Inspection of the Translating Cowl Doors - Civil Aviation Safety Alert (CASA) No. 2020-01


Owners, operators and maintainers of Bombardier Inc. CL-600-2B19 (CRJ 100 & 440 series) aeroplanes

File Classification No. : Z 5000-35
RDIMS No. : 15943414
Document No. : CASA 2020-01
Issue No. : 01
Effective Date: 2020-02-14


The purpose of this Civil Aviation Safety Alert (CASA) is to remind individuals who conduct inspections of the translating cowl doors that they should refer to the latest Aircraft Maintenance Manual (AMM) applicable inspection requirements/procedures.


Transport Canada has received reports of upper and/or lower translating cowl doors becoming dislodged from the nacelle and subsequently departing in flight resulting in damage to the airplane fuselage. Investigation by Bombardier Inc. (BA) has determined that in 3 cases, the improper/inadequate maintenance was most likely the main contributing factor for the dislodgement of the translating cowl doors.

In one case, both upper and lower translating cowls were dislodged and the investigation revealed that the main cause of the dislodgement was failure of the latch line Upper Interlock Fitting due to a dormant fatigue crack. As there was no detailed inspection requirement identified for the subject fittings, this critical crack was not detected during routine maintenance activities.

In order to prevent reoccurrence, BA has revised the AMM to introduce an additional detailed inspection task for the translating cowl closing latches and fittings.

Recommended action:

Transport Canada recommends that operators and maintainers of CL-600-2B19 airplanes familiarize themselves with BA’s All Operator Message (AOM) No. 1667, and follow the latest maintenance instructions for Translating Cowl Door inspection in accordance with the AMM Rev. 58 or later revisions of Task 78−30−00−220−801 and/or Task 71−11−01−210−801.

Contact office:

For more information concerning this issue, contact a Transport Canada Centre; or A K Durrani, Continuing Airworthiness in Ottawa, by telephone at 1-888-663-3639, facsimile at 613-996-9178 or e mail at

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.