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Fatal Towplane Accident 5-9-20



 
 
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  #191  
Old June 2nd 20, 07:28 PM posted to rec.aviation.soaring
Peter Whitehead
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Default Fatal Towplane Accident 5-9-20

Is the statement or suggestion that the low tow reduces the insidence of tug upsets based on evidence (eg from Australia, where I understand low tow is the norm) or hunch/belief/'common sense' /anecdotal observation?
The denominator of number of aerotows should be applied to the numbers.
Important question to answer before applying the 'solution' of low tows for everyone, do you not think?

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  #192  
Old June 2nd 20, 09:18 PM
Delta8 Delta8 is offline
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Ok ...How about unmanned Drones? Have a local teenager under a hood flying remotely.
  #193  
Old June 2nd 20, 11:51 PM posted to rec.aviation.soaring
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Default Fatal Towplane Accident 5-9-20

On Tuesday, June 2, 2020 at 1:46:59 PM UTC-4, Neal Alders wrote:
-Here's another question about low tow:

-Has a glider on low tow ever pulled the tail of the towplane DOWN and caused the towplane wing to stall?

A: No idea. Never heard of it happening, But, I would think you would need a proportionate amount of altitude to cause that, and a stall recovery is easier at low altitude when already at full power, especially if you dump the glider, than an extreme nose down at a far lower altitude on take off. Imagine the angles. Would you rather be nose up or nose down at 200 feet?


We tested that issue 30 years ago using a Super Cub and a 2-33. We were never able to get to where we were pulling the tail down a significant amount. We tested down to tow speeds that went slightly below where the Cub would stall in free flight. Out conclusion was that the tug got more stable with the glider behind.
It is worth noting that most people fly the tow too low based upon my observation of lots of pilots trained at other sites. If you are not occasionally nibling the wake with the vertical tail, you probably are flying too low.
FWIW
UH
  #194  
Old June 3rd 20, 01:08 AM posted to rec.aviation.soaring
Neal Alders
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Default Fatal Towplane Accident 5-9-20

To answer the Australia Low Tow question, as seen in the The Gliding Federation of Australia Inc Aerotowing Manual

Go to page 44 in this PDF

http://doc.glidingaustralia.org/inde...als&Itemid=101

If you cannot or do not want to open the link, here is the text.

10.1.12.High-tow and Low-tow An aircraft in flight generates a “slipstream” behind it.This is a region of turbulent air, originating mainly from large vortices streaming from the wingtips, with small amounts of mechanical turbulence such as propeller wash thrown in for good measure. A glider pilot may choose to fly either above or below this turbulent slipstream(Refer 10.1.10).Australia tends to favour the “low-tow” position.Other countries prefer “high-tow”.
10.1.12.1.Low-tow With a glider in low-tow, below the slipstream, the combination tends to be less pitch sensitive and tow pilots have less difficulty in maintaining attitude for a constant air speed and a stable platform for the glider pilot to follow.
10.1.12.2.High-tow In high-tow, above the slipstream, the combination feels a little more pitch sensitive and tow pilots need to work harder to maintain a constant climb attitude and air speed.The difference is not large and tow pilots should have no difficulty in maintaining a stable platform whichever position the glider pilot chooses.WARNING: HIGH-TOW IS, BY DEFINITION, ABOVE THE SLIPSTREAM, NOT ABOVE THE TOW PLANE. There is one important difference between low-tow and high-tow and this becomes apparent if a glider gets out of position vertically(i.e. too high). In low-tow a glider can get very low and still not cause significant difficulty for the tow pilot in controlling his aircraft.Furthermore, out-of-trim forces tend to change at a slow enough pace that the tow pilot has ample time to release the glider if there is any fear that the limits of elevator control might be reached. In high-tow, things happen more rapidly and the tow pilot will have less time to react to a glider going too high.If a glider that is out of station in high tow(i.e. too high)is not released immediately, there is a risk of the tow plane being pulled out of control.See Section 10.3“The tow plane upset”. Tow pilots need to be trained to tow gliders in both high and low-tow and to experience a glider transitioning between the two positions.To avoid subjective judgements about high-tow and low-tow, the reference for the glider pilot establishing the towing position is always the slipstream.
  #195  
Old June 3rd 20, 01:11 AM posted to rec.aviation.soaring
Neal Alders
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Default Fatal Towplane Accident 5-9-20

To answer the Australia Low Tow question, as seen in the The Gliding Federation of Australia Inc Aerotowing Manual

Go to page 44 in this PDF, As well as see PDF Page 53 for tow plane upset.

http://doc.glidingaustralia.org/inde...als&Itemid=101

If you cannot or do not want to open the link, here is the text.

