9th of September 2024, Engine Torque, Blog #719
- V2Aviation
- 20 minutes ago
- 4 min read
An ATR 42-500 was scheduled to be operated on a 6-sector day in Papua, Indonesia, 366 days ago to date. After three uneventful flights, the fourth flight was scheduled to depart Serui Airport (ZRI/WABO) with Jayapura- Sentani Airport (DJJ/WAJJ.
On board the aircraft, a crew of four (two pilots and two cabin attendants) and 44 passengers (including one engineer and one flight operations operator from the operator). The captain was to be the pilot monitoring (PM), with th eco-pilot operating as pilot flying (PF) for this sector. The weather was good. The following weather was reported approximately 30 minutes before the flight's departure;
Wind - 240°/ 6 knots
Visibility & clouds - good visibility and no low cloud (ceiling and visibility OK)
Temperature - 30°C
Dewpoint - 24°C
Pressure - 1,006 hPa
Forecast - no significant change expected
At 10:25 lt (local time), the start-up clearance was issued with a cruise altitude of 13.500 feet being stated. Eight minutes later, the crew started to taxi the aircraft to the designated take-off runway 28 via taxiway Alpha. The take-off clearance was issued at 10,35 lt after the crew reported ready for departure to ATC.
Engine power was increased, and the aircraft started to accelerate down the runway. During the take-off roll, the propeller revolutions per minute (NP) of both engines reached 100%. One second later, the NP of engine number 2 decreased while the NP of engine number 1 remained steady at 100%. At the same time, the torque of engine 1 was 88% and engine 2 was 85%. Two seconds later, the torque of engine number 1 decreased to 90% while the torque of engine number 2 passed 100% and continued to increase to a maximum 116%. Another seven seconds later, the NP engine number 1 was 100 % and the NP engine number 2 was 72%. The torque of engine number 1 was 90% and the torque of engine number 2 was 116%. Nine seconds later, the Propeller Electronic Control (PEC) number 2 detected an internal fault for 16 seconds. During this time, the crew observed a split in engine performance, and the captain decided to abort the take-off. The speed at the time of the initiation of the aborted take-off was 109 knots.
As the aircraft decelerated, the Propeller Electronic Control (PEC) number 1 fault occurred for two seconds. At the same time, the aircraft started to pull to the left, leaving the paved area of the runway and coming to a stop 1,200 meters from the beginning of Runway 28.
After the aircraft stopped, the cabin crew was expecting an evacuation command from the PIC for 10 seconds, but there was no such command. The cabin crew then decided to evacuate the passenger using all four doors. Among the passengers were four Airport Rescue and Fire Fighting (ARFF) personnel of Serui Airport who assisted the FA during the passenger evacuation process. Three of the crew members and 18 passengers sustained injuries (in varying degrees) during the accident. There was no post-accident fire.
The aircraft was substantially damaged. All landing gears and the left engine propeller blades were broken, and the left wing tip was bent. The fuselage skin aft of the cockpit section was wrinkled. In the cockpit area, the central and pedestal panels were pulled backwards. The instrument panel was removed from its mountings. The Komite Nasional Keselamatan Transportasi (KNKT) of the Republic of Indonesia is currently investigating this accident. In their preliminary report (which served as the source for this blog), they reported, amongst others, the following findings;
The occurrence flight was the fourth of six planned flights of the day. The first three flights were uneventful.
The Pilot in Command (PIC) acted as Pilot Monitoring (PM) and the Second in Command (SIC) acted as Pilot Flying (PF).
The aircraft was operated within the weight and balance envelope.
During takeoff, after both power levers advanced to the notch, both engines' torque and NP increased as expected. After that, the right engine torque continued to increase to a maximum of 116%, while the left engine torque remained at 90%. At the same time, NP of the right engine dropped to 72% while NP of the left engine remained at 100%.
The aircraft speed continued to increase to about 100 knots, when both pilots realised that the aircraft engines had an abnormal condition. The PIC decided to cancel the take-off by retarding the power levers and selected to reverse. The aircraft then veers to the left of the runway and stops about 1,200 meters from the beginning of Runway 28.
After the aircraft stopped, the FA waited for an evacuation command from the PIC for 10 seconds, but there was no command from the PIC. The FA then decided to evacuate the passenger using all four doors.
The aircraft was substantially damaged as a result of this accident.
Both pilots sustained serious injuries, one flight attendant and 18 passengers had minor injuries.
The exact cause will be determined in the final report. The preliminary report can be accessed by clicking on the .pdf file below;