Life glider hours with winch

[[email protected]]

Hi all.

I listened from some pilots that the glider life hours reduce if you use winch start.

Is that true? I looked for some data about and I did not found.

have a nice day, José.

[Eric Munk]

At 17:14 21 March 2019, wrote:
>Hi all.
>
>I listened from some pilots that the glider life hours reduce if you
use
>wi=
>nch start.
>
>Is that true? I looked for some data about and I did not found.
>
>have a nice day, Jos=C3=A9.
>

I know this is true for the Blanik and maybe other dural gliders.
Certainly not any GFRP or wooden types.

[Eric Munk]

At 17:14 21 March 2019, wrote:
>Hi all.
>
>I listened from some pilots that the glider life hours reduce if you
use
>wi=
>nch start.
>
>Is that true? I looked for some data about and I did not found.
>
>have a nice day, Jos=C3=A9.
>

Blanik, yes. Other dural gliders maybe. Others don’t think so.

[Eric Munk]

At 17:14 21 March 2019, wrote:
>Hi all.
>
>I listened from some pilots that the glider life hours reduce if you
use
>wi=
>nch start.
>
>Is that true? I looked for some data about and I did not found.
>
>have a nice day, Jos=C3=A9.
>

Blanik, yes. Other dural gliders maybe. Others don’t think so.

[Frank Whiteley]

On Thursday, March 21, 2019 at 11:14:42 AM UTC-6, wrote:
> Hi all.
>
> I listened from some pilots that the glider life hours reduce if you use winch start.
>
> Is that true? I looked for some data about and I did not found.
>
> have a nice day, José.

Any life adjustment issues should be in the POH or the maintenance manual. There were adjustment factors on our L-23 for winch launches, flying with the wing tip extensions, solo/dual flight, or for aerobatic flight.

Frank Whiteley

[José Ignacio Otero]

El jueves, 21 de marzo de 2019, 14:31:08 (UTC-3), Frank Whiteley escribió:
> On Thursday, March 21, 2019 at 11:14:42 AM UTC-6, wrote:
> > Hi all.
> >
> > I listened from some pilots that the glider life hours reduce if you use winch start.
> >
> > Is that true? I looked for some data about and I did not found.
> >
> > have a nice day, José.
>
> Any life adjustment issues should be in the POH or the maintenance manual.. There were adjustment factors on our L-23 for winch launches, flying with the wing tip extensions, solo/dual flight, or for aerobatic flight.
>
> Frank Whiteley


Hi Frank,

Thanks for reply, L-23 is an special situation with the AD in the wing roots.

What about K-13, Ka-6, Libelle, Std Austria, Lak-12, Std Cirrus, ASW-20...

[José Ignacio Otero]

El jueves, 21 de marzo de 2019, 14:30:05 (UTC-3), Eric Munk escribió:
> At 17:14 21 March 2019, wrote:
> >Hi all.
> >
> >I listened from some pilots that the glider life hours reduce if you
> use
> >wi=
> >nch start.
> >
> >Is that true? I looked for some data about and I did not found.
> >
> >have a nice day, Jos=C3=A9.
> >
>
> I know this is true for the Blanik and maybe other dural gliders.
> Certainly not any GFRP or wooden types.

Hi Erik,

Thanks fro reply, L-23 is speciall situation...

[Martin Gregorie[_6_]]

On Thu, 21 Mar 2019 11:52:53 -0700, José Ignacio Otero wrote:

> El jueves, 21 de marzo de 2019, 14:31:08 (UTC-3), Frank Whiteley
> escribió:
>> On Thursday, March 21, 2019 at 11:14:42 AM UTC-6,
>> wrote:
>> > Hi all.
>> >
>> > I listened from some pilots that the glider life hours reduce if you
>> > use winch start.
>> >
>> > Is that true? I looked for some data about and I did not found.
>> >
>> > have a nice day, José.
>>
>> Any life adjustment issues should be in the POH or the maintenance
>> manual. There were adjustment factors on our L-23 for winch launches,
>> flying with the wing tip extensions, solo/dual flight, or for aerobatic
>> flight.
>>
>> Frank Whiteley
>
>
> Hi Frank,
>
> Thanks for reply, L-23 is an special situation with the AD in the wing
> roots.
>
> What about K-13, Ka-6, Libelle, Std Austria, Lak-12, Std Cirrus,
> ASW-20...

