Jazz Q400 Right main landing gear collapse YEG

[pelmet]

What was the final word on the SAS gear collapses. Did it turn out to be the fault of the manufacturer or the airline?

[Big Pistons Forever]

What was the final word on the SAS gear collapses. Did it turn out to be the fault of the manufacturer or the airline?

The causal factor was ineffective maintenance procedures with respect to processes used to lubricate components of the MLG. Part of the problem was maintenance instructions that were, in retrospect, too ambiguous.

[whiteguy]

What was the final word on the SAS gear collapses. Did it turn out to be the fault of the manufacturer or the airline?

The causal factor was ineffective maintenance procedures with respect to processes used to lubricate components of the MLG. Part of the problem was maintenance instructions that were, in retrospect, too ambiguous.

Yup, SAS was so unhappy with this shoddy built aircraft that, after the landing failures, they went and ordered a dozen more Qs!

[-TSRA]

Yup, SAS was so unhappy with this shoddy built aircraft that, after the landing failures, they went and ordered a dozen more Qs!

...wha?

[Finn47]

What was the final word on the SAS gear collapses. Did it turn out to be the fault of the manufacturer or the airline?

The causal factor was ineffective maintenance procedures with respect to processes used to lubricate components of the MLG. Part of the problem was maintenance instructions that were, in retrospect, too ambiguous.

Yup, SAS was so unhappy with this shoddy built aircraft that, after the landing failures, they went and ordered a dozen more Qs!

However, SAS got rid of them all, eventually, and now have zero Dash 8`s of any model in their fleet. They sold the 27 older Q400´s to Philippine Airlines and Malev. The 14 or so new ones were not operated by SAS but by a subsidiary (Wideroe) instead and never flew in full SAS colours. Finally, SAS sold Wideroe to private investors last year.

[pile_it]

That propeller thing is insane...

Are there many accidents/incidents where props went through the fuselage? I can't find many recently.

I guess bombardier are not done with this story.

In 2011, a Wasaya BE02 had a prop blade depart the hub and breach the fuselage in Kasabonnika, ON.

[CFM Symphony]

It also happened to a Brasilia in the US in 1995.

For this particular case it seems the blade entered right through the window, which is very unlucky. I wonder how the strengthening plate would have been able to withstand the impact had it hit there first.

[PilotDAR]

As I have read that the nature of the tire damage was "a piece missing", is it possible that when it spun up upon touchdown, that it shook the gear leg so much that the downlock was shaken undone, and the "leg lock" arrangement unlocked to allow the collapse?

[Lost in Saigon]

As I have read that the nature of the tire damage was "a piece missing", is it possible that when it spun up upon touchdown, that it shook the gear leg so much that the downlock was shaken undone, and the "leg lock" arrangement unlocked to allow the collapse?

I thought the same thing when I read this news report:


http://www.theglobeandmail.com/news/nat ... e21516648/

When the right landing gear deployed, Ms. Kurylo saw that the tire was “shredded and flapping.”

Ms. Menard said the landing initially seemed normal and passengers hadn’t been told to brace into a crash position.

Then the plane suddenly started rattling as they went down the runway. The right landing gear collapsed and the plane started tilting to the right. Ms. Menard felt as if she was in a car about to roll over.

[linecrew]

After seeing what a Metro prop did to the side of the fuselage after a gear up landing in Ottawa back in the 90s I always make sure that I don't get a seat near the prop line when booking a flight on a turboprop aircraft. On a much lesser point, it's also quieter in the back of the Dash-8 anyway.

[plhought]

...Seems to have been an issue with the Dash 8 dating back pretty much to day one:...

One should note that a significant number of those early serial number Dash-8's had much-much smaller ice-shields installed. Although their primary purpose is to prevent damage from flying ice to the fuse, they do help better protect the cabin from flying spinny bits.


I think we're getting a little side-tracked here - the propeller will always be a hazard. It's still disheartening that something like a blown tire could result in a collapsed gear. Even a violently shaking gear leg should have no problem keeping that H-Frame secure with over-centering, and spring-force.

