Decision making in ground roll

On 3/24/21 8:56 PM, ProfJ wrote:
Hi Folks,

There's a lot of focus at the moment on wing dropping during the
ground roll phase. I did my primary training on winch launches. For
those who have never winch launched, it's quite an experience being
in a 900 lb. vehicle which is accelerated by a 300hp motor which is
fixed to the ground and connected by a cable, i.e. no slip anywhere.
One of my co-trainees was a large and apparently fearless
professional rugby player; some time later he admitted to me that he
had kept his eyes tightly closed for his first half dozen launches.

As a way of dealing with the sensory overload of the first few
seconds of a winch launch, I used a protocol which was based on what
I could control. It went like this:

In the first second of roll, there is only one control which has any
authority, and that is the cable release. You have to release if the
glider jerks forward and overruns the cable. So, have a good grip on
the release and the only thing you have to think about in the first
second is, should I release? None of the other controls have any
effect at this speed, so don't think about them.

In the second second of roll, the rudder starts to have authority.
The initial jerk probably pulled the glider offline. So get back on
line. Given the yaw/roll coupling, this will probably help raise any
falling wingtip.

In the third second of roll, the elevator has authority. So raise
the tail (or nose, depending) and get balanced on the main wheel.

You might question, why control yaw then roll? Even with two wheels
on the ground, there is some yaw control, and the initial launch jerk
probably has the tail bobbing up and down anyway, so don't worry
about pitch yet. Get in line.

In the fourth second of roll, the ailerons finally have some
authority and you can level the wings. By that time, with a winch,
you're probably airborne anyway.

This was helpful to me because it gave a structure for dealing with a
very fluid and rapidly evolving situation.

The main reason for describing this, is that it requires you to have
a grip on the release and understand that it's a primary control
during ground roll; certainly the only one that works in the initial
roll.

Just my two cents...


I see others have provided feedback related to the "weak point" in your
logical - and IMO fundamentally sensible - reasoning. My knee-jerk
mental response to your logic was along the lines of: It's sensible in
basic theory, but likely "only minimally applicable" to most of the real
(winching) world.

It would take some combo of a weak
winch,"leisurely-winch-operator"/lacking-headwind to yield a
4-second-to-liftoff winch launch in my direct/observational
experience...writing as one whose first experience with a winch was a
1948, Buick straight-8-powered, old/tired when our paths crossed
baby...and *IT* easily, consistently, bettered 4-seconds-to-liftoff
launches of loaded 2-33s.

In any event, if your logical/linear reasoning worked for you - awesome!
Mebbe the problem lies in translating reality to words, I dunno. But
sensory-input overload is an inescapable hurdle teaching/experiencing
winch launching contains to be sure. There's no substitute for
experience...assuming a person survives it.

YMMV.

Bob W.