Air Greenland Dash 8 gear collapse
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According to this article Ingen erstatning for ulykkesfly the Dash 8 will be scrapped. No replacement aircraft will be bought in the short term. A Dash 7 that was in the charter department will be placed in the route department until april, where a Dash 8-200 that was purchased before the accident should enter production.
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In the same article it is stated that "Havarikommisionen" (Danish accident investigation team) will publish a preliminary report on the accident next week.
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Originally Posted by Miraculix
So the preliminary findings are that...
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The final report is published and in part states:
Synopsis
Upon landing on runway 07 at Ilulissat (BGJN) in gusting crosswind conditions above the aircraft and the operator limited maximum crosswind components, the left main landing gear collapsed.
The aircraft skidded off the left side of the runway in a nose right position and into the safety zone.
The aircraft continued an increasingly sideways skid in a nose right position, skidded down a steep snow-covered slope and impacted a rocky area approximately 10 meters below the runway elevation.
One passenger and one crew member suffered minor injuries.
The aircraft was destroyed.
The accident occurred in dark night and under visual meteorological conditions (VMC).
The investigation did not result in recommendations being made. However, the AIB addressed an area of safety concern to Transport Canada (TC).
Summary
Adverse crosswind conditions at BGJN led to flight crew target fixation, a flight crew divergence from the operator’s stabilized approach parameters and a mental blocking of an appropriate decision on going around.
The flight crew divergence from the operator’s stabilized approach parameters induced a non-stabilized approach, which in combination with power levers retarded below flight idle in flight resulted in an accelerated rate of descent leading to a hard landing, with side load on the left main landing gear at touchdown.
The left main landing gear structural fuse pin sheared as a result of lateral and vertical overload stress.
Cycling the power levers between ground and flight range prevented an appropriate deceleration of the aircraft and prolonged the landing roll.
The prolonged landing roll combined with the application of full left rudder and no decisive use of reverse thrust on the side with the unaffected main landing gear made it impossible for the flight crew to maintain directional control.
The lack of directional control resulted in the aircraft running off the side of the runway and the safety zone, respectively.
Upon landing on runway 07 at Ilulissat (BGJN) in gusting crosswind conditions above the aircraft and the operator limited maximum crosswind components, the left main landing gear collapsed.
The aircraft skidded off the left side of the runway in a nose right position and into the safety zone.
The aircraft continued an increasingly sideways skid in a nose right position, skidded down a steep snow-covered slope and impacted a rocky area approximately 10 meters below the runway elevation.
One passenger and one crew member suffered minor injuries.
The aircraft was destroyed.
The accident occurred in dark night and under visual meteorological conditions (VMC).
The investigation did not result in recommendations being made. However, the AIB addressed an area of safety concern to Transport Canada (TC).
Summary
Adverse crosswind conditions at BGJN led to flight crew target fixation, a flight crew divergence from the operator’s stabilized approach parameters and a mental blocking of an appropriate decision on going around.
The flight crew divergence from the operator’s stabilized approach parameters induced a non-stabilized approach, which in combination with power levers retarded below flight idle in flight resulted in an accelerated rate of descent leading to a hard landing, with side load on the left main landing gear at touchdown.
The left main landing gear structural fuse pin sheared as a result of lateral and vertical overload stress.
Cycling the power levers between ground and flight range prevented an appropriate deceleration of the aircraft and prolonged the landing roll.
The prolonged landing roll combined with the application of full left rudder and no decisive use of reverse thrust on the side with the unaffected main landing gear made it impossible for the flight crew to maintain directional control.
The lack of directional control resulted in the aircraft running off the side of the runway and the safety zone, respectively.
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Would someone who is familiar with this type care to comment on the use (see animation) of beta to drop the aircraft on the runway and the full left rudder after touch down? I think both look a bit odd, but I fly a very different type, so maybe this is normal for the Dash 8?
Generally, Beta is the area where the propeller governor no longer governs the propeller RPM, as it has typically hit the low pitch stop.
There is a Flight Beta and a Ground Beta range present on the DH8, separated by the power lever position "Flight Idle". Flight Idle results in a prop blade position safe for flight and still noticeable forward thrust, while in Ground Idle, even some mild reverse thrust may be delivered (DISC and slightly above). In order to get to Ground Idle, one has to lift a release catch (below each power lever) before pulling the levers further backward. As going below Flight Idle is not allowed inflight on the DH8, depending on the mod status of the aircraft, the release catch will either trigger a warning whistle or be mechanically locked when no WoW is sensed.
For consequences of reducing below Flight Idle, although not on the DH8, the accident to a Luxair F50 in 2002 may be of interest. Nothing else is to be expected from a DH8 in the same situation.
