[Federal Register Volume 61, Number 193 (Thursday, October 3, 1996)]
[Proposed Rules]
[Pages 51621-51624]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-25306]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 96-NM-78-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 727 Series Airplanes
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 all Boeing Model 727 series
airplanes. This proposal would require a one-time visual inspection of
the manual extension gearbox assembly of the main landing gear (MLG) to
detect whether certain gearbox housings have been installed; repetitive
dye penetrant inspections of these housings to determine whether
cracking has occurred; and ultimately, replacement of these housings
with correct housings. This proposal is prompted by a report indicating
that a manual gearbox assembly which contained an incorrect housing was
installed on a Model 727 series airplane. The actions specified by the
proposed AD are intended to prevent the installation of manual
extension gearbox assemblies with incorrect housings. This condition,
if not corrected, could reduce the structural integrity of the manual
extension gearbox assembly, and ultimately result in an inability to
lock the MLG in a down position during landing.
DATES: Comments must be received by November 12, 1996.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
[[Page 51622]]
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 96-NM-78-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: Elizabeth Gnehm, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-1426;
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 96-NM-78-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. 96-NM-78-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA received a report indicating that the manual extension
gearbox assembly for the main landing gear (MLG) on a Model 727 series
airplane had been replaced with a modified gearbox assembly that did
not comply with Airworthiness Directive (AD) 79-04-01 R3, amendment 39-
4000 (45 FR 84014, December 22, 1980). Among other things, that AD
requires replacement of the left and right gearbox housing assemblies
having Boeing part number (P/N) 65-27485-1 and P/N 65-27485-2 with
improved assemblies having P/N 65-27485-11 and P/N 65-27485-12,
respectively; the replacement must be accomplished in accordance with
Boeing Service Bulletin 727-32-279, dated June 22, 1979. That AD was
prompted by reports of corrosion cracking found in the vertical support
attaching lugs of the MLG manual extension-gearbox housings. The
requirements of the AD are intended to prevent such cracking from
resulting in loss of support for the manual extension gearbox and the
consequent inability to manually lock the MLG in the down position.
A subsequent inspection of the incident airplane's maintenance
documents showed that the gearbox assembly installed on the airplane
had been repaired in accordance with Boeing Overhaul Manual 32-35-01
(``Landing Gear Manual Extension Gearbox Assembly''). Although that
manual stated that the text of Boeing Service Bulletin 727-32-279 had
been incorporated into it, the manual, in fact, did not contain
information from the service bulletin which would have ensured that
gearbox assemblies installed on Model 727 series airplanes contained
the housings required by AD 79-04-01 R3. (The manual has since been
revised to incorporate that information.) Consequently, one of the
housings in the modified gearbox assembly did not comply with the
requirements of the AD.
Based on this incident, and the fact that the manufacturer's
overhaul manual contained incomplete information for a period of time,
the FAA has reason to conclude that there currently may be other Model
727 series airplanes in service that are operating with incorrect
gearbox housings/housing assemblies installed. Furthermore, some of
these housings may be cracked.
This condition, if not corrected, can reduce the structural
integrity of the manual system for extending the MLG, and ultimately
could result in the inability of the flight crew to lock the MLG in the
down position during landing.
Explanation of Relevant Service Information
The FAA previously reviewed and approved Boeing Service Bulletin
727-32-279, dated June 22, 1979, which describes procedures for
inspecting the manual extension gearbox assembly of the MLG, and
modifying the assembly by replacing the left and right housings with
improved housings. The service bulletin also describes procedures for
conducting dye penetrant inspections of the housings to detect cracks.
Explanation of Requirements of Proposed Rule
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 a one-time visual inspection of the manual
extension gearbox assembly of the MLG to detect whether this assembly
contains the correct left and right gearbox housings/housing
assemblies. (A housing assembly is composed of a housing and a NAS75-3-
007 bushing.) The incorrect housings/housing assemblies are indicated
as Boeing Part Numbers (P/N):
------------------------------------------------------------------------
Housing
Housing assembly
------------------------------------------------------------------------
65-27485-3.............................................. 65-27485-1
65-27485-4.............................................. 65-27485-2
65-27485-9.............................................. 65-27485-7
65-27485-10............................................. 65-27485-8
------------------------------------------------------------------------
If any incorrect housing/housing assembly is detected by the visual
inspection, the proposed AD would require a dye penetrant inspection of
the incorrect housing to detect cracking. Any cracked housing would be
required to be replaced immediately. The proposal would allow an
uncracked, incorrect housing/housing assembly to be reinstalled,
provided that another dye penetrant inspection of this housing is
accomplished 9 months later; thereafter, the housing would be required
to be replaced with a housing that meets the requirements of AD 79-04-
01 R3 within 18 months after the initial dye penetrant inspection.
All proposed actions would be required to be accomplished in
accordance with the service bulletin described previously.
Differences Between Proposed AD and Service Information
Boeing Service Bulletin 727-32-279 provides for a housing subjected
to dye
[[Page 51623]]
penetrant inspection to continue to be used if cracking is found and
the cracking is within certain parameters. However, the proposed AD
would prohibit the continued use of a housing that contains any
cracking.
The service bulletin also provides for repetitive dye penetrant
inspections to be performed every 3,000 landings. However, the proposed
AD would require these inspections to be performed within 9 months
after the initial dye penetrant inspection. In establishing this 9-
month inspection cycle, the FAA considered that:
1. The cause of cracking was stress corrosion (which is unrelated
to the number of landings);
2. Aging of the housings increases the potential for cracking, and
3. The housings are part of a back-up system which is used only
when the primary system fails.
Based on these considerations, the FAA determined that the proposed
9-month cycle for dye penetrant inspections is appropriate.
