Wing Launch - Can it pull your wings off?

Derek C wrote:
The consequence of using a 10% weaker link would be a greater chance
of a broken weak link and a failed launch, which might be hazardous in
itself under some circumstances.

No, never! A cable brake is routine and *never* hazardous in *any*
circumstances. If it is, then something in your operation is seriously
flawed.

But a cable brake (or weak link brake) is always an annoyance, as it
interrupts the operation.

On Aug 12, 4:12*pm, Frank Whiteley wrote:
On Aug 12, 3:16*pm, ContestID67 wrote:



I was sent this link from a UK soaring friend of mine about a death
when the wings came off of a glider during a winch tow.http://www.dailymail.co.uk/news/arti...lunged-death-b...

Sad story. *A few things;

- My friend's thought was that the wing pins were left out. *Howerver,
this was the second flight of the day. *Both winch launches. *So I
would think that the wing pins were installed but the wings failed
under a winch load. *Which glider was it? *Older? *Wooden spars?
Never having had a winch launch, what happens if you don't release
back pressure at the top? *Can you pull your wings off? *Maybe
safeties on the pins were missed and the pins wiggled out on the
second flight after staying in for the first.

- I was under the impression that the BGA required parachutes for all
pilots. *Wrong? *1000 ft should have been enough to get out in time
but who knows what was happening in the cockpit or if she was 1000 MSL
or AGL at the time.

Thanks.

- John DeRosa

It was aFoka4.

Foka-4was a derivative of theFokalinehttp://en.wikipedia.org/wiki/Foka_%28glider%29
Cobra was the next to last iteration, with 17m being the last.http://en.wikipedia.org/wiki/SZD-36_Cobra_15
Note the comments on failures.

I don't know that the4had the same wing join design, but suspect it
was very similar.
There was a wing failure on a Cobra in the US and a sobering analysis.http://www.sylacaugasoaring.com/SZD%...%20WARNING.htm

The SHK has an expanding vertical pin. *There's an anecdotal story of
someone who used the right-hand to expand the pin, and finished the
job with left-hand, in the opposite direction. *The wings reportedly
departed at the top of the launch. *The pilot reportedly pulled the
tail chute on the way down.

I believe that some German studies found that successful egress and
parachute deployment below 600m is unlikely, of course there are
exceptions. *The better emergency chutes are life saving from 100ft
agl at 100kts horizontal.

Wing failure on a winch launch is very rare. *There was a K-7 at RAF
Dishforth in the UK a while back, but the investigation determined
there was prior damage to the spar which was not found following
another incident. *There was a homebuilt in Colorado that had a wing
failure due to aileron flutter during a winch launch. *After two weak
link breaks, the pilot doubled the weak link (unknown to the winch
crew). *The described flight path was one of climb, level off, climb,
level off, climb, glider breakup, crash. *The wing inspection hatch
was found early in the flight path. *What did not appear in the NTSB
report was that the pilot was refused further tows at the local FBO
after the glider had suffered significant aileron flutter on aero tow.

I winched at RAF Bicester when it was the RAF/GSA Centre. *Appropriate
weak links were always used, like any UK club. *It's not a long run,
but easy enough to climb away on the thermal day.

Steel wire rope used in many places typically has a breaking strength
of 2800-3500lbs. *The new UHMWPE 12-strand ropes (Spectra, Plasma,
Dyneema, Amsteel) now in common use are nominally 3500-5400lbs
breaking strength at similar diameters, thus use of correct weak links
are essential to avoid damaging a glider as some winches have
substantial power and there are also gusts and thermals to allow for.

Frank Whiteley

Reading the UK URAS new group today, I see someone posted a link to
this FAA doc
http://www.ntsb.gov/recs/letters/1974/A74_100_101.pdf
which gives another mode of failure specific to the Foka 4.

The AAIB analysis will prove interesting.

Frank Whiteley

On Aug 12, 10:16*pm, ContestID67 wrote:
I was sent this link from a UK soaring friend of mine about a death
when the wings came off of a glider during a winch tow.http://www.dailymail.co.uk/news/arti...lunged-death-b...

Sad story. *A few things;

- My friend's thought was that the wing pins were left out. *Howerver,
this was the second flight of the day. *Both winch launches. *So I
would think that the wing pins were installed but the wings failed
under a winch load. *Which glider was it? *Older? *Wooden spars?
Never having had a winch launch, what happens if you don't release
back pressure at the top? *Can you pull your wings off? *Maybe
safeties on the pins were missed and the pins wiggled out on the
second flight after staying in for the first.

- I was under the impression that the BGA required parachutes for all
pilots. *Wrong? *1000 ft should have been enough to get out in time
but who knows what was happening in the cockpit or if she was 1000 MSL
or AGL at the time.

Thanks.

