A320 Battery Fault - Fuel consumption increase?
 

Can anyone shed light on this?

On A320 , Elec: BAT 1(2) FAULT

Fuel consumption increased
FMS PRED UNRELIABLE

Why does the fuel consumption increase with a battery fault?
Why there is no fuel penalty factor in the QRH regarding this failure?

Thanks

Hi Citation2.

In our FCOM this note for the particular fault only appears for recent MSNs (5318, 5592-6267).

The level 2 note says

FUEL CONSUMPT INCRSD
This message is triggered when the failure (or combination of failures) affects the nominal aerodynamic characteristics of the aircraft.

FMS PRED UNRELIABLE
Disregard FMS fuel predictions and refer to QRH/PER-B Fuel Penalty Factors Tables in order to find the applicable Fuel Penalty Factor.

I guess that means you have to check through your sys pages on ECAM and ascertain which bits have been affected (spoilers/ailerons etc) and then apply the relevant factor from the tables in the QRH. As you say, even for one of the MSNs mentioned I cannot find a penalty referenced back to the Bat Fault.

Best of luck.

My FCOM only states that:


"Battery contactor is automatically opened by battery charge limiter" and "Crew awareness" is required. Besides "APU BAT START NOT AVAIL" message on STATUS.

Any Airbus experts , or engineers to clarify why a battery fault would lead to a fuel consumption increase, on new MSNs ?
If it happened, I would like to know why and what is the fuel penalty factor to be applied?

In my company's fcom it applies to A320 with CFM and A321 with IAE

According to the QRHs for our fleet, this appears to be the case only for A320s with CFMs (MSN 800-900 in our fleet). We have IAEs of a similar age, they don't have this entry.

Went through the FCOM couldn't find anything. The following is just a guess. In the case of flight on batteries only you will notice that the engine anti-ice valves are automatically open (increased fuel consumption). I wonder if the same thing is done just incase the faulty battery problem develops into something more serious. If further electrical systems were lost, could we guarantee the ability to select engine anti-ice after the event?

Superpilot
The A320 is just like all the other airliners I have flown... without electrics the engine anti-ice valves are open, with electrics they are held closed until you switch them on.....

Thanks for that info. It makes sense however I don't see this from looking at the electrical systems architecture diagrams.

Engine anti-ice would be left open in case of total loss of electrical network. This is not the case in BAT 1(2) Fault.
Suprisingly if you switch OFF the batterie(s) manually , battery contactors are disconnected , and nothing happen in terms of fuel consumption, FCOM says :

"Battery is abnormally selected off.

Crew awareness.

STATUS APU BAT START NOT AVAIL"

But in case of deficiencies in the battery , BCL still disconnect the batteries contactors , but in that case:

Elec: BAT1(2) fault

Battery contactor is opened automatically by battery charge limiter.

Crew awareness. FUEL CONSUMPT INCRSD FMS PRED UNRELIABLE

STATUS APU BAT START NOT AVAIL FUEL CONSUMPT INCRSD See (1)

FMS PRED UNRELIABLE

switching the bats off is a different scenario ,
the outcome may appear the same .. the bats are disconnected from the bat bus ,

but in the bat 1 (2) fault scenario the system has detected a thermal runaway in the battery and obviously in that situation you could very shortly loose the hot bat bus for whichever bat is failing ,

hot bat bus feeds back up dc to secs ,elacs and adirus ,

hence i suspect this is the avenue to influence the comment

FUEL CONSUMPT INCRSD
This message is triggered when the failure (or combination of failures) affects the nominal aerodynamic characteristics of the aircraft.

i will try and dig a bit deeper in the manuals to explain any change in flight characteristics with loss of back up dc power , but dont expect a quick answer as im busy with fixing the things .

Thanks for that

turn and slip,

Why only CFM though? I wouldn't have expected flight computer related degradations to be associated with engine type.

STATUS APU BAT START NOT AVAIL". Could someone shed some light on this...Does this mean that APU start is not available at all? An explanation would be appreciated. Thanks in advance.

If batteries are not connected to DC BAT BUS for whatever reasons APU cannot be started.

There is a penalty for DC Ess bus,and the fuel critical inop sys is spoiler 3. DcEss is powered through the DC Bat bus .I wonder if this is what the note refers to?

I found the following in PRO-SPO-40-50, ABN and EMER Procedures:

Electrical Emergency Configuration

Engine Anti-ice

Engine anti-ice valves are permanently open, although the ECAM memo ENG A.ICE is not displayed on the ECAM (except if the ENG A. ICE pb is at ON).

This confirms what tyropicard said and whilst it's not discussed in the context of the condition you've described, it highlights that there are situations where engine anti-ice can be on but without the relevant status or message to inform the crew. "Increased fuel consumption" is most probably sensed by another means (not the engine anti-ice pb).

Done a bit more checking and this only applies to the newer sharklet fitted A320s not to the ordinary ones or A319s.

For ELEC BAT 1(2) FAULT there are no FC actions but the bat contactor opens automatically. If, however, you manually switch off the batt then the extra line about extra fuel consumption does not appear.

In our aircraft TR1 powers DC1, DC BAT BUS and DC ESS, TR2 powers DC2.

Eng A/I VLV 1 is powered from DC1 and VLV 2 from DC2 so it would appear that is not the source of extra consumption as they will still be powered closed even if Bat 1 (2) is disconnected.

I have scoured the electrical supply sections of FCOM and cannot find anything apart from one EIU and one FADEC channel powered by Hot bus 1 or 2. That doesn't mean there is nothing else it is just we are not worthy of the information.

I will try to get an answer from one of our exceedingly helpful engineers but our paths will have to cross to do that so standby.

Hello again all ,

For anyone who hasn't had access to this , Airbus safety first magazine Jan 2012 issue 13 , has some background information on fuel penalty factor which may be of some interest.


Airbus Safety First Magazine

OK the boffins have replied and the answer to the Batt fault (everyone remember that?) is

If you have an ELEC BATT fault, you can lose the ELAC roll channel and the SEC’s take over. Roll is now controlled by the spoilers, increasing drag, increasing fuel consumption.

Apparently it is for all S/Ns.

That's all there is to it. Simple isn't it..

Now I have to go lie down for a while.

Lurkio, I think the article referenced by Turn and Slip provides a better explanation.
It states that the two causes of increased consumption caused by increasing drag are failures affecting the landing gear or landing gear doors, or failures affecting the flight control surfaces.

it elaborates on this last point-
Three specific flight control configurations create a differing amount of drag
1-The surface is blocked in the fully deflected position.
2-The surface is free and floats in the wind
3-The surface(spoilers only) slowly extends over time.(floats). This can be caused by a hydraulic or electrical failure.

DC Ess bus (spoiler3) is powered from DC Bat bus and hence from BAT1 and I think from reading the footnotes that this spoiler will float when it is no longer electrically supplied , leading to a corresponding increase in fuel consumption.