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-   -   A320 fuel/tank feed at engine start (https://www.pprune.org/tech-log/640793-a320-fuel-tank-feed-engine-start.html)

iaveight 1st Jun 2021 00:07

A320 fuel/tank feed at engine start
 
I have heard many differing opinions so I am looking to Europe to answer the question. At engine start, where is fuel
supplied from? The Centre tank or the wing tank? After both engines are started I believe the centre tanks feed the engines until slat extension. My question is specifically upon the first engine start.

thanks

Check Airman 1st Jun 2021 00:12

Apologies if the answer to my question is obvious, but where are you getting these "opinions", and why do you need to revert to an opinion?

iaveight 1st Jun 2021 00:25

So in other words you do not know yet piped up for some unknown reason.

Check Airman 1st Jun 2021 01:30

I can't stop you from taking that point of view if you're so determined.

oicur12.again 1st Jun 2021 01:51

This has me intrigued.

I have been flying the bus for a very long time and always thought the wing tanks fed the engines during start. I am certain that FCOM said something similar to “the CTR tank pumps run for two minutes AFTER engine start”.

BUT

I have just started reading through my newly issued company manuals on the IPAD and they have all been ….”customized” since I last flew in 2020 and are no longer simply copies of FCOM.

And reading the fuel system it clearly states:

“If fuel is in the CTR tank, the pumps run AT engine start for 2 minutes”

followed by

“They will also run before OR after the engine start sequence if the slats are retracted”.

So this implies the CTR tank is providing fuel during start?

Its no big deal, knowing this doesn’t impact the operation but it certainly goes to show that not all is what you think it is!

Dorf 1st Jun 2021 02:02

Anybody that would name themself "Check Airman" must be quite impressive! My goodness!

porterpat 1st Jun 2021 02:31

A lot of people on this site are just so bitchy.
How about if you have nothing that enhances knowledge just keep quiet.
Anyone noticed the reduction in posts over the last few years, I'm not the only one who thinks this way.

320busboy 1st Jun 2021 06:05

For the 20 the wing tanks have sequence valves. Basically blow off valves. The ctr pumps run for the start until 2 mins or slats extend as per the fcom. The higher pressure from the ctr pumps wins the pressure fight and you get ctr fuel. The flscu will off the pumps as described and will restart them at slat retraction until one of the ctr low level sensors is dry then I think its 2 or 5 mins for scavenge then they shut off. If my memory serves me well. Hope that helps some.

vilas 1st Jun 2021 08:04

It depends on MSN numbers. New aircraft do not have centre tank pumps they don't feed engines directly but empty into respective inner tanks.

Uplinker 1st Jun 2021 08:25

Unless the cross-feed is open, each engine will only take fuel from its respective wing tank.

The fuel is fed from the centre tank and ACT tanks into the wing tanks, and is used in the sequence ACT 2, ACT 1, Centre tank, Wing tanks.

I can't find the specific text in the FCOM any more but my understanding was that around engine start the CTR pumps will run, (assuming fuel in the CTR tank), but when the Slats are out this will stop. The CTR tank pumps run presumably to allow any problems to reveal themselves on the ground that might render the CTR tank fuel unavailable for the flight. Fuel transfer is stopped during take-off and approach to prevent a tank contamination problem affecting all engines.

Edit, my post crossed with vilas

8314 1st Jun 2021 09:25


Originally Posted by Uplinker (Post 11055103)
Unless the cross-feed is open, each engine will only take fuel from its respective wing tank.

You must have the joy of flying a rather modern fleet in deed.

320busboy 1st Jun 2021 11:58

guessing it’s the Neo’s. All of our v25 20s have ctr pumps. 21 have the jet pumps.

iaveight 2nd Jun 2021 16:45

Thanks all!

pineteam 3rd Jun 2021 09:22

Not only the Neos. We have A320 V25 with jet pumps too.

8314 6th Jun 2021 16:16

Busboy has it, except for one little nitpick: ctr pumps run 2min after engine start regardless of slat position for self test.

So all whites out —> all pumps run, but wings have pressure relief sequence, so ctr wins and supplies fuel for engine start and until 2min after. Then they turn off with slats (earliest 2min after eng start) , so t/o is on wing tanks.

FlightDetent 6th Jun 2021 18:53

8314, I thought the same and even typed it: lights off and all run. Then deleted it, thinking the centre's are energized but may not actually run. With the normal refuelling sequence the outers are full and thus the centre pumps would be crossline green. Same logic could apply for jetpipes/transfer valves.

Care to check the books for the two of us?

8314 6th Jun 2021 20:37

Logic 1 says ctr pumps stop with slats and at least 2min since engine start
Logic 2 says ctr pumps stop with full inner tanks until 500kg are used to prevent spillage from the IDG return. ( xfer valves (jet pump a/c) clsd until 250kg gone)
Fuel return valve only opens above a certain oil temp threshold (73C?) but seems to have no connection with pump logic, so on ground with fuel in ctr tank wings should always be full, so ctr pumps always crossline green? Do they run at engine start for self test?
Getting more confuddled the longer I look at it. 🤔

FlightDetent 7th Jun 2021 00:27

My hunch is with Logic 2 you brought the answer. The general rule of self-test could still apply it seems, only achieved through a more complex logic and not just a timer.

Funny story: I once flew for an operator whose CAA thought the tank segregation for take-off was of high importance. Hence we had an SOP to time after engine start for 2 minutes, in order to observe the limitation and avoid departing with them running.

vilas 7th Jun 2021 05:12

But you won't be opening TO thrust before two minutes from engine start anyway.

Denti 7th Jun 2021 08:19

Well, you shouldn't. But of course it is possible at some airports ;)

And if one uses single engine taxi out, then it is a real timing issue anyway.


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