Event Summary
On 12 October 2012, at approximately 0625 local time, a Diamond DA42NG Twin Star, registration A6-HIC, was conducting a training flight from Al Ain International Airport (OMAL). The aircraft had a student pilot and a flight instructor on board. During the initial climb after takeoff, an unusual slipstream sound was noticed, traced to the rear passenger door. A gap was visible between the door sill and the lower edge of the door. The instructor attempted to hold the door closed but had to release the grip to manage the flight. Soon after, while turning left to join the circuit, the rear passenger door separated from the airframe. The instructor assumed control as pilot flying, managed the descent and circuit with ATC communication, and landed without further incident.
Aircraft and Door System
The Diamond DA42NG Twin Star is a twin-engine, four-seat, low-wing monoplane with a composite structure. The rear passenger door is a one-piece canopy with a large glazed area, hinged at the top and supported by a gas strut when open. The door latching system includes internal and external handles and locking bolts.
Sequence of Events
Before takeoff, the student completed pre-flight checks. During the pre-takeoff checklist, the door warning light was reported out, but the instructor noted the front canopy was in the cooling gap position. The student then closed the front canopy and rechecked the warning light. After takeoff clearance, the student advanced the throttles rapidly. The instructor noted a historical concern of ECU failure indications with rapid throttle advancement. The takeoff roll and initial climb proceeded normally until around 200 feet AGL and 100 knots indicated airspeed, when an unfamiliar slipstream sound was heard. The noise was identified as coming from the rear door, with a visible gap. The instructor attempted to hold the door handle but the aerodynamic loads were excessive, and the instructor released the handle at approximately 400 feet AGL. Shortly thereafter, the rear passenger door separated.
Damage and Investigation
The passenger door separated as a complete assembly. The door lifted from the latched lower edge due to aerodynamic loads and separated at the upper hinge line, which failed beyond design limits. The door sustained damage from ground contact after separation. Both the flight instructor and student pilot held current licenses and medical certificates. No injuries were reported. The aircraft was airworthy, with its GCAA airworthiness certificate revalidated on 29 April 2012.