There is nothing my Std Libelle's POH about launch method affecting
airframe lifetime. AFAIK they are fitted as standard with both CG and
nose hooks. Mine was, and so are the other two others based at the club.
Re-life inspection is at 3000 hours regardless of launch method.


--
Martin | martin at
Gregorie | gregorie dot org

[Ken Fixter[_3_]]

At 18:54 21 March 2019, José_Ignacio_Otero wrote:
>El jueves, 21 de marzo de 2019, 14:30:05 (UTC-3), Eric Munk
escribi=C3=B3:
>> At 17:14 21 March 2019, wrote:
>> >Hi all.
>> >
>> >I listened from some pilots that the glider life hours reduce if
you=20
>> use
>> >wi=3D
>> >nch start.
>> >
>> >Is that true? I looked for some data about and I did not found.
>> >
>> >have a nice day, Jos=3DC3=3DA9.
>> >
>>=20
>> I know this is true for the Blanik and maybe other dural gliders.=20
>> Certainly not any GFRP or wooden types.
>
>Hi Erik,
>
>Thanks fro reply, L-23 is speciall situation...
>
>
>Hi for the L13 the shortest airframe life is to winch launch two persons
on board and make it an aerobatic flight, longest airframe life aerotow
launch flown solo no aerobatics, by the manual all flights should be loged
according to each flight type launch,crew number, aerobatics or no
aerobatis if like our worn out L13 none of the details required about it's
flight use could be corolated when it came to how mutch airframe life
remained
so the fuz ended up as a flight simulator, the rest of the loose rivets
scrap metal.

[Bob Kuykendall]

What I've read is that the bending forces applied to the wings and tail during a typical winch launch are roughly equivalent to 3.5g flight. That is comfortably below the load limit of every common glider. However, it is high enough that repeated launches will eventually shorten the service life of an aluminum glider. The Blanik designers understood this very well, and the original service documentation was quite explicit about logging operations carefully so the service life could be tracked. Unfortunately, most operators did not do so.

Normal winching operations probably has no appreciable effect on the composite parts of a composite glider. However, I believe it was BGA analysis of repeated winch launch stresses that initiated the service bulletin on the steel end-pins ("spigots") on Grob 102, 103 and 109 series sailplanes.

As for wood sailplanes, my concern would mostly be around the age and condition of the structure, since many wood gliders are now half a century old. Since you don't feel the added stresses of winch launching the way you feel the g of vertical acceleration, it would be easy to get into the gray area between what the structure was originally built to sustain, and what it can actually sustain after fifty years of operation, repairs, and deterioration.

--Bob K.

[Eric Munk]

As Bob said, the only concern with wooden ships is adequate
maintenance which includes a timely stripdown to bare wood and
inspection of all structural components. Type of glue used is a
major factor, looking at recent issues with common glues like
Kaurit WHK.

GFRP ships like wooden ships have no life limitations based on
use, solely in hours. At least that I know of based on reading
dozena of manuals and type certificates. Looking forward to being
corrected. Have just done a life extension for an ASK21 that had
50,000+ launches and it was in great shape. Just had to replace
the main pins and stab pins as they had reached the end of their
fatigue life of 12,000 hours...

Theoretically, there’s a long fatigue life left in gliders like this when

looking at the calculations Eiri did for the PIK-20s...

At 02:02 22 March 2019, Bob Kuykendall wrote:
>What I've read is that the bending forces applied to the wings
and tail
>dur=
>ing a typical winch launch are roughly equivalent to 3.5g flight.
That is
>c=
>omfortably below the load limit of every common glider.
However, it is
>high=
> enough that repeated launches will eventually shorten the
service life of
>=
>an aluminum glider. The Blanik designers understood this very
well, and
>the=
> original service documentation was quite explicit about logging
>operations=
> carefully so the service life could be tracked. Unfortunately,
most
>operat=
>ors did not do so.
>
>Normal winching operations probably has no appreciable effect
on the
>compos=
>ite parts of a composite glider. However, I believe it was BGA
analysis of
>=
>repeated winch launch stresses that initiated the service bulletin
on the
>s=
>teel end-pins ("spigots") on Grob 102, 103 and 109 series
sailplanes.
>
>As for wood sailplanes, my concern would mostly be around the
age and
>condi=
>tion of the structure, since many wood gliders are now half a
century old.
>=
>Since you don't feel the added stresses of winch launching the
way you
>feel=
> the g of vertical acceleration, it would be easy to get into the
gray
>area=
> between what the structure was originally built to sustain, and
what it
>ca=
>n actually sustain after fifty years of operation, repairs, and
>deteriorati=
>on.
>
>--Bob K.
>

[José Ignacio Otero]

Thansk Martin !!





