# AD 72-11-05: Auxiliary Fuel Cell Leaks

- Type: Airworthiness directive
- Status: Current
- Products: Cessna 411, 411A, 421, 421A, 421B and 421C
- Effective: June 2, 1972
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-1454
- Registered aircraft: 779 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/52AFD54C0B101A0286256A3400634878.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/72-11-05

## The airworthiness directive

72-11-05 CESSNA: Amdt. 39-1454. Applies to Models 411 and 421 series airplanes.

Compliance: Required as indicated, unless already accomplished.

In order to detect auxiliary fuel cell leakage that could result in possible fire and explosion hazards from fuel vapor ignition, accomplish the following:

A) On Model 411 (Serial Numbers 411-0001 thru 411-0200) airplanes:

1) Within 10 hours' time in service after the effective date of this AD, and thereafter prior to the first flight of each day, visually inspect the lower surface of the wings in the area of the auxiliary fuel cells for fuel stains and leakage. If auxiliary fuel cell leakage is observed, prior to further flight, replace the auxiliary fuel cells with improved auxiliary fuel cells in accordance with Cessna Service Letter ME72-8, dated April 21, 1972, or any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region.

2) The repetitive inspections required prior to the first flight of each day may be performed by the pilot, including pilots of aircraft engaged in air taxi operations. A chronological listing of compliance with this AD must be made in the airplane's permanent maintenance log in accordance with FAR 91.173.

3) On or before January 1, 1973, replace all auxiliary fuel cells with the improved auxiliary fuel cells specified in Cessna Service Letter ME72-8, dated April 21, 1972.

4) The repetitive inspections required in Paragraph A(1) may be discontinued when the improved auxiliary fuel cells are installed.

B) On Model 411 (Serial Numbers 411-0201 thru 411-0300) airplanes and on Model 421 (Serial Numbers 421-0001 thru 421B0048) airplanes, within 10 hours' time in service after the effective date of this AD and thereafter at intervals not to exceed 100 hours' time in service from the date of the last inspection, visually inspect the lower surface of the wings in the area of the auxiliary fuel cells for stains or leakage. If auxiliary fuel cell leakage is observed, prior to further flight, replace the auxiliary fuel cells with improved auxiliary fuel cells in accordance with Cessna Service Letter ME72-8, dated April 21, 1972, or any equivalent method approved by the Chief, Engineering and Manufacturing Branch, FAA, Central Region. The repetitive inspections required in this paragraph may be discontinued when the improved auxiliary fuel cells are installed.

This amendment becomes effective June 2, 1972.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A7CE](https://openairdocs.org/tcds/A7CE): Textron Aviation Inc.; names 6 of 16 models: 421C, 411A, 421B, 421A, 411, 421

## 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: 779 (779 by airframe model, 0 by engine model)
- Makers: Cessna 779

Models with the most aircraft:

- [Cessna 421C](https://openairdocs.org/model/cessna-421c): 496 aircraft (airframe model)
- [Cessna 421B](https://openairdocs.org/model/cessna-421b): 225 aircraft (airframe model)
- [Cessna 421](https://openairdocs.org/model/cessna-421): 28 aircraft (airframe model)
- [Cessna 421A](https://openairdocs.org/model/cessna-421a): 20 aircraft (airframe model)
- [Cessna 411](https://openairdocs.org/model/cessna-411): 6 aircraft (airframe model)
- [Cessna 411A](https://openairdocs.org/model/cessna-411a): 4 aircraft (airframe model)

All 6 models: https://openairdocs.org/ad/72-11-05/models.md
Every aircraft: https://openairdocs.org/ad/72-11-05/aircraft.md

Its text cites no advisory circulars or STCs.

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