# AD 75-16-04: Carburetor Air Box Valve

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-28-151
- Effective: July 30, 1975
- Published: July 28, 1975
- Issued: July 16, 1975
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-2272
- Registered aircraft: 961 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/96194DF162E2381A86256999005149B1.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/75-16-04

## The airworthiness directive

75-16-04 PIPER AIRCRAFT CORPORATION: Amendment 39-2272. Applies to PA-28-151 airplanes serial numbers 28-7415001 through 28-7515425; certificated in all categories.

Compliance required within the next 50 hours' time in service or at the next scheduled inspection, whichever occurs first, after the effective date of this AD, unless already accomplished.

To prevent over-travel of the carburetor air box valve, accomplish the following or accomplish an alternate modification method approved by the Chief, Engineering and Manufacturing Branch, Southern Region.

  (1) Remove lower nose cowl and metal bottom panel for access to the carburetor air box.

  (2) Loosen clamps attaching carburetor heat and induction air hoses to air box. Remove hoses from air box.

  (3) Remove control cable from bracket and lever on air box. Retain all hardware except cotter pin for reinstallation.

  (4) Remove air box bottom and valve by removing (12) #6 screws, nuts, and washers around the bottom of the air box. Retain the air box bottom and valve and attaching hardware for reinstallation.

  (5) Remove safety wire securing (4) MS20074-04-04 bolts which mount air box to carburetor. Remove the bolts and AN936A416 washers. Remove air box from carburetor. Remove and discard old 73451-07 gasket, but retain mounting hardware for reinstallation.

  (6) Install (2) plates, Piper Part Number 35646002, to top stiffener, secured with 8 (4 each plate) MS28470AL3-4 (Piper P/N 420-201) rivets. Installation must prevent valve over- travel.

  (7) Install new gasket Piper P/N 73451-07, and reworked air box on carburetor using (4) MS20874-04-04 bolts and AN936A416 washers. Safety wire bolts.

  (8) Reinstall bottom and valve assembly to air box using (12) #6 screws, nuts, and washers previously removed. Insure lever on valve is on the same side of box as control cable bracket.

  (9) Reinstall control cable. Tighten the swivel fitting nut to draw the core wire into the recess 1/2 its diameter.

  (10) Reinstall carburetor heat and induction air hoses on air box and secure with clamps.

  (11) Replace cowling and metal bottom panel.

Piper Service Bulletin 474 also pertains to this same subject.

This amendment becomes effective July 30, 1975.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 2A13](https://openairdocs.org/tcds/2A13): Piper Aircraft Inc.; names 1 of 18 models: PA-28-151

## 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: 961 (961 by airframe model, 0 by engine model)
- Makers: Piper 961

Models with the most aircraft:

- [Piper PA-28-151](https://openairdocs.org/model/piper-pa-28-151): 961 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/75-16-04/models.md
Every aircraft: https://openairdocs.org/ad/75-16-04/aircraft.md

Its text cites no advisory circulars or STCs.

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