# AD 90-20-21: Cowl Doors

- Type: Airworthiness directive
- Status: Current
- Products: Bombardier DHC-8-101, DHC-8-102, DHC-8-103 and DHC-8-106
- Effective: October 26, 1990
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Amendment: 39-6745
- Docket: 90-NM-69-AD
- Registered aircraft: 13 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/528F473632F254A28625698100449325.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/90-20-21

## The airworthiness directive

90-20-21 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment No. 39-6745. Docket No. 90-NM-69-AD.

Applicability: De Havilland Model DHC-8-100 series airplanes, Serial Numbers 1 through 156 and 158 through 193, certificated in any category.

Compliance: Required within 300 days after the effective date of this AD, unless previously accomplished.

To prevent deformation or loss of the engine forward side cowl doors due to compartment overpressurization, and subsequent loss of fire extinguishing capability, accomplish the following:

A. Modify the cowl door retention latch arrangement and install pressure relief features on both engine cowlings, in accordance with the Accomplishment Instructions in de Havilland Service Bulletin No. 8-71-13, Revision C, dated January 12, 1990.

B. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, New York Aircraft Certification Office (ACO), ANE-170, FAA, New England Region.

NOTE: The request should be submitted directly to the Manager, New York ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Manager, New York ACO.

C. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing of Canada, Ltd., de Havilland Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplne Directorate, 1601 Lind Avenue S.W., Renton, Washington; or at the FAA, New England Region, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York.

This amendment (39-6745, AD 90-20-21) becomes effective on October 26, 1990.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A13NM](https://openairdocs.org/tcds/A13NM): De Havilland Aircraft of Canada Limited; names 4 of 16 models: DHC-8-101, DHC-8-102, DHC-8-103, DHC-8-106

## 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: 13 (13 by airframe model, 0 by engine model)
- Makers: Dehavilland 7, Boeing 3, Boeing Of Canada/Dehav Div 3

Models with the most aircraft:

- [Dehavilland DHC-8-106](https://openairdocs.org/model/dehavilland-dhc-8-106): 4 aircraft (airframe model)
- [Boeing DHC-8-102](https://openairdocs.org/model/boeing-dhc-8-102): 3 aircraft (airframe model)
- [Boeing Of Canada/Dehav Div DHC-8-106](https://openairdocs.org/model/boeing-of-canada-dehav-div-dhc-8-106): 2 aircraft (airframe model)
- [Dehavilland DHC-8-103](https://openairdocs.org/model/dehavilland-dhc-8-103): 2 aircraft (airframe model)
- [Boeing Of Canada/Dehav Div DHC-8-102](https://openairdocs.org/model/boeing-of-canada-dehav-div-dhc-8-102): 1 aircraft (airframe model)
- [Dehavilland DHC-8-102](https://openairdocs.org/model/dehavilland-dhc-8-102): 1 aircraft (airframe model)

All 6 models: https://openairdocs.org/ad/90-20-21/models.md
Every aircraft: https://openairdocs.org/ad/90-20-21/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.