Michael Ash wrote:
J a c k wrote:
Ian wrote:

I am amazed that nobody seems to have come up with a really reliable
fuel gauge for light aircraft. I know it's a fairly small market, but
aviation prices are high: I'd have thought it would be worth
somebody's time.
Why? The flight manual and a stick, verified by experience, work very well.

Inaccurate gauges are not the cause of the problem.

Do you, or anyone else, schedule fuel stops for your car by taking its
average miles per gallon (or hours per gallon) and multiplying it by the
length of your trip, all the while ignoring that terrible imprecise fuel
guage? Personally I just drive around until the thing is around the red
area that says "you're getting close", then I stop for fuel. When I'm
going to go through an area where fuel is scarce, I will stop if the guage
is higher. Trying to calculate the fuel burn from first principles seems
like the sort of thing that's likely to leave me stranded in the mountains
with no gas. Why doesn't this work for aircraft? (He asks, as a glider
pilot with no power rating.)



I do _schedule_ auto fuel stops according to known fuel consumption
rates. Enroute, I ignore neither the fuel-related information
presentation nor factors known to affect consumption (or retention), so
that modifications to the basic plan can be made in the case of
unforeseen conditions mechanical or environmental. There is no
procedural difference between fuel planning in a boat, a car, nor an
aircraft. Some aspects of the process are more prominent in one mode
than in the others, but all are present in each.

The perfect fuel gauge would be a fine thing. When the market calls for
something better and is willing to pay for it, I'm sure Cessna, Piper,
and Beech will be able to supply improved systems. My contention is that
it is operator error which causes almost all fuel-starvation incidents.
Running out of gas causes a significant proportion of serious accidents
in light planes.

Fuel leaks are not a large part of the problem, but even an inaccurate
gauge can give warning of a fuel leak, if it is monitored as it should
be. There are also windows, in most cockpits. I have caught fuel leaks
visually twice, prior to entering the enroute phase of flight. Our tow
pilots do not _plan_ refueling according to the fuel gauge in the tow
plane. They do monitor the system, while planning for refueling based on
number of tows, with a substantial pad.

Pre-flight and in-flight planning, and total-system monitoring, would be
required anyway, _even if our fuel gauges were far more accurate than
they are._ To the extent it inspired misplaced confidence, the better
fuel gauge could lead pilots to ignore the other aspects of fuel
planning and monitoring which should be second nature to every power
pilot and are essential in every flight, whether terrestrial or
interplanetary.

An airliner's fuel quantity indicating system is relatively more
accurate and reliable, but even they malfunction. Large aircraft
normally have complex fuel systems consisting of multiple tanks,
multiple pumps, multiple routes for feeding from tanks to engines,
cross-feeding from tank to tank, etc., coupled of course with multiple
failure modes. All this complexity is accompanied by the appropriate
"gauges", indicators, and controls--some even automatic. Still, the
basics of planning and monitoring are essential.

Pilots have run out of gas in Cubs with a cork-float-and-wire fuel level
indicator mounted through the fuel cap directly in front of the pilot
and visible through the windscreen. Pilots have run out of gas in
aircraft with a wing-root located transparent tube visible in the
cockpit which allows the pilot to view the level of gas in the tank.
Better fuel gauges are welcome, but are not the solution to the problems
of fuel management.


Jack