Yeti AT72 at Pokhara on Jan 15th 2023, lost height on final approach, both propellers went into feather

Last Update: March 28, 2024 / 11:44:26 GMT/Zulu time

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Incident Facts

Date of incident
Jan 15, 2023


Flight number

Pokhara, Nepal

Aircraft Registration

Aircraft Type
ATR ATR-72-200

ICAO Type Designator

On Mar 28th 2024 Nepal's Aircraft Accident Investigation Commission (AAIC) released their final report via the French BEA concluding the probable causes of the crash were:

The most probable cause of the accident is determined to be the inadvertent movement of both condition levers to the feathered position in flight, which resulted in feathering of both propellers and subsequent loss of thrust, leading to an aerodynamic stall and collision with terrain.

The contributing factors to the accident are:

- High workload due to operating into a new airport with surrounding terrain and the crew missing the associated flight deck and engine indications that both propellers had been feathered.

- Human factor issues such as high workload and stress that appears to have resulted in the misidentification and selection of the propellers to the feathered position.

- The proximity of terrain requiring a tight circuit to land on runway

- This tight circuit was not the usual visual circuit pattern and contributed to the high workload. This tight pattern also meant that the approach did not meet the stabilised visual approach criteria.

- Use of visual approach circuit for RWY 12 without any evaluation, validation and resolution of its threats which were highlighted by the SRM team of CAAN and advices proposed in flight procedures design report conducted by the consultant and without the development and approval of the chart by the operator and regulator respectively.

- Lack of appropriate technical and skill based training (including simulator) to the crew and proper classroom briefings (for that flight) for the safe operation of flight at new airport for visual approach to runway 12.

- Non-compliance with SOPs, ineffective CRM and lack of sterile cockpit discipline.

The AAIC analysed that both propeller were found "with a pitch at
impact close to feather position (about 12 degrees max below feather) and continued:

During the course of the investigation, in particular, the analysis of the flight recorder data, the recorded parameters indicated that the propellers were most likely moved to the feathered condition when the PF requested for Flaps 30 during the approach. The condition levers and flap lever are located next to each other on the pedestal and closer to the co-pilot seat.

The FDR only recorded 187 parameters of which the position of the condition levers were not recorded. It was through the detailed examination of aircraft components from the wreckage that provided corroborating evidence for the flight recorder data as follows:

- The witness marking from the propeller hub indicated that the propeller were close to the feathered angle.

- The right hand MFC super advance BITE records did not indicate any auto feather command from the RH AFU.

The witness marks from the pedestal indicates that the left condition lever was in the feathered position. Although the right hand condition lever did not have witness marks it is probable that the lever was also in the feathered position based on the FDR data and MFC examination corroboration. All evidence gathered from the detailed examinations appear to indicate that the propellers were manually selected to the feathered position.


The active “Super Advanced BITE" zone of the read and decoded MFC non-volatile memory from the retrieved CPU card reveals no automatic feathering command activation by the MFC.


There was no evidence of engine failure in FDR data analysis until the impact of the aircraft. Both the engines were running at idle condition till the time of impact. Hence the possibility of engine failure is ruled out. There was no evidence of any systems failure either. Hence, the failure of the aircraft systems e.g. hydraulic, flight control and other major components can, too, be ruled out. The probability that the power-plants, systems, or structural failures or any other mechanical malfunction contributing to the accident can be ruled out. The Commission examined the maintenance history of the aircraft and found that all the airworthiness directives and service bulletins had been complied with as per the maintenance requirements within the prescribed time frame. The technical logs and log books show that the maintenance works, major inspection works and modifications were carried out as per the approved maintenance program and bulletins. No technical defect was found in the technical logbook prior to the flight. On the basis of available evidences, any technical or mechanical reason has been discounted.


Detailed examinations of the pedestal showed:

- The flap lever was locked in the 30° position, with damage to the lever consistent with the application of a high force from the rear during the accident. As a result, the lever was clearly in the 30° position at impact.

- Traces and impact on the Condition Lever 1 rail are consistent with a FEATHER position at impact (no other impact on other position on the rail of Condition lever 1);

- No trace on the Condition Lever 2;

- Traces and damage on Power levers 1 and 2 are consistent with a position forward (zone corresponding to high power).

