY FOR USE 

 # of shots n.a. 

 Manual/automatic n.a. 

 Procedure for activation 4 optical sensors 

 Time to release halon 1301 The system specification lists the interval from detection of the fire 

until start of discharge as 10 - 15 ms. The halon will be fully 

discharged within 100 ms. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method One discharges toward the front, the other toward the rear of this 

compartment. The halon discharges are unrestricted; no nozzles are 

used. This is intended to produce the shortest discharge time. 

Extinguisher discharge rate (kg/min (lb/min)) n.a. 

Distribution system plumbing 

 Inner diameter (cm (in)) 

 Length (cm (in)) 

 Shape (bends, elbows) 

# and nature of nozzles/pipe terminations 

There is no plumbing associated with the fire extinguishing system in 

the crew compartment. 

MODIFICATION POTENTIAL 

Potential for increased number or increased size of 

storage bottles 

The crew compartment is of medium size, but can be crowded with 

soldiers. Examination of the interior indicates that it may be possible 

to use larger fire extinguishing bottles. 

Restriction on alternative fluids 

(very/modestly/slightly) 

n.a. 
47

 M2, M3 Bradley Fighting Vehicles 

Crew Compartment 

Access of current distribution plumbing for retrofit 

(Please rate with percent of ease (e.g., 20 percent of 

the plumbing is difficult to access, 80 percent of the 

plumbing is easy to access.)) 

n.a. 

Access & available space for additional distribution 

plumbing or nozzle modification (Please rate with 

percent of ease (e.g., 20 percent of the plumbing is 

difficult to access, 80 percent of the plumbing is easy 

to access.)) 

It should be possible to add nozzles to the discharge valves, although 

any time delays associated with additional plumbing may not be 

acceptable. 

How tight is the bottle space? n.a. 

Is the plumbing readily accessible for replacement? n.a. 

Is the plumbing readily accessible for adding another 

distribution part? 

n.a. 

Is the plumbing readily accessible for changing the 

pipe end? 

n.a. 

Extinguisher Growth Potential n.a. 

OTHER 

Suppression success fraction n.a. 

Extinguisher system manufacturer n.a. 

Evidence of halon distribution characteristics (from 

certification tests)—design concentration required for 

extinguishment 

7 percent - Halon concentration within the crew compartment 

probably varies by a factor of at least two. 

Range of expected operating temperatures for the 

bottle and the plumbing (oC (oF)) 

Any system in a vehicle must survive –45 oC (-49 oF). The system 

must function properly at –32 oC (-26 oF)and above. The bottles are 

all in the crew compartment, and thus are not exposed to the high 

temperatures associated with engine compartments. The maximum 

temperature to which the bottles will be exposed is approximately 63 

oC (145 oF). 

n.a. – not available

3.4.1.3.2 System Schematic 

 Figure 4 displays the fire suppression system configuration for the M2, M3 Bradley 

Fighting Vehicles. 

Figure 4. M2, M3 Bradley Fighting Vehicles Fire Extinguishing System Schematic 
48

3.4.1.3.3 Sequence of Events 

 As above, fires are detected automatically through the use of discriminating dual-band 

infrared sensors. When a mine penetrates the crew compartment and ruptures the main fuel cell, 

a large quantity of fuel (liquid, droplets, mist, and vapor) will be ejected from the tank and into 

the crew compartment. Both hot metal spall and remnants of the explosive fireball will act as 

ignition sources, igniting the fuel. The discriminating sensors will sense the initial event, but 

then delay activation of the halon fire suppression system for approximately 5 ms until the 

system is certain that there is truly a fire. The initial event is so large that closed hatches or the 

ramp may be blown open. The halon that is released may be entrained in the fire plume exiting 

the hatch openings. There is a danger that the halon can be swept out of the vehicle before 

achieving fire suppression. This is an absolutely worst-case scenario. Most events in which an 

antivehicle mine would attack a Bradley would not produce as large an initial event as described 

above. It is expected that in most cases the crew compartment halon system will be able to 

extinguish fires caused by land mines within the 250 ms time frame. Since most air-attack 

weapons are not nearly as strong as large land mines, it is expected that the halon system in the 

crew compartment will be able to extinguish resulting fires within the accepted time frame. 

3.4.2 Aircraft halon 1301 System Configurations 

3.4.2.1 C-130 System Configuration Description 

3.4.2.1.1 System Configuration Description 

 The C-130 fire extinguisher system provides fire protection for each of the four engines 

and the auxiliary power unit. For fire protection, the C-130 utilizes three halons (1301, 1011, 

and 1202) onboard. The distribution system for the halon 1202 engine system is significantly 

different than the halon 1301 system. The high rate discharge (HRD) halon 1301 system utilizes 

open-end nozzles and relies on the high velocity of the agent discharge for proper dispersal 

within the nacelle. Consequently, high vapor pressure agents such as halon 1301 are best suited 

for HRD applications. In contrast, the conventional system utilizes perforated tubing for agent 

distribution with consequent penalties of restricted flow and general high total system weight. A 

low vapor pressure agents such as halon 1011 are best suited for the latter application. Halon 

1202, an intermediate volatility extinguishant, has been used successfully in both types of 

systems. The C-130 has long and unique distribution system runs since the bottles are housed 

under the left wing and distribution lines must be routed from the bottles to the left engines on 

the left side wing, plus they must pass through the fuselage to the engines on the right wing. [5] 

The agent is contained in two bottles and the capacities of the bottles depend upon the agent 

(1011 – 9 kg (20 lb), 1202 – 9 kg (20 lb), 1301 – 10 kg (22 lb)). Each bottle is marked to 

identify the type of agent it contains. The bottles are discharged one at a time, and the agent is 

directed to any one of the engines or auxiliary power unit. The outlets for the agent are 

perforated tubing. Two rings encircle each engine, and a single tube is located above the 

auxiliary power unit. The controls for the system are located on the fire emergency panel on the 

pilot’s overhead pane. Specific C-130 fire system details are in Table 11. 
49

Table 11. C-130 Fire Suppression System Configuration. 

 C-130 (Halon 1011) C-130 (Halon 1202) C-130 (halon 1301) 

Engine Bay APU Engine Bay APU Engine Bay APU 

GENERIC 

Number of aircraft Active force, 300; ANG, 80E's and 166Hs; reserve 140 

Service cycle refill (years) 5 5 5 

Fire types (pool fires, mist...) Spray/pool Spray/pool Spray/pool 

Estimated halon use/year/aircraft 

(kg (lb)) 

39 

FIRE ZONE 

# of fire zones 2 2 2 

Fire Zone size (L, W, D) (cm, cm, 

cm (in, in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Fire zone volume (cm3 (in3)) n.a. n.a. n.a. n.a. n.a. n.a. 

Fire zone free volume (m3 (ft3)) 1.9 (66) 1.9 (66) 1.9 (66) 1.9 (66) 1.9 (66) 1.9 (66) 

EXTINGUISHANT Usually, C-130s are shipped with Halon 1011. After this is expelled, they are refilled with either 

Halon 1202 or for newer models/versions halon 1301. 

# of halon systems 2 2 2 

Extinguisher trigger mode Pilot activated Pilot 

activated 

Pilot activated Pilot 

activated 

Pilot activated Pilot activated 

Extinguisher volume (cm3 (in3)) 8800 (536) 8800 (536) 8800 (536) 8800 (536) 15,500 (945) 15,500 (945) 

Size of extinguishant container 

(cm, cm, cm (in, in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Storage compartment for 

extinguishant bottle (cm, cm, cm 

(in, in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Free volume in storage 

compartment (cm3

 (in3)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Normal charge and pressure of 

extinguisher container (MPa (psi)) 

4.1 (600) 

Max extinguisher container 

pressure (MPa (psi)) 

4.4 (640) (except on hot days where the pressure may exceed 6.9 MPa (1000 psi)) 

Extinguisher container percent 

filled (%) 

50 

Extinguisher container orientation 

(upright with valves at bottom...) 

Valves @ bottom 

Extinguisher container weight 

without Halon (kg (lb)) 

9 (20) 9 (20) 9 (20) 9 (20) 10 (22) 10 (22) 

Halon wt (kg (lb)) 8.6 (19) 8.6 (19) 8.6 (19) 8.6 (19) 8.6 (19) 8.6 (19) 

Extinguisher container location 

(inside/outside fire zone) 

Outside 

STRATEGY FOR USE 

 # of shots 2 2 2 2 2 2 

 Manual/automatic Manual, discharge one at a time 

 Procedure for activation Fire warning light is activated, pilot initiates firing of pyrotechnic squib which releases the 

contents of the bottle, the agent travels through the system plumbing to the engine nacelle/APU 

and is discharged as a gas. 

 Time to release halon 1301 10 seconds 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method Manifold 

Extinguisher discharge rate 

(lb/min) 

The contents of the bottle are discharged in less than 10 seconds. 

Distribution system plumbing The distribution system is complex. The bottles are stored under the left wing. The plumbing is 

routed to the left engine and through the aircraft to the right engine. There would involve a 

significant effort to redesign the plumbing system. The system was designed for a liquid agent 

(such as Halons 1011, 1211, and 1202) and not for a gaseous agent (halon 1301). The optimal 

design for a halon 1301 system would require short plumbing runs and larger diameter tubing. 

However, the distribution system for the C-130 utilizes long runs and a smaller diameter tubing 

(for optimization of the liquid agents utilized). 

 Inner diameter (cm (in)_ n.a. n.a. n.a. n.a. n.a. n.a. 
50

 C-130 (Halon 1011) C-130 (Halon 1202) C-130 (halon 1301) 

Engine Bay APU Engine Bay APU Engine Bay APU 

 Length (m (ft)) 24-27 (80-90) n.a. 24-27 (80-90) n.a. 24-27 (80-90) n.a. 

 Shape (bends, elbows) n.a. n.a. n.a. n.a. n.a. n.a. 

# and nature of nozzles/pipe 

terminations 

Outlets for agent are 

perforated tubing. Tubing is 

scattered throughout the each 

engine compartment, a single 

tube is located above APU. 

Outlets for agent are 

perforated tubing. Tubing is 

scattered throughout the each 

engine compartment, a single 

tube is located above APU. 

Outlets for agent are perforated 

tubing. Tubing is scattered 

throughout the each engine 

compartment, a single tube is 

located above APU. Normal 

halon 1301 systems have pipe 

terminations discharging into 

engine compartment. However, 

this system was not designed 

that way and the agent amount 

was increase to compensate. 

