U.S. Department 

of Transportation 

Federal Aviation 

Administration 

Advisory 

Circular 

Subject: Class B and F Cargo Compartments Date: DRAFT 

Initiated By: ANM-100 

AC No: 25.857-X 

1 PURPOSE. 

This advisory circular (AC) provides guidance concerning compliance with the 

airworthiness standards for transport category airplanes pertaining to Class B and 

Class F cargo compartments, both of which must be accessible in flight to 

crewmembers (i.e., located on the main deck). This guidance is applicable to transport 

category airplanes for which a new, amended, or supplemental type certificate is 

requested. 

2 APPLICABILITY. 

2.1 The guidance provided in this document is directed to airplane manufacturers, 

modifiers, foreign regulatory authorities, and Federal Aviation Administration (FAA) 

transport airplane type certification engineers and their designees. 

2.2 This material is neither mandatory nor regulatory in nature and does not constitute a 

regulation. It describes acceptable means, but not the only means, for demonstrating 

compliance with the applicable regulations. The FAA will consider other means of 

demonstrating compliance that an applicant may elect to present. While these guidelines 

are not mandatory, they are derived from extensive FAA and industry experience in 

determining compliance with the relevant regulations. If, however, we become aware of 

circumstances that convince us that following this AC would not result in compliance 

with the applicable regulations, we will not be bound by the terms of this AC, and we 

may require additional substantiation or design changes as a basis for finding 

compliance. 

2.3 This material does not change or create any additional regulatory requirements, nor 

does it authorize changes in, or permit deviations from, existing regulatory 

requirements. 
mm/dd/yy D R A F T AC 25.857-X 

2 

3 RELATED DOCUMENTS. 

3.1 Sections of Title 14, Code of Federal Regulations (CFR) Part 25. 

 Section 25.851, Fire extinguishers. 

 Section 25.855, Cargo or baggage compartments. 

 Section 25.857, Cargo compartment classification. 

 Section 25.858, Cargo or baggage compartment smoke or fire detection systems. 

3.2 Advisory Circulars (AC). 

This list identifies the current version of each AC at the time of publication of this AC. 

If any AC is revised after publication of this AC, you should refer to the latest version 

for guidance. You can find the latest version of the following ACs at 

http://www.faa.gov/regulations_policies/advisory_circulars/. 

 AC 20-42D, Hand Fire Extinguishers for use in Aircraft, issued January 14, 2011. 

 AC 25-9A, Smoke Detection, Penetration, and Evacuation Tests and Related Flight 

Manual Emergency Procedures, issued January 6, 1994. 

 AC 25-17A, Transport Airplane Cabin Interiors Crashworthiness Handbook, issued 

May 18, 2009. 

 AC 25-18, Transport Category Airplanes Modified for Cargo Service, issued 

January 6, 1994. 

 AC 25-22, Certification of Transport Airplane Mechanical Systems, issued March 

14, 2000.

 AC 25.851-X, Built-in Fire Extinguisher/Fire Suppression Systems in Class C and 

Class F cargo compartments, issued , 201X.

3.3 FAA Orders. 

Order 8150.4, Certification of Cargo Containers with Self-Contained Temperature 

Control (Active ULDs), dated August 28 2007. 

4 BACKGROUND. 

Paragraphs (b) and (f) of § 25.857 provide standards for certification of two classes of 

cargo compartments, Class B and Class F. A Class B cargo compartment is configured 

in a manner that allows a crewmember to extinguish any fire likely to occur in the 

compartment using a hand fire extinguisher. While the person combating the fire must 

have access to the compartment, it must not be necessary for that person to physically 

enter the compartment to extinguish the fire. A Class F cargo compartment is similar to 

a Class C compartment in that there are means to extinguish or control the fire without 

requiring a person to enter the compartment. However, a Class F cargo compartment 

can also be similar to a Class B compartment in that a crewmember could rely on the 

ability to reach any cargo within the compartment and to extinguish any fire likely to 
mm/dd/yy D R A F T AC 25.857-X 

3 

occur in the compartment using a hand fire extinguisher. Both Class B and Class F 

cargo compartments have smoke or fire detection systems to alert the crew to the 

presence of the fire. 

