B737 Classics. Raising gear after A System failure
 

Question arose during hydraulic systems discussion. Engine failure on lift off with severe damage to A system hydraulics and loss of fluid to that system. According to the book you now cannot raise the gear which in turn seriously degrades climb performance.

However with one engine inoperative is it possible to raise the gear via the PTU operation under these circumstances?

No, because the PTU uses Sys A(!) pressure (which you have lost) and feeds the autoslats and leading edge flaps. Plus, it only operates when Sys B pump pressure drops below limits (+ airborne + flaps >up<15).

But you can still raise the gear via the LTV (landig gear transfer valve), which operates automatically when airborne + eng.1 RPM below limits + landing gear lever up + either main gear not up & locked. This valve allows Sys B to supply the amount of fluid to raise the gear.

happy landings

Ok, Dollys reply was for the newer models.

For the 737-200, the answer would be easily "no". Landing gear is powered by System A, and there is no way to transfer fluid from the other ones (Sys B and STBY).

PP

Dolly,

Don't think your answer is correct. Don't have access to the books at the minute but I seem to remember that the Landing Gear Transfer unit operates by using SYSTEM B FLUID FLOW to pressurise SYSTEM A FLUID. In other words it caters for a loss of flow rate of system A fluid due to loss of A system engine-driven pump following an engine failure on takeoff. However, if there has been a major leak in system A then there may be no fluid left for the LGTU to pressurise - if no A fluid, gear cannot be retracted.

I stand to be corrected...

I’m talking -300/400:

The LGTU includes a shuttle valve that opens under the mentioned conditions to port Sys B pressurized fluid via the unit to the landing gear “retraction mechanism”. So, fluid actually transfers. During each gear raising attempt about 0.8gal Sys B fluid will be lost (dumped into a reservoir as the gear up valve repositions).

If there is a rupture from the LGTU towards the landing gear, then you will be unable to retract the gear.

***Click here for a shematic.***

happy landings

I heard a keen type checkie once came up with the scenerio:-

* Loss of Sys A pressure NOT associated with engine failure
* Unable to land at departure airport
* Not enough fuel to fly gear-down to alternate
How do you get the gear up?

Answer- EITHER shut down NO.1, or else pull the breaker on the no.1 N2 gauge to fool the LTU into thinking you had an engine failure....

I think he needed to get out more...

... yup - up they go ...
 

:ok:

For the 300/400, dolly737's on the money and I got a thumbs up from an engineer.

Mr Boeing says:

"....or else pull the breaker on the no.1 N2 gauge"

Let's hope doing this doesn't have the same effect as pulling engine indication CB's on DC10's... I seem to recall an engine separating from a wing as a result of an indication breaker being pulled and reset in flight :rolleyes:

Rgds.
Q.

Thank you all very much for the info. It is really appreciated.

Try P6-2 D2 and D4.

N2 Tach Indicator.

Yes it is,

Boeing built about 2000 of them,

So there are around 4000 N2 circuit breakers out there...

Hey, Wizofoz, you forgot the 30 737-100 and more than 1100 737-200!:}

Not quite as I remember it, but...


"11/3/1973 National Airlines
DC10-10 Albuquerque, New Mexico Overspeeding of the starboard engine caused the engine to disintegrate. Pieces struck the fuselage, breaking a window, causing rapid explosive decompression and a passenger was sucked out of the plane. The plane landed safely. Out of boredom, the captain and flight engineer decided to experiment and see what would happen to the autothrottle system if the circuit breakers which supplied power to the instruments which measured the rotational speed of each engine's low pressure compressor were tripped. This led to engine overspeeding and destruction of the engine. "

Is anyone out there advocating the pulling of tacho indicator circuit breakers to get out of trouble? :eek:

Cheers.
Q.

ASFKAP - at home at the moment, so don't have the cb chart to hand, but I'm pretty sure the 400 EIS has them somewhere around P6-2, behind F/O's right ear.

