Stall spin during aero tow? Std cirrus

A very comprehensive report, and a fair conclusion.

General comment, not totally related to this post.........
Most of our tug pilots are also glider pilots, tug pilot is sorta secondary.
We usually fly dry, but if we fly wet, we (glider pilot) instruct wing runner to flag tuggie that we are wet and need more speed.
I have flown out of our field heavy (ASW-20 a and c, thus 9lbs......) before with no issues.
Don't know if our field has EVER had a 2-32, I have flown a lot of ships, a 2-32 is not on the list.

Yes, a wee bit fast is better than a wee bit slow. I am a light pilot and have done XC tows from home to HHSC in a 1-26 (something like 120 air miles), yep, things got a wee bit too fast, but we were racing November weather to destination.

If you bend/break something, have a good reason when the FAA comes calling.
Hopefully you are around to chat with them.
Radios can fail or get stepped on.

Flapped ships have some options, but not unlimited.
Nonflapped have few options.
Time for go/no go is limited. When in doubt, bail out.

El domingo, 5 de agosto de 2018, 22:49:48 (UTC-4), escribió:
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 did several hours in my club's std cirry, and lot's of scarry tows on heavy turbulence... It was a Grob std cirrus, all flying tailplane, no winglets and CG hook. It was tail heavy due to a tail boom repair. Not the best combination at all, and get's worse if you have a tow at 2pm midsummer 35°C here in the Andes.

Remember that the glider stabilizes at different attitudes during tow because of the traction of the rope, so probably stall speed is different (maybe higher?) than in free flight. In this glider was obvious that the eccentricity of the CG hook affected heavily. The glider started to felt "uncomfortable" at 90 km/h, like trying to drop a wing.
Also, during aerotow in turbulence we experienced horizontal tail stalls if the towplane went below 100 km/h... full forward stick while the glider still pitching up and a buzz on the stick, reeaaally scary the first times. It recovered control if you centered a little the stick, which in this glider = lowering tail's AoA. Then we got used to go softer on the movements, even if you didn't follow the plane exactly, so no heavy changes on the tail's AoA are induced.
Of course, the glider flew much better when we started to add nose ballast to get the CG out of the back-limit region (it always flew in between the correct limits although).

Anyways, it was by far my favorite so far, a real joy to fly in the ridge. Still has a huge place in my heart.

By the other hand, i had a very similar event to yours, but in a Libelle (H301, flapped)...
Changed the tow plane that day from a 150 supercub to a Stearman, everything’s cool up to there. We were leaving the airstrip during takeoff at about 150~200 ft, and a little uncomfortably slow when suddenly i saw (and i swear it was scarry) the towplane's tail moving up and the plane abruptly changing it's attitude and climbing... first, there was no way to follow the plane in climbing, then i got into the massive rotor of the biplane and dropped a wing. Full opposite rudder and then dropped the other wing, again full rudder when the plane stabilized at a safer speed.
2 remarks:
- Towplane pilot had few hours on the plane and saw the speed way up while leaving the runway, so immediately tried to slow down. Then checked instruments and the plane marked higher IAS.
- when you get checked on a plane like a Stearman, you also need to get a master on radio com decoding... full throttle on that engine plus the wind hitting on your head & headphones, then its real challenging to understand radio talks. So, communication during aerotow is an issue. How can you tell the tow pilot to speed up, without having the risk of him understanding the opposite?

Francisco

I fly unflapped standard ships.
I used to fly a DG300 mainly dry. Tow in 110km/h range is not a problem.
This year I switch to a Discus 2. It has a big AoA also when on the ground and
it need about 130km/h dry to have and more speed when it is wet.

Both ship dry has the same weight and the almost the same surface. I think the main factor is the AoA. The differences are in the AoA and also in the tow hook position (baricentral for DG300 and on the nose for Discus 2) who main influence the stability on tow. When on tow we fly at relative low speed at high AoA fly in an uncommon attitude for the glider.

I always say my load and the desired speed at tow pilot befor take off.
ciao,
giovanni

At 18:35 23 August 2018, wrote:
I fly unflapped standard ships.
I used to fly a DG300 mainly dry. Tow in 110km/h range is not a
problem.
This year I switch to a Discus 2. It has a big AoA also when on the
ground
=
and
it need about 130km/h dry to have and more speed when it is wet.

