Precision Landings and practice

William W. Plummer wrote:

Also, commercial glider pilots must be able to drop the plane between
two lines 100' appart.

Which is not that impressing when you consider that with those huge
airbrakes, you can adjust your glidepath to anything between 50:1 to 5:1.

This said, in our club we have the rule that "every landing is a spot
landing".

Stefan

"Stefan"
Also, commercial glider pilots must be able to drop the plane between
two lines 100' appart.

Which is not that impressing when you consider that with those huge
airbrakes, you can adjust your glidepath to anything between 50:1 to 5:1.

Airbrakes are far superior to flaps for glidepath control but I'm sure you
are exaggerating to make the point. Few gliders can achieve 50:1 and I'm
not sure about 5:1 either. But they are effective even if not huge.

But not always. I had the pleasure to do my initial training in a Schwiezer
2-22 where the difference in glide ratio with zero spoilers and full
spoilers was barely distinguishable (slight exaggeration). Side slips with
full spoilers were standard procedure. A nice training experience.

My first owned sailplane was the Finnish PIK20-b. A 70's vintage glass ship
with no spoilers. It had flaps that were infinitely adjustable between -8
and +90 degrees. Flaps can out perform spoilers in the sense that steep
descents can be achieved at slower speed. Problems include the need for
tight airspeed control to avoid balloning and float along with the fact that
flaps are effectively 'one way' devices, especially on gliders. Once you
roll in landing flaps and slow down, you really can't increase your glide
ratio by rolling them off. If you do retract the flaps to increase your
glide ratio, you generally have to increase your speed and/or let your
descent rate go up to regain some energy before the desired effect can be
achieved. With an engine, you can counteract that but in a glider all you
have is height and speed.

The PIK could be set down on a dime once the technique was learned. The
trick was to fly final with 90degs of flap and flare a foot or so off the
ground. Unless you entered the flare with a ridiculously low airspeed,
ground effect was sure to float you past any planned landing point. But
when you the desired point was reached, you simply dumped the flaps and
flared for a 2 pointer. However, the flaps were actuated with a crank that
required 2-3 full turns to dump. Imagine rubbing your tummy and patting
your head at the same time. It took a full season before I could detach the
cranking with my left hand from the smooth pulling with my right. Imagine a
bouncing ball..... But once mastered, you could land with a yard of any
intended point.

Maule Driver wrote:

Airbrakes are far superior to flaps for glidepath control but I'm sure you
are exaggerating to make the point. Few gliders can achieve 50:1 and I'm
not sure about 5:1 either.

Ok, I admit. So I'll reduce it to between 48:1 and 7:1. (48:1 being the
best glide for an LS8 with 18m, and JAR-22 requires a glide ratio of
less than 7:1 with airbrakes deployed.) Maybe I should even reduce the
upper limit to 45:1 for the bugs. :-)

I had the pleasure to do my initial training in a Schwiezer
2-22 where the difference in glide ratio with zero spoilers and full
spoilers was barely distinguishable (slight exaggeration).

The airbrakes of the Rhönlerche (aka Rhönstone) were called "noise
makers" because the only difference they made was the noise level. :-)
Slips were *very* effetive, however.

The PIK could be set down on a dime once the technique was learned.

Every airplane can be set down on a dime once the technique has been
learned (and is regularly practised!). Of course it may be more
difficult for some planes than for others.

But
when you the desired point was reached, you simply dumped the flaps and
flared for a 2 pointer.

Just smashing down the glider doesn't count. At least it doesn't at the
spot landing contests of our club. On the other hand, when outlanding,
the only thing which counts is the result and nobody will care about
style, of course.

Stefan

"Stefan"
The PIK could be set down on a dime once the technique was learned.

Every airplane can be set down on a dime once the technique has been
learned (and is regularly practised!). Of course it may be more
difficult for some planes than for others.

I'd have to agree but perhaps not all. A long wing ship I've heard about
that really doesn't spot land is the U2 (it was just hangar talk - can
anyone comment?)

when you the desired point was reached, you simply dumped the flaps and
flared for a 2 pointer.

Just smashing down the glider doesn't count. At least it doesn't at the
spot landing contests of our club. On the other hand, when outlanding,
the only thing which counts is the result and nobody will care about
style, of course.

This wasn't a smash down. Rather it resulted in a particularly smooth,
precise, and satisfying landing (once one learned to eliminate the PIOsfrom
cranking with one hand while controlling pitch with the other). Problem was
that the technique was not documented as far as I know. Just the technique
taught by one experienced PIK owner to another.

Otherwise I would submit that gliders that depend on flaps only for glide
path control *cannot* be consistently and safely landed 'on a dime' in the
normal range of conditions without the kind of non-standard technique
described above. The PIK couldn't and the Schweizer 1-35 couldn't in my
experience. And I think that fact that no one builds production gliders
with this configuration is a reflection of this. But my experience is
limited here.