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View Full Version : A330 Land Rcvy. Why LGCIU?


Microburst2002
11th Sep 2014, 12:21
Why does the LAND RECOVERY gives us the LGCIU 1 if we still have to lower the gear by gravity and we won't be able to retract the L/G in case of a go around?

AQIS Boigu
11th Sep 2014, 14:21
not an Airbus expert...

the LGCIU 1 comes online so you get the green triangles to confirm the gear is down and locked...(either on the SD page or the greens next to the gear lever

Microburst2002
11th Sep 2014, 16:33
It is better than nothing…

But why can't we have, for the same price, the ability of the computer to control the landing gear extension and, more importantly, the gear retraction? The problem is electric supply, not hydraulic or mechanical. If the LGCIU is supplied, why not?

Perhaps only a part of the LGCIU is powered?

Sidestick_n_Rudder
12th Sep 2014, 21:21
But why can't we have, for the same price, the ability of the computer to control the landing gear extension and, more importantly, the gear retraction? The problem is electric supply, not hydraulic or mechanical. If the LGCIU is supplied, why not?

I'm not flying the 330, but I guess that in Emer Elec Config you may, or may not have the HYD Engine pumps running. In the latter case (ie. both engines out), if powered by RAT only, I doubt it would have enough power to move the L/G...

A360
12th Sep 2014, 23:09
I did not fly the A340 for a while (similar to A330) but the reason could be the closure of the safety valve due to the loss of airspeed signal (loss of ADRs)

NovemberRain
13th Sep 2014, 00:28
First of all, as you know, the main purpose of the Land Recovery is powering the SFCC (Slat Flap Control Computer). It also energizes LGCIU because we and several systems need to know the landing gear in down and locked position. LGCIU provides information to tons of systems including nav, air cond, fuel, hyd system, etc, even toilet system :rolleyes: as an example, simply the GPWS gets that information to prevent a TOO LOW GEAR warning.

mutley320
14th Sep 2014, 01:28
I imagine its to give air/ground logic to the various systems.... Especially spoilers. Even if both LGCIUs fail , you have " Independent downlock logic " to the "green lights " on the panel above the lever...

Anytime the EMER Gen is selected , it Latches on as power source to ESS busses til maintainence action.
Emer gen , powered by the Green system, be it Eng driven pumps or the Rat...
Landing Gear , biggest user on Green system.... Manual extension to prevent a "shock" to the Green system and possible interruption to Elec power generation.

Microburst2002
15th Sep 2014, 05:42
I always learn a lot in PPRune

Mutley that makes sense, the need of the air-ground logic being the main reason for recovering the LGCIU. Also the need to preserve the green hydraulic for its EMER GEN powering role. Although it should be at least possible to retract it. In the Y+B hydraulic failure we have to extend the gear by gravity to preserve the only hydraulic remaining, but it is possible to retract it if you wish. Isn't it possible at all to retract it if need be?

my conclusions so far:

need for knowing if the gravity extension is successful (3 green)
air-ground logic for whatever systems still available that need it
green hydraulic system "preservation"

vilas
15th Sep 2014, 09:07
Microburst2002
An explanation from Airbus presentation on dual engine flame out with RAT powering the Green system says With recovery of engine1, green and blue systems are recovered the ECAM continues to show landing gear gravity extension to cover both cases of engines recovered and not recovered because gravity extension has minor consequences like nose wheel steering loss. LGCIU1 stops nuisance warning from GPWS. It recommends to follow the ECAM but technically it appears you could lower the gear normally. I am not a 330 guy but happened to see the presentation because it explained the difference with A 320 system.

Microburst2002
15th Sep 2014, 11:31
Interesting. In the EMER ELEC case (no dual flame out, just bus bars fault or whatever) I can't see in the INOPs if the L/G RETRACT is there or not, because it is "simplified". In the sys remaining it does not mention the retracting function, only the LGCIU 1 status (and that of the gravity system). So I guess the only way to know is to rule out the possibility of gear retraction due to the lack of some equipment, or by doing an experiment in the sim.

What I am more concerned with is with retracting the gear after a go around. In the case you are forced to divert, that is about 3 times the fuel required, which in most cases will mean you are in a fuel emergency.

vilas
15th Sep 2014, 12:19
Microburst2002
According to A330 FCOM in EMER ELEC with no generators recovered there is the following
Note: In case of a go-around, gear retraction is not available, and CLIMB performance is degraded.
In any case with red land ASAP why would you be diverting after a GA. You won't select a marginal weather or airfield in the first place.

Microburst2002
16th Sep 2014, 12:06
Because sh1t happens… :uhoh:

That note is in the FCOM PRO ABN?

vilas
16th Sep 2014, 14:02
Yes. I copied from FCOM. When this electrical problem occurred and you selected a diversionary air field and made approach. Now you want to do another diversion. Even if you were landing at destination normally and execute a GA, the gear doesn't go up if you have to divert would you have fuel?

Microburst2002
19th Sep 2014, 16:46
The worst case would be arriving to destination with just enough fuel with one failure only and then something else becomes u/s and then you see yourself in the ELEC EMER.
You do the drill quickly and after L/G down the runway lights or something don't work and you cannot land there anymore. You have minimum diversion fuel, but now you need three times as much to reach an alternate and three times as much to stay in the air for 30 min.
It is very likely that you don't even have fuel for 30 min, so you are instantaneously in a fuel emergency.
In that situation I would probably choose to retract than to starve and crash land somewhere. Even ditching is not a good choice, with L/G down.