Hands off thermalling

On 22 Apr 2004 11:16:50 -0700, (Andy Durbin)
wrote:

John Jones wrote in message ...
How many gliders can be trimmed for hands off thermalling?

An instructor showed me, with spoilers open and proper
trim, the glider will stabilize in a slow descending
turn. Claimed it was good for getting out of a cloud.

Neat, but would not want to thermal with the spoilers
open.

My ASW 19b and ASW 28 will thermal hands off for several turns. Only
works for smooth thermals not the more typical rowdy tight cores of a
strong Arizona day.

The full airbrake, hands and feet off controls, descent is known as
the benign spiral. Does not work in all gliders so try it before you
use it in a real descent emergency.

Indeed. I found out that the ASW-20 has a 20 second phugoid when
trimmed at 50 kts, clean at zero flap. I didn't notice the height
variation, but the speed excursion is +/- 5 kts and its stable - once
the phugoid is established in smooth air it doesn't increase or damp
out over about 10 cycles. I haven't tried other trim speeds and was
using my feet gently to stay straight, so I don't know if a spiral
would have developed or what happens at other trim settings

I must try the benign spiral next time I'm out with height to spare.
What sort of speed is recommended?

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :