Wing Drop, Aerotow vs Winch, Grass vs Pavement.

I suggest everyone have a look at this accident report from France.
It is significant and unusual, as a tow operation lead to a violent groundloop with the sailplane landing inverted, as in a classic and tragic winch accident.
The reason is most probably to be found in the strong headwind.
The accident started with a wing drop, and was irrecuperable within 3 seconds.
The French text shouldn't be a big issue, as the photographic sequence illustrates the event very well and is self-explanatory (especially if you look at the time stamp of each picture.

https://www.bea.aero/uploads/tx_elyd...f-dd140430.pdf

Safe flights,
Aldo Cernezzi
www.voloavela.it

On Monday, March 22, 2021 at 10:50:24 AM UTC-6, Aldo Cernezzi wrote:
I suggest everyone have a look at this accident report from France.
It is significant and unusual, as a tow operation lead to a violent groundloop with the sailplane landing inverted, as in a classic and tragic winch accident.
The reason is most probably to be found in the strong headwind.
The accident started with a wing drop, and was irrecuperable within 3 seconds.
The French text shouldn't be a big issue, as the photographic sequence illustrates the event very well and is self-explanatory (especially if you look at the time stamp of each picture.

https://www.bea.aero/uploads/tx_elyd...f-dd140430.pdf

Safe flights,
Aldo Cernezzi
www.voloavela.it

Very interesting and worth translating.
This data point would seem to indicate higher energy tows are a higher risk of having an issue wshould a wing drop occur. In this event it appear the strong headwind made it an even higher energy tow.
With that much headwind I would not have expected a wing drop as I would have expected to have good aileron and rudder control immediately. But as the report hints to, the combination of a gust and the prop wash may have overpowered the controls.

Thanks for posting.

Brian

On the winch, if the wing drops, release immediately, you don't have time to consider your options. There's a good chance you can't do it fast enough, and it's going to hurt.
The wing runner isn't going to do a lot of running, if they start you from a balanced position, (which might be slightly different than wings level), and your control inputs are neutral, you will have aileron control and flying speed very quickly after the "All Out" calls.

On Monday, 22 March 2021 at 20:03:39 UTC, Accounts Receivable wrote:
On the winch, if the wing drops, release immediately, you don't have time to consider your options. There's a good chance you can't do it fast enough, and it's going to hurt.
The wing runner isn't going to do a lot of running, if they start you from a balanced position, (which might be slightly different than wings level), and your control inputs are neutral, you will have aileron control and flying speed very quickly after the "All Out" calls.

At my club we try to emphasise that the wing runner should not allow the launch to start if there is a significant up or down force on the wingtip.

Someone mentioned water ballast - I think that is very significant, as a low wing allows water to flow towards the tip and make that wing heavier, making recovery less likely.

On Mon, 22 Mar 2021 17:41:30 -0700, waremark wrote:


At my club we try to emphasise that the wing runner should not allow the
launch to start if there is a significant up or down force on the
wingtip.

Same at my club. In addition, if there's a cross wind for a winch launch
and the pilot is using aileron to hold the downwind tip up rather than
leaving the stick central while the wing runner moves the tip up or down
to zero the force he's feeling, the wing runner is encouraged to stop the
launch until the stick is centralised.

This is safer because the pilot can't feel what the up- or down-force of
the wingtip is - only the wing runner knows that. And so, if the
balancing is left to the pilot, the chances of an immediate tip drop is
raised.

Someone mentioned water ballast - I think that is very significant, as a
low wing allows water to flow towards the tip and make that wing
heavier, making recovery less likely.

Agreed.


--
Martin | martin at
Gregorie | gregorie dot org

On Monday, March 22, 2021 at 6:57:59 PM UTC-6, Martin Gregorie wrote:
On Mon, 22 Mar 2021 17:41:30 -0700, waremark wrote:


At my club we try to emphasise that the wing runner should not allow the
launch to start if there is a significant up or down force on the
wingtip.

Same at my club. In addition, if there's a cross wind for a winch launch
and the pilot is using aileron to hold the downwind tip up rather than
leaving the stick central while the wing runner moves the tip up or down
to zero the force he's feeling, the wing runner is encouraged to stop the
launch until the stick is centralised.

This is safer because the pilot can't feel what the up- or down-force of
the wingtip is - only the wing runner knows that. And so, if the
balancing is left to the pilot, the chances of an immediate tip drop is
raised.
Someone mentioned water ballast - I think that is very significant, as a
low wing allows water to flow towards the tip and make that wing
heavier, making recovery less likely.

Agreed.


--
Martin | martin at
Gregorie | gregorie dot org

Good point about wing runners. What I teach wing runners is if the wing wants to go up, to let it go up as high as you can reach. If it goes low, let it go as low as is practical, as this will signal the pilot to put the correct input in to correct for wing low or wing high condition.

Brian

Not so much if the wing tanks are full and not interconnected.

Dan
5J

On 3/22/21 6:41 PM, waremark wrote:
Someone mentioned water ballast - I think that is very significant, as a low wing allows water to flow towards the tip and make that wing heavier, making recovery less likely.

On Tuesday, March 23, 2021 at 9:20:53 AM UTC-7, Dan Marotta wrote:
Not so much if the wing tanks are full and not interconnected.

Dan
5J
On 3/22/21 6:41 PM, waremark wrote:
Someone mentioned water ballast - I think that is very significant, as a low wing allows water to flow towards the tip and make that wing heavier, making recovery less likely.


I believe a nose tow hook reduces lateral excursions, but not all ! There was a Genesis-2 take off accident where the slack was not all taken out before starting tow. This resulted in glider pitching down on the nose wheel which is mounted on a 36� fiberglass shock strut which then sprung the nose up! It’s called the Hobby-horse effect which is annoying, but not all that dangerous, unless a wing tip touches the ground as the fuselage is pitching down. This can (and has) resulted in the glider cartwheeling and ended up inverted!
If you’d ship doesn’t have a nose tow hook I’d investigate having one installed!
Be safe out there and keep a hand on the tow release during takeoff!
JJ

On Tuesday, March 23, 2021 at 1:28:47 PM UTC-4, John Sinclair wrote:
I believe a nose tow hook reduces lateral excursions, but not all !

It's true that at the very beginning of the launch, the nose hook improves tracking. It's also true that once aerodynamic control is achieved that the rudder works better with a CG hook, and the rudder often (this is type dependent) works better for picking up a low wing than aileron input.

In all cases, the only thing that beats pilot skill is pilot judgement.

The release knob is the most under rated control in the cockpit.

T8