A small experiment

Robert Ehrlich wrote in message ...
Mike Borgelt wrote:

Would anyone like to carry out the following experiment?
Upon touchdown on a sealed runway, close the brakes, don't use the
wheel brake and see how far the glider rolls.

If I do that with any glider in my club, it will become airborne
again when I close the brakes.

Land slower?

Andy

Do you always touch down at excessive speed?

Robert Ehrlich wrote:
Mike Borgelt wrote:

Would anyone like to carry out the following experiment?
Upon touchdown on a sealed runway, close the brakes, don't use the
wheel brake and see how far the glider rolls.


If I do that with any glider in my club, it will become airborne
again when I close the brakes.

In article ,
says...
Do you always touch down at excessive speed?

I don't know about Robert's gliders, but all the ones I have flown
require more airspeed to stay up with the spoilers open (stall speed
about 3 to 4 knots higher) than with them closed. If I land with the
spoilers open, it will be at a higher speed than with them closed. For
this reason, and if the field is long enough, I try to land with the
spoilers closed during a field landing.

So, I think what Robert says is will happen, even for the best pilots.
The solution is to let the glider speed decay below the spoilers in
flying speed before closing them, or to land with them closed.

Robert Ehrlich wrote:
Mike Borgelt wrote:

Would anyone like to carry out the following experiment?
Upon touchdown on a sealed runway, close the brakes, don't use the
wheel brake and see how far the glider rolls.


If I do that with any glider in my club, it will become airborne
again when I close the brakes.



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Eric Greenwell USA

Eric Greenwell wrote:

...let the glider speed decay below the spoilers-in
flying speed before closing them, or to land with them closed.

Unless of course one reduces angle of attack while retracting spoilers,
or is that an advanced maneuver that should not be too widely discussed?



Jack

In article m, baron58
@sbcglobal.net says...
Eric Greenwell wrote:

...let the glider speed decay below the spoilers-in
flying speed before closing them, or to land with them closed.

Unless of course one reduces angle of attack while retracting spoilers,
or is that an advanced maneuver that should not be too widely discussed?

I think it is, because there is no point to closing the spoilers
completely immediately after a normal touchdown. The reason for doing so
in this case was to measure the drag while rolling after landing.

But to discuss your suggestion: I usually land on the main and the tail
wheel (or just the tailwheel), and keep the tail on the ground with back
stick. To reduce the angle of attack, I would have to raise the tail off
the ground. I haven't tried it purposely (I sometimes did it
inadvertently on my ASW 20 C when braking hard), since I haven't
encountered any situation where it would be of value, but I think it
could be done on most gliders.

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Eric Greenwell USA

Andy Durbin wrote:

Robert Ehrlich wrote in message ...
Mike Borgelt wrote:

Would anyone like to carry out the following experiment?
Upon touchdown on a sealed runway, close the brakes, don't use the
wheel brake and see how far the glider rolls.

If I do that with any glider in my club, it will become airborne
again when I close the brakes.

Land slower?

Andy

With open airbrakes, I can't land slower. With closed airbrakes,
it would take more than the 1km runway to decrease the speed
at the point the glider is no more airborne, if the approach
was done with the standard safety speed margin (stall speed plus
30%) and with half airbrakes.

Mike.

Ventus 2cxt.
aprox 450m ground roll.
Bitumen (11/29 x strip int to 29 threshold)
No brakes (wheel or air)(slight drag on wheel disk)
Nil wind.
Tip dragged for 20m

Mark R


--
justsoaring
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