high tow vs low tow

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

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

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

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

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

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

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?

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

Sounds to me that this method of staying low in ground effect for low tow position will increase the time we spend in the dangerous zone below 200 feet, in addition to transitioning through the wake while low and slow. Personally I prefer to spend as less time as possible down low, and would rather transition to low tow position at safe altitude and safe speed. Especially at high density altitude such as we have in the west, fully ballasted combined with not so powerful towplane, the last thing I would want is to purposely stay in ground effect at the end of the runway while the tow plane slowly climbs higher. I never tried this, so maybe it is not as bad as i think it is.

Ramy

In Australia we now transition higher, I use around 200’ before going into low tow.
I have flown high tow at many overeas comps and still find low tow much more stable.
The only time I fly high tow at home is on long cross country tows where I also pull the gear up (nose hook only!) and let the tug pilot accelerate in level flight.
The issue of tug pilots ignoring what type and weight of glider behind them is much more of a safety issue than the simple high/low equasion.
(I am a tug pilot too!)
Tom