ASW 20 SPIN CHARACTERISTICS

Bryan wrote:
Although George Thelen doesn't name the sailplane that is the subject of his
July 2004 Safety Corner column in Soaring magazine, he seems to be talking
about the ASW 20A. Perhaps someone familiar with that particular accident
could elaborate.

Yes, that was Ruben's fatal ASW-20A accident at Air Sailing.

Jeremy

(Chip Bearden) wrote in message . com...
There was some discussion about ten years ago that a contributing
factor in the early '20 accidents might have been the type of sealing
tape used on the flaps and ailerons. Specifically, before the
wholesale adoption of Mylar seals, many of the older ships had white
cloth tape on the lower surface that could bulge out at the hinge line
under certain airflow conditions, presumably triggering some sort of
undesirable behavior.

Anyone recall this or know if it was true?

Chip Bearden

Reply: Quite true. '20 is very sensitive to the quality of sealing on
both top and bottom of the wing. Remakable affect on both performance
and handling.
UH

Eric,

I don't recall if my A had a prohibition against spinning in landing
flap. However, to avoid overspeeding the flaps I would immediately
move the flap handle forward after the first half rotation. I had
assumed when I bought the glider that the upturned ailerons in landing
flap position would prevent dramatic autorotation, but this wasn't the
case. I think the 20 developed a bad reputation because pilots were
setting the landing flaps on downwind rather than waiting until final
approach. The 20 definitely handles less pleasantly, especially in
turns and turbulence with the landing flaps down.

With full flaps on the A, the nose angle at stall was below the
horizon. Just another thing to get used to.

I have to say I think George T. went a little overboard in
charcaterizing the 20 as a dangerous glider. Like all fast glass, it
requires additional energy management skills and a respect for the
altitude it will need to recover if abused. I see it as no less safe
or dangerous than a Discus. Perhaps more complex, but that's a
training issue. That's not nostalgia talking. I prefer newer
gliders... they are better harmonized, easier to put together, climb
and glide better. But the 20 (2nd gen) has the same management issues
as third generation flapped ships (V2, ASW-27) and newer gliders are
no less disposed to bite their masters if mishandled. There's nothing
inherent in the glider that would presdispose it to accidents. But
like all fast glass, it will accentuate pilot ignorance.

As for George's complaints against manual control hookups, well, this
is a fact of life. I would guess that 3/4 of all ships in service have
manual hookups. Again, a training issue. Pilots who follow the
manufactures' assembly instructions and best practices (double
inspection, critical assembly check, positive control check) don't
have problems. Control failures can almost always be traced back to
poor maintenance or a mistake in the assembly and inspection sequence.
There are some inherently poor designs, but the 20's hotellier
fittings are not among them. And after market safety devices are
available to address their known weaknesses (or more correctly,
weakness in the assembler). Are automatic control hookups better...?
You bet! But that doesn't make manual hookups inherently unsafe. They
simply require more attention.

JJ,

The 20's flaps and ailerons are split. They move differentially. The
ailerons alot, the flaps a little. They are flush with stick neutral
in fist positve, "0," and negative flap positions. And, of course, in
landing flaps, the ailerons go up causing the distinctive anhedral bow
on approach.

(Chip Bearden) wrote in message
.com...
. Specifically, before the wholesale adoption of Mylar seals, many of the
older ships had white cloth tape on the lower surface that could bulge out at
the hinge line under certain airflow conditions, presumably triggering some
sort of undesirable behavior.


Worse yet is that this cloth tape will shrink over time and can restrict
control surface travel. If you have not replaced your cloth tape in several
years you could have less travel than you should. You can of course pull or
push real hard to get to the stop but that is not a good thing to have to do.

Robert Mudd

It's true that many ASW20A's were/are sealed with cloth tape on the
underside of the flaps and sometimes the ailerons. It is needed for
the flaps because of the 55 degree (jesus)down flap setting for short
field landings. Mylar would just peel off when trying this flap
psoition during your control checks.

Mine is sealed with cloth tape and I intend to leave it on the
underside of the flaps. I have looked at how it is installed. It would
appear it was put on with full negative flap applied and even then a
small amount of "slack" has been left and pushed up into the gap by a
small amount. No matter what flap setting I use this "slack" always
stays up in the gap.