5 COMPARTMENT CLASSIFICATION. 

All cargo compartments must be properly classified in accordance with § 25.857 and 

meet the requirements of §§ 25.851, 25.855, 25.857, and 25.858 pertaining to the 

particular class involved. In order to establish appropriate requirements for fire 

protection, a system for classification of cargo or baggage compartments was developed 

and adopted for transport category airplanes. Classes A, B, and C were initially 

established; Classes D, E, and F were added later. Class D has been eliminated from the 

regulations. The classification is based on the means by which a fire can be detected and 

the means available to control the fire. 

5.1 A Class A compartment (see § 25.857(a)) is one that is located so close to the station of 

a crewmember that the crewmember would discover the presence of a fire immediately. 

In addition, each part of the compartment is easily accessible so that the crewmember 

could quickly extinguish a fire with a portable fire extinguisher. A Class A 

compartment is not required to have a liner. 

5.2 A Class B compartment (see § 25.857(b)) is one that is accessible in flight but more 

remote than a Class A compartment and must, therefore, incorporate a smoke or fire 

detection system to give warning at the pilot or flight engineer station. Because a fire 

would not be detected and extinguished as quickly as in a Class A compartment, a 

Class B compartment must have a liner in accordance with § 25.855(b). In flight, a 

crewmember must have sufficient access to a Class B compartment to effectively fight a 

fire with a hand fire extinguisher in any part of the compartment when standing at any 

one access point, without stepping into the compartment. There must be means to 

ensure that, while the access provisions are being used, no hazardous quantity of smoke, 

flames, or extinguishing agent will enter areas occupied by the crew or passengers. 

5.3 A Class C compartment (see § 25.857(c)) differs from a Class B compartment in that it 

is not required to be accessible in flight and must, therefore, have a built-in fire 

extinguishing or suppression system. A Class C compartment must have a liner and a 

smoke or fire detection system in accordance with §§ 25.855(b) and 25.857(c)(1). There 

must also be means to exclude hazardous quantities of extinguishant and products of 

combustion from occupied areas (see § 25.857(c)(3)). 

5.4 A Class D compartment was one in which a fire would be completely contained without 

endangering the safety of the airplane or the occupants. A Class D compartment was not 

accessible to a crewmember in flight, and instead of providing smoke or fire detection 

and extinguishment, Class D compartments were designed to control a fire by severely 

restricting the supply of available oxygen. Due to several uncontrollable fires in Class D 

compartments, they were eliminated by Amendment 25-93, effective March 19, 1998. 

As explained in Amendment 25-93, Class D cargo compartment standards pre-dating 

Amendment 25-93 are inadequate. Therefore, the FAA does not approve new Class D 
mm/dd/yy D R A F T AC 25.857-X 

4 

cargo compartments even in airplanes with a certification basis pre-dating 

Amendment 25-93. 

5.5 A Class E compartment (see § 25.857(e)) is found on an all-cargo airplane. Typically, a 

Class E compartment is the entire cabin of an all-cargo airplane; however, other 

compartments (e.g., lower lobe inaccessible cargo compartments) of such airplanes may 

be classified as Class E compartments. Shutting off the ventilating airflow to or within 

the compartment controls a fire in a Class E compartment. A Class E compartment must 

have a liner and a smoke or fire detection system installed in accordance with 

§ 25.857(e)(2). It is not required to have a built-in fire suppression system. 

5.6 A Class F compartment (see § 25.857(f)) is one that has means to control or extinguish 

a fire without requiring a crewmember to enter the compartment. However, a Class F 

cargo compartment must be readily accessible in flight and located on the main deck of 

the airplane. A Class F cargo compartment may rely on the use of a hand fire 

extinguisher to fight a fire within the compartment. Class F compartments that include a 

built-in fire extinguisher/suppression system or require the use of acceptable fire 

containment covers (FCCs) or fire resistant containers (FRCs) may meet these 

requirements if the FCCs or FRCs meet certain requirements. The Class F compartment 

must have a smoke or fire detection system installed in accordance with § 25.857(f)(1). 

