Airworthiness Directive · Amendment 39-11730 · MD Helicopters Inc. Model MD900 Helicopters
MD Helicopters Inc. Model MD900 Helicopters
Model MD900 helicopters, certificated in any category.
Note 1: This AD applies to each helicopter 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 helicopters 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.
This amendment adopts a new airworthiness directive (AD) for MD Helicopters Inc. (MDHI) Model MD900 helicopters. This action requires visually inspecting the drive shaft to determine the assembly part number (P/N) and marking the drive shaft assembly P/N and serial number (S/N) on any unmarked drive shaft. This AD also requires creating a component history card or equivalent record for certain drive shaft assemblies and replacing any drive shaft assembly that has reached its life limit. This amendment is prompted by the discovery of several drive shafts with no assembly P/N marked on the part, which could result in a drive shaft remaining in service past its life limit. The actions specified in this AD are intended to prevent failure of the drive shaft due to fatigue, which could result in total loss of drive to the main rotor hub and subsequent loss of control of the helicopter.
To prevent failure of the drive shaft due to fatigue, which could result in total loss of drive to the main rotor hub and subsequent loss of control of the helicopter; accomplish the following:
(a) Before accumulating 1,450 hours time-in-service (TIS), visually inspect the drive shaft assembly to determine which part number (P/N) is installed. If necessary, remove the drive plate cover to access the P/N located on the top edge of the drive shaft assembly. If the number of hours TIS on the drive shaft assembly is unknown, use the total hours TIS on the helicopter.
Note 2: Do not confuse the P/N of the drive shaft subassembly, P/N 900D2436028-101, 900D2436026-101, or 900D2436030-101 as the P/N of the drive shaft assembly.
(1) If a drive shaft assembly, P/N 900D2436530-101, is installed, no further action is required by this AD.
(2) If a drive shaft assembly other than P/N 900D2436530-101 is installed and is not marked with a P/N, before further flight, use an indelible ink fine tip marking pen to mark the following information on the edge of the drive shaft assembly in line with the engraved subassembly number:
(i) P/N 900D2436528-101 and the serial number (S/N) of the drive shaft subassembly if the subassembly is P/N 900D2436028-101. When the ink dries, apply a clear coat over the P/N and S/N, or
(ii) P/N 900D6400004-101 and the S/N of the drive shaft subassembly if the subassembly is P/N 900D2436026-101. When the ink drives, apply a clear coat over the P/N and S/N.
(b) For a drive shaft assembly with 1,450 or more hours TIS, before further flight, accomplish paragraph (a) of this AD.
Note 3: MD Helicopters Inc. Service Bulletin SB900-062 R1, dated December 16, 1999, applies to the subject of this AD.
(c) After accomplishing the requirements of paragraph (a) of this AD, before further flight, determine the hours TIS of the drive shaft assembly. Record the hours TIS on a current or newly created component history card or equivalent record. If the drive shaft assembly has reached or exceeded its life limit, replace the drive shaft assembly with an airworthy drive shaft assembly before further flight.
Note 4: The Airworthiness Limitations Section, section 04, of the MD-900 Rotorcraft Maintenance Manual (CSP-900RMM-2), Revision 6, dated December 23, 1999, pertains to the subject of this AD.
