Accident de Havilland Canada DHC-6 Twin Otter 300 9N-AET, Sunday 29 May 2022
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Date:Sunday 29 May 2022
Time:10:10
Type:Silhouette image of generic DHC6 model; specific model in this crash may look slightly different    
de Havilland Canada DHC-6 Twin Otter 300
Owner/operator:Tara Air
Registration: 9N-AET
MSN: 619
Year of manufacture:1979
Total airframe hrs:41336 hours
Cycles:71338 flights
Engine model:Pratt & Whitney Canada PT6A-27
Fatalities:Fatalities: 22 / Occupants: 22
Other fatalities:0
Aircraft damage: Destroyed, written off
Category:Accident
Location:Sanosware -   Nepal
Phase: En route
Nature:Passenger - Scheduled
Departure airport:Pokhara Airport (PKR/VNPK)
Destination airport:Jomsom Airport (JMO/VNJS)
Investigating agency: Nepal AAIC
Confidence Rating: Accident investigation report completed and information captured
Narrative:
Tara Air flight 197, a DHC-6 Twin Otter 300, impacted a mountainside at 14500 feet while on a domestic flight from Pokhara to Jomsom, Nepal. All 22 occupants suffered fatal injuries.

The flight was the first of five Tara Air flights from Pokhara to Jomsom that day and scheduled to depart at 06:15 hours.
The flight was delayed because the Lete Pass on the route was covered up with clouds. The Twin Otter finally departed at 09:55, after two aircraft of Summit Air had departed for Jomsom.
9N-AET was supposed to take-off as the second flight but the captain seemed hesitant to commence the flight due to a weather report from the first Summit Air flight that, the en-route weather was not favorable for VFR flights and critical around LETE and TATOPANI.
The cockpit voice recording revealed that someone, either ground staff or some intimate passenger to the crew, advised the PIC strongly to conduct the flight.

The aircraft took off from Pokhara from runway 04. The Tower controller instructed to "report 5 DME northwest runway 04". Then after departure the aircraft turned left to maintain a heading of 345 and planned to join heading 305 degree towards Ghodepani. After four minutes, flight 197 reported, "Now on course... 6000 climbing and ETA Jomsom 32" (0432 UTC). At 04:21 UTC flight 197 reported to Pokhara Tower as position approaching Ghodepani 12000 climbing for 12500.
After 6 Seconds ATC Pokhara asked flight 197, "confirm would like to change level and TRA 197 replied, “No Ma'am we have crossed Ghodepani and like to be on”. Pokhara Tower
instructed, “Tara 197 contact Jomsom Tower 122.5”
CVR recordings show that after flight 197 crossed Ghodepani, the PIC was not comfortable with the en-route weather. However, the flight was continued following the advice of the preceding Summit Air flight. At 04:26 UTC, flight 197 made the first contact with Jomsom AFS and reported its position to which Jomsom Tower conveyed the prevailing weather as "Wind South Westerly up to 30 kts, QNH 1019, Temp 18º". The PIC of flight 197 reconfirmed twice if the wind was maximum, up to 30 kts and currently South Westerly 25 kts. The crew was discussing about the bad weather being encountered and the PIC himself voiced his dissatisfaction about the behavior of other pilots who conduct VFR flights in such unfavorable weather. The CVR recordings reveal that the aircraft was encountering clouds and the PIC was trying his best to remain clear of the clouds.
The PIC was searching for light and brighter areas and adamantly heading towards it. The aircraft was maintaining 12000 ft and was in a climbing attitude.
During the continuous attempts of crew to avoid the clouds with Terrain Avoidance and Warning System (TAWS) inhibited, the aircraft struck rocky terrain at an altitude of 4050 meters AMSL at Sanusare Mountain.

The cockpit voice recoerder readout showed that the aural GPWS warning, a function of TAWS, was triggered approximately 3 seconds prior to the impact. However, there was no aural warning of enhanced Forward Looking Terrain Alert (FLTA), Premature Descent Alert (PDA), and Imminent Terrain
Impact (ITI) Alert/Warning function of TAWS.
Further investigation of tht TAWS showed that it was configured to use GPS altitude, however no data was received by the system. This was likely caused by the misconfiguration of the RS-232 output format from the Garmin GPS receiver. As a result Corrected Barometric Altitude (CBA), computed by the Air Data Computer (ADC), was the only altitude input. In order to compute a reliable CBA, a regional barometric pressure setting must be entered into the ADC. This had not been done, so during the previous flights the CBA was off by 73 to 866 feet.
Due to an overabundance of nuisance alerts, the TAWS was inhibited.

Probable Cause:
The probable cause of this accident was the flight crew's failure to monitor and maintain the proper course while inadvertently flying in IMC conditions with the aircraft Terrain Avoidance and Warning System [TAWS] inhibited which resulted into a CFIT accident.
Contributing factors:
1. The flight crew's failure to follow the SOP of company
2. The aircraft flight operation with TAWS inhibited during deteriorating en-route weather condition.
3. Loss of situational awareness of crew
4. Deteriorating en-route weather
5. Less experienced copilot for that sector and high crew gradient
6. Poor CRM during the flight
7. The whole cockpit duties [both PF and PM] were undertaken by the PlC, which likely impaired his performance.
8. Underutilization of the available Navigation instruments

Accident investigation:
cover
  
Investigating agency: Nepal AAIC
Report number: final report
Status: Investigation completed
Duration: 11 months
Download report: Final report

Sources:

kathmandupost.com
AAIC Press release

History of this aircraft

Other occurrences involving this aircraft

3 April 1984 7P-LAG Lesotho Airways 0 near Quthing Airport (UTG) sub

Statistics

  • 3rd worst accident in 2022
  • 6th worst accident of this aircraft type
  • 6th worst accident of this aircraft type at the time

Location

Images:


photo (c) Flightaware; 29 May 2022

Revision history:

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