A320 APU Fire Test with APU already running

[CaptainGrizzly]

Hi all

Is there anything somewhere in the books that specifically prohibits this during Cockpit Preparation?

​​​​​​The APU fire test does not shut down the APU on ground and as far as I am able to interpret the procedures, crew has to perform the APU fire test even if it is left running by previous crew/maintenance.

​What's your take on this?

Regards

What's y

[RUMBEAR]

We do it every day. I don’t believe their is any prohibition as it’s necessary to follow the Preliminary cockpit preparation in most cases.

[Ondraayyy]

My company check pilot asked why I did the APU FIRE TEST as the APU is already running. I looked it up on the A320 FCOM there is not restriction saying that we shouldn't do it. Any take on this?

[hans brinker]

test the APU, no mention if it is running or not, so just test the APU

[Denti]

I had the test once aborting an APU start cycle, but that might have been a fluke or coincidence, apart from that, no problem whatsoever with testing it while the APU is running.

[hikoushi]

The APU AUTO EXTG test button on the overhead maintenance panel will cut off the APU if running. The regular fire test has no effect at all, and should be done even if it is already running!

[FlightDetent]

Asked several times over the years, and all the answers are already provided above.

Once a a line engineer told me the only issue is with a in-depth MX / warning system troubleshooting procedure , when a C/B gets pulled.. The system logic would err on the conservative side and fire the squib. :\ Just a story.

[pineteam]

Maybe I'm missing something but I don't understand why you need to perform the APU fire test. If you arrive at the aircraft and APU is already running, it means the maintenance has turned it on and has done the APU fire test already.
In the company I work for, we only do that test if the cockpit crew arrives at the aircraft and APU is not running.

[hans brinker]

Maybe I'm missing something but I don't understand why you need to perform the APU fire test. If you arrive at the aircraft and APU is already running, it means the maintenance has turned it on and has done the APU fire test already.
In the company I work for, we only do that test if the cockpit crew arrives at the aircraft and APU is not running.

Different SOP mabe?
Our SOP is that when you pick up an aircraft, you test the APU fire detection, running or not. It has to be tested every day and maybe it was left running from the previous evening and the test is required again (we operate 24/7).

[FlightDetent]

Doing less is inherently safer, in this respect reduced amount (of unnecessary) decision making is better.

If the FCOM suggestions work unaltered, it is easier just to follow them - same as Hans'. For us new crew = new start, irrespective of what has been left running.

pinteam: it is my personal belief the reason for the BAT check split between PM and PF during the cockpit prep is to cover for one of the guys actually not doing the job at all. On what is a survival-critical system in case of a larger failure inside the electrics. Good SOP would have such "recovery" features embedded.

That's where your company's way - whilst perfectly reasonable under the assumed state of things - falls short of the (slightly ignorant) FCOM regime, me thinks.

[pineteam]

Ok, I get your points. Thank you guys.

[CaptainGrizzly]

Thanks guys. Interesting feedback.

Regardless of individual company SOPs, it is clear now that there is nothing in the Airbus procedures prohibiting it.

@pineteam

It often happens that an aircraft arrives within a few minutes of the next departure; in such cases, the previous crew leaves the APU running to save APU start cycles. Therefore, we cannot assume whether they left it ON or the engineering switched it ON. Even if its engineering that did it, it's still a part of FCOM procedure and a change of crew definitely necessitates a fire test.

The point of asking this question was due to the fact that I was recently confronted by a Captain who asked me to prove where its written. I pointed out there's nothing prohibiting it, and with back to back flights with crew change, sometimes the APU remains ON continuously.

Apparently some people have their own interpretations of the FCOM. Not everything is mentioned nor can be mentioned explicitly for every situation. Thats how it works.
​​

[ironbutt57]

do you fly the entire 320 family of aircraft? if so you might want to research what happens if you perform the APU fire test in other models, and see if performing the test while the APU is running has a negative effect on those models...one possible reason for you company' SOP......in any event, the SOP should be sufficient reason for you to not perform the test....no?

[Check Airman]

do you fly the entire 320 family of aircraft? if so you might want to research what happens if you perform the APU fire test in other models, and see if performing the test while the APU is running has a negative effect on those models...one possible reason for you company' SOP......in any event, the SOP should be sufficient reason for you to not perform the test....no?

I've flown the 319, 320 and 321 for 2 different airlines. Neither has specified APU on or off for the test.

