63302 Federal Register / Vol. 79, No. 205 / Thursday, October 23, 2014 / Rules and Regulations 

Composite Wing and Fuel Tank PostCrash Fire Survivability 

1. The wing fuel tank structure must 

withstand an external fuel-fed pool fire 

for a minimum of 5 minutes. 

2. The integrity of the wing fuel tank 

structure must be demonstrated at: 

• Minimum fuel load, not less than 

reserve fuel level; 

• Maximum fuel load equal to the 

maximum range fuel quantity; and 

• Any other critical fuel loads. 

3. The demonstration must consider 

fuel tank flammability, burn-through 

resistance, wing structural strength 

retention properties, and auto-ignition 

threats from localized heating of 

composite structure, fasteners, or any 

other feature that may produce an 

ignition source during a ground fire 

event for the required time duration. 

Issued in Renton, Washington, on October 

16, 2014. 

Michael Kascycki, 

Acting Manager, Transport Airplane 

Directorate. 

[FR Doc. 2014–25239 Filed 10–22–14; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2014–0421; Special 

Conditions No. 25–571–SC] 

Special Conditions: Boeing 

Commercial Airplanes, Model 767–2C 

Airplane; Interaction of Fuel Systems 

and Structures 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for the Boeing Model 767–2C 

airplane. This airplane will have novel 

or unusual design features when 

compared to the state of technology 

envisioned in the airworthiness 

standards for transport category 

airplanes. These design features include 

the addition of four body fuel tanks and 

a modified fuel management system 

that, directly or as a result of failure or 

malfunction, could affect the airplane’s 

structural performance. The applicable 

airworthiness regulations do not contain 

adequate or appropriate safety standards 

for these design features. These special 

conditions contain the additional safety 

standards that the Administrator 

considers necessary to establish a level 

of safety equivalent to that established 

by the existing airworthiness standards. 

DATES: Effective Date: This action is 

effective on November 24, 2014. 

FOR FURTHER INFORMATION CONTACT: 

Mark Freisthler, FAA, Airframe and 

Cabin Safety Branch, ANM–115, 

Transport Airplane Directorate, Aircraft 

Certification Service, 1601 Lind Avenue 

SW., Renton, Washington 98057–3356; 

telephone 425–227–1119; facsimile 

425–227–1232. 

SUPPLEMENTARY INFORMATION: 

Background 

On January 18, 2010, Boeing 

Commercial Airplanes applied for an 

amendment to Type Certificate No. 

A1NM to include the new Model 767– 

2C. The Boeing Model 767–2C, which is 

a derivative of the Model 767–200 

currently approved under Type 

Certificate No. A1NM, is a transport 

category airplane, intended for use as a 

freighter, powered by two PW4062 

engines with a maximum takeoff weight 

of 415,000 pounds. 

The Boeing Model 767–2C will have 

more fuel capacity than a traditional 

freighter through the addition of four 

body fuel tanks. The Model 767–2C 

contains fuel systems that could, 

directly or as a result of failure or 

malfunction, affect the aircraft’s 

structural performance. Current 

regulations do not take into account 

loads for the airplane due to the effects 

of fuel system failures on structural 

performance; therefore, special 

conditions are needed. 

Type Certification Basis 

Under the provisions of Title 14, Code 

of Federal Regulations (14 CFR) 21.101, 

Boeing must show that the Model 767– 

2C meets the applicable provisions of 14 

CFR part 25, as amended by 

Amendments 25–0 through 25–130, 

except for earlier amendments as agreed 

upon by the FAA. These regulations 

will be incorporated into Type 

Certificate No. A1NM after type 

certification approval of the Model 767– 

2C. 

In addition, the certification basis 

includes other regulations, special 

conditions, and exemptions that are not 

relevant to these special conditions. 

Type Certificate No. A1NM will be 

updated to include a complete 

description of the certification basis for 

these model airplanes. 

If the Administrator finds that the 

applicable airworthiness regulations 

(i.e., 14 CFR part 25) do not contain 

adequate or appropriate safety standards 

for the Model 767–2C because of a novel 

or unusual design feature, special 

conditions are prescribed under the 

provisions of § 21.16. 

Special conditions are initially 

applicable to the model for which they 

are issued. Should the type certificate 

for that model be amended later to 

include any other model that 

incorporates the same or similar novel 

or unusual design feature, or should any 

other model already included on the 

same type certificate be modified to 

incorporate the same or similar novel or 

unusual design feature, the special 

conditions would also apply to the other 

model under § 21.101. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the Model 767–2C must 

comply with the fuel vent and exhaust 

emission requirements of 14 CFR part 

34 and the noise certification 

requirements of 14 CFR part 36. 