El jueves, 21 de marzo de 2019, 16:45:08 (UTC-3), Martin Gregorie escribió:
> On Thu, 21 Mar 2019 11:52:53 -0700, José Ignacio Otero wrote:
>
> > El jueves, 21 de marzo de 2019, 14:31:08 (UTC-3), Frank Whiteley
> > escribió:
> >> On Thursday, March 21, 2019 at 11:14:42 AM UTC-6,
> >> wrote:
> >> > Hi all.
> >> >
> >> > I listened from some pilots that the glider life hours reduce if you
> >> > use winch start.
> >> >
> >> > Is that true? I looked for some data about and I did not found.
> >> >
> >> > have a nice day, José.
> >>
> >> Any life adjustment issues should be in the POH or the maintenance
> >> manual. There were adjustment factors on our L-23 for winch launches,
> >> flying with the wing tip extensions, solo/dual flight, or for aerobatic
> >> flight.
> >>
> >> Frank Whiteley
> >
> >
> > Hi Frank,
> >
> > Thanks for reply, L-23 is an special situation with the AD in the wing
> > roots.
> >
> > What about K-13, Ka-6, Libelle, Std Austria, Lak-12, Std Cirrus,
> > ASW-20...
>
> There is nothing my Std Libelle's POH about launch method affecting
> airframe lifetime. AFAIK they are fitted as standard with both CG and
> nose hooks. Mine was, and so are the other two others based at the club.
> Re-life inspection is at 3000 hours regardless of launch method.
>
>
> --
> Martin | martin at
> Gregorie | gregorie dot org

[José Ignacio Otero]

Hi Bob.

Thanks for the reply, it was what I looking for !!

I think that the pilots how said that, were thinking that because the 3.52 g that the glider "suffer" during the wich start.

Have a nice day, José


El jueves, 21 de marzo de 2019, 23:02:51 (UTC-3), Bob Kuykendall escribió:
> What I've read is that the bending forces applied to the wings and tail during a typical winch launch are roughly equivalent to 3.5g flight. That is comfortably below the load limit of every common glider. However, it is high enough that repeated launches will eventually shorten the service life of an aluminum glider. The Blanik designers understood this very well, and the original service documentation was quite explicit about logging operations carefully so the service life could be tracked. Unfortunately, most operators did not do so.
>
> Normal winching operations probably has no appreciable effect on the composite parts of a composite glider. However, I believe it was BGA analysis of repeated winch launch stresses that initiated the service bulletin on the steel end-pins ("spigots") on Grob 102, 103 and 109 series sailplanes.
>
> As for wood sailplanes, my concern would mostly be around the age and condition of the structure, since many wood gliders are now half a century old.. Since you don't feel the added stresses of winch launching the way you feel the g of vertical acceleration, it would be easy to get into the gray area between what the structure was originally built to sustain, and what it can actually sustain after fifty years of operation, repairs, and deterioration.
>
> --Bob K.

[José Ignacio Otero]

Hi Erik,

Thanks for your time.

Yes, wooden gliders are in special situation, in my country Argentina, we lower the VNE to the half to make them safe because you never know the glue status.

Have a nice day, José.

