high tow vs low tow

On Wednesday, February 27, 2019 at 7:45:46 AM UTC-5, Tango Eight wrote:
On Tuesday, February 26, 2019 at 10:16:56 PM UTC-5, Ramy wrote:
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

One reason I will never do this in a ballasted glider is wind shear.

Low tow increases the glider pilot's vulnerability to a slow tow.

best,
Evan

If excessively low on tow wind shear can be a factor. Properly flown, my experience is that it is not.
Possibly you can explain your second contention. Slow is slow no matter which position you are in.
UH

On Wednesday, February 27, 2019 at 8:52:36 AM UTC-5, wrote:
On Wednesday, February 27, 2019 at 7:45:46 AM UTC-5, Tango Eight wrote:
On Tuesday, February 26, 2019 at 10:16:56 PM UTC-5, Ramy wrote:
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

One reason I will never do this in a ballasted glider is wind shear.

Low tow increases the glider pilot's vulnerability to a slow tow.

best,
Evan

If excessively low on tow wind shear can be a factor. Properly flown, my experience is that it is not.
Possibly you can explain your second contention. Slow is slow no matter which position you are in.
UH

I think your argument here is that "a properly flown low tow doesn't hurt much." In which case my point has been made, yes?

T8

I would say, a "properly flown tow" doesn't hurt much.
There are issues in ANY formation flying, a glider aero tow is formation flying.
Do we at least agree on that (that an aero tow is formation flying)?

Any aero tow (or even winch launch, etc.) has some risk.
I have seen people fly low tow as a "new thing" when they normally did high tow. Common issue is waiting late to climb with the towplane.

As I stated earlier, this discussion has been hashed out on RAS before as well as other places.
To me, this is a "no win" for anyone.
We train for both, which is good.
I normally fly whatever tow is "usual" at a site.

While I agree that "slow is slow", I think it's much better to be in
high tow position and be able to sink to low tow if the tug gets too
slow.Â* I've been dangling on the end of a slow rope with a full load and
had to start dumping while on tow.Â* It's not comfortable.

Of course that proper thing is to not get slow and I blame this on an
inexperienced tuggie who strives for a good climb rate at the expense of
the glider.

On 2/27/2019 6:52 AM, wrote:
On Wednesday, February 27, 2019 at 7:45:46 AM UTC-5, Tango Eight wrote:
On Tuesday, February 26, 2019 at 10:16:56 PM UTC-5, Ramy wrote:
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
One reason I will never do this in a ballasted glider is wind shear.

Low tow increases the glider pilot's vulnerability to a slow tow.

best,
Evan
If excessively low on tow wind shear can be a factor. Properly flown, my experience is that it is not.
Possibly you can explain your second contention. Slow is slow no matter which position you are in.
UH

--
Dan, 5J

On Wednesday, February 27, 2019 at 9:30:18 AM UTC-8, Dan Marotta wrote:
While I agree that "slow is slow", I think it's much better to be in
high tow position and be able to sink to low tow if the tug gets too
slow.Â* I've been dangling on the end of a slow rope with a full load and
had to start dumping while on tow.Â* It's not comfortable.

Of course that proper thing is to not get slow and I blame this on an
inexperienced tuggie who strives for a good climb rate at the expense of
the glider.

On 2/27/2019 6:52 AM, wrote:
On Wednesday, February 27, 2019 at 7:45:46 AM UTC-5, Tango Eight wrote:
On Tuesday, February 26, 2019 at 10:16:56 PM UTC-5, Ramy wrote:
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
One reason I will never do this in a ballasted glider is wind shear.

Low tow increases the glider pilot's vulnerability to a slow tow.

best,
Evan
If excessively low on tow wind shear can be a factor. Properly flown, my experience is that it is not.
Possibly you can explain your second contention. Slow is slow no matter which position you are in.
UH

--
Dan, 5J

I received my glider training in Minden. Some of you might have heard rotor can be a real thing there. From day one I was conditioned, if I ever lost sight of tow plane to release immediately, and I have! Other than training the only low tow I have been in was back in the 90's we (local not Minden) had a string of very poorly (not) trained tow pilots. It was so bad pilots were making signs that said "Fast tow". To this day there are no radios in the local tugs I was flying a loaded ASW-24 and was so slow and low that the tow rope was basically just inched in front of the leading edge (CG Hook). Thank goodness for the Nixon/Murray water system, dumps fast. Since this tow pilot was towing away from field low and slow, I to wait until I thought I could make it back to airport before I released. On the ground I spoke to the tuggie. He had no clue gliders carried water ballast. I held up a sign that said I had water ballast before the tow he thought that was drinking water! That same day he towed a 1-26 at 70 knots straight away from airport with no mind of return to airport for the 1-26 driver. Since I got back into gliding our tow pilots are some of the best pilots of anything I have ever met! Perhaps all this boils down to improper initial training. If I was sleeping, dreaming of being on tow, and in the dream lost sight of tow plane, I would still be pulling for that release. Of course I don't mess with anything else on tow because I have been trained while flying tow, that is the only thing you should be doing!

In Minden before each training session we briefed the tow and we briefed immediate release if lost sight. It was much more than cursory, or something we mentioned a few times, it was part of every before flight emergency procedure spoken outloud.

On Tuesday, February 26, 2019 at 10:16:56 PM UTC-5, Ramy wrote:
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

My experience is that the slightly improved takeoff performance puts the glider at an equal to slightly higher height shortly after transition to the tug climbing attitude.
UH

And I think this is an example of not being properly trained in low tow.
You are in ground effect until the towplane reaches the proper sight view in front of the glider which is not too far off the ground.
If you are looking up at the bottom of the towplane, you waited too long. This would accentuate the negative effect of wind gradient.

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......

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

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.