DASH 8-400 (Q400) Forward Cowl Door Departure from the Aircraft on Take-off - Civil Aviation Safety Alert (CASA) No. 2020-08


Owners, operators and maintainers of De Havilland Aircraft of Canada Limited Dash 8-400 series (Q400) aeroplanes

File Classification No. : Z 5000-35
RDIMS No.: 16703162
Document No.: CASA 2020-08
Issue No.: 01
Effective Date: 2020-09-10


The purpose of this Civil Aviation Safety Alert (CASA) is to raise awareness of the proper maintenance practice and recommended modifications to prevent the forward cowl door on the engine nacelle from departing the aeroplane during take-off.


There have been a number of reported occurrences of the forward cowl door departing from the aeroplane on take-off following maintenance access to the powerplant area. Loss of the cowl door has resulted in damage to the aeroplane’s wing leading edge, wing skin and vertical tail structure.

Inspections of the cowl doors recovered at the departure airports revealed that all occurrences were attributed to unsecured cowl doors. In some events, the latches on the door panel were not in the closed and latched position, indicating that the cowl doors were not latched after performing maintenance. In other events, the latches on the door panel were in the closed position, indicating that the latches were closed before the cowl doors were shut, preventing the locking pin of latches from engaging in the receiving fitting on the nacelle lower cowl.

In order to prevent reoccurrence, De Havilland Aircraft of Canada Limited has issued an All Operator Message (AOM), No. 870 on 17 July 2020, to bring attention to a new Aircraft Maintenance Manual (AMM) task instruction for proper cowl door closing, the Service Bulletin 84-11-46, a new modsum which introduces placards for illustrating the proper closing of the cowl door, and new rework modifications to improve the ability of latch engagement.

Recommended action:

Transport Canada Civil Aviation recommends that owners, operators and maintainers of Dash 8-400 aeroplanes familiarize themselves with De Havilland’s AOM No. 870 and follow the improvement actions outlined in the AOM for maintenance instructions, placard addition and rework to the latch mechanism.

Contact office:

For more information concerning this issue, contact a Transport Canada Centre; or Zhiwei Wang, Continuing Airworthiness in Ottawa, by telephone at 1-888-663-3639, facsimile at 613-996-9178 or by e-mail at cawwebfeedback@tc.gc.ca.

Original signed by

Rémy Knoerr
Chief, Continuing Airworthiness
National Aircraft Certification

The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.