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high tow vs low tow



 
 
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  #11  
Old February 25th 19, 03:54 PM posted to rec.aviation.soaring
Cookie
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Posts: 152
Default high tow vs low tow

You've noted that many fly low tow "too low"

I've noted that many fly high tow "too high"

Hmmmm?



Cookie




On Monday, February 25, 2019 at 8:54:59 AM UTC-5, wrote:
On Sunday, February 24, 2019 at 10:27:25 PM UTC-5, Steve Koerner wrote:
As a US pilot, I've flown low tow a few times but mostly just high tow as that is the convention here. I'm wondering what all of the trade-offs are by the two methods? Might it be time to reconsider this?

As pointed out on another thread, low tow would seem to be safer against the problem of glider kiting up to overpower the tugs up elevator. I'm wondering if it's ever possible for a low tow glider to go too low and overpower the tugs down elevator?

Also, how does low tow compare in the other common dangerous towing situation wherein the tug flys too slow for a highly ballasted glider? My own experience with a seriously too slow tug is that I end up falling to low tow whether I like it or not.

Has anyone done a lot of tows both ways and have reasons as to which way is better?


I've done something over 20,000 flights at both ends, 12k or so at the back and something over 8k at the front.
Properly flown, as high as possible without being in the wake, the glider is very closely aligned with the thrust line of the tug and has almost no effect on trim.
Flown too low, the glider pilot can have a poorer view of the horizon.
Being a bit high is obvious.
The rope wrapping hazard happens if there is slack caused by a fairly quick, big descent. I have never witnessed this happening in operations I have been involved with.
We tested the "pull the tail down" risk and could not accomplish it. The angles don't work. In trying this we had our Cub down to below 45 MPH with the glider behind hanging low. It was more stable with the glider on at that speed.
My experience is that low is easier to teach and do at the beginning because the view is a bit better and the wake is not anywhere near as much of an issue.
Get slack- Move to the side to take it out, just like high(normal?) tow.
Rope will hit the glider. Could happen if way too low when tug releases it. If the glider is in proper position when releasing the rope doesn't go much up or down. If the tug releases the rope drops below and behind and probably, but not surely back releases.
Rope will wrap around the glider- I have yet to figure out how a rope can go upwind against a 60 mph headwind.
The rope will scratch my belly when using a CG hook. No scratches on my ships in 40+ years of low tow.
Most training, from my experience, teaches pilots to fly too low.
If one wants to get better at this, a couple dual flights with an experienced instructor can be useful.
Also note that many tugs have mirrors set up such that the tow pilot can't see the glider in low tow.
Tell your tow pilot what you plan to do. Trim settings are different so he or she may want to adjust.
To finish. Both options can be done safely. I believe low tow is more easily done safely.
Flame suit on.
UH


  #12  
Old February 25th 19, 04:00 PM posted to rec.aviation.soaring
Cookie
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Posts: 152
Default high tow vs low tow

Only one "freak" incident I saw where low tow may have caused an "issue"

Well actually it was a high tow gone bad...

It was a rough day...the glider pilot was seemingly attempting to fly "high" tow.

For some reason, the glider went low....the rope broke...

The rope blew back over the glider and made a complete 360 "wrap" around the glider fuselage....the glider landed with the rope still wrapped around it. The glider canopy had a long "burn mark" where the rope slid along it.

Luckily the rope did not get wedged into an aileron gap or tail surface.

Cookie






On Monday, February 25, 2019 at 8:54:59 AM UTC-5, wrote:
On Sunday, February 24, 2019 at 10:27:25 PM UTC-5, Steve Koerner wrote:
As a US pilot, I've flown low tow a few times but mostly just high tow as that is the convention here. I'm wondering what all of the trade-offs are by the two methods? Might it be time to reconsider this?

As pointed out on another thread, low tow would seem to be safer against the problem of glider kiting up to overpower the tugs up elevator. I'm wondering if it's ever possible for a low tow glider to go too low and overpower the tugs down elevator?

Also, how does low tow compare in the other common dangerous towing situation wherein the tug flys too slow for a highly ballasted glider? My own experience with a seriously too slow tug is that I end up falling to low tow whether I like it or not.

Has anyone done a lot of tows both ways and have reasons as to which way is better?


