Overspeeding on winch launches

[Dan Schmitz]

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

[Martin Gregorie[_5_]]

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.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Scott Williams]

On Monday, November 6, 2017 at 6:48:16 AM UTC-6, Dan Schmitz wrote:
> 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
When our club was winching fairly often, I was one of the winch drivers (with only a 3-4 hundred runs though). As the glider begins to reach the last third of the launch, the power must back off, sometimes to barely above idle. this is especially true if launching into a good brisk headwind.

[[email protected]]

Q: "I understand that it places stress on the airframe, but to what extent"
A: Up to the breaking strength of the weak link. Max ground launch speed is there to protect the weak link not the glider.

[George Haeh]

https://members.gliding.co.uk/bga-safety-management/safe-winching/

The BGA has published a an excellent winch launching resource.

Well worth memorizing at the beginning of every season.

The winch driver should be reducing power at the top of the launch as this
is
where overspeed becomes critical.

Do remember to have a correct weak link.

I managed to break one just as I was releasing. Gusts and transmission
surging
can add loads. That is what the weak link protects against. The
manufacturer
airspeed limit gives some margin for gusts; so yes, on a calm day a small
airspeed exceedence might not break the weak link. But don't make it a
habit.

We qualify in a 2-seater, but a single seater handles differently. The
winch
generally has to run at the max for a 2-seater, but has excess power for a
single
seater.

Tension can go up or down a few hundred pounds in very few seconds because

of gusts.

[Tony[_5_]]

That statement is not true when ground launching gliders certified under the old Glider Criteria Handbook in the USA. In that case the ground launch limit is a structural limit!

[Tango Whisky]

Well, you've got that wrong.

[waremark]

I don't agree with:

", i.e. when the climb
starts to flatten, you should release immediately if you're even slightly
above the placarded max winch speed. "

I do agree of course that exceeding the placarded limit is not a problem earlier in the launch when the cable is pulling the glider more forward than down, but that the load on the glider (and the weak link) is more critical towards the end of the launch. However, rather than releasing, I think that safety (and not breaking the weak link) can be achieved by relaxing the back pressure.

The correct weak link should prevent any glider from suffering structural failure, and probably does. But has anyone ever heard of any accident caused by exceeding a placarded maximum launch speed?

[Martin Gregorie[_5_]]

On Mon, 06 Nov 2017 16:33:03 -0800, waremark wrote:

> The correct weak link should prevent any glider from suffering
> structural failure, and probably does. But has anyone ever heard of any
> accident caused by exceeding a placarded maximum launch speed?
>
Not that I've heard of, but that's pretty much a direct quote from any of
the instructors at GRL - especially w.r.t. the Puchacz.

I tend to apply it pretty rigidly to my Libelle because she's an old
lady, 48 this year, and I feel that I should be kind to her.

Actually, Libelles would appear to have a better protection than the weak
link: I was at Eden Soaring at the end of September, where pole-bending
is pretty much de rigeur thanks to a somewhat short field (940m winch to
launchpoint) and the need to get to the hill, 2.5 km away, at least 900ft
above the airfield, so you hear words from the instructor if you're
climbing out at less than 45 degrees during a site check in their K13.
Anyway, I soon found out that doing the same in my Libelle tends to back
release a little before I'd normally pull the bung and certainly before
the weak link went. They have good winch drivers: good brisk acceleration
at the start and spot on 65 kts in the top half of the launch.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Jonathon May]

At 00:33 07 November 2017, waremark wrote:
>I don't agree with:
>
>", i.e. when the climb=20
>starts to flatten, you should release immediately if you're even
slightly=
>=20
>above the placarded max winch speed. "
>
>I do agree of course that exceeding the placarded limit is not a
problem
>ea=
>rlier in the launch when the cable is pulling the glider more
forward than
>=
>down, but that the load on the glider (and the weak link) is more
critical
>=
>towards the end of the launch. However, rather than releasing, I
think
>that=
> safety (and not breaking the weak link) can be achieved by
relaxing the
>ba=
>ck pressure.
>
>The correct weak link should prevent any glider from suffering
structural
>f=
>ailure, and probably does. But has anyone ever heard of any
accident
>caused=
> by exceeding a placarded maximum launch speed?

