Service Difficulty Alert

AL 2000-06
11 October 2000

Large Jet Transport Aircraft

Engine Fan Cowl Loss

Ongoing investigation by Transport Canada and the Transportation Safety Board of Canada into the recent loss of engine fan cowlings from Airbus aircraft operated in Canada has brought to light several findings which may affect the safe operation of these and other large jet transport aircraft:

  • The loss of fan cowls in flight poses a significant safety risk to the aircraft and its occupants.
  • Failure to follow the manufacturer's instructions for operation of the cowling latches may lead to the latch handle opening in flight.
  • Many of the recent occurrences followed a maintenance action in which the cowl was opened, indicating that possibly not all persons involved with the operation of these assemblies are following the manufacturer's instructions for their operation.
  • During several engagement tests, the latch handle reached full travel before the trigger/safety latch could engage completely, rendering the latch ineffective. The subtle offset of the trigger/safety latch may be difficult to detect in an operational environment.
  • The audible "click" of the trigger/safety mechanism engaging is difficult to detect under operational conditions. A convenient procedure for determining handle security is not clearly stated in the Airbus publications.
  • 80% of the Airbus latches inspected were found to be below the manufacturer's specified minimum latch tension.
  • Retention springs were observed to be broken or missing on several latch assemblies.
  • In some installations, the handle latch pins were found broken. This appeared to be due to improper assembly and installation.
  • An unsecured cowling latch handle or trigger mechanism may not be readily identifiable due to its location on the bottom of the cowl.

In light of these findings, Transport Canada strongly recommends the following:

  1. Operators of large jet transport aircraft should ensure that all personnel approved to operate the cowl latches have read and understand the instructions contained within the manufacturer's appropriate publication and have received adequate training in the operation of the cowl closure system.
  2. Readily visible portions of cowl latches should be visually inspected whenever they are operated, and any abnormalities should be rectified before flight.
  3. Operators of aircraft with cowling latches not readily visible should consider the marking of these handles with a contrasting color to help make an unsecured handle more conspicuous.
  4. Operators and maintainers of large transport category aircraft should have in place a procedure to ensure security of engine cowls before flight.
  5. Ensure that all personnel involved with the maintenance of these latches have all the necessary documentation for correct installation, e.g. Aircraft Maintenance Manual, etc.

This issue remains under investigation by Transport Canada.

Any defects or further occurrences should be reported by sending a Service Difficulty Report to Transport Canada, Continuing Airworthiness, Ottawa.

For further information, contact a Transport Canada Centre, or Mr. Paul Jones, Continuing Airworthiness, Ottawa, telephone (613) 952-4431, facsimile (613) 996-9178 or e-mail jonesp@tc.gc.ca.

For Director, National Aircraft Certification

B. Goyaniuk
Chief, Continuing Airworthiness

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