MODIFICATION POTENTIAL 

Potential for increased number or 

increased size of storage bottles 

The exact reasoning for storage of the bottles under the left wing is unknown in the original 

design. However, this design has been maintained for subsequent aircraft modifications. There is 

room for larger bottle. The fixtures, which support these bottles, would need to be redesigned. 

There may not be room for the addition of more bottles. The potential might exist to store 

additional bottles on the other side of the aircraft. The optimal solution would allow for 1 bottle to 

be assigned to each engine. 

Restriction on alternative fluids 

(very/modestly/slightly) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Access of current distribution 

plumbing for retrofit (Please rate 

with percent of ease (e.g., 0%-very 

difficult, 50%-relatively easy, 100 

percent easy).) 

Open access doors on 

nacelle/APU 

Open access doors on 

nacelle/APU 

Open access doors on 

nacelle/APU 

Access & available space for 

additional distribution plumbing or 

nozzle modification (Please rate 

with percent of ease (e.g., 0%-very 

difficult, 50%-relatively easy, 100 

percent easy).) 

n.a. n.a. n.a. n.a. n.a. n.a. 

How tight is the bottle space? n.a. n.a. n.a. n.a. n.a. n.a. 

Is the plumbing readily accessible 

for replacement? 

n.a. n.a. n.a. n.a. n.a. n.a. 

Is the plumbing readily accessible 

for adding another distribution 

part? 

n.a. n.a. n.a. n.a. n.a. n.a. 

Is the plumbing readily accessible 

for changing the pipe end? 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher Growth Potential 200% 200% 200% 200% 200% 200% 

OTHER 

Suppression success fraction 

Extinguisher system manufacturer Walter Kidde Walter 

Kidde 

Walter Kidde Walter 

Kidde 

Walter Kidde Walter Kidde 

Evidence of halon distribution 

characteristics (from certification 

tests)—design concentration 

required for extinguishment 

n.a. n.a. n.a. n.a. n.a. n.a. 

Range of expected operating 

temperatures for the bottle and the 

plumbing (°C (°F)) 

-54 to 71 

(-65 to 160) 

-54 to 71 

(-65 to 

160) 

-54 to 71 

(-65 to 160) 

-54 to 71 

(-65 to 

160) 

-54 to 71 

(-65 to 160) 

-54 to 71 

(-65 to 160) 

n.a. – not available

3.4.2.1.2 System Schematic 

 The C-130 utilizes three halons (1301, 1011, and 1202) onboard. The distribution system 

for the halon 1202 engine system is significantly different than the halon 1301 system. The 
51

C-130 has long and unique distribution system runs since the bottles are housed under the left 

wing and distribution lines must be routed from the bottles to the left engines on the left side 

wing, plus they must pass through the fuselage to the engines on the right wing. [5] Figure 5 

displays the fire suppression system configuration for the C-130 [34]. 

Figure 5. C-130 Fire Extinguishing System Schematic. 

3.4.2.1.3 Sequence of Events 

 The storage containers (or “bottles”) of fire extinguishant for engine fire protection 

systems are typically remotely located from the engine nacelle (although not always)--sometimes 
52

up to 15.2 m or 18.3 m (50 or 60 feet) away from the engine nacelle itself. The first step in such 

cases is to shut down the engine, when the proximity fire detector confirms a fire is present and 

the pilot is satisfied that a true fire event has occurred. The bottle is typically activated, at the 

initiation of the pilot, by the firing of a pyrotechnic squib that severs a rupture disk and releases 

the contents of the bottle. The extinguishant must then travel some distance through a series of 

pipes to the nacelle in question. A bottle may be plumbed to more than one engine nacelle, and 

some configurations will cross-feed two different bottles to the same two nacelles to provide 

“two-shot” protection to the nacelle needing extinguishment. Typically, APU systems are 

plumbed from the engine nacelle systems. Once the extinguishant reaches the nacelle, it 

discharges as a fluid either at one or more remote locations in the nacelle (for high volatility 

extinguishants such as halon 1301) or through a series of perforated holes in a complex network 

of distribution tubing within the nacelle (such as with low volatility extinguishants halon 1202, 

1211, and 1011). [12] In most cases, the fluid exits as a two-phase fluid (in the same distribution 

pipe), then flashes. The momentum allows the extinguishant to fill the "nooks and crannies" of 

the fire zone. 

3.4.2.2 F/A-18 C/D 

3.4.2.2.1 System Configuration Description 

 The approach to fire protection in F-18 aircraft consists of a single-bottle fixed halon 

1301 fire suppression system designed to provide fire protection for the left and right engines 

and the left and right airframe mounted accessory drive (AMAD) bays. A potential for false 

discharges exists on the ground. [19] Specific F/A-18 fire system details are in Table 12. 

Table 12. F-18C/D Fire Suppression System Configuration. 

F-18C/D 

Engine Bay APU 

GENERIC 

Number of aircraft 1001 

Service cycle refill (years) 5 

Fire types (pool fires, mist...) Spray/pool 

Estimated halon use/year/aircraft (kg (lb)) n.a. 

FIRE ZONE 

# of fire zones 3 (2 engines/AMAD, 1 APU) 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) n.a. n.a. 

Fire zone volume (cm3 (in3)) n.a. n.a. 

Fire zone free volume (m3 (ft3)) 1.14 (40.4) n.a. 

EXTINGUISHANT 

# of halon systems 1 

Extinguisher trigger mode Pilot activated 

Extinguisher volume (cm3 (in3)) 3031 (185) 

Size of extinguishant container (cm, cm, cm (in, in, in)) 11.4 cm (4.5 in.) dia, 46 cm (18 in.) long; 

cylindrical 

Storage compartment for extinguishant bottle (cm, cm, cm (in, in, in)) see 

drawing 

206 x 12.7 x 20.3 (81 x 5 x 8) 

Free volume in storage compartment (m3 (in3)) see drawing 0.048 (2953) 

Normal charge and pressure of extinguisher container (MPa (psi)) 4.3 (625) @ 22.2 °C (72 °F) 

Max extinguisher container pressure (MPa (psi)) 6.2 (900) @ 16 °C (60 °F) 

Extinguisher container percent filled (%) 50 

Extinguisher container orientation (upright with valves at bottom...) Lateral configuration 
53

F-18C/D 

Engine Bay APU 

Extinguisher container weight (kg (lb)) without Halon 2.7 (~6 lb) 

Halon wt (kg (lb)) 2.5 (5.5) 

Extinguisher container location (inside/outside fire zone) Outside 

STRATEGY FOR USE 

 # of shots 1 shot discharges into engine nacelle and 

AMAD bay or APU. 

 Manual/automatic Manual 

 Procedure for Activation Fire warning light is activated, pilot initiates 

firing of pyrotechnic squib which releases the 

contents of the bottle, the agent travels 

through the system plumbing to the engine 

nacelle/APU and is discharged as a gas. 

 Time to release halon 1301 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method Cut off pipe Cut off pipe 

Extinguisher discharge rate (kg/sec (lb/s)) 0.99 (2.2) 

Distribution system plumbing Single pipe discharged into engine and 

AMAD simultaneously. APU has discharge 

port, but the first fire occurrence in either the 

engine/AMAD or APU bays will utilize all 

Halon 

 Inner diameter (cm (in)) see drawings: none given n.a. n.a. 

 Length (cm (in)) see drawings: none given n.a. n.a. 

 Shape (bends, elbows) see drawings: nothing specific given n.a. n.a. 

# and nature of nozzles/pipe terminations cut off pipe cut off pipe 

MODIFICATION POTENTIAL 

Potential for increased number of increased size of storage bottles. n.a. n.a. 

Restriction on alternative fluids (very/modestly/slightly) modestly modestly 

Access of current distribution plumbing for retrofit (Please rate with 

percent of ease (e.g., 0%-very difficult, 50%-relatively easy, 100 percent 

easy).) 

20% 20% 

Access & available space for additional distribution plumbing or nozzle 

modification (Please rate with percent of ease (e.g., 0%-very difficult, 

50%-relatively easy, 100 percent easy).) 

20% 20% 

How tight is the bottle space? Only 12.7 cm (5 in.) in height available for 

growth. 

Is the plumbing readily accessible for replacement? n.a. n.a. 

Is the plumbing readily accessible for adding another distribution part? n.a. n.a. 

Is the plumbing readily accessible for changing the pipe end? n.a. n.a. 

Extinguisher Bottle Growth Potential 12.7 cm (5 in.) in height 

OTHER 

Suppression success fraction Historical reports show 80 percent success. 

Extinguisher system manufacturer Pacific Scientific 

Evidence of halon distribution characteristics (from certification tests) Yes Yes 

Range of expected operating temperatures for the bottle and the plumbing 

(°C (°F)) 

-54 to 71 (-65 to 600) -54 to 71 (-65 to 

600) 

n.a. – not available

3.4.2.2.2 System Schematic 

 Figure 6 through Figure 8 display the fire suppression system configuration for the F18C/D [35]. 
54

F/A-18 C/D FIREXX BOTTLE

INSTALLATION 

REFER TO STRUCTURE DWG

74A332000 SH 17 REV AG 

Figure 6. F/A-18C/D FIREXX Bottle Installation.
55

Figure 7. F/A-18C/D Halon Bottle And Discharge Piping Installations Bottom View. 
56

Figure 8. Halon Bottle and Discharge Piping Installations Side View. 
57

3.4.2.2.3 Sequence of Events 

 The storage containers (or “bottles”) of fire extinguishant for engine fire protection 

systems are typically remotely located from the engine nacelle (although not always)--sometimes 

up to 15.2 m or 18.3 m (50 or 60 feet) away from the engine nacelle itself. The first step in such 

cases is to shut down the engine, when the proximity fire detector confirms a fire is present and 

the pilot is satisfied that a true fire event has occurred. The bottle is typically activated, at the 

initiation of the pilot, by the firing of a pyrotechnic squib that severs a rupture disk and releases 

the contents of the bottle. The extinguishant must then travel some distance through a series of 

pipes to the nacelle in question. A bottle may be plumbed to more than one engine nacelle, and 

some configurations will cross-feed two different bottles to the same two nacelles to provide 

“two-shot” protection to the nacelle needing extinguishment. Typically, APU systems are 

plumbed from the engine nacelle systems. Once the extinguishant reaches the nacelle, it 

discharges as a fluid either at one or more remote locations in the nacelle (for high volatility 

extinguishants such as halon 1301) or through a series of perforated holes in a complex network 

of distribution tubing within the nacelle (such as with low volatility extinguishants halon 1202, 

1211, and 1011). [12] In most cases, the fluid exits as a two-phase fluid (in the same distribution 

pipe), then flashes. The momentum allows the extinguishant to fill the "nooks and crannies" of 

the fire zone. 

