Running dry?

Recently, Roy Smith posted:

"Neil Gould" wrote:
What FAR says you may not run a tank dry?

The FARs address minimum fuel levels when you arrive at your
destination.

I'm not aware of any such regulation. I suspect you're thinking of:

91.151 Fuel requirements for flight in VFR conditions.

[...]
But that only talks about how much fuel you have at takeoff, not at
landing.

You're (all) right; I was thinking of that FAR, and I stretched the point
too FAR. ;-)

I regularly fly something with two tanks and no "both" position
(PA28), and my preference is to arrive at my destination with more
than 30 minutes worth of fuel, period. I see no point in pushing
those limits any more than seeing how much over gross I can fly.
IMO, such points are just useless information. YMMV.

I also think landing with 30 minutes of fuel is too little. So, how
much is enough? Let's assume we can agree on an hour, which in a 180
HP PA-28 means about 8 gallons. You take off with 48 usable and fly
for 5 hours, leaving an estimated 8 gallons left. Which is a more
useful configuration to have at this point, an estimated 4 gallons
usable remaining in each tank, or an estimated 8 gallons usable in
one tank and the other one dry?

I would feel more comfortable with 4 in each tank than with a dry tank.

I had an interesting thing happen to me in an Archer. During an XC, a
facia screw on the fuel selector had worked loose and backed out enough
that when I went to switch tanks, it wouldn't go into that position. My
choices were the tank I was on, or off. I'm glad the tank I was on wasn't
dry, because when the A&P looked it over, it took him around 15 minutes to
figure out what was wrong. Needless to say, I wouldn't have figured that
out en route before hitting the ground, because I couldn't see the problem
from my seated position. Stuff happens.

Neil

"Neil Gould" wrote:

I also think landing with 30 minutes of fuel is too little. So, how
much is enough? Let's assume we can agree on an hour, which in a 180
HP PA-28 means about 8 gallons. You take off with 48 usable and fly
for 5 hours, leaving an estimated 8 gallons left. Which is a more
useful configuration to have at this point, an estimated 4 gallons
usable remaining in each tank, or an estimated 8 gallons usable in
one tank and the other one dry?

I would feel more comfortable with 4 in each tank than with a dry tank.

Let's examine that. We're comparing the relative risk of two events.

Event 1 is that the fuel selector valve fails when you go to switch to the
tank containing the remaining 8 gallons.

Event 2 is that your estimate of how much fuel is left in the tank is wrong
by 4 gallons (16%).

Which is more likely?

Recently, Roy Smith posted:

"Neil Gould" wrote:

I would feel more comfortable with 4 in each tank than with a dry
tank.

Let's examine that. We're comparing the relative risk of two events.

Event 1 is that the fuel selector valve fails when you go to switch
to the tank containing the remaining 8 gallons.

Event 2 is that your estimate of how much fuel is left in the tank is
wrong by 4 gallons (16%).

Which is more likely?

Talk about straw men! If the *only* risk in running a tank dry in flight
was the fuel selector valve failing -- probably the *least* likely thing
to happen -- there wouldn't be much point in this discussion, would there?
Yet, a variant on the "least likely thing to happen" happened to me in
flight. OTOH, my fuel consumption estimates have NEVER been off by 4
gallons (which is closer to between 20-25% in the planes that I fly, btw).
So, what can be concluded from this data? IMO, nada.

I recently read an article by a pilot that ferries aircraft between Hawaii
and Australia. Part of his prep was to test actual fuel flow in flight,
because the jump would necessitate reliance on the reserves. He didn't
mention doing it by running a tank dry in flight.

In the flying that I do, there is no direction that I can go where there
isn't fuel well within the range of the plane's fuel capacity without
considering reserves. So, I plan accordingly. You can fly however you
wish. I just see no point in unnecessarily pushing limits.

Regards,

Neil

Neil,

I would feel more comfortable with 4 in each tank than with a dry tank.


Well, I definitely wouldn't, the odd and very rare fuel selector
malfunction notwithstanding.

--
Thomas Borchert (EDDH)

In article ,
Thomas Borchert wrote:

Neil,

I would feel more comfortable with 4 in each tank than with a dry tank.


Well, I definitely wouldn't, the odd and very rare fuel selector
malfunction notwithstanding.


Nor would I! I would rather have an hour in ONE tank, rather than spread
among FOUR tanks! How would you know which tank to select for landing? I
would not want to select the 5 minute tank, when I would have to go
around!

Those are the guys who run into fuel starvation problems!