[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]


-----------------------------------------------------------------------


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).

-----------------------------------------------------------------------

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