Does anyone use a tug tow hook that releases automatically whenglider kites?

On 23/02/2014 01:35, kirk.stant wrote:

Without any statistics, my scientific wild-ass guess (SWAG) is about
80% nose tow hook on glider and 19% low tow; I'll concede 1% to
training just because I know how poorly most glider pilots listen to
any training when "safety" is involved...

I'd agree with that split. I'd also add that there are no Schweitzer
hooks in Oz. That helps a lot.

GC

Kirk 66

Let's say I'm on low tow and fly perpendicular to the "tube" of rotor (aka horizontal circular air flow/ vortex)...

The tug goes abruptly up, the glider goes abruptly down. When the glider pulls down on the tug tail, can it increase the tug AOA and stall the tug wings?

On 23/02/2014 01:46, Chris Rollings wrote:

I've been aware of the Australian preference for low tow and the reasons
for it for over 30 years. My own flight testing and experience lead me to
believe that it does not significantly reduce the probability of a kiting
accident.

Well, Australia's experience shows that it does.

I would also say that, having flown in the UK, the Oz rules are
sometimes seen there as somewhat wussy - along the lines of "real men
don't fly low tow". Chris's irrational vehemence makes me think he may
be one of that 'sometimes' group.

GC

For those who consider using a nose hook largely solves the
problem of kiting, I suggest watching
http://www.youtube.com/watch?v=4MkCnVYa3VY
It is a video of a pilot's second solo flight in a K13 with an aerotow
launch using the nose hook. The pilot is distracted when the
airbrakes open, he looks out at the airbrakes, closes/locks them
and when he looks forward again the tug is disappearing below the
nose. The glider pilot releases. This is at 90m agl.
The commentary and text (in French) gives some extra insight and
analysis. CRIS is the acronym for the French pre-flight checks.
I met the tug pilot some months after this incident - he said that it
was very fortunate that the glider pilot released so promptly as the
towplane was starting to be tipped. It was a big lesson learnt for
him personally, not least to keep a hand VERY close to the release.
Enlightening and interesting thread...

On Saturday, February 22, 2014 11:14:30 AM UTC-5, son_of_flubber wrote:
Let's say I'm on low tow and fly perpendicular to the "tube" of rotor (aka horizontal circular air flow/ vortex)... The tug goes abruptly up, the glider goes abruptly down. When the glider pulls down on the tug tail, can it increase the tug AOA and stall the tug wings?

No- Our experience is that you can't pull the tail down that much. We have towed at speeds so low in low tow when testing that the glider was adding to the stability of the pair by keeping the tug straight.
In any case it is so obvious that the glider pliot will take corrective action.
UH

On 23/02/2014 03:14, son_of_flubber wrote:
Let's say I'm on low tow and fly perpendicular to the "tube" of rotor
(aka horizontal circular air flow/ vortex)...

The tug goes abruptly up, the glider goes abruptly down. When the
glider pulls down on the tug tail, can it increase the tug AOA and
stall the tug wings?


Maybe. I've never heard of it happening. The tug is also pulling the
glider nose up which will make it want to climb and reduce the downward
pull. We could place bets on who might win.

The actual answer is that if the tug pilot runs out of forward stick, he
has a big handle and a Tost release which reliably solve his problem.

GC

Yes, but that was a fixed hitch. I would think that, as the glider shot
upwards, the hinged release would swivel upward before the tug's nose
started down. Is it because the arm aft of the hinge point would be so
short?

I always preferred mechanical stuff to electrical, but the education was
free so I had to take what was offered.


"Steve Leonard" wrote in message
...
Dan, that might work if the towplane's attitude was constant. However,
during a kiting event, the towplane is being pitched nose down, so the hitch
would not likely get activated, as the hitch to surrounding structure angle
may not change. I wish it could be that simple, but it isn't. See the
previous post about a kiting even where the glider was still in sight in the
mirror, even though the towplane was significantly nose down.

Steve

Huh! Sounds good to me!


"GC" wrote in message
eb.com...
On 22/02/2014 16:17, Alan wrote:

...You don't get kiting if you fly normal "high" tow behind the towplane,
if you remain in control.

If you don't remain in control, starting from low tow is not going to
make a lot of difference.

