Landing gear transfer unit 737NG

[LOC1GSarmed]

I was wondering if loosing hydraulic system A fluid will hamper LGTU ability to work?

[latetonite]

The LGTU will not kick in, unless engine #1 has less than 50% N1.
On the ground you can make it work by switching the Alt Nose wheel steering to ALT.

[de facto]

If you lose sys A after takeoff,the gear wont retract.
As latetonite wrote you 'need' nr1 engine to fail for the LGTU to operate.
The LGTU is for the gear to be retracted within 8 secs and the 2nd climb gradient not be delayed as engine 1 is operating sys A engine driven pump.
Both engines running and gear down wouldnt be an initial climb gradient issue.

The switching to ALT NWS on the ground would indeed activate the LGTU but i fail to see any operational reason unless you dispatch with the left engine out,an idea for Kramer i reckon:p

[latetonite]

Maybe for steering back to the stand?

[de facto]

I hadnt even started my flight yet and u wanna taxi back?:p

[latetonite]

Would not be the first time. A good captain always has a few "no go's" in his pocket..

[de facto]

Quite agree.

[Kefuddle]

I was wondering if loosing hydraulic system A fluid will hamper LGTU ability to work?
Pulling the N1 run pwr CB will fool the system into thinking engine 1 has failed and the LGTU will operate.

Generally speaking troubleshooting is troublefinding and in this case if you try this with a leak in Sys A keep the manual reversion page handy too :D

[Fullblast]

Maybe not a big point in the discussion but as far as I remember N2 is the master signal, not N1.

Generally speaking troubleshooting is troublefinding and in this case if you try this with a leak in Sys A keep the manual reversion page handy too

Correct, unless you are 100% sure the leak is upstream of the landing gear lines, wouldn't do that anyway.

[Kefuddle]

Yup, N2, quite right Fullblast.

[latetonite]

Ok, it is N2. Typo.

Back to a real life situation, you will not have trouble if the engine does NOT fail, as you can easely climb with the gear down. L

Loosing nr 1 engine, yes, LGTU will work with an empty system A reservoir, as long as the gear is hanging down.
Return fluid will however go to system one after gear retraction, and be dumped to the same place the fluid from system A went.

Do not know how many go arounds you can make, as the fluid tranfer/loss is quite substantial. Probably depends where the leak is.

Chance this scenario to happen however is next to none.

Double failures nowadays are prohibited in the sim.:O

[Kefuddle]

Lateronite,
Back to a real life situation, you will not have trouble if the engine does NOT fail, as you can easely climb with the gear down.
Agreed, not being able to raise the gear is mainly a fuel burn issue - going back is undesirable and continuing may or may not be possible. Options?

[latetonite]

Kefuddle:

You answered your question yourself in post #8.

Pull circuit breaker labeled 'RUN/PWR' behind Captains seat, middle panel, second row, third from the left, and raise the gear.
Then continue to your new, nice weather destination, with good overnight facilities.
Then let the F/O fly. He needs the practice when manual reversion becomes necessary.
Before hitting the bar, fill in a CVR and ASR.

Where is the problem?

[Kefuddle]

Errm, no problem mate. Just continuing the discussion. In summary, you can raise the gear with loss of system A assuming no leak. It isn't advised. The probability is remote, but if it does happen in difficult circumstances, armed with this knowledge, such troubleshooting is an option for consideration.

N'est ce pas?

[latetonite]

Oui m'sieur.

[Fullblast]

Assuming no leak...
So, engines working but system A u/s...why...pump problem? You have 2 of them...both u/s...quite unlikely...no fluid..so you have a leak. The point is, as I already said, where is the leak, but how do you know? And even if you know...are you sure 100%???

Then..if you really can't land back and not enough fuel for the closer alternate is can be an option...but even an emergency landing below minima back to the departure airport can be an option...but if you are over the ocean, well, don't see any particular problem doing a ditching in manual reversion:E

[flyboyike]

Just eject.

[de facto]

So dont take off with less than 5 T if your dep airport vis is less than the landing minima...(b737 NG).

[Gas Bags]

The transfer valve will operate automatically with these conditions present:

1. One main landing gear not up.
2. Landing gear lever not down.
3. Engine 1 N2 less than 50%.
4. System B pressure available at the valve.
5. Aircraft in the air.

The valve exists to allow system B EDP to supply retract pressure to the landing gear when system A EDP is offline (Engine 1 N2 less than 50%). The EMDP (System A in this case) flow rate is too low to get the gear up in a satisfactory time during a single engine climb out after takeoff, with the obvious drag issues created.

To the OP: System A quantity has no bearing on the valve operation.

[BARKINGMAD]

Interesting point but do you have any regulation/prohibition/recommendation etc from any xAA on this principle?

There are some TRE/TRIs out there who need to be educated if this is a fact.

Especially for the unfortunate command trainees who are currently being tortured and sometimes destroyed by some very imaginative scenarios dreamt up by their "trainers" to see how long they can hold out before cracking, this could be a breath of fresh air indeed?! :confused:

[latetonite]

Barkingmad:

You can always start a new tread.
Being in the trainer business for some years, I can tell you that most of the times we are working on a standard syllabus, issued by the company.
The checking part is covering the same principles.
TRE are supposed to check objective issues, not subjective decisions.