Unless there are other means of containing the fire and protecting critical systems and 

structure, a Class F compartment must have a liner meeting the requirements of part III 

of appendix F to part 25 or other approved equivalent methods (see § 25.855(b)). For 

example, a Class F cargo compartment where FCCs or FRCs meet the liner 

requirements (i.e., part 25, appendix F, part III flame penetration resistant means) would 

be acceptable. The Class F cargo compartment was introduced as a practicable and safe 

alternative to the previous practice of providing large Class B cargo compartments. The 

Class B compartments were limited to the main deck for accessibility reasons. 

Likewise, Class F cargo compartments should also be limited to the main deck for 

accessibility. All lower deck cargo compartments in airplanes carrying passengers need 

to comply with the Class C cargo compartment requirements of § 25.857(c). 

6 FIRE PROTECTION FEATURES. 

Based on the class of the compartment, fire protection features must be provided. The 

fire protection features must be shown to meet the standards established by the original 

type certification basis for the airplane or later part 25 standards. These features may 

include liners, control of ventilation, fire/smoke detection systems, hand fire 

extinguishers, and built-in fire suppression systems. 

6.1 Liners.

6.1.1 The primary purpose of a liner is to prevent a fire originating in a cargo compartment 

from spreading to other parts of the airplane before it can be brought under control. For 

Class B compartments, it is assumed that the fire will be quickly extinguished, so the 

liner must be qualified to part 25, appendix F, part I requirements. For Class F cargo 

compartments, the fire might have grown larger prior to being suppressed so better 
mm/dd/yy D R A F T AC 25.857-X 

5 

protection is needed to prevent damage to surrounding systems and structure. Therefore, 

a Class F liner must be qualified to part 25, appendix F, part III requirements. However, 

the liner does not need to serve as the compartment seal, although it is frequently used 

to perform the secondary functions of containing discharged extinguishing agent and 

controlling the flow of oxygen into the compartment. If other means, such as 

compartment walls, are not capable of performing those functions, the liner must be 

sufficiently airtight to perform them. 

6.1.2 The liner must have sufficient fire integrity to prevent flames from burning through the 

liner before the fire can be brought under control and the heat from the fire is 

sufficiently dissipated. As stated in part III of appendix F to part 25, in addition to the 

basic liner material, the term "liner" includes any design feature, such as a joint or 

fastener that would affect the capability of the liner to safely contain a fire. 

6.2 Access.

6.2.1 Class B. 

Class B compartments must provide sufficient accessibility to enable a crewmember to 

reach any part of the compartment by hand or with the contents of a hand fire 

extinguisher without physically entering the compartment. This requirement, by its 

nature, tends to limit the size and shape of the compartment. Additionally, the access 

provisions should be sufficiently large to enable the crewmember to determine visually 

that a fire has been extinguished. Access is also a function of how the compartment is 

configured rather than just dimension and/or volume. In determining access, it would 

not be acceptable for there to be a need to pull baggage or cargo onto the floor of the 

passenger compartment to gain access to the seat of the fire. Such action may introduce 

a safety hazard to the passengers. 

6.2.1.1 “To reach any part of the compartment” means that the crewmember 

should be able to open the door or hatch and, standing in the opening, 

effectively fight a fire anywhere in the compartment where cargo or 

baggage can be located. The extension of the crewmember’s reach through 

the use of a fire extinguisher is limited such that the combination of reach 

and the extinguisher should not be more than 52 inches. 

6.2.1.1.1 The FAA tasked an Aviation Rulemaking Advisory Committee, which 

established the Cargo Standards Harmonization Working Group 

(CSHWG), to develop new or revised requirements for Class B cargo 

compartments in transport category airplanes. The CSHWG 

recommendations included an estimate of a Class B cargo compartment 

that would meet the intent for a crewmember to reach any part of the 

compartment. Reportedly based on the estimated reach of a 95th percentile 

male, one recommendation was that the outline of any compartment, 

viewed from above, should fit within a vertical cylinder of radius 

52 inches (132 cm) measured from the centerline of the access door or 

hatch (see figure 1). This dimension assumes the above male can reach a 

one-foot square box located anywhere within the compartment. Access by 
mm/dd/yy D R A F T AC 25.857-X 

6 

a smaller crewmember to reach the same area within the compartment 

could require that the crewmember move laterally within the access door 

or hatch opening, while not physically entering the compartment. 

