LGCIU 1+2 Failure on A320 Question

[b767300]

Here is the scenario.
LGCIU 1+2 Failure.
ON STATUS page the inoperative items will be:-
AP1+2
A/THR.
REV 1+2 (Will operate actually )....we tried it in the simulator.

The Question is:-

How can you make sure that the landing gear is actually down & locked without the LGCIU.

1- The landing gear indicator panel is signaled by LGCIU 1 if electrically powered, which in this case it is not !!!.

2- The red arrow on the panel which comes at 750 RA is also from LGCIUs.

So what is the guarantee of the landing gear is really down locked?

Can you ASSUME it is down knowing the system of Gravity Gear Extension?

Any ideas ????

[Oom Kaspaas]

Wait for dreamland. He knows everything

[westinghouse]

fly past the tower........ and hope it during day time.

[electricdeathjet]

oh yeah I am sure they can tell all three gears are locked when passing at 150mph 400 m in front of them! :ok:

[lurkio]

Simplest way is to land, you will have to sooner or later. If the world takes on a strange attitude one (or more) wasn't down and locked.
Sorry for the simplistic attitude but even with the Airbus I still think that simplest is best.

[yoland]

If you need full power to taxi to the stand after landing then you will know.:O

[LandASAP]

Good Day,

some of the LDG Proximity sensors are hardwired to the Lights which gives you an indication even if both LGCIUs fail but not if LGCIU#1 is completly blown away because nevertheless these signals are going through the BOX (LGCIU#1). That's how it is on the A330. I actualy don't know if the A320 has the same architecture but i think so.

[Leave 5 on the glide]

FCOM Vol 3 says that LDG gear lights on LDG gear control panel will remain only if LGCIU 1 is electrically-supplied. So I guess that if LGCIU 1 is not electrically-supplied, you have no lights.

Also as a side point, the GPWS has to go OFF if LGCIU 1 is affected because it recieves gear UP info even if the gear is DOWN.

[b767300]

Also as a side point, the GPWS has to go OFF if LGCIU 1 is affected because it recieves gear UP info even if the gear is DOWN.


This is what the FCOM 3 & ECAM will tell you to do.
BUT
As a trial in the simulator, the GPWS was intensionally left ON.
the following were noticed:-

1- The red arrow at 750 on the landing gear control panel did NOT appear.
2- but at 500 feet A.G.L. the warning TOO LOW GEAR was correct.

they tried it with both cases (one approach with LDG gear not downlocked and another approach with LDG gear downloacked).

[Boroda]

And both cases they had at 500 TOO LOW GEAR?

[aulglarse]

You also have the WHEEL page to cross-check for gear down indications.

[Lemurian]

1- The landing gear indicator panel is signaled by LGCIU 1 if electrically powered, which in this case it is not !!!.
Then it's a bad day for you. The requirement for the green panel indications is for the LGCIU 1 to be electrically powered. It can be faulty, it doesn't matter as the prox switch signals run through it to the panel indications.It just needs to be powered.
So, if LGCIU 1 is not powered, you're screwed, no gear position available either on the WHEEL ECAM page or on the indicator : you'll have to perform a LDG with abnormal L/G procedure.
Can you ASSUME it is down knowing the system of Gravity Gear Extension?
Check that the crank is fully against the mechanical stop and still - just in case - go through the abnormal L/G procedure. Don't forget to promise St Francis you'll burn a candle for him !

[Che Guevara]

I have tried the same failure in a 320 and a 330 sim. The 320 does not give you the red arrow, however the 330 does...don't know if it is the 330 sim or whether they are in fact wired differently. If anybody knows for sure please let us know....

[b767300]

And both cases they had at 500 TOO LOW GEAR?

No, when the landing gear was not downlocked the warning appeared.
when the LDG GEAR was downlocked the warning did not appear.
So the plan should be contine to 500 AGL and see, if this warning is triggere then Go Around and consider abnormal LDG procedure otherwise continue normal landing.

So, if LGCIU 1 is not powered, you're screwed, no gear position available either on the WHEEL ECAM page or on the indicator : you'll have to perform a LDG with abnormal L/G procedure.


But which one you should consider?:sad:
THREE cases are there.... which gear you should consider?

I have tried the same failure in a 320 and a 330 sim. The 320 does not give you the red arrow, however the 330 does...don't know if it is the 330 sim or whether they are in fact wired differently. If anybody knows for sure please let us know....

The A330 is different, it wired differently, this is I know becasue we tried it in the simulator earlier, few year ago.

