[Federal Register Volume 63, Number 31 (Tuesday, February 17, 1998)]
[Rules and Regulations]
[Pages 7693-7696]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-3635]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-78-AD; Amendment 39-10341; AD 98-04-29]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to all Boeing Model 727 series airplanes, that requires 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 amendment 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 this AD are intended to detect 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: Effective March 24, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 24, 1998.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

FOR FURTHER INFORMATION CONTACT: Walter M. Sippel, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-2774; 
fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to all Boeing Model 727 series 
airplanes was published in the Federal Register on October 3, 1996 (61 
FR 51621). That action proposed to require a one-time visual inspection 
of the manual extension gearbox assembly of the main landing gear (MLG) 
to detect whether this assembly contains the correct left and right 
gearbox housings/housing assemblies. If incorrect housings/housing 
assemblies are installed, that action also proposed to require 
repetitive dye penetrant inspections of these housings to determine 
whether cracking has occurred; and ultimately, replacement of these 
housings with correct housings.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    Three commenters support the proposed rule.

Request to Withdraw the Proposal

    Several commenters state that the proposed AD is unnecessary 
because AD 79-04-01 R3, amendment 39-4000 (45 FR 84014, December 22, 
1980), addresses the problem, thus the proposed AD only duplicates time 
and effort. One of these commenters points out that the ``incomplete 
information . . .'' of Boeing Overhaul Manual 32-35-01 (referred to in 
the Discussion Section of the preamble of the proposed AD) is ``a very 
gray area.'' This commenter contends that almost all overhaul manuals 
contain ``incomplete information,'' even when components are affected 
by AD's. The commenters assert that it is the responsibility of the 
operators and component vendors to determine which parts are affected 
by an AD. Two of these commenters state that all of their gearbox 
housings comply with the requirements of AD 79-01-04 R3.
    The FAA does not concur that the proposed AD should be withdrawn. 
The FAA acknowledges that, even though an overhaul manual may contain

[[Page 7694]]

incomplete information, operators are responsible for the overall 
airworthiness of the airplane. In addition, component vendors should be 
cognizant of AD's that affect parts they are overhauling.
    However, as explained in the Discussion section of the preamble of 
the proposed AD, the FAA has received a report indicating that a manual 
extension gearbox assembly for the MLG on a Boeing Model 727 series 
airplane had been replaced with a modified gearbox assembly that did 
not comply with AD 79-01-04 R3. In light of this report and the fact 
that the manufacturer's overhaul manual contained incomplete 
information for a period of time, the FAA finds that there currently 
may be other Model 727 series airplanes in service that are operating 
with incorrect gearbox housing/housing assemblies installed. Therefore, 
the FAA has determined that a one-time visual inspection of the manual 
extension gearbox assembly of the main landing gear (MLG) is necessary 
to detect whether or not these discrepant housings have been installed.

Request to Extend Compliance Time for One-Time Visual Inspection

    One commenter requests that the compliance time for accomplishing 
the proposed one-time visual inspection be extended from the proposed 6 
months to the first ``C'' check after the effective date of the AD. The 
commenter points out that it has found no cracked gearbox housing since 
accomplishment of AD 79-04-01 R3.
    The FAA does not concur. In developing an appropriate compliance 
time for this action, the FAA considered the safety implications, parts 
availability, and normal maintenance schedules for timely 
accomplishment of the visual inspection. In consideration of these 
items, as well as the report indicating that a manual gearbox assembly 
containing an incorrect housing had been installed on an airplane in 
service, the FAA has determined that a 6-month compliance time is 
appropriate.

Request to Extend Compliance Time for Initial Dye Penetrant 
Inspection

    One commenter requests that the compliance time for accomplishing 
the dye penetrant inspection required by paragraph (c) of the proposed 
AD be extended from the proposed ``prior to further flight'' to 
``within 100 hours time-in-service or 50 landings, whichever occurs 
first.'' The commenter states that the proposed compliance time is not 
justified because the FAA has not received recent reports of incorrect 
housing/housing assemblies that have been cracked. This commenter also 
states that it would have to special schedule its fleet of airplanes to 
accomplish this inspection within the proposed compliance time; this 
would entail considerable additional expenses and schedule disruptions.
    The FAA concurs partially. The FAA finds that stress corrosion 
cracking in the vertical support attaching lugs of the MLG manual 
extension-gearbox housing is caused by the combined action of corrosion 
and stress, either external (applied) or internal (residual). It is 
difficult to predict when stress corrosion cracking will occur because 
corrosion is influenced by unpredictable factors, such as the operating 
environment, maintenance, and the passage of time. If those housings/
housing assemblies are still installed on airplanes more than 17 years 
after AD 79-04-01 R3 was issued, there is a greater likelihood that 
stress corrosion cracking exists; therefore, the FAA finds that 
accomplishment of a dye penetrant inspection prior to further flight 
following accomplishment of the initial visual inspection is warranted.
    However, the FAA's intent is that the dye penetrant inspection be 
conducted during a regularly schedule maintenance visit for the 
majority of the affected fleet, when the airplanes would be located at 
a base where special equipment and trained personnel would be readily 
available, if necessary. The FAA finds that in lieu of accomplishing a 
dye penetrant inspection, an operator may choose to replace the 
discrepant part with an updated part prior to further flight following 
accomplishment of the initial visual inspection. Therefore, paragraph 
(c) of the final rule has been revised to provide operators with this 
option.

