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