The FAA issues special conditions, as 

defined in 14 CFR 11.19, in accordance 

with § 11.38, and they become part of 

the type-certification basis under 

§ 21.101. 

Novel or Unusual Design Features 

The Boeing Model 767–2C will 

incorporate the following novel or 

unusual design features: Fuel system 

changes including the addition of 

forward and aft body fuel tanks, a mainto-center-tank gravity transfer system, 

hydraulically-powered-pumps for 

jettison, a nitrogen generation system for 

inerting of all fuel tanks, and a pressureregulating closed fuel tank vent system. 

Digital electronic controls (i.e., fuel 

management systems) are added for 

control and monitoring of these systems. 

Discussion 

The fuel management system is 

designed to keep the fuel distributed in 

accordance with fuel usage 

requirements. System failures of these 

new and modified systems may result in 

adverse fuel distributions or center-ofgravity excursions that increase the 

airplane loads. For example, a failure of 

the main tank gravity drain valve may 

result in less wing main tank fuel than 

normal management; or failure of the 

body auxiliary tank transfer systems 

may result in excessive body fuel at 

landing. Additionally, failures of the 

nitrogen generation system, fuel transfer 

system, or vent/pressure regulating 

system may result in excessive fuel tank 

pressures. These types of failures are 

addressed by these special conditions. 

Special conditions have been applied 

on past airplane programs in order to 

require consideration of the effects of 

systems on structures. These special 

conditions are similar to those 

previously applied except that the scope 

is limited to new fuel system features 

unique to the Model 767–2C. These 


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Federal Register / Vol. 79, No. 205 / Thursday, October 23, 2014 / Rules and Regulations 63303 

special conditions contain the 

additional safety standards that the 

Administrator considers necessary to 

establish a level of safety equivalent to 

that established by the existing 

airworthiness standards. 

Discussion of Comments 

Notice of proposed special conditions 

No. 25–14–07–SC for the Boeing Model 

767–2C airplane was published in the 

Federal Register on July 2, 2014 (79 FR 

37670). No comments were received, 

and the special conditions are adopted 

as proposed. 

Applicability 

As discussed above, these special 

conditions are applicable to the Boeing 

Model 767–2C airplane. Should Boeing 

Commercial Airplanes apply at a later 

date for a change to the type certificate 

to include another model incorporating 

the same novel or unusual design 

feature, the special conditions would 

apply to that model as well. 

Conclusion 

This action affects only certain novel 

or unusual design features on one model 

of airplanes. It is not a rule of general 

applicability. 

List of Subjects in 14 CFR Part 25 

Aircraft, Aviation safety, Reporting 

and recordkeeping requirements. 

■ The authority citation for these 

special conditions is as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701, 

44702, 44704. 

The Special Conditions 

Accordingly, pursuant to the 

authority delegated to me by the 

Administrator, the following special 

conditions are issued as part of the type 

certification basis for Boeing 

Commercial Airplanes Model 767–2C 

airplane. 

1. Interactions of fuel systems and 

structures. General. 

a. For airplanes equipped with fuel 

systems that affect structural 

performance, either directly or as a 

result of a failure or malfunction, the 

influence of these systems and their 

failure conditions must be taken into 

account when showing compliance with 

the requirements of 14 CFR part 25 

subparts C and D. 

b. The criteria in Section 2 below 

must be used for showing compliance 

with these special conditions for 

airplanes equipped with fuel systems 

that either directly or as a result of 

failure or malfunction affect structural 

performance. 

c. The criteria only address the direct 

structural consequences of the system 

responses and performances and cannot 

be considered in isolation but should be 

included in the overall safety evaluation 

of the airplane. These criteria may in 

some instances duplicate standards 

already established for this evaluation. 

These criteria are only applicable to 

structural elements whose failure could 

prevent continued safe flight and 

landing. Specific criteria that define 

acceptable limits on handling 

characteristics or stability requirements 

when operating in the system degraded 

or inoperative mode are not provided in 

these special conditions. 

d. Depending on the specific 

characteristics of the airplane, 

additional studies may be required that 

demonstrate the capability of the 

airplane to meet other realistic 

conditions such as alternative gust or 

maneuver descriptions for an airplane 

equipped with a load alleviation system. 

e. The following definitions are 

applicable to these special conditions: 

(1) Structural performance: Capability 

of the airplane to meet the structural 

requirements of part 25. 