[vilas]

Is there anything that forbids APU test when it's running? The answer is NO. Rather if you are not sure if the test was done you should do it.
Below from FCOM PRO NORM SOP
FIRE
APU FIRE pb-sw.......................................................... .........................................IN and GUARDED
AGENT lights ............................................................ ............................................................ ..... OUT
If the APU is already running, ensure that the following check has already been completed. If not,
perform it.
APU FIRE TEST pb.......................................................... ......................................................PRESS
Check :
‐ APU FIRE warning on ECAM + CRC + MASTER WARN light (if AC Power available).
‐ APU FIRE pb-sw lighted red.
‐ SQUIB light and DISCH light on

[Black Pudding]

If you arrive at the aircraft and APU is already running, it means the maintenance has turned it on and has done the APU fire test already

Not necessarily so. That’s like requiring you to do and APU fire test as you taxi in before you switch it on before engine shut down. You wouldn’t. Why would you presume engineers will always do a test. Your preliminary cockpit procedure requires you to do it on YOUR first flight of the day.

[ironbutt57]

I've flown the 319, 320 and 321 for 2 different airlines. Neither has specified APU on or off for the test.

reason I asked, our serial number 321's APU would shut down if the APU fire test were activated...cant say for sure if ALL 321's do this or not, all of ours did

[pineteam]

Not necessarily so. That’s like requiring you to do and APU fire test as you taxi in before you switch it on before engine shut down. You wouldn’t. Why would you presume engineers will always do a test. Your preliminary cockpit procedure requires you to do it on YOUR first flight of the day.



I know cause in our company, aircraft are always shut down completely after the last flight of the day. Then before the first flight in the morning, maintenance will start the APU before the cockpit crew arrive. I never had the chance to come in a dark cockpit so far. Also, never in the 5 years flying Airbus I saw a cockpit crew testing the APU fire pb while it was running. Thus my question. The FCOM Regarding the cockpit preparation assumes the APU was not running. It’s not very clear IMHO that we are supposed to test the APU if already running. In any case, I trust our maintenance to have done it. It’s part of their daily check.

[vilas]

The FCOM Regarding the cockpit preparation assumes the APU was not running. It’s not very clear IMHO that we are supposed to test the APU if already running. ​​​​​​
pineteam, it is very clear. I have produced airbus FCOM SOP. It just checks the circuitary. There's no problem what so ever.

[RUMBEAR]

I think Airbus are very clear. First two lines under the title GENERAL - PRELIMINARY COCKPIT PREPARATION. Items marked with an asterisk are completed for a transit stop with no crew change. Otherwise complete all items.

[pineteam]

Hi Vilas,
I understand there is no problem of testing it while it's running. But the way it's written, it assumes you arrive at the aircraft with APU off which is never the case in the company I work for. I understand the check must be done for the first flight of the day. Some people will argue that you can't assume maintenance did the check... Well, we trust them to maintain our aircraft airworthy; I think we can trust them to have done a simple no brainer task as an APU fire test 1h before the crew arrive at the aircraft. Or maybe all the pilots working in my company are foolish. lol:}

[vilas]

Systemically it's permitted. Somebody needs to do it. No need for pilots to do the test if maintenance guys have a procedure to start APU only after fire test is done. I train an airline who's procedure says not do the test if APU is running.

[FlightDetent]

@pinteam

According to Airbus the check should be done with a new crew. How closely each individual airline follows and why (not) would be an endless debate, though still enlightening at some points.

AFAIK running the APU is a not part of the DY.

The quoted sentence "If the APU is already running, ensure that the following check has already been completed. If not, perform it." is not in my recent FCOMs but I see it in the 2014 edition.

For your last sentence: crowd mentality and assuming things can be a biting bitch. For instance, I hear of an airline where the agreed saving technique was to shoot approaches with F3 and increase Vapp by +15 kts for "safety" and "easier landing". :E Or another one, where when calculated ASD=ASDA on flex takeoff they would modify runway by -100 m at DER to get a "margin" - of course only on the long runways where it was possible. Emergency torches being used for walkarounds "to test them" as supposedly they re-charge when back in the cradle. Having already left a cloud into the blue, E-AI must not be switched off until ECAM MEMO : ice not det, in order to "prevent getting a QAR".

If your OPS always start in the morning at a base where MX power-up and prepare the A/C, including running the APU, there is probably no need to change the drill. Situation-driven SOP, nothing wrong with that. The book provides protocol-driven SOP that are situation independent.

[Sig229]

This didn't happen at an airline, or in an Airbus, but it still relates. Started a trip on an airplane that had maint done overnight that involved running the APU. During preflight checks the APU fire test failed. Called maint and turns out the tech had only recently left so he came back out in just a few mins. Upon talking to him and mentioning the fire test he commented that they (mx) never do the fire test before starting the engines/apu. So just because something is supposed to be done does not mean it will be!

[pineteam]

Yes you can assume it has be done. Same as you assume the loadsheet has been done accurately or that the maintenance has done all his duty as a good professionnal. We don’t go and check the loading or engines by ourselves. We trust them!

[CaptainGrizzly]

Is there anything that forbids APU test when it's running? The answer is NO. Rather if you are not sure if the test was done you should do it.
Below from FCOM PRO NORM SOP
"If the APU is already running, ensure that the following check has already been completed. If not,
perform it."