3.4.2.3 C-17 

3.4.2.3.1 System Configuration Description 

 Fire extinguishing is provided for all four engines (with four 9.5 kg (21 lb) bottles) and 

for the APU compartment (with one 1.13 kg (2.5 lb) bottle). Pulling out the applicable handle 

assembly on the glareshield panel discharges the agent from the extinguishers. The engine fire 

extinguisher system distribution lines on each wing are routed so the agent from each 

extinguisher can be discharged to either or both engines. Fire extinguishing is provided for the 

APU by a fixed halon 1301 high rate discharge fire extinguishing system in the APU 

compartment. Specific C-17 fire system details are in Table 13. 

Table 13. C-17 Fire Suppression System Configuration. 

C-17 

Engine Bay APU 

GENERIC 

Number of aircraft 23 

Service cycle refill (years) n.a. 

Fire types (pool fires, mist...) Spray/pool 

Estimated halon use/year/aircraft (kg (lb)) n.a. n.a. 

FIRE ZONE 

# of fire zones 2 1 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) n.a. n.a. 

Fire zone volume (m3 (ft3)) n.a. n.a. 

Fire zone free volume (m3 (ft3)) (net volume) 7.45 (263) 0.623 (22) 

EXTINGUISHANT 

# of halon systems 2 1 

Extinguisher trigger mode Remote Remote 

Extinguisher volume (cm3 (in3)) 10,300 (630) 1400 (86) 
58

C-17 

Size of extinguishant container (cm, cm, cm (in, in, in)) 27.7 (10.9 in.) diameter 14.2 (5.6 in.) diameter 

Storage compartment for extinguishant bottle (m3 (ft3)) 0.42 (15) 

Free volume in storage compartment (cm3 (in3)) 0.43 (260) 

Normal charge and pressure of extinguisher container 

(MPa (psig)) (@ 21 °C (70 °F)) with GN2) 

5.6 (800) 4.24 (600) 

Max extinguisher container pressure (MPa (psig)) 

(Burst range of safety disc) 

13.2 – 15.6 

(1900-2300) @ 96 °C (205 °F) 

11.96 – 13.3 

(1720-1920) 

Extinguisher container percent filled (%) 67% 69% 

Extinguisher container orientation (upright with valves 

at bottom...) 

Valves at bottom 

Extinguisher container weight (kg (lb)) without Halon 5.8 (12.8) 1.5 (3.2) 

Halon wt (kg (lb)) 9.5 (21.0) 1.1 (2.5) 

Extinguisher container location (inside/outside fire 

zone) 

Outside 

STRATEGY FOR USE 

 # of shots 2 1 

 Manual/automatic Manual Manual 

 Procedure for Activation Fire warning light is activated, pilot initiates firing of pyrotechnic 

squib which releases the contents of the bottle, the agent travels 

through the system plumbing to the engine nacelle/APU and is 

discharged as a gas. 

 Time to release halon 1301 n.a. n.a. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method (@ 21 °C (70 °F)) 5.6 MPa (Gas N2 @ 800 psig) 4.24 MPa (Gas N2 at 600 psig) 

Extinguisher discharge rate (kg/min (lb/min)) (95 

percent in 0.9 seconds) 

544 (1200) 72 (158) 

Distribution system plumbing Bottle to pylon stub: 6061ALT6; 

all else: CRES. 

CRES 321 

Inner diameter (cm (in)) From bottle to pylon stub, 3.8 

(1.5) ID; all else, 3.8 (1.5), 2.5 

(1.0), and 1.9 (0.75) ID. Wall 

thickness, 0.24 (0.095) 

1.27 (0.5) ID. Wall thickness, 

0.071 (0 .028) 

 Length (cm (in)) 99.4 (39.14) from outboard bottle 

to both outlets in core 

compartments; 41.7 (16.42); from 

outboard bottle to inboard pylon 

Straight length – 12.7 (5) – 

78.7 (31) 

 Shape (bends, elbows) 1 bend, 1.5 radius 

# and nature of nozzles/pipe terminations Two nozzles (1.91 (0.75)) One nozzle (1.27 (0.5)) 

MODIFICATION POTENTIAL 

Potential for increased number of increased size of 

storage bottles. 

n.a. n.a. 

Restriction on alternative fluids 

(very/modestly/slightly) 

slightly slightly 

Access of current distribution plumbing for retrofit 

(Please rate with percent of ease (e.g., 0%-very 

difficult, 50%-relatively easy, 100 percent easy).) 

30 percent difficult; 70 percent 

easy. 

30 percent difficult; 70 percent 

easy. 

Access & available space for additional distribution 

plumbing or nozzle modification (Please rate with 

percent of ease (e.g., 0%-very difficult, 50%-relatively 

easy, 100 percent easy).) 

30 percent difficult; 70 percent 

easy. 

30 percent difficult; 70 percent 

easy. 

How tight is the bottle space? n.a. n.a. 

Is the plumbing readily accessible for replacement? n.a. n.a. 

Is the plumbing readily accessible for adding another 

distribution part? 

n.a. n.a. 

Is the plumbing readily accessible for changing the 

pipe end? 

n.a. n.a. 

Extinguisher Bottle Growth Potential n.a. n.a. 

OTHER 

Suppression success fraction n.a. 
59

C-17 

Extinguisher system manufacturer Walter Kidde 

Evidence of halon distribution characteristics (from 

certification tests) 

6 percent by volume for 5.5 

seconds at cruising condition. 

6 percent by volume for 5.5 

seconds at cruising condition. 

Range of expected operating temperatures for the bottle 

and the plumbing (°C (°F)) 

-60 to 93 (-77 to 200) -60 to 93 (-77 to 200) 

MISCELLANEOUS 130 kPa (4 psig) is max pressure the protected volume can accept in 

nacelle. Max pressure in plumbing is 14 kPa (2000 psi) allowable. 

Potential fuels: Jet A and JP-8, Hydraulic Fluid MIL -H-83282, 

Lube Oil MIL-L-23699. 

n.a. – not available

3.4.2.3.2 System Schematic 

 Figure 9 displays the fire suppression system configuration for the C-17 [36]. 

Figure 9. C-17 Fire Extinguishing System Schematic (86 in3

). 
60

3.4.2.3.3 Sequence of Events 

 The storage containers (or “bottles”) of fire extinguishant for engine fire protection 

systems are typically remotely located from the engine nacelle (although not always)--sometimes 

up to 15.2 m or 18.3 m (50 or 60 feet) away from the engine nacelle itself. The first step in such 

cases is to shut down the engine, when the proximity fire detector confirms a fire is present and 

the pilot is satisfied that a true fire event has occurred. The bottle is typically activated, at the 

initiation of the pilot, by the firing of a pyrotechnic squib that severs a rupture disk and releases 

the contents of the bottle. The extinguishant must then travel some distance through a series of 

pipes to the nacelle in question. A bottle may be plumbed to more than one engine nacelle, and 

some configurations will cross-feed two different bottles to the same two nacelles to provide 

“two-shot” protection to the nacelle needing extinguishment. Typically, APU systems are 

plumbed from the engine nacelle systems. Once the extinguishant reaches the nacelle, it 

discharges as a fluid either at one or more remote locations in the nacelle (for high volatility 

extinguishants such as halon 1301) or through a series of perforated holes in a complex network 

of distribution tubing within the nacelle (such as with low volatility extinguishants halon 1202, 

1211, and 1011). [12] In most cases, the fluid exits as a two-phase fluid (in the same distribution 

pipe), then flashes. The momentum allows the extinguishant to fill the "nooks and crannies" of 

the fire zone. 

3.4.2.4 H-60 

3.4.2.4.1 System Configuration Description 

 Fire suppression for the H-60 aircraft consists of two halon 1301 bottles, which provide 

protection for both engines and the APU. The engine system halon bottles are configured to 

provide a "reserve capability.” for both engines and the APU. For the engines this means that the 

No. 2 engine bottle provides reserve fire protection capability for the No. 1 engine, and the No. 1 

engine bottle provides reserve fire protection capability for the No. 2 engine. For the APU, 

either bottle can be the primary bottle or the reserve bottle depending upon which bottle is first 

utilized. [21] Specific H-60 fire system details are in Table 14. 

Table 14. H-60 Fire Suppression System Configuration. 

H-60 

Engine Bay APU 

GENERIC 

Number of aircraft 1400 

Service cycle refill (years) 5 

Fire types (pool fires, mist...) Spray/pool Spray/pool 

Estimated halon use/year/aircraft (kg (lb)) n.a. n.a. 

FIRE ZONE 

# of fire zones 2 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) 132, 69, 56 (52, 27, 22) 36, 48, 38 

(14, 19, 15) 

Fire zone volume (m3 (ft3)) 0.54 (19) n.a. 

Fire zone free volume (m3 (ft3)) 0.28 (10.01) 4.5 E-2 (1.6) 

Fire zone maximum airflow rate (m3/min (CFM)) (1770) (1770) 

EXTINGUISHANT 

# of halon systems 1 1 
61

H-60 

Engine Bay APU 

Extinguisher trigger mode Pilot activated Pilot activated 

Extinguisher volume (cm3 (in3)) 1410 (86) 1410 (86) 

Size of extinguishant container (cm, cm, cm (in, in, in)) n.a. n.a. 

Storage compartment for extinguishant bottle (cm, cm, cm (in, in, in)) n.a. n.a. 

Free volume in storage compartment (cm3 (in3)) n.a. n.a. 

Normal charge and pressure of extinguisher container (kPa (psi)) 42.2 (600) 42.2 (600) 

Max extinguisher container pressure (kPa (psi)) n.a. n.a. 

Extinguisher container percent filled (%) 50 50 

Extinguisher container orientation (upright with valves at bottom...) upright with valves at bottom 

Extinguisher container weight (kg (lb)) without Halon n.a. n.a. 

Halon wt (kg (lb)) 1.13 (2.5) 1.13 (2.5) 

Extinguisher container location (inside/outside fire zone) outside Outside 

STRATEGY FOR USE 

 # of shots 2 

 Manual/automatic Manual Manual 

 Procedure for Activation Confirm fire, trigger No. 1 bottle, then can use 

No. 2 bottle 

 Time to release halon 1301 n.a. n.a. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method Manifold Manifold 

Extinguisher discharge rate (m3/min (CFM)) 0.105 (3.7) (3.7) 

Distribution system plumbing 

 Inner diameter (cm (in)) n.a. n.a. 

 Length (cm (in)) n.a. n.a. 

 Shape (bends, elbows) n.a. n.a. 

# and nature of nozzles/pipe terminations n.a. n.a. 

MODIFICATION POTENTIAL 

Potential for increased number of increased size of storage bottles. n.a. n.a. 