Please let me stress that while the situation I presented might be of academic interest, it was presented as the machinations of an over zealous check captains diseased mind.

I AM NOT and WOULD NEVER advocate deliberatley pulling CBs unless it was spelled out in a manufacturers approved checklist (See gear not down and locked in B737 EFIS non normal c/list).

No, pulling N2 C/Bs wouldn't cause results al la the DC 10. That doesn't make it a good idea!!

"There are some CBs for the various sections of the EIS primary display".

Sorry, ASFKAP - I was being economical with my reply! Exactly as you say, and like you I also assume that you cannot affect the signal to the change-over module just by killing the display. I think engine shut-down would be the only option as per 'wizofoz'.

Yes and No
 

OK, ASKFAP, if the question is if these acft have N2 CB´s, the answer is yes and no.
No, the 737-100 and -200 doesn´t have a CB to interrupt N2 indication. But yes, they do have a N2 CB - related to illumination (located on P6 panel):p
This is pretty straight forward, as N2 (and N1) on this kind of acft are only tacho generators (remember that we still have the information in case of a battery start).
From Boeing maintenance manual, we can extract the following paragraph (AMM section 77 - Engine Indications, 77-12-0, page 2):
"The engine tachometer system operates on self-generated electrical power. The airplanes electrical power is required only for the integral lighting of the tachometer indicators".
I hope this clarifies a little bit more!:ok:

PP

.. getting into VERY dangerous waters here, people.

The only way to know what a CB or fuse protects is to go back to the WDM or similar design document.

If the operational documentation provided to the crew does not specify the operational use of protection in abnormal or emergency situations, then the breakers ought not to be played with AT ALL .... in the great majority of cases, the pilot will have no real knowledge of what is hanging off the other end of the breaker and what consequential screwups might follow on from ill-considered tripping of breakers. What one learns in a pilot endorsement school about the mysteries under the trim covers usually is a very, very sanitised and simplified version of reality ...

Perhaps one of our electrical engineering design members might like to wade into the fray and emphasise the dangers to be encountered if one plays about with electricity ......

ASFKAP,

As I explained, my original post was meant as an amusing aside and I did not mean to start a bun fight. As to whether pulling the N2 c/b would fool the LTU, with 4000 hours on the things (both E-I-S and S-T-E-A-M D-R-I-V-E-N), my answer is B******* If I Know, but I believe my alluded too check captain used to run this scenerio in a sim, so if it is the truth either the sims fidelity was at fault, or pulling the N2 breaker DID affect the LTU (Or the whole thing was made up by an even MORE diseased mind!!).

Your first reply that
Just aint so. Non EIS, EFIS aircfraft have them. If my retort was a little curt, no offense was meant, but I did think you shot from the hip a bit. Just what inputs opening that circuit cause are for more able minds than mine to debate.

In any case, shutting down No1 WOULD bribg the LTU on line, Just for Christ sake don`t say I told you to do IT!!! :eek: :eek: :eek: ;)

Just a small PS, I made no mention of 1 or 200 series Aircraft. I`ve never even sat in one.

ASKFAP,

Take it easy. We never meant to discuss, just to talk!:)
I completely agree with our moderator Jonh (hey, things became a little bit hot on this cabin!) and Wizofoz when they say that we never advocated to pull ANY cb (unless specifically adressed by the QRH)!
Let's assume this was just another question from an exam. When you said
you were a little bit wrong (see, just a little, I don't wanna fight :ok: )
We do have a CB for the lighting of the instrument. I already scanned it, but I'm so idiot that I wasn't able to include it in this reply:{ I could e-mail it for you, if you want.
Sorry if in any message I said anything you didn't like.
Still friends?

PP

PS - by the way, I'd very pleased if you all give any opinion regarding my message "Flight Deck Forums » Tech Log » Concorde: why not two different V1´s?"
Thanks in advance!!!