Landing Flap Video

On Aug 2, 10:35*pm, Scott wrote:
As a noob to gliders (coming from powered airplanes), I always thought
that spoilers were "the bomb" * *One thing I like about spoilers over
flaps is that you can go from full spoilers to no spoilers instantly
without bad effects. *Can't do that with flaps...if you misjudge and put
on too much, too early, there isn't much you can do except
undershoot...

You can if you resist the temptation to fly slower than a safe no-flap
speed until you are very close to the ground and/or have the runway
"made". Use the flaps to approach steeper, not to approach slower.

When I was flying a Janus (which has something like a 20º landing flap
position I think), I sometimes practiced going smoothly but reasonably
quickly between no flap and landing flap without feeling a change in G
forces. This involved applying forward elevator at the same time as
increasing the flap setting, and backward elevator at the same time as
reducing the flap setting.

If you do this then you can safely remove flap on approach without any
"sagging", provided that you keep the speed above 50 knots or so. Some
people liked to float the Janus in with landing flap at under 45 knots
on dead calm days, and that's usually going to be ok, but I always
added another 5 knots for my wife and kids. You can get rid of it
quickly enough once you're below a height you don't mind falling from.

I have been flying a Calif (90 deg flaps + spoilers) for many years,
and I didn't had any problem going from 90 deg to 8 deg on very short
final (and the flaps actually go 90 to -12 to +8 durig this procedure)
something like 15m above ground. Doing so took 1-2 sec typically.
Although the Calif flaps are the most powerful I've ever seen (flaps
and spoiler amount to 15 sft perpendicular to the slipstream...), they
have the backdraw that youi change lift, drag and attitude at the same
time, which needs some training.
Today I fly a Ventus C with standard SH airbrakes, and I never had the
feeling that I should want more powerful airbrakes.

Btw, the distance of the ground run after touchdown has little to do
with flaps & airbrakes - it's a function of the spped at touch down,
and your gross weight.

Bert TW

Btw, the distance of the ground run after touchdown has little to do
with flaps & airbrakes - it's a function of the speed at touch down,
and your gross weight.


Ah, the potential fuzziness of free, condensed, advice!

While some of the above statement is absolutely correct, specifically the,
"...it's a function of the speed at touch down, and your gross weight" bit,
the, "Btw, the distance of the ground run after touchdown has little to do
with flaps & airbrakes..." lead-in may be just a tad misleading for readers
either lacking the specific engineering background, or, otherwise new to flaps.

Because the large-deflection landing flaps used on some sailplanes definitely
do increase lift, this gives Joe Interestedly-Capable Glider Pilot the
*option* of consequently touching down at a slower speed than would otherwise
be safely possible without the flaps' presence. Hence I disagree with the
lead-in statement, IF we presume Joe Glider Pilot is interested in learning
how to get the most (i.e. shortest) landing performance from the glider.

To this point, considering the lead-in video of this thread,I dare say few
gliders of any semi-modern ilk would be capable of touching down and rolling
to a halt, on a paved surface, in a(n ~)5-knot headwind in *only* 300' (twice,
so it might not have been pure luck!) withOUT using that flap-specific
advantage. Kinetic energy remaining after touchdown of a landing glider, after
all, is proportional to speed *squared*, while also being proportional to
touchdown weight (not squared).

Quibblingly,
Bob W.