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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. |
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. |
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. |
A longer discussion was just recently had here.
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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. |
Hi tdracer,
Airbus doesn't close the spar valve when you set the fuel switch to CUTOFF, 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." |
@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. |
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." 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. |
FD
do you not think it's unfair of AIB not to adjust the FCOM accordingly? |
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.
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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.
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Originally Posted by vilas
(Post 10805427)
My post #3 is a personal reply from Airbus.
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.....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)...... 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 ! |
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.
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At my company, if we waited for fuel to start our setup, we’d push late every time lol
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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. |
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.
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. |
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. |
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! |
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. |
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. |
It is possible to do it even faster :)
Some low costers have 25-30 min as standard turnaround time |
Originally Posted by Check Airman
(Post 10807849)
How do you accomplish a 25 minute turn in an A320? The shortest I’ve seen is closer to 45 mins maybe.
Otherwise, the critical path is the cabin. Hence: - remote parking, 2 sets of stairs - deplane 5 minutes - 10 min cleaning - 5 min CC procedures, security check - 10 min pax boarding - 2 min head-count - 3 minutes for engine start (IAE) It is necessary for CC to be exactly on their marks for the above, needless to say it is the redcap who runs the show. The weakest link in my experience is the delay between cleaners leaving and first PAP stepping inside. |
Originally Posted by FlightDetent
(Post 10807903)
35 is the target for quite a large portion of the European ops. Doable, for anything below 30 in my personal experience the crew procedures become limiting.
Otherwise, the critical path is the cabin. Hence: - remote parking, 2 sets of stairs - deplane 5 minutes - 10 min cleaning - 5 min CC procedures, security check - 10 min pax boarding - 2 min head-count - 3 minutes for engine start (IAE) It is necessary for CC to be exactly on their marks for the above, needless to say it is the redcap who runs the show. The weakest link in my experience is the delay between cleaners leaving and first PAP stepping inside. |
Originally Posted by vilas
(Post 10807771)
Going strictly by literature, it says during cockpit preparation no white light. So either put the fuel pumps on during refuelling or do the prep after refuelling. I am sure you are aware of the A320 incident where the crew taxied, took off and climbed to 370 when both engines flamed out and during dual engine flame out procedure they realized that the fuel pumps were off. They relit engines came back and landed.
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Originally Posted by Check Airman
(Post 10808076)
Impressive. Most of our outstations are planned for about a 1 hr turnaround. Rare to see under 50 minutes. If your day includes going through one of the hubs, 1.5 - 3 hrs is typical.
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In a previous company where we still had aircraft cleaning we planned 45 minutes for an A321, and that was very much manageable. In a LCC world where there is no aircraft cleaning during turn around, just a short tidy by the cabin crew which includes the security check. Head count is not necessary, and thankfully engine start is a bit faster on the CFM, except the LEAP if you are unlucky enough to have a NEO.
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Originally Posted by vilas
(Post 10808562)
Many Asian LCCs turn around in 25mts.
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Originally Posted by Denti
(Post 10808769)
In a previous company where we still had aircraft cleaning we planned 45 minutes for an A321, and that was very much manageable. In a LCC world where there is no aircraft cleaning during turn around, just a short tidy by the cabin crew which includes the security check. Head count is not necessary, and thankfully engine start is a bit faster on the CFM, except the LEAP if you are unlucky enough to have a NEO.
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No jetty for the superquick ops. AOBT is the first movement.
In reality a flash turnaround can be achieved, even repeatedly. But maybe 30%? There would be a padding in the block-flight-block times, to allow some schedule recovery. With a PRM passenger everything goes to hell. Unless you are flying for one of the three strongest LoCos, where penalties on the ground service providers are dire. And everyone else needs to wait. What was this thread about again? Oh that, shared 2 years ago
Originally Posted by MAR18
I read the explanation with a bit of sadness.
[...] 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 SOPs 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. |
Originally Posted by Check Airman
(Post 10808929)
Interesting that a few replies here have mentioned engine start as part of the turnaround time. Why's that? Here, most companies measure the turn time from IN to OUT on the ACARS, so it'd be a few minutes between OUT and engine start.
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Originally Posted by AerocatS2A
(Post 10808989)
Yeah, a push back is an extra 5 minutes leeway on the turn time.
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Originally Posted by FlightDetent
(Post 10808951)
No jetty for the superquick ops. AOBT is the first movement.
In reality a flash turnaround can be achieved, even repeatedly. But maybe 30%? There would be a padding in the block-flight-block times, to allow some schedule recovery. With a PRM passenger everything goes to hell. Unless you are flying for one of the three strongest LoCos, where penalties on the ground service providers are dire. And everyone else needs to wait. What was this thread about again? Oh that, shared 2 years ago |
Originally Posted by Check Airman
(Post 10809023)
I’m not really understanding this. I know that a lot of European airports use remote stands. Is this really factored into the turn times?
I’ve only deplaned via stairs a few times, but the turn time was always the same. If anything, the rear door is only usually opened for the cleaners to board. Even in a legacy carrier before i joined some LCCs we were happy to park on a remote stand, boarding and deboarding via two stairs is simply much faster than with just one entry. And yes, if possible, we always let the passengers deplane via both exits, it is nice for them and better for us. |
Thanks for the clarification on the delay code. Never seen that tracked here. I quite like the stairs, if I’m being honest. Shame we don’t do it more- as long as the weather’s cooperating.
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Point being for below 30 min you pretty much need two stairs so there are no dual turnaround targets, rather the airline might selectively choose to use remote only. Also, failure of turning on time has financial implications for the GHA. Having a SLA that specifies turnaround extra of 5 mins = 300 EUR penalty is not unheard of. Then it's fair to allow 3 minutes for engine start, once things are getting Excel'd. If the Teutonic system come up with a dedicated delay code, nobody really is surprised.
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Originally Posted by Check Airman
(Post 10809070)
I quite like the stairs, if I’m being honest. Shame we don’t do it more- as long as the weather’s cooperating.
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Originally Posted by FlightDetent
(Post 10809090)
Careful what you wish for. Imagine the cockpit load, more especially the lack of any lull to rev the brain down, if the target turnaround becomes 35 min. The GHA will learn how to match that so, day in and out, you'll be expected to make it too. Not to mention the possibility of 5 sector days.
So even if the working conditions are good, which they are at some outfits, although that might change now very fast, LCC flying is very hard work indeed, for both cabin crew and flight deck. |
Originally Posted by Check Airman
(Post 10809023)
I’m not really understanding this. I know that a lot of European airports use remote stands. Is this really factored into the turn times?
Originally Posted by Denti
Indeed, doing only minimum turnarounds can be very fatiguing. Especially for the PM (who does the walkaround where i work, but also the load calculation) it can be hard to get enough breathing time to visit the loo, especially when he is new to the operation.
So even if the working conditions are good, which they are at some outfits, although that might change now very fast, LCC flying is very hard work indeed, for both cabin crew and flight deck. To each, their own. Personally I'd much rather do a four sector day with minimum turn times rather than have a five to ten minute lull each time. Get to work, bang out the sectors, go home, that's my ideal work schedule. |
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