(2) Flight limitations: Limitations that 

can be applied to the airplane flight 

conditions following an in-flight 

occurrence and that are included in the 

airplane flight manual (e.g., speed 

limitations, avoidance of severe weather 

conditions, etc.). 

(3) Operational limitations: 

Limitations, including flight limitations, 

that can be applied to the airplane 

operating conditions before dispatch 

(e.g., fuel, payload and Master 

Minimum Equipment List limitations). 

(4) Probabilistic terms: The 

probabilistic terms (probable, 

improbable, extremely improbable) used 

in these special conditions are the same 

as those used in § 25.1309. 

(5) Failure condition: The term failure 

condition is the same as that used in 

§ 25.1309. However, these special 

conditions apply only to system failure 

conditions that affect the structural 

performance of the airplane (e.g., system 

failure conditions that induce loads, 

change the response of the airplane to 

inputs such as gusts or pilot actions, or 

lower flutter margins). The system 

failure conditions include consequential 

or cascading effects resulting from the 

first failure. 

2. Effects of Fuel System Failure on 

Structures. The following criteria will 

be used in determining the influence of 

the fuel system and its failure 

conditions on the airplane structural 

elements. 

a. Fuel system fully operative. With 

the fuel system fully operative, the 

following apply: 

(1) Limit loads must be derived in all 

normal operating configurations of the 

fuel system from all the limit conditions 

specified in subpart C (or used in lieu 

of those specified in subpart C), taking 

into account any special behavior of 

such a system or associated functions or 

any effect on the structural performance 

of the airplane that may occur up to the 

limit loads. In particular, any significant 

nonlinearity (rate of fuel transfer, 

thresholds or any other system 

nonlinearities) must be accounted for in 

a realistic or conservative way when 

deriving limit loads from limit 

conditions. 

(2) The airplane must meet the 

strength requirements of part 25 (i.e., 

static strength, residual strength), using 

the specified factors to derive ultimate 

loads from the limit loads defined 

above. The effect of nonlinearities must 

be investigated beyond limit conditions 

to ensure the behavior of the system 

presents no anomaly compared to the 

behavior below limit conditions. 

However, conditions beyond limit 

conditions need not be considered when 

it can be shown that the airplane has 

design features that will not allow it to 

exceed those limit conditions. 

(3) The airplane must meet the 

aeroelastic stability requirements of 

§ 25.629. 

b. Fuel system in the failure 

condition. For any fuel system failure 

condition not shown to be extremely 

improbable, the following apply: 

(1) At the time of occurrence, starting 

from 1-g level flight conditions, a 

realistic scenario, including pilot 

corrective actions, must be established 

to determine the loads occurring at the 

time of failure and immediately after 

failure. 

(i) For static strength substantiation, 

these loads, multiplied by an 

appropriate factor of safety that is 

related to the probability of occurrence 

of the failure, are ultimate loads to be 

considered for design. The factor of 

safety is defined in Figure 1. 


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63304 Federal Register / Vol. 79, No. 205 / Thursday, October 23, 2014 / Rules and Regulations 

(ii) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in subparagraph 2b(1)(i). 

For pressurized cabins, these loads must 

be combined with the normal operating 

differential pressure. 

(iii) Freedom from aeroelastic 

instability must be shown up to the 

speeds defined in § 25.629(b)(2). For 

failure conditions that result in speeds 

beyond VC/MC, freedom from 

aeroelastic instability must be shown to 

increased speeds, so that the margins 

intended by § 25.629(b)(2) are 

maintained. 

(iv) Failures of the fuel system that 

result in forced structural vibrations 

(oscillatory failures) must not produce 

loads that could result in detrimental 

deformation of the affected structural 

elements. 

(2) For continuation of flight, for an 

airplane in the system failed state and 

considering any appropriate 

reconfiguration and flight limitations, 

the following apply: 

(i) The loads derived from the 

following conditions (or used in lieu of 

the following conditions) at speeds up 

to VC/MC, or the speed limitation 

prescribed for the remainder of the 

flight, must be determined: 

(A) The limit symmetrical 

maneuvering conditions specified in 

§§ 25.331 and 25.345. 

(B) The limit gust and turbulence 

conditions specified in §§ 25.341 and 

25.345. 

(C) The limit rolling conditions 

specified in § 25.349 and the limit 

unsymmetrical conditions specified in 

§§ 25.367 and 25.427(b) and (c). 