Restriction on alternative fluids (very/modestly/slightly) n.a. n.a. 

Access of current distribution plumbing for retrofit (Please rate with 

percent of ease (e.g., 0%-very difficult, 50%-relatively easy, 100 percent 

easy).) 

n.a. n.a. 

Access & available space for additional distribution plumbing or nozzle 

modification (Please rate with percent of ease (e.g., 0%-very difficult, 

50%-relatively easy, 100 percent easy).) 

n.a. n.a. 

How tight is the bottle space? n.a. n.a. 

Is the plumbing readily accessible for replacement? n.a. n.a. 

Is the plumbing readily accessible for adding another distribution part? n.a. n.a. 

Is the plumbing readily accessible for changing the pipe end? n.a. n.a. 

Extinguisher Bottle Growth Potential n.a. n.a. 

OTHER 

Suppression success fraction n.a. 

Extinguisher system manufacturer Walter Kidde Walter Kidde 

Evidence of halon distribution characteristics (from certification tests) 

Range of expected operating temperatures for the bottle and the plumbing 

(°C (°F)) 

-54 to 177 (-65 to 350) -54 to 177 (-65 to 

350) 

n.a. – not available

3.4.2.4.2 System Schematic 

 Figure 10 through Figure 12 display the fire suppression system configuration for the 

H-60 [37]. 
62

Figure 10. H-60 Fire Extinguishing Components Location. 

Figure 11. H-60 Engine Fire Extinguisher Installation. 
63

Figure 12. H-60 Engine Fire Extinguisher Installation. 

3.4.2.4.3 Sequence of Events 

 The storage bottles of fire extinguishant for engine fire protection systems are typically 

remotely located from the engine nacelle (although not always)--sometimes up to 15.2 m or 

18.3 m (50 or 60 feet) away from the engine nacelle itself. The first step in such cases is to shut 

down the engine, when the proximity fire detector confirms a fire is present and the pilot is 

satisfied that a true fire event has occurred. The bottle is typically activated, at the initiation of 

the pilot, by the firing of a pyrotechnic squib that severs a rupture disk and releases the contents 

of the bottle. The extinguishant must then travel some distance through a series of pipes to the 

nacelle in question. A bottle may be plumbed to more than one engine nacelle, and some 

configurations will cross-feed two different bottles to the same two nacelles to provide “twoshot” protection to the nacelle needing extinguishment. Typically, APU systems are plumbed 

from the engine nacelle systems. Once the extinguishant reaches the nacelle, it discharges as a 

fluid either at one or more remote locations in the nacelle (for high volatility extinguishants such 

as halon 1301) or through a series of perforated holes in a complex network of distribution 

tubing within the nacelle (such as with low volatility extinguishants halon 1202, 1211, and 

1011). [12] In most cases, the fluid exits as a two-phase fluid (in the same distribution pipe), 

then flashes. The momentum allows the extinguishant to fill the "nooks and crannies" of the fire 

zone. 
64

3.4.2.5 CH-47 

3.4.2.5.1 System Configuration Description 

 Fire suppression for the CH-47 aircraft consists of two halon 1301 bottles, which provide 

dual-shot protection for both engines similar to the reserve capability of the H-60. Specific 

CH-47 fire system details are in Table 15. 

Table 15. CH-47 Fire Suppression System Configuration. 

CH-47 

Engine Bay 

GENERIC 

Number of aircraft 463 (AF); 398 (USA) 

Service cycle refill (years) n.a. 

Fire types (pool fires, mist...) Spray/pool 

Estimated halon use/year/aircraft (kg (lb)) n.a. 

FIRE ZONE 

# of fire zones 2 (1 under each engine) 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) 99, 56, 66 (39, 22 ,26) 

Fire zone volume (m3 (ft3)) 0.37 (13) 

Fire zone free volume (m3 (ft3)) 0.34 (12) 

Fire zone operating temperature range (°C (°F)) -17 to 149 (0 to 300) 

Fire zone length/effective diameter ratio (m (ft)) 15.24 (50) 

EXTINGUISHANT 

# of halon systems 2 

Extinguisher trigger mode Pilot activated 

Extinguisher volume (cm3 (in3)) 62 (86) 

Size of extinguishant container (cm, cm, cm (in, in, in)) Spherical with 12.7 cm (5.5 in diameter bottle (2 containers) 

Storage compartment for extinguishant bottle (cm, cm, cm 

(in, in, in)) 

Not really stored in a compartment. Bottle is between fuselage 

and APU. 

Free volume in storage compartment (m3 (ft3)) 0.028 (1) 

Normal charge and pressure of extinguisher container (MPa 

(psi)) 

4.1 (600) 

Max extinguisher container pressure (MPa (psi)) 4.1 (600) 

Extinguisher container percent filled (%) 50 

Extinguisher container orientation (upright with valves at 

bottom...) 

Valves at bottom and to the side 

Extinguisher container weight without halon (kg (lb)) 1.81 (4) 

Halon wt (kg (lb)) 1.36 (3) 

Extinguisher container location (inside/outside fire zone) Outside (located at stations 482 and 502) 

STRATEGY FOR USE 

 # of shots 2 (can blow both bottles on either engine) 

 Manual/automatic Manual 

 Procedure for Activation See fire, detect with wire around engine, light in cockpit goes 

off, select bottle, select engine, pull "T" handle. 

 Time to release halon 1301 n.a. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method Nozzle 

Extinguisher discharge rate (m3/min (CFM)) 0.105 (3.7) 

Distribution system plumbing Very simple. 

 Inner diameter (cm (in)) Majority is 2.54 (1) (ID); goes to 0.952 (0.375); goes to 1.27 

(0.5) before it exits the nozzle. 

 Length (cm (in)) 160 (63) for each run 

 Shape (bends, elbows) Front bottle has 3 bends and 2 tees on the left and right side. 
65

CH-47 

Back bottle has 4 bends and 2 tees on the left and right side. 

# and nature of nozzles/pipe terminations 2 nozzles on each engine; fitted to fuselage bulkhead 

MODIFICATION POTENTIAL 

Potential for increased number of increased size of storage 

bottles. 

n.a. 

Restriction on alternative fluids (very/modestly/slightly) n.a. 

Access of current distribution plumbing for retrofit (Please 

rate with percent of ease (e.g., 0%-very difficult, 50%-

relatively easy, 100 percent easy).) 

n.a. 

Access & available space for additional distribution 

plumbing or nozzle modification (Please rate with percent 

of ease (e.g., 0%-very difficult, 50%-relatively easy, 100 

percent easy).) 

n.a. 

How tight is the bottle space? n.a. 

Is the plumbing readily accessible for replacement? n.a. 

Is the plumbing readily accessible for adding another 

distribution part? 

n.a. 

Is the plumbing readily accessible for changing the pipe 

end? 

n.a. 

Extinguisher Bottle Growth Potential n.a. 

OTHER n.a. 

Suppression success fraction n.a. 

Extinguisher system manufacturer Walter Kidde 

Evidence of halon distribution characteristics (from 

certification tests) 

114-FT-718-3 Report of Test Powerplant Fire Extinguishing 

System on CH-47C Helicopter, 1969 

D234-10090-3.5 APU Fire Extinguishing System Agent 

Concentration Test and Engine/APU Fire Detector System, 

1981 

Range of expected operating temperatures for the bottle and 

the plumbing (°C (°F)) 

149 (300) 

n.a. – not available

3.4.2.5.2 System Schematic 

 Figure 13 displays the fire suppression system configuration for the CH-47 [38]. 

3.4.2.5.3 Sequence of Events 

 The storage containers (or “bottles”) of fire extinguishant for engine fire protection 

systems are typically remotely located from the engine nacelle (although not always)--sometimes 

up to 15.2 m or 18.3 m (50 or 60 feet) away from the engine nacelle itself. The first step in such 

cases is to shut down the engine, when the proximity fire detector confirms a fire is present and 

the pilot is satisfied that a true fire event has occurred. The bottle is typically activated, at the 

initiation of the pilot, by the firing of a pyrotechnic squib that severs a rupture disk and releases 

the contents of the bottle. The extinguishant must then travel some distance through a series of 

pipes to the nacelle in question. A bottle may be plumbed to more than one engine nacelle, and 

some configurations will cross-feed two different bottles to the same two nacelles to provide 

“two-shot” protection to the nacelle needing extinguishment. Typically, APU systems are 

plumbed from the engine nacelle systems. Once the extinguishant reaches the nacelle, it 

discharges as a fluid either at one or more remote locations in the nacelle (for high volatility 

extinguishants such as halon 1301) or through a series of perforated holes in a complex network 

of distribution tubing within the nacelle (such as with low volatility extinguishants halon 1202, 

1211, and 1011). [12] In most cases, the fluid exits as a two-phase fluid (in the same distribution 
66

pipe), then flashes. The momentum allows the extinguishant to fill the "nooks and crannies" of 

the fire zone. 

Figure 13. CH-47 Fire Extinguishing System Schematic. 

3.4.2.6 F-16 

3.4.2.6.1 System Configuration Description 

 The halon reservoir is located in the left main wheel well. The reservoir stores thirteen 

pounds of liquid halon. The halon inerting system is set to ensure a nine percent halon by 

volume concentration, thereby providing a modest margin of safety. 

 The halon inerting, or fuel tank explosion suppression, system is controlled by the TANK 

INERTING switch on the cockpit fuel control panel. When the TANK INERTING switch is 

placed to TANK INERTING, the fuselage and internal wing tanks are placed on a reduced 

pressure schedule and a valve at the halon reservoir is opened. At each activation of the TANK 

INERTING switch, halon (if available) is released into the F1, A1, and internal wing tanks for 20 
67

seconds for initial inerting. After the 20 s of initial inerting, a small amount of pure halon will 

continue to flow into the wings. Thereafter, a continuous metered flow of halon is mixed with 

pressurization air to maintain the inert condition. The metered flow continues until the system is 

turned off or master power is turned off. Because of the limited halon supply, the system 

normally is activated after the external tanks have emptied, but before half of the internal fuel is 

depleted. The external tanks are not protected by the explosion suppression system. Specific 

F-16 fire system details are in Table 16. [24] 

Table 16. F-16 Fire Suppression System Configuration. 

F-16 

Fuel Cells 

GENERIC 

Number of aircraft Active force, 444; ANG, 305; reserve, 60 

Service cycle refill (years) n.a. 

Fire types (pool fires, mist...) Deflagration 

Estimated halon use/year/aircraft (kg (lb)) 12 

FIRE ZONE 

# of fire zones 1 

Fire Zone size (L, W, D) (cm, cm, cm (in, in, in)) n.a. 

