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Winnipeg, Manitoba, 1 November 2022 — In its investigation report (A20C0107) released today, the Transportation Safety Board of Canada (TSB) identified multiple contributing factors leading to a 2020 runway excursion in Naujaat, Nunavut.
On 26 November 2020, a Calm Air International LP Avions de Transport Régional ATR 42-300 aircraft was conducting a flight from Rankin Inlet, Nunavut, to Naujaat, Nunavut, with three crew members on board. While on descent to Naujaat Airport, the crew observed abnormally low propeller rpm indications on the left engine. Shortly after touchdown, 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 and sustained substantial damage. The captain received serious injuries.
The investigation determined that 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, which locks the blade pitch and prevents reverse thrust from activating. The propeller remained in that condition until the aircraft landed. The investigation also determined that 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. Immediately on touchdown, reverse thrust was selected by the pilot flying, resulting in the aircraft entering an asymmetric thrust state. Due to the asymmetric thrust, directional control of the aircraft could not be maintained, and the aircraft exited the landing surface of the runway.
Following the occurrence, the operator issued a Flight Operations Bulletin, which describes the condition known as pitch lock, possible causes for this condition, how to identify it, and the actions to be taken if this condition is suspected.
Check the complete report
Propeller malfunction led to 2020 runway excursion in Naujaat, NU
Moderators: sky's the limit, sepia, Sulako, lilfssister, North Shore
Re: Propeller malfunction led to 2020 runway excursion in Naujaat, NU
Standard procedure on a PW100 is to wait for a Low Pitch call after touchdown before selecting reverse.
On occasion, a light could fail to illuminate due to an electrical issue. But one should be especially sure to get the low pitch indication if there has been a propeller anomaly before selecting reverse.
It sounds like the captain to just slammed ‘em into reverse before the F/O had a chance to say something. Bad idea. Even if they did get two low pitch lights in a situation of propeller anomalies, I would suggest no reverse or minimal reverse.
One can easily identify a pitch locked prop while in flight by simply moving the throttle(or changing airspeed). If the rpm does follow the throttle, you have a pitch lock and will not get reverse as it is now a fixed pitch prop.
Different engine types could have different issues. The blade angle at which it pitchlocked can have an effect on the situation. The blades are much coarser in cruise than on climb. On some engine types, there is a very narrow allowable rpm range. This can decrease the ability to reduce power for descent as the pitchlocked prop will decrease rpm as the power is reduced. Then again, rpm increases as speed increases on the descent. Engine power output increases with a decrease in altitude. With a pitch locked prop situation resulting in the pilot having to keep the throttle significantly forward of the idle position once slowed down at a low altitude, resulting in an increasing power differential. Typically, an engine would be shut down if it has a pitch locked prop.
I was on a flight that had a pitchlocked prop. The malfunction became evident on short final. There were uncertainties about what was happening at that point but after touchdown and in the ground range, there was no light illumination on one of the engines. The captain seemed to want to experiment deciding to gently try a bit of reverse even after being told about the issue which led to some actual yawing/slight sideways movement/lateral wheel skipping. The prop was then feathered and the rest of the rollout presented no problem. There was another flight with an over speed due to oil loss, where it likely pitch locked at that point, as a safety mechanism was designed to do that to minimize overspeed. The engine was shut down quickly.
There is a history of a nasty accident(aircraft out of control quickly) on a PW100 powered airplane although that was a reversal in flight. Still, any prop anomaly should be taken seriously. It can ruin your day.
Quite possibly a different issue but this did arrive in the email today.....
"Occurrence Summary:
C-GDSS, an ATR-42-300 operated by Calm Air as MO240 was conducting a flight from Winnipeg
Airport, MB (CYWG) to Sanikiluaq, NU (CYSK) with 14 passengers and 3 crew members on board.
When landing on runway 27, the crew lost lateral control of the aircraft, which veered to the right
and the right main landing gear door struck a runway light. The aircraft remained on the runway
between the runway lights. The crew regained centerline, brought the aircraft to a stop and then
taxied to the terminal ramp.
There were no injuries and the aircraft sustained minor damage to the right main landing gear
door. The company deployed maintenance and downloaded the quick access recorder and intends
to ferry the aircraft to CYWG."
On occasion, a light could fail to illuminate due to an electrical issue. But one should be especially sure to get the low pitch indication if there has been a propeller anomaly before selecting reverse.
It sounds like the captain to just slammed ‘em into reverse before the F/O had a chance to say something. Bad idea. Even if they did get two low pitch lights in a situation of propeller anomalies, I would suggest no reverse or minimal reverse.
One can easily identify a pitch locked prop while in flight by simply moving the throttle(or changing airspeed). If the rpm does follow the throttle, you have a pitch lock and will not get reverse as it is now a fixed pitch prop.
Different engine types could have different issues. The blade angle at which it pitchlocked can have an effect on the situation. The blades are much coarser in cruise than on climb. On some engine types, there is a very narrow allowable rpm range. This can decrease the ability to reduce power for descent as the pitchlocked prop will decrease rpm as the power is reduced. Then again, rpm increases as speed increases on the descent. Engine power output increases with a decrease in altitude. With a pitch locked prop situation resulting in the pilot having to keep the throttle significantly forward of the idle position once slowed down at a low altitude, resulting in an increasing power differential. Typically, an engine would be shut down if it has a pitch locked prop.
I was on a flight that had a pitchlocked prop. The malfunction became evident on short final. There were uncertainties about what was happening at that point but after touchdown and in the ground range, there was no light illumination on one of the engines. The captain seemed to want to experiment deciding to gently try a bit of reverse even after being told about the issue which led to some actual yawing/slight sideways movement/lateral wheel skipping. The prop was then feathered and the rest of the rollout presented no problem. There was another flight with an over speed due to oil loss, where it likely pitch locked at that point, as a safety mechanism was designed to do that to minimize overspeed. The engine was shut down quickly.
There is a history of a nasty accident(aircraft out of control quickly) on a PW100 powered airplane although that was a reversal in flight. Still, any prop anomaly should be taken seriously. It can ruin your day.
Quite possibly a different issue but this did arrive in the email today.....
"Occurrence Summary:
C-GDSS, an ATR-42-300 operated by Calm Air as MO240 was conducting a flight from Winnipeg
Airport, MB (CYWG) to Sanikiluaq, NU (CYSK) with 14 passengers and 3 crew members on board.
When landing on runway 27, the crew lost lateral control of the aircraft, which veered to the right
and the right main landing gear door struck a runway light. The aircraft remained on the runway
between the runway lights. The crew regained centerline, brought the aircraft to a stop and then
taxied to the terminal ramp.
There were no injuries and the aircraft sustained minor damage to the right main landing gear
door. The company deployed maintenance and downloaded the quick access recorder and intends
to ferry the aircraft to CYWG."