(D) The limit yaw maneuvering 

conditions specified in § 25.351. 

(E) The limit ground loading 

conditions specified in §§ 25.473, 

25.491, and 25.493. 

(ii) For static strength substantiation, 

each part of the structure must be able 

to withstand the loads in paragraph 

2b(2)(i) of these special conditions 

multiplied by a factor of safety 

depending on the probability of being in 

this failure state. The factor of safety is 

defined in Figure 2. 

(iii) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in paragraph 2b(2)(ii) of 

these special conditions. For 

pressurized cabins, these loads must be 

combined with the normal operating 

differential pressure. 

(iv) If the loads induced by the failure 

condition have a significant effect on 

fatigue or damage tolerance, then their 

effects must be taken into account. 

(v) Freedom from aeroelastic 

instability must be shown up to a speed 

determined from Figure 3. Flutter 

clearance speeds V′ and V′′ may be 

based on the speed limitation specified 


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Federal Register / Vol. 79, No. 205 / Thursday, October 23, 2014 / Rules and Regulations 63305 

for the remainder of the flight using the 

margins defined by § 25.629(b). 

(vi) Freedom from aeroelastic 

instability must also be shown up to V′ 

in Figure 3 above, for any probable 

system failure condition combined with 

any damage required or selected for 

investigation by § 25.571(b). 

(3) Consideration of certain failure 

conditions may be required by other 

sections of part 25 regardless of 

calculated system reliability. Where 

analysis shows the probability of these 

failure conditions to be less than 10¥9, 

criteria other than those specified in this 

paragraph may be used for structural 

substantiation to show continued safe 

flight and landing. 

c. Failure indications. For fuel system 

failure detection and indication, the 

following apply: 

(1) The fuel system must be checked 

for failure conditions, not extremely 

improbable, that degrade the structural 

capability below the level required by 

part 25 or significantly reduce the 

reliability of the remaining system. As 

far as reasonably practicable, the flight 

crew must be made aware of these 

failures before flight. Certain elements 

of the fuel system, such as mechanical 

and hydraulic components, may use 

special periodic inspections, and 

electronic components may use daily 

checks, in lieu of detection and 

indication systems to achieve the 

objective of this requirement. These 

identified inspections must be limited 

to components that are not readily 

detectable by normal detection and 

indication systems and where service 

history shows that inspections will 

provide an adequate level of safety. 

(2) The existence of any failure 

condition, not extremely improbable, 

during flight that could significantly 

affect the structural capability of the 

airplane and for which the associated 

reduction in airworthiness can be 

minimized by suitable flight limitations, 

requires a caution level alert for 

immediate flightcrew awareness and a 

warning level alert for immediate 

flightcrew awareness and corrective 

action. For example, a flightcrew alert 

during flight is required for failure 

conditions that result in a factor of 

safety between the airplane strength and 

the loads of subpart C below 1.25, or 

flutter margins below V′′, because it 

could significantly affect the structural 

capability of the airplane. 

d. Dispatch with known failure 

conditions. If the airplane is to be 

dispatched in a known fuel system 

failure condition that affects structural 

performance, or affects the reliability of 

the remaining system to maintain 

structural performance, then the 

provisions of these special conditions 

must be met, including the provisions of 

paragraph 2a for the dispatched 

condition, and paragraph 2b for 

subsequent failures. Expected 

operational limitations may be taken 

into account in establishing Pj as the 

probability of failure occurrence for 

determining the safety margin in Figure 

1. Flight limitations and expected 

operational limitations may be taken 

into account in establishing Qj as the 

combined probability of being in the 

dispatched failure condition and the 

subsequent failure condition for the 

safety margins in Figures 2 and 3. These 

limitations must be such that the 

probability of being in this combined 

failure state and then subsequently 

encountering limit load conditions is 

extremely improbable. No reduction in 

these safety margins is allowed if the 

subsequent system failure rate is greater 

than 10¥3 per hour. 

Issued in Renton, Washington, on October 

16, 2014. 

Michael Kaszycki, 

Acting Manager, Transport Airplane 

Directorate, Aircraft Certification Service. 

[FR Doc. 2014–25242 Filed 10–22–14; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2014–0532; Directorate 

Identifier 2014–CE–016–AD; Amendment 

39–17994; AD 2014–21–02] 

RIN 2120–AA64 

Airworthiness Directives; Pacific 

Aerospace Limited Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Final rule. 


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