Calm AT42 at Naujaat on Nov 26th 2020, runway excursion on landing

Last Update: November 1, 2022 / 15:25:47 GMT/Zulu time

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Incident Facts

Date of incident
Nov 26, 2020

Classification
Accident

Airline
Calm Air

Destination
Naujaat, Canada

Aircraft Registration
C-FAFS

Aircraft Type
ATR ATR-42

ICAO Type Designator
AT42

Airport ICAO Code
CYUT

A Calm Air Avions de Transport Regional ATR-42-300, registration C-FAFS performing freight flight MO-464 from Rankin Inlet,NU to Naujaat,NU (Canada) with 3 crew on board, landed on Naujaat's (former Repulse Bay's) runway 34 (1040 meters/3400 feet long) at about 13:24L (19:24Z) but veered right off the runway and came to a stop with all gear off the runway on soft ground. There was one serious injury, the aircraft sustained substantial damage.

The airline reported "At about 1:30pm local time today, a cargo flight operated by Calm Air (Calm Air flight 464) left the runway at Naujaat Airport in Nunavut. No passengers were on board and the crew are receiving medical evaluations. Calm Air has informed Transport Canada and the Transportation Safety Board of the incident."

Nav Canada reported the aircraft C-FAFS sustained substantial damage in a runway excursion at Naujaat.

On Dec 2nd 2020 the Canadian TSB announced they are deploying a team of investigators to Naujaat.

On Dec 3rd 2020 the TSB reported the aircraft veered off the side of the runway 34, one minor injury occurred. The occurrence was rated an accident and is being investigated.

On Apr 21st 2021 the TSB updated their report now stating the captain received serious injuries after the crew lost directional control during landing on Naujaat's runway 34 causing the aircraft to veer off the east side of the runway. The aircraft came to a stop about 44 meters/144 feet off the edge of the runway. The TSB is investigating (Class 3 investigation).

On Nov 1st 2022 the TSB released their final report concluding the probable causes of the accident were:

Findings as to causes and contributing factors
These are conditions, acts or safety deficiencies that were found to have caused or contributed to this occurrence.

- A contaminant inside the left propeller’s high-pressure pump caused its pressure relief valve to fail. As a result, the propeller entered a pitch-lock condition and remained in that condition until the aircraft landed.

- Because there is no indication in the cockpit of a pitch-lock condition in flight, the flight crew were not aware that the propeller had entered a pitch-lock condition, and they continued the flight to Naujaat Airport (CYUT), Nunavut, without discussing any options.

- Immediately on touchdown, reverse thrust was selected by the pilot flying without confirmation that both LO PITCH lights had illuminated. With the left propeller in a pitch-lock condition, the selection of reverse thrust resulted in the aircraft entering an asymmetric thrust state.

- Due to the asymmetric thrust, directional control of the aircraft could not be maintained. As a result the aircraft exited the landing surface of the runway, travelled across rough terrain adjacent to the runway, and was substantially damaged.

- For undetermined reasons, the captain’s safety belt buckle released during the runway excursion and the captain’s head struck the forward upper area of the cockpit, resulting in serious head injuries.

Findings as to risk

These are conditions, unsafe acts or safety deficiencies that were found not to be a factor in this occurrence but could have adverse consequences in future occurrences.

- If flight crews do not assess abnormal situations as a team, there is a risk that they will not identify the nature of the abnormal situation and determine the most appropriate action to take.

- If the layout and design of a Quick Reference Handbook make it difficult for flight crews to find a procedure to address a malfunction, they may not take the appropriate actions quickly or efficiently, which may lead to an unsafe aircraft state.

The TSB provided following abstract:

While on descent, the crew observed abnormally low propeller rpm indications on the left engine. At 1326 Central Standard Time, shortly after touchdown on Runway 34 at Naujaat Airport, directional control was lost and the aircraft experienced a runway side excursion on the east side of the runway. The aircraft came to rest approximately 108 feet from the runway edge. The captain received serious injuries. The aircraft sustained substantial damage.

The TSB analysed:

The tear-down inspection of the left propeller control unit (PCU) revealed that it did not meet certification criteria and was slow to function at normal operating temperatures. Testing of the propeller’s high-pressure oil pump revealed that its pressure relief valve was not allowing adequate oil pressure to build up in the system.

Metal contamination from an undetermined source was found in the high-pressure pump’s pressure relief valve and was preventing the valve from sealing. The impeded seal decreased the pressure output from the high-pressure pump, and decreased the ability of the PCU to control the propeller pitch.

This decreased pressure output occurred during the cruise portion of the occurrence flight, around the same time the flight crew observed the unstable propeller indication. When the decreased pressure output occurred, in order to prevent the aerodynamic and centrifugal pressure from driving the propeller blades into fine pitch (and cause an overspeed condition), the propeller pitch-lock mechanism activated and locked the propeller blades in approximately 22.5° of pitch. This pitch-lock condition was, however, unknown to the flight crew.

...

On touchdown, 750 feet past the threshold, the pilot flying immediately selected reverse thrust, possibly due to the relatively short runway length; however, only the right propeller went into reverse. Almost simultaneously with the selection of reverse thrust, only the “LO PITCH” light for the No. 2 engine illuminated. The pilot monitoring did not have the time to identify the status of the LO PITCH lights and to make the “TWO LOW PITCH” callout before reverse was selected. The flight crew was unaware that the left propeller was in a pitch-lock condition and that reverse thrust was unavailable on the left side.

...

When the flight crew first noticed the abnormal propeller indications, they briefly discussed the situation, but they did not consult the QRH to find a solution to their situation, or take any other procedural action. The captain considered his options (i.e., return to Rankin Inlet Airport, shut down the left engine, or both); however, he did not specifically discuss these options with the first officer. This meant that the flight crew did not fully assess their situation as a team, which may have prevented them from identifying the nature of the malfunction that they were experiencing. This was not in accordance with CRM best practices.

...

The captain’s safety belt buckle released without input from the captain at some point during the runway excursion. The cause of the uncommanded safety belt release could not be determined.

Metars:
CYUT 262100Z 35005KT 15SM SCT092 M23/M26 A2965 RMK AC4 SLP046=
CYUT 262000Z 00000KT 15SM SCT150 BKN240 M23/M26 A2965 RMK AC4CI1 SLP047=
CYUT 261934Z 02006KT 15SM SCT150 BKN240 M23/M26 A2965 RMK AC3CI3 SLP047=
CYUT 261900Z 02010KT 15SM FEW150 BKN230 M23/M27 A2965 RMK AC2CI4 SLP047=
CYUT 261855Z 02010KT 15SM FEW096 BKN230 M23/M27 A2966 RMK AC2CI3 WSHFT 1839 SLP048=
CYUT 261800Z VRB03KT 15SM FEW094 BKN210 M23/M26 A2966 RMK AC2CI4 SLP048=
CYUT 261700Z 03003KT 15SM FEW094 BKN220 M23/M26 A2966 RMK AC1CI5 SLP049=
CYUT 261600Z 35003KT 15SM FEW150 BKN220 M23/M26 A2966 RMK AC1CI5 SLP050=
CYUT 261500Z 33004KT 330V030 15SM FEW100 BKN230 M22/M25 A2966 RMK AC1CI5 SLP049=
Incident Facts

Date of incident
Nov 26, 2020

Classification
Accident

Airline
Calm Air

Destination
Naujaat, Canada

Aircraft Registration
C-FAFS

Aircraft Type
ATR ATR-42

ICAO Type Designator
AT42

Airport ICAO Code
CYUT

This article is published under license from Avherald.com. © of text by Avherald.com.
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