Wake Turbulence Suspected in Diamond DA62 Accident in Dubai
On 2o June 2019 the the Air Accident Investigation Sector (AAIS) of the UAE General Civil Aviation Authority (GCAA) released their preliminary report into the loss on 16 May 2019 of Diamond DA62 G-MDME of Flight Calibration Services Ltd (FCSL) at Dubai International Airport.
The aircraft, with 4 persons on board, was flying approaches to runway 30L as part of a ground lighting calibration linked to runway refurbishment. Dubai has two parallel runways, 12R/30L and 12L/30R. The distance between the runway centerlines is approximately 380 meters. These flights were conducted under visual flight rules (VFR), with air traffic communicating with the DA62 on a separate frequency. The investigators say that:
The prevailing meteorological conditions at the time of the Accident were fine with ceiling and visibility ok (CAVOK). Low level winds were recorded at 1,000 ft with a speed of 6 kt from 020 degrees, and a speed of 11 kt from 010 degrees at 1,500 ft. Sunset on 16 May 2019 in Dubai was at 1857
At 1929, the Aircraft entered the final to runway 30L for the tenth approach, following a Thai Airways Airbus A350-900, which was flying the approach to the parallel runway 30R. The Airbus was approximately 3.7 nautical miles (nm) ahead of the DA62. When the DA62 leveled off after turning onto final at an altitude of approximately 1,100 feet (ft) and at an airspeed of approximately 130 knots (kt), it rolled slightly but was recovered after nine seconds. Seven seconds later, the [DA62] abruptly rolled to the left until it became inverted and it then entered a steep dive. The aircraft impacted the ground approximately 3.5 nm from the runway 30L threshold.
… the Aircraft impacted the ground at an elevation of approximately 130 ft while travelling at high speed in the direction opposite to the direction of flight, on a heading of approximately 100 degrees.
All four persons onboard the Aircraft sustained fatal injuries…[and]…the aircraft was destroyed by impact forces and the subsequent fire.
The Safety Investigation
The 406 MHz Emergency Locator Transmitter (ELT) installation was damaged in the impact, with the antenna and electrical cables severed from the unit. Consequently, no signals were detected from it.
The investigators state that at a meeting with the airport before the calibration flights commenced, it was agreed that:
The DA62 would apply own separation to other arriving aircraft to the parallel runway 30R while operating under VFR, which meant that ATC would not be responsible for providing wake turbulence separation.
The investigators reviewed the airport radar data:
Observations of previous approaches during the same calibration flight indicated that the DA62 consistently followed preceding traffic on approach to the parallel runway 30R at distances which were below the specified minimum separation, and less than the distances discussed during the pre-departure meeting.
The radar monitor recording indicated that there was an air traffic control (ATC) inconsistency in advising the DA62 of the expected occurrence of hazards caused by wake turbulence from traffic on approach to the parallel runway 30R. Based on these observations, the Investigation believes that there is sufficient reason to issue a prompt safety recommendation to re-emphasize to pilots and air traffic controllers the importance of maintaining a minimum safe distance and issuing essential traffic information such as advising aircraft of the expected occurrence of hazards caused by wake turbulence.
The investigation is ongoing. We will update this article as more information emerges.
DANS and Dubai Airports agreed to continue the calibration flights and necessary instrument calibration flights in a sterile airport environment and issued temporary instructions for the required days, in which ATC procedures were detailed. All commercial operation…ceased during these flights on 24th, 26th and 27th May 2019.
The GCAA is in the process of publishing a Safety Decision containing mandatory requirements for ensuring that ATC procedures are developed, implemented and maintained for issuing essential traffic information, including the advice to aircraft of the expected occurrence of hazards caused by turbulent wake. Additionally, a Safety Decision is being prepared to ensure standardised procedures are developed, implemented and maintained for the management of unusual or abnormal aircraft operations, including calibration flights, as it was found that regulations, standards and recommended practices and procedures did not specifically cover the management of such operations, e.g. calibration flights.
The Operator has contacted all company pilots to raise their awareness of minimum separation criteria as detailed in a Eurocontrol document titled “European Wake Turbulence Categorisation and Separation Minima on Approach and Departure”. A training course on wake turbulence effects during take-off and landing, and a practical upset recovery training is being developed. The Operator is in the process of reviewing the procedures and processes for calibration flights.
In their Preliminary report the AAIS recommended that:
The GCAA issue a safety alert to all air navigation service providers in the United Arab Emirates and to all operators of light aircraft, to enhance awareness among pilots and air traffic controllers of their separation procedures, particularly under visual flight rules.
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