Experience (tens of thousands of aerotows) shows there is an enormous
difference. The inadequate control and time to go from high tow to kiting
is orders of magnitude different from that required to go from low tow to
kiting. In fact, I've never heard of that ever happening. Even with low
time students. Kiting from high tow, however, is apparently so common as
to need a whole new system of electronic whizzbangery and gallons of
bandwidth to stop.

If the tug has just lifted off, being in low tow sounds a bit
difficult,
but that would be a particularly hazardous time.

Yes. Liftoff is a time to be wary and we train accordingly. Nevertheless,
all I can say is that low tow has prevented kiting accidents for many
years. But don't take my word for it, keep this ridiculous discussion
going with another screwball idea for pivoting, autoswivelling,
pitch-sensing, stick-following nonsense.

If the issue is serious - as it was in Australia - flying low tow will
solve it. If it isn't - see my previous post.

GC



As for automatic methods to mitigate the problem, perhaps the solution
is not to modify tow planes, but to modify gliders. If the glider is
in a very high pitch attitude on tow, it might be a good time to
automatically
release.

Another modification might be to attach the tow rope to the top of the
glider.
This would cause the tow force to pitch the glider down.


Is this more of a problem when folks try to tow a slow glider like a
2-33 at
high speeds?

Alan

Elevator power.
I may have missed the comment , but has anyone experienced
insufficient pitch down authority with full forward stick?
Our club had an incident in very rough conditions.
A PIK20B , belly hook, flown by a very experienced pilot,
was forced to release as a snatch caused an uncontrollable
pitchup. CG position not known, but the pilot was not large.
I did a calculation ( 30 years ago) to see if this was plausible
and indeed, if the CG was is near the aft limit with a PIK 20,
the transient pitchup couple in a snatch can probably overpower
full nose down elevator, thus initiating kiting.
There a re probably many other sailplanes susceptable to
this near the aft CG limit.
John firth

At 14:46 22 February 2014, Chris Rollings wrote:
At 14:28 22 February 2014, wrote:
On Saturday, February 22, 2014 1:58:28 AM UTC-6, GC wrote:
On 22/02/2014 16:17, Alan wrote:
=20
=20
=20
...You don't get kiting if you fly normal "high" tow behind the
towplan=
e,
=20
if you remain in control.
=20

=20
If you don't remain in control, starting from low tow is not
going
t=
o
=20
make a lot of difference.
=20
=20
=20
Experience (tens of thousands of aerotows) shows there is a
enormous=20
=20
difference. The inadequate control and time to go from high tow to=20
=20
kiting is orders of magnitude different from that required to g
from=20
=20
low tow to kiting. In fact, I've never heard of that eve
happening.=20
=20
Even with low time students. Kiting from high tow, however, is=20
=20
apparently so common as to need a whole new system of electronic=20
=20
whizzbangery and gallons of bandwidth to stop.
=20
=20
=20
If the tug has just lifted off, being in low tow sounds a bit
diffic=
ult,
=20
but that would be a particularly hazardous time.
=20
=20
=20
Yes. Liftoff is a time to be wary and we train accordingly.=20
=20
Nevertheless, all I can say is that low tow has prevented kiting=20
=20
accidents for many years. But don't take my word for it, keep this=20
=20
ridiculous discussion going with another screwball idea fo
pivoting,=20
=20
autoswivelling, pitch-sensing, stick-following nonsense.
=20
=20
=20
If the issue is serious - as it was in Australia - flying low to
will=20
=20
solve it. If it isn't - see my previous post.
=20
=20
=20
GC
=20
=20
=20

=20

=20
As for automatic methods to mitigate the problem, perhaps the
soluti=
on
=20
is not to modify tow planes, but to modify gliders. If the glider
is
=20
in a very high pitch attitude on tow, it might be a good time to
automa=
tically
=20
release.
=20

=20
Another modification might be to attach the tow rope to the top
of
t=
he glider.
=20
This would cause the tow force to pitch the glider down.
=20

=20

=20
Is this more of a problem when folks try to tow a slow glider
like
a=
2-33 at
=20
high speeds?
=20

=20
Alan
=20

GC is making his point for low tows very convincingly - why is he
immediate=
ly being ripped, Chris? Preparing and steering into low tow at a safe
alti=
tude, say 300',

If you wait 'till 300 feet the majority of the risk of a fatal kitin
incident is already behind you, once past 400 feet there is just abou
enough height for the tow pilot to recover.

means to mentally and then practically pushing the stick
fo=
rward and then holding in the low tow position. That's the opposite
maneuv=
er of what's leading to kiting. Drifting upwards takes you into the
prop
w=
ash and again, it takes forward stick pressure to move into the saf
spot.
=
That feedback mechanism is correctly maintaining the intended safe spot
wh=
ile in the normal tow position only visual cues are being used.
I think I'll give the low tow a try, if ever that polar vortex over
Chicago=
makes like tree...
Herb


I've been aware of the Australian preference for low tow and the reason
for it for over 30 years. My own flight testing and experience lead me t
believe that it does not significantly reduce the probability of a kitin
accident.