El viernes, 22 de marzo de 2019, 4:45:03 (UTC-3), Eric Munk escribió:
> As Bob said, the only concern with wooden ships is adequate
> maintenance which includes a timely stripdown to bare wood and
> inspection of all structural components. Type of glue used is a
> major factor, looking at recent issues with common glues like
> Kaurit WHK.
>
> GFRP ships like wooden ships have no life limitations based on
> use, solely in hours. At least that I know of based on reading
> dozena of manuals and type certificates. Looking forward to being
> corrected. Have just done a life extension for an ASK21 that had
> 50,000+ launches and it was in great shape. Just had to replace
> the main pins and stab pins as they had reached the end of their
> fatigue life of 12,000 hours...
>
> Theoretically, there’s a long fatigue life left in gliders like this when
>
> looking at the calculations Eiri did for the PIK-20s...
>
> At 02:02 22 March 2019, Bob Kuykendall wrote:
> >What I've read is that the bending forces applied to the wings
> and tail
> >dur=
> >ing a typical winch launch are roughly equivalent to 3.5g flight.
> That is
> >c=
> >omfortably below the load limit of every common glider.
> However, it is
> >high=
> > enough that repeated launches will eventually shorten the
> service life of
> >=
> >an aluminum glider. The Blanik designers understood this very
> well, and
> >the=
> > original service documentation was quite explicit about logging
> >operations=
> > carefully so the service life could be tracked. Unfortunately,
> most
> >operat=
> >ors did not do so.
> >
> >Normal winching operations probably has no appreciable effect
> on the
> >compos=
> >ite parts of a composite glider. However, I believe it was BGA
> analysis of
> >=
> >repeated winch launch stresses that initiated the service bulletin
> on the
> >s=
> >teel end-pins ("spigots") on Grob 102, 103 and 109 series
> sailplanes.
> >
> >As for wood sailplanes, my concern would mostly be around the
> age and
> >condi=
> >tion of the structure, since many wood gliders are now half a
> century old.
> >=
> >Since you don't feel the added stresses of winch launching the
> way you
> >feel=
> > the g of vertical acceleration, it would be easy to get into the
> gray
> >area=
> > between what the structure was originally built to sustain, and
> what it
> >ca=
> >n actually sustain after fifty years of operation, repairs, and
> >deteriorati=
> >on.
> >
> >--Bob K.
> >

[AS]

On Friday, March 22, 2019 at 9:15:42 AM UTC-4, José Ignacio Otero wrote:
> Hi Bob.
>
> Thanks for the reply, it was what I looking for !!
>
> I think that the pilots how said that, were thinking that because the 3.52 g that the glider "suffer" during the wich start.
>
> Have a nice day, José
>
>
> El jueves, 21 de marzo de 2019, 23:02:51 (UTC-3), Bob Kuykendall escribió:
> > What I've read is that the bending forces applied to the wings and tail during a typical winch launch are roughly equivalent to 3.5g flight. That is comfortably below the load limit of every common glider. However, it is high enough that repeated launches will eventually shorten the service life of an aluminum glider. The Blanik designers understood this very well, and the original service documentation was quite explicit about logging operations carefully so the service life could be tracked. Unfortunately, most operators did not do so.
> >
> > Normal winching operations probably has no appreciable effect on the composite parts of a composite glider. However, I believe it was BGA analysis of repeated winch launch stresses that initiated the service bulletin on the steel end-pins ("spigots") on Grob 102, 103 and 109 series sailplanes.
> >
> > As for wood sailplanes, my concern would mostly be around the age and condition of the structure, since many wood gliders are now half a century old. Since you don't feel the added stresses of winch launching the way you feel the g of vertical acceleration, it would be easy to get into the gray area between what the structure was originally built to sustain, and what it can actually sustain after fifty years of operation, repairs, and deterioration.
> >
> > --Bob K.

Guys - let's stop making the winch launch sound like it is a glider shredding method! The force introduced into the glider's structure is limited by a weak-link. The max. breaking strength of these weak-links together with the Vw are determined by the designer and documented in the POH.
I am just referencing two popular two-seat trainers here:
ASK-21 - MTOW of 600kg, black weak-link of 1,000kg, ratio 1:1.66
G103 Twin-II - MTOW 580kg, red weak-link of 750kg, ratio 1:1.29
(may the gods of physics forgive me for mixing mass and force units here!)
There is a load added during the launch when the glider transitions from the initial shallow climb into the full climb (akin to performing a small segment of a looping) but all this will not get you near the mentioned 3.5g!
However, all this is predicated on the use of proper weak-links. If you ignore these safety devices, then all bets are off. To the best of my knowledge, there hasn't been a properly maintained glider launched with the correct weak-links, that got pulled apart during the launch!

Uli
'AS'

[José Ignacio Otero]

Hi Uli,

I like the idea to use winch luch but I do not know about it, talking with some instructor and pilot of my country (winch is not popular here) I listen many times about this "structure fatigue" but I do not found any about that, and that is the reason of my question.
Your argument is clear and reasonable. Do you have any winch launch procedure file or something similar to know more about it?

