PPRuNe Forums

PPRuNe Forums (https://www.pprune.org/)
-   Tech Log (https://www.pprune.org/tech-log-15/)
-   -   What is the reason for turning off fuel pumps after shutdown.(a320) (https://www.pprune.org/tech-log/606202-what-reason-turning-off-fuel-pumps-after-shutdown-a320.html)

FlywithPark 6th Mar 2018 03:57

What is the reason for turning off fuel pumps after shutdown.(a320)
 
It is not easy to find the specific reason for turning off fuel pumps after shutdown for a320.
Could anybody explain this for me?
Thank you.

pineteam 6th Mar 2018 05:04

Since you don’t need them why keeping them on? The wings pumps run all of time unless you switch them off.
Also during refueling, if fuel pumps are on there is a chance of fuel spilage. Can’t find any references for this but it happened quite recently in our fleet.

vilas 6th Mar 2018 05:12

31st Jan I quoted the following from airbus.

Regarding the operation of fuel pumps in standard/normal conditions, we would like to confirm that Airbus recommendation is to switch OFF all fuel pumps at the end of the flight, and to turn them back ON during the cockpit preparation.
The references in the Airbus operational documentation are the following ones:

- At the end of the flight, Airbus SOP (Refer to FCOM-PRO-NOR-SOP-22 P 2/4) requests the flight crew to set FUEL PUMPS to OFF

- During the cockpit preparation, Airbus SOP (Refer to FCOM-PRO-NOR-SOP-06 P 3/20) states “It is a general rule to turn off all white lights during the scan sequence; therefore, these actions are not listed here”, namely to turn OFF all white lights for all the related systems.

The reason for this policy is to avoid operation of fuel pumps in an empty fuel tank, and also avoid unwanted fuel transfers (which can affect and potentially abort refueling process). That is the reason why the recommendation to switch OFF the fuel pumps before refueling is not explicitly provided into the FCOM, because this recommendation is implicitly covers by SOPs in standard operations (i.e. when refueling is performed before the cockpit preparation).
Please be informed that there are no restrictions/limitations to have fuel pumps running during the refueling as long as they do not run dry (in an empty tank, which in any cases should never be more than 10 minutes).

However, the general recommendation (not mandatory) is to have the fuel pumps switched OFF during refueling, in order to ensure that the possibility of pump dry running is avoided. It is particularly relevant for the center tank pumps, because the center tank is most of the time empty at the end of the flight. Switching OFF the center tank pumps ensures in all cases that they do not run during refuelling.

When performing the cockpit preparation, it is assumed that the refuelling (if needed) has been performed previously. As a result, if Airbus SOPs are well applied, all the fuel pumps will be correctly switched OFF during refueling.

vapilot2004 6th Mar 2018 09:04

A longer discussion was just recently had here.

tdracer 6th Mar 2018 16:19

Airbus doesn't close the spar valve when you set the fuel switch to CUTOFF, just the engine fuel valve (note that this is different than Boeing - Boeing closes both the engine valve and the spar valve when you select CUTOFF).
As a result, if there is a bad seal on the engine cutoff fuel valve, the pressure from the boost pumps can cause fuel to leak past the valve and into the combustion chamber. That can cause a major tailpipe fire on the subsequent start.

Goldenrivett 6th Mar 2018 17:08

Hi tdracer,

Airbus doesn't close the spar valve when you set the fuel switch to CUTOFF,
Airbus calls the spar valve "LP fuel shut off valve"
FCOM DSC-70-40: Shut-Off Valves
"Moving the ENG1 (ENG2) MASTER switch to OFF directly commands the closing of the LP and HP fuel shut off valves for that engine's fuel system.
It also closes the fuel return valve and opens the bypass valve."

FlightDetent 6th Mar 2018 19:38

@vilas Thanks again. You seem to have raised all of the questions with Airbus, that all of us mere mortals have. How you managed, I can only speculate that vilas is at least the second reincarnation as a TRI/E.:E

BTW: do you not think it's unfair of AIB not to adjust the FCOM accordingly? I read the explanation with a bit of sadness.

The airline that trained me the best went to great lengths to wipe off the habit of leaving the pumps OFF, citing the no-white-lights rule. Now, 7 years later on the internet I read that it does not apply to Fuel Pumps before refuelling ends? Yuck. And maybe that the AMM even specifies so!

Their logic that SOP are well applied because during CKPT PREP the re-fuelling is finished is utter rubbish. That was NEVER true at any turn-around, since A320 day 1.

tdracer 6th Mar 2018 20:39


Originally Posted by Goldenrivett (Post 10074907)
Hi tdracer,


Airbus calls the spar valve "LP fuel shut off valve"
FCOM DSC-70-40: Shut-Off Valves
"Moving the ENG1 (ENG2) MASTER switch to OFF directly commands the closing of the LP and HP fuel shut off valves for that engine's fuel system.
It also closes the fuel return valve and opens the bypass valve."

