United Arab Emirates investigators have disclosed that the Diamond Aircraft DA62 which fatally crashed at Dubai last month had been following preceding traffic on a parallel runway closer than prescribed before a suspected wake-vortex upset.
It was flying 3.7nm behind an Airbus A350 whose wake turbulence is thought to have contributed to the accident.
The DA62, with four occupants, had departed Dubai to conduct calibration approaches to runway 30L on 16 May, as part of a ground lighting check linked to runway refurbishment.
These flights were carried out under visual flight rules, with air traffic control communicating with the DA62 on a separate frequency.
The aircraft performed nine circuits, over the course of about 1h 20min, and entered final approach for the 10th behind a Thai Airways International A350-900 which was 3.7nm ahead, flying the parallel approach to 30R.
After levelling off from the turn to final, at around 1,100ft and 130kt, the DA62 rolled slightly but recovered 9s later.
But 7s after that, the aircraft "abruptly" rolled to the left, says the UAE's General Civil Aviation Authority, becoming inverted before entering a steep dive.
It struck the ground in a nature reserve about 3.5nm from the runway 30L threshold, travelling at "high speed" on a heading of about 100° – almost the opposite direction to its intended flightpath, says the inquiry.
Tree damage indicates the DA62 was in an upright attitude but pitched 24° nose-down with its right-wing down 30°.
"The aircraft was completely destroyed by impact forces and the post impact fire," says the inquiry, with its fibre reinforced plastic fuselage and wings consumed entirely.
None of the four occupants survived.
Investigators found that the DA62 had "consistently followed" preceding traffic on approach to 30R at distances which were "below the specified minimum separation", and less than the distances discussed during a pre-departure meeting.
The DA62 pilots had agreed that they would apply their own separation to other arriving aircraft on 30R, which meant air traffic control would not be responsible for providing wake turbulence separation.
"Radar monitor recording indicated that there was an air traffic control inconsistency in advising the DA62 of the expected occurrence of hazards caused by wake turbulence," the inquiry adds.
While the investigation has yet to reach formal conclusions, the inquiry suspects a wake turbulence encounter from the A350 contributed to the accident and has issued an early safety recommendation to air navigation services and light aircraft operators to "enhance awareness" of separation procedures, particularly under visual flight rules.