# AD 64-19-06: Spiral Bevel Pinion Gears

- Type: Airworthiness directive
- Status: Current
- Products: Boeing Defense & Space Group 42A, 42B, 44A, 44B, H-21B, H-21B and H-21B
- Effective: August 7, 1964
- Published: August 7, 1964
- Issued: July 31, 1964
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/2156A4243884750686256A34005B5D59.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/64-19-06

## The airworthiness directive

64-19-06 VERTOL: Amdt 782 Part 507 Federal Register August 7, 1964. Applies to Models 42A, 42B (Military H21B, H21C), 44A and 44B Helicopters.

Compliance required as indicated.

A spiral bevel pinion gear P/N 42D2043-2 installed in an aft transmission of a Vertol Model 42/44 Series helicopter recently failed. The nature of the failure indicated that metallurgical processing was a contributing factor. The gears listed herein were manufactured in the same carburizing and heat treat lot. These gears must be removed from service and replaced as follows:

  (a) Remove from service any spiral bevel pinion gear P/N 42D2043-2 listed in paragraph (b) and replace it in accordance with the V44-28 rotor transmission overhaul manual at the following times:

  (1) Within 10 hours' time in service after the effective date of this AD for those gears which have 500 or more hours' time in service on the effective date of this ad.

  (2) Within 50 hours' time in service after theeffective date of this AD for those gears which have less than 500 hours' time in service on the effective date of this AD.

  (b) The following spiral bevel pinion gears P/N 42D2043-2 shall be removed from service in accordance with paragraph (a):

Gear S/N - P2009; Aft Transmission S/N - P-9-1653 Gear S/N - P2008; Aft Transmission S/N - P-9-1665 Gear S/N - P2001; Aft Transmission S/N - P-9-1657 Gear S/N - P1999; Aft Transmission S/N - P-9-1640 Gear S/N - P1997; Aft Transmission S/N - P-9-1646 Gear S/N - P1977; Aft Transmission S/N - P-9-1642 Gear S/N - P1972; Aft Transmission S/N - P-9-1405 Gear S/N - P2007 Gear S/N - P1995 Gear S/N - P1962 Gear S/N - P1961

NOTE. - It is believed that the aft transmission S/N's listed above have the corresponding gear S/N listed. It is not known which aft transmission S/N's may have the remaining listed gear S/N's.

(Vertol Division Technical Memorandum SDTMNo. 2059 dated May 19, 1964, covers this subject.)

This directive effective August 7, 1964.

## Affected data sheets (1) (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

## 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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