Thanks for your time, José.


El viernes, 22 de marzo de 2019, 12:17:47 (UTC-3), AS escribió:
> On Friday, March 22, 2019 at 9:15:42 AM UTC-4, José Ignacio Otero wrote:
> > Hi Bob.
> >
> > Thanks for the reply, it was what I looking for !!
> >
> > I think that the pilots how said that, were thinking that because the 3..52 g that the glider "suffer" during the wich start.
> >
> > Have a nice day, José
> >
> >
> > El jueves, 21 de marzo de 2019, 23:02:51 (UTC-3), Bob Kuykendall escribió:
> > > What I've read is that the bending forces applied to the wings and tail during a typical winch launch are roughly equivalent to 3.5g flight. That is comfortably below the load limit of every common glider. However, it is high enough that repeated launches will eventually shorten the service life of an aluminum glider. The Blanik designers understood this very well, and the original service documentation was quite explicit about logging operations carefully so the service life could be tracked. Unfortunately, most operators did not do so.
> > >
> > > Normal winching operations probably has no appreciable effect on the composite parts of a composite glider. However, I believe it was BGA analysis of repeated winch launch stresses that initiated the service bulletin on the steel end-pins ("spigots") on Grob 102, 103 and 109 series sailplanes.
> > >
> > > As for wood sailplanes, my concern would mostly be around the age and condition of the structure, since many wood gliders are now half a century old. Since you don't feel the added stresses of winch launching the way you feel the g of vertical acceleration, it would be easy to get into the gray area between what the structure was originally built to sustain, and what it can actually sustain after fifty years of operation, repairs, and deterioration.
> > >
> > > --Bob K.
>
> Guys - let's stop making the winch launch sound like it is a glider shredding method! The force introduced into the glider's structure is limited by a weak-link. The max. breaking strength of these weak-links together with the Vw are determined by the designer and documented in the POH.
> I am just referencing two popular two-seat trainers here:
> ASK-21 - MTOW of 600kg, black weak-link of 1,000kg, ratio 1:1.66
> G103 Twin-II - MTOW 580kg, red weak-link of 750kg, ratio 1:1.29
> (may the gods of physics forgive me for mixing mass and force units here!)
> There is a load added during the launch when the glider transitions from the initial shallow climb into the full climb (akin to performing a small segment of a looping) but all this will not get you near the mentioned 3.5g!
> However, all this is predicated on the use of proper weak-links. If you ignore these safety devices, then all bets are off. To the best of my knowledge, there hasn't been a properly maintained glider launched with the correct weak-links, that got pulled apart during the launch!
>
> Uli
> 'AS'

[AS]

On Friday, March 22, 2019 at 11:55:34 AM UTC-4, José Ignacio Otero wrote:
> Hi Uli,
>
> I like the idea to use winch luch but I do not know about it, talking with some instructor and pilot of my country (winch is not popular here) I listen many times about this "structure fatigue" but I do not found any about that, and that is the reason of my question.
> Your argument is clear and reasonable. Do you have any winch launch procedure file or something similar to know more about it?
>
> Thanks for your time, José.
>
>
> El viernes, 22 de marzo de 2019, 12:17:47 (UTC-3), AS escribió:
> > On Friday, March 22, 2019 at 9:15:42 AM UTC-4, José Ignacio Otero wrote:
> > > Hi Bob.
> > >
> > > Thanks for the reply, it was what I looking for !!
> > >
> > > I think that the pilots how said that, were thinking that because the 3.52 g that the glider "suffer" during the wich start.
> > >
> > > Have a nice day, José
> > >
> > >
> > > El jueves, 21 de marzo de 2019, 23:02:51 (UTC-3), Bob Kuykendall escribió:
> > > > What I've read is that the bending forces applied to the wings and tail during a typical winch launch are roughly equivalent to 3.5g flight. That is comfortably below the load limit of every common glider. However, it is high enough that repeated launches will eventually shorten the service life of an aluminum glider. The Blanik designers understood this very well, and the original service documentation was quite explicit about logging operations carefully so the service life could be tracked. Unfortunately, most operators did not do so.
> > > >
> > > > Normal winching operations probably has no appreciable effect on the composite parts of a composite glider. However, I believe it was BGA analysis of repeated winch launch stresses that initiated the service bulletin on the steel end-pins ("spigots") on Grob 102, 103 and 109 series sailplanes.
> > > >
> > > > As for wood sailplanes, my concern would mostly be around the age and condition of the structure, since many wood gliders are now half a century old. Since you don't feel the added stresses of winch launching the way you feel the g of vertical acceleration, it would be easy to get into the gray area between what the structure was originally built to sustain, and what it can actually sustain after fifty years of operation, repairs, and deterioration.
> > > >
> > > > --Bob K.
> >
> > Guys - let's stop making the winch launch sound like it is a glider shredding method! The force introduced into the glider's structure is limited by a weak-link. The max. breaking strength of these weak-links together with the Vw are determined by the designer and documented in the POH.
> > I am just referencing two popular two-seat trainers here:
> > ASK-21 - MTOW of 600kg, black weak-link of 1,000kg, ratio 1:1.66
> > G103 Twin-II - MTOW 580kg, red weak-link of 750kg, ratio 1:1.29
> > (may the gods of physics forgive me for mixing mass and force units here!)
> > There is a load added during the launch when the glider transitions from the initial shallow climb into the full climb (akin to performing a small segment of a looping) but all this will not get you near the mentioned 3.5g!
> > However, all this is predicated on the use of proper weak-links. If you ignore these safety devices, then all bets are off. To the best of my knowledge, there hasn't been a properly maintained glider launched with the correct weak-links, that got pulled apart during the launch!
> >
> > Uli
> > 'AS'


