15890 Federal Register / Vol. 74, No. 66 / Wednesday, April 8, 2009 / Proposed Rules 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. NM400 Special Conditions No. 

25–09–03–SC] 

Special Conditions: Boeing Model 747– 

8/–8F Airplane, Interaction of Systems 

and Structures 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed special 

conditions. 

SUMMARY: This notice proposes special 

conditions for the Boeing Model 747–8/ 

–8F 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 

their effects on the structural 

performance. These proposed 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. 

Additional special conditions will be 

issued for other novel or unusual design 

features of the Boeing 747–8/–8F 

airplanes. 

DATES: Comments must be received on 

or before May 26, 2009. 

ADDRESSES: Comments on this proposal 

may be mailed in duplicate to: Federal 

Aviation Administration, Transport 

Airplane Directorate, Attention: Rules 

Docket (ANM–113), Docket No. NM400, 

1601 Lind Avenue, SW., Renton, 

Washington 98057–3356; or delivered in 

duplicate to the Transport Airplane 

Directorate at the above address. All 

comments must be marked Docket No. 

NM400. Comments may be inspected in 

the Rules Docket weekdays, except 

Federal holidays, between 7:30 a.m. and 

4 p.m. 

FOR FURTHER INFORMATION CONTACT: 

Mark Freisthler, FAA, Airframe & 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) 227–1149. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

The FAA invites interested persons to 

participate in this rulemaking by 

submitting written comments, data, or 

views. The most helpful comments 

reference a specific portion of the 

proposed special conditions, explain the 

reason for any recommended change, 

and include supporting data. We ask 

that you send us two copies of written 

comments. 

We will file in the docket all 

comments we receive as well as a report 

summarizing each substantive public 

contact with FAA personnel concerning 

these proposed special conditions. The 

docket is available for public inspection 

before and after the comment closing 

date. If you wish to review the docket 

in person, go to the address in the 

ADDRESSES section of this notice 

between 7:30 a.m. and 4 p.m., Monday 

through Friday, except Federal holidays. 

We will consider all comments we 

receive on or before the closing date for 

comments. We will consider comments 

filed late if it is possible to do so 

without incurring expense or delay. We 

may change the proposed special 

conditions based on comments we 

receive. 

If you want the FAA to acknowledge 

receipt of your comments on this 

proposal, include with your comments 

a pre-addressed, stamped postcard on 

which the docket number appears. We 

will stamp the date on the postcard and 

mail it back to you. 

Background 

On November 4, 2005, The Boeing 

Company, PO Box 3707, Seattle, WA 

98124, applied for an amendment to 

Type Certificate Number A20WE to 

include the new Model 747–8 passenger 

airplane and the new Model 747–8F 

freighter airplane. The Model 747–8 and 

the Model 747–8F are derivatives of the 

747–400 and the 747–400F, 

respectively. Both the Model 747–8 and 

the Model 747–8F are four-engine jet 

transport airplanes that will have a 

maximum takeoff weight of 970,000 

pounds and new General Electric GEnx– 

2B67 engines. The Model 747–8 will 

have two flight crew and the capacity to 

carry 660 passengers. The Model 747– 

8F will have two flight crew and a zero 

passenger capacity, although Boeing has 

submitted a petition for exemption to 

allow the carriage of supernumeraries. 

Type Certification Basis 

Under the provisions of § 21.101, 

Boeing must show that Models 747–8 

and 747–8F (hereafter referred as 747– 

8/–8F) meet the applicable provisions of 

part 25, as amended by Amendments 

25–1 through 25–117, except for earlier 

amendments as agreed upon by the 

FAA. These regulations will be 

incorporated into Type Certificate No. 

A20WE after type certification approval 

of the 747–8/–8F. 

In addition, the certification basis 

includes other regulations, special 

conditions and exemptions that are not 

relevant to these proposed special 

conditions. Type Certificate No. A20WE 

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 747–8/–8F because of a novel or 

unusual design feature, special 

conditions are prescribed under the 

provisions of § 21.16. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the 747–8/–8F 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. 

Special conditions, as defined in 

§ 11.19, are issued under § 11.38, and 

become part of the type certification 

basis under § 21.101. 

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. 

Novel or Unusual Design Features 

The Boeing Model 747–8/8F is 

equipped with systems that affect the 

airplane’s structural performance, either 

directly or as a result of failure or 

malfunction. That is, the airplane’s 

systems affect how it responds in 

maneuver and gust conditions, and 

thereby affect its structural capability. 

These systems may also affect the 

aeroelastic stability of the airplane. 

Such systems represent a novel and 

unusual feature when compared to the 

technology envisioned in the current 

airworthiness standards. A special 

condition is needed to require 

consideration of the effects of systems 

on the structural capability and 

aeroelastic stability of the airplane, both 

in the normal and in the failed state. 

This special condition requires that 

the airplane meet the structural 

requirements of subparts C and D of 14 

CFR part 25 when the airplane systems 

are fully operative. The special 

condition also requires that the airplane 

meet these requirements considering 

failure conditions. In some cases, 


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reduced margins are allowed for failure 

conditions based on system reliability. 