However, the FAA’s position is that the use of a 95th percentile male is 

not realistic in that many flight attendants are female and have a smaller 

reach1. For example, a 50th percentile female has a reach of 28.96 inches 

(~29 inches) and the FAA holds that this is a reasonable value to use. In 

addition, when determining a distance that a crewmember can effectively 

fight a fire within a Class B cargo compartment, consideration should be 

given to the distance that the fire extinguisher stream can be accurately 

directed. However, the published “range” of hand fire extinguishers can be 

many feet and will vary depending on bottle pressure and mass of the fire 

extinguishing agent. Using accepted values for extinguisher range from 

recognized authorities (e.g., the U.S. Underwriters Laboratories) would 

result in very large Class B cargo compartments that are beyond the ability 

for crewmembers to effectively fight a fire. A reasonable value that a hand 

fire extinguisher can be accurately directed is no more than two feet. 

Therefore, in consideration of reasonable effective reach to extinguish a 

fire, harmonization with the guidance provided by other regulatory 

authorities, the recommendations of the CSHWG, and service history of 

airplanes with small Class B cargo compartments, a fire in a small cargo 

compartment may be effectively fought if the contents of cargo and 

baggage are within an arc not exceeding a 52-inch radius. 

6.2.1.2 Should an applicant request FAA certification of an airplane with a 

Class B cargo compartment that exceeds the criteria included in this AC, 

the FAA will expect the applicant to perform full-scale fire extinguishing 

tests. These tests will be used to demonstrate compliance to the regulations 

and to establish the quantity of fire extinguishing agent that must be 

provided to ensure an acceptable level of safety. 

 

1

 Harrison, Catherine R., Robinette, Kathleen M., “CAESAR: Summary Statistics for the Adult Population (Ages 

18-65) of the United States of America,” AFRL-HE-WP-TR-2002-0170, United States Air Force Research 

Laboratory, June 2002. 
mm/dd/yy D R A F T AC 25.857-X 

7 

Figure 1. Examples of Possible Cargo Compartment Shapes within 52” Reach 

from Access Point Centerline. 

C/L

access point

52" radius

6.3 Means to suppress or extinguish a fire. 

6.3.1 Class F. 

In the case of a Class F compartment, a means should be provided to suppress or 

extinguish a fire without a crewmember entering the compartment. 

6.3.1.1 One means is to design the compartment to Class C requirements but not 

include a built-in fire suppression system. One suppression method might 

be to use a plumbing and nozzle distribution system within the 

compartment that would provide acceptable suppression capability 

throughout the volume of the compartment. The source for such a system 

could be hand fire extinguishers, which interface with the distribution 

system through a suitable interface nozzle. This reduces the complexity 

and costs associated with a built-in suppression system and could be 

suitable for smaller compartments. For certification purposes, the 

extinguishing agent concentration should be measured in flight, following 

airplane flight manual (AFM) procedures, and the length of protection 

time afforded by the system recorded. This time of protection should be 

used to establish AFM limitations for cargo or baggage compartment fire 

protection times. The operator could then use these times for route 

planning. For Halon 1301 fire extinguishing agent, a minimum 5-percent 

concentration by volume at all points in the compartment is considered 

adequate for initial knockdown of a fire, and a 3-percent concentration by 

volume at all points in the compartment is considered the minimum for 

controlling a fire after it is knocked down2

. The use of this option requires 

 

2

 Gassmann, J., Hill, R., “Fire Extinguishing Methods for New Passenger/Cargo Aircraft,” Federal Aviation 

Administration, Final Report FAA-RD-71-68, November 1971. 
mm/dd/yy D R A F T AC 25.857-X 

8 

the use of a liner, if needed, as noted in § 25.855(c). Full-scale or 

high-fidelity fire extinguishing testing may be necessary. 