I've done something over 20,000 flights at both ends, 12k or so at the back and something over 8k at the front.
Properly flown, as high as possible without being in the wake, the glider is very closely aligned with the thrust line of the tug and has almost no effect on trim.
Flown too low, the glider pilot can have a poorer view of the horizon.
Being a bit high is obvious.
The rope wrapping hazard happens if there is slack caused by a fairly quick, big descent. I have never witnessed this happening in operations I have been involved with.
We tested the "pull the tail down" risk and could not accomplish it. The angles don't work. In trying this we had our Cub down to below 45 MPH with the glider behind hanging low. It was more stable with the glider on at that speed.
My experience is that low is easier to teach and do at the beginning because the view is a bit better and the wake is not anywhere near as much of an issue.
Get slack- Move to the side to take it out, just like high(normal?) tow.
Rope will hit the glider. Could happen if way too low when tug releases it. If the glider is in proper position when releasing the rope doesn't go much up or down. If the tug releases the rope drops below and behind and probably, but not surely back releases.
Rope will wrap around the glider- I have yet to figure out how a rope can go upwind against a 60 mph headwind.
The rope will scratch my belly when using a CG hook. No scratches on my ships in 40+ years of low tow.
Most training, from my experience, teaches pilots to fly too low.
If one wants to get better at this, a couple dual flights with an experienced instructor can be useful.
Also note that many tugs have mirrors set up such that the tow pilot can't see the glider in low tow.
Tell your tow pilot what you plan to do. Trim settings are different so he or she may want to adjust.
To finish. Both options can be done safely. I believe low tow is more easily done safely.
Flame suit on.
UH


  #13  
Old February 25th 19, 04:09 PM posted to rec.aviation.soaring
Cookie
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Posts: 152
Default high tow vs low tow

You make some very good arguments in favor of low tow....Does that mean you win the overall argument?...I dunno?..most glider ops in USA still use high tow. ( guess they have their reasons?)

My concern about all of this tow position stuff is this....
Does using low tow simply mask the "symptom", the larger problem of not-so-proficient glider pilots on tow?

In the incidents I've seen or heard about... It was always the glider pilots lack of skill, or inattention, which caused the problem...the root cause was the glider pilot, not the tow position...

That being said....If I were a tow pilot (I'm not)...and I were towing somebody in a glider, who I had no idea of his ability, experience, etc....I would be much happier if he flew low position...


Cookie




On Monday, February 25, 2019 at 8:54:59 AM UTC-5, wrote:
On Sunday, February 24, 2019 at 10:27:25 PM UTC-5, Steve Koerner wrote:
As a US pilot, I've flown low tow a few times but mostly just high tow as that is the convention here. I'm wondering what all of the trade-offs are by the two methods? Might it be time to reconsider this?

As pointed out on another thread, low tow would seem to be safer against the problem of glider kiting up to overpower the tugs up elevator. I'm wondering if it's ever possible for a low tow glider to go too low and overpower the tugs down elevator?

Also, how does low tow compare in the other common dangerous towing situation wherein the tug flys too slow for a highly ballasted glider? My own experience with a seriously too slow tug is that I end up falling to low tow whether I like it or not.

Has anyone done a lot of tows both ways and have reasons as to which way is better?


I've done something over 20,000 flights at both ends, 12k or so at the back and something over 8k at the front.
Properly flown, as high as possible without being in the wake, the glider is very closely aligned with the thrust line of the tug and has almost no effect on trim.
Flown too low, the glider pilot can have a poorer view of the horizon.
Being a bit high is obvious.
The rope wrapping hazard happens if there is slack caused by a fairly quick, big descent. I have never witnessed this happening in operations I have been involved with.
We tested the "pull the tail down" risk and could not accomplish it. The angles don't work. In trying this we had our Cub down to below 45 MPH with the glider behind hanging low. It was more stable with the glider on at that speed.
My experience is that low is easier to teach and do at the beginning because the view is a bit better and the wake is not anywhere near as much of an issue.
Get slack- Move to the side to take it out, just like high(normal?) tow.
Rope will hit the glider. Could happen if way too low when tug releases it. If the glider is in proper position when releasing the rope doesn't go much up or down. If the tug releases the rope drops below and behind and probably, but not surely back releases.
Rope will wrap around the glider- I have yet to figure out how a rope can go upwind against a 60 mph headwind.
The rope will scratch my belly when using a CG hook. No scratches on my ships in 40+ years of low tow.
Most training, from my experience, teaches pilots to fly too low.
If one wants to get better at this, a couple dual flights with an experienced instructor can be useful.
Also note that many tugs have mirrors set up such that the tow pilot can't see the glider in low tow.
Tell your tow pilot what you plan to do. Trim settings are different so he or she may want to adjust.
To finish. Both options can be done safely. I believe low tow is more easily done safely.
Flame suit on.
UH

