Fuel Jettison - Tme to Remain

[emerydc8]

Hi Hardy,

I noticed that I could not get the "time to remain" to indicate anything other than zero on the lower EICAS fuel page without opening the jettison valves. On the ANA 744BCFs at my airline, it is common on preflight to turn the jettison selector to A and roll in a fuel figure based on subtracting the max landing weight from the actual takeoff weight. I understand that during actual jettison it would update for accuracy after 90 seconds of dumping, but this would roughly be the time required to dump down to MLW in case of an air-turnback.

I couldn't find a model in PSX where I could get this to work. I tried it with the models that had the MLW on the jettison selector too and it still indicates zero. Do you think this is just an option on certain airplanes? Thanks. Jon D.
My manual states:

Fuel jettison is initiated by rotating the fuel jettison selector to A or B. When a jettison control system is selected, the fuel temperature indication on EICAS is replaced with the fuel to remain quantity indication. The jettison manifold and jettison time display on the fuel synoptic.

[John H Watson]

My engineering notes don't go into enough detail. It just says JETTISON TIME and FUEL TO REMAIN appear when the jettison system is activated (and the activation procedure in my books includes all steps, including the opening of the nozzle valves). However, from past experience, I know that the JETTISON TIME and FUEL TO REMAIN appear as soon as you move the selector to A or B. Having said that, I've only ever seen a JETTISON TIME of zero. This, perhaps, was because I only ever selected the switch to A or B with less fuel in the tanks than the dump value. Whenever there was more fuel in the tanks, either the aircraft was being refuelled or the flight crew were on board (or both), so I wouldn't be touching the jettison controls at this time.

Note that the Jett Nozzle valves have no automation (purely manually operated by the switches). During refuelling, the tanker will be pumping fuel directly into the fuelling/jettison manifold, so if the nozzle valves are opened, fuel will come straight out of the wingtips onto the tarmac (I don't know if you get the "red screen of death" in PSX when you do this  ). According to my notes, even though the fuel synoptic will show a jettison pattern, the fuel system will not be reconfigured for jettison until at least one nozzle valve switches is pushed (and there is power to the respective nozzle valve CB on P6). Whilst the nozzle valves will open at any time, I can't recall if the pump logic and other jettison valves need an in-air signal.

Regarding options... ANA were somewhat infamous for adding lots of options to their aircraft (we had one of their 767 Freighters)

[Hardy Heinlin]

I don't know if it's an option, Jon.


|-|ardy

[emerydc8]

We only had one ERF and I didn't get to try it, but the ANA birds definitely allowed us to do this. I talked to a friend in training at Atlas and he said that his instructor just showed him how to do this without opening the jettison valves. Thanks for pulling out the manuals on this, John.

[Hardy Heinlin]

So should the jettison controller calculate a theoretical jettison fuel flow based on theoretical standard settings of pumps and valves even when there is no actual jettison fuel flow detected?


|-|ardy

[emerydc8]

Hi Hardy,

This may be a crude method, but it's all we had on the classic.

JETTISON SYSTEM -------------------------------------

•   One (1) nozzle each wingtip.     Left nozzle....no 2 DC      Right nozzle....Ess DC
•   Six (6) jettison pumps   Two (2) jettison pumps in main tanks 2 + 3
   Two (2) jettison\override pumps in center tank.
•   Approximate dump rate with six (6) pumps + engine burn = 5,000 lbs\min.

[Hardy Heinlin]

This feature is now available in PSX 10.0.9-beta10:

http://aerowinx.com/board/index.php?topic=3685.0

[emerydc8]

Thanks!

[Britjet]

I specifically tested this some time ago by making the upper panel selections on the ground.
There is obviously no jettison, and there is no rate/time display.
I can test it again next time if you like.
Peter.

[Hardy Heinlin]

In flight it may be different ...


|-|ardy

[Britjet]

It's is definitely different in flight. I was testing earlier something Jon said, I think, about Atlas culture of establishing jettison time prior to take-off in the event of a return..
It couldn't be done in the BA sim, but easy to check this again next time..
Peter

[Hardy Heinlin]

Hi,

now since it has been reconfirmed that the BA sim doesn't indicate the jettison time on the ground, can we conclude that this feature is airline specific?

In PSX the feature is available on all aircraft. Is it necessary to make it optional? Does it confuse anyone?

(Has anyone tried it on a real BA 744? Maybe it's a sim issue?)


Regards,

|-|ardy