German investigators have determined that the fire which destroyed a Ukrainian Antonov An-12 transport at Leipzig originated in the vicinity of the auxiliary power unit.
Seven personnel were on board the aircraft, which was preparing to depart on 9 August for the Russian city of Mineralnye Vody with a 3t cargo of nearly 49,000 chicks.
German investigation authority BFU says the pilots started the APU, then the outboard left-hand Motor-Sich AI-20M engine. Once this was running the crew started the outboard right-hand engine, but the co-pilot heard a muffled bang and received an APU fire indication.
One of the flight engineers climbed through the emergency hatch in the cockpit floor to look outside, and reported that the APU – which is located in a fairing behind the left-hand main landing-gear – was burning.
Initial attempts to extinguish the fire were unsuccessful. Six minutes after being cleared for engine start, the crew alerted the control tower and evacuated the aircraft.
BFU says the first fire-fighting foam attack on the An-12 occurred 5min later. But the aircraft, to which 22,800 litres of fuel had been uplifted, was gutted by the blaze.
The An-12 (UR-CAG) was a 44-year old airframe and BFU says its Aviamotor TG-16M APU, built in 1975, had undergone three overhauls between 1983 and 2007. It was installed in the freighter in September 2012, with the last maintenance performed in April 2013.
While the fire spread quickly and fiercely, melting many smaller components, both flight recorders were retrieved from the aircraft. The remains of the APU were salvaged and sent to Braunschweig for examination.