Fire zone volume (cm3(in3)) 1966 (120) 

Fire zone free volume (cm3 (in3)) n.a. 

EXTINGUISHANT 

# of halon systems 1 

Extinguisher trigger mode n.a. 

Extinguisher volume (cm3 (in3)) 5200 – 5600 (315-340) 

Size of extinguishant container (cm, cm, cm (in, in, in)) n.a. 

Storage compartment for extinguishant bottle (cm, cm, cm 

(in, in, in)) 

n.a. 

Free volume in storage compartment(cm3 (in3)) n.a. 

Normal charge and pressure of extinguisher container (MPa 

(psi)) 

4.1 (600) 

Max extinguisher container pressure (MPa (psi)) 4.1 (600) 

Extinguisher container percent filled (%) n.a. 

Extinguisher container orientation (upright with valves at 

bottom...) 

Upright with valves at bottom 

Extinguisher container weight (kg (lb)) without Halon 2.5 (5.5) 

Halon wt (kg (lb)) 5.9 (13.0) 

Extinguisher container location (inside/outside fire zone) Outside 

STRATEGY FOR USE 

 # of shots Multiple 

 Manual/automatic Manual activation; automatic metering. 

 Procedure for Activation Pilot activated. 

 Time to release halon 1301 n.a. 

 How long does the halon last (with tank venting and fuel 

use)? It is not active when the plane is refueled in flight? 

Halon is released into F1, A1, and internal wing tanks for 20 

seconds for initial inerting. After 20 seconds, a small amount 

of pure halon will continue to flow into the wings. A 

continuous flow of halon is mixed with pressurization air to 

maintain the inert condition. The metered flow continues 

until the system is turned off or master power is turned off. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method n.a. 

Extinguisher discharge rate (kg/min (lb/min)) 0.91 (2) 

Distribution system plumbing 

 Inner diameter (cm (in)) 

 Length (cm (in)) 762 (300) 

 Shape (bends, elbows) From forward to aft fuselage fuel tanks and across to wing 
68

F-16 

tanks 

# and nature of nozzles/pipe terminations n.a. 

MODIFICATION POTENTIAL 

Potential for increased number of increased size of storage 

bottles. 

n.a. 

Restriction on alternative fluids (very/modestly/slightly) n.a. 

Access of current distribution plumbing for retrofit (Please 

rate with percent of ease (e.g., 0%-very difficult, 50%-

relatively easy, 100 percent easy).) 

Access to tubing would necessitate opening the fuel tanks 

Access & available space for additional distribution plumbing 

or nozzle modification (Please rate with percent of ease (e.g., 

0%-very difficult, 50%-relatively easy, 100 percent easy).) 

Access to tubing would necessitate opening the fuel tanks 

How tight is the bottle space? n.a. 

Is the plumbing readily accessible for replacement? n.a. 

Is the plumbing readily accessible for adding another 

distribution part? 

n.a. 

Is the plumbing readily accessible for changing the pipe end? n.a. 

Extinguisher Bottle Growth Potential 100% 

OTHER n.a. 

Suppression success fraction n.a. 

Extinguisher system manufacturer Walter Kidde 

Evidence of halon distribution characteristics (from 

certification tests) 

9 percent by volume 

Range of expected operating temperatures for the bottle and 

the plumbing (°C (°F)) 

-54 to 71 (-65 to 160) 

n.a. – not available

3.4.2.6.2 System Schematic 

 Figure 14 through Figure 16 illustrate the halon inerting system with the major system 

components identified along with a general depiction of the associated plumbing, electrical 

wiring and switches [24]. 

3.4.2.6.3 Sequence of Events 

 Halon inerting systems are activated prior to entering combat. The halon inerting, or fuel 

tank explosion suppression, system is controlled by the TANK INERTING switch on the cockpit 

fuel control panel. When the TANK INERTING switch is placed to TANK INERTING, the 

fuselage and internal wing tanks are placed on a reduced pressure schedule and a valve at the 

halon reservoir is opened. At each activation of the TANK INERTING switch, halon (if 

available) is released into the F1, A1, and internal wing tanks for 20 s for initial inerting. After 

the 20 s of initial inerting, a small amount of pure halon will continue to flow into the wings. 

Thereafter, a continuous metered flow of halon is mixed with pressurization air to maintain the 

inert condition. [24] 
69

Figure 14. F-16 Fuel Inerting System Schematic. 
70

Figure 15. Fuel Inerting Equipment. 
71

Figure 16. Halon Tank Assembly. 

3.4.3 Shipboard Machinery and Storage Spaces halon 1301 System Configurations 

3.4.3.1 DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer 

3.4.3.1.1 System Configuration Description 

 The DDG 51 is representative of the newer ships where halon 1301 was the suppression 

agent of choice during the design of the ship. The following compartments are protected by 

halon 1301: MMRs, AMRs, FLSRs, paint issue rooms, pump rooms, and generator room. There 

is enough space onboard to accommodate a two shot halon 1301 system for each MMR, AMR 

and generator room. Table 17 displays the breakdown of the DDG 51 (Arleigh Burke) Class: 

Aegis Guided Missile Destroyer halon 1301 systems including the spaces protected, number of 

cylinders, and number of shots. All halon 1301 shipboard systems are manually operated, both 

for occupied and unoccupied compartments. Detection device signal or occupied space sailor 

fire detection is followed by personnel assessment, evacuation, and system activation, as 

warranted. 

Table 17. DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer Halon 1301 

Systems. 

Spaces Protected Cylinders Size Halon Quantity Per System 

 (kg) (lb) (kg) (lb)

* Auxiliary Machinery Room 10 56.7 125 567 1250 

* Engine Room – 1 20 56.7 125 1134 2500 

* Engine Room – 2 22 56.7 125 1247 2750 

* Generator Room 6 43.1 95 258.5 570 

* Gas Turbine Module – 1A/B 2 43.1 95 86.2 190 

* Gas Turbine Module – 2A/B 2 43.1 95 86.2 190 

* Ship Service Gas Turbine 

Generator – 1 

2 43.1 95 86.2 190 

* Ship Service Gas Turbine 

Generator – 2 

2 43.1 95 86.2 190 

* Ship Service Gas Turbine 

Generator – 3 

2 43.1 95 86.2 190 

Flammable Liquid Storeroom 1 27.22 60 27.2 60 

Flammable Liquid Issue Room 2 6.8 15 13.6 30 

TACTAS room 2 56.7 125 113.4 250 

Quantity Halon Installed On Ship 3792 8,360 

On Board Spares 288 635 

Total Halon On Board 4080 8,995 

Notes: 

1. Spaces with asterisk (*) have “two shot” systems. 

2. All systems are “banked.” 

 Table 18 displays a description of the DDG 51 (Arleigh Burke) Class: Aegis Guided 

Missile Destroyer halon 1301 systems. 
72

Table 18. DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer Halon 1301 

System Description. 

Location Of Agent Cylinders 

Platform Space

Number Of 

Enclosures In 

Compartment 

Number Of 

Shots 

(halon 1301) 

Inside 

Compartment 

In Adjacent 

Compartment 

MMR 2 or 3 2 - Yes 

MMR Gas Turbine 

Enclosures 

- 2 - Yes 

AMR 1 2 Yes - 

AMR Enclosure - 2 - Yes 

Generator Room 1 1 Yes - 

Generator 

Enclosure 

- 2 - Yes 

DDG 51 

FLSRs, and other 

miscellaneous 

compartment 

- 1 Yes - 

 Table 19 displays the fire suppression system configuration for the DDG 51 (Arleigh 

Burke) Class: Aegis Guided Missile Destroyer. 

Table 19. DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer Fire Suppression 

System Configuration. 

 DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer 

 MMRs AMRs FLSRs Paint issue 

rooms 

Pump 

Rooms 

Generator 

Room 

GENERIC 

Number of vehicles Current number of ships/class = 16. Number of ships in class under construction = 37. 

Quantity of systems/ship = 12. Amount of halon/ship = 4080 kg (8,995 lb) Quantity of 

2-shot systems/ship = 9. 

Service cycle refill (years) n.a. n.a. n.a. n.a. n.a. n.a. 

Fire types (pool fires, mist...) FLSRs and Paint issue rooms: result from burning fuel cascading over highly obstructed 

and fuel loaded shelves and into flaming pools 

MMRs, AMRs, Engine Enclosures, and Generator Rooms: result from the ignition of a 

pressurized fuel (diesel/hydraulic or lubricating oil) leak or ignition of fuel soaked 

insulating material. Leaks onto hot surfaces result in three-dimensional spray fires with 

cascading liquid flow on complex surfaces and into flaming pools. 

Estimated halon use/year/vehicle 

(kg (lb)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

FIRE ZONE 

# of fire zones 6 

# of enclosures in the 

compartment 

2 or 3 1 -- -- -- 1 

Fire Zone size (L, W, D) (cm, cm, 

cm (in, in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Fire zone volume (cm3 (in3)) n.a. n.a. n.a. n.a. n.a. n.a. 

Fire zone free volume (m3 (ft3)) n.a. n.a. n.a. n.a. n.a. n.a. 

EXTINGUISHANT 
73

 DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer 

 MMRs AMRs FLSRs Paint issue 

rooms 

Pump 

Rooms 

Generator 

Room 

# of halon systems 12 

MMR: two shot halon system with the bottles in external manifold banks. LM2500 gas 

turbine enclosures have their own two shot system. AMR: two shot system, contains an 

engine enclosure and fuel delivery pipe. The enclosure is tight and halon protected. 

Enclosure protection is by a two shot system. Generator Room: It has a two shot 1301 

system. Contains an engine enclosure that is protected by a 2 shot system. Other: Other 

spaces are typically protected by single shot systems. 

Extinguisher trigger mode Manually activated 

Extinguisher volume (cm3 (in3)) n.a. n.a. n.a. n.a. n.a. n.a. 

Size of extinguishant container 

(cm, cm, cm (in, in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Storage compartment for 

extinguishant bottle (cm, cm, cm 

(in, in, in)) 

Systems built in at the time of ship construction are usually banked systems, where 

bottles are stored as a bank with a discharge manifold feeding nozzles throughout the 

space. 

Free volume in storage 

compartment (cm3

 (in3)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Normal charge and pressure of 

extinguisher container (MPa (psi)) 

4.13 MPa (600 psi) 

Max extinguisher container 

pressure (MPa (psi)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher container percent 

filled (%) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher container orientation 

(upright with valves at bottom...) 

