Landing an A320 with only one nosewheel
 

On January 17th a Thomas Cook A320 lost a nosewheel on take off from LGW.

Firstly would like to thank the AAIB for quickly exhonourating Thomas Cook engineering department. This incident was not caused by a maintenance error. It turned out to be a bearing failure that caused it to overheat on the take off roll. It got so hot that it actually welded itself to the wheel nut, sheared the locking devices and wound itself off the axle. the wheel is presently undergoing stripdown analysis at Hatfield as a follow up of the AAIB investigations.

As an engineer I would like to pose a question to any A320 pilots, with reference to the QRH under "Landing with abnormal gear config" It states that engines are to be shut down on flare. Why shut down the engines? When this aircraft landed in a text book landing, engines shut down, rat out, hydraulic pressure dropped. As the nosewheel only had one wheel, it castored round to 90deg to the runway as there was no longer any hyd pressure to keep it in line or even steer. The aircraft ended up nearly slewing off the runway. As such a great load was put onto the nose leg after this incident it was recommended by Airbus that the nose leg be changed. This was done and the aircraft was flying again after five days.

Well done to all involved!!!

Not questioning the airmanship of the crew (As in my opinion they did a great job) but why does the QRH say shut down the engines?

Look, one spelling mistake in a word is passable, but 2 goes beyond the limit- exonerate please!

I don't recall anyone criticising the Thos. Cook Engineering department- should you really use this as a means to bang the drum of your own department? Is it appropriate to thank the Authority for providing such exoneration? They are merely trying to find out why the incident occurred and need no thanks. Perhaps you'd like to run through a cast list (like at the end of movies) of all in the Thos. Cook Engineering department to come out and take a bow?

Shutting down an engine in the flare should have no effect on hydraulic pressure surely? The engine will still be rotating and still producing hydraulic pressure if it is a mechanical pump.

Sorry Rainboe, but I was looking for an answer from an Airbus pilot not an english teacher.

The reason we are all thankful to the AAIB for informing us of their findings so quickly, is that naturally we all asumed that it was caused by a maintenance error. The locknuts are not visible on a 320 nosewheel, they are under a plate. Could they have worked loose? Where they fitted correctly? Was it torqued correctly? Was it me? All these questions go through the head of any conciencious engineer that signs the CRS on any aircraft that is involved in an incident.

And to answer your question on hydraulics, no there wouldn't be enough pressure from the EDPs once the engines have been shut down. Neither would there be sufficient airspeed for the RAT to produce adequate hyd power, especially near the end of the landing roll.

i think the reasoning behind the qrh is so the engines are shut down if the gear gives way. I understand it was just one nose wheel but the qrh procedure is generic and sitting up front there is no way of knowing exactly what damage has occured to the leg, so best follow the qrh to the letter as it sounds like they did. From memory the rat is no good below 140 or 125 kts depending on the model.

winglit,

You have stated that the wheel is undergoing further analysis. Perhaps it would have been more prudent to delay posting until all the investigative reports have been completed. It is only then you should claim to be exonerated of all blame.

What if this final analysis discovers something untoward caused by an oversight of the T.C. engineering department? Why risk losing face when all that is required is a little patience?

I say this because there are so many potential causes of this bearing failure that fall under the maintenance umbrella, for example : wear, mechanical damage, corrosion, exceeding the manufacturer's recommended life, debris ingestion, insufficient lubrication (inadequate supply, incorrect type used) - to name just a few.

Of course, if you do get exonerated (and I sincerely hope that you do) then that would point to an inherent design problem with the bearing, which would need to be looked at with great urgency by Airbus.

Can you provide a link to the AAIB report, please?

Regards,

VC10 Rib22
:ok:

OK VC10, cool yer Conways! I'm not worried about losing face. Although it looks like I'm being misunderstood about my reasons for starting this thread. Maybe I shouldn't have mentioned the part about AAIB exonorating our engineering dept. But to say that it was a relief would be an understatement!

We did not make the wheel, nor did we overhaul it. But there have been problems with these bearings before. Usually they manifest themselves by producing a noticeable rumble through the airframe, not an instant catastrophic failure.

Unlike the VC10, the A320 does not have electric flying controls and maxaret brakes, so landing without hydraulics, I guess would not cause too much of a problem. But if you did end up scraping an engine on a VC10, then you are seriously in trouble!

I am looking for the reasoning behind the logic in shutting down both engines on the 320 with any abnormal gear config. I can understand that there may be a possibilty of gear collapsing, but how much difference would it make to safety if the engine was running or not? If you consider that by having the engines powered you also have full hydraulic power, you stand a lower risk of the gear collapsing as you have full pressure behind the hydraulic jack and this indication may only be caused by an unmade downlock that would engage on touchdown. You also have the added safety devices such as anti-skid and nosewheel steering to help with a tricky landing. Also if you had a confirmed gear not retracted, then wouldn't you want full flying controls to keep that wing up as long as possible? Without hyds you have no flying controls.

Hi winglit, I was an A-320 mechanic in a past life... why were the electric hydraulic pumps ( & the PTUs) not turned on so they would have hyd press??? Does the checklist not call for it? Turning on the electric hyd pumps + the PTUs just before engine shutdown would result in a smooth and quick pwr source transition.

LDG WITH ABNORMAL L/G checklist is intended for use with Nose or main gear not downlocked .
With loss of one nose wheel, confirmed by fly-by and three greens, would it not be possible to consider the possibility of a normal landing in respect of this checklist?
Admittedly there are other criteria but I think Winglit may have a point.