- The Gust Lock lever was moved rearward upon impact during the accident sequence and deformed. The lever was therefore forward before impact (normal position in flight).


Operational (Flight) Analysis

The departure from KTM was normal.

Before reaching MANKA, the PM expressed intentions to familiarize PF on RWY 12 if traffic permits and briefed on the visual approach procedure for RWY 12 emphasizing the need of a sharp turn during final approach. The intent for runway change was to clear PF from RWY12 under IP supervision. However, this familiarization from RWY12 was not planned by the operator‟s operations department.

When the aircraft was at 15 miles to PHR, 6500ft, the PM requested and received clearance for landing on RWY 12. After receiving approval for RWY12, the PM briefed the PF on manoeuvring techniques, the circuit, heading and radial to be followed as well as the altitude to be maintained. After joining downwind, RWY12, the crew announced flap 15. The PM continued briefings on visual landmarks, obstacle, runway orientation etc. The crew then announced flap 30. However, it was found the checklist in all phases of flight was not carried out appropriately as per SOP.

PF voiced concerns about ELEC lights but CVR records do not show any response from PM. The PF then asked if they should continue the turn to which the PM responded “positive”. Subsequently, PM advised on increasing the power, but PF reported that there was no power. and PF once again repeated that there was no power, no torque. The FDR records show the power levers were moved from flight idle position to RAMP position.

The PM who was occupying right hand seat had made 2 landings at RWY 12; one from left hand seat and the other from right hand seat. The flight was first for PF who was occupying left hand seat. Previous experience, type of flight and seating position, etc. might have affected the situational awareness in the critical phase of the flight.

From the retrieved FDR data, flight path of the event flight as well as another flight on 12th Jan, 2023 where other set of crews landed on RWY 12 were recovered.

The flight trajectories show that the flight path gradients were not as per ATR 72-212A version 500‟s flight manual. Due to the tight circuit and shortened final leg of RWY 12, the stabilization criteria for visual approach couldn‟t be maintained at the height of 500 ft. AGL. Sequence of events of the accident flight resembled previous flights of the day to Pokhara, except for when flap 30 was called (yet not acknowledged by the other crew) on the accident flight, the flaps were not deployed; rather both propellers went to feather resulting in loss of torque in both engines. However, when the flaps 30 were finally deployed, there were no recorded callout from either cockpit crew.


Human Factors Analysis:


A 72-hour history of both crewmembers indicated that fatigue and their health issues were not a factor prior to the accident. Both pilots were reported to have eaten routine foods, went to bed, and rose at routine hours.

The PF owned a noise-cancelling headset and this type of device has been known to decrease the sensitivity of acoustical sensory cues in flight and may have contributed to the crew not perceiving the accidental feathering of both engines. The PM did not own noise-cancelling headset.

The CVR transcript captured a flight deck environment rich with discussion on the appropriate way to fly a visual approach into the new Pokhara Airport. Both pilots were experiencing high workload, distractions to the external environment, and may have impacted on effective CRM within the cockpit. This may have lead them to not follow the checklist properly in critical phases of flight. The crew were most probably distracted due to excessive conversation in cockpit because the flight was first for the PF and the PM was occupied with providing instructions and was not focused on the PM duties.


Although weather conditions and time of day were optimal, challenges provided by the opening of the new Pokhara Airport certainly played a role in crew distraction. The new airport had opened only two weeks prior to the accident flight. With both crewmembers having extensive experience flying in Nepal, and experience flying to/from the old Pokhara Airport, because the old Pokhara Airport was very close to the new Pokhara Airport, it can be assumed that both were very familiar with the terrain around Pokhara.

The crew requested to land on runway 12, necessitating flying a downwind, base and final leg, instead of a straight in approach that they were initially cleared for. This may have been part of the instructor pilot‟s decision to ensure proficiency at approaching the airport from both directions.

Manoeuvring and configuring the aircraft for a visual approach to a new airport could have certainly increased the workload and stress on both crewmembers. A visual approach requires attention outside of the aircraft by the PF and adequate support from the PM to ensure all checklist items and aircraft configuration settings are done correctly. In this case it is likely that both crewmembers were focused outside the aircraft which could result in distractions in carrying out the PM functions.