  #14  
Old February 25th 19, 04:11 PM posted to rec.aviation.soaring
Steve Koerner
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Posts: 430
Default high tow vs low tow

Hank -

Do you have any thoughts on the separate problem of tow too slow with a ballasted glider? Wondering which might be better for that big problem. Maybe that problem is the same either way.

Second, I'm wondering about how glider lift off occurs for a low tow. Do you typically lift off with the towplane then immediately transition to low position or does the glider attempt to hold it down on the runway until the sight picture is correct for low tow?
  #15  
Old February 25th 19, 05:45 PM posted to rec.aviation.soaring
[email protected]
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Posts: 2,124
Default high tow vs low tow

On Monday, February 25, 2019 at 10:09:35 AM UTC-5, Cookie wrote:
You make some very good arguments in favor of low tow....Does that mean you win the overall argument?...I dunno?..most glider ops in USA still use high tow. ( guess they have their reasons?)

My concern about all of this tow position stuff is this....
Does using low tow simply mask the "symptom", the larger problem of not-so-proficient glider pilots on tow?

In the incidents I've seen or heard about... It was always the glider pilots lack of skill, or inattention, which caused the problem...the root cause was the glider pilot, not the tow position...

That being said....If I were a tow pilot (I'm not)...and I were towing somebody in a glider, who I had no idea of his ability, experience, etc....I would be much happier if he flew low position...


Cookie


Not trying to win anything but if I can clear up some misinformation it could be a good thing. Knowledge is important and commonly limited.

Low tow may mask proficiency issues a bit simply because it is a bit easier to do- my experience.
I completely agree that proficiency is a major concern. How many things do we do only 20 or 30 times a year that can kill somebody if we do it wrong?
The point Chris R made about rope length is also very important.Short ropes make position errors more critical.
UH
  #16  
Old February 25th 19, 05:57 PM posted to rec.aviation.soaring
[email protected]
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Posts: 2,124
Default high tow vs low tow

On Monday, February 25, 2019 at 10:11:36 AM UTC-5, Steve Koerner wrote:
Hank -

Do you have any thoughts on the separate problem of tow too slow with a ballasted glider? Wondering which might be better for that big problem. Maybe that problem is the same either way.

Second, I'm wondering about how glider lift off occurs for a low tow. Do you typically lift off with the towplane then immediately transition to low position or does the glider attempt to hold it down on the runway until the sight picture is correct for low tow?


Too slow is obviously a problem in either position- duh! That said the first thing most will feel in high tow is poorer position control when sinking into the wake. Control isn't as much an issue in low tow but it still feels bad.
In a flapped ship adding some more flap can get a bit of lift without pulling the leading edge up and reducing control.
Ships with no flaps are just screwed.
On takeoff I teach:
Lift off normally and get stable at a comfortable height, say 6- 8 feet.
Hold that position as the tug accelerates and lifts off.
When the tug starts to climb hold the glider down a bit so the tug outclimbs the glider . The glider stays in ground effect and the tug wake is dissipated.
As the tug wake starts to be above the glider smoothly transition to climb in the low tow position. Avoid doing this late and then having to climb hard to catch up.
Easier to do than describe but it feels very odd to someone not famailiar.
UH
  #17  
Old February 25th 19, 05:59 PM posted to rec.aviation.soaring
Tango Eight
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Posts: 962
Default high tow vs low tow

On Monday, February 25, 2019 at 11:45:25 AM UTC-5, wrote:
On Monday, February 25, 2019 at 10:09:35 AM UTC-5, Cookie wrote:
You make some very good arguments in favor of low tow....Does that mean you win the overall argument?...I dunno?..most glider ops in USA still use high tow. ( guess they have their reasons?)

My concern about all of this tow position stuff is this....
Does using low tow simply mask the "symptom", the larger problem of not-so-proficient glider pilots on tow?

In the incidents I've seen or heard about... It was always the glider pilots lack of skill, or inattention, which caused the problem...the root cause was the glider pilot, not the tow position...

