A320 Push back on battery only
 

Hello guys,

Last week I had an usual scenario. We had no APU, and when we requested engine start at the gate ATC did not allow due to construction behind the aircraft. Our only option was to disconnect the EPU and to push back on battery only. Then they brought EPU and external high bleed pressure via vehicles. As I remember, when you are on battery only the mechanical horn will sound as the ADIRS are aligned. So before removing the EPU I turned off the ADIRS, then after push back completed and EPU connected I proceed with the alignment.
My question is: What are the consequences of leaving the ADIRS running on battery only? Are they going to overheat? That's what I was told and that's what I believe but I could not find any reference about it; It is just my assumption after checking the MEL about the mechanical horn. Some other guys mentioned it might drain the battery... :mad: right?
Also I waited for ADIRS to be fully aligned before starting the engines... I never had this situation before and I was not 100% sure it would be a good idea since I had alignment fault just because of gusty wind or rough cargo loading in the past.
The FCOM just states that if alignment is still in progress while one engine is running it will be written in amber on the Ecam memo. I guess it might work just fine.

The warning horn is to tell you that there is no avionics cooling to the ADIRS, if you leave them on they may well overheat. Hope this helps.

Hello Turin,
Thank you for your reply. That’s what I had in mind but could not find anything written about it. If you have any reference about it I would be happy to have a read.
Cheers.

Hi Pineteam, If you left the IRS 1 on all night - then it might drain the battery flat.

This iinfo is from my original paper Training manual in 2003 from Airbus.
ADIRU 1 power supply is normally AC ESS but will take power from HOT bus 2 until the battery is flat.
ADIRU 2 will take power from HOT bus 2 for 5 mins.
ADIRU 3 will take power from HOT bus 1 for 5 mins.

so I guess you could have left the IRS in NAV during push back provided you were re-connected with power within 5 mins - else IRS 2 and 3 would have shut down automatically.

I can send you pdfs of the relevant pages.
Nav Electrical power supply

Electrical distribution

I’d just switch everything off. You’ll be starting from dark and the ADIRS will align long before you can set it all up.

It begs the question, how much work was being conducted behind the plane at the time? Could the work be paused? Particularly now, I wouldn’t want to be stuck in a small metal tube with no airflow for what would be an extended amount of time at my company.

Are inbound planes required to be towed in?

Hello Goldenrivett,
thank you for the infos! I will pop you a PM with my Email. =)

Actually everything in the MCDU was still there. Just some spurious ECAM which disappeared after Engines start.
After acceleration phase also the FMGS assumed descent phase instead of climb phase. Just needed to reinsert cruise altitude to recover.
But yes I agree.

Arf, it was ridiculous since the construction was quite far and I could not see any workers at that time and we entered the gate on idle thrust so why not be able to push back on idle power on single engine is beyond my understanding.

As you said, my main concern was the passengers as it was almost night time and a hot day. I was afraid, one of them would be claustrophobic and freaked out but luckily clear announcement was made to explain the situation and according to the CFA the pax were fairly calm.

I thought the horn was there to warn ground staff that the batteries are draining so I learned something today.

by the way each MCDU has its own battery so Inputs don't get erased.

while we’re here, I’d like to ask what your considerations are when shutting down without apu or external power? System wise, and passenger wise.

“The FMGCs are supplied by the A/C electrical power. The FMSs contain batteries which can maintain power supply and allow to keep entered data in the memory for at least 10 mn, in the event of lost of normal electrical power supply.”

Thales New FM Pilot's Guide

RELEASE 1A (S7A)

MD83FO

Can’t say I’ve ever shut down without APU or external services. If it had to happen though, I’d keep #1 running until pax and bags are off.

Until you realize the ground handlers are not authorized to come close and touch a live plane. And then shut her cold like the rest of us. :ouch:

A: in the day 95 per cent of customers don't notice the slightest
B: in the night it is worthwhile to explain and ask to keep seats until the GPU powers the lights again.

Check Airman

What side of the aircraft are your passenger steps?

FlightDetent

Our below the wing folks only have to wait for #2 to be shut down before they can start offloading baggage. SOP for APU inop is to taxi in, set brake, either have a gpu plugged in or wait for the jet bridge to saddle up to the plane and connect to that power and then shut down #1.

If we are to “go dark” with an APU but no gnd power we wait until the folks have gotten off and then shut down the APU, etc.

We don’t have a normal procedure to deplane without power and in the 27 years I have been here (there) I don’t recall having that happen. (yet)

I always thought that the warning horn was to alert ground staff that the batteries were being drained by the ADIRS... Would ATC let any aircraft taxi into the gate, or were they towed in? I believe you took all reasonable precautions. Nicely done!

CaptainMongo

Understood, sounds reasonable and proper. Depends on the network you have: some different place, on an awkward day, that SOP toolbox might just be empty.

Opinions might differ. For myself deplaning a cold aeroplane in the daylight is less overall risk than running an ad-hoc untrained, unprepared, live engine ground servicing show without a headset and possibly common language. Remember, the reason behind this scenario is the GHA could not cater for APU-inop airplane in the first place.

It's not a big deal if you seriously need to do it, daytime.

To confirm, my scenario is
APU inop + GPU=NIL -->> ENG=ON -->> BEACON=ON -->> ground servicing not authorized

Without judging or forming an opinion, I find it odd that for the SOP designers as you decribe:
- it is not OK to deplane cold, the preferred option is to wait for GND ELEC whatever it takes
(while at the same time)
- it is OK to unload cargo with ENG1 running, and that waiting a bit is not the more conservative choice.

Goldenrivett

Pax always board on the left. We almost always have a jetbridge. Can't recall the last time we operated a revenue flight with stairs.

CaptainMongo

Quite different here. If there's no ground power/air, we leave the APU running.

MD83FO

It pretty much depends on what sort of scenario we are considering. Let's consider dispatch with APU INOP to a remote destination where only 1 GPU/ASU is available and -surprise!- they fail as soon as you arrive at the gate. As others have said, I take it as an extremely unlike situation in standard commercial airline operations, but with that being said let's imagine You are also lucky enough to arrive at night time with this lovely scenario.

- you will need to coordinate with ground staff a disembarkation with the port engine (ENG 1) OFF and ENG 2 ON. If they are happy with that, great, if not then you will need to shutdown everything and use the emergency exit lights but you will be stuck wherever you are.
- once the disembarkation is completed, you need to restart ENG 1 in crossbleed and shutdown ENG 2 to allow bags offloading and refueling with one engine running (SUPP FUEL).
- when you are done with that, restart ENG 2 in crossbleed and shutdown ENG 1 to allow pax embarkation on the port side.
- you are now ready for pushback or taxi and can start ENG 1.

I reckon this sort of scenario could possibly happen only if you are extremely unlucky (no apu, no gpu, no asu) and conducting a charter flight for a humanitarian purpose and need to get the hell out of there ASAP. Not our ordinary day at the office as airline crew members.

I had that scenario in asia, no APU or GPU, right engine shutdown, off loaded cargo and pax on the right side, refueled form the left side while loading cargo and pax.

Interesting experience then! Are You sure though You refueled on the left side? The procedure specifically calls for a RH refuel with ENG 1 running.