# AD 74-26-04: Explosion Hazards

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-31 and PA-31-300
- Effective: December 19, 1974
- Published: December 12, 1974
- Issued: December 5, 1974
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-2044
- Registered aircraft: 29 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D68CDC0763BF9E1A86256999005140F8.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/74-26-04

## The airworthiness directive

74-26-04 PIPER: Amendment 39-2044. Applies to Models PA-31 & PA-31-300 S/N 31- 2 to 31-7401258 inclusive.

Compliance required as indicated unless already accomplished:

In order to eliminate explosion hazards associated with fuel leaking from the heater manual shut-off and solenoid shut-off valves in the nose compartment, accomplish the following:

a. Within 25 hours time in service after the effective date of this AD, conduct a pressure check of the P/N 492107 manual heater shut-off valve and P/N 756513 solenoid fuel regulator shut-off valve. This may be accomplished by operating the right electric fuel pump, turning on the heater manual fuel valve and visually inspecting for fuel seepage around the valve body and connecting line fittings of both shut-off valves.

If any leakage is observed, the valve must be replaced or repaired and the pressure check repeated.

b. Within 125 hours time in service after the effective date of this AD for Serial Numbers 31-2to 31-7401258 inclusive, remove manual heater fuel shut-off valve P/N 492107 and bracket P/N 41948-00 in accordance with Piper Service Bulletin No. 417 and subsequent approved revisions.

c. Within 125 hours time in service after the effective date of this AD for Serial Numbers 31-2 to 31-103 inclusive, install shroud assembly Piper P/N 43493 with associated cover, overboard drain tube, sealing grommets and clamp over heater solenoid shut-off valve P/N 756513 in accordance with Piper installation drawing No. 41923 and Parts Catalog No. 753703 Fig. 38.

d. Alternate equivalent modifications to those described above must be approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region. Aircraft may be flown to a base where the maintenance required by this Airworthiness Directive may be performed per FAR's 21.197 and 21.199.

(Piper Service Bulletin No. 417 dated August 26, 1974, pertains to this subject.)

This amendment is effective December 19, 1974.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A20SO](https://openairdocs.org/tcds/A20SO): Piper Aircraft Inc.; names 2 of 4 models: PA-31, PA-31-300

## 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: 29 (29 by airframe model, 0 by engine model)
- Makers: Piper 29

Models with the most aircraft:

- [Piper PA-31](https://openairdocs.org/model/piper-pa-31): 26 aircraft (airframe model)
- [Piper PA-31-300](https://openairdocs.org/model/piper-pa-31-300): 3 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/74-26-04/models.md
Every aircraft: https://openairdocs.org/ad/74-26-04/aircraft.md

Its text cites no advisory circulars or STCs.

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