[Federal Register Volume 67, Number 139 (Friday, July 19, 2002)]
[Proposed Rules]
[Pages 47490-47491]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-18200]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NM-93-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777-200 Series Airplanes 
Equipped With General Electric Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Proposed rule; withdrawal.

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SUMMARY: This action withdraws a notice of proposed rulemaking (NPRM) 
that proposed a new airworthiness directive (AD), applicable to all 
Boeing Model 777-200 series airplanes equipped with General Electric 
engines. That action would have required installation of a high-
temperature silicone foam seal on the aft fairing of the strut. Since 
issuance of the NPRM, the Federal Aviation Administration (FAA) has 
received new information that indicates that the unsafe condition would 
not be prevented by the proposed action. Subsequently, the FAA has 
issued new rulemaking that positively addresses the unsafe condition 
identified in the NPRM and eliminates the need for the actions proposed 
by the NPRM. Accordingly, the proposed rule is withdrawn.

FOR FURTHER INFORMATION CONTACT: Technical Information: John Vann, 
Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-1024; fax (425) 227-1181.
    Other Information: Judy Golder, Airworthiness Directive Technical 
Editor/Writer; telephone (425) 687-4241, fax (425) 227-1232. Questions 
or comments may also be sent via the Internet using the following 
address: [email protected]. Questions or comments sent via the 
Internet as attached electronic files must be formatted in Microsoft 
Word 97 for Windows or ASCII text.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to add a new airworthiness 
directive (AD), applicable to all Boeing Model 777-200 series airplanes 
equipped with General Electric engines, was published in the Federal 
Register as a Notice of Proposed Rulemaking (NPRM) on October 30, 2001 
(66 FR 54727). The proposed rule would have required installation of a 
high-temperature silicone foam seal on the aft fairing of the strut. 
That action was prompted by reports indicating that, during routine 
inspections of the aft fairing of the strut, evidence of an elevated 
temperature in the interior cavity of the aft fairing was found on 
several Boeing Model 777-200 series airplanes equipped with General 
Electric engines. The proposed actions were intended to prevent primary 
engine exhaust from entering the aft fairing of the strut, elevating 
the temperature in the aft fairing of the strut, and creating a 
potential source of ignition, which could lead to an uncontrolled fire 
in the aft fairing of the strut. Such a fire would expose the wing fuel 
tank to high-temperature gasses and flames and result in a potential 
ignition source for the fuel tank, and reduced structural integrity of 
the wing.

Actions That Occurred Since the NPRM Was Issued

    Since the issuance of that NPRM, one operator reported significant 
heat damage to the forward end of the diagonal brace on an airplane 
that had the high-temperature silicone foam seal installed. 
Investigation revealed that the foam seal was not a sufficient barrier 
to the heat of the primary engine exhaust. Thus the exhaust entered the 
aft fairing of the strut through a gap in the heat shield, elevating 
the temperature and resulting in heat damage to the primary fire seal, 
heat shield seal, and secondary fluid seal. The damaged seals allowed 
the exhaust to pass into the aft fairing cavity causing heat damage to 
the diagonal brace assembly.
    As a result of this incident, the FAA has determined that the 
unsafe condition would not be prevented by the installation of the high 
temperature silicone foam seal alone, which the NPRM proposed to 
require.

Other Relevant Rulemaking

    On March 29, 2002, the FAA issued AD 2002-07-07, amendment 39-12701 
(67 FR 16991, April 9, 2002), applicable to certain Boeing Model 777-
200 series airplanes equipped with General Electric GE90 series 
engines. That AD requires repetitive inspections of the diagonal brace 
and forward seals of the aft fairing of the strut to find 
discrepancies, and corrective actions, if necessary. The actions 
required by that AD are intended to prevent primary engine exhaust from 
entering the aft fairing of the strut and elevating the temperature, 
which could lead to heat damage of the seals and diagonal brace. Such 
damage could result in cracking and fracture of the forward attachment 
point of the diagonal brace, loss of the diagonal brace load path, and 
consequent separation of the strut and engine from the airplane.

FAA's Conclusions

    In AD 2002-07-07, the FAA stated that it was considering 
withdrawing NPRM 2001-NM-93-AD. Upon further consideration, the FAA has 
determined that the unsafe condition addressed by that NPRM would NOT 
be prevented by the actions that would be required by that proposed AD, 
but WOULD be prevented by the actions required by AD 2002-07-07. 
Accordingly, the proposed rule is hereby withdrawn.
    Withdrawal of this NPRM constitutes only such action, and does not 
preclude the agency from issuing another action in the future, nor does 
it commit the

[[Page 47491]]

agency to any course of action in the future.

Regulatory Impact

    Since this action only withdraws a notice of proposed rulemaking, 
it is neither a proposed nor a final rule and therefore is not covered 
under Executive Order 12866, the Regulatory Flexibility Act, or DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Withdrawal

    Accordingly, the notice of proposed rulemaking, Docket 2001-NM-93-
AD, published in the Federal Register on October 30, 2001 (66 FR 
54727), is withdrawn.

    Issued in Renton, Washington, on July 11, 2002.
Lirio Liu-Nelson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-18200 Filed 7-18-02; 8:45 am]
BILLING CODE 4910-13-P