40482 Federal Register / Vol. 74, No. 154 / Wednesday, August 12, 2009 / Rules and Regulations 

V′ = Clearance speed as defined by 

§ 25.629(b)(2). 

V′′ = Clearance speed as defined by 

§ 25.629(b)(1). 

Qj = (Tj)(Pj) where: 

Tj = Average time spent in failure condition 

j (in hours) 

Pj = Probability of occurrence of failure mode 

j (per hour) 

Note: If Pj is greater than 10¥3 per flight 

hour, then the flutter clearance speed must 

not be less than V′′. 

(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). 

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 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 July 29, 

2009. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E9–19246 Filed 8–11–09; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. NM399; Special Conditions No. 

25–387–SC] 

Special Conditions: Boeing Model 747– 

8/–8F Airplanes; Additional Airframe 

Structural Design Requirements 

Related to Sudden Engine Stoppage 

Due to Fan Blade Failures 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final special conditions. 

SUMMARY: These special conditions are 

issued for Boeing Model 747–8/–8F 

airplanes. These airplanes will have a 

novel or unusual design feature(s) 

associated with an increased engine size 

when compared to previous model 

airplanes. These larger engines with 

larger bypass fans are capable of 

producing higher and more complex 

dynamic loads than previously 

experienced in older designs. The 

applicable airworthiness regulations do 

not contain adequate or appropriate 

safety standards for this design feature. 

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: September 11, 

2009. 

FOR FURTHER INFORMATION CONTACT: 

Mark Freisthler, FAA, Airframe & Cabin 


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Federal Register / Vol. 74, No. 154 / Wednesday, August 12, 2009 / Rules and Regulations 40483 

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: 

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 GEnx2B67 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 Title 14 Code 

of Federal Regulations (14 CFR) 21.101, 

Boeing must show that the Model 747– 

8 and 747–8F airplanes (hereafter 

referred to as the 747–8/–8F) as 

changed, continue to meet the 

applicable provisions of 14 CFR 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. 

If the Administrator finds that the 

applicable airworthiness regulations 

(i.e., 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 novel or unusual 

design feature, or should any other 

model already included on the same 

type certificate be modified to 

incorporate the same 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 

airplanes will incorporate the following 

novel or unusual design features: Highbypass 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 special conditions 

contain design criteria recommended by 

the ARAC. 

Discussion of Comments 

Notice of proposed special conditions 

No. 25–09–02–SC for the Boeing Model 

747–8 and 747–8F airplanes was 

published in the Federal Register on 

April 8, 2009 (74 FR 15888). No 

comments were received and the special 

conditions are adopted as proposed. 

Applicability 

As discussed above, these 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, the special 

conditions would apply to that model as 

well. 

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 

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 the Boeing Model 


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40484 Federal Register / Vol. 74, No. 154 / Wednesday, August 12, 2009 / Rules and Regulations 

747–8/–8F airplanes. The following 

special conditions are in lieu of 

§ 25.361(b): 

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 July 29, 

2009. 

Ali Bahrami, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. E9–19249 Filed 8–11–09; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2009–0464; Directorate 

Identifier 2008–NM–189–AD; Amendment 

39–15992; AD 2008–16–09 R1] 

RIN 2120–AA64 

Airworthiness Directives; Short 

Brothers Model SD3–60 Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), Department of 

Transportation (DOT). 

ACTION: Final rule. 

SUMMARY: We are revising an existing 

airworthiness directive (AD) for the 

products listed above. This AD results 

from mandatory continuing 

airworthiness information (MCAI) 

originated by an aviation authority of 

another country to identify and correct 

an unsafe condition on an aviation 

product. The MCAI describes the unsafe 

condition as: 

There have been several occurrences of 

cracked elevator trim tab balance weight 

attachment brackets, on one occasion, the 

elevator trim tab mass balance weight bracket 

separated from the aircraft. The loss of an 

elevator trim tab mass balance weight bracket 

has the potential to cause damage to an 

aircraft, or cause serious injury to personnel. 

* * * * * 

We are issuing this AD to require 

actions to correct the unsafe condition 

on these products. 

DATES: This AD becomes effective 

September 16, 2009. 

The Director of the Federal Register 

previously approved the incorporation 

by reference of certain publications 

listed in this AD as of September 15, 

2008 (73 FR 46543, August 11, 2008). 

The Director of the Federal Register 

previously approved the incorporation 

by reference of a certain publication 

listed in this AD as of March 14, 2005 

(70 FR 9212, February 25, 2005). 

The Director of the Federal Register 

previously approved the incorporation 

by reference of a certain other 

publication listed in this AD as of 

September August 3, 2004 (69 FR 38813, 

June 29, 2004). 

ADDRESSES: You may examine the AD 

docket on the Internet at http:// 

www.regulations.gov or in person at the 

U.S. Department of Transportation, 

Docket Operations, M–30, West 

Building Ground Floor, Room W12–140, 

1200 New Jersey Avenue, SE., 

Washington, DC. 

FOR FURTHER INFORMATION CONTACT: 

Todd Thompson, Aerospace Engineer, 

International Branch, ANM–116, 

Transport Airplane Directorate, FAA, 

1601 Lind Avenue, SW., Renton, 

Washington 98057–3356; telephone 

(425) 227–1175; fax (425) 227–1149. 

SUPPLEMENTARY INFORMATION: 

Discussion 

We issued a notice of proposed 

rulemaking (NPRM) to amend 14 CFR 

part 39 to include an AD to revise AD 

2008–16–09, amendment 39–15627 (73 

FR 46543, August 11, 2008). The 

existing AD applies to the products 

identified in this AD. The NPRM was 

published in the Federal Register on 

May 20, 2009 (74 FR 23668). That 

NPRM proposed to correct an unsafe 

condition for the specified products. 

Since we issued AD 2008–16–09, 

Short Brothers advised that SD3–07– 

6011xA brackets manufactured in 2005 

or later have a life limit of 28,800 flight 

hours, per Section 5–00–02 of the Short 

Brothers SD360 Aircraft Maintenance 

Manual (AMM), and as noted in 

Appendix 1 of Shorts Alert Service 

Bulletin SD360–55–A21, Revision 1, 

dated March 29, 2007. In light of this, 

we have revised the existing AD to 

extend the life limit of any balance 

weight bracket from 1,750 flight hours 

to 28,800 flight hours. You may obtain 

further information by examining 

European Aviation Safety Agency 

Airworthiness Directive 2007–0107–E, 

dated April 18, 2007 (referred to after 

this as ‘‘the MCAI’’), in the AD docket. 

In addition, we removed paragraphs 

(f) and (l)(1) of the existing AD from this 

AD. Those paragraphs defined the use of 

the term ‘‘service bulletin,’’ as used in 

the AD. 

Comments 

We gave the public the opportunity to 

participate in developing this AD. We 

received no comments on the NPRM or 

on the determination of the cost to the 

public. 

Conclusion 

We reviewed the available data and 

determined that air safety and the 

public interest require adopting the AD 

as proposed. 

Differences Between This AD and the 

MCAI or Service Information 

We have reviewed the MCAI and 

related service information and, in 

general, agree with their substance. But 

we might have found it necessary to use 

different words from those in the MCAI 

to ensure the AD is clear for U.S. 

operators and is enforceable. In making 

these changes, we do not intend to differ 

substantively from the information 


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