Manual Extension Gearbox

Category - Airframe
Effective Date - 03/24/1998
Recurring - Yes
Supersedes - N/A
Superseded by - N/A
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.

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.

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.