# Airworthiness Directives; Boeing Model 747 Series Airplanes, Excluding Airplanes Equipped with Pratt & Whitney PW4000 and General Electric CF6-80C2 Series Engines

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URL: https://www.frixlaw.com/law-library/documents/fr%3A94-27852

## Record

- **Collection:** Federal Register
- **Document type:** Uncategorized Document
- **Published:** November 10, 1994

## Text

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-123-AD]

Airworthiness Directives; Boeing Model 747 Series Airplanes,
Excluding Airplanes Equipped with Pratt & Whitney PW4000 and General
Electric CF6-80C2 Series 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 replacement of certain fuse pins
on the upper link of the inboard and outboard struts. This AD also
would require inspections to detect corrosion or cracks of certain fuse
pins, and replacement, if necessary. This proposal is prompted by
reports of cracked or corroded fuse pins on the upper link of the
inboard and outboard struts, which could result in fracturing of the
pins. The actions specified by the proposed AD are intended to prevent
failure of the strut and separation of an engine from the airplane due
to fracturing of the fuse pins.

DATES: Comments must be received by January 10, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-123-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: Tim Backman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2776; 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-123-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-123-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.

Discussion -

The FAA received several reports of cracked fuse pins on the upper
link of the inboard and outboard struts on Boeing Model 747 series
airplanes. Several pins also showed evidence of corrosion. The fuse
pins involved in these reports were ``bottle bore style'' fuse pins
installed in the forward position of the struts. The cracking initiated
in a machining groove in the inner recess of the pin bore, and it
propagated due to fatigue. Cracking of the pins occurred on some
airplanes as early as 9,366 total flight cycles (on the airplane) and
42,493 total flight hours. One of the reports involved the complete
fracture of both shear planes on the fuse pin; consequently, that pin
had no load carrying capability. Analysis of several of the cracked
fuse pins indicated that fracturing occurred in the recess area of the
pin bore. -
Corrosion may cause cracking of the fuse pins; this could lead to
fracturing of the fuse pins. This condition, if not corrected, could
result in failure of the strut and separation of an engine from the
airplane. -
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-54A2166, dated April 28, 1994, which describes procedures for
replacement of ``bulkhead style'' and ``bottle bore style'' fuse pins,
installed in the forward position of the upper link on the inboard and
outboard struts, with either a 15-5 corrosion-resistant steel fuse pin
(also known as a ``third generation'' pin) or a new bulkhead style pin.
(This alert service bulletin specifies that installation of the third
generation pin is preferred.) The alert service bulletin also describes
procedures for repetitive detailed visual inspections to detect
corrosion of the bulkhead style pins; magnetic particle inspections to
detect cracks in these pins; and replacement of any cracked or corroded
pin with a third generation pin or a new bulkhead style pin. -
The alert service bulletin references Boeing Service Bulletin 747-
54-2155, dated September 23, 1993, as an additional source of service
information for replacement of certain fuse pins, installed in the
forward and aft positions of the upper link, with third generation
pins. (Although there have been no reports of cracked pins in the aft
position, replacement of the pin in the forward position with a third
generation pin necessitates that the aft pin also be replaced with a
third generation pin in order to preserve the function and location of
the primary structural fuse.) -
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 replacement of bottle bore style fuse pins,
installed in the forward position of the upper link on the inboard and
outboard struts, with either third generation fuse pins or new bulkhead
style pins. This proposed AD also would require repetitive detailed
visual inspections to detect corrosion of bulkhead style fuse pins;
magnetic particle inspections to detect cracks in those pins; and
replacement of any corroded or cracked bulkhead style fuse pin with a
third generation fuse pin or with a new bulkhead style pin.
Installation of a third generation fuse pin, if accomplished, would
constitute terminating action for the inspection requirements of the
proposed AD. The actions would be required to be accomplished in
accordance with the alert service bulletin described previously. -
The manufacturer has advised that it is currently developing a
modification program for the engine strut that will positively address
the unsafe condition addressed by this AD. Once this modification
program is developed, approved, and available, the FAA may consider
additional rulemaking.
There are approximately 869 Model 747 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 147
airplanes of U.S. registry would be affected by this proposed AD. -
It would take approximately 122 work hours per airplane to
accomplish the proposed replacement of fuse pins with bulkhead style
pins. The average labor rate is $60 per work hour. Based on these
figures, the total cost impact on U.S. operators who replace fuse pins
with bulkhead style pins is estimated to be $7,320 per airplane. -
It would take approximately 140 work hours per airplane to
accomplish the proposed replacement of fuse pins with third generation
pins. The average labor rate is $60 per work hour. Based on these
figures, the total cost impact on U.S. operators who replace fuse pins
with third generation pins is estimated to be $8,400 per airplane. -
It would take approximately 1.5 work hours per airplane to
accomplish the proposed inspections (in addition to the work hours
necessary for fuse pin replacement). The average labor rate is $60 per
work hour. Based on these figures, the total cost impact on U.S.
operators for the proposed inspections is estimated to be $90 per
airplane per inspection. -
The cost of required replacement parts would vary from airplane to
airplane, depending upon the current airplane configuration. -
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 number of required work hours, as indicated above, is presented
as if the accomplishment of the proposed inspection and replacement
actions were to be conducted as ``stand alone'' actions. However, in
actual practice, these actions, for the most part, would be
accomplished coincidentally or in combination with normally scheduled
airplane inspections and other maintenance program tasks. Therefore,
the actual number of necessary additional work hours would be minimal
in many instances. Additionally, any costs associated with special
airplane scheduling would be minimal. -
The FAA recognizes that the obligation to maintain aircraft in an
airworthy condition is vital, but sometimes expensive. Because AD's
require specific actions to address specific unsafe conditions, they
appear to impose costs that would not otherwise be borne by operators.
However, because of the general obligation of operators to maintain
aircraft in an airworthy condition, this appearance is deceptive.
Attributing those costs solely to the issuance of this AD is
unrealistic because, in the interest of maintaining safe aircraft,
prudent operators would accomplish the required actions even if they
were not required to do so by the AD. -
A full cost-benefit analysis has not been accomplished for this
proposed AD. As a matter of law, in order to be airworthy, an aircraft
must conform to its type design and be in a condition for safe
operation. The type design is approved only after the FAA makes a
determination that it complies with all applicable airworthiness
requirements. In adopting and maintaining those requirements, the FAA
has already made the determination that they establish a level of
safety that is cost-beneficial. When the FAA, as in this proposed AD,
makes a finding of an unsafe condition, this means that the original
cost-beneficial level of safety is no longer being achieved and that
the proposed actions are necessary to restore that level of safety.
Because this level of safety has already been determined to be cost-
beneficial, a full cost-benefit analysis for this proposed AD would be
redundant and unnecessary. -
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-123-AD.

