What happened
On 13 May 2005, a Piper PA-38-112, registration G-BJUR, was being prepared for a training flight at Nottingham Airfield. During pre-flight preparations, the student pilot was instructed to verify the engine oil and fuel levels. Upon noticing the oil level appeared low, the student requested that the ground crew add one quart of oil to the engine.
Following the oil replenishment, the instructor performed a check of the fuel in both wing tanks and verified the engine oil level using the dipstick. After closing the cowling and boarding the aircraft, the instructor proceeded with a standard takeoff. While the aircraft was at an altitude of approximately 500 feet, performing a left-hand turn and bank, a loud bang occurred. The left-side engine cowling lifted, partially obstructing the pilot's forward vision. The cowling struck the lower right section of the windscreen, creating a hole several inches in diameter. The instructor leveled the aircraft, issued a 'PAN' radio call, and returned to the airfield to land safely. There were no injuries to the two crew members.
The investigation
The investigation focused on the security of the engine cowlings. The Piper PA-38-112 is designed with separate left and right cowlings, each attached via longitudinal hinges and secured by two butterfly clips on the lower edges. Upon inspection of G-BJUR after the landing, investigators found that both butterfly clips on the left-side cowling were missing.
Evidence suggested that the left cowling may not have been properly secured prior to departure. While the instructor noted that missing clips had been observed on other aircraft in the fleet during daily inspections, the investigation also considered that the student may have mistakenly inspected the left side of the engine during the oil check, as the dipstick and filler are located on the right. This error could have led to the left cowling being left unsecured.