Apparently, that note is not included in my FCOM dated 4 DEC 18. I guess it depends on the MSN numbers; the latest we have is in early 3000 series. What's yours?

[Roj approved]

Our FCOM States:
APU FIRE.................IF NOT RUNNING CHECK/TEST

But it appears to be a company specific procedure.

I know in the past i have done it, and the APU continues to run, but the bleed shuts down momentarily.

[vilas]

CG
Yes. I also can't find it in 1917 manuals. It appears to have been removed but not forbidden. This is in 2014 airbus manufacturer manual. The MSN is given as 9761 A320-214. Actually Airbus publishes new manual in their code which for this is 18CMHE which translates as C​​​​-CFM, M-METRIC, H-HONEYWELL, E- ENHANCED GPWS.

[FlightDetent]

Yes you can assume it has be done. Same as you assume the loadsheet has been done accurately or that the maintenance has done all his duty as a good professionnal. We don’t go and check the loading or engines by ourselves. We trust them! We do not trust them, neither we do doubt them. We do our part of the job as professionally as a human can, which means quite poorly on a bad day - same as they might. As well, over here I am not supposed to assume the LDS is ok, I am required to check it. I know what you mean, but that sentence as written is a sword you're leaning over deeply.

Ever heard of cowling flaps flying open? That, of course, would never happen as it is a dual-check and sign procedure, then verified by pilots.

BTW, the DY check has a list of actions; dare go ask to see the APU fire test on that list? ;)

[CaptainGrizzly]

Yes you can assume it has be done. Same as you assume the loadsheet has been done accurately or that the maintenance has done all his duty as a good professionnal. We don’t go and check the loading or engines by ourselves. We trust them!

Would disagree with you here. FCOM, or any other manual for that matter, doesn't tell you to calculate your own loadsheet nor does it tell you to go and check the loading or engines; however, it does tell you to perform the APU fire test.

Trust is valid when something is not a part of your procedure. When it is, you cannot assume it has been done.

[hans brinker]

I know cause in our company, aircraft are always shut down completely after the last flight of the day. Then before the first flight in the morning, maintenance will start the APU before the cockpit crew arrive. I never had the chance to come in a dark cockpit so far. Also, never in the 5 years flying Airbus I saw a cockpit crew testing the APU fire pb while it was running. Thus my question. The FCOM Regarding the cockpit preparation assumes the APU was not running. It’s not very clear IMHO that we are supposed to test the APU if already running. In any case, I trust our maintenance to have done it. It’s part of their daily check.

We have no last flight of the day as we operate 24 hours per day. I get to a cold dark cockpit at least a couple of times a month, and if there aircraft has been switched on by MX there's always things still off we switch on like crew OX. Our OM specifically states to test regardless if it's on.

I guess there's a lot of different ways to get the same thing done......

[pineteam]

Would disagree with you here. FCOM, or any other manual for that matter, doesn't tell you to calculate your own loadsheet nor does it tell you to go and check the loading or engines; however, it does tell you to perform the APU fire test.

Trust is valid when something is not a part of your procedure. When it is, you cannot assume it has been done.

You have a good point. Things is that FCOM procedure assumes you arrive in a dark cockpit which is not our case. For example to check that APU area is clear is a mandatory item but not applicable for us as the APU is already running. The APU fire test is also done by maintenance when they power the aircraft so as the cockpit then don’t do the fire test. I think that’s the logic behind it. I would not mind doing it as you mention we shall do it, but my company does not expect us to do it.

[Escape Path]

Our FCOM is quite clear: Upon arrival of a new crew taking on the aircraft perform a COMPLETE preflight inspection. It’s not dependent on whether the previous crew or maintenance did it. If that’s the case, I might as well start questioning every single procedure Airbus publishes. How many times have you, during your preflt, found something that’s not right yet it was supposed to be catched on the first flight of the day! Do yourself and your crew a favour and test the thing as instructed on the manual, whether the APU is off or on (as nothing happens). Takes not longer than 3 seconds and who knows, maybe one day you’ll even catch a fault that happened to you but not the previous crew

[cptkris]

The FCOM and QRH are Airline specific. In my airline’s QRH the wording is
APU FIRE........................... *JIF NOT RUNNING CHECK/TEST”
the J* annotates it’s a Jetstar specific procedure.

[ppppilot]

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1224x272/firetest_0435065920895ceaead4ddec7a5c3fcab51606b5.jpeg
A380 panel

Don't know about A350 but A380 has only one fire test button that checks all the loops at once, wheter the APU is running or not

[Sidestick_n_Rudder]

After flying Airbus for 7 years I moved to a Boeing and guess what... no requirement to test APU, or indeed anything else in the preflight :eek: