Luxair emergency at Sarrebruck

[Joe_K]

Different media report now claiming no burst tire and no fire on board, smoke only after the gear-up landing. Unusual sounds mentioned.

(RTL.lu - Lëtzebuerg - Kee geplatzte Pneu, kee Feier, enorme Materialschued in Luxembourgish)

Which then (as others mention) begs the question: why would an experienced flight crew decide to abort take-off after gear-up when they were only 50nm from their home airport which they were due to fly to (SCN being an intermediary stop on a HAM->SCN->LUX route), in a plane they had just previously flown from HAM to SCN and which was on the ground for maybe half an hour to unload PAX?

[Tank2Engine]

The Luxembourgish press (not the most professional or objective IMHO ) says that the investigation is now focusing on the landing gear, as apparently there were some issues a few years ago on the Dash 8: Luxemburger Wort - Ermittlungen konzentrieren sich auf Fahrwerk

In the mean while, another Luxembourgish newspaper already came to the conclusion that the crew did everything correct: L'essentiel Online - «Der Pilot hat richtig gehandelt» - Nachrichten Great, so we don't need to wait for the conclusion of the investigation!

A very strange accident indeed, especially judging from the limited and conflicting information. As Joe_K mentioned it's somehow it's very difficult to believe that an experienced crew, after V1 and immediately after lift-off and gear retraction, would cut the power and crashland an aircraft gear up on the remaining runway for a 'simple' smoke warning. I wonder if they even got airborne at all, or if the gear collapsed/retracted upon rotation perhaps due to some technical issue?

[Joe_K]

Conclusions

Hello,

Luxembourg media have now published the conclusions of Luxair's internal investigation following a press conference:

Luxemburger Wort - Co-Pilotin der Luxair für Bauchlandung verantwortlich

RTL.lu - Lëtzebuerg - Saarbrécken-Tëschefall wéint mënschlechem Feeler

Apparently it was human error, gear was retracted too early.

[Tu.114]

From AvHerald:

On Nov 17th 2015 the airline reported in a press conference, that the first officer had retracted the landing gear too early before the captain aborted takeoff causing the aircraft to settle on its belly without landing gear. The captain as well as cabin crew acted well in the course of the occurrence, the first officer however was suspended.

This begs the question: How does this happen? The gear should be protected against inadvertent retraction as long as there is weight on wheels - which is typically the case before V1 (and also a varying time above that speed). Also, to retract the gear on the DH8, one will first need to unlatch the gear lever via a thumb-operated little knob before moving it to the "Up" position, so it is rather hard to move it unintentionally. And finally, there is a huge difference in sound and also in the general setting surrounding it between the callout "Stop" (or whatever LG may use to initiate a takeoff abort) and "Positive", which triggers the next order "Gear Up".

The FDR transcript will likely be highly interesting.

[Joe_K]

Well, at least one of the articles seems to imply that the first officer retracted the gear because she happened to be thinking about retracting the gear, sort of "automatically", without being asked by the PF to retract the gear. And goes on to describe it as a "known psychological phenomenon".

They then claim the early gear retraction lead to "the tail hitting the runway", which caused the PF to abort. I'm reading elsewhere the Q400 only has Weight-on-Wheels sensor on the nose gear, is that true?

Edited:
Another article claims the gear retracted 3 seconds before the aircraft would have achieved VR.
http://www.tageblatt.lu/nachrichten/...h-ein-22371399

[Tu.114]

No, the Weight on Wheel sensors are definitely on the Main landing gear as well. There are two sensors per leg dedicated to this task; the failure of one, or a very tail-heavy condition during loading with e. g. the rear cargo hold filled to the limit and nothing else on board (extending the NLG shock strut too far), will trigger the "WT ON WHEELS" caution light in the flight deck. This requires maintenance attention before the next flight and is not releasable under MEL.

So I am still surprised that the WOW sensors allowed a gear retraction at such a premature stage.

[F-16GUY]

As soon as the main gear starts to extend the oleos, I suspect that the WOW circuit is opened and that allows the gear to start the retraction cycle. If this the lift from the wing is not enough to get the aircraft of the runway, it will settle back tail first. Seen it before...

[ATC Watcher]

I have heard aerodynamics (e.g. relative air entering the open gear wells ) played a role in keeping aircraft from accelarating/lifting off.