Apparently Airbus finally wised up and made a change to close the "LP valve" because it didn't use to be that way (A300, A310, at least some early A320).
Not that Boeing didn't do the same thing - early 747s didn't close the spar valve either - after a number of hot starts/tailpipe fires they changed to shut down both valves.

vilas 7th Mar 2018 00:56

FD

do you not think it's unfair of AIB not to adjust the FCOM accordingly?
I somewhat tend to agree with you there. But I think all manufacturers play close to their chest. It may the fear of law suites. They tell what you need to operate the machine. But they will answer the customer query. So ask them under Tech Request. But then some airlines control who will ask. As for no white light during cockpit prep it could be difference in perception. Perhaps airbus wanted that way. It doesn't take long anyway.

MD83FO 7th Jun 2020 12:20

Dear Vilas, I cannot find in the literature where it states that we must wait for refueling complete to begin the cockpit preparation. Thank you.

vilas 8th Jun 2020 07:52


Originally Posted by MD83FO (Post 10804739)
Dear Vilas, I cannot find in the literature where it states that we must wait for refueling complete to begin the cockpit preparation. Thank you.

My post #3 is a personal reply from Airbus.

AerocatS2A 9th Jun 2020 07:30


Originally Posted by vilas (Post 10805427)
My post #3 is a personal reply from Airbus.

In other words, it's not in the literature.

Uplinker 9th Jun 2020 08:58


.....That is the reason why the recommendation to switch OFF the fuel pumps before refueling is not explicitly provided into the FCOM, because this recommendation is implicitly covers by SOPs in standard operations (i.e. when refueling is performed before the cockpit preparation)......
my bold.

Airbus SOPs are part of "the literature" surely?

Switching off fuel pumps on the ground while they could be running dry, seems to be a reasonable precaution to me. Heat and fuel vapour can be an explosive combination !


AerocatS2A 9th Jun 2020 10:01

Well refuelling isn't usually performed before cockpit preparation where I work, and I can't see where it says it should be, not that that means it's not there of course. If it is important then the SOP should tie the pumps into the completion of fuelling.

Check Airman 9th Jun 2020 14:11

At my company, if we waited for fuel to start our setup, we’d push late every time lol

jettison valve 9th Jun 2020 21:42

Dear tdracer,
As was pointed out already, on A330/A340s (I think A380 is the same) the ENG master switch closes also the LP valve on the front spar. Unless... it´s assembled wrongly, as a hidden failure.
This lesson was learned when during a maintenance activity (for whatever reason!) an engine was to be shut down using just the ENG Fire P/B (which interestingly only moves the LP valve, but does not trigger the HMU or anything else in ATA 73). The engine kept on running for many minutes, when the engineers finally killed the engine with the ENG master switch.
Side facts: The incident took place on an A340 whose "operator" at that time was, well, a big aircraft manufacturer in Seattle. Secondly, we replicated the same scenario (eng shutdown via fire P/B) on a different airplane, and it took more than 60sec before the EGT started decreasing after P/B activation; I still wonder why it takes so long...
(Official documentation: https://ad.easa.europa.eu/ad/F-2003-360R1 - On reading the AD more than 15 years later, I am still amazed about the long compliance times set by the DGAC - for such a simple task, 12.000FH / 39 months (we pushed this through much quicker)).

Now, and the real reason to start typing: A big thank you for all your comments and insights! I really appreciate your contributions. No political nonsense or guesses, but always solid technical statements, presented understandibly, even for a maintenance person.

Thank you very much!
J. V.



Denti 10th Jun 2020 07:21


Originally Posted by AerocatS2A (Post 10806480)
Well refuelling isn't usually performed before cockpit preparation where I work, and I can't see where it says it should be, not that that means it's not there of course. If it is important then the SOP should tie the pumps into the completion of fuelling.

Really?

With a 25 minute turnaround, the fueller connects as soon as the doors are opened, and the flightdeck crew will start with the cockpit preparation as soon as they have finished the post-flight flows.

AerocatS2A 10th Jun 2020 08:13


Originally Posted by Denti (Post 10807334)
Really?

With a 25 minute turnaround, the fueller connects as soon as the doors are opened, and the flightdeck crew will start with the cockpit preparation as soon as they have finished the post-flight flows.

Yes? And once the cockpit preparation is finished the fueller is still hooked up. Look, sometimes they've finished but sometimes they haven't, there is nothing in our SOPs that ensures the fuelling has finished before the PF does the overhead panel.

Jwscud 10th Jun 2020 08:29

There is nothing in our SOPs either.

There is howver plenty of “wise man’s guidance” from our training dept. My lot have a number of EIS1 old MSNs in the 1xxx range and I was strongly advised not to switch the pumps on until:
(a) refuelling was complete and
(b) the APU was running and the external power had been disconnected.

The reasoning behind the latter was experience showed most “challenging” problems (random ECAMs, CIDS issues requiring resets &c happened when switching power supplies with a high load. Not SOP or in the manuals but wise experience nonetheless!

sonicbum 10th Jun 2020 09:15


Originally Posted by Denti (Post 10807334)
Really?

With a 25 minute turnaround, the fueller connects as soon as the doors are opened, and the flightdeck crew will start with the cockpit preparation as soon as they have finished the post-flight flows.

You would be surprised to know there are airlines out there with much larger turn around times.


All times are GMT. The time now is 11:44.


Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.