Winglit,


I can understand where your coming from on your initial post, and the thoughts you guys must have gone through!!

In my opinion the AAIB wouldn't have exonorated yourselves unless they were certain, meaning initial findings must have pointed towards a design flaw! If they weren't certain they wouldn't have said it - they would only end up contradicting themselves once the report was released.

Unfortunately 50% of the replies you get on here you have to let blow over your head, as that is all they are worth. I have probably started world war 111.

Well done to the crew involved, and well done for following the QRH, that is what it is there for!!

As this is a discussion forum I shall persevere. The LDG WITH ABNORMAL L/G drill is ' for use when nose or main landing gear fail to extend and/or lockdown following the application of L/G GRVTY EXTN procedure'
Other gear problems have different procedures. For example TIRE PRESSURE LO - crew awareness. ie. normal landing.
Presumably the requirement to shut down the engines is to avoid damage/fire when the gear is not locked down and therefore is sure to collapse and taxying or staying straight on the runway is not an option. The assumption that gear that is locked down ,albeit with one wheel ,will collapse may be a consideration but only that. If one tyre is flat the above procedure is not expected to be used. If one wheel is missing and there is no procedure then airmanship dictates, and indeed shutting down the engines , with the consideration that the a/c may depart the runway just because of that is an option.
By all means follow the QRH procedure- just be sure you have the appropriate one.

The exact same thing happened to me four years ago


except i was driving a ford fiesta on the M4
damned scary it was too........ :ooh:

Winglit,

As the AAIB have not yet made the details publc I can only imagine that your posting is either based on hearsay, reading my statement to the AAIB or information that I supplied to Airbus. If it's one of the latter two I would rather information that is meant for use within TCX stayed there.
I'm not *sure* who you are but I'm fairly confident that you were not there on the day. That being the case I don't really think it's your place to post comments on the incident. Questions - fine, comments - not.
To clarify what you've already said tho' - it was clear from soon after the aircraft landed that the wheel had been correctly fitted, nobody (& I don't mean me) has been nervously awaiting a call from the AAIB.

Winglit

It is still the airline that is responsible for whoever carries out the overhaul or tyre replacement on the wheel assembly, this includes the bearing inspection, clean and greasing.

backofthedrag is absolutely correct. All 3 u/c legs extended and locked down = normal landing gear configuration. Loss of a tyre is quite obviously something else and deliberately inducing total loss of nosewheel steering by shutting down all hydraulic power seems to me to be an unwise course of action...

I concur with Beagle, surely those who are interested in aviation and thinking through a problem would like to discuss a problem, those who think spelling is more important please feel free to disappear.
If this incident is not found in any POH...then surely the maintenace dept would have advised a procedure to follow. Incidenta like these are very important as case reference points and guidance.
Has this sort of incident been seen before? Is it an obvious resultant that the wheel would castor with or without hyd pressure. I am not so sure.

As far as the cause of the wheel departing the aircraft, I've seen this on the 737 twice (except on the main tire). The 737 and the 757 main wheel bearings are indistinguishable... at least to the naked eye that is. So both of these times a 757 bearing was installed on a 737 wheel assy at the tire shop and the wheel departed the aircraft on take off without the crew knowing anything about it, it was only after taxiing in at the gate that the mechanic noticed a main wheel is missing... one of these two times the mechanic was me. I've also seen aircraft taxiing into the gate with one deflated nose tire... in both of these examples the cause was "not following prodedures" at the tire shop as it is impossible for the mechanic installing the tire to see the problem unless he/she forgets to install an external bearing which has happened before.

Winglet...

Agree with some of the above that a missing wheel, but other NW remaining, does not count as "Ldg with Gear in Abnormal Config". Only my opinion (as an A320 Capt)... Usually in these cases time is not critical, and you will have time to consult Company Engineering, Flt Ops Mgmt and even Airbus, before Landing.

The "Eng/Hyd Off" is sensible for a potential nasty with missing legs - note the drill is for "Ldg with Gear in Abnormal Config", not "Ldg with Gear in potential Abnormal Config".

The aircraft is designed and certified to Land perfectly well with NWS not working, because it is assumed that there will be 2 balanced NWs, and an element of aerodynamic steering and differential braking (e.g. accumulator etc.) remaining. The missing wheel scenario does not fit in here, and maybe had never previously been considered?

The incident here was somewhat "out of the box", and lessons to be learned - that is what the AAIB is there for! No implication of criticism of the crew of anybody at the time - strange "emergency", and lessons for all. Interesting time for NW "problems" with the KLM 737 at BCN as well....

NoD

I'm a little confused with this one. Was the APU not running? I'd have thought engines shut down, APU running, electric hydraulics pumps + PTU?
Another point mentioned was that this scenario might not have been considered when writing the QRH - I vaguely remember that the using the park brake as an emergency brake wasn't considered until an accident happened (can't remember the airline).
Differential braking should be more than enough to steer the aircraft even with the nose wheel scrubbing, how easy that is though is another point all together.....

With the engines shut down the yellow and green hydraulic systems will depressurise. The green system does not have an electric pump and the yellow electric pump will not operate unless selected on, which is not included in the checklist. The yellow elec pump is also useful in the dual engine failure case if the APU can be started, but again is not in the QRH. Maybe someone with a few more brain cells than me could explain why?

So do the Airbus engines not windmill for a period after being shutdown, and still supply hydraulic pressure for the time of the rollout if shutdown in the flare?
If I am going to end up scraping along on an engine, I would rather there was not any fuel running into it!