I would think it unlikely that cloth tape contributed to spinning
accidents. More likely poor energy management and/or the use of
landing flap before speed has been set and final turn complete.

Always complete your final turn, check your speed, make sure you are
going to make the field, check your speed, then select whichever
landing flap position you want, check your speed and use further
airbrake if required, continue checking you speed. Sorry if this seems
like teaching Granny to suck eggs.

Andy Henderson
ASW20FP


(Chip Bearden) wrote in message . com...
There was some discussion about ten years ago that a contributing
factor in the early '20 accidents might have been the type of sealing
tape used on the flaps and ailerons. Specifically, before the
wholesale adoption of Mylar seals, many of the older ships had white
cloth tape on the lower surface that could bulge out at the hinge line
under certain airflow conditions, presumably triggering some sort of
undesirable behavior.

Anyone recall this or know if it was true?

Chip Bearden

Andy Henderson wrote:
"Mylar would just peel off when trying this flap
psoition during your control checks."

Sorry, but I must disagree: my PIK 20B is sealed on the underside of the flaps with Mylar and Teflon, and they go down to 90 degrees! - the Mylar doesn't peel off, it works just fine if you put it on right. And if the grip of the mylar you have fitted to other places on the airframe is that tenuous you should be worried about it peeling.

Rgds,

Derrick Steed

Andy Henderson wrote:

It's true that many ASW20A's were/are sealed with cloth tape on the
underside of the flaps and sometimes the ailerons. It is needed for
the flaps because of the 55 degree (jesus)down flap setting for short
field landings. Mylar would just peel off when trying this flap
psoition during your control checks.

*Only* 55 degrees? We do 90 degrees in HP-Land. I use wide Scotch plastic
tape applied to the outside surface to seal. Yes, using mylar may be
feasible but it is very difficult to keep stuck in place on these ships.

Regards,

-Doug


Mine is sealed with cloth tape and I intend to leave it on the
underside of the flaps. I have looked at how it is installed. It would
appear it was put on with full negative flap applied and even then a
small amount of "slack" has been left and pushed up into the gap by a
small amount. No matter what flap setting I use this "slack" always
stays up in the gap.

Yup. Same here.

Good post Andy,
When the 20 first came out we had a rash of accidents, like 20 or more
world-wide. Then things settled down and the carnage stopped. Why? I have an
opinion, lots of guys climbed out of the 301 libelle and bought the hot new
toy. Think about the differences; The 301 had automatic elevator hook-up, the
20 didn't. Hence, a bunch of us forgot to hook things up. The 301 flaps only
went down about 15 degrees, the 20 flaps went way down. Hence a bunch of
landing accidents. On the 301, the stick only moved the ailerons, whereas in
the 20, everything out there moved and therefore a bit of heavy-handed input
could get one in trouble a whole lot faster. The 301 was nimble and quick, try
to be nimble and quick in your 20, with the flaps down, and one could end up
with rocks in the cockpit.
Why didn't we just stick with the good old 301 libelle?
JJ Sinclair

This comment is not quite on point - but relevant. I met a pilot yesterday
who flew B-26s during WWII. He mentioned that the B-26 had a reputation for
killing pilots during training. In particular, the pilots were afraid of an
engine out on takeoff causing a spin. Vice President Truman heard these
stories and considered the B-26 a financial waste, so he sent Jimmy
Doolittle down to test the characteristics of the plane.

Doolittle spoke with the pilots, read the operations manual, then flew the
airplane. He then assembled the cadets and brought along one of the
instructors as a check pilot. On the first takeoff, he pulled an engine,
then did a 360 degree turn and landed safely. On the next takeoff, he
pulled the other engine, then did a 360 and returned to land safely.

He then assembled the cadets and stated that he had flown the aircraft and
when the engine was shut down during takeoff, he flew it exactly like the
operations manual directed. His conclusion was that there was nothing wrong
with the airplane, but that the pilots had not been trained properly.

What is important is to understand the characteristics of the aircraft and
give great deference to the operations manual - unless you are smarter than
the guy who wrote it.

Colin


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