I watched a fatal winch launch accident happen ,and it still haunts
me.
The climb was not steep but the pilot got into a PIO while trying to
sort it out .1 wing broke off near the root and it came down
side ways.
There were structural faults in the glider wing and the weak link was
doubled,BUT the experienced winch driver said there was little load
on the cable.
We put it down to the change in angle of attack at high speed, the
load hits the wing first, then the hook, it is not until all the bow is
taken from the cable that the load it on the weak link and the driver
feels it.
max winch means max.
However I have not let it stop me, but I never have full back stick at
near max winch speed and I try to be smooth .
Jon May
>

[Peter Whitehead]

On Monday, 6 November 2017 12:48:16 UTC, Dan Schmitz wrote:
> 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

Dan, my response is "yes".

The physics suggest that there is substantially greater risk to the airframe (and you) over 1/2 way up the launch, and even more as it progresses (with little risk below half-launch situation) because of increasing resolved forces acting 'downwards' (relative to the glider). Yes the weak link should provide protection - BUT are you sure the weak link is the correct one? Is your airframe perfect (in manufacture, later storage, repair, infestation, rot, corrosion, etc )?
Fortunately we have not seen many situations where the structure has failed through over-speeding. We have seen more damage and death with too low airspeeds or failed launches. A little off this particular thread but please may I reiterate the advice that we should all take a (repeated) look at the BGA advice, arrived at through a proper scientific analyisis to the 'BGA safe winch launching initiative' to reduce accidents (proven to help). The basic advice is at
https://members.gliding.co.uk/wp-content/uploads/sites/3/2015/04/1430311979_HowToWinchSafely_Part1.mp4
The whole programme is at
https://members.gliding.co.uk/bga-safety-management/safe-winching/

Pete.

[Dan Schmitz]

Thanks everyone for your feedback. My take aways from this are:

1. Speak with the winch driver. I've had fast launches a few times with no reduction in power when signalling.
2. Get the airspeed under control early in the launch.
3. Release early if over speeding past the first 1/2 of the launch.
4. Smooth control inputs and don't give full up elevator towards the top of the launch if over speeding.

Thanks,

Dan

[Dave Walsh]

Having a little engine I don't winch launch but reading through
the earlier posts it sounds like little has changed in 40 years:
why, in the 21st Century, don't the pilot and winch driver
communicate by radio? Surely all this waggling the wings
about stuff should long ago have been scrapped?

[Mike Hendron]

I would repeat what Scott said above as well. I've done quite a few launches as driver on our winch here at Utah Soaring, and we are always back to 1/3 or 1/4 throttle as the climb rate begins to slow and the glider begins to arc over at the top, and sometimes get all the way to idle by the time the back release engages. The less tension on the line the better the back release works, at least on our Astir.

I assume "signaling" is done by radio? If not, that seems to be a "weak link" in the process chain, as Dave suggests.

Mike

[Martin Gregorie[_5_]]

On Tue, 07 Nov 2017 09:00:58 -0800, Mike Hendron wrote:

> I would repeat what Scott said above as well. I've done quite a few
> launches as driver on our winch here at Utah Soaring, and we are always
> back to 1/3 or 1/4 throttle as the climb rate begins to slow and the
> glider begins to arc over at the top, and sometimes get all the way to
> idle by the time the back release engages. The less tension on the line
> the better the back release works, at least on our Astir.
>
> I assume "signaling" is done by radio? If not, that seems to be a "weak
> link" in the process chain, as Dave suggests.
>
Where I fly, glider-winch signalling is visible: lower the nose of the
launch is too slow and use the rudder to wave your tail at the winch if
its too fast.

Our duty launch marshal uses radio, rather than lights, to pass glider
details to the winch driver and to manage the launch, but that doesn't
use an airband frequency and we do not have an airband radio in the
winch.

Our airband frequency is used for glider-tug, glider-glider comms and for
blind calls as we join the circuit. The launch marshal has an airband
receiver to help him maintain situational awareness, but he is primarily
concerned with managing winch launching and co-ordinating launches with
aerotow operations. On a typical day winch launches considerably
outnumber aero tows.

