poor lateral control on a slow tow?

I think that some of the postings above, when referring to tow
positions, are to some extent using different definitions of high and
low tow.

When I started my UK glider training in 1970, a "high" tow position in
the glider was level with, or even higher than, the tug. It was way
above the tug wake and prop wash. It was the normal position for
towing at my gliding club, and as I understood it at the time, the
same for most UK gliding club training.

A "low" tow position meant below the tug wake and propwash. It was
normally only used for long cross-country tows, and was allegedly
easier for the glider pilot, particularly in thermic conditions. I saw
it and experienced it also when dual tows were practised. The glider
on the short rope went to the high tow position, and the glider on the
long rope into low tow.

After a series of tug upset accidents, UK practice was changed. The
normal tow position now became a lower "high" tow, not far above the
tug wake and propwash. With a tug that was climbing well, this placed
the glider below the tug. That is now the norm, in the UK, as far as I
know. Consequently, with anything other than a very low powered tug, a
glider on tow often has its longitudinal axis horizontal, or even
inclined above the horizontal.

Chris N

On Jan 2, 6:53*pm, Chris Nicholas wrote:
I think that some of the postings above, when referring to tow
positions, are to some extent using different definitions of high and
low tow.

When I started my UK glider training in 1970, a "high" tow position in
the glider was level with, or even higher than, the tug. It was way
above the tug wake and prop wash. It was the normal position for
towing at my gliding club, and as I understood it at the time, the
same for most UK gliding club training.

*A "low" tow position meant below the tug wake and propwash. It was
normally only used for long cross-country tows, and was allegedly
easier for the glider pilot, particularly in thermic conditions. I saw
it and experienced it also when dual tows were practised. The glider
on the short rope went to the high tow position, and the glider on the
long rope into low tow.

After a series of tug upset accidents, UK practice was changed. The
normal tow position now became a lower "high" tow, not far above the
tug wake and propwash. With a tug that was climbing well, this placed
the glider below the tug. That is now the norm, in the UK, as far as I
know. Consequently, with anything other than a very low powered tug, a
glider on tow often has its longitudinal axis horizontal, or even
inclined above the horizontal.

Chris N

Yes...the upset accidents.......I watched from the ground as a tow
pilot got killed that way.....

Once you are above the wake, there is no reason you need to go
higher....and lots of reasons not to. But how did that "above the
towplane" stuff get started in the old days? I think that was a
misconception from the start!

I know a couple of glider ports around here were their answer is to
use low tow exclusively. While this does address the upset problem, I
feel that there are more disadvantages and dangers to low tow (for
routine tows) than for "normal" tow.

If a pilot can't keep a fairly steady tow position, above the wake and
below the tow plane, even if rough air, he needs more training.
Flying in low tow is not a substitute for pilot skill.

Cookie

On Jan 2, 6:09*pm, Bruce Hoult wrote:
On Jan 3, 12:01*am, Derek C wrote:

Actually the only totally reliable sysmptom of being stalled is that
the elevator will no longer raise the nose.

But that is neither necessary nor sufficient!

If you put enough weight in the front cockpit then there are plenty of
gliders where you reach the back stop while they are still flying just
fine.

Conversely, there are also plenty of gliders with sufficiently
powerful elevators that the wing can be stalled and you're mushing at
500+ fpm but you still have perfect control over the attitude of the
nose and can raise or lower it at will. Not to mention other aircraft
such as the F/A-18 which can be flown in perfect control with the wing
stalled at huge angles of attack.

I see in another post the definition:

Admittedly that is still a stall according to FAR23/25 definitions "a stall is produced, as shown by either:
(1) An uncontrollable downward pitching motion of the airplane;
(2) A downward pitching motion of the airplane that results from the activation of a stall avoidance device (for example, stick pusher); or
(3) The control reaching the stop."

Without having that document in front of me I will hazard a guess that
this is not a definition of a stall, but rather a definition of the
standards for what a pilot should do in order to pass a practical
flight examination. They're not going to fail him when the aircraft
fails to actually stall because the elevator reaches its stop first,
so they explicitly allow that as a signal that the pilot is allowed to
terminate the "stall" attempt and commence the stall recovery
procedure.

The only true definition of a stall is when the wing is at an angle of
attack such that a further increase of AoA produces a decrease of
lift.

*Usually* this will be accompanied by a large increase in drag such
that the combination of lift and drag is easily capable of supporting
the aircraft against gravity at a low speed and steep nose up descent
angle, but that may not necessarily always be the case and some
aircraft might speed up while stalled (perhaps at high altitude?).