Applicability: Model 747 series airplanes; line numbers 1
through 967 inclusive, and 969 through 992 inclusive; excluding
airplanes equipped with Pratt & Whitney PW4000 or General Electric
CF6-80C2 series engines; certificated in any category.

Note 1: This AD does not require that the actions be
accomplished on the struts of airplanes having straight bore fuse
pins (installed on Model 747 series airplanes equipped with Pratt &
Whitney PW4000 or General Electric CF6-80C2 series engines) or 15-5
corrosion resistant steel (third generation) fuse pins.

Compliance: Required as indicated, unless accomplished
previously.
To prevent failure of the strut and loss of an engine due to
corrosion or cracking of the fuse pins, accomplish the following:
(a) For airplanes having bottle bore style fuse pins in the
forward position on the upper link: Replace any bottle bore style
fuse pin with a new bulkhead style fuse pin in the forward position,
or with 15-5 corrosion resistant steel (third generation) fuse pins
in the forward position, in accordance with Boeing Alert Service
Bulletin 747-54A2166, dated April 28, 1994, at the later of the
times specified in paragraphs (a)(1) and (a)(2) of this AD.
(1) Prior to the accumulation of 5,000 landings on the fuse pin,
or within 5 years since installation of the pin, whichever occurs
first. Or
(2) Within 6 months after the effective date of this AD.

