Luxair emergency at Sarrebruck
 

Luxembourg press reporting Luxair Bombardier Q400 emergency undercarriage up landing at Sarrebruck Ensheim airport this morning. Reported as experiencing sudden heavy smoke (not clear where) leading pilots to decide on emergency return and landing. No injuries reported.

Saarbruecken is the correkt spelling, or EDDR

jacdec.de

Just depends which language you're using. Pleased that all on board are OK.

For photographs go here RTL.lu - Lëtzebuerg - Luxair-Maschinn brécht Start of a kënnt um Bauch un d'Halen

Aviation Safety Network reporting that there was smoke in the cabin immediately after take-off and wheel retraction. A/c landed back on the runway wheels-up.

Seems that retraction was pretty smart for that to have happened, or am I misreading it? (disclaimer, very occasional SLF here)

ASN Aircraft accident de Havilland Canada DHC-8-402Q Dash 8 LX-LGH Saarbrücken-Ensheim Airport (SCN)

Here's an odd case where being gear up may have helped the outcome.

If the gear had still been down when they rejected, being well past V1, if the gear holds then it's probably a high speed overrun. If the gear folds up from the hard landing then it might puncture full wing tanks or cause some spinning or cartwheel action from digging into the ground.

The gear generally are raised smartly after lift-off, to 1) reduce drag and improve climb as soon as they are no longer needed, and 2) get the gear and doors stowed before the dynamic pressure of the airspeed gets too high. It puts more and more strain on things "hanging out," and the actuators that move them, as speed increases.

Without getting into the minutiae of specific aircraft, equipment, operator and pilot SOPs - the pilot not flying (therefore monitoring) has his eyes on the altimeter and vertical speed gauge and calls "Positive rate (of climb)" as soon as the needles indicate such, followed immediately by the call (and action) "Gear UP!"

Has anybody considered the posibility that the gear was retrackted to early and that the aircraft just setteled down on the runway? Not familier with the type, but could it be that the gear handle was in the up position on the ground by mistake and that as soon as WOW occured the gear retrackted and the tail hit followed by the rest of the aircraft?

We have seen the above scenario on the F-16 where the flaps are retrackted automaticly with the gear, and if this is done to early ie. just after rotation, the reduced lift will cause the aircraft to sink back on the runway.

While the scenario You offer would be technically possible, there would have to have been a lot of previous SOP breeches and much negligence for it to occur.

First of all, during the cockpit preparation, among many others the correct positioning of the gear lever and the serviceability of the light bulbs is verified.

Secondly, it is very hard to overlook the gear lever if it is selected UP on the ground, as the wheel-shaped knob on the lever would be lit up (TRANSIT indication, showing that the landing gear is not in the position selected by the lever). To assume that both pilots willingly accepted such an indication and not only taxi, but also take off with this would stretch my imagination a lot.

Also, on the DH8, the flaps are selected separately from the gear and under no circumstance will retract automatically. A too early gear retraction might possibly cause a tailstrike, but (without having tried this!) I would assume that the aircraft is sufficiently powered to climb out of such a situation - even more so with only 16 pax on board and a probably light fuel load.

Tu.114 I know you also have some Q4 time under your belt, I couldn't help but wonder on a 2000m runway, even with 16 passengers on board, I don't think you would be able to take off, climb to a normal sort of height to retract gear and then reverse the aircraft and land.

Which leads me to suspect either the gear was retracted early, or was being retracted as the decision to land was made.

Happy conclusion in that no one died, but lots to come from this I think!

Yes, I too think that the report on this accident will be an interesting read when it comes out.

Pitch after liftoff increases rather quickly. During gear retraction, I would expect to see about 10°; with a light DH8-400, a pitch of 15 to nearly 20° is not uncommon then during initial climb. This means that the runway gets invisible below the nose structure rather soon. Were one to lower the nose again and pull the power levers back with the possible intention to land, there might well follow some surprise about how little runway is still left out of the 2000m.

I do not know but would be interested to learn the following: How will the PSEU (Proximity Switch Electronics Unit, governing and sequencing the gear retraction and extension among many other things) react to a "GEAR DOWN" selection while it still is busy retracting said landing gear?

Either it will simply reverse the process and reextend the gear starting from where it happened to be interrupted in the retraction, or it will complete the retraction and follow with an extension from the fully retracted position - or, the nastiest possibility, it will lock up and produce a "LG INOP" caution light, seeing that the gear is in a not clearly defined position while it still is in movement (a similar PSEU fault has once caused me the need for an alternate gear extension). Is anybody able to shed some light on this?

Dont have any detailed system knowledge to add I am afraid but looking at some of the pictures there is something that looks like an open nosegear door visible?

Burst tire?
 

