Nigerian investigators probing a loss of thrust in both engines of a Hawker 900XP have disclosed that one of the powerplants – which had stopped responding to thrust commands – became responsive again after the aircraft landed.
The jet, operated by Flybird Aircraft Management Services, had departed Abuja for Accra on 6 December last year.
But as it climbed out of 26,000ft the crew “heard a loud bang” from the right-hand Honeywell TFE-731-50R powerplant, says the Nigerian Safety Investigation Bureau in preliminary findings.
It says that, according to the crew, the engine’s temperature was increasing and they reduced it to idle thrust, with vibrations continuing to be felt.
The captain took control of the aircraft and the crew decided to return to Abuja.
After initiating the return and being cleared to descend to 5,000ft the crew carried out the engine-failure checklist, about 13min after the initial bang.
As the first officer achieved visual contact with runway 22, the captain remarked, “Number two is out”, to which the first officer replied: “Number one is out, number two is out.”
The inquiry says the crew noticed that the right-hand engine “was not responding to thrust commands”.
“We have lost two engines,” the crew stated as they declared an emergency to air traffic control for the second time.
The aircraft continued to descend and landed safely about 3min later. None of the three crew members or the sole passenger was injured.
According to the inquiry, the crew stated that the right-hand engine “regained response” to thrust commands after landing.
Investigators have been analysing flight-data recorder information but have yet to determine the reasons for the in-flight loss of power from both engines.
“Without the thrust-lever angle parameter, the engine thrust commands are not readily apparent to the investigation,” says the safety bureau.
But it says the right-hand powerplant showed a spike in inter-turbine temperature to around 1,000°C at 26,000ft.
A reduction in this engine’s speed and fuel flow immediately after the spike indicates a “possible reduction in [thrust-lever angle] for the associated engine”, because the same parameters for the left-hand engine remained at their previous levels.
Visual examination of the right-hand engine revealed “some damage” around the exhaust, it adds, the extent of which is still being ascertained.