The centre pedestal design of the ATR 72-212A version 500 does not directly preclude inadvertent movement of the propeller condition levers in lieu of the flap handle (or vice versa), but some design considerations mitigate this risk.

In order to move a propeller condition lever, the pilot must first activate a trigger below the lever to disengage the lever from a detent. Similarly, the flap handle also has detents, but there is no trigger. The entire flap handle is raised to lift the lever out of the detent.

Additionally, the shape of each lever is such that they would feel different when touched. There are different number of levers (two for condition levers and one for flap), the colours are different and their locations on pedestal also differ. The flap handle is shaped like an airfoil, the propeller condition levers have ridged knobs, the thrust levers are smooth and cylindrical, and the landing gear handle is shaped like a wheel. These are all industry standard design considerations.

Consideration has been given by the investigation to the alignment of the flap handles in the 15 degree position which is geometrically close to the condition lever AUTO position. Given the previous design features therefore, one has to consider other inputs such as workload, confirmation bias and the operational context that contributed to the pilot monitoring actions.

The CVR transcript indicated that there was likely a chime that followed the feathering of both propellers. Considering ATR 72 systems failures resulting from Np drop due to feathering in flight, this was likely an electrical, anti-icing or hydraulic system caution.

The CVR transcript also highlighted that the crew was making configuration changes prior to landing well below 1,000‟ AGL which could contribute to increase the crew workload.


The configuration of the aircraft for the visual approach to Pokhara may have been carried out at an altitude lower than desirable as stated in the operator‟s SOPs. The operator‟s SOP for Task Sharing indicates “In all situations, BOTH CMs must be aware of all important selections or switching and maintain situational awareness throughout the flight. Cross monitoring of Speed Bug / Altimeter settings / changes in frequencies / changes in aircraft configuration (Gear / Flaps) is mandatory.”

Because both crewmembers should be aware of configuration changes as indicated above, it would be reasonable to expect Yeti to have a crosscheck or confirmation by both crewmembers to ensure appropriate changes are carried out. However, because of the increased workload and stress, it appears as though this procedure to crosscheck and confirm
switch selections was not followed.

The available recorded data, coupled with witness video and the teardown report of the centre pedestal, point to one likely scenario: The most probable sequence of events of the accident is a selection of both Condition Levers to Feather position, which resulted in feathering of both propellers and subsequent loss of thrust. Without change of the aircraft flight path, the loss of speed resulted in a loss of control in flight. Contributing to this accident was the high workload associated with unfamiliar airport operations and subsequent loss of recognition of undesired aircraft state.

Visual Approach Procedure

At the time of the accident Pokhara had two operational airports, Pokhara airport and Pokhara International airport (VNPR). Pokhara airport was used for domestic flights whereas VNPR was used for international flights. VNPR was newly opened on 1 January 2023. At the time of the accident, VNPR had not yet published their instrument approach procedures and was operating as a Visual Flight Rules (VFR) only airport.

However, procedures to allow for such visual approaches had not been developed. The operator had developed a visual circuit pattern internally into VNPR and attempted for the aircraft to remain clear of surrounding terrain and Pokhara domestic airport. This resulted in an approach that required tight turns during the descent and would result in the aircraft being at a lower altitude once aligned to RWY 12. This did not meet the requirements for a stabilised visual approach. This would result in a challenging approach, increase the flight crew‟s workload and decrease the safety margin.

The operator had carried out demonstration flights to VNPR prior to it opening; however the demonstration flights were for VFR landings on RWY 30 and departure on RWY 12. The operator had also developed a visual circuit for landings on RWY 12 but did not carry out any demonstration flights for this visual approach.

CAAN has a process for operators to develop and propose approaches into airports. The approval process also allows operators to conduct validation flight with the approval of CAAN to demonstrate the viability of the design approach.
Incident Facts

Date of incident
Jan 15, 2023


Flight number

Pokhara, Nepal

Aircraft Registration

Aircraft Type
ATR ATR-72-200

ICAO Type Designator


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