[Builtinredundancy]

Hi Guys,

Having just experienced this in the sim there was much discussion about indications and actions.
If in doubt, there's no doubt! Full emergency landing. After reading the manuals again, I too come up with the same information with regard to LGCIU 1 powered situation with indications available. Dual failure, no indications.
Coming at the same problem from a slightly different direction. The landing gear has spring loaded geometric (over center) locks attached to each of them. In the event of "Gravity Extension", the main gear SHOULD free fall, with the nose gear aerodynamically assisted into position and then all down locked by the geo locks.
Point raised in discussion;

Did you hear the usual uplock release clonk?

Does the aircraft require more thrust to fly?

Has the level changed in the green hydraulic system display?

I believe LGCIU1 circuit breaker is monitored but I am unsure of LGCIU2. A dual failure in isolation seem highly unlikely. Furthermore, this failure coupled with an uplock release failure or geometric downlock failure is so unlikely at to make it so improbable that it could ALMOST be disregards.

In response to the previous comments, a flyby could work as the diagonal braces are quite clearly visible. If these are in position it is quite safe to assume the geometric locks have done their jobs. However, It would have to be daylight, it would require a low flyby and I would suggest a technically competent person such as an engineer confirms the gear position.

If anybody out there has a definitive answer, it would be much appreciated.

Ps red gear arrow SEEMS to take its signal from output 14 of the LGCIU1 so now power, no signal. i standby to be corrected.

[Microburst2002]

When an LGCIU declares itself faulty it does't mean it is unpowered. It only means its outputs are disregarded by users. But the gear down locked output from LGCIU 1 is hardwired to the panel indicator and as long as the LGCIU has electrical power it will provide the down locked indication. Not so in the ECAM WHEEL page.

If you have a double LGCIU failure and on top of that the LGCIU 1 happens to be unpowered, then there is no landing gear position indication. There is no way to be certain. Gravity extension should work normally. The down lock springs should help to extend the lock stay to overcenter. But of course something abnormal could happen and you wouldn't know.

So in that case you should use your airmanship, take into account fuel and time and all circumstances before making any decision. With fuel and visibility you can make a low pass and have someone take a look, or even (why not) request air force airplanes to inspect it from below. Or you can study the abnormal landing gear procedure and think of a contingency procedure should things con bad after touch down

[Citation2]

Does anyone know why a dual LGCIU Fault does not lead to direct law ?

FCOM DSC-27-20-20 P 1/8 " Flight Controls Law Reconfiguration" lists failures that would reconfigure the flight controls to Alternate/ Direct law and it states that LGCIU disagree would lead to direct law BUT having a look at LGCIU Disagree procedure on FCOM, nothing is mentioned about direct law either.

[Magnetic Iron]

Citation II no, but interesting question.
Why would a LGCIU fault lead to direct law ?

I understand that only a LGCIU disagreement would in conf 2.

How would a disagreement in LGCIU´s data cause Direct Law ?

[vilas]

Citation2
LGCIU disagreement alone does not cause direct law. It is double RA failure that causes it, normally when gear down or one step earlier in conf2 with LGCIU disagree since gear down indication is not avaiable.

[TurnOne]

Hi
Had this in the sim last week. No gear indications. When rereading the Fcom it seems as Airbus has confidence in their gravity extension. Bit uncomfortable not seeing the green triangles but with the gear noise and higher thrust in level flight, all indicating gear down.Otherwise we are talking of multiple system failures.
Doing a flypast at home base with proper tech's viewing gear down and good ATC not a bad idea but flying mostly at dodgy controlled airports where English is not first language in my opinion will add to the risk. No A/P, F/D and A/thr also increases the work load.
As precaution notify the emergency services and brief the cabin crew.

In short, if you used the L/G gravity extension take it as the gear is down and locked

[clark y]

B767300,
With respect to your comment about the Reversers working in the simulator, I've had LGCIU 1 fail in flight in an A320. The status page stated that reverser one was inop, yet it actually worked when we landed.

[Valmont]

I had this failure a couple months back when we selected the gear down at about 1800ft RA.
Now the ECAM was showing LGCIU 1+2 fault but it seems that not all parts of the LGCIUs were inop as the nr2 was showing the gear down on the wheel SD page, and the landing gear pos indicator was showing gear down too (Connected to the LGCIU 1 backup part).
After touchdown, both reversers worked just fine (status was showing reversers inop) and the landing gear doors retracted.