# Airworthiness Directives; Boeing Model 747 Series Airplanes Equipped With General Electric CF6-80C2 Engines

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URL: https://www.frixlaw.com/law-library/documents/fr%3A94-24873

## Record

- **Collection:** Federal Register
- **Document type:** Uncategorized Document
- **Published:** October 7, 1994

## Text

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).
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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

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A94-24873. Public record. Not legal advice.