The context of those stall definitions have to to with aircraft
certification. I think our towing discussion should stick with the
"aerodynamic" (AoA) definition.

As far a stalls on the practical test......the practical test
standards leaves a lot up to the examiner. I train my students for
what I call "baby stalls"....where you just creep up on it, and the
glider barely stalls, and the recovery is almost immediate. I also
train them for "monster stalls" where you really pull back hard, and
fast, resulting in a major nose up, followed by major nose down
attitude and a more "active" recovery needed.

The former is perhaps more realistic....in that in the real world
flying, the pilot might be more likely to stall this way. It also is
a good way to teach stall recognition and stall avoidence.

The later however shows more "plane handling", and more of the flight
envelope, almost more like an aerobatic maneuver.. Also shows no
"fear" of stalling. But unlikely to happen this way in the real
world.

I have sent students to examiners who like the stalls demonstrated in
the "baby" way, and others who like the "monster" way. I tell my
students to ask the examiner what he/she wants and perform the stall
and recovery accordingly.

During flight reviews, I find many pilots who, when I ask them to
demonstrate a stall and recovery, simply lift the nose up a bit, the
glider slows, and they push the nose back down.....never an actual
stall. To me this shows either fear, lack of understanding, or lack
of the "feel" of the glider. Thjen I demonstrate a "real stall" and
have then practice a bit.

Cookie

On Jan 2, 10:38*am, Andy wrote:
On Jan 1, 8:29*pm, "
wrote:

Then.....if the tow rope provides a forward and Downward pull........
(which was pretty much proven in an earlier discussion, by virtue of
the 'sag" in the rope, the angle at which the rope meets the
glider) * *then lift has to be GREATER than what you might at first
think. *

I was not part of that earlier discussion and I certainly don't accept
that conclusion.

All I have read here is that the D2, because of its very low angle of
incidence, may have a downward pull on the nose (and even here
downward would mean below the glider longitudinal axis, not
necessarily below the horizon). *I'm quite sure that my ASW 28 being
towed on the CG hook has no downward force on the nose.

When I do tow in gliders with a nose hook I'm quite sure there is no
significant downward pull from the rope. *Maybe it all depends on what
you call high tow. *I've seen may pilots tow tens of feet higher than
I regard as normal high tow.

Andy

Which part don't you accept? The part about rope pulling downward, or
the part about the required lift being greater if/when it does?

In the previous discussion we all seemed to agree that the tow rope
has a consicerable sag during tow, and that the pulling force of the
rope acts in the direction of the rope meeting the tow hook, which is
not along the long. axis of the glider, and not parallel to the
direction of flight of the glider.

Now, how significant? I dunno!

With a mid-mounted wing glider and a nose hook, the forces of the tow
rope and the drag all run pretty close to the CG.....so probably
little to no pitching effect.......On a 2-33 for instance, where the
tow hook is mounted low, and the wing is high, I believe there is a
nose up pitching moment created, and in fact the 2-33 needs full
forward trim and considerable forward stick pressure on tow. Where a
mid wing nose hook glider flys nicely with about neutral trim and
little stick force if any.

But if we were to agree that the tow rope does not pull in the
dircetion of flight of the glider, and in fact pulls somewhat
"downward" compared to the direction of flight, we need to balance
this force......the only way to balance this force is for lift to
become greater, since weight, and drag remain the same. More lift
comes from more AoA.

I am not saying this is the only factor in this mushy tow deal, but I
think it contributes along with the other factors mentioned.


Cookie

On 1/2/2011 2:35 PM, sisu1a wrote:
I know that you have some 'persons of size' out in the States, but I
have never flown a glider that could not stalled in straight flight

Not that this adds to the main discussion, but...

160lb (normal sized) pilot here... my SZD-59 couldn't be stalled
straight ahead without 'tricking' it (ease nose up till *near stall
and yank the stick for the last bit of travel). No mods were done to
plane to cause this, and a reliable W&B with me in it determined C/G
to be at 37%, well within the limits (it's JAR22 cert'd...). This is
actually common with this ship as well as the Jantar Std3 from which
it's derived. I added 5.5lbs to the tail via a brass/lead tailwheel
and now fly it at 50%, where it flies much nicer, with an honest (and
predictable) stall and a more usable trim range.

Wow, what's the minimum cockpit load for the glider? Must be less than
140 pounds!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

a reliable W&B with me in it determined C/G to be at 37%

Wow, what's the minimum cockpit load for the glider? Must be less than
140 pounds!

close...