6.3.1.2 Another means of providing fire protection in a Class F compartment 

would be to provide a fire suppression system similar to a Class C cargo 

compartment. Further guidance on this type of design installation can be 

found in AC 25.851-X. However, in general, a Class F cargo compartment 

that uses a built-in fire suppression system should meet the same 

requirements as a Class C cargo compartment. For example, an applicant 

for a Class F cargo compartment with a built-in fire suppression system 

must ensure that: 

6.3.1.2.1 No extinguishing agent likely to enter personnel compartments will be 

hazardous to the occupants; 

6.3.1.2.2 No discharge of the extinguisher can cause structural damage; 

6.3.1.2.3 The capacity of each required built-in extinguishing system must be 

adequate for any fire likely to occur in the compartment where used, 

considering the volume of the compartment and the ventilation rate; 

6.3.1.2.4 There are means to exclude hazardous quantities of smoke, flames, or 

extinguishing agent from any compartment occupied by the crew or 

passengers; 

6.3.1.2.5 There are means to control ventilation and drafts within the compartment 

so that the extinguishing agent used can control any fire that may start 

within the compartment; and 

6.3.1.2.6 Flight tests are conducted to ensure compliance with the provisions in 

§ 25.857(f). 

6.3.1.3 Another means of providing fire protection in a Class F compartment 

involves the use of FRCs or FCCs shown to be capable of containing a 

fire. Some FCCs have already been developed and are typically 

constructed of woven fiberglass-based materials that will pass the oil 

burner test requirements in part 25, appendix F, part III. 

6.3.1.3.1 Using FRCs or FCCs shown to be capable of containing a fire in 

complying with Class F cargo compartment fire protection requirements 

may meet expectations in the § 25.857 at Amendment 25-XXX3. For a 

Class F cargo or baggage compartment not using FCCs or FRCs, § 25.857 

requires a ceiling and sidewall liner constructed of materials that meet the 

requirements of part III of appendix F to part 25. The liner must also be 

 

3

 We are proposing new rulemaking. The Amendment level will be added when the rule is published. 
mm/dd/yy D R A F T AC 25.857-X 

9 

separated from the airplane structure (except for attachments), while the 

floor panels must comply with part I of appendix F. 

6.3.1.3.2 If FCCs or FRCs are proposed as a means of compliance for the new 

Class F compartment, they must meet these standards (i.e., part III of 

appendix F to part 25 for the sides and top and part I of appendix F for the 

bottom). 

6.3.1.3.3 It is recommended that the responsible aircraft certification office (ACO) 

be contacted for concurrence when FCC or FRC qualification is envisaged 

in order to address the relevant test method. Full-scale or high-fidelity fire 

testing may be necessary to ensure that the FCC or FRC can contain a fire 

for the longest flight time (diversion) required in service. The ACO should 

coordinate with the Transport Airplane Directorate. 

6.3.1.3.4 If FCCs are used as the sole means of compliance, they should completely 

surround all cargo, including underneath the cargo, except for obviously 

nonflammable items, such as metal stock, machinery, and nonflammable 

fluids without flammable packaging. These FCCs would need to meet 

part III of appendix F to part 25. Because the fire is controlled or 

extinguished within the isolated compartment, but is separated from the 

actual cargo compartment boundaries, the cargo compartment liner 

requirements of § 25.855(c) would not apply. However, the effects of the 

heat generated by the contained/covered fire should be evaluated to ensure 

that adjacent systems and structure are not adversely affected. For 

certification purposes, test data with the actual design configuration and 

possible fire sources would have to be provided. The temperature and heat 

load time history measurements at various locations above, around, and 

below the FCC are needed to ensure the continued safe function of 

adjacent systems and structure. The time history data should be used to 

establish the length of protection time afforded by the system and 

subsequent AFM limitations for cargo or baggage compartment fire 

protection times. The operator would then use these times for route 

planning purposes. 

6.3.1.3.5 The issue of compliance to the cargo compartment requirements for smoke 

or fire detection in § 25.858 may represent unique challenges if FCCs or 

FRCs are used. Crew awareness is a critical factor to ensure adequate fire 

protection on airplanes. Applicants for FAA approval should consider the 

use of Infrared (IR) Camera or other means to ensure adequate detection 

of a fire within the cargo compartment where FCCs and FRCs are used. 