[safelife]

Knowing the landing gear of the Q400 it isn't really surprising that the gear did retract.
During two years on the Q I've seen green lownlock lights with the gear firmly up, landing gear doors opening and closing by turning the tiller, even wheels driven through closed gear doors.
The logic controlling the gear must be a weird piece of kit.

[Tu.114]

Safelife, did that happen to be during the first years of this types operation, i. e. around 2000? I am under the impression that such weird things have become rather uncommon since then.

[safelife]

Between 2009 and 2011, on factory-new aircraft.

[Clandestino]

Originally Posted by ATC Watcher

I have heard aerodynamics (e.g. relative air entering the open gear wells ) played a role in keeping aircraft from accelarating/lifting off.

Small chance. "Triumph of raw power over aerodynamics" is an old cliché, yet it fits Q400 well.

Incıdentally, I had a terrific opportunity for observing repetitive attempts at uncommanded gear extension on pretty new mighty Q, somewhere 'round 2010. Spontaneous retraction would be new for me but if BFU, in 5-7 years, comes to conclusion that it happened here, I won't be surprised a little bit although my money is currently on missed item in preliminary cockpit preparation + bump on the runway.

[ATC Watcher]

Clandestino, the BFU rep said final report will be published in 2016 .

I do not know the Q400 , but Luxemburg a bit, very small aviation community there .
BTW, for those that do not understand Luxemburgish, here is a rough translation of what Ney ( CEO Luxair ) said during the press conference :

The lady FO has inadvertently retracted the landing gear too early, so that the aircraft tail struck the runway. She did so, as the take-off was reached. At that moment only the nose wheel had lifted , the main landing gear was still in contact with the runway. The co-pilot had, with the actuation of the lever, disactivated the mechanism that prevent retraction of the gear on the ground. Everything was functionning properly, according to Luxair, as tests proved after the incident.

Are the last 2 sentences technically correct ?

[Universe]

Gear lever and logic design

The Dash 8 gear lever is designed only with an uplock release switch, preventing inadvertend gear selection in case of accidentaly bumping against the lever.

Pilots have to unlock this switch at EVERY gear selection making it an automatic manoeuvre, thus eliminating that safety net. The word is out that although the Dash has weight on wheel switches on all gear, only the nose wheel weight on wheel switch is part of the gear extension/retraction logic.

[Clandestino]

Clandestino, the BFU rep said final report will be published in 2016 .

I am very relieved to hear that. Last time Luxair's ERJ left a nosewheel on Saarbrücken's runway before departing for MUC, it took BFU 9 years to admıt they have no clue why the offending axle fractured.

Are the last 2 sentences technically correct ?

İf the first one were correct and merely setting the gear lever up disables retraction protections, then TC and DHC would be in big trouble - not that the later was exactly known for high quality of the landing gear used on their mightiest. Second one is probably correct - "tested on ground, found OK" was the most common response in TLBs I was obliged to read.

The word is out that although the Dash has weight on wheel switches on all gear, only the nose wheel weight on wheel switch is part of the gear extension/retraction logic.

Though I can't verify it, as I only flew 'em and didn't fix 'em, I won't be surprised at all if it indeed turns out to be so.

[ATC Watcher]

Thanks Clandestino, another question if I may : when retracting the gear, does this open some gear wells doors , or are all remaining open all the time on the ground ?

[Clandestino]

All three gear bays feature doors that open (well, hopefully open) only when gear is in transition, though their climb gradient reducing effect on the over-powered collection of spare parts flying in close formation, otherwise known as Q400, is quite negligible. Especially on short leg with 12 pax.

If the final analysis confirms that the cartoon provided by Luxair ıs correct, gear was selected up before rotation and retraction sequence began as soon as weight was off the nose gear. Aeroplane never achieved lift-off attitude (or more precisely: alpha) and just settled on the fuselage.

To say the accident is very interesting is probably an understatement.

[hampshireandy]

Any connection with any of the collapsing gear SAS incidents on the crash 8 a few years ago?

[Joe_K]

Looks like it's not a good year for Luxair, another Q400, LX-LGE lost part of it's engine cowling en route to LCY today.
(second link has a picture)

Luxemburger Wort - Luxair plane immobilised after panel breaks off

Un avion de Luxair perd des pièces de capot au décollage

[twochai]

What on earth is going on at Luxair??