Min -143lb
Max -256lb

-Paul

On Jan 2, 5:33*pm, "
wrote:
On Jan 2, 6:53*pm, Chris Nicholas wrote:



I think that some of the postings above, when referring to tow
positions, are to some extent using different definitions of high and
low tow.

When I started my UK glider training in 1970, a "high" tow position in
the glider was level with, or even higher than, the tug. It was way
above the tug wake and prop wash. It was the normal position for
towing at my gliding club, and as I understood it at the time, the
same for most UK gliding club training.

*A "low" tow position meant below the tug wake and propwash. It was
normally only used for long cross-country tows, and was allegedly
easier for the glider pilot, particularly in thermic conditions. I saw
it and experienced it also when dual tows were practised. The glider
on the short rope went to the high tow position, and the glider on the
long rope into low tow.

After a series of tug upset accidents, UK practice was changed. The
normal tow position now became a lower "high" tow, not far above the
tug wake and propwash. With a tug that was climbing well, this placed
the glider below the tug. That is now the norm, in the UK, as far as I
know. Consequently, with anything other than a very low powered tug, a
glider on tow often has its longitudinal axis horizontal, or even
inclined above the horizontal.

Chris N

Yes...the upset accidents.......I watched from the ground as a tow
pilot got killed that way.....

Once you are above the wake, there is no reason you need to go
higher....and lots of reasons not to. * But how did that "above the
towplane" stuff *get started in the old days? * I think that was a
misconception from the start!

I know a couple of glider ports around here were their answer is to
use low tow exclusively. *While this does address the upset problem, I
feel that there are more disadvantages and dangers to low tow (for
routine tows) than for "normal" tow.

If a pilot can't keep a fairly steady tow position, above the wake and
below the tow plane, even if rough air, he needs more training.
Flying in low tow is not a substitute for pilot skill.

Cookie

Where was that?

Answer me off group, okay?

Frank Whiteley

On Jan 3, 4:57*am, Frank Whiteley wrote:
On Jan 2, 5:33*pm, "
wrote:





On Jan 2, 6:53*pm, Chris Nicholas wrote:

I think that some of the postings above, when referring to tow
positions, are to some extent using different definitions of high and
low tow.

When I started my UK glider training in 1970, a "high" tow position in
the glider was level with, or even higher than, the tug. It was way
above the tug wake and prop wash. It was the normal position for
towing at my gliding club, and as I understood it at the time, the
same for most UK gliding club training.

*A "low" tow position meant below the tug wake and propwash. It was
normally only used for long cross-country tows, and was allegedly
easier for the glider pilot, particularly in thermic conditions. I saw
it and experienced it also when dual tows were practised. The glider
on the short rope went to the high tow position, and the glider on the
long rope into low tow.

After a series of tug upset accidents, UK practice was changed. The
normal tow position now became a lower "high" tow, not far above the
tug wake and propwash. With a tug that was climbing well, this placed
the glider below the tug. That is now the norm, in the UK, as far as I
know. Consequently, with anything other than a very low powered tug, a
glider on tow often has its longitudinal axis horizontal, or even
inclined above the horizontal.

Chris N

Yes...the upset accidents.......I watched from the ground as a tow
pilot got killed that way.....

Once you are above the wake, there is no reason you need to go
higher....and lots of reasons not to. * But how did that "above the
towplane" stuff *get started in the old days? * I think that was a
misconception from the start!

I know a couple of glider ports around here were their answer is to
use low tow exclusively. *While this does address the upset problem, I
feel that there are more disadvantages and dangers to low tow (for
routine tows) than for "normal" tow.

If a pilot can't keep a fairly steady tow position, above the wake and
below the tow plane, even if rough air, he needs more training.
Flying in low tow is not a substitute for pilot skill.

Cookie

Where was that?

Answer me off group, okay?

Frank Whiteley- Hide quoted text -

- Show quoted text -

The correct position for 'high tow' is just a few feet above the tug
propwash. If you are not sure, ease the glider down until you feel the
turbulence and then ease back up a few feet. The appearance of the tug
and its position relative to the horizon will depend on its angle of
climb, and for that matter the nature of the horizon because a
mountain range is somewhat higher than a plain or a seascape. When the
tug levels out on a cross-country retrieve the correct high tow
position looks a lot higher than the normal climb position.

Derek C (UK Instructor)

On Jan 2, 6:14*pm, "
wrote:
On Jan 2, 10:38*am, Andy wrote:



On Jan 1, 8:29*pm, "
wrote:

Then.....if the tow rope provides a forward and Downward pull........
(which was pretty much proven in an earlier discussion, by virtue of
the 'sag" in the rope, the angle at which the rope meets the
glider) * *then lift has to be GREATER than what you might at first
think. *

I was not part of that earlier discussion and I certainly don't accept
that conclusion.