Full-scale or high-fidelity fire testing may be necessary to ensure that the 

smoke or fire detection system can provide adequate detection. 

6.3.1.4 Class F cargo compartment designs that rely on fire containment (e.g., fire 

hardened containers/pallets, FRCs and/or FCCs placed over palletized 
mm/dd/yy D R A F T AC 25.857-X 

10 

loads or non-fire hardened containers) should be considered with regard to 

the possibility of incorrect usage or cargo loading errors. 

6.3.1.5 All practicable means to prevent the carriage of cargo in standard 

containers or pallets (if special pallets are required) and/or the omission of 

FCCs or FRCs should be incorporated. Means may include, but not be 

limited to: 

6.3.1.5.1 Physical features at the container/pallet to cargo compartment floor 

interface; 

6.3.1.5.2 Operational procedures, such as requiring airplane crew verification of 

cargo loading before every flight; 

6.3.1.5.3 A suitable detection system that would warn the crew in the event a 

non-authorized cargo configuration has been loaded. 

6.4 Extinguishing Agent.

6.4.1 In order to effectively extinguish or control a fire in a Class B or Class F cargo or 

baggage compartment, sufficient fire extinguishing agent must be allocated. The FAA 

requirements for hand fire extinguishers and fire extinguishing agents are included in 

§ 25.851(a). General guidance on this topic is included in AC 20-42D. The FAA 

requirements for built-in fire suppression systems and fire extinguishing agent are 

included in § 25.851(b). AC 25.851-X contains guidance for built-in fire 

extinguishing/suppression systems. However, the FAA has not issued substantive 

guidance addressing installation issues associated with non-halon fire extinguishing 

agent applications. Instead of such guidance, the FAA will ensure that each non-halon 

agent has successfully passed the minimum performance standard4

 for that application 

(i.e., lavatory trash receptacle, hand fire extinguisher, engine/auxiliary power unit fire 

extinguishing system, or cargo compartment fire suppression system). The purpose is to 

ensure the performance of the proposed non-halon agent provides protection equivalent 

to that provided by halon and that the applicant has addressed installation issues 

associated with the specific application. Depending on the properties of the agent, the 

means to deliver the agent, and the means to determine the concentration of the agent, 

full-scale or high-fidelity fire testing may be necessary to ensure that the non-halon fire 

extinguishing or fire suppression system provides adequate performance. AC 20-42D 

provides an acceptable means to implement the CSHWG provisions of § 25.851(a) that 

require at least one hand fire extinguisher be located in the pilot compartment, at least 

one readily accessible hand fire extinguisher be available for use in each Class A or 

Class B cargo/baggage compartment and in each accessible Class E or Class F 

cargo/baggage compartment, and one or more hand fire extinguishers be located in the 

passenger compartment for airplanes with a passenger seating capacity of 7 or more. 

 

4

 Reports available at the FAA William J. Hughes Technical Center Fire Safety Branch website: 

http://www.fire.tc.faa.gov. 
mm/dd/yy D R A F T AC 25.857-X 

11 

6.5 Fire Control. “To control a fire” (§ 25.857(f)(2)) means that the fire does not grow to a 

state where damage to the airplane or harm to the passengers or crew occurs during the 

length of time of protection that the fire protection system is demonstrated to afford. 

This in turn means that critical airplane systems and structure located adjacent to the 

compartment are not adversely affected, and the temperature and air contaminants in 

areas occupied by passengers and crew do not reach hazardous levels. 

6.5.1 Adequate protection should be provided for cockpit voice and flight data recorder and 

wiring, windows, primary flight controls (unless it can be shown that a fire cannot cause 

jamming or loss of control), and other systems, structure, and equipment within or 

adjacent to the compartment that are required for safe flight and landing. 

6.5.2 Regardless of a compartment’s classification, Class B or Class F, it must be 

demonstrated that hazardous quantities of smoke, flames, extinguishing agent, or 

noxious gasses do not enter any compartment occupied by passengers or crewmembers. 

