Classic British Flight Sim

Since I only operated the German Internals, it could even be that we didn't put any fuel in the centre tank as sector lengths were from 35 mins to 1 hour 25 mins...Even the odd Berlin to London was only 1 hour 55 mins :think: Perhaps we just left the centre tank full and isolated and only brought it into use for the odd long sector. Anyway, I can't remember any switching of pumps or cocks. A set of BA Drill Cards for the S111 would reveal all...Anyone?

What a nice discution this post become... Thanks for all masters!
I'm always learning with you...

Just been trawling through some old posts and came across this one.

The principle on all aircraft with a centre tank is load the wing tanks to full first and then the centre tank. The reason you do not put any fuel in the centre tank without full wings is to do with bending moment on the wing roots, i.e when you fill the wings to full you are putting weight outboard of the landing gear (pivot) and therefore alleviating the bending moment on the wing roots.

This is the same reason for the Zero Fuel Weight limitation on the aircraft, the fuselage is effectively a weight hung between the wings. Aircraft with sponson mounted gear (C130, SD360, ATR42/72) do not have a zero fuel weight limitation.

You use the centre tank to top up the wings as the fuel is burnt off.

If you do not have full wings, any fuel contained in the centre tank is considered as "trapped fuel" or "ballast fuel" and must be included as "payload" in the zero fuel weight of the aircraft.

Nige C

NIgel

Thanks for digging this thread up again.

Now I have time to re read and thing about it -- The MD80/Dc9 is the same way -- you basically run with crossfeeds open until the center tank is dry (or at
a level you wish for "trapped" fuel (Yes we use this method for ballasting emptying MD80s here at the real world airline). In the 1-11 (well Dan Airs 300/400s)
The procedure was to run with crossfeed pumps on until the CT was depleted then shutoff the pumps and close the valves. I had this discussion on my lsat obs ride (form KLAS-KEUG and back if anyone is interested) specifically about trapped CT fuel and where it was added. Many of our crews labour under the misconception it is added to the BOW where in truth it has to be added to the ZFW. To that end it isnt a procedure that is recommended on anything but ferry and empty reposition flights.

Leif

Hi Leif,

I remember having a "discussion" with a B757 skipper at LGW who wanted me to up the MZFW by the amount of trapped fuel he had. I said no, it's the other way in effect. Upshot was, I told him if he wanted a loadsheet doing that way, he could do it himself coz I wasn't going to put my name on it. Lots of huffing and puffing but the next day I received a case of beer and an apology.

Nige

I dunno how common this was but you can't take fuel directly from the centre tank on the 1-11 either. It has to be pumped into the wing tanks then used from there. Sort of still on topic I think

ATB

DaveB :tab:

Yep, fuel gets pumped out to the wings, maintaining them full (i.e keeping weight outboard) then to the engines.

Nige

DaveB wrote:That said, the Commander can still refuse to fly if he wants a particular thing repaired even if the MEL states that he can fly with it U/S
ATB
DaveB :tab:

That said - if the Capt wants the thing fixed any ensuing delay goes down as a Code 65 'Crew Request', not a 41 'Technical' as the a/c was legal to fly.


Sorry I'm coming into this late but the One-Elevens I was licensed on had two different types of Ctr Tank fuel transfer. The 201/300's had Ctr Tank boost pumps that transferred into the wing. ( I got asked several question on that when I was doing my license oral exam ).

The 501/509 & 530 had two jet pumps for Ctr Tank fuel t/fer. This worked by taking a tapping of wing tank boost pump output fuel and directing it to a jet in the middle of a venturi. As the fuel squirted into the throat of the venturi it induced a flow of fuel out of the Ctr tank. There were float valves that prevent fuel transfer when the wings were full.

The right wing of the One-Eleven had a smaller fuel capacity than the left because the Ctr Tank Vent pipe went through it to the RH vent box. (I used to know the numbers but it is 25 yrs ago now since I last touched one

MALTBY D wrote:It really depends on which mark and how you fly it.
The average fuel flow over the past year with the CBFS va is...
BA11 200 = 2391 kg/h
BA11 400 = 2419 kg/h
BA11 500 = 2653 kg/h

These are for all flights though and cover long and short routes.
The amounts above per hour + 2000 kg should just about see you right.
Fill the wing tanks & only use the centre tank if needed.

DM

Oh well, I have found answers to my questions concerning 1-11 fuel. However I am still wondering if this roughly 2500 kg/h is for both engines, or for a single engine. I presume that it stands for two engines, am I right?

Hi asolyom

Yes.. that is total burn, not burn per engine

ATB

DaveB