Upright with valves at the top 

Extinguisher container weight 

without Halon (kg (lb)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Halon wt (kg (lb)) See Table 21 

Extinguisher container location 

(inside/outside fire zone) 

Outside 

(adjacent) 

Inside Inside -- -- Inside 

STRATEGY FOR USE 

 # of shots 2 2 1 -- -- 1 

 Manual/automatic Manual 

 Procedure for activation All halon 1301 shipboard systems are manually operated, both for occupied and 

unoccupied compartments. Detection device signal or occupied space sailor fire 

detection is followed by personnel assessment, evacuation, and system activation, as 

warranted. 

 Time to release halon 1301 Discharge time: 10 seconds maximum. All systems have a time delay (30 or 60 seconds) 

and a pre-discharge alarm to allow time for ventilation shut down and for personnel 

egress. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion method There is probably not significant excess capacity. Smaller systems may employ standard 

pipe sizes that would allow significant additional fluid to be discharged within the time 

specifications. 

Extinguisher discharge rate 

(kg/min (lb/min)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Distribution system plumbing 

inner diameter (cm (in)) 

Plumbing sizes vary from 2.54 cm (1 in.) to over 15.24 cm (6 in.) in diameter Schedule 

40 to Schedule 80 pipe depending on compartment size and bottle location. The larger 

systems have plumbing sized for the amount of agent to be discharged. 

Distribution system plumbing 

length (cm (in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Distribution system plumbing 

shape (bends, elbows) 

n.a. n.a. n.a. n.a. n.a. n.a. 

# and nature of nozzles/pipe 

terminations 

n.a. n.a. n.a. n.a. n.a. n.a. 

MODIFICATION POTENTIAL 
74

 DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer 

 MMRs AMRs FLSRs Paint issue 

rooms 

Pump 

Rooms 

Generator 

Room 

Potential for increased number or 

increased size of storage bottles 

MMR: The bank compartments are crowded with perhaps 10 percent additional capacity. 

It may be possible to add 50 percent capacity in the MMR itself via modular units. AMR: 

Retrofit space expansion of 100 percent may be feasible since suppression system can be 

down rated to a single shot. Generator Room: Some expansion space is available. Other: 

Several other small usage compartments exist and would need to be considered 

separately. These involve only one or two cylinders each. 

Restriction on alternative fluids 

(very/modestly/slightly) 

Temperature impacts concentration designs as delivered concentration depends on 

compartment temperature. Temperature, however, also impacts agent storage. For 

example, one consideration in selecting HFC-227ea over HFC-23 was that while the 

same or less weight of HFC-23 was required, its higher vapor pressure at elevated 

temperatures necessitated employing reduced cylinder fill densities. More cylinders 

would have been needed at significant increases in system space and weight. 

Access of current distribution 

plumbing for retrofit (Please rate 

with percent of ease (e.g., 20 

percent of the plumbing is 

difficult to access, 80 percent of 

the plumbing is easy to access.)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Access & available space for 

additional distribution plumbing 

or nozzle modification (Please 

rate with percent of ease (e.g., 20 

percent of the plumbing is 

difficult to access, 80 percent of 

the plumbing is easy to access.)) 

The DDG 51 is representative of the newer ships where halon 1301 was the suppression 

agent of choice during the design of the ship. Therefore, there is enough space onboard 

to accommodate a two shot halon 1301 system for each MMR, AMR and Generator 

Room. 

How tight is the bottle space? n.a. n.a. n.a. n.a. n.a. n.a. 

Is the plumbing readily accessible 

for replacement? 

Piping is generally accessible. 

Is the plumbing readily accessible 

for adding another distribution 

part? 

Additional nozzles could likely be added or nozzles changed particularly with a 

supplemental modular discharge system. 

Is the plumbing readily accessible 

for changing the pipe end? 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher Growth Potential MMR: perhaps 10 percent additional capacity or 50 percent capacity via modular units. 

AMR: expansion of 100 percent may be feasible. Generator Room: Some expansion 

space is available. Other: Several other small usage compartments exist and would need 

to be considered separately. 

OTHER 

Suppression success fraction n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher system manufacturer Either Kidde or Ansul. 

Evidence of halon distribution 

characteristics (from certification 

tests)—design concentration 

required for extinguishment 

Agent design concentration envelope: 5 percent at 10 °C (50 °F) to 7 percent at 66 °C 

(150 °F). Acceptance testing: in order for a system to be accepted, during ship 

commissioning, the average halon 1301 concentration in the compartment must be 

between 5 percent and 7 percent by volume. The minimum measured value must be 

above 4 percent. Agent measurements are taken at five to twelve locations depending on 

compartment type (MMR, AMR, generator room or other). 

Range of expected operating 

temperatures for the bottle and the 

plumbing (°C (°F)) 

The Navy shipboard operating temperature range for total flooding fire protection 

systems is 10 °C (50 °F) to 66 °C (150 °F). This temperature range covers both the 

compartments to be protected and the storage of the agent. 

n.a. – not available

3.4.3.1.2 System Schematic 

 Figure 17 displays the fire suppression system configuration for the DDG 51 (Arleigh 

Burke) Class: Aegis Guided Missile Destroyer. 
75

Figure 17. DDG 51 (Arleigh Burke) Class: Aegis Guided Missile Destroyer Fire 

Extinguishing System Schematic 

3.4.3.1.3 Sequence of Events 

 Time from fire initiation to agent discharge can vary considerably between occupied and 

unoccupied spaces. All activations are manual and occur after inspection and usually attempts at 

suppression with water, etc. are made. For occupied spaces, system activation may occur, if 

warranted, after situation assessment and compartment evacuation. This time interval can be as 

short as 30 seconds to one minute. For unoccupied spaces, the Damage Control Central will 

respond to a detector alarm, by sending a dispatcher to investigate the cause of the alarm. The 

elapsed time from the detector alarm initiation to discharge system activation will be a function 

of other ongoing activities in Damage Control Central, the availability of a dispatcher, and the 

proximity of the compartment to be investigated. The shortest times from detector response to 

suppression system activation are estimated at one and a half to two minutes. Table 20 provides 

a listing of the sequence of events. 
76

Table 20. System Activation/Sequence of Events. 

Event Event Initiation and/ or Duration (min:sec) 

Unmanned Compartment Manned Compartment 

Dampers are normally open/ fans are normally on 

Fire ignition Variable (prolonged ignition will yield a larger fire, initially) 

“Detection” High temperature and/or rate of rise detectors Manned 

Situation Assessment 

fire 

Damage Control Central responds to detector signal 

by sending dispatcher to identify threat 

On site personnel 

Egress - 0:30-1:00 

System Activation

Secure fan motors 

and close dampers (if 

present) 

0:30 - 1:00 (interlocked fan motors and dampers) 

Ventilation and Compartment leakage – Compartments protected by 1301 are equipped 

with ventilation interlocks. In the event of system activation, the ventilation fans are 

automatically turned off and ventilation dampers, when installed, are automatically shut. 

Discharge Agent 

3.4.3.2 LHD 1 (WASP) / LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft 

Carriers 

3.4.3.2.1 System Configuration Description 

 The LHDs can be separated into LHD-1 through LHD-4, and LHD-5. While LHD-5 

compartments are likely to have dampers in the ventilation ducts, the other ships probably do 

not. Table 21 and Table 22 display the breakdown of the LHA – 4 USS Nassau and the LHD – 3 

USS Kearsarge halon 1301 systems including the spaces protected, number of cylinders, and 

number of shots. All halon 1301 shipboard systems are manually operated, both for occupied 

and unoccupied compartments. Detection device signal or occupied space sailor fire detection is 

followed by personnel assessment, evacuation, and system activation, as warranted. 

Table 21. LHA – 4 USS Nassau Halon 1301 Systems. 

Space Cylinders Size Halon Quantity Per System 

 (kg) (lb) (kg) (lb)

Main Machinery Room #1 19 56.7 125 1077 2375 

Main Machinery Room #2 23 56.7 125 1304 2875 

Auxiliary Machinery Room 8 56.7 125 453.6 1000 

Emergency Diesel Generator Room #1 5 56.7 125 283.5 625 

Emergency Diesel Generator Room #2 3 56.7 125 170.1 375 

JP-5 Pump Room #1 2 56.7 125 113.4 250 

JP-5 Pump Room#2 1 56.7 125 56.7 125 

Fuel Pump Room 4 56.7 125 226.8 500 

Quantity halon installed on ship 3685 8,125 

On board spares 1474 3,250 

Total halon on board 5160 11,375 

1. All systems are “single shot”. 

2. All systems are “modular”. 

3. This arrangements (single shot, modular) is typical of ships that received Halon via backfit. 
77

Table 22. LHD – 3 USS Kearsarge Halon 1301 Systems. 

Space Cylinders Size Halon Quantity Per System 

 (kg) (lb) (kg) (lb)

Main Machinery Room #1 38 56.7 125 2155 4750 

Main Machinery Room #2 46 56.7 125 2608 5750 

Auxiliary Machinery Room 20 56.7 125 1134 2500 

Emergency Diesel Generator Room 

#1 

5 56.7 125 283.5 625 

Emergency Diesel Generator Room 

#2 

3 56.7 125 170.1 375 

JP-5 Pump Room #1 4 56.7 125 226.8 500 

JP-5 Pump Room#2 3 27.2 60 81.7 180 

LCAC Pump Room 3 27.2 60 81.7 180 

Paint Mix And Issue Room 1 43.1 95 43.1 95 

Cargo Flammable Liquid Room 6 56.7 125 340.2 750 

Aviation Flammable Storeroom 2 43.1 95 86.2 190 

Supply Department Flammable 

Liquid Storeroom 

4 27.2 60 108.9 240 

Ship Store Flammable Liquid 

Storeroom 

2 4.5 10 9.1 20 

Aviation Flammable Liquid Issue 

Room 

1 6.8 15 6.8 15 

Quantity halon installed on ship 7335 16,170 

On board spares 929.9 2,050 

Total halon on board 8264 18,220 

1. Spaces with asterisk (*) have “two shot” systems. 

2. All systems are “banked.” 

 
78

Table 23 displays a description of the LHD 1-4, LHD 5-7, and LHA halon 1301 systems. 

Table 23. LHD 1-4, LHD 5-7, and LHA halon 1301 halon 1301 System Description. 