Full left rudder may be owed to a crosswind from the right. As in a jet, the DH8 shows some weathervaning tendencies under reverse thrust. This can already show up in DISC. So a bit of rudder during landing is often needed under these circumstances and would not appear out of the ordinary to me in a normal landing on all 3 legs. In this landing with the aircraft drifting to the left, I am not so sure though.
There is a Flight Beta and a Ground Beta range present on the DH8, separated by the power lever position "Flight Idle". Flight Idle results in a prop blade position safe for flight and still noticeable forward thrust, while in Ground Idle, even some mild reverse thrust may be delivered (DISC and slightly above). In order to get to Ground Idle, one has to lift a release catch (below each power lever) before pulling the levers further backward. As going below Flight Idle is not allowed inflight on the DH8, depending on the mod status of the aircraft, the release catch will either trigger a warning whistle or be mechanically locked when no WoW is sensed.
For consequences of reducing below Flight Idle, although not on the DH8, the accident to a Luxair F50 in 2002 may be of interest. Nothing else is to be expected from a DH8 in the same situation.
Full left rudder may be owed to a crosswind from the right. As in a jet, the DH8 shows some weathervaning tendencies under reverse thrust. This can already show up in DISC. So a bit of rudder during landing is often needed under these circumstances and would not appear out of the ordinary to me in a normal landing on all 3 legs. In this landing with the aircraft drifting to the left, I am not so sure though.
the Danish Accident Investigation Board (DAIB) report...
Dash 8 Accident Report Cites Unstabilized Approach
In its report on a landing accident on January 1 this year involving a Bombardier Dash-8 at Ilulissat (BGJN) in Greenland, the Danish Accident Investigation Board (DAIB) focused on the crew’s failure to conduct a stabilized approach. While the Dash-8 was landing in a gusty nighttime crosswind that exceeded both the aircraft and the operator’s limitations, the left main gear collapsed and the aircraft skidded along the remainder of the runway and down a steep snow-covered slope to a point 35 feet below the runway elevation. One passenger and one crewmember among the 15 people on board received minor injuries, and the aircraft was destroyed. Investigators concluded that the crew failed to conduct a stabilized approach. The board said the crew reduced power to flight idle and then into the Beta range late in the approach, causing a hard landing that applied an excessive side load to the left main gear. Despite a nearly 90-degree crosswind gusting as high as 33 knots, the crew never attempted to execute a go-around. The investigation re-created the flight in an animation that showed the flightpath with a calculated Vref of 99 knots. At 1.5 miles from the end of the runway, the aircraft was still 30 knots above Vref and did not pass through the PAPI glideslope until half a mile out on final. The Board also cited the crew for their failure to use reverse thrust on the right engine, a decision that prolonged the landing roll and made directional control impossible.
In its report on a landing accident on January 1 this year involving a Bombardier Dash-8 at Ilulissat (BGJN) in Greenland, the Danish Accident Investigation Board (DAIB) focused on the crew’s failure to conduct a stabilized approach. While the Dash-8 was landing in a gusty nighttime crosswind that exceeded both the aircraft and the operator’s limitations, the left main gear collapsed and the aircraft skidded along the remainder of the runway and down a steep snow-covered slope to a point 35 feet below the runway elevation. One passenger and one crewmember among the 15 people on board received minor injuries, and the aircraft was destroyed. Investigators concluded that the crew failed to conduct a stabilized approach. The board said the crew reduced power to flight idle and then into the Beta range late in the approach, causing a hard landing that applied an excessive side load to the left main gear. Despite a nearly 90-degree crosswind gusting as high as 33 knots, the crew never attempted to execute a go-around. The investigation re-created the flight in an animation that showed the flightpath with a calculated Vref of 99 knots. At 1.5 miles from the end of the runway, the aircraft was still 30 knots above Vref and did not pass through the PAPI glideslope until half a mile out on final. The Board also cited the crew for their failure to use reverse thrust on the right engine, a decision that prolonged the landing roll and made directional control impossible.
Flight Idle results in a prop blade position safe for flight and still noticeable forward thrust, while in Ground Idle, even some mild reverse thrust may be delivered (DISC and slightly above).
On the other hand, discing produces negative thrust (drag) at TD and zero thrust at Zero IAS, approximately.
Like all reversing propellors, or jet/turbofan reversers, the effectiveness of reverse decays as a square function as the IAS decays. So, the message is: get on reverse early where stopping distance is critical, be it jet or turbo-prop.
This is the great advantage of the turbo-prop: with 'beta' control (incremental control of propeller blade angle with Power Levers) the pilot has a tool to precisely control thrust/drag during the flare, touch down and rollout. But he needs to understand the underlying principles!
Last edited by twochai; 25th Nov 2014 at 01:23.
