Self-launch takeoff performance from grass?

[Robert Davenport]

I'm interested in knowing if anyone has any direct experience with the
increase in take-off run when launching a self-launch glider on grass? I'm
specifically interested in the performance of the Russia AC-5M, but would
enjoy hearing from anyone with grass-strip experience in any type of
self-launch glider. Thanks in advance..

[Tom Seim]

"Robert Davenport" > wrote in message >...
> I'm interested in knowing if anyone has any direct experience with the
> increase in take-off run when launching a self-launch glider on grass? I'm
> specifically interested in the performance of the Russia AC-5M, but would
> enjoy hearing from anyone with grass-strip experience in any type of
> self-launch glider. Thanks in advance..

That's going to depend a lot on the condition of the grass, i.e. short
and dry or long and wet. My DG-400 POH recommends adding 10% for grass
strips. But if it is soggy and long I would consider 25% to be more
realistic. That said, it isn't going to make a lot of diffence (100
ft, or so) unless you are at high altitude on a shorter strip.

Tom

[Jeffrey Banks]

I take 1,200 ft ground roll on gravel. Density altitude aprox 2,000ft.
I estimate over a 50 ft obstacal around 2,500 ft. (Although I have not
tested or measured such a situation.)
AC5M
Alaska
Jeff Banks

[Steve Hill]

I operate a DG-400 almost exclusively off grass...my takeoff ground roll is
consistently between 700 and 800 feet, depending on wind, weight and density
altitude...the DG climbs out about 600 fpm. The most noticeable difference
between launching off grass vs. Hard surfaces, is how much quicker I can get
the wing up off the ground on hard surfaces...I never have a wing runner so
you learn to compensate. I generally start my takeoff runoff run with the
left wing down, and the nose slightly angled off the runway heading
generally to the left with the glider a bit off center to the right (
reverse if wind is reversed ) It is very easy to get the wing up in 50 to
100 feet, the big key is to keep the tail on the ground for the initial part
of the takeoff run ( steerable tailwheel on the DG-400 is a blessing) Once
the wings are level with good aileron control, raise the tail and accelerate
to rotation speed...I have watched the AC5m launch only once, and it didn't
look like any more trouble than my ship once the guy was in position to
launch...he did need help getting to that point, where the DG can just taxi
up and launch all by itself...Tom Seim is totally right in his assessment of
distance...when my runway is soft or muddy...the takeoff run easily exceeeds
1000 ft and you have to be very judicious in your use of adding power early
in the takeoff run being careful not to use so much power to nose over,
instead slowly letting the aircraft accelerate as the wings begin taking
weight off the wheel...it can be a balancing act some days...I have a few
times, had to abort a takeoff and move to higher/dryer ground due to the
high loading placed on the single main wheel when it is very soft and the
wheel actually sinks into the ground...( the joys of winter soaring) Not to
mention pull lots of mud mess out of the wheel well after a flight in those
conditions...at first, if I were you, I'd try to stick to firmer
grass...avoid soft muddy wet areas...and ENJOY!!!


Steve Hill
(sierra hotel)
DG-400