[Canoehead]

should have no problem keeping that H-Frame secure with over-centering, and spring-force.

Over-center lock and hydraulic pressure.

[plhought]

Over-center lock and hydraulic pressure.

Sorry...and hydraulic pressure! :p

Seems like a heck of cheese holes lined up here mechanically to allow this thing to fail.

[Maynard]

Post irrelevant, thanks Canoe.

[Canoehead]

The Dash 8 100/200/300 also has composite blades.

[Oxi]

[CD]

Final report published:

Aviation Investigation Report A14W0177

Right main landing gear collapse
Jazz Aviation LP (dba Air Canada Express)
DHC-8-402, C-GGBF
Edmonton International Airport
Edmonton, Alberta
06 November 2014

Summary

The Jazz Aviation LP (doing business as Air Canada Express) Bombardier DHC-8-402, registration C-GGBF, serial number 4433, operating as flight JZA8481, departed from Calgary International Airport (CYYC) with an intended destination of Grande Prairie, Alberta. During the takeoff roll, the number 3 tire of the main landing gear failed. The flight was diverted to Edmonton International Airport (CYEG); aircraft rescue and firefighting equipment was standing by for the landing on Runway 02. On touchdown at 2030 Mountain Standard Time, the right main landing gear collapsed. Upon contact with the ground, all of the right-side propeller blades were sheared, and 1 blade penetrated the cabin wall. The aircraft came to a stop off the right (east) edge of the runway surface. Passengers and crew evacuated using all 4 exits. Three passengers sustained minor injuries. There was no post-accident fire. The accident occurred during the hours of darkness.

Findings as to causes and contributing factors

The number 3 tire ruptured on takeoff, most likely as a result of impact with a hard object.
During landing, the failed number 3 tire was spun by contact with the ground and was maintained at a rotational speed that was the same as or very close to one of the natural frequencies of the main landing gear. This caused the lock links to trigger the proximity sensor electronic unit to de-energize the solenoid sequence valve, thereby relieving system pressure from the extend port of the unlock actuator.
The excessive vibration caused the lock links to overcome the force from the downlock springs and unlock the stabilizer brace as a result of gear dynamics, which led to collapse of the right main landing gear.

Findings as to risk

If there are no specific requirements for dynamic vibration testing of components or completed airframes, there is a risk that similar or other aircraft systems could fail during high-vibration conditions.

Other findings

Short-radius turns with hard braking may cause an extreme shearing force on the tread area and on the sidewalls of the number 3 tire in particular, because it is the pivot point.

[YYCAME]

Well I for one am a bit disappointed in the results. To blame resonant frequencies feels like a bit of a shot in the dark. Unless they actually induced the frequencies on a landing gear and were able to observe a link lock/prox sensor failure in which case I would expect some sort of vibration dampening mod to be coming out as an AD. To claim that these vibrations were then induced by an unbalanced wheel spin also feels rather vague. This requires that the brakes were not being used or defective on that wheel, that the damaged hub was maintaining a very specific harmonic rather then decelerating with the aircraft or failing to decelerate due to normal friction in free rotation if no longer contacting the ground.

Did Transport really write this or were they just fed it by Bombardier? Anyone who has flown in a Q400 with the NVS deactivated would know that there are tons of vibrations going from the props, engines, wheel imbalance etc but somehow a wheel briefly spinning up on contract and then slowing down did all this?

[Canoehead]

Did Transport really write this or were they just fed it by Bombardier?

TSB wrote it. Nothing to do with Transport.

[YYCAME]

Your right TSB, though I think I assumed they were connected somehow. I'm not really clear on where the two overlap if at all.

It just seems much more plausible that a PSEU uncommanded signal to depressurize that actuator occurred because of an electrical design flaw where a signal failure defaulted to the wrong position. Though it is a bit disconcerting that the mechanical lock itself was not able to do its job, because hydraulic pressure loss is a normal part of life. Edit: Though maybe the actuator has been depressurizing for various reasons for a long time and the mechanical lock has been faithfully doing its job of covering up the problem.