C172 Flaps up or 10 degrees for takeoff

"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..

How about -- unbolt the wings and hire a trailer. G

I would guess (low time pilot warning here, wait for someone else to
comment) that soft field takeoff would be the best bet here, except
climbing out at VX instead of VY after accelerating out of ground
effect. That way, you're not dealing with the friction of the sand for
as long.

Ben Hallert
PP-ASEL

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

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

David Rind wrote:

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....


He said maybe. Some aircraft do use full flaps for takeoff. The Cessna
does not. You want 20 degrees to break ground quickly, accelerate to 80
mph and milk the flaps up and then climb. If you have an obstacle then
you accelerate to 60 mph with the flaps down and keep it there and climb
above the obstacle. Once above the obstacle accelerate to 80 and get
the flaps up.

For which Cessna model is that procedure recommended? Certainly not
any version of the 172.

David Rind wrote:

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....

With an aircraft which has the ability to dump the flaps quickly (about anything
with a "Johnson bar"), you can get a remarkably short ground run by accelerating
with no flaps until just past the full flap stall speed. Drop the flaps down,
use a little elevator to yank it into ground effect, immediately put the yoke
forward to keep it a few feet above the runway, and milk the flaps up in ground
effect.

Obviously you aren't going to be able to drop the flaps that rapidly with a
172N, but the full-flaps stall speed is only 51 mph. Perhaps accelerating to
about 55 with the flaps down wouldn't incur much of a drag penalty?

Note that you *do* get a hefty drag penalty while the flaps are down, so your
distance to clear the traditional 50' obstacle is likely to be longer than a
normal takeoff.

It's a fun technique to try when there's no pucker factor involved. I used to
almost always spoil the effect by banging the tailwheel getting off the ground.

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.

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

"Mike Rapoport" wrote in message
nk.net...
I believe that some 172s only have 30deg of flaps availible.

Yes, P series only has 30°.


--
Hello, my name is Mike, and I am an airplane addict....

Mike

That's simple enough that every one should be able to understand.

John
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On Sat, 13 Aug 2005 04:05:57 GMT, "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
roups.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