Hello José,

Try this manual for starters, which was put together by Bill Daniels here in the US using data and procedures from various sources:
http://www.pas.rochester.edu/~cline/Winch%20launch%20training%20guide%20Rev%2012.pdf
I don't know of any similar documents in Spanish but I am sure they exist.
Good luck,


Uli
'AS'

[José Ignacio Otero]

Many thanks Uli, it look very complete.

Have a nice weekend, José.



El viernes, 22 de marzo de 2019, 13:36:51 (UTC-3), AS escribió:
> On Friday, March 22, 2019 at 11:55:34 AM UTC-4, José Ignacio Otero wrote:
> > Hi Uli,
> >
> > I like the idea to use winch luch but I do not know about it, talking with some instructor and pilot of my country (winch is not popular here) I listen many times about this "structure fatigue" but I do not found any about that, and that is the reason of my question.
> > Your argument is clear and reasonable. Do you have any winch launch procedure file or something similar to know more about it?
> >
> > Thanks for your time, José.
> >
> >
> > El viernes, 22 de marzo de 2019, 12:17:47 (UTC-3), AS escribió:
> > > On Friday, March 22, 2019 at 9:15:42 AM UTC-4, José Ignacio Otero wrote:
> > > > Hi Bob.
> > > >
> > > > Thanks for the reply, it was what I looking for !!
> > > >
> > > > I think that the pilots how said that, were thinking that because the 3.52 g that the glider "suffer" during the wich start.
> > > >
> > > > Have a nice day, José
> > > >
> > > >
> > > > El jueves, 21 de marzo de 2019, 23:02:51 (UTC-3), Bob Kuykendall escribió:
> > > > > What I've read is that the bending forces applied to the wings and tail during a typical winch launch are roughly equivalent to 3.5g flight. That is comfortably below the load limit of every common glider. However, it is high enough that repeated launches will eventually shorten the service life of an aluminum glider. The Blanik designers understood this very well, and the original service documentation was quite explicit about logging operations carefully so the service life could be tracked. Unfortunately, most operators did not do so.
> > > > >
> > > > > Normal winching operations probably has no appreciable effect on the composite parts of a composite glider. However, I believe it was BGA analysis of repeated winch launch stresses that initiated the service bulletin on the steel end-pins ("spigots") on Grob 102, 103 and 109 series sailplanes.
> > > > >
> > > > > As for wood sailplanes, my concern would mostly be around the age and condition of the structure, since many wood gliders are now half a century old. Since you don't feel the added stresses of winch launching the way you feel the g of vertical acceleration, it would be easy to get into the gray area between what the structure was originally built to sustain, and what it can actually sustain after fifty years of operation, repairs, and deterioration.
> > > > >
> > > > > --Bob K.
> > >
> > > Guys - let's stop making the winch launch sound like it is a glider shredding method! The force introduced into the glider's structure is limited by a weak-link. The max. breaking strength of these weak-links together with the Vw are determined by the designer and documented in the POH.
> > > I am just referencing two popular two-seat trainers here:
> > > ASK-21 - MTOW of 600kg, black weak-link of 1,000kg, ratio 1:1.66
> > > G103 Twin-II - MTOW 580kg, red weak-link of 750kg, ratio 1:1.29
> > > (may the gods of physics forgive me for mixing mass and force units here!)
> > > There is a load added during the launch when the glider transitions from the initial shallow climb into the full climb (akin to performing a small segment of a looping) but all this will not get you near the mentioned 3..5g!
> > > However, all this is predicated on the use of proper weak-links. If you ignore these safety devices, then all bets are off. To the best of my knowledge, there hasn't been a properly maintained glider launched with the correct weak-links, that got pulled apart during the launch!
> > >
> > > Uli
> > > 'AS'
>
>
> Hello José,
>
> Try this manual for starters, which was put together by Bill Daniels here in the US using data and procedures from various sources:
> http://www.pas.rochester.edu/~cline/Winch%20launch%20training%20guide%20Rev%2012.pdf
> I don't know of any similar documents in Spanish but I am sure they exist..
> Good luck,
>
>
> Uli
> 'AS'

