This section of the FEDERAL REGISTER

contains notices to the public of the proposed

issuance of rules and regulations. The

purpose of these notices is to give interested

persons an opportunity to participate in the

rule making prior to the adoption of the final

rules.

Proposed Rules Federal Register

15888 

Vol. 74, No. 66 

Wednesday, April 8, 2009 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. NM399 Special Conditions No. 

25–09–02–SC] 

Special Conditions: Boeing Model 747– 

8/–8F Airplane, Additional Airframe 

Structural Design Requirements 

Related to Sudden Engine Stoppage 

Due to Fan Blade Failures 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed special 

conditions. 

SUMMARY: This document 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 larger engines with 

large bypass fans capable of producing 

much larger and more complex dynamic 

loads. 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. NM399, 

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. 

NM399. 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 14 CFR 

21.101, Boeing must show that the 

Model 747–8 and 747–8F airplanes 

(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 


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Federal Register / Vol. 74, No. 66 / Wednesday, April 8, 2009 / Proposed Rules 15889 

conditions would also apply to the other 

model under § 21.101. 

Novel or Unusual Design Features 

The Boeing Model 747–8/–8F airplane 

will incorporate the following novel or 

unusual design features: high-bypass 

engines with a fan diameter 

approximately twelve percent greater 

than those currently installed on other 

Boeing Model 747 airplanes. 

Discussion 

High-bypass engines with a fan 

diameter approximately twelve percent 

greater than those currently installed on 

other Boeing Model 747 airplanes, such 

as the 747–400 series were not 

envisioned when § 25.361 was adopted 

in 1965. Section 25.361 addresses loads 

imposed by engine seizure. Because of 

the higher inertia of the rotating 

components, worst case engine seizure 

events become increasingly more severe 

with increasing engine size. 

Typically the design torque loads 

associated with typical failure scenarios 

have been estimated by the engine 

manufacturer. These loads are used by 

the airframe manufacturer as limit 

loads. Section 25.305 requires that 

supporting structure be able to support 

limit loads without detrimental 

permanent deformation, meaning that 

supporting structure should remain 

serviceable after a limit load event. 

Limit loads are expected to occur about 

once in the lifetime of any airplane. For 

turbine engine installations, 

§ 25.361(b)(1) requires that the engine 

mounts and supporting structures be 

designed to withstand a ‘‘limit engine 

torque load imposed by sudden engine 

stoppage due to malfunction or 

structural failure.’’ 

Since § 25.361(b)(1) was adopted the 

size, configuration, and failure modes of 

turbine engines have changed 

significantly. Current engines are much 

larger and are designed with large 

bypass fans. In the failure event 

prescribed by § 25.361 they produce 

much higher transient loads on the 

engine mounts and supporting structure 

than previous designs. At the same time, 

the likelihood of such an event 

occurring in modern engines has 

become less. The service history of 

modern turbine engines shows that 

engine seizures are rare events, much 

less than what is typically expected for 

‘‘limit’’ loads. While it is important for 

the airplane to be able to support such 

rare loads safely without failure, it is 

unrealistic to expect that no permanent 

deformation will occur. 

Given this situation, the Aviation 

Rulemaking Advisory Committee 

(ARAC) has proposed a design standard 

for today’s large engines. For the 

commonly occurring deceleration 

events, the proposed standard would 

require engine mounts and structures to 

support maximum torques without 

detrimental permanent deformation. For 

the rare-but-severe engine seizure events 

such as loss of any fan, compressor, or 

turbine blade, the proposed standard 

would require engine mounts and 

structures to support maximum torques 

without failure, but allow for some 

deformation in the structure. 

The FAA concludes that modern large 

engines, including those on the 747–8/ 

–8F, are novel and unusual compared to 

those envisioned when § 25.361(b)(1) 

was adopted and thus warrant special 

conditions. These proposed special 

conditions contain design criteria 

recommended by ARAC. 

Applicability 

As discussed above, these proposed 

special conditions are 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, 

these proposed special conditions 

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 these 

proposed Special Conditions 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 conditions as part of 

the type certification basis for the 747– 

8/–8F airplanes. 

In lieu of § 25.361(b) the following 

special conditions are proposed: 

1. For turbine engine installations, the 

engine mounts, pylons and supporting 

airframe primary structure (such as the 

affected wing and fuselage primary 

structure) must be designed to 

withstand 1g level flight loads acting 

simultaneously with the maximum 

torque load, considered as limit load, 

imposed by each of the following: 

(a) Sudden engine deceleration due to 

a malfunction which could result in a 

temporary loss of power or thrust; and 

(b) The maximum acceleration of the 

engine. 

2. For auxiliary power unit 

installations, the power unit mounts 

and supporting airframe primary 

structure (such as the affected fuselage 

primary structure) must be designed to 

withstand 1g level flight loads acting 

simultaneously with the maximum 

torque load, considered as limit load, 

imposed by each of the following: 

(a) Sudden auxiliary power unit 

deceleration due to malfunction or 

structural failure; and 

(b) The maximum acceleration of the 

power unit. 

3. For turbine engine installations, the 

engine mounts, pylons and supporting 

airframe primary structure (such as the 

affected wing and fuselage primary 

structure) must be designed to 

withstand 1g flight loads acting 

simultaneously with the transient 

dynamic loads, considered as ultimate 

load, imposed by each of the following: 

(a) Sudden engine stoppage due to the 

loss of any fan, compressor, or turbine 

blade; and separately 

(b) Where applicable to a specific 

engine design, any other engine 

structural failure that results in higher 

loads. 

4. The ultimate loads developed from 

the conditions specified in paragraphs 

3(a) and 3(b) are to be multiplied by a 

factor of 1.0 when applied to engine 

mounts and pylons and multiplied by a 

factor of 1.25 when applied to the 

supporting airframe primary structure 

(such as the affected wing and fuselage 

primary structure). In addition, the 

airplane must be capable of continued 

safe flight considering the aerodynamic 

effects on controllability due to any 

permanent deformation that results from 

the conditions specified in paragraph 3, 

above. 

Issued in Renton, Washington, on January 

22, 2009. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E9–7909 Filed 4–7–09; 8:45 am] 

BILLING CODE 4910–13–P 


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