All I have read here is that the D2, because of its very low angle of
incidence, may have a downward pull on the nose (and even here
downward would mean below the glider longitudinal axis, not
necessarily below the horizon). *I'm quite sure that my ASW 28 being
towed on the CG hook has no downward force on the nose.

When I do tow in gliders with a nose hook I'm quite sure there is no
significant downward pull from the rope. *Maybe it all depends on what
you call high tow. *I've seen may pilots tow tens of feet higher than
I regard as normal high tow.

Andy

Which part don't you accept? *The part about rope pulling downward, or
the part about the required lift being greater if/when it does?

In the previous discussion we all seemed to agree that the tow rope
has a consicerable sag during tow, and that the pulling force of the
rope acts in the direction of the rope meeting the tow hook, which is
not along the long. axis of the glider, and not parallel to the
direction of flight of the glider.

Now, how significant? *I dunno!

With a mid-mounted wing glider and a nose hook, the forces of the tow
rope and the drag all run pretty close to the CG.....so probably
little to no pitching effect.......On a 2-33 for instance, where the
tow hook is mounted low, and the wing is high, I believe there is a
nose up pitching moment created, and in fact the 2-33 needs full
forward trim and considerable forward stick pressure on tow. *Where a
mid wing nose hook glider flys nicely with about neutral trim and
little stick force if any.

But if we were to agree that the tow rope does not pull in the
dircetion of flight of the glider, and in fact pulls somewhat
"downward" compared to the direction of flight, we need to balance
this force......the only way to balance this force is for lift to
become greater, since weight, and drag remain the same. *More lift
comes from more AoA.

I am not saying this is the only factor in this mushy tow deal, but I
think it contributes along with the other factors mentioned.

Cookie

Maybe the disagreement is only what is meant by downwards. I disagree
that for a glider towing just above the wake, using a CG hook, and
with the tug in a full power climb at normal tow speed, that the rope
applies any force to the glider in a direction below the local
horizontal plane. All the qualifiers above describe a normal tow for
me.

Andy

At 23:09 02 January 2011, Bruce Hoult wrote:
On Jan 3, 12:01=A0am, Derek C wrote:
Actually the only totally reliable sysmptom of being stalled is that
the elevator will no longer raise the nose.

But that is neither necessary nor sufficient!

If you put enough weight in the front cockpit then there are plenty of
gliders where you reach the back stop while they are still flying just
fine.

Conversely, there are also plenty of gliders with sufficiently
powerful elevators that the wing can be stalled and you're mushing at
500+ fpm but you still have perfect control over the attitude of the
nose and can raise or lower it at will. Not to mention other aircraft
such as the F/A-18 which can be flown in perfect control with the wing
stalled at huge angles of attack.

I see in another post the definition:

Admittedly that is still a stall according to FAR23/25 definitions "a
sta=
ll is produced, as shown by either:
(1) An uncontrollable downward pitching motion of the airplane;
(2) A downward pitching motion of the airplane that results from the
acti=
vation of a stall avoidance device (for example, stick pusher); or
(3) The control reaching the stop."

Without having that document in front of me I will hazard a guess that
this is not a definition of a stall, but rather a definition of the
standards for what a pilot should do in order to pass a practical
flight examination. They're not going to fail him when the aircraft
fails to actually stall because the elevator reaches its stop first,
so they explicitly allow that as a signal that the pilot is allowed to
terminate the "stall" attempt and commence the stall recovery
procedure.

The only true definition of a stall is when the wing is at an angle of
attack such that a further increase of AoA produces a decrease of
lift.

*Usually* this will be accompanied by a large increase in drag such
that the combination of lift and drag is easily capable of supporting
the aircraft against gravity at a low speed and steep nose up descent
angle, but that may not necessarily always be the case and some
aircraft might speed up while stalled (perhaps at high altitude?).


Exactly - FAA 'legal' definitions of stall are aimed at defining speeds
for certification purposes. Most recently, more use has been made of the
'1g stall speed', which is the slowest speed you can fly and still
maintain level flight (obviously a bit tricky for a glider!) - which
corresponds to your definition of teh AoA at which a further increase
produces a decrease of lift (= maximum lift). The problem for the
regulators is that some (many?) aircraft become uncontrollable one way or
another before you get to this point - which is why stall such a bl*^dy
difficult thing to define precisely