- John DeRosa

Getting back to the original subject, many Polish gliders have a
rigging system which consists of vertical tapered mainpins that expand
outwards on a screw to engage with the wing root fittings. This is
basically a good system because the pins stay as part of the
structure, so there is no separate mainpin that can be lost, and if
correctly assembled gives a positive, secure and play free joint. I
understand that the problem comes when the bushing that keeps the
expanding pins central becomes worn. Then it is possible that one half
of the pin may not fully engage in one the wing root fitting, even if
the jack screw is fully tightened. I have a share in an elderly Polish
two-seater glider with two such taper mainpins. We are always careful
to check that these are fully and equally engaged in the wing root
fittings when rigging it, but it is easier to see this than in the
single seaters with a single pin. See:
http://www.sylacaugasoaring.com/SZD%...%20WARNING.htm

On the subject of bailing out, it is not compulsory to wear parachutes
in gliders in the UK, but it is normal practice to do so if the design
of the glider permits. We don't know exactly at what height the wings
fell off the crash glider (but probably less than 1000ft) and the
fuselage would have dropped like a stone without them. I doubt if the
pilot could have got out in time.

Derek C

On Aug 12, 10:16*pm, ContestID67 wrote:
I was sent this link from a UK soaring friend of mine about a death
when the wings came off of a glider during a winch tow.http://www.dailymail.co.uk/news/arti...lunged-death-b...

Sad story. *A few things;

- My friend's thought was that the wing pins were left out. *Howerver,
this was the second flight of the day. *Both winch launches. *So I
would think that the wing pins were installed but the wings failed
under a winch load. *Which glider was it? *Older? *Wooden spars?
Never having had a winch launch, what happens if you don't release
back pressure at the top? *Can you pull your wings off? *Maybe
safeties on the pins were missed and the pins wiggled out on the
second flight after staying in for the first.

- I was under the impression that the BGA required parachutes for all
pilots. *Wrong? *1000 ft should have been enough to get out in time
but who knows what was happening in the cockpit or if she was 1000 MSL
or AGL at the time.

Thanks.

- John DeRosa

Getting back to the original subject, many Polish gliders have a
rigging system which consists of vertical tapered mainpins that expand
outwards on a screw to engage with the wing root fittings. This is
basically a good system because the pins stay as part of the
structure, so there is no separate mainpin that can be lost, and if
correctly assembled gives a positive, secure and play free joint. I
understand that the problem comes when the bushing that keeps the
expanding pins central becomes worn. Then it is possible that one half
of the pin may not fully engage in one of the wing root fitting, even
if the jack screw is fully tightened. I have a share in an elderly
Polish two-seater glider with two such taper mainpins. We are always
careful to check that these are fully and equally engaged in the wing
root fittings when rigging it, but it is easier to see this than in
the single seaters with a single pin. See:
http://www.sylacaugasoaring.com/SZD%...%20WARNING.htm

On the subject of bailing out, it is not compulsory to wear parachutes
in gliders in the UK, but it is normal practice to do so if the design
of the glider permits. We don't know exactly at what height the wings
fell off the crash glider (but probably less than 1000ft) and the
fuselage would have dropped like a stone without them. I doubt if the
pilot could have got out in time.

Derek C

On Aug 12, 10:16*pm, ContestID67 wrote:
I was sent this link from a UK soaring friend of mine about a death
when the wings came off of a glider during a winch tow.http://www.dailymail.co.uk/news/arti...lunged-death-b...

Sad story. *A few things;

- My friend's thought was that the wing pins were left out. *Howerver,
this was the second flight of the day. *Both winch launches. *So I
would think that the wing pins were installed but the wings failed
under a winch load. *Which glider was it? *Older? *Wooden spars?
Never having had a winch launch, what happens if you don't release
back pressure at the top? *Can you pull your wings off? *Maybe
safeties on the pins were missed and the pins wiggled out on the
second flight after staying in for the first.

- I was under the impression that the BGA required parachutes for all
pilots. *Wrong? *1000 ft should have been enough to get out in time
but who knows what was happening in the cockpit or if she was 1000 MSL
or AGL at the time.

Thanks.

- John DeRosa

Getting back to the original subject, many Polish gliders have a
rigging system which consists of vertical tapered mainpins that expand
outwards on a screw to engage with the wing root fittings. This is
basically a good system because the pins stay as part of the
structure, so there is no separate mainpin that can be lost, and if
correctly assembled gives a positive, secure and play free joint. I
understand that the problem comes when the bushing that keeps the
expanding pins central becomes worn. Then it is possible that one half
of the pin may not fully engage in one of the wing root fitting, even
if the jack screw is fully tightened. I have a share in an elderly
Polish two-seater glider with two such taper mainpins. We are always
careful to check that these are fully and equally engaged in the wing
root fittings when rigging it, but it is easier to see this than in
the single seaters with a single pin. See:
http://www.sylacaugasoaring.com/SZD%...%20WARNING.htm

On the subject of bailing out, it is not compulsory to wear parachutes
in gliders in the UK, but it is normal practice to do so if the design
of the glider permits. We don't know exactly at what height the wings
fell off the crash glider (but probably less than 1000ft) and the
fuselage would have dropped like a stone without them. I doubt if the
pilot could have got out in time.