Both ship dry has the same weight and the almost the same
surface. I think
=
the main factor is the AoA. The differences are in the AoA and also
in the
=
tow hook position (baricentral for DG300 and on the nose for
Discus 2) who
=
main influence the stability on tow. When on tow we fly at relative
low
spe=
ed at high AoA fly in an uncommon attitude for the glider.

I always say my load and the desired speed at tow pilot befor take
off.
ciao,
giovanni



The D-2 has an Angle Of Incidence (AOI) that corresponds to that of
flapped wing gliders. It came from 15m owners wanting to fly STD
Class competitions, and being allowed to do so with their flaps
locked at the zero setting. It was assumed that these 15 m birds
would be at a disadvantage in the climb because their airfoils were
not optimized to always be at the zero flap setting. It turned out
that the 15 m gliders did quite well in the STD Class, and were
noticeably better in the higher speed regimes due to their lower AOI
causing less (fuselage) drag. Centrair was the first to exploit this
with their Pegase, which is basically a "no flap" ASW-20. Anyway,
the D-2 has this lower AOI, so the visual sight picture from the
cockpit is somewhat more "nose high" at slower speeds than on
previous generation STD Class birds. It will fly just fine down into
the high 30 Kt range, but if you are on tow, the nose is so high by
then that you will have trouble seeing the tow plane. Take it from a
19 year D-2 owner. If the tow gets a little slow for your comfort,
just offset your tow position to the left side a bit. Then you will be
able to see the tow plane in the front right side of the canopy, AND
the tow pilot will thank you for doing it so that he/she doesn't have
to stand on the right rudder pedal so much...

RO

On Sunday, August 5, 2018 at 7:49:48 PM UTC-7, 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.


Slight topic creep: As a tow-pilot I always give more speed on tow when requested, but I've also had a complaint later that the climb-rate was very slow. My impression is that Pawnees are very draggy and rate of climb suffers noticeably with extra speed. I've only towed in turbulent air, so can't give any measurements.

To me, this is a "formation flight". If both are "sorta middle of the road", normal may be fine.
Something different (time of glider pilot, turbulence, heavy weight), thou shalt communicate what you want and/or can do!
It behooves BOTH pilots!

Loading a glider to 10-11lbs when the site is used to 6lbs, something needs to change!

Just my take.

I fly rather light wing loading gliders (1-26 SN 002, I weigh about 150lbs) to wet 15M glass full of water (9+lbs) and communicate to the towpilot.
You're BOTH PIC in your craft!
You do right by you!

Say, high altitude density for the tug and a heavy glider.
Glider pilot wants "X" but tug pilot states "no way", wait for another tug, or drop weight.
Don't assume!

We have enough statistics, no need for more, especially if they are avoidable.

On Monday, August 27, 2018 at 6:35:25 AM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:
To me, this is a "formation flight". If both are "sorta middle of the road", normal may be fine.
Something different (time of glider pilot, turbulence, heavy weight), thou shalt communicate what you want and/or can do!
It behooves BOTH pilots!

Loading a glider to 10-11lbs when the site is used to 6lbs, something needs to change!

Just my take.

I fly rather light wing loading gliders (1-26 SN 002, I weigh about 150lbs) to wet 15M glass full of water (9+lbs) and communicate to the towpilot.
You're BOTH PIC in your craft!
You do right by you!

Say, high altitude density for the tug and a heavy glider.
Glider pilot wants "X" but tug pilot states "no way", wait for another tug, or drop weight.
Don't assume!

We have enough statistics, no need for more, especially if they are avoidable.

Just to point out some places do not have comms between glider and tow. Just signals.

On Monday, August 27, 2018 at 9:03:17 AM UTC-6, Jonathan St. Cloud wrote:

Just to point out some places do not have comms between glider and tow. Just signals.

That's when a face-to-face conversation about what you want/need prior to launch is key.

On Monday, August 27, 2018 at 10:03:17 AM UTC-5, Jonathan St. Cloud wrote:

Just to point out some places do not have comms between glider and tow. Just signals.

Yeah, cuz radios are so, like, expensive and hard to use!

Tow planes without radios (and transponders and soon, ADS-B out) are dangerous, IMO. And there really is NO excuse not to have some kind of radio in every glider.

Our club is getting there, slowly. Unfortunately our most commonly used trainer is a Blanik L-13AC, and our A&Ps can't find a legal way to put a battery in it.

Kirk