Overspeeding on winch launches

On Mon, 06 Nov 2017 05:25:52 -0800, Tango Whisky wrote:

Le lundi 6 novembre 2017 13:48:16 UTC+1, Dan Schmitz a écritÂ*:
I'm wondering what the consequences of overspeeding on winch launches
are? I understand that it places stress on the airframe, but to what
extent?

I find it near impossible to control the airspeed on the top third of a
launch and have found myself over speeding the placarded max. speed by
5 - 10 knots a few times despite signalling to the winch driver.

Should I be taking the approach of releasing at 2/3 of typical launch
height (e.g. 700 - 800 foot) if my airspeed isn't under control at this
point?

Thanks in advance

If you are overspeeding on winch launch, ease the stick forward as
needed to stay in the flight enveloppe. If this doesn't help, release
and talk to the winch driver when back on the ground.

If you are overspeeding while flying a high angle of attack, remember
that the whole load generated by the winch is fed via the fuselage into
the wing (and you won't feel a thing unlike while pulling g's in free
flight). If you have a weak ling popping at say 1000 daN, that is like
you had added 1000 kg to the weight of your fuselage. If you fuselage
weights 200 kg, adding 1000 kg translates to a "g-load" of 6 g.

What Tango Whisky says.

Quite a high degree of overspeed (5-10 kts) is acceptable in the first
half of the launch because most of the cable tension is pulling you
forward rather than down, but above that point, i.e. when the climb
starts to flatten, you should release immediately if you're even slightly
above the placarded max winch speed.

The ideal launch speed for most single seaters is about 5 kts[*] below
the placarded max: you get almost as high and the launch feels nicer and
a bit more controllable.

[*] Vwinch for an ASK-21 is 80 kts, but we virtually never exceed 70kts
on the winch with out club gliders - there's simply no need to launch
them that hard.

My H.201 Libelle has a Vwinch of 65 kts, which I strictly observe
in the top half of the climb and almost never exceed below that, but
it definitely feels a lot nicer at 60kts. That speed reduction costs
me no more than 100 ft. We normally place the winch 1200m (4000ft)
from the launch point and I expect to get 1300-1400 ft in typical
wind conditions.


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martin@ | Martin Gregorie
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