AC 25-9A, Smoke Detection, Penetration, and Evacuation Tests and Related Flight 

Manual Emergency Procedures, provides guidance concerning smoke penetration 

testing. 

6.5.3 If an airplane has a Class B or Class F cargo compartment, portable protective breathing 

equipment must be provided for the appropriate crewmembers in accordance with 

§ 25.1439. If the airplane is operated under part 121, the protective breathing equipment 

must meet the more stringent standards of § 121.337. 

6.5.4 Additional protective breathing equipment or breathing gas supply, and additional fire 

extinguishers, may be required to ensure that the fire can be controlled for the time the 

airplane is expected to be in the air after onset of a fire. As required in § 25.851(a) the 

quantity of extinguishing agent used in each extinguisher required by this section must 

be appropriate for the kinds of fires likely to occur where used. Depending upon the 

proposed fire extinguishing agent and quantity of the agent provided, full-scale or 

high-fidelity fire extinguishing testing may be necessary to ensure an adequate level of 

protection. 

6.6 Reclassification.

As explained in paragraph 5.4, the Class D cargo compartment has been eliminated 

from the regulations due to limited effectiveness in providing fire protection. The 

Class F compartment is not intended to be a Class D compartment with smoke or fire 

detection. It is not acceptable to simply reclassify a compartment as Class F and use the 

same fire protection methodology as was used for Class D compartments. Means for 

controlling ventilation in Class D cargo compartments were shown to be ineffective in 

controlling a fire in many cases. This was evidenced by a number of accidents and 

incidents involving fires in Class D cargo compartments as discussed in Docket 

No. 28937, Notice 97-10, and Amendment 25-93. 
mm/dd/yy D R A F T AC 25.857-X 

12 

7 PROCEDURES AND LIMITATIONS. 

7.1 To ensure that the contents of Class B and F compartments are accessible to combat a 

fire, the cargo or baggage loading limitations and any operational limitations or 

procedures provided are expected to be identified with placards in the compartment. 

The loading and operational limitations must also be addressed in the appropriate 

weight and balance or loading document. 

7.2 Any operational limitations or procedures necessary to ensure the effectiveness of the 

fire protection system for Class B and Class F cargo and baggage compartments should 

be clearly defined in the AFM. This should include such items as any changes to the 

ventilation system to prevent the entrance of smoke or gasses into occupied areas, use 

of hand fire extinguishers, use of protective breathing equipment, use of protective 

clothing, and use of the FCCs. The applicant and the ACO should work closely with the 

FAA Flight Standards organization (Aircraft Evaluation Group) to ensure that 

additional training necessary for crewmembers assigned to combat fires is adequately 

addressed. 

7.3 Any time limit for a cargo or baggage compartment fire protection system, or other 

conditions or procedures related to combating a fire in a compartment, should be clearly 

defined in the AFM. 

8 AFM CONSIDERATIONS. 

8.1 Any crewmember designated to combat a fire in a Class B compartment will need 

special training. Fires occurring in luggage are difficult to extinguish completely and 

rekindling may occur. Crewmembers designated to combat fires in Class B 

compartments should be trained to check periodically to ensure that a fire has not grown 

back to hazardous proportions. The applicant and the ACO should work with the 

appropriate organizations, including the operators, to ensure that training in the use of 

protective breathing equipment, fire extinguishers, protective gloves and clothing is 

provided. 

8.2 AFMs should contain instructions to land at the nearest suitable airport following smoke 

or fire detection, unless it can be positively determined that the fire is extinguished. 

8.3 Any limitations regarding occupancy of Class B or Class F compartments during flight, 

or during takeoff and landing, should be defined in the AFM. 

8.4 Any loading restrictions associated with access to cargo or baggage or special 

containers should be clearly identified in the AFM. This would include, but not be 

limited to, placement of luggage in a Class B compartment or identification of special 

containers or covers associated with fire protection in a Class F compartment. If FCCs 

or FRCs are used in conjunction with a Class F cargo compartment, they should be easy 

to install and sufficiently durable to withstand in-service conditions. 
mm/dd/yy D R A F T AC 25.857-X 

13 

END