I believe that some 172s only have 30deg of flaps availible. Full flaps
produce *some* additional lift even if there is a large drag increase. Keep
in mind that you are trading aerodynamic drag against the drag of the tires
in sand. On my airplanes MU-2 and Helio Courier minimium ground roll is a
function of weight, flaps and power availible.

In the Helio:

At normal density altitudes and light weights minimium ground roll is with
full flaps (40deg). This use of full flaps increases obstacle clearance
distance but reduces ground roll.

At some high density altitude and high weight the airplane won't climb out
of ground effect with full flaps without using a tremendous amount of
distance and a reduced flap setting is required.

The Helio is not that different from the 172 in terms of flaps. Both have
single slotted fowler flaps.

In the MU-2

Take off with flaps 20 uses less ground roll than flaps 5deg. Flaps 40deg
used even less distance but isn't used because the airplane becomes airborn
below Vmc and can't climb on one engine with flaps 40.

My guess is that a 172 at light weights and low density altitude will use
less runway with more than 10deg of flaps and the more powerful the engine
the more pronounced this difference. It would be interesting to see if the
new 172s have a full set of takeoff charts showing all altitudes, temps,
weights and flaps settings

Mike
MU-2


"David Rind" wrote in message
...
Mike Rapoport wrote:
Some flaps (maybe even full flaps) until airborn, accelerate in ground
effect and then climb. If you are interested in this stuff, read F.E.
Potts book on bush flying.

Mike
MU-2


"grubertm" wrote in message
oups.com...

So what's the best procedure for a sand strip, 4000AGL, 50ft obstacle ?
I can see the advantage of 10 deg. flaps for a mud strip, but I am not
sure whether the increased friction due to sand is worth the decrease
in climb rate..

- Marco

I haven't been following this thread that closely so I may have missed
something, but "full flaps"? I thought that once you got to 40 degrees of
flaps on a 172 you were just adding drag without any appreciable reduction
in stall speed. I can't see how that would get you into ground effect any
quicker....

--
David Rind