What happened
On 12 October 2012, a Diamond DA 42 NG, registration A6-HIC, was conducting a training flight from Al Ain International Airport with a flight instructor and a student pilot onboard. During the initial climb following takeoff, the crew noticed an unusual slipstream noise and a visible gap between the rear passenger door and the door sill.
In an attempt to manage the situation, the instructor tried to hold the door closed while flying the aircraft. However, after the instructor had to release the handle to focus on flight controls and managing the increased aerodynamic drag, the rear door separated from the airframe. The instructor took control of the aircraft to manage the descent, communications, and the high power demands required to maintain level flight despite the significant drag caused by the door loss. There were no injuries to the two occupants.
The investigation
An investigation by the UAE Air Accident Investigation Sector (AAIS) focused on the sequence of events leading to the door separation. Investigators examined the aircraft's maintenance records, the cockpit canopy and door locking mechanisms, and the crew's adherence to standard operating procedures. The investigation also reviewed the academy's specific checklists and the instructor's actions during the takeoff roll.
Findings
Several critical factors contributed to the incident. The investigation established that the instructor failed to physically verify that all external door locks were secured during the pre-flight inspection. Additionally, the crew did not strictly follow pre-takeoff checklist requirements regarding the cockpit canopy.
A significant factor was the instructor's fixation on potential engine control unit (ECU) warnings caused by the student pilot's rapid throttle advancement, which led to a failure to notice the active door warning light and audio alert. Furthermore, the investigation determined there was a probable attempt to close the rear door while in flight, which directly contradicts the manufacturer's warning that such an action can cause the latch to disengage and the door to open.
Safety action
Following the investigation, the AAIS issued safety recommendations to the General Civil Aviation Authority (GCAA) to ensure that all Diamond DA 42 NG operators in the UAE modify their emergency checklists to align with manufacturer standards. The recommendations also emphasize the necessity of reinforcing the instruction to land as soon as possible during a door warning, rather than attempting to close the door in flight.