On 2005-06-14, Chris W wrote:
Isn't this 30 *minute* reserve rule for day VFR flight a bit odd? Here
are 2 examples to illustrate why I say that. In a J3 Cub you are going
to go just over 35 miles in those 30 minutes. In an RV-7, you can go
100 miles with that same 30 minutes reserve.
[snip]
need less than 1000 feet. Wouldn't a reserve rule that stated the
minimum distance you could fly in calm air be a better rule?

No, because it doesn't make sense. The fuel consumption in a plane
is not even strongly tied to distance, it's entirely tied to time in
the air. Since (as you point out) there are massive differences
between different aircraft, if you set out a reasonable minimum
fuel (based on calm air distance) for a Cub, it'd be entirely
unreasonable for a Piper Meridien or perhaps a Learjet (yes, they are
sometimes flown VFR, not often but it happens). If you set a distance
that's reasonable for a Piper Meridien, it'd be completely unreasonable
(and possibly out of the full fuel range) of a Pietenpol Aircamper. Or
in a strong wind (imagine the winds aloft are 40 knots, and you are
flying something like an Evans VP-1 which does about 55 knots on a good
day, you could plan a 100NM flight, run out of of fuel 20 miles from
your departure point, and based on a distance based reserve you were
entirely legal all along).

Basing the VFR minimum on *time* is far better, because then you get to
decide whether you meet minimum reserve based on actual conditions -
i.e. the plane you are flying and the wind conditions. Basing it on
distance would be silly.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"