Peter wrote:
This is a good example of a complex fuel system: the B52
Anyone having flown with Twin Cessnas should understand it in a jiffy…
But on the serious side, the B52 has a flight engineer and for a reason.
This is a good example of a complex fuel system: the B52 
Capitaine wrote:
A French Staggerwing landed in a field a few years ago because one of the fuel selectors had broken
The same thing happened to a Mooney 201 a couple of years back. And that one has a bog easy 2 tanks system, but that does not help if the fuel selector breaks and simply turns freely instead of actually switching tanks.
tmo wrote:
Why are you surprised? They are magnificent planes…
Sorry, I meant I was surprised more people don’t run out of fuel. Maybe they don’t all have such a complicated system.
I see this one regularly which is impressive (Pilot article). There’s no mention of the fuel system except to take off on the main tank as it’s the only one vented for full fuel flow, and the procedure for running a tank dry.
Capitaine wrote:
I’m surprised they’re still flying.
Why are you surprised? They are magnificent planes…
A French Staggerwing landed in a field a few years ago because one of the fuel selectors had broken. It had 5 fuel tanks, a main and 2 each side. It transpires that instead of a single selector (Off-1-2-3-4-5), it had 4x (Off-L-R) selectors inline, making 81 possible combinations. I’m surprised they’re still flying.
Peter wrote:
The thing I don’t get, totaliser or not, is how can you possibly know where the fuel is, on a multi separate tank system, unless you let them go dry in turn.
You need to keep a fuel schedule and ideally use a similar worksheet as I recall them for the FE’s on large jets in ages past. In practice, you get a sheet with each tank listed separately (and possibly graphically) where you put the actual loaded fuel per tank down before start up. The totalizer needs to be manually set to the combined figure. Thereafter, every time you switch a tank you calculate and put down the fuel used from that tank (taken from the Fuel computer and crosschecked with the gauge) and substract it from the figure that tank had at the beginning. Then you do the next and next and next tank, which also allows you to balance the fuel system. It will get more complex where you manually transfer fuel from one tank to the other, but in general, you need to keep your bookkeeping and crosscheck it with the gauges in level flight.
A better way would be a means of being sure a tank is empty. Presumably that is how auto tank switching works; they detect some low level in the tank. The traditional GA fuel gauges are pretty useless.
Auto tank switching is quite a lot more complex but bases on the same principle. The manufacturer will give you a fuel schedule, with which you need to work. Which tank needs to used first, which 2nd and so on, what is the optimum CG and how do you have to transfer fuel from one tank to the next, e.t.c. Concorde was known for CG being moved by manual fuel transfer, Airbus has trim tanks in the tail which also get operated with the goal of arriving at an optimum CG. The difference is that airliners of today do all this automatically, while those who had complex systems did have a flight engineer.
You can run tanks dry but you need to be careful. Easiest is to keep your eyes on the fuel pressure gauge when you approach emty and switch at the first sign of the pressure dropping. That will leave a small quantity in the tank but is better than making your pax nervous with temporarily starved engines. Some manufacturers actually reommend running tanks dry.
Peter wrote:
The thing I don’t get, totaliser or not, is how can you possibly know where the fuel is, on a multi separate tank system, unless you let them go dry in turn.
Like Emir said in post #15 for the DA42 case. When there is enough room in the main tanks, you transfer all the fuel from the aux tanks into the main tanks. So in a sene you run the aux tanks dry by not by running the engine from them but by transferring them into the main tanks. It’s of course more difficult if you have an aircraft where you can’t transfer between tanks.
The thing I don’t get, totaliser or not, is how can you possibly know where the fuel is, on a multi separate tank system, unless you let them go dry in turn.
A better way would be a means of being sure a tank is empty. Presumably that is how auto tank switching works; they detect some low level in the tank. The traditional GA fuel gauges are pretty useless.
Pilot_DAR wrote:
As said earlier, understand the fuel system in the plane you’re flying, and use it as designed!
Absolutely, that is the key.
I am not sure how the fuel system in the C310 works, do you have a gauge for each tank? And how is the valve switching?
I’ve seen one system (not sure I believe on a Baron) where you had master fuel selector which had the main and aux position, then a 2ndary fuel selector which selected the actual aux and some additional tanks which (not sure anymore) emptied into the aux tanks. The fuel gauges had to be switched from one to another by a different selector and only showed the fuel of the selected tank. Personally I did not like the complexity very much.
I also remember a Setup in a Cessna 210 which had an additional baggage tank which needed transfer in flight into a specific tank. One one flight the fuel pump broke leaving the airplane out of fuel despite having some considerable amount on board.
You are very right about the fuel gauges. I have seen some Cessnas which had massively inaccurate gauges up to the point where it showed zero when there was more than 1/4 tank left… I am pretty happy with the fuel gauges in the Mooney however, in the C they work really well. In newer models you need separate gauges (on the wing) to see the fuel on ground vs in the air, as the airplane sits quite nose high and therefore the cockpit gauges won’t show correct unless in flight.