I know that at least one Scandinavian club experimented with using radio
telemetry to display the glider's airspeed to the winch driver, but I
don't know if they still use it or what their conclusions about its
benefits were.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[David Salmon[_3_]]

At 17:28 06 November 2017, George Haeh wrote:
>https://members.gliding.co.uk/bga-safety-management/safe-winching/
>
>The BGA has published a an excellent winch launching resource.
>
>Well worth memorizing at the beginning of every season.
>
>The winch driver should be reducing power at the top of the launch as thi
>is
>where overspeed becomes critical.
>
>Do remember to have a correct weak link.
>
>I managed to break one just as I was releasing. Gusts and transmissio
>surging
>can add loads. That is what the weak link protects against. Th
>manufacturer
>airspeed limit gives some margin for gusts; so yes, on a calm day a small

>airspeed exceedence might not break the weak link. But don't make it
>habit.
>
>We qualify in a 2-seater, but a single seater handles differently. Th
>winch
>generally has to run at the max for a 2-seater, but has excess power for
>single
>seater.
>
>Tension can go up or down a few hundred pounds in very few seconds becaus
>
>of gusts.
>
>You can always invest in a Launch Assistant from Skylaunch. An ASI
transmitter in the glider, and a receiver/readout in the winch. Not that
expensive, and doesn't have to be a Skylaunch winch.
Dave
>
>
>

[David Salmon[_3_]]

At 11:22 07 November 2017, Peter Whitehead wrote:
>On Monday, 6 November 2017 12:48:16 UTC, Dan Schmitz wrote:
>> 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?
>>=20
>> I find it near impossible to control the airspeed on the top third of a
>l=
>aunch and have found myself over speeding the placarded max. speed by 5 -
>1=
>0 knots a few times despite signalling to the winch driver.
>>=20
>> Should I be taking the approach of releasing at 2/3 of typical launch
>hei=
>ght (e.g. 700 - 800 foot) if my airspeed isn't under control at this
point?
>>=20
>> Thanks in advance
>
>Dan, my response is "yes".
>
>The physics suggest that there is substantially greater risk to the
>airfram=
>e (and you) over 1/2 way up the launch, and even more as it progresses
>(wit=
>h little risk below half-launch situation) because of increasing resolved
>f=
>orces acting 'downwards' (relative to the glider). Yes the weak link
>should=
> provide protection - BUT are you sure the weak link is the correct one?
>Is=
> your airframe perfect (in manufacture, later storage, repair,
>infestation,=
> rot, corrosion, etc )?=20
>Fortunately we have not seen many situations where the structure has
>failed=
> through over-speeding. We have seen more damage and death with too low
>air=
>speeds or failed launches. A little off this particular thread but please
>m=
>ay I reiterate the advice that we should all take a (repeated) look at
the
>=
>BGA advice, arrived at through a proper scientific analyisis to the 'BGA
>sa=
>fe winch launching initiative' to reduce accidents (proven to help). The
>ba=
>sic advice is at=20
>https://members.gliding.co.uk/wp-content/uploads/sites/3/2015/04/1430311979=
>_HowToWinchSafely_Part1.mp4
>The whole programme is at=20
>https://members.gliding.co.uk/bga-safety-management/safe-winching/
>
>Pete.

There is another aspect to this, which unfortunately cannot be evaluated.
My understanding from a BGA Technical Officer a long time ago, was that the
designer does not calculate the maximum speed that the specified gust load
can be withstood safely, but rather decides on a speed, and then does the
calculation to show that that speed is safe. We don't know, but it may well
be safe at a much higher speed. Some years ago the BGA National Coach tried
to get the Puchacz max winch speed increased above 59 kts. This gives a
very narrow window when you don't really want to be below 55 kts in the
full climb.
Dave

[AS]

On Monday, November 6, 2017 at 1:48:16 PM UTC+1, Dan Schmitz wrote:
> 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

Dan - if you are overspeeding in the last third of the launch, your winch driver is inept and needs some supplemental training! He needs to back off the power much more when launching a light single seat glider compared to a heavy K21 or TwinAstir. Ideally, the winch operator retards the engine to the point where the glider over-flies the line and executes a very soft back-release.