Request to Revise Dye Penetrant Inspection Requirement

    One commenter requests that operators be advised of where the 
incorrect gear boxes were found and of the source that obtained them. 
Subsequently, the discrepant gear boxes could be tracked and the 
proposed inspection requirements could be limited to those operators 
that received the discrepant housings from the suspect sources. The 
commenter also suggests that the initial visual inspection be 
accomplished within 300 landings and repeated at intervals not to 
exceed 6 months, and suggests that the replacement be accomplished 
within 18 months.
    The FAA does not concur. The FAA is unable to determine all sources 
of discrepant housings. Therefore, the FAA finds that the proposed one-
time visual inspection is necessary to determine whether certain 
gearbox housings have been installed. In addition, the FAA finds that a 
compliance time based on a number of landings is not acceptable 
because, as discussed previously, it is difficult to predict when 
stress corrosion cracking will occur.

Request to Revise Applicability of the Proposal

    Two commenters request that the applicability of the proposed AD be 
revised to exclude airplanes whose operators are confident of their 
gearbox installations or have internal procedures to ensure that only 
correct housing/housing assemblies are installed in accordance with AD 
79-04-01 R3.
    The FAA does not concur. A one-time visual inspection to confirm 
the presence of correct housings should not pose an undue burden to 
operators. If an operator chooses to review its available records, 
however, to determine that incorrect manual extension gearbox 
assemblies have not been installed, the operator may request approval 
of an alternative method of compliance in accordance with the 
provisions of paragraph (d) of this AD.

Request to Revise Table 2 of the Proposal

    One commenter requests that Table 2 of the proposed AD, which lists 
the part numbers of correct replacement housings and housing 
assemblies, be revised to include the Boeing part number of the die 
forging from which these parts could be made. (Not all of the correct 
parts are made from this forging.) The commenter points out that the 
part number on this die forging is easily ascertained and permanent, 
unlike the numbers on the housings/housing assemblies currently listed 
in Table 2. For the reasons the commenter states, the FAA concurs and 
has revised Table 2, as requested. In addition, because all the 
incorrect housings/housing assemblies are made from a certain die 
forging, the FAA has added the Boeing part number of that forging to 
Table 1, which lists the part numbers of incorrect housing and housing 
assemblies.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

[[Page 7695]]

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 will be affected by this AD.
    The FAA estimates that it will take approximately 2 work hours per 
airplane to accomplish the required one-time visual inspection, at an 
average labor rate of $60 per work hour. Based on these figures, the 
cost impact of the AD 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 will take approximately 20 work hours 
per airplane, at an average labor rate of $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 will 
take approximately 16 work hours per airplane to accomplish the 
replacement, at an average labor rate of $60 per work hour. Replacement 
parts will 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 requirements of this 
AD action, and that no operator will accomplish those actions in the 
future if this AD were not adopted.

Regulatory Impact

    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

98-04-29 Boeing: Amendment 39-10341. Docket 96-NM-78-AD.

    Applicability: All Model 727 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 
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 detect 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                               
------------------------------------------------------------------------
             Housings*                        Housing 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             
------------------------------------------------------------------------
* All housings are made from die forging 65-27485-6.                    

    (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, accomplish either paragraph 
(c)(1) or (c)(2) of this AD.
    (1) Perform a dye penetrant inspection to detect cracking of the 
housing, in accordance with Boeing Service Bulletin 727-32-279, 
dated June 22, 1979.
    (i) If no cracking is detected during the dye penetrant 
inspection, the incorrect housing/housing assembly may be 
reinstalled. Thereafter, accomplish the actions required by 
paragraphs (c)(1)(i)(A) and (c)(1)(i)(B) of this AD.
    (A) After reinstallation, repeat the dye penetrant inspection at 
intervals not to exceed 9 months.
    (B) Within 18 months after the initial dye penetrant inspection 
required by paragraph (c)(1) of this AD is accomplished, replace the 
housing/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 inspections required by paragraph 
(c)(1)(i)(A) of this AD and, thereafter, no further action is 
required by this AD.
    (ii) If any cracking is detected during the dye penetrant 
inspection, prior to further flight, replace the housing/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 inspections required by paragraph (c)(1)(i)(A) of this AD 
and, thereafter, no further action is required by this AD.
    (2) Replace the discrepant part with an applicable Boeing part 
number listed in Table 2 of this AD, in accordance with the service 
bulletin. Thereafter, no further action is required by this AD.

    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.

[[Page 7696]]



    Table 2.--Boeing Part Numbers of Correct Replacement Housings and   
                           Housing Assemblies                           
------------------------------------------------------------------------
             Housings*                        Housing 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             
------------------------------------------------------------------------
* Housings may be made from die forging 65-27485-15.                    

    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.
    (f) The inspections and replacement of parts shall be done in 
accordance with Boeing Service Bulletin 727-32-279, dated June 22, 
1979. This incorporation by reference was approved by the Director 
of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR 
part 51. Copies may be obtained from Boeing Commercial Airplane 
Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (g) This amendment becomes effective on March 24, 1998.

    Issued in Renton, Washington, on February 6, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-3635 Filed 2-13-98; 8:45 am]
BILLING CODE 4910-13-U