On Saturday, February 22, 2014 5:14:59 PM UTC-5, firsys wrote:
Elevator power. I may have missed the comment , but has anyone experienced insufficient pitch down authority with full forward stick? Our club had an incident in very rough conditions. A PIK20B , belly hook, flown by a very experienced pilot, was forced to release as a snatch caused an uncontrollable pitchup. CG position not known, but the pilot was not large. I did a calculation ( 30 years ago) to see if this was plausible and indeed, if the CG was is near the aft limit with a PIK 20, the transient pitchup couple in a snatch can probably overpower full nose down elevator, thus initiating kiting. There a re probably many other sailplanes susceptable to this near the aft CG limit. John firth At 14:46 22 February 2014, Chris Rollings wrote: At 14:28 22 February 2014, wrote: On Saturday, February 22, 2014 1:58:28 AM UTC-6, GC wrote: On 22/02/2014 16:17, Alan wrote: =20 =20 =20 ...You don't get kiting if you fly normal "high" tow behind the towplan= e, =20 if you remain in control. =20 =20 If you don't remain in control, starting from low tow is not going t= o =20 make a lot of difference. =20 =20 =20 Experience (tens of thousands of aerotows) shows there is a enormous=20 =20 difference. The inadequate control and time to go from high tow to=20 =20 kiting is orders of magnitude different from that required to g from=20 =20 low tow to kiting. In fact, I've never heard of that eve happening.=20 =20 Even with low time students. Kiting from high tow, however, is=20 =20 apparently so common as to need a whole new system of electronic=20 =20 whizzbangery and gallons of bandwidth to stop. =20 =20 =20 If the tug has just lifted off, being in low tow sounds a bit diffic= ult, =20 but that would be a particularly hazardous time. =20 =20 =20 Yes. Liftoff is a time to be wary and we train accordingly.=20 =20 Nevertheless, all I can say is that low tow has prevented kiting=20 =20 accidents for many years. But don't take my word for it, keep this=20 =20 ridiculous discussion going with another screwball idea fo pivoting,=20 =20 autoswivelling, pitch-sensing, stick-following nonsense. =20 =20 =20 If the issue is serious - as it was in Australia - flying low to will=20 =20 solve it. If it isn't - see my previous post. =20 =20 =20 GC =20 =20 =20 =20 =20 As for automatic methods to mitigate the problem, perhaps the soluti= on =20 is not to modify tow planes, but to modify gliders. If the glider is =20 in a very high pitch attitude on tow, it might be a good time to automa= tically =20 release. =20 =20 Another modification might be to attach the tow rope to the top of t= he glider. =20 This would cause the tow force to pitch the glider down. =20 =20 =20 Is this more of a problem when folks try to tow a slow glider like a= 2-33 at =20 high speeds? =20 =20 Alan =20 GC is making his point for low tows very convincingly - why is he immediate= ly being ripped, Chris? Preparing and steering into low tow at a safe alti= tude, say 300', If you wait 'till 300 feet the majority of the risk of a fatal kitin incident is already behind you, once past 400 feet there is just abou enough height for the tow pilot to recover. means to mentally and then practically pushing the stick fo= rward and then holding in the low tow position. That's the opposite maneuv= er of what's leading to kiting. Drifting upwards takes you into the prop w= ash and again, it takes forward stick pressure to move into the saf spot. = That feedback mechanism is correctly maintaining the intended safe spot wh= ile in the normal tow position only visual cues are being used. I think I'll give the low tow a try, if ever that polar vortex over Chicago= makes like tree... Herb I've been aware of the Australian preference for low tow and the reason for it for over 30 years. My own flight testing and experience lead me t believe that it does not significantly reduce the probability of a kitin accident.

Dick Johnson wrote an article about this in about 1987. Combination of aft CG, low air speed, and snatch force can stall the glider tail. Rare but it is possible.
UH