Location Of Agent Cylinders 

Platform Space

Number Of 

Enclosures In 

Compartment 

Number Of 

Shots 

(halon 1301) 

Inside 

Compartment 

In Adjacent 

Compartment 

MMR - 2 Yes - 

AMR - 2 Yes - 

Emergency 

Generator Room 

- 1 Yes - 

Pump Room - 1 Yes - 

LHD 1-4 

FLSRs, and other 

miscellaneous 

compartment 

- 1 Yes - 

MMR - 2 - Yes 

AMR - 1 Yes - 

Emergency 

Generator Room 

- 1 Yes - 

LHD 5-7 

FLSRs, and other 

miscellaneous 

compartment 

- 1 Yes - 

MMR - 1 Yes - 

AMR - 1 Yes - 

Emergency 

Generator Room 

- 1 Yes - 

Pump Room - 1 Yes - 

LHA 

FLSR (CO2) - 1 Yes - 
79

 Table 24 displays the fire suppression system configuration for the LHD 1 (WASP) / 

LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft Carriers. 

Table 24. LHD 1 (WASP) / LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft 

Carriers Fire Suppression System Configuration. 

 LHD 1 (WASP) / LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft Carriers 

 MMR AMR FLSR Paint issue 

Rooms 

Pump 

Rooms 

Generator 

Room 

GENERIC 

Number of vehicles Current number of ships/class: LHA (5); LHD (4). Number of ships in class under 

construction: LHA (0); LHD (3). Quantity of systems/ship: LHA (8); LHD (14). Amount of 

halon/ship: LHA (5160 kg (11,375 lb)); LHD (8314 kg (18,330 lb)). Quantity of 2-shot 

systems/ship: LHD (3). LHA is a modular system. LHD is a banked system. 

Service cycle refill (years) n.a. n.a. n.a. n.a. n.a. n.a. 

Fire types (pool fires, 

mist...) 

FLSRs and Paint issue rooms: result from burning fuel cascading over highly obstructed and 

fuel loaded shelves and into flaming pools 

MMRs, AMRs, Engine Enclosures, and Generator Rooms: result from the ignition of a 

pressurized fuel (diesel/hydraulic or lubricating oil) leak or ignition of fuel soaked insulating 

material. Leaks onto hot surfaces result in three-dimensional spray fires with cascading liquid 

flow on complex surfaces and into flaming pools. 

Estimated halon 

use/year/vehicle (kg (lb)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

FIRE ZONE 

# of fire zones 6 

Fire Zone size (L, W, D) 

(cm, cm, cm (in, in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Fire zone volume (cm3

(in3

)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Fire zone free volume (m3

(ft3

)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

EXTINGUISHANT 

# of halon systems LHA-1 (8); LHD-1 (14) 

Extinguisher trigger mode Manually activated. 

Extinguisher volume (cm3

(in3

)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Size of extinguishant 

container (cm, cm, cm (in, 

in, in)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Storage compartment for 

extinguishant bottle (cm, 

cm, cm (in, in, in)) 

Systems built in at the time of ship construction are usually banked systems, where bottles are 

stored as a bank with a discharge manifold feeding nozzles throughout the space. LHA is a 

modular system. LHD is a banked system. 

Free volume in storage 

compartment (cm3

 (in3)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Normal charge and pressure 

of extinguisher container 

(MPa (psi)) 

4.13 MPa (600 psi) 

Max extinguisher container 

pressure (MPa (psi)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher container 

percent filled (%) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher container 

orientation (upright with 

valves at bottom...) 

Upright with valves at the top. 

Extinguisher container 

weight without Halon (kg 

(lb)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Halon wt (kg (lb)) See Tables 32 and 33. 
80

 LHD 1 (WASP) / LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft Carriers 

 MMR AMR FLSR Paint issue 

Rooms 

Pump 

Rooms 

Generator 

Room 

Extinguisher container 

location (inside/outside fire 

zone) 

Outside 

(adjacent) 

Inside Inside -- -- Inside 

STRATEGY FOR USE MMR: LHD 1 to LHD 4 have the halon cylinders in the MMR. LHD 5 has halon stored in 

dedicated compartments external to the MMR. Additional space in the MMR should be 

available onboard LHD 5-7. AMR: Early LHDs have two shot that were later down rated as 

requiring only single shot systems. LHD 1 - 4 have two shot halon systems. LHD 5-7 have a 

single shot system. The halon cylinders for all LHDs are stored inside the AMRs. LHAs 

have single shot systems with bottles inside the compartments. Emergency Generator Room: 

LHDs and LHAs have a single shot. The agent is stored inside the compartment. Other: Other 

spaces are typically protected by single shot systems. 

 # of shots LHD 1-4: MMR-2, AMR-2, Emergency Generator Room-1, Pump Room-1, FLSR-1 

LHD 5-7: MMR-2, AMR-1, Emergency Generator Room-1, FLSR-1 

LHA: MMR-1, AMR-1, Emergency Generator Room-1, Pump Room-1, FLSR (CO2)-1 

 Manual/automatic Manual 

 Procedure for activation All halon 1301 shipboard systems are manually operated, both for occupied and unoccupied 

compartments. Detection device signal or occupied space sailor fire detection is followed by 

personnel assessment, evacuation, and system activation, as warranted. 

 Time release halon 1301 Discharge time: 10 seconds maximum. All systems have a time delay (30 or 60 seconds) and 

a pre-discharge alarm to allow time for ventilation shut down and for personnel egress. 

DISTRIBUTION SYSTEM 

Extinguisher dispersion 

method 

Banked system – a discharge manifold feeds nozzles throughout the space. Modular system – 

cylinders are distributed throughout the space and centrally tripped by a pneumatic activation 

loop. 

Extinguisher discharge rate 

(kg/min (lb/min)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Distribution system 

plumbing Inner diameter 

(cm (in)) 

Plumbing sizes vary from 2.54 cm (1 in.) to over 15.24 cm (6 in.) diameter Schedule 40 to 

Schedule 80 pipe depending on compartment size and bottle location. The larger systems 

have plumbing sized for the amount of agent to be discharged. 

Distribution system 

plumbing Length (cm (in)) 

Distribution system 

plumbing Shape (bends, 

elbows) 

# and nature of nozzles/pipe 

terminations 

Refer to Figure 18. 

MODIFICATION 

POTENTIAL 

Potential for increased 

number or increased size of 

storage bottles 

MMR: LHD 1 - 4 will be the most difficult to retrofit because they have two shot systems in 

the MMRs hence there is little additional space for more agent. LHD 5 - 7 have the agent 

stored outside the MMRs, therefore there will available for a modular agent system in side the 

MMR where the agent used to previously be located (LHD 1 - 4). LHAs will also be difficult 

to retrofit because they contain the 1 shot suppression system in the MMRs. 

AMR: There is at least 100 percent space availability. Only a 1 shot protection is required. 

For LHD 1- 4 the second shot can be eliminated. 

Generator Room: For all LHDs and LHAs limited space may be available. 

Several other small usage compartments exist and would need to be considered separately. 

These involve only one or two cylinders each. 

Restriction on alternative 

fluids 

(very/modestly/slightly) 

Temperature impacts concentration designs as delivered concentration depends on 

compartment temperature. Temperature, however, also impacts agent storage. For example, 

one consideration in selecting HFC-227ea over HFC-23 was that while the same or less 

weight of HFC-23 was required, its higher vapor pressure at elevated temperatures 

necessitated employing reduced cylinder fill densities. More cylinders would have been 

needed at significant increases in system space and weight. 
81

 LHD 1 (WASP) / LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft Carriers 

 MMR AMR FLSR Paint issue 

Rooms 

Pump 

Rooms 

Generator 

Room 

Access of current 

distribution plumbing for 

retrofit (Please rate with 

percent of ease (e.g., 20 

percent of the plumbing is 

difficult to access, 80 

percent of the plumbing is 

easy to access.)) 

n.a. n.a. n.a. n.a. n.a. n.a. 

Access & available space 

for additional distribution 

plumbing or nozzle 

modification (Please rate 

with percent of ease (e.g., 

20 percent of the plumbing 

is difficult to access, 80 

percent of the plumbing is 

easy to access.)) 

There is probably not significant excess capacity. Smaller systems may employ standard pipe 

sizes that would allow significant additional fluid to be discharged within the time 

specifications. 

How tight is the bottle 

space? 

n.a. n.a. n.a. n.a. n.a. n.a. 

Is the plumbing readily 

accessible for replacement? 

Piping is generally accessible. 

Is the plumbing readily 

accessible for adding 

another distribution part? 

Additional nozzles could likely be added or nozzles changed particularly with a supplemental 

modular discharge system. 

Is the plumbing readily 

accessible for changing the 

pipe end? 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher Growth 

Potential 

LHD 1 - 4 MMRs – limited potential. LHD 5 - 7 MMRs have potential due to modular units. 

LHA MMRs – very difficult. AMR: 100 percent. Generator Room – limited space may be 

available. Several other small usage compartments exist and would need to be considered 

separately. 

OTHER 

Suppression success 

fraction 

n.a. n.a. n.a. n.a. n.a. n.a. 

Extinguisher system 

manufacturer 

Either Kidde or Ansul. 

Evidence of halon 

distribution characteristics 

(from certification tests)—

design concentration 

required for extinguishment 

Acceptance testing: in order for a system to be accepted, during ship commissioning, the 

average halon 1301 concentration in the compartment must be between 5 percent and 7 

percent by volume. The minimum measured value must be above 4 percent. Agent 

measurements are taken at five to twelve locations depending on compartment type (MMR, 

AMR, generator room or other). 

Range of expected 

operating temperatures for 

the bottle and the plumbing 

(°C (°F)) 

The Navy shipboard operating temperature range for total flooding fire protection systems is 

10 °C (50 °F) to 66 °C (150 °F). This temperature range covers both the compartments to be 

protected and the storage of the agent. 

n.a. – not available
82

3.4.3.2.2 System Schematic 

 Figure 18 displays the fire suppression system configuration for the LHD 1 

(WASP)/LHA 1 (Tarawa) Class: Amphibious Helo/Landing Craft Carriers. 

Figure 18. . LHD 1 (WASP) / LHA 1 (TARAWA) Class: Amphibious Helo/Landing Craft 

Carriers Fire Extinguishing System Schematic. 

3.4.3.2.3 Sequence of Events 

 Time from fire initiation to agent discharge can vary considerably between occupied and 

unoccupied spaces. All activations are manual and occur after inspection and usually attempts at 

suppression with water, etc. are made. For occupied spaces, system activation may occur, if 

warranted, after situation assessment and compartment evacuation. This time interval can be as 
83

short as 30 seconds to one minute. For unoccupied spaces, the Damage Control Central will 

respond to a detector alarm, by sending a dispatcher to investigate the cause of the alarm. The 

elapsed time from the detector alarm initiation to discharge system activation will be a function 

of other ongoing activities in Damage Control Central, the availability of a dispatcher, and the 

proximity of the compartment to be investigated. The shortest times from detector response to 

suppression system activation are estimated at one and a half to two minutes. Table 25 provides 

a listing of the sequence of events. 