[Bob Kuykendall]

On Friday, March 22, 2019 at 8:17:47 AM UTC-7, AS wrote:

> Guys - let's stop making the winch launch sound like it is a glider shredding method!...

> ASK-21 - MTOW of 600kg, black weak-link of 1,000kg, ratio 1:1.66...

Let's remember that the critical factor here is wing root bending moment, which relates much more closely to the non-lifting mass than it does to the total mass.

Taking the ASK21 maximum non-lifting mass of 410 kg as our metric, the ratio in question is 1000/410 = 2.43.

True, not the 3.5 I cited, but still a substantial value.

--Bob K.

[AS]

On Friday, March 22, 2019 at 1:22:07 PM UTC-4, Bob Kuykendall wrote:
> On Friday, March 22, 2019 at 8:17:47 AM UTC-7, AS wrote:
>
> > Guys - let's stop making the winch launch sound like it is a glider shredding method!...
>
> > ASK-21 - MTOW of 600kg, black weak-link of 1,000kg, ratio 1:1.66...
>
> Let's remember that the critical factor here is wing root bending moment, which relates much more closely to the non-lifting mass than it does to the total mass.
>
> Taking the ASK21 maximum non-lifting mass of 410 kg as our metric, the ratio in question is 1000/410 = 2.43.
>
> True, not the 3.5 I cited, but still a substantial value.
>
> --Bob K.

No doubt, Bob - thanks for that additional clarification! And that's why I am a stickler for the correct weak-link and adherence to Vw during the full climb phase of the launch. :-)

Uli
'AS'

[Bob Kuykendall]

On Friday, March 22, 2019 at 10:22:07 AM UTC-7, I wrote:

> Taking the ASK21 maximum non-lifting mass of 410 kg as our metric, the ratio in question is 1000/410 = 2.43.

I think I miscalculated.

If we're considering the root bending moment caused by a launch that applies 1000 kg downward to an ASK21, we also have to consider the load applied by the non-lifting mass of the glider itself. The load being reacted by the wings is actually:

1000 kg delivered by winch cable
410 kg delivered by non-lifting mass of glider
------
1410 kg

The ratio 1410/410 = 3.44 is the equivalent g load of the bending moment reacted by the wings. Which puts us back in the neighborhood of the 3.5g I originally cited.

--Bob K.

[[email protected]]

Hi José,

besides some exceptions (like Blanik or Romanian IS gliders), winch launches do not cause additional limitation of glider life times on top of the usual flight time limits.

Winch launching is a very common method in many European countries. The ASK13 of our club has close to 50,000 starts, 95% of them as winch launches. We safely take it to Vne, do basic instructions and spin trainings with it. There is no doubt that it can safely be flown within the approved operational limits. It has always been stored in a dry place and received a major overhaul 15 years ago.

If you there is any doubt about the airworthiness of a glider, it should receive a thorough inspection rather than being flown up to 50% of Vne.

Best regards,
Christoph