Fuel contents gauging

[M61A1]

It depends upon the nature of the hypothetical system. A flowmeter depends upon a simple mechanical calibration, and it just counts pulses, so electronically it's stone-axe simple, and not particularly susceptible to interference. The main potential for inaccuracy is the miniaturisation of the impellers that is necessary to measure the small flows involved.The big jets use pressure refuelling from an underground hydrant system; the fuel truck for that system carries a reel of large-size hose and a large and very accurate flowmeter; it hooks into the nearest hydrant and the aircraft, and the operator zeros the meter and turns the tap on - just like any service station, but about five times the size. He gives the meter reading to the pilot, who enters it into his fuel log, and the aircraft uses its own flowmeters from then on. This is the reason the domestic airlines run a "hub-and spoke" pattern of operations. They can of course, use overwing refuelling if the airport is not equipped for pressure refuelling; but not if they can avoid it.

The fuel quantities are normally figured in weight units, but I'll let one of our ex-airline pilots speak on how that is figured from the volume - there are "standard" fuel densities that are required to be used for weight & balance calculations.

 

Some military types may have load cells built into their undercarriages, but I'm not aware of this system being generally used for fuel management.

 

For certification flight testing, it is not uncommon to weigh the aircraft, with the test crew aboard, before and after each flight.

I'm not aware of any military type with built in load cells, everything I've seen has capacitance probes and flow meters to engine feeds. Much the same as civvy world, the refueller pumps fuel in (usually in litres), then an aircraft total read off the gauges (usually pounds or kilos) and cross checked to make sure it's consistent, the figure is then entered into the aircraft documentation.

 

 

[Geoff13]

All this talk makes the Foxbat System look positively futuristic. Twin wing tanks. Very simple to dip and very accurate when dipping. Twin digital fuel guages which also seem to very very accurate and in line with what is actually in the tanks. So now fuel monitoring and a reliable engine that seems like two good reasons to stick with a Foxbat along with all the others.

 

It makes you wonder why, that when some can get it so right why others can get it so wrong. Dont get me wrong the fuel tap system on the Foxbat could easily catch out someone who is not used to it and although I have no problem with it I could think of several improvements that could be made.

 

Cheers Geoff13

 

 

[Dafydd Llewellyn]

All this talk makes the Foxbat System look positively futuristic. Twin wing tanks. Very simple to dip and very accurate when dipping. Twin digital fuel guages which also seem to very very accurate and in line with what is actually in the tanks. So now fuel monitoring and a reliable engine that seems like two good reasons to stick with a Foxbat along with all the others.It makes you wonder why, that when some can get it so right why others can get it so wrong. Dont get me wrong the fuel tap system on the Foxbat could easily catch out someone who is not used to it and although I have no problem with it I could think of several improvements that could be made.

 

Cheers Geoff13

Yep; the PA 28 was even better. There's no such thing as a "good" aeroplane - but some are worse than others . . .

 

 

[pmccarthy]

As a former PA28 driver now flying the FS Texan, I have not had to worry about this gauging problem. The Texan can be dipped quite reliably, the two tank gauges work reliably, and there is a low level lamp that comes on when the tank level falls to about 10 litres. But I still rely mainly on dipping and an adequate planning margin rather than the gauges.