Table 25. System Activation/ Sequence of Events. 

Event Event Initiation and/ or Duration (min:sec) 

Unmanned Compartment Manned Compartment 

Dampers are normally open/ fans are normally on 

Fire ignition Variable (prolonged ignition will yield a larger fire, initially) 

“Detection” High temperature and/or rate of rise detectors Manned 

Situation Assessment 

fire 

Damage Control Central responds to detector signal 

by sending dispatcher to identify threat 

On site personnel 

Egress - 0:30-1:00 

System Activation

Secure fan motors 

and close dampers (if 

present) 

0:30 - 1:00 (interlocked fan motors and dampers) 

Ventilation and Compartment leakage – Compartments protected by 1301 are equipped 

with ventilation interlocks. In the event of system activation, the ventilation fans are 

automatically turned off and ventilation dampers, when installed, are automatically shut. 

Discharge Agent 

4.0 Technical Problems 

 The technical problems associated with this effort related to data (combat, safety, and 

system configuration) acquisition. In characterizing the severity of fires addressed by these 

systems, it was necessary to consult the various combat databases. Unfortunately, combat data 

are not releasable. Also consulted were the safety centers of the various Services. However, 

sometimes safety center data may be incomplete and/or subjective. Numerous efforts were made 

to obtain complete system configuration data. Although substantial data were obtained, still data 

holes exist. 

5.0 Recommendations 

 Since the system configuration data are incomplete, it is recommended that this report be 

updated as future data are located. 

6.0 Conclusions 

 The goal of the Next Generation Fire Suppression Technology Program (NGP) is to 

develop and demonstrate retrofitable, economically feasible, environmentally-acceptable, and 

user-safe processes, techniques, and fluids that meet the operational requirements currently 

satisfied by halon 1301 systems in aircraft, ships, land combat vehicles, and critical mission 
84

support facilities. The results will be specifically applicable to fielded weapon systems, and will 

provide dual-use fire suppression technologies for preserving both life and operational assets. 

 Previous research, development, testing and evaluation have led to the identification of 

ways to provide halon-equivalent fire protection for some platforms. The remaining applications 

are fire suppression in: 

• Crew compartments of ground vehicles, 

• Dry bays in aircraft, 

• Engine nacelles in aircraft, 

• Storage compartments in aircraft and ships, and 

• Machinery spaces in ships. 

 In addition, halon 1301 is used to inert the ullage in some aircraft fuel tanks. 

 There are a large number of platforms that have halon 1301 fire suppression systems. 

Obtaining information on all of these would be difficult, costly, and unnecessary. Therefore, the 

Military Services identified a small subset of these platforms whose halon systems are 

representative of the range of fire suppression needs: 

• Ground vehicles: M992 (FAASV), M1 tank, and M2/M3 (BFSV) 

• Aircraft: C-130, F/A-18 C/D, C-17, H-60, CH-47, F-16 

• Ships: DDG 51, LHD 1/LHA 1, LCAC 

 This project accomplished the following: 

• Characterized and tabulated the nature, frequency, consequences (including personnel 

injuries), and severity of fires previously and currently attacked using halon 1301. 

• Derived a small set of representative (model) fires (using the analyses described 

above) for other elements in the Program. 

• Compiled characteristics and limitations of the systems that new fire suppression 

technologies will replace or into which they will be retrofitted. The descriptions of 

the environments of the current systems compiled during this program will serve as 

boundary conditions for the new technologies to be developed in subsequent 

Elements of the NGP. 

7.0 References 

1. “Next-Generation Fire Suppression Technology: Strategy for A National Program”, 

Department of Defense, Office of the Director, Defense Research and Engineering, July 

1996. 

2. SURVIAC-TR-93-010, "Alternatives for halon 1301 in Army Ground Vehicle 

Firefighting Systems", The SURVICE Engineering Company, July 1993. 
85

3. U.S. Army Research Laboratory, “Replacements for Halon Fire-Extinguishing Systems 

in Ground Combat Vehicles”, A.E. Finnerty, P.J. Peregino, and L.J. Vande Kieft, August 

1998. 

4. Air Mobility Command, Public Affairs, USAF Fact Sheet, August 2001, 

<http://www.af.mil/news/factsheets.html>. 

5. MIL-E-22285, Military Specification, Extinguishing System, Fire, Aircraft, High-RateDischarge Type, Installation and Test of, April 27, 1960. 

6. “F/A-18 Background Info”, Boeing, August 2001, <http://www.boeing.com/defensespace/military/fa18/fa18_4back.htm>. 

7. UH-60 Black Hawk, Sikorsky, August 2001, 

<http://www.sikorsky.com/details/1,,CLI1_DIV69_ETI561,00.html>. 

8. U.S. Naval Research Laboratory, “Model Fire for Evaluating Shipboard Halon 

Replacement Agents”, R.S. Sheinson, August 1998. 

9. “Halon Substitutes Program, Crew Compartment Program.” Aberdeen Test Center – Fire 

Protection / Fire Safety Testing: 3 pp. 9 August 2001. 

<http://www.atc.army.mil/brochures/fireprot/crew.shtml>. 

10. “Halon Substitutes Program, Facilities.” Aberdeen Test Center – Fire Protection / Fire 

Safety Testing: 5 pp. 9 August 2001. 

<http://www.atc.army.mil/brochures/fireprot/facilities.shtml>. 

11. “US Army Ground Vehicle Crew Compartment Halon Replacement Program”, S. 

McCormick and M. Clauson, US Army Tank-automotive and Armaments Command and 

H. Cross, US Army Aberdeen Test Center, Presented at the Halon Options Technical 

Working Conference, Albuquerque, NM, 2-4 May 2000. 

12. WL-TR-97-3066, SURVIAC-97-029, “Aircraft Engine/APU and Dry Bay Fire 

Extinguishing System Design Model (HFC-125)”, J.M. Bennett and M.V. Bennett, May 

1997. 

13. AFWAL-TR-87-3032, “Aircraft Dry Bay Fire Protection”, July 1987, Boeing Military 

Airplane Company, M.F. Robaidek, Final Report for period September 1983 – March 

1987. 

14. SURVIAC-TR-98-023, “F-22 Dry Bay Fire Suppression Testing”, Booz·Allen & 

Hamilton Inc., August 1998. 

15. The Fundamentals of Aircraft Combat Survivability Analysis and Design, Robert E. Ball, 

1985. 

16. WL-TR-95-3039, “Halon Replacement Program for Aviation, Dry Bay Application, 

Phase I – Operational Parameters Study”, September 1995. 

17. Memorandum From W. M. Moscrip To T.A. Simpson, 27 March, 1998, Aircraft Engine 

Nacelle Fire Hazard Definition, Walter Kidde Aerospace. 

18. “Incident Data Analysis Report”, Booz•Allen & Hamilton Inc., July 1994. 
86

19. NAWCADLKE-MISC-05-SR-0146, "Fixed-Wing Aircraft Fire Protection, halon 1301 

Fire Suppression Systems Effectivity Analysis", M. Tedeschi, US Naval Air System 

Team, Naval Air Warfare Center, September 30, 1994. 

20. Personal conversation with A. Thompson, C-17 System Program Office. 

21. NAWCADLKE-MISC-05-SR-0132, "Rotary Aircraft Fire Protection, halon 1301 Fire 

Suppression Systems Effectivity Analysis", M. Tedeschi and B. Leach, US Naval Air 

System Team, Naval Air Warfare Center, May 26, 1994. 

22. Memorandum From W. M. Moscrip To T.A. Simpson, 12 February, 1998, Generic 

Transport Aircraft Engine Nacelle Fire Protection System, Walter Kidde Aerospace. 

23. WL-TR-95-3077, “Halon Replacement Program for Aviation, Aircraft Engine Nacelle 

Application, Phase I – Operational Parameters Study”, April 1997. 

24. SURVIAC-TR-96-025, “F-16 Fuel Cell Inerting Technical Characteristics”, Booz·Allen 

& Hamilton Inc., July 1996. 

25. “F-16 Fuel Cell Explosion Suppression System Requirements”, Booz•Allen & Hamilton. 

September 1996. 

26. “F-16 Fuel Tank Explosion Suppression System Replacement Characterization Test With 

The W-Tank - Final Report”, Booz·Allen & Hamilton Inc., January 1998. 

27. Memorandum From Commanding Officer, Naval Research Laboratory to Director, U.S. 

Army Research Laboratory (AMSRL-WM-TB/Dr. Anthony E. Finnerty), Navy 

Shipboard halon 1301 Fire Suppressions: A Fire Incident Summary, February 1999 

28. “Shipboard Fire Scaling.” Naval Research Laboratory: 1 pp. 16 August 2001. 

<http://www.chemistry.nrl.navy.mil/6180/6186.html.> 

29. “Chesapeake Bay Fire Test Detachment (CBD).” Naval Research Laboratory: 1 pp. 16 

August 2001. <http://www.chemistry.nrl.navy.mil/6180/6180cbd.html.> 

30. Skaggs, R.R., Daniel, R.G., Miziolek, A.W., McNesby, K.L., Babushok, V.I., Tsang, W., 

and Smooke, M.D., “Spectroscopic Studies of Inhibited Opposed Flow Propane/Air 

Flames,” ARL-TR-2388, Army Research Laboratory, Aberdeen MD (2001). 

31. Yang, J.C., Donnelly, M.K., Prive, N.C., and Grosshandler, W.L., “An Apparatus for 

Screening Fire Suppression Efficiency of Dispersed Liquid Agents,” Fire Safety Journal 

36, 55-72 (2001). 

32. Grosshandler, W., Hamins, A., McGrattan, K., and Presser, C., Transient Application, 

Recirculating Pool Fire, Agent Effectiveness Screen: Final Report to the Strategic 

Environmental Research and Development Program, NISTIR 6733, National Institute of 

Standards and Technology, Gaithersburg, MD, (2001). 

33. ASTM E 2179, Standard Test Methods for Limiting Oxygen (Oxidant) Concentration in 

Gases and Vapors, ASTM International, West Conshohocken, PA, 2001. 

34. TO 1C-130H-2-2, Maintenance Instruction Ground Handling, Service, And, 1999-09-13. 

35. Electronic conversation with L. Ash, U.S. Naval Air Systems Command, August 1999. 
87

36. TO 1C-17A-4-26, Organizational Maintenance – Illustrated Parts Breakdown – Fire 

Protection, 2001-05-01. 

37. JLF-TR-88-13, “UH-60A Black Hawk Helicopter Engine Compartment Fire 

Vulnerability Tests”, August 1990. 

38. TM 55-1520 240-23P (Chinook Technical Manual).