AD 89-08-05

89-08-05 BELL HELICOPTER TEXTRON, INC.: Amendment 39-6403. Final copy of a Priority Letter AD. Docket No. 89-ASW-11.

Applicability: All Bell Helicopter Textron, Inc. (BHTI) Model 204B, 205A, 205A-1, 212, and 412 helicopters, certificated in any category, with main transmission spiral bevel gear, P/N 204-040-701-103, having less than 250 hours' time in service upon effective date of this AD and delivered as spares or in a new transmission between January 1, 1988, and April 4, 1989. The spare (uninstalled) spiral bevel gears, P/N 204-040-701-103, affected serial numbers are as follows:

A-3819 A-3821 A-3825 A-3826 A-3829 A-3833 A-3834 A-3836 A-3838 A-3840 A-3845 A-3847 A-3848 A-3850 A-3855 A-3856 A-3857 A-3858 A-3861 A-3878 A-3880 A-3885 A-3886 A-3889 A-3891 A-3892 A-3893 A-3895 A-3896 A-3897 A-3899 A-3901 A-3911 A-3915 A-3916 A-3919 A-3920 A-4008 A-4014 A-4017 A-4019 A-4020 A-4021 A-4027 A-4029 A-4068 A-4069 A-4071A-4075 A-4077 A-4078 A-4079 A-4080 A-4081 A-4083 A-4084 A-4085 A-4087 A-4089 A-4090 A-4091 A-4092 A-4093 A-4094 A-4095A A-4096 A-4097 A-4098 A-4107 A-4108 A-4109 A-4147 A-4184 A-4186 A-4187 A-4188 A-4191 A-4192 A-4193 A-4213 A-4229 A-4233 A-4235 A-4236 A-4241 A-4243 A-4244 A-4245 A-4254 A-4266 A-4267 A-4274 A-4275 A-4280 A-4282 A-4288 A-4289 A-4290 A-4303 A-4319 A-4320 A-4325 A-4327 A-4328 A-4329 A-4332 A-4333 A-4334 A-4335 A-4336 A-4337 A-4358 A-4366 A-4368 A-4369 A-4370 A-4371 A-4372 A-4374 A-4376 A-4377 A-4378 A-4379 A-4380 A-4383 A-4385 A-4386 A-4387 A-4394 A-4395 A-4397 A-4400 A-4401 A-4403 A-4411 A-4417 A-4418 A-4428

The following Model 212 serial numbered helicopters were delivered with affected main transmission spiral bevel gears; S/N's 31304, 31305, and 31307. The following Model 412 serial numbered helicopters were delivered with the affected main transmission spiral bevel gears: S/N's 33175, 33177, 33178, 33179, 33181, 33182, 33185, 33186, 33190, 33192, 33194, and 33195.

Compliance: Required as indicated, unless already accomplished.

To prevent failure of the main transmission spiral bevel gear which could result in possible loss of the helicopter, accomplish the following:

(a) Within the next 10 hours' time in service upon effective date of this AD and thereafter, before the first flight of each day, accomplish the following:

(1) Remove and inspect the transmission internal sump oil filter for evidence of metal contamination (e.g., steel particles in splinter, granular, or flake form).

(2) If metal contamination is evident, disassemble the main transmission to determine the extent of damage and replace any unserviceable parts with serviceable parts before further flight.

(b) Within the next 10 hours' time in service upon effective date of this AD and thereafter, at intervals not to exceed 50 hours' time in service from the last inspection, accomplish the following:

(1) Remove a quill pad cover, P/N 204-040-174-001, or rotor brake quill from the transmission main ring gear case to gain access to the main transmission spiral bevel gear.

(2) Utilizing a bright light and a dental mirror, inspect all teeth in the spiral bevel gear, P/N 204-040-701-103, for evidence of cracks, chipping, and metal deformation. If cracks, chipping, or metal deformation is evident, the part must be removed from service and replaced with a serviceable part before further flight.

(3) Reinstall pad cover, P/N 204-040-174-001, or rotor brake quill, whichever is applicable.

(c) The provisions of this AD do not apply when the time in service of the spiral bevel gear, P/N 204-040-701-103, reaches or exceeds 250 hours' time in service.

NOTE: Spiral bevel gear, P/N 204-040-701-103, affected by this AD may be returned to Bell Helicopter Textron, Inc., Attn: CPR Monitor, 3000 South Norwood & Trinity Boulevard, Hurst, Texas 76053, for inspection and reidentification. After reidentification, the provisions of this AD no longer apply.

(d) An alternate method of compliance or adjustment of the compliance time, which provides an equivalent level of safety, may be used when approved by the Manager, Rotorcraft Certification Office, Rotorcraft Directorate, Aircraft Certification Service, FAA, Southwest Region, Fort Worth, Texas.

(e) In accordance with FAR Sections 21.197 and 21.199, flight is permitted to a base where the inspection requirements of this AD may be accomplished.

This amendment becomes effective on January 3, 1990, as to all persons except those persons to whom it was made immediately effective by Priority Letter AD 89-08-05, issued April 12, 1989, which contained this amendment.