That being said....If I were a tow pilot (I'm not)...and I were towing somebody in a glider, who I had no idea of his ability, experience, etc....I would be much happier if he flew low position...


Cookie


Not trying to win anything but if I can clear up some misinformation it could be a good thing. Knowledge is important and commonly limited.

Low tow may mask proficiency issues a bit simply because it is a bit easier to do- my experience.
I completely agree that proficiency is a major concern. How many things do we do only 20 or 30 times a year that can kill somebody if we do it wrong?
The point Chris R made about rope length is also very important.Short ropes make position errors more critical.
UH


Jus' for clarity, the only bits I quoted Chris on are in quotes. I get the blame for everything else in that post.

T8
  #18  
Old February 25th 19, 07:52 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Posts: 1,383
Default high tow vs low tow

OK, I will start with.....I am biased to UH, he was one of my early instructors and we have other connections.

The "only" time I see an issue with low tow is with a VERY high wind gradient and someone being waaaayyyyyy too low near the ground.
The relevant airspeed of the tug vs. the glider (especially on a weaker tug) may put the glider in a poor position speed wise.

I will say, I have towed out of our field on very gusty days with, about a 45* cross wind, near gross weight (say, a ASW-20 A or C, so, about 9lbs/sqft.).
Yes, it ''twas sporty down low", why not? Big cross wind, over trees, higher wingloading, etc.

I have had rope breaks and a few TP dumped ropes while low tow, the rope just drops below the glider, try to drop a broken rope over the field on the grass.

As to the towpilots, what I have heard is that low tow allows them to trim a climb in their ship, thus less tiring over a day. High tow is usually outside the trim limits, thus always using your arms to maintain a climb pitch.. Part of this is a correct low tow puts the glider basically on the pitch line from tug spinner and down the rope to the glider...

I remember decades ago in upstate NY at a contest. Summer day, ballast, weak towplane (leaving site and tug out, not trying to slam the site). I started in high tow. We were attempting to do circles close to the field to clear terrain, I ended up in low tow since I was just hanging on. It appeared that it helped climb a bit, but I was not happy.

In general, the "perfect world" done wrong/incorrect still sucks and may be dangerous.

At our place, we teach both.
Other places, we do as they do, but if it gets bad, we may fall back to what we have more time with.

A search on RAS will likely pop up multiple threads with the same basic question, which tow is better?

I guess this discussion is akin to, "what contest rules should we use?", sheesh......
  #19  
Old February 25th 19, 08:30 PM posted to rec.aviation.soaring
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Posts: 580
Default high tow vs low tow

I flew at Valley Soaring for a while and did low tow. Worked fine. The only negative I heard was that the glider appears to be lower in the first critical phase of climb so it takes longer to get to the 200' safe 180 turnaround point. But I've also heard that low tow is more efficient because there's less/no trim drag from the towplane using up elevator to keep the tail down and therefore climbs faster. So perhaps it's a wash.

I'll move into low tow on cross-country aerotows if I've briefed the tow pilot or can communicate with him/her because it seems easier to hold position.

Yes, kiting a glider is going to upset the towplane regardless of the tow position. But at least if you're in low tow, you'll feel the wake as you pop up thru it, which provides an alert that might help prevent situations as was described in the NTSB report where the glider pilot may have taken his eye off the towplane for a few seconds.

Chip Bearden
  #20  
Old February 25th 19, 08:55 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Posts: 1,383
Default high tow vs low tow

To add a tiny bit, some high tow proponents have said, "I want to clear low obstructions, thus I fly high tow....!"
I usually counter with, if the towplane clears, there is typically enough energy for the glider to clear, even from low tow. Also, as Chip stated (and I agree), low tow does not require as much parasitic drag from the towplane tail to maintain a climb angle, thus more efficient. This also means the towplane is marginally higher clearing an obstacle, thus more energy for the sailplane to clear even if too low doing low tow.
Again, big wind gradient can be a negative factor if too low.

We break ground, sit in ground effect (pretty much the most efficient place for any aircraft), let towplane accelerate, break ground, then establish a climb. Once the sight picture looks good, the sailplane starts a climb.
Turbulence from towplane wing wash/vortex is essentially "0" since that does not really form until some climb is done. By the time it starts, the sailplane should be starting up.

As stated before, any method done wrong/incorrect is still poor.
 




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