Hello,

Media report now citing passengers who claim tire burst just before lift-off with aircraft "veering out of control and impacting runway" and pilots then regaining control and putting aircraft down with gear retracted. Aircraft apparently came to a halt 300m beyond end of runway on a paved area of the airport. As with all passenger eyewithness report, not sure how credible.

Report (in German) here: Tageblatt Online - Alle raus! - Nachrichten

Sorry but some things do not make sense to me...

There is mention of smoke from the rear part of the galley just after liftoff, but it would have taken at least 10 seconds for that evaluation to reach the cockpit, then why when airborne decide to dive and crash the aircraft gear up with no guarantee of remaining in the airport/runway perimeter while a traffic pattern on a turboprop will maybe take max. 4 minutes to complete if the situation is immediately so dire...?!

I see no damage hinting of a massive fire at the back?...

Despegue, this is the elephant in the room indeed.

There are two smoke detector circuits on the DH8D that report directly to the flight deck: one in the forward and one in the rear cargo hold. The smoke detector in the toilet (located behind the F/Os side of the flight deck and directly in front of the forward cargo hold) will not trigger an alert in the flight deck as such, but its siren intended to call the flight attendants can certainly be heard in the cockpit as well.

Smoke in the cabin or the galley on the other hand is supposed to be detected and acted upon by the flight attendants.

Smoke in the lavatory or the cabin would typically be reported to the flight deck via an emergency call - but answering this will typically be lower on the priority list than establishing the aircraft in a climb, retracting the gear and so on.

A cargo smoke warning will trigger the master warning, a triple chime, the red "Check fire detect" warning light (mid-left on the lowest line of the CWP) and several lights on the upper right part of the overhead panel (in a slightly "sunk" section to the right of the T handles). The extinguishing agent will normally be released automatically in two steps; only correct operation of the system will need to be checked. This has definitely been trained in the simulator and should not cause a well-proven crew to shoot from the hip either.

Another possibility, of course, is smoke in the flight deck coming from whatever source. Air conditioning has been known to be a provider sometimes, but more often at low than at high power settings (with the HP taps open instead of the LP ones). But then again, training would have suggested putting on the masks and smoke goggles and entering one of the checklists offered for this situation.

I for one do not know and dare not suggest what may have happened here - the investigation will soon show.

Emerald Airways (HS748 Turbo Prop - 30 Mar 98) did something similar.

https://assets.digital.cabinet-offic...001_G-OJEM.pdf

I agree the elephant in the room will be exactly what prompted the decision to abort.

The decision must have been virtually simultaneously with the movement of the gear lever to UP (absent the scenario F16guy mentions) - to produce the visible damage to the aircraft on the ground. Nose gear doors open and crushed, main gear fully retracted and doors closed.

Ground contact must have occurred within a second or so of this moment in the gear retraction sequence:

http://airlinersgallery.smugmug.com/...%2846%29-M.jpg

...a very narrow window, where the long main gear have reached a point higher than the aircraft belly, but the nose gear and doors are still exposed. The undamaged main gear then completed the retraction cycle as the aircraft slid along the pavement.

Pattern_is_full - this sounds plausible.

http://www.aerotelegraph.com/wp-cont...n_luxair_2.jpg

Looking at the propellers, it seems that the #1 side has hit the ground: the blade tips appear missing at least on the blade that is visible. With the propellers running clockwise (when observed from behind), chances are that debris did not impact the cabin but got thrown away to the sides. #2 seems to be intact, but the blade angle seems to be a fair bit lower than the start/feather position displayed after a normal shutdown; this might hint at a quick shutdown via the T-handles.

Just a thought, I'm not familiar with Bombardier, but on some other aircraft an emergency call from the cabin will trigger the master caution. Unrelated to this incident, generally speaking, I think that's a good idea, it provides a hint that it's not a good practice to give priority to retracting the gear rather than answering an emergency call.

On the DH8-400, the emergency call will only trigger a chime and a yellow flashing light on the rear part of the radio control unit located at the rear end of the center console (IIRC, the -300 had no chime but the light in a more prominent position in the forward center part of the center console). One has to look at the panel to see the nature of the call.

I would be of the opinion though that flying the aircraft comes first: there are very few instances in which postponing the gear retraction, which takes mere seconds and brings the aircraft in a state covered by performance calculations, in order to take a call from the cabin is justified. If required, a relanding via a traffic pattern is usually a matter of a few minutes and initiating this maneuver 3 or 4 seconds later, but with a cleaned-up aircraft, will do more good than allowing one to get kicked out of the flow and possibly forgetting the landing gear retraction over the information received.

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?

The Luxembourgish press (not the most professional or objective IMHO :rolleyes:) 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! :D

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?

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.

From AvHerald:

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.

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

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.

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...

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

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.

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.

Between 2009 and 2011, on factory-new aircraft.

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.

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 :
Are the last 2 sentences technically correct ?

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.

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.

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.

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.

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 ?

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.

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

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

What on earth is going on at Luxair??