What happened
On 22 May 2017, a Grumman AA-5 Traveller, registration G-BBSA, was conducting a training flight at Durham Tees Valley Airport. The flight was a revalidation exercise involving the pilot and an instructor.
During the pre-flight inspection, the pilot attempted to open the left engine cowling. Noting that the left cowl was notoriously difficult to operate, the pilot disengaged the latches but found the cowling would not open. Consequently, the latches were re-engaged without the cowling being opened. The pilot then completed the necessary engine bay and oil level checks by opening only the right cowling.
Following an uneventful taxi and power check, the aircraft departed from Runway 23. At an altitude of approximately 50 ft, an audible bang occurred, and the left engine cowling detached. The cowling was observed flapping over the right engine cowling. The instructor momentarily took control of the aircraft and reduced the throttle before returning control to the pilot. The aircraft subsequently returned to the airport, landing on the runway with approximately 700 m of runway remaining. There were no injuries to the crew.
The investigation
Investigators examined the aircraft following the incident. A post-flight inspection revealed that the left engine cowling attachments were damaged. Notably, the latches themselves remained undamaged and were found to be in their locked position. The pilot suggested that the latches had likely not been properly secured following the initial unsuccessful attempt to open the cowling during the pre-flight walkaround.