Derek C

We had a Foka 4 at my club in the 1970s, with this sort of expanding
bolt.

My recollection is that the owners used to count the number of turns
to get the full expansion. If the number of turns was correct, and the
top bolt was visible in the right place, then the invisible lower one
must also have fully engaged with the lower lugs.

Might be a useful check in the absence of a visible sign.

(I'm not saying that this had anything to do with the recent accident
- the latter may have been caused by something different.)

Chris N

On Aug 22, 9:09*am, Chris Nicholas wrote:
We had a Foka 4 at my club in the 1970s, with this sort of expanding
bolt.

My recollection is that the owners used to count the number of turns
to get the full expansion. If the number of turns was correct, and the
top bolt was visible in the right place, then the invisible lower one
must also have fully engaged with the lower lugs.

Might be a useful check in the absence of a visible sign.

(I'm not saying that this had anything to do with the recent accident
- the latter may have been caused by something different.)


It's an assumption that if the correct number of turns have been done
and the top bolt is seen to be correctly expanded that the lower bolt
has also correctly expanded. I gather that in the US Cobra accident
there was some sort of fault in the bolt such that the top part
expanded correctly but the bottom didn't, and it is very hard to see.

Personally I am so glad I fly a relatively modern glass glider with
two horizontal main pins where the only mechanism is me pushing them
home and then crossing and latching their 'handles'.

On Aug 23, 9:52*am, Cats wrote:
On Aug 22, 9:09*am, Chris Nicholas wrote:

We had a Foka 4 at my club in the 1970s, with this sort of expanding
bolt.

My recollection is that the owners used to count the number of turns
to get the full expansion. If the number of turns was correct, and the
top bolt was visible in the right place, then the invisible lower one
must also have fully engaged with the lower lugs.

Might be a useful check in the absence of a visible sign.

(I'm not saying that this had anything to do with the recent accident
- the latter may have been caused by something different.)

It's an assumption that if the correct number of turns have been done
and the top bolt is seen to be correctly expanded that the lower bolt
has also correctly expanded. *I gather that in the US Cobra accident
there was some sort of fault in the bolt such that the top part
expanded correctly but the bottom didn't, and it is very hard to see.

Personally I am so glad I fly a relatively modern glass glider with
two horizontal main pins where the only mechanism is me pushing them
home and then crossing and latching their 'handles'.

In the US Cobra accident the taper bolt mainpin expanded correctly,
but wasn't centred due to wear in the central locating bush. Hence it
didn't fully engage in the bottom wing root fitting. This failure
could have been prevented by a visual inspection, but apparently it is
difficult to see the bottom fitting in this type of glider. I will
repeat that there is nothing intrinsically wrong with this rigging
system, as long as it is properly maintained and a visual check is
made after rigging.

Derek C

Following the recent break up of a Foka 4 glider during a winch
launch, the British Gliding Association has issued the following
safety alert. Please note that it also applies to a number of other
glider types fitting with expanding taper mainpins.

http://www.gliding.co.uk/bgainfo/saf...lert020910.pdf

Derek C


On Aug 23, 10:19*am, Derek C wrote:
On Aug 23, 9:52*am, Cats wrote:


On Aug 22, 9:09*am, Chris Nicholas wrote:

We had a Foka 4 at my club in the 1970s, with this sort of expanding
bolt.

My recollection is that the owners used to count the number of turns
to get the full expansion. If the number of turns was correct, and the
top bolt was visible in the right place, then the invisible lower one
must also have fully engaged with the lower lugs.

Might be a useful check in the absence of a visible sign.

(I'm not saying that this had anything to do with the recent accident
- the latter may have been caused by something different.)

It's an assumption that if the correct number of turns have been done
and the top bolt is seen to be correctly expanded that the lower bolt
has also correctly expanded. *I gather that in the US Cobra accident
there was some sort of fault in the bolt such that the top part
expanded correctly but the bottom didn't, and it is very hard to see.

Personally I am so glad I fly a relatively modern glass glider with
two horizontal main pins where the only mechanism is me pushing them
home and then crossing and latching their 'handles'.

In the US Cobra accident the taper bolt mainpin expanded correctly,
but wasn't centred due to wear in the central locating bush. Hence it
didn't fully engage in the bottom wing root fitting. This failure
could have been prevented by a visual inspection, but apparently it is
difficult to see the bottom fitting in this type of glider. I will
repeat that there is nothing intrinsically wrong with this rigging
system, as long as it is properly maintained and a visual check is
made after rigging.

Derek C- Hide quoted text -

- Show quoted text -