Note 2: Third generation fuse pins are installed in pairs (in
the forward and aft positions). Therefore, replacement of an
individual upper link fuse pin in the forward position with a third
generation pin also would necessitate replacement of the pin in the
aft position.
Note 3: The alert service bulletin references Boeing Service
Bulletin 747-54-2155, dated September 23, 1993, as an additional
source of service information for replacement of the fuse pins with
15-5 corrosion resistant steel (third generation) fuse pins.
Installation of these third generation fuse pins is preferred over
installation of bulkhead style fuse pins.

(b) For airplanes having bulkhead style fuse pins in the forward
position on the upper link: Perform a detailed visual inspection to
detect corrosion of the pins, and a magnetic particle inspection to
detect cracks, in accordance with Boeing Alert Service Bulletin 747-
54A2166, dated April 28, 1994, at the later of the times specified
in paragraphs (b)(1) and (b)(2) of this AD.
(1) Prior to the accumulation of 8,000 landings on the fuse pin,
or within 8 years since installation of the pin, whichever occurs
first. Or
(2) Within 12 months after the effective date of this AD.
(c) If no corrosion or crack is found during the inspection
required by paragraph (b) of this AD, repeat the inspections
thereafter at the intervals specified in paragraph (c)(1) or (c)(2)
of this AD, as applicable.
(1) For the inboard and outboard struts on airplanes other than
those identified in paragraph (c)(2) of this AD: Repeat the
inspections at intervals not to exceed 1,000 landings.
(2) For the outboard struts on airplanes equipped with Rolls-
Royce RB211-524G or -524H series engines: Repeat the inspections at
intervals not to exceed 2,000 landings.

Note 4: The outboard struts of airplanes equipped with Rolls-
Royce RB211-524G or -524H series engines are equipped with thick
wall ``4330 steel'' bulkhead style fuse pins in the forward position
of the upper link. Crack propagation to critical length in these
thick wall pins is slower than for pins installed on the struts of
airplanes equipped with engines other than the Rolls-Royce RB211-
524G or -524H series.

(d) If any corrosion or crack is found during any inspection
required by this AD, prior to further flight, replace the corroded
or cracked pin with either a new bulkhead style fuse pin in the
forward position of the upper link, or with 15-5 corrosion resistant
steel (third generation) fuse pins in the forward and aft positions
of the upper link, in accordance with Boeing Alert Service Bulletin
747-54A2166, dated April 28, 1994.
(1) If the corroded or cracked fuse pin is replaced with a new
bulkhead style fuse pin, prior to the accumulation of 8,000 landings
on the new pin, or within 8 years since installation of the new pin,
whichever occurs first, perform a detailed visual inspection to
detect corrosion of the new pin, and a magnetic particle inspection
to detect cracks of the new pin, in accordance with Boeing Alert
Service Bulletin 747-54A2166, dated April 28, 1994. Repeat these
inspections thereafter at the interval specified in paragraph
(d)(1)(i) or (d)(1)(ii) of this AD, as applicable.
(i) For the inboard and outboard struts on airplanes other than
those identified in paragraph (d)(1)(ii) of this AD: Repeat the
inspections at intervals not to exceed 1,000 landings.
(ii) For the outboard struts on airplanes equipped with Rolls-
Royce RB211-524G or -524H series engines: Repeat the inspections at
intervals not to exceed 2,000 landings.
(2) If the corroded or cracked fuse pin is replaced with a 15-5
corrosion resistant steel (third generation) fuse pin, no further
action is required by this AD.
(e) Installation of 15-5 corrosion resistant steel (third
generation) fuse pins in the forward and aft positions of the upper
link on the inboard or outboard strut constitutes terminating action
for the requirements of this AD.
(f) 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 5: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.

(g) 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 November 4, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-27852 Filed 11-9-94; 8:45 am]
BILLING CODE 4910-13-U

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A94-27852. Public record. Not legal advice.