high tow vs low tow

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

Some gliders have the CG hook just forward of the gear doors.Â* I always
raised the gear in my LAK-17a on tow (at a safe altitude, of course) to
get a marginal improvement in climb rate.Â* Everyone says that low tow is
best for XC tows.Â* I've only been on the front end of the rope on an XC
tow, so I can't address the back end.

On 2/27/2019 12:02 AM, wrote:
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

--
Dan, 5J

On Tuesday, February 26, 2019 at 11:02:17 PM UTC-8, wrote:
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.

Weird, because long cross country tows is exactly the one time the rest of us use low tow!

The height difference between a good low tow and a good high tow isn't much anyway. Twenty feet / six metres maybe? Maybe less.

Yes!

Above the wake during a level (not climbing) tow, will place the glider quite a bit above the tow plane...not a good place to be...

Low tow during level tow, just barely below the wake will place the glider only very slightly lower than the tow plane...a good place to be...

So...anybody winning the argument yet? LOL


Cookie



Weird, because long cross country tows is exactly the one time the rest of us use low tow!

The height difference between a good low tow and a good high tow isn't much anyway. Twenty feet / six metres maybe? Maybe less.

You do realise high and low refer to the slipstream don’t you!?

Speed of tow is the most important thing, I have not had so much flying in the USA but it is a problem at comps here when tug pilots used to towing slow two seaters and empty older gliders and turn up at a comp to tow heavily ballasted gliders. I understand there have been accidents over there from this.
ASGs and JSs need more speed than 2-22s but some tug pilots cannot seem to see that!

I have always believed the wake basically goes DOWN behind the tow plane, being compressed, i.e. heavier, air, and/or maybe for other reasons. I don't remember feeling any wake turbulence just following the tow plane at the same height, climbing or level flight.

On Wednesday, February 27, 2019 at 2:21:01 PM UTC-8, Cookie wrote:
Yes!

Above the wake during a level (not climbing) tow, will place the glider quite a bit above the tow plane...not a good place to be...

Low tow during level tow, just barely below the wake will place the glider only very slightly lower than the tow plane...a good place to be...

So...anybody winning the argument yet? LOL


Cookie

On Wed, 27 Feb 2019 18:12:56 -0800, Tom BravoMike wrote:

I have always believed the wake basically goes DOWN behind the tow
plane, being compressed, i.e. heavier, air, and/or maybe for other
reasons. I don't remember feeling any wake turbulence just following the
tow plane at the same height, climbing or level flight.

Its caused by a wing generating lift. If you assume that the wake's
downward angle is 1/3 of the wing's AOA you won't be far wrong.


--
Martin | martin at
Gregorie | gregorie dot org

On Thursday, February 28, 2019 at 12:35:13 AM UTC-8, Martin Gregorie wrote:
On Wed, 27 Feb 2019 18:12:56 -0800, Tom BravoMike wrote:

I have always believed the wake basically goes DOWN behind the tow
plane, being compressed, i.e. heavier, air, and/or maybe for other
reasons. I don't remember feeling any wake turbulence just following the
tow plane at the same height, climbing or level flight.

Its caused by a wing generating lift. If you assume that the wake's
downward angle is 1/3 of the wing's AOA you won't be far wrong.

So maybe 2 to 3 degrees from a towplane, a 1:20 to 1:30 slope, 2 or 3 metres at the end of a 60m towrope.

What is the more controlling factor, is the tow plane is continuously climbing up and away from the wash. Leaving the wash behind if you will.

At say 60 knots, and 10 knots climb..that is a 1 in 6 angle.....giving the glider pilot the impression that the wash is dropping...but really the glider and towplane are climbing compared to the wash.

I've done many "level" (not climbing) tows. The wash essentially comes straight back. To fly outside of the wash, the glider must be either above the tow plane, or below it.


Cookie






reasons. I don't remember feeling any wake turbulence just following the
tow plane at the same height, climbing or level flight.

Its caused by a wing generating lift. If you assume that the wake's
downward angle is 1/3 of the wing's AOA you won't be far wrong.


--
Martin | martin at
Gregorie | gregorie dot org