# AD 68-06-01: Transmission Drive Shaft

- Type: Airworthiness directive
- Status: Current
- Products: Boeing Defense & Space Group 42A, 42B, 44A, 44B, H21A, H-21B, H-21B and H-21B
- Effective: March 21, 1968
- Published: March 21, 1968
- Issued: March 12, 1968
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-563
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/2F711F97FA6EAF7386256A34005B78FF.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/68-06-01

## The airworthiness directive

68-06-01 BOEING - VERTOL: Amendment 39-563. Applies to Helicopter Type 42A, 42B, 44A, 44B and Military H-21 series certificated under Part 21 (CAR Part 8 or 9).

Compliance required as indicated.

As a result of fatigue failures of the attacking lugs on transmission drive shaft flex coupling adapter P/N 22D3047-1, accomplish the following:

  (1) Unless already accomplished on helicopters which incorporate P/N 22D3047-1 adapters on transmission drive shaft assemblies (P/N 22D3046, 22D3057, 22D3066 or 22D2172) remove the shaft assembly from the helicopter within 15 hours' time in service after the effective date of this AD and strip all paint from the exposed portion of the adapter. Particular attention should be given to removal of all paint on both sides of the adapter lugs including the fillet area around the bosses where the adapter mates with the Thomas coupling plates. Do not allow paint remover to seep into the riveted joint. Perform a dye penetrant inspection of the exposed portion of the adapter and inspect for crack indications, paying particular attention to both sides of the adapter lugs and fillet areas. Any adapter with crack indications must be removed from service.

  (2) Any P/N 22D3047-1 new or used adapter re-installed in the helicopter after completing the above dye penetrant inspection must be inspected using a ten power magnifying glass within 10 hours' time in service and every 10 hours thereafter until an improved type adapter P/N 22D3047-3 is installed.

Upon installation of the -3 adapter, the above paragraphs 1 and 2 inspections are no longer required.

(Vertol Telex Communication No. 8-2300-2-59 dated January 17, 1968, covers this subject.)

This amendment effective March 21, 1968.

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1H12](https://openairdocs.org/tcds/1H12): Boeing Defense & Space Group; names 4 of 4 models: 44B, 44A, 42A, 42B
- [TCDS HR-35](https://openairdocs.org/tcds/HR-35): Heli-Crane Corporation; names 1 of 1 models: H21A

## Registered aircraft it may apply to (OpenAirDocs)

No registered aircraft matched the models it names.

Its text cites no advisory circulars or STCs.

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