Further, in establishing the compliance time for the ultimate
replacement of uncracked, incorrect housings, the FAA considered not
only the safety implications, but also the availability of an ample
number of correct housings that may be necessary for the affected
fleet.
Cost Impact
There are approximately 1,560 Boeing Model 727 series airplanes of
the affected design in the worldwide fleet. The FAA estimates that
1,054 airplanes of U.S. registry would be affected by this proposed AD,
that it would take approximately 2 work hours per airplane to
accomplish the proposed one-time visual inspection, and that the
average labor rate is $60 per work hour. Based on these figures, the
cost impact of the proposed visual inspection on U.S. operators is
estimated to be $126,480, or $120 per airplane.
Should a dye penetrant inspection need to be performed, the FAA
estimates that each inspection would take approximately 20 work hours
per airplane, and the average labor rate is $60 per work hour. Based on
these figures, the cost impact of the proposed dye penetrant inspection
on U.S. operators is estimated to be $1,200 per airplane, per
inspection.
Should parts have to be replaced, the FAA estimates that it would
take approximately 16 work hours per airplane to accomplish the
replacement, and the average labor rate is $60 per work hour.
Replacement parts would cost approximately $4,000 per housing. Based on
these figures, the cost impact of replacement of parts on U.S.
operators is estimated to be $4,960 per airplane if one housing is to
be replaced, and $8,960 if both housings are to be replaced.
The cost impact figures discussed above are 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.
Regulatory Impact
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. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Boeing: Docket 96-NM-78-AD.
Applicability: All Model 727 series airplanes, certificated in
any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
otherwise modified, altered, or repaired in the area subject to the
requirements of this AD. For airplanes that have been modified,
altered, or repaired so that the performance of the requirements of
this AD is affected, the owner/operator must request approval for an
alternative method of compliance in accordance with paragraph (d) of
this AD. The request should include an assessment of the effect of
the modification, alteration, or repair on the unsafe condition
addressed by this AD; and, if the unsafe condition has not been
eliminated, the request should include specific proposed actions to
address it.
Compliance: Required as indicated, unless accomplished
previously.
To prevent the installation of manual extension gearbox
assemblies that do not contain required gearbox housings/housing
assemblies, and ultimately could result in the inability of the
flight crew to lock the main landing gear (MLG) in the down position
during landing, accomplish the following:
(a) Within 6 months after the effective date of this AD,
visually inspect the manual extension gearbox assembly of the MLG,
in accordance with Boeing Service Bulletin 727-32-279, dated June
22, 1979, to determine whether left and right gearbox housings/
housing assemblies having Boeing part numbers listed in Table 1 of
this AD are installed.
Note 2: If the part number is not visible, a conductivity test
may be performed to determine the type of housing material.
Incorrect housings are made of 7079-T6 aluminum; correct housings
are made of 7075-T73 aluminum.
Table 1.--Boeing Part Numbers of Incorrect Housings and Housing
Assemblies
------------------------------------------------------------------------
Housing
Housings assemblies
------------------------------------------------------------------------
65-27485-3.............................................. 65-27485-1
65-27485-4.............................................. 65-27485-2
65-27485-9.............................................. 65-27485-7
65-27485-10............................................. 65-27485-8
------------------------------------------------------------------------
(b) If none of the incorrect housings/housing assemblies are
installed, no further action is required by this AD.
(c) If any of the incorrect housings/housing assemblies are
installed, prior to further flight, perform a dye penetrant
inspection to detect cracking of the housing, in accordance with
Boeing Service Bulletin 727-32-279, dated June 22, 1979.
(1) If no cracking is detected during the dye penetrant
inspection, the incorrect housing/housing assembly may be
reinstalled. Thereafter, the actions specified in paragraphs
(c)(1)(i) and (c)(1)(ii) must be accomplished.
(i) After reinstallation, repeat the dye penetrant inspection at
intervals not to exceed 9 months.
(ii) Within 18 months after the initial dye penetrant inspection
required by this
[[Page 51624]]
paragraph is accomplished, replace the housings/housing assemblies
with parts having an applicable Boeing part number listed in Table 2
of this AD, in accordance with the service bulletin. This
replacement constitutes terminating action for the repetitive dye
penetrant inspection required by this paragraph and, thereafter, no
further action is required by this AD.
(2) If any cracking is detected during the dye penetrant
inspection, prior to further flight, replace the housings/housing
assemblies with parts having an applicable Boeing part number listed
in Table 2 of this AD, in accordance with the service bulletin. This
replacement constitutes terminating action for the repetitive dye
penetrant inspection required by this AD and, thereafter, no further
action is required.
Note 3: This AD prohibits the reinstallation (or installation)
of any housing that is cracked, even though the service bulletin
provides instructions for reinstallation of a cracked, incorrect
housing in certain circumstances.
Table 2.--Boeing Part Numbers of Correct Replacement Housings and
Housing Assemblies
------------------------------------------------------------------------
Housing
Housings assemblies
------------------------------------------------------------------------
65-27485-13............................................. 65-27485-11
65-27485-14............................................. 65-27485-12
65-27485-19............................................. 65-27485-17
65-27485-20............................................. 65-27485-18
------------------------------------------------------------------------
Note 4: Although not listed in the service bulletin or in AD 79-
04-01 R3 (amendment 39-4000), housings/housing assemblies having
part numbers 65-27485-19/65-27485-17 and 65-27485-20/65-27485-18 are
fully interchangeable with those having part numbers 65-27485-13/65-
27485-11 and 65-27485-14/65-27485-12.
(d) 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.
(e) 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 September 26, 1996.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-25306 Filed 10-02-96; 8:45 am]
BILLING CODE 4910-13-U