Description

On 29 March 2016, an Antonov AN-26B (S2-AGZ) being operated by True Aviation on a non scheduled domestic cargo flight from Cox’s Bazar to Jessore, reported an engine failure immediately after takeoff and an immediate return was requested. After two discontinued approaches the crew subsequently lost control at a low altitude and were unable to recover before impact with the sea surface which destroyed the aircraft and caused the death of three of the four flight crew on board and serious injuries to the other one, the Navigator.

Investigation

An Investigation was carried out by the Bangladesh Aircraft Accident Investigation Group (AAIG). Both the FDR and the CVR were both recovered from the aircraft in an apparently externally undamaged condition and both were subsequently taken to the Ukrainian National Bureau of Air Accident and Incidents (NBAAI) for readout. The FDR data were successfully downloaded but the CVR data could not be recovered because of internal damage to the equipment. The recorded ATC communications with the aircraft were also available and a transcript was made.

It was noted that the 57 year-old Captain, who was acting as PF for the accident flight, had a total of 13,315 hours flying experience which included 6,896 hours on type and the 27 year-old First Officer had a total of 1,438 hours flying experience which included 1,195 hours on type. The aircraft flight crew also included a 36 year-old Flight Engineer and a 48 year old Navigator both with the same recorded total of 3,924 hours flying experience including 2,946 hours on type. All four crew members were of Ukrainian nationality and all appeared to have Russian as their first language but the three who made radio transmissions prior to and during the accident flight appeared to be able to use the English language without difficulty. Their Ukrainian licences had all been validated by the Bangladesh CAA to allow them to operate Bangladeshi-registered aircraft operated by a Bangladeshi AOC holder.

It was noted that the Cox’s Bazar-based aircraft operator was a commercial cargo air carrier that had been formed in 2013 and primarily carried baby shrimps from Cox’s Bazar to Jessore, refuelling as required en route at Chittagong. Initially, it had wet leased two AN-26B aircraft from a Ukrainian operator, one of which was the accident aircraft. In 2014, both aircraft were re-registered in Bangladesh and thereafter dry leased from the same owner.

It was established from FDR data that just four seconds after the takeoff roll of the fully loaded aircraft from runway 35 began and with the speed still below 40 knots, the left engine oil pressure recorded on the engine torque meter system “spontaneously decreased” from the value when full power had been set - 1,350 psi - to 925 psi, which indicated that takeoff power was reduced to cruise power. The takeoff was continued and after a 37 second takeoff roll, the aircraft became airborne at a speed of 107 knots. Almost immediately, the left engine failed completely. ATC were advised of an engine failure (although which engine was only clarified in a subsequent transmission) and an immediate return was requested and approved. Although no emergency was declared, the airport emergency services were put on standby by ATC. The flaps were retracted and the airspeed eventually settled at around 160 knots, close to the applicable minimum clean speed. A maximum altitude of 1,280 feet aal was reached and was not thereafter exceeded.

The aircraft was manoeuvred in a figure of eight pattern with the intention of returning to land on runway 17 but a satisfactory alignment on the extended centreline was not achieved and just under 6 minutes into the flight, it was discontinued from around 400/500 feet aal. The landing gear was selected up and the flaps were returned to zero, the latter in stages. The aircraft then began to position for a landing on runway 35, and entered the right downwind leg for that runway at about 1000 feet aal, clean and positioned, according to the surviving Navigator, “more or less” onto the extended centreline at 3½ nm and fully configured for landing. However, when approximately 1.2 nm from the threshold and at about 330 feet aal, a further go around was commenced and there were no further transmissions from the aircraft. Flap retraction was commenced but speed did not increase and FDR data showed that one minute and 20 seconds after beginning the go around, the aircraft had entered a stall when turning left into the direction of the failed engine at “a very low altitude” and at a speed of only around 120 knots from which no recovery was made. The wreckage of the aircraft was located approximately 1.6 nm west of the aerodrome in shallow sea water. All occupants had been recovered from the wreckage by local fishermen prior to the arrival of the emergency services, at which point, the sole survivor was taken to hospital with multiple injuries.

The weather at the time of the departure, for the two attempted visual approaches and when the loss of control occurred after the second go around was recorded as wind calm and the visibility 800 metres in fog. This was considered suitable for takeoff on the planned route but it was noted that there was no precision approach procedure at Cox’s Bazar, only an NDB.

The cause of the engine failure was not determined, but inspection of the 10th stage compressor did disclose evidence of internal damage from unknown causes.

The Causes of the accident were formally documented as follows:

• Failure to initiate a rejected take off during the takeoff roll following the indication of engine failure.
• Failure to adhere to the company SOP following the detection of the engine failure during takeoff
• Considering the poor visibility at Cox’s Bazar Airport, diverting to the alternate Chittagong Airport located only 50 nm away which had provision for an ILS approach could have helped the crew to complete a proper one engine out precision approach landing
• The aircraft flew at a much lower speed - 121 knots - than the minimum clean configuration speed which was 157 knots.
• The aircraft stalled while making a turn towards the side of the failed engine at a very low altitude.

Three Safety Recommendations were made as a result of the Investigation as follows:

• that All Relevant AN26 Flight Crew need to be properly trained to correctly apply the engine failure procedure during and immediately after takeoff.
• that Flight Crew CRM courses should give emphasis to the decision making process.
• that the Maintenance Status of all AN-26 aircraft shall be enhanced to ensure prevention of engine failure occurrences at any stage of flight.

The Final Report was completed on 20 March 2017 and subsequently published.

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• Rejected Take Off