>FUEL IMBALANCE

[osss]

Hello!

Aerowinx manual states (and sim actually does accordingly) that ">FUEL IMBALANCE" EICAS message appears when "difference greater than 1360 kg (3000 lb) between inboard and outboard main tanks after reaching tank-to-engine condition..". As far as I know the difference should be 2720 kgs.

For example, http://landrover.narod.ru/gershon/AIRPLANTANK/747-400_operations_manual.pdf page 881.

offtopic: for CATII and CATIII approaches it will be great to have some autopilot related malfunctions such as AP or AT disengagement and no FLARE mode at 40'.

Thank you
Stan

[Hardy Heinlin]

Hello,

I guess you're right. I can't remember why I used 3000 lbs.

Re A/P malfunctions: There are autopilot malfunctions on the "Nav" page for each FCC (L, C, R). They are attitude errors. "Severe" is without autodisconnect, else with it. You can program an MSL altitude for the trigger.

Re A/T malfunction: You can indirectly fail it by an FMC L failure (when FMC L is the master). This is on the "Nav" page as well, and you can program an MSL altitude for the trigger.


Regards,

|-|ardy

[John H Watson]

How do you interpret the conditions in our FCOM?

After reaching FUEL TANK/ENG
condition, there is a longitudinal fuel
imbalance of 2,720 kgs between
inboard main tanks and outboard main
plus reserve tanks.
Message no longer displayed when
difference less than 450 kgs.

Vs the online manual

Fuel difference of 2,720 kilograms
between inboard main tanks (2 and 3) and
outboard main tanks (1 and 4) after
reaching FUEL TANK/ENG condition.
Message no longer displayed when
difference less than 450 kilograms.

[Hardy Heinlin]

My interpretation:


FCOM A:

imbal = ( RES1 + M1 + RES4 + M4 ) - ( M2 + M3 )


FCOM B:

imbal = ( M1 + M4 ) - ( M2 + M3 )

[John H Watson]

The FIM generalises:

SUMMATION OF INBOARD MAIN TANK QUANTITIES
RELATIVE TO SUMMATION OF OUTBOARD MAIN
TANK QUANTITIES DIFFER BY MORE THAN 6000 LBS
(AFTER TANK TO ENGINE CONFIGURATION IS
REACHED).

We can assume the outboard tanks are outboard main plus reserves .. but in normal situations the reserves will be empty by the time tank/eng config has been reached, it will be ( M1 + M4 )

[Hardy Heinlin]

Hello,

I guess you're right. I can't remember why I used 3000 lbs.

[...]

Regards,

|-|ardy

I just rechecked my PSX code from version 10.0.0 up to the latest update: It's correctly set to 6000 lbs, and in my tests the message only appears at 6000 lbs as it should. So the "3000" is just a typo in the PSX manual.

Note that the "3000" is used for the >FUEL IMBAL 1-4 message.
This may be confused with the >FUEL IMBALANCE message.
Also note that an imbalance message is cleared when the respective difference decreases below 1000 lbs (hysteris to avoid flip-flops).


Regards,

|-|ardy

[Hardy Heinlin]

After reaching FUEL TANK/ENG
condition, there is a longitudinal fuel
imbalance of 2,720 kgs between
inboard main tanks and outboard main
plus reserve tanks.

"Plus reserve tanks" is now added in PSX 10.34 as well:

http://aerowinx.com/board/index.php?topic=4191.0


|-|ardy