Sign in to follow this  
Guest ib345

fuel pumps problems

Recommended Posts

helloi have some problemsif the engines are running and i turn off all the fuel pumps, the engines should stop, is this correct? in my case this not happenI thought that i had the option of fs2004 (ilimited fuel on), but this was not the problemin the other side, with APU running, if i put the fuel pumps off, the apu should stop (is this correct?? and they don

Share this post


Link to post
Help AVSIM continue to serve you!
Please donate today!

My understanding is that both the engines and APU will draw fuel via suction in the event that the fuel pumps are inoperative.So the behaviour you are experiencing seems normal.Peter

Share this post


Link to post

But i think that this behaviour is not very logic, because, in this way, why does the plane need the fuel pumps?that happen also to you?

Share this post


Link to post

It may not be logical to you , but it appears to be representative of the real aircraft. See this link http://www.smartcockpit.com/pdf/plane/boei...7/systems/0019/I am no expert but I asume that the engines work most efficiently when fuel is provided at a given pressure; pumps also allow for X-feed and tank balancing.If the pumps fail....? That is when you are happy for the backup system.Peter

Share this post


Link to post

thank you very muchanother thing that i have seen is that when i have the plane completely configurated for fly, if I turn off the HID pumps (the ELEC and ENG ones) i can move all the surfaces of the plane(flaps, spoilers, alerons, trim...)is this normal?

Share this post


Link to post

Yes that is normal too. There is mechanical linkage from the control column to the control surfaces.

Share this post


Link to post

I thought surfaces wouldn't move unless 4 was on Auxiliary?Rob

Share this post


Link to post

I think hes talkig about the 737. I fly the 737-800 for a living. The engine its self has two fuel pumps separate from the ones in the tanks. The switches are for the ones in the tanks. The engine pumps both increase the fuel pressure and send it to the Hydromechanical Metering Unit which then sends the required fuel to the engine. Any fuel above what is needed gets sent back into the system. There is a suction feed line for each engine in its corresponding tank that bypasses the pump incase the pump fails. Due to decreased air pressure at high altitude there may not be enough pressure to get fuel to the engine.As for the APU we used run them all the time with no fuel pump on. Now they want us to have a pump on when running it because they say the suction feed was putting stress on the parts.

Share this post


Link to post

Ms/Mr Nameless,Please sign all your posts with your real name. It's always nice to know to whom you are speaking.1. You have in-tank fuel pumps and engine fuel pumps. Engine fuel pumps are pressure pumps driven by the engines. In-tank fuel pump are feed pumps for the engines/engine pumps and are driven electrically and operated from the overhead.2. At high altitude if your in-tank fuel pumps stop your engines *might* stop. This is not modelled on the PMDG NG however IIRC.3. With hydraulics INOP you can still move the control surfaces. The INOP hydraulics will make the servos INOP for the controls as well but you are still on cables so moving the controls are still possible but will need quite some extra force. As explained above. This extra force is not simulated for obvious reasons on the PMDG NG.Hope it helps,

Share this post


Link to post

but with all the HYD pumps off i can extend and desextenf flapsWhy?

Share this post


Link to post

That, my unknown friend, will be answered when you sign your posts. ;-)Happy new year,

Share this post


Link to post

sorry, you are right, i gorgot to sign my postMiguel Velazquez

Share this post


Link to post

Here is a summary, Miguel...Although modern jet engines have to be able to run in all flight regimes without the assistance of tank fuel pumps, the tank pumps are there for safety (as engines have been known to flame out or not get full thrust without the use of tank pumps). Also, you can't suck fuel out of the centre tank (no suction feed system is available). 737 Stabiliser Trim uses a DC electric motor rather than the hydraulics found on larger jets.Trailing Edge Flaps can use electric power also, but only if you select Alternate Flaps. Are you sure all sources of hydraulic power have been removed? Note that windmilling engines can provide enough hydraulics for all systems if the aircraft airspeed is fast enough.There is manual reversion for ailerons and elevators, but lots of muscle power is required.Spoilers and Leading Edge Slats will only work if you have hydraulics.Please note: I believe you can't get independent leading edge and trailing edge movement in MSFS, so you may find that sim programmers have to make compromises/simplifications in flap modelling.Hope this helps.Cheers.Q> Ян

Share this post


Link to post

When you select the Alternate Flaps switch to arm a trailing edge bypass valve locks out hydraulics to the flaps. Electric motors the drive the trailing edge flaps as previously mentioned. It will also energize the standby hydraulic system to move the leading edge flaps and slats. They will only go to full extend not the partial extend normally get with flaps 1, 2, and 5. In the real world aircraft the leading edge devices can not be retracted by the standby system. One thing Microsoft Flight Simulator can not simulate is how hard it is to move the flight controls in flight with no hydraulics. I have never done it in the real plane but we have done it in the simulator. Using the cables only is very very difficult.

Share this post


Link to post

thank you very much with your explanationis the neumatic system need for the engines just for the start?if, when the engines running in ground i put off the apu bleed air and both engines bleed air switches, the engines are runningthis means, that the neumatic system is use only for the start of the engines? and of course trhe presurization?

Share this post


Link to post

"this means, that the neumatic system is use only for the start of the engines? and of course trhe presurization?"I think you just answered your own question... Without the pneumatic system switched on, the passengers would die :(Pneumatics are also used for:AirconditioningEngine inlet cowl anti-icingWing leading edge anti-icingPassenger drinking water tank pressurisationHydraulic reservoir pressurizationTAT probe operation on the ground (in some cases)Cargo Heating...and a few other things I probably haven't thought ofI repeat.. you DON'T need to switch off engine bleed for engine start. Just the airconditioning packs.Cheers.Q> イアン

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this