Applicability 

As discussed above, this proposed 

special condition is applicable to Boeing 

Model 747–8/–8F airplanes. Should 

Boeing apply at a later date for a change 

to the type certificate to include another 

model incorporating the same novel or 

unusual design features, this proposed 

special condition would apply to that 

model as well under the provisions of 

§ 21.101. 

Conclusion 

This action affects only certain novel 

or unusual design features of the Boeing 

Model 747–8/–8F 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 this 

proposed Special Condition is as 

follows: 

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

44702, 44704. 

The Proposed Special Conditions 

Accordingly, pursuant to the 

authority delegated to me by the 

Administrator, the Federal Aviation 

Administration (FAA) proposes the 

following special condition as part of 

the type certification basis for the 747– 

8/–8F airplanes. 

A. General 

The Boeing Model 747–8/8F airplane 

is equipped with automatic control 

systems that affect the airplane’s 

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 Subparts C and D of 

part 25. The following criteria must be 

used for showing compliance with this 

proposed special condition for airplanes 

equipped with flight control systems, 

autopilots, stability augmentation 

systems, load alleviation systems, flutter 

control systems, fuel management 

systems, and other systems that either 

directly or as a result of failure or 

malfunction affect structural 

performance. If this proposed special 

condition is used for other systems, it 

may be necessary to adapt the criteria to 

the specific system. 

1. The criteria defined here 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 

this proposed special condition. 

2. Depending on the specific 

characteristics of the airplane, 

additional studies may be required that 

go beyond the criteria provided in this 

proposed special condition in order to 

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. 

3. The following definitions are 

applicable to this proposed special 

condition. 

(a) Structural performance: Capability 

of the airplane to meet the structural 

requirements of part 25. 

(b) 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 (AFM) (e.g., 

speed limitations, avoidance of severe 

weather conditions, etc.). 

(c) 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 (MMEL) 

limitations). 

(d) Probabilistic terms: The 

probabilistic terms (probable, 

improbable, extremely improbable) used 

in this proposed special condition are 

the same as those used in § 25.1309. 

(e) Failure condition: The term failure 

condition is the same as that used in 

§ 25.1309, however this proposed 

special condition applies 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 condition includes 

consequential or cascading effects 

resulting from the first failure. 

B. Effects of Systems on Structures 

1. General. The following criteria will 

be used in determining the influence of 

a system and its failure conditions on 

the airplane structural elements. 

2. System fully operative. With the 

system fully operative, the following 

apply: 

(a) Limit loads must be derived in all 

normal operating configurations of the 

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 displacement of 

control surface, thresholds or any other 

system nonlinearities) must be 

accounted for in a realistic or 

conservative way when deriving limit 

loads from limit conditions. 

(b) 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. 

(c) The airplane must meet the 

aeroelastic stability requirements of 

§ 25.629. 

3. System in the failure condition. For 

any system failure condition not shown 

to be extremely improbable, the 

following apply: 

(a) 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. 

(1) 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 (F.S.) is 

defined in Figure 1. 


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(2) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in subparagraph 3(a)(1). 

For pressurized cabins, these loads must 

be combined with the normal operating 

differential pressure. 

(3) 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. 

(4) Failures of the system that result 

in forced structural vibrations 

(oscillatory failures) must not produce 

loads that could result in detrimental 

deformation of the affected structural 

elements. 

(b) For continuation of flight, for an 

airplane in the system failed state and 

considering any appropriate 

reconfiguration and flight limitations, 

the following apply: 

(1) 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: 

(i) The limit symmetrical 

maneuvering conditions specified in 

§ 25.331 and in § 25.345. 

(ii) The limit gust and turbulence 

conditions specified in § 25.341 and in 

§ 25.345. 

(iii) The limit rolling conditions 

specified in § 25.349 and the limit 

unsymmetrical conditions specified in 

§§ 25.367 and 25.427(b) and (c). 

(iv) The limit yaw maneuvering 

conditions specified in § 25.351. The 

limit ground loading conditions 

specified in §§ 25.473, 25.491 and 

25.493. 

(2) For static strength substantiation, 

each part of the structure must be able 

to withstand the loads in paragraph 

(3)(b)(1) of the proposed special 

condition 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. 

(3) For residual strength 

substantiation, the airplane must be able 

to withstand two thirds of the ultimate 

loads defined in paragraph (3)(b)(1) of 

the proposed special condition. For 

pressurized cabins, these loads must be 

combined with the normal operating 

differential pressure. 


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(4) 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. 

(5) 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 

for the remainder of the flight using the 

margins defined by § 25.629(b). 

(6) 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). 

(a) 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. 

4. Failure indications. For system 

failure detection and indication, the 

following apply: 

(a) The 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 control 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 

Certification Maintenance Requirements 

(CMRs) 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. 

(b) 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, 

must be signaled to the flight crew. For 

example, 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′′, 

must be signaled to the crew during 

flight. 

5. Dispatch with known failure 

conditions. If the airplane is to be 

dispatched in a known system failure 

condition that affects structural 

performance, or affects the reliability of 

the remaining system to maintain 

structural performance, then the 

provisions of this proposed special 

condition must be met, including the 

provisions of paragraph 2 for the 

dispatched condition, and paragraph 3 

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 January 

22, 2009. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E9–7882 Filed 4–7–09; 8:45 am] 

BILLING CODE 4910–13–P 


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