Accident Antonov An-74TK-100 RA-74044,

ASN Wikibase Occurrence # 319141

Date:	Monday 3 August 2020
Time:	10:00
Type:	Antonov An-74TK-100
Owner/operator:	UTair-Cargo
Registration:	RA-74044
MSN:	36547097936
Year of manufacture:	1994
Total airframe hrs:	13302 hours
Cycles:	6496 flights
Engine model:	Lotarev D-36-3A
Fatalities:	Fatalities: 0 / Occupants: 11
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	Gao Airport (GAQ) - Mali
Phase:	Landing
Nature:	Cargo
Departure airport:	Bamako Airport (BKO/GABS)
Destination airport:	Gao Airport (GAQ/GAGO)
Investigating agency:	MAK
Confidence Rating:	Information verified through data from accident investigation authorities

Narrative:
An Antonov An-72TK-100 transport plane, operating for the United Nations, suffered an accident on landing at Gao Airport, Mali.
The aircraft operated flight UNO 052P from Bamako to Gao, Mali. There were 7 crew members on board the aircraft and 4 passengers (representatives of the UN mission).
While en route, about 1 hr. 10 min after takeoff, the right engine generator failed. The captain initiated a descent and attempted to start the APU. At that moment the left engine generator failed as well. Two attempts to start the APU failed.
After about 20 minutes of flight, the batteries were completely discharged, which led to a complete loss of power supply on board the aircraft.
The crew continued the flight to Gao in VFR under the clouds. Landing approach at Gao was performed visually. Due to the on board powerloss, the flaps remained retracted.
The aircraft touched down at a distance of about 500 m from threshold of runway 25. Due to the power failure, the thrust reverser could not be used.
The aircraft could not be stopped on the runway and overran, coming to rest 389 meters past the end of the runway. Two crew members were injured, other crew members and passengers were not injured.

Conclusion:
The aviation incident occurred during rollout after landing, resulting in the longitudinal excursion of the aircraft beyond the runway and collision with a sewage collector during ground movement. The landing was performed on a fully unpowered aircraft with wing flaps retracted, without the possibility of using spoilers and engine reversers for braking. Immediately after landing, the wheel brake system failed due to its usage by the crew at speeds significantly exceeding the established FCOM maximum values for the An-74TK-100 aircraft. The landing under these conditions exceeded the expected operating conditions, as there is no data in the FCOM for its calculation and execution.

The most probable contributing factors were:
- The absence of information in the FCOM regarding landing calculation and crew actions during unpowered flight (landing with retracted flaps without the possibility of using spoilers and engine reversers) due to the aircraft developer's assessment of such a situation as practically improbable.
- Poor execution of pre-flight refueling of generator oil systems and a lack of proper control over their execution, leading to exceeding the permissible maximum oil level, its overheating in flight, melting of thermal sensors, and sequential automatic disconnection of two GP21 generators.
- Failure of the crew to adhere to standard operational procedures for the APU in-flight (failure to activate the APU compartment heater), as well as the preparation and start-up methods outlined in the FCOM, leading to the inability to start the APU and complete loss of power in the aircraft after the battery voltage dropped below the permissible value.

Accident investigation: