# AD 70-08-03: Heater Inlet Check Valve

- Type: Airworthiness directive
- Status: Current
- Products: Sikorsky S-61A, S-61L, S-61N and S-61R
- Effective: March 17, 1970
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-974
- Registered aircraft: 53 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/2D5166841CA229FD86256A55006DB2FE.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/70-08-03

## The airworthiness directive

70-08-03 SIKORSKY: Amdt. 39-974. Applies to Sikorsky type S-61A/L/N/R helicopters certificated in all categories.

Accomplish the following within the next 10 heater hours in service, unless already accomplished, and every 15 heater hours in service thereafter:

A. Remove and inspect combustion air inlet duct backfire check valve Bobrick Co. P/N 9660-1-1 or 40064-32 for distortion, missing flappers, or other obvious damage.

B. Replace defective valves before further operation of the heater with a part inspected in accordance with paragraph A above. Upon replacement inspect all heater inlet air ducting for evidence of fuel contamination. Any fuel contamination must be eliminated before further heater operation.

C. Upon submission of substantiating data through an FAA maintenance inspector, the Chief, Engineering and Manufacturing Branch, FAA Eastern Region may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator.

D. For the purpose of this AD, compliance time may be based on helicopter hours in service if the owner or operator cannot document heater operating time.

This amendment is effective April 23, 1970, and was effective March 17, 1970 for all recipients of the telegram dated March 17, 1970 which contained this amendment.

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1H15](https://openairdocs.org/tcds/1H15): Sikorsky Aircraft; names 3 of 4 models: S-61R, S-61N, S-61L
- [TCDS H2EA](https://openairdocs.org/tcds/H2EA): Sikorsky Aircraft Corporation; names 1 of 4 models: S-61A

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 53 (53 by airframe model, 0 by engine model)
- Makers: Sikorsky 52, Carson Helicopters / Sikorsky 1

Models with the most aircraft:

- [Sikorsky S-61N](https://openairdocs.org/model/sikorsky-s-61n): 45 aircraft (airframe model)
- [Sikorsky S-61A](https://openairdocs.org/model/sikorsky-s-61a): 5 aircraft (airframe model)
- [Sikorsky S-61L](https://openairdocs.org/model/sikorsky-s-61l): 1 aircraft (airframe model)
- [Sikorsky S-61R](https://openairdocs.org/model/sikorsky-s-61r): 1 aircraft (airframe model)
- [Carson Helicopters / Sikorsky S61A](https://openairdocs.org/model/carson-helicopters-sikorsky-s61a): 1 aircraft (airframe model)

All 5 models: https://openairdocs.org/ad/70-08-03/models.md
Every aircraft: https://openairdocs.org/ad/70-08-03/aircraft.md

Its text cites no advisory circulars or STCs.

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