# AD 91-18-21: Flap Track Support Fittings

- Type: Airworthiness directive
- Status: Current
- Products: Viking Air DHC-7-1, DHC-7-100, DHC-7-101, DHC-7-102 and DHC-7-103
- Effective: October 15, 1991
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Amendment: 39-8025
- Docket: 91-NM-43-AD
- Registered aircraft: 7 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/04EEEE5DE9538CB6862569810044F644.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/91-18-21

## The airworthiness directive

91-18-21 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment 39- 8025. Docket No. 91-NM-43-AD.

Applicability: Model DHC-7 series airplanes; Serial Numbers 53 through 57, 59, and 60; certificated in any category.

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

To prevent jamming of the flaps and reduction of airplane controllability, accomplish the following:

  (a) Replace the left- and right-hand wing flap track No. 4 forward support fittings in accordance with the Accomplishment Instructions of de Havilland Service Bulletin No. 7-27-37, dated October 28, 1981.

  (b) An alternative method 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 forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, New York Aircraft Certification Office.

  (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.

  (d) The replacement requirements shall be done in accordance with de Havilland Service Bulletin No. 7-27-37, dated October 26, 1981. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing of Canada, Ltd., de Havilland Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. Copies may be inspected at the FAA, Transport Airplane Directorate, Renton, Washington; at the FAA, New England Region, New York Aircraft Certification Office, 181 S. Franklin Avenue, Room 202, Valley Stream, New York; or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C.

This amendment (39-8025, AD 91-18-21) becomes effective on October 15, 1991.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A20EA](https://openairdocs.org/tcds/A20EA): De Havilland Aircraft of Canada Limited; names 5 of 5 models: DHC-7-101, DHC-7-103, DHC-7-102, DHC-7-100, DHC-7-1

## 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: 7 (7 by airframe model, 0 by engine model)
- Makers: Dehavilland 7

Models with the most aircraft:

- [Dehavilland DHC-7-102](https://openairdocs.org/model/dehavilland-dhc-7-102): 5 aircraft (airframe model)
- [Dehavilland DHC-7-103](https://openairdocs.org/model/dehavilland-dhc-7-103): 2 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/91-18-21/models.md
Every aircraft: https://openairdocs.org/ad/91-18-21/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.