I'd think if you're out of fuel -- just the unusable in the tanks,
chances of fire are pretty low. If I knew I wasn't going to get to an
airport (like my gauges are that accurate, right?) I would not fly to
fuel exhaustion then glide into the ground. I'd want enough fuel so if
I did break out or see the ground before impact I'd have enough power
to make a choice or two. If nothing else, I'd bring that sucker way
back on the power curve and drag it onto the dirt hanging on its prop.
That might buy me a few fewer knots of airspeed, and energy goes as
speed squared of course.

One could always have a tank spring a leak, of course, but a consistant
fuel management scheme can make fuel exhaustion a little less likely.
My fuel management checklist goes like this.

Before startup, switch to the less fuel tank.

Start up and start to taxi out on that tank. Now I'm pretty sure that
side is sweet.

Switch to the takeoff tank, finish the taxi out and run up on that one.
Now I'm pretty sure that tank is sweet too.

Take off, fly away a little less than half that fuel. Switch tanks. If
the new tank had become sour there should be enough left in the take
off tank to get me back to where I came from.

Otherwise, fly that tank to nearly empty.

Then, switch tanks, land and refuel, even if my destination is only 100
miles away. I'll always have at least 25% fuel on board.

The Mooney I used to own carried 33 gallons on each side, and could be
leaned to sip less than 10 GPH. I just described a 5 plus hour flight.
I'd been lucky enough to fly from LA to the northeast coast a couple of
times that way with just two en route fuel stops, going mostly at
11,000 feet and riding the wind. Adventures like that are best done
solo or with PX who know they have to moderate their water intake.
Ziplock bags are a poor substitute for on board toilet facilities! My
experience is most times the airplane has a LOT more endurance than the
PX (and sometimes, the PIC)!

Yeah, I know about keeping hydrated.

On Nov 12, 11:12 pm, "Kev" wrote:
Tony wrote:
I'd declare an emergency, ask for vectors for the lowest ground around
hoping the clouds wouldn't be on the deck there. I'd also want to have
the engine running when I got close to the ground, I may need some gas
to avoid something ugly and gliding at a few knots above stall might
not let me get above or around that tree.I seem to recall a study that said if you manage to glide for at least
45 seconds after shutting down your piston engine, then the cooling
reduces your chances of a post-crash fire by over 50%.

If true, then if you're low on fuel, your advice is good because you
have little to burn anyway. But if your motor is sputtering and the
plane is loaded with gas, it seems to argue that we should shut down
the engine as early as practical in hopes of avoiding a fire. Hard
choice!

Kev