[Federal Register Volume 59, Number 194 (Friday, October 7, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-24873]


[[Page Unknown]]

[Federal Register: October 7, 1994]


=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-119-AD]
 

Airworthiness Directives; Boeing Model 747 Series Airplanes 
Equipped With General Electric CF6-80C2 Engines
AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes. This proposal would require modification of the fire 
extinguishing system in the number two engine strut. This proposal is 
prompted by reports of chafing of the fire extinguishing tubes in a 
certain inboard strut to wing area. The actions specified by the 
proposed AD are intended to prevent chafing of the fire extinguishing 
tube; such chafing could cause cracking of the tube and consequently 
produce a hole in the fire extinguishing tube, which could prevent the 
proper distribution of the fire extinguisher agent within the nacelle 
in the event of a fire.

DATES: Comments must be received by December 5, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-119-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT:
Tamra Elkins, Aerospace Engineer, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2669; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION:
Comments Invited
    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 94-NM-119-AD.'' The 
postcard will be date stamped and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 94-NM-119-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On June 17, 1992, the FAA issued AD 92-14-07, amendment 39-8289 (57 
FR 31433, July 16, 1994), applicable to certain Boeing Model 747 series 
airplanes, to require repetitive inspections to detect damage of the 
tubes of the engine fire extinguishing system in the number two and 
number three engine struts; replacement or repair, if necessary; and 
reorientation of the clamp. That Ad also requires modification of the 
engine fire extinguishing system in the number two and number three 
engine struts, which, when accomplished, terminates the inspection 
requirements. The modification was required to be accomplished on all 
affected airplanes no later than February 20, 1993. That action was 
prompted by multiple reports of the support clamps in the number two 
and number three engine struts chafing a hole in the tubes of the 
engine fire extinguishing system. The requirements of that AD are 
intended to prevent inadequate distribution of the fire extinguishing 
agent within the nacelle in the event of a fire.
    Since the issuance of that AD, the FAA has received reports of 
chafing of the tubes and/or cracking of the rubber blocks that are an 
integral part of the clamps in the inboard strut to wing area in the 
number two engine strut. (The tube and the rubber blocks were installed 
as part of the modification required by AD 92-14-07.) As a result of 
the chafing, one of the tubes on one airplane cracked approximately six 
inches from the forward end. Investigation revealed that the cracked 
tube had a notch near the cracked area of the tube that had been formed 
due to contact with a ground stud. This notch may have initiated the 
crack in the tube. Further investigation revealed that the rubber 
blocks, which support the tubes, were cracked between the stand-off 
spacers and the tubes.
    The cause of such chafing and cracking has been attributed to 
movement between the spacer and the tube. This movement exceeded the 
flexibility of the rubber and stressed the rubber block, which 
subsequently pinched and tore the rubber block of the clamp. Such 
pinching and tearing could cause the clamp to fail and could lead to 
chafing of the fir extinguishing tube.
    Chafing of the fire extinguishing tube, if not corrected, could 
result in cracking of the fire extinguishing tube and consequently 
produce a hole in the fire extinguishing tube, which could prevent the 
proper distribution of the fire extinguishing agent within the nacelle 
in the event of a fire.
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-26A2226, dated June 30, 1994, which describes procedures for 
modification of the fire extinguishing system in the number two engine 
strut. This modification entails removing and replacing the fire 
extinguishing tube with a new, improved tube (for Group 1 and 2 
airplanes); removing and reinstalling the existing fire extinguishing 
tube (for Group 3 airplanes); and replacing the channel and rubber 
blocks; and reworking the forward bracket (for Group 1, 2, and 3 
airplanes). This modification would revise the geometry of the rubber 
block and the tube, which would increase the flexibility of the rubber 
block and would increase the clearance between the tube and the 
adjacent ground studs.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require modification of the fire extinguishing system 
in the number two engine strut. The actions would be required to be 
accomplished in accordance with the alert service bulletin described 
previously.
    There are approximately 145 Boeing Model 747 series airplanes 
equipped with General Electric CF6-80C2 engines of the affected design 
in the worldwide fleet. The FAA estimates that 2 airplanes of U.S. 
registry would be affected by this proposed AD, that it would take 
approximately 3 work hours per airplane to accomplish the proposed 
actions, and that the average labor rate is $55 per work hour. Required 
parts would be supplied by the manufacturer at no cost to the 
operators. Based on thee figures, the total cost impact of the proposed 
AD on U.S. operators is estimated to be $330, or $165 per airplane.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 94-NM-119-AD.

    Applicability: Model 747 series airplanes equipped with General 
Electric CF6-80C2 engines; as listed in Boeing Alert Service 
Bulletin 747-26A2226, dated June 30, 1994; certificated in any 
category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To ensure proper distribution of the fire extinguisher agent 
within the nacelle in the event of a fire, accomplish the following:
    (a) Within 6 months after the effective date of this AD, modify 
the fire extinguishing system in the number two engine strut, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-26A2226, dated June 30, 1994.
    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (c) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on October 3, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-24873 Filed 10-6-94; 8:45 am]
BILLING CODE 4910-13-P