Uli
Winchmeister, Carolina Soaring Assoc.

[Martin Gregorie[_5_]]

On Tue, 07 Nov 2017 18:15:23 +0000, David Salmon wrote:

>You can always invest in a Launch Assistant from Skylaunch. An ASI
> transmitter in the glider, and a receiver/readout in the winch. Not that
> expensive, and doesn't have to be a Skylaunch winch.
> Dave
>
So I see. That answers all my questions about size/weight/how it is
installed in the glider. Thanks.



--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[David Salmon[_3_]]

At 20:56 07 November 2017, Martin Gregorie wrote:
>On Tue, 07 Nov 2017 18:15:23 +0000, David Salmon wrote:
>
>>You can always invest in a Launch Assistant from Skylaunch. An ASI
>> transmitter in the glider, and a receiver/readout in the winch. Not
that
>> expensive, and doesn't have to be a Skylaunch winch.
>> Dave
>>
>So I see. That answers all my questions about size/weight/how it is
>installed in the glider. Thanks.
>
>
>
>--
>martin@ | Martin Gregorie
>gregorie. | Essex, UK
>org |
>
It is a small lightweight plastic box, from memory around 75x25x10. Needs
tee-ing in to the pitot and static lines, and also needs a 12v supply. So
light, it could be velcro'd under the panel, or tie wrapped. It detects the
start of the launch, at around 25kts, then transmits the airspeed to the
receiving unit in the winch, which has an analogue airspeed readout, then
after the launch, switches itself off. Check out the Skylaunch web site.
Dave

[DG300PI]

Also electric winchlaunch is getting more common (at least in w. europe)
The cable tension is controlled by the automation of the winch, which leads to a considarable reduction of weak-link breakage and adds to a more safer winch operation.

Eric

[Peter Whitehead]

I am going to purchase the kit for our expedition winch and auto-tow outfit, and one for my glider. A small price for higher and safer launches, compared to what we spend on 'gizmos'. I have no connection with Skylaunch though they have always provided great service and everything I have needed in terms of launching accessories.
The 'wheel has been invented'. We don't need to anguish over the question - "should I pull off before my wings are pulled off?"!

[Martin Gregorie[_5_]]

On Thu, 09 Nov 2017 22:43:07 -0800, Peter Whitehead wrote:

> I am going to purchase the kit for our expedition winch and auto-tow
> outfit, and one for my glider. A small price for higher and safer
> launches, compared to what we spend on 'gizmos'. I have no connection
> with Skylaunch though they have always provided great service and
> everything I have needed in terms of launching accessories.
> The 'wheel has been invented'. We don't need to anguish over the
> question - "should I pull off before my wings are pulled off?"!

To me this looks like a great idea if almost every winch has it, but
otherwise a slight worry that it may affect my proficiency if my home
winch is equipped with it but winches at clubs I visit don't have it.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[john firth]

On Monday, November 6, 2017 at 7:48:16 AM UTC-5, Dan Schmitz wrote:
> 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

I have seen a cable tension display in a modern winch in the UK.
It showed the proper tension for each glider type. It would seem to be the
right way to optimise the launch.

John F.

[Martin Gregorie[_5_]]

On Fri, 10 Nov 2017 14:46:00 -0800, john firth wrote:

> On Monday, November 6, 2017 at 7:48:16 AM UTC-5, Dan Schmitz wrote:
>> 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
>
> I have seen a cable tension display in a modern winch in the UK.
> It showed the proper tension for each glider type. It would seem to be
> the right way to optimise the launch.
>
All Skylaunch winches have a sort of analoge computer: you input the
glider type and windspeed (our winches have an anemometer on the roof)
and that sets a stop at the optimal speed. The driver is still responsable
for initial acceleration and can, IIRC, override the stop, but it
generally gives a pretty consistent launch.

They'll also rebuild almost any other winch (we, CGC, have a Skylaunch
and a Tost they rebuilt) or supply a kit for clubs that want to do their
own work, but they can all have the analogue computer thingy installed.

The glider ASI telemetry is an optional extra that lets the wings driver
see the glider's actual airspeed.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |