Stall spin during aero tow? Std cirrus

Have there been stall spins during an aero tow?

Today, I had a very scary aero retrieve. From being towed to fast to-to slow. Anyways the scaries part was when, the tow plane started to climb and to slow. The indicated speed on the glider was 50 knots and decreasing. The glider kept slowing down and sinking under the tow plane into the wake. By this time the glider felt extremely sloopy and it felt like it was ready to drop into stall. Fortunately as I felt the wing wanting to drop, the tug leveld some and got back to a decent speed.

Yes I did radio the pilot askig for 20 indicated more. And I was attempting to release when I hit the wake, but the release on the standard cirrus is far, and my extention had moved from my legs.

Btw std cirrus has a cg hook

On Sun, 5 Aug 2018 19:49:46 -0700 (PDT), wrote:

Have there been stall spins during an aero tow?

Today, I had a very scary aero retrieve. From being towed to fast to-to slow. Anyways the scaries
part was when, the tow plane started to climb and to slow. The indicated speed on the glider
was 50 knots and decreasing. The glider kept slowing down and sinking under the tow plane
into the wake. By this time the glider felt extremely sloopy and it felt like it was ready to drop
into stall. Fortunately as I felt the wing wanting to drop, the tug leveld some and got back to
a decent speed.

Yes I did radio the pilot askig for 20 indicated more. And I was attempting to release when
I hit the wake, but the release on the standard cirrus is far, and my extention had moved
from my legs.

If I understand your situation, what you describe is not unique to the
Standard Cirrus, but is a common experience when an aerotow gets too
slow, though most often experienced with a heavy ballasted glider.

The question usually comes out something like "I can fly my glider in
free flight at x knots (e.g., 40 kts), why does it feel difficult to
control and ready to stall at x+y knots (e.g. 50 kts)?"

This topic was widely discussed on r.a.s. in the 2010-2011 time frame.
The best explaination I saw came from Gary Osaba in his post on
1/1/2011.

To summize (Gary, sorry if I am not doing justice to your post) was
that the effect was due to the combination of the downwash (not the
prop wash!) aft of the towplane wing, combined with the fact that in
most cases, since the towplane has a shorter span than the sailplane,
the sailplane's outer wings (i.e, the ailerons) lie outside this
downwash field.

The impact of the downwash on the inner portions of the sailplane wing
is that the glider must be flown at a higher angle of attack than
would be experienced in normal free flight. To compound the issue, the
outer wing ailerons are not in this flow field, but in effect are in a
higher angle of attack than the inner wing. Essentially over-twisting
the outer portions of the wing (the exact opposite of what would
normally be done to prevent tip stalling and loss of aileron control).

The solution is obvious, the towplane must fly faster. This theory
only helps explain why the sailplane feels so close to loss of control
when on a tow comfortably above its free flight stall speed.

Anyone interested can do a search on Google's r.a.s archive using a
search term "poor lateral control on slow tow" (don't use the quotes
in the search, however).

https://groups.google.com/forum/#!searchin/rec.aviation.soaring/poor$20lateral$20control$20on$20slow$20tow

Hope this helps explain your experience.

Bob

I also experienced recently slow takeoffs in my fully ballasted 29 which felt very uncomfortable. The yaw string was all over the place often showing skidding. I am noticing it more in my 18m 29 than my 27, perhaps since the wing loading is higher, or due to more adverse yaw. Seems like 70 knots should be the minimum, preferably 75 knots.

Ramy

On Monday, August 6, 2018 at 12:10:19 AM UTC-5, Ramy wrote:
I also experienced recently slow takeoffs in my fully ballasted 29 which felt very uncomfortable. The yaw string was all over the place often showing skidding. I am noticing it more in my 18m 29 than my 27, perhaps since the wing loading is higher, or due to more adverse yaw. Seems like 70 knots should be the minimum, preferably 75 knots.

Ramy

From a glider pilot (who has BTDT) and a current towpilot - the answer is simple, if not always effective: ALWAYS establish comms with the tow pilot before the tow (satisfies the FAR requirement for a pilot to pilot briefing).. If you (or the tow plane) do not have working radios, get face to face with the tuggie and TELL HIM what speed to fly - that is YOUR responsibility..

Once on tow, if the tow starts to slow down - TELL HIM ON THE RADIO TO SPEED UP! That's why you have the darn thing! Then, if the tow continues to get dangerously slow (when you can't stay above the wake) and radio or wing rocks do not solve the problem, release (assuming you are high enough for a safe PTT) and get face to face with the tow pilot when he lands and explain the problem, nicely. Especially with tow pilots that are not also glider pilots, they REALLY may not understand what is going on at the back end of the rope!

Most tow pilots really want to give you a good tow, but feedback can be rare; take the time to debrief you tow pilot if anything unusual happens on tow, and when possible brief and practice emergencies on tow - visual signals (both glider and towplane), simulated tow plane engine failure, glider dive brakes open, etc. Makes the tow more interesting than just a drag around the local area waiting for 3000' AGL to appear on the clock...

Cheers,

66

On 8/6/2018 7:47 AM, kirk.stant wrote:
Big SnipÂ* Makes the tow more interesting than just a drag around the
local area waiting for 3000' AGL to appear on the clock...
Cheers,

66

As an active glider pilot and retired tow pilot, it always disappointed
me as the tuggie when the glider pilot would tell me he would get off at
3,000' AGL.Â* Then we'd proceed tow through super lift only to have him
release in sink at 3,000' AGL and practically beat me back to the
ground.Â* Just one of my pet peeves because the tuggie usually gets the
blame for the poor judgement of the glider pilot.Â* Get off in lift, not
at some predetermined altitude!
--
Dan, 5J

At 13:47 06 August 2018, kirk.stant wrote:
On Monday, August 6, 2018 at 12:10:19 AM UTC-5, Ramy wrote:
I also experienced recently slow takeoffs in my fully ballasted 29
which=
felt very uncomfortable. The yaw string was all over the place often
showi=
ng skidding. I am noticing it more in my 18m 29 than my 27, perhaps since
t=
he wing loading is higher, or due to more adverse yaw. Seems like 70
knots
=
should be the minimum, preferably 75 knots.=20
=20
Ramy

From a glider pilot (who has BTDT) and a current towpilot - the answer is
s=
imple, if not always effective: ALWAYS establish comms with the tow pilot
b=
efore the tow (satisfies the FAR requirement for a pilot to pilot
briefing)=
.. If you (or the tow plane) do not have working radios, get face to
face
w=
ith the tuggie and TELL HIM what speed to fly - that is YOUR
responsibility=
..

Once on tow, if the tow starts to slow down - TELL HIM ON THE RADIO TO
SPEE=
D UP! That's why you have the darn thing! Then, if the tow continues to
get=
dangerously slow (when you can't stay above the wake) and radio or wing
ro=
cks do not solve the problem, release (assuming you are high enough for a
s=
afe PTT) and get face to face with the tow pilot when he lands and
explain
=
the problem, nicely. Especially with tow pilots that are not also glider
pi=
lots, they REALLY may not understand what is going on at the back end of
th=
e rope!

Most tow pilots really want to give you a good tow, but feedback can be
rar=
e; take the time to debrief you tow pilot if anything unusual happens on
to=
w, and when possible brief and practice emergencies on tow - visual
signals=
(both glider and towplane), simulated tow plane engine failure, glider
div=
e brakes open, etc. Makes the tow more interesting than just a drag
around=
the local area waiting for 3000' AGL to appear on the clock...

Agree entirely about this. Talk to the tug pilot before you start.

I'm a new tuggie but have been gliding for 50 years. I want to give people
good tows. But if you don't let me know what you want then I won't feel
that bad if you don't get it.

Talking on the way up is all very well but we have to coordinate with the
tower before take off and it may take a while before I change back to the
gliding frequency.

It's sad how many people think that there's no need to talk to the tuggie.

Chris

It goes without saying that one must communicate their desired tow speed with the tow pilot (especially when faster than normal) and request more speed during the tow if necessary
That said, it is easier said than done at the high density altitude in the west, especially with non powerful tow planes. Releasing from tow is often not a good option when you just lifted off at the far end of the runway fully ballasted.

Ramy

On Sunday, August 5, 2018 at 10:49:48 PM UTC-4, wrote:
Have there been stall spins during an aero tow?

Today, I had a very scary aero retrieve. From being towed to fast to-to slow. Anyways the scaries part was when, the tow plane started to climb and to slow. The indicated speed on the glider was 50 knots and decreasing. The glider kept slowing down and sinking under the tow plane into the wake. By this time the glider felt extremely sloopy and it felt like it was ready to drop into stall. Fortunately as I felt the wing wanting to drop, the tug leveld some and got back to a decent speed.

Yes I did radio the pilot askig for 20 indicated more. And I was attempting to release when I hit the wake, but the release on the standard cirrus is far, and my extention had moved from my legs.

I had to release a couple of times last year; put the first down to new tow pilot. Second... hmmm. When the Pawnee did its annual, transponder (actually encoder) failed, and leak in pitot/static system and a subtly bent pitot tube were found to be responsible. The towplane speed looked good, mine, not so much in a Std class glider with the stick on the back stop, still sinking. When in doubt, release and debrief; multiple times, find what the problem is (I had checked my pitot/static system for leaks too). One problem inexperienced tow pilots cause without thinking is pulling up in lift to use the energy - while the glider is still in the sink surrounding...

On Monday, August 6, 2018 at 8:00:52 AM UTC-7, Dan Daly wrote:
On Sunday, August 5, 2018 at 10:49:48 PM UTC-4, wrote:
Have there been stall spins during an aero tow?

Today, I had a very scary aero retrieve. From being towed to fast to-to slow. Anyways the scaries part was when, the tow plane started to climb and to slow. The indicated speed on the glider was 50 knots and decreasing. The glider kept slowing down and sinking under the tow plane into the wake. By this time the glider felt extremely sloopy and it felt like it was ready to drop into stall. Fortunately as I felt the wing wanting to drop, the tug leveld some and got back to a decent speed.

Yes I did radio the pilot askig for 20 indicated more. And I was attempting to release when I hit the wake, but the release on the standard cirrus is far, and my extention had moved from my legs.

I had to release a couple of times last year; put the first down to new tow pilot. Second... hmmm. When the Pawnee did its annual, transponder (actually encoder) failed, and leak in pitot/static system and a subtly bent pitot tube were found to be responsible. The towplane speed looked good, mine, not so much in a Std class glider with the stick on the back stop, still sinking. When in doubt, release and debrief; multiple times, find what the problem is (I had checked my pitot/static system for leaks too). One problem inexperienced tow pilots cause without thinking is pulling up in lift to use the energy - while the glider is still in the sink surrounding...

A simple improvement, if not a fix:
If it feels sloppy on tow, put in another notch of positive flaps.
Jim