1AD/BELL 412/31 - Fin to Tail Boom Junction

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Bell Helicopter Textron 412 Series Helicopters

AD/BELL 412/31 Fin to Tail Boom Junction 8/92

TX

Applicability: All models.

Requirement: Remove the tail boom lower elliptical inspection panel, (Part number 205-030-814- 019) and perform a close visual inspection of the internal tail boom to fin junction area, paying particular attention to:

Skin Part number 212-030-099-087 or \-131, in the internal radius adjacent to, and the area immediately forward of, angle Stiffener Part number 205-030-801-007. (See attached diagram, Item 22).

2. The flanges of the left and right hand upper boom longerons, in the area adjacent to angle Stiffener Part number 205-030-801-007. (See attached diagram, Item 21)

Compliance: At the earliest opportunity, but before further flight after 25 May 92.

Background: One operator of a Bell 212 has reported a 250 mm crack in the subject skin, and adjacent cracks in the upper left hand longeron. These cracks occurred in line with the forward edge of the gear box support mount, and progressed under the skin doubler (Part number 212-030-099-089 or -129, Item 23) making external detection difficult. This one-off inspection is required to ensure that no other helicopters are immediately affected. Further action may be expected following laboratory investigation or manufacturers recommendation.

As the Bell model 412 has an identical tail boom to the model 212, this inspection is also required for these models.