10.1.12.High-tow and Low-tow An aircraft in flight generates a “slipstream” behind it.This is a region of turbulent air, originating mainly from large vortices streaming from the wingtips, with small amounts of mechanical turbulence such as propeller wash thrown in for good measure. A glider pilot may choose to fly either above or below this turbulent slipstream(Refer 10.1.10).Australia tends to favour the “low-tow” position.Other countries prefer “high-tow”.
10.1.12.1.Low-tow With a glider in low-tow, below the slipstream, the combination tends to be less pitch sensitive and tow pilots have less difficulty in maintaining attitude for a constant air speed and a stable platform for the glider pilot to follow.
10.1.12.2.High-tow In high-tow, above the slipstream, the combination feels a little more pitch sensitive and tow pilots need to work harder to maintain a constant climb attitude and air speed.The difference is not large and tow pilots should have no difficulty in maintaining a stable platform whichever position the glider pilot chooses.WARNING: HIGH-TOW IS, BY DEFINITION, ABOVE THE SLIPSTREAM, NOT ABOVE THE TOW PLANE. There is one important difference between low-tow and high-tow and this becomes apparent if a glider gets out of position vertically(i.e. too high). In low-tow a glider can get very low and still not cause significant difficulty for the tow pilot in controlling his aircraft.Furthermore, out-of-trim forces tend to change at a slow enough pace that the tow pilot has ample time to release the glider if there is any fear that the limits of elevator control might be reached. In high-tow, things happen more rapidly and the tow pilot will have less time to react to a glider going too high.If a glider that is out of station in high tow(i.e. too high)is not released immediately, there is a risk of the tow plane being pulled out of control.See Section 10.3“The tow plane upset”. Tow pilots need to be trained to tow gliders in both high and low-tow and to experience a glider transitioning between the two positions.To avoid subjective judgements about high-tow and low-tow, the reference for the glider pilot establishing the towing position is always the slipstream.
  #196  
Old June 3rd 20, 02:06 AM posted to rec.aviation.soaring
son_of_flubber
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Default Fatal Towplane Accident 5-9-20

On Tuesday, June 2, 2020 at 1:35:05 PM UTC-4, Hightime wrote:
How does one combat turbulence and fly smoothly in low tow ...


I've had opportunities to aerotow through rotor to fly in wave.

After the tug flies through a patch of lift/sink, time elapses before the glider flies through same patch, and by then the tug may fly through a different patch of lift/sink. Its normal for the glider to move somewhat above and below the optimal high tow position. With practice, I've learned to smooth out this oscillation with elevator and rudder/spoilers, but it is not possible, nor desirable to try to completely eliminate the bobbing above and below optimal position. Attempting to do so leads to overshooting the optimal position. In high tow position, the glider can bob somewhat above and below optimal position without overwhelming the tug's elevator authority.

Is it okay for a glider to bob above and below optimal low tow position?

What about the oscillation in bank angle in rotor that is tolerable in high tow position? Is aileron authority any different in low tow position?
  #197  
Old June 3rd 20, 02:48 AM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Fatal Towplane Accident 5-9-20

Many recent questions.....many recent answers.....

To answer you, you are just below the propwash, thus the glider controls work perfectly fine. If you get too high, you're in high tow.
If you get too low, the towplane still flies...as "UH" mentioned, several times many years ago (with prior pre tow discussion), we flew "really low tow" as in basically looking at the full belly of the towplane. It still flew but the rope angle was ugly.
Advantage was you still saw the towplane.
Too high, towplane disappears.....yep, sucks to be the towpilot then.....regardless of hitch type.

I have flown low tow through some rather rough (well, rough for where I fly) rotor, no issues other than busy/rough.

I will agree, a kiting situation gets real bad real fast regardless of high vs. low tow.
  #198  
Old June 3rd 20, 01:58 PM posted to rec.aviation.soaring
[email protected]
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Default Fatal Towplane Accident 5-9-20

On Tuesday, June 2, 2020 at 5:11:34 PM UTC-7, Neal Alders wrote:
To answer the Australia Low Tow question, as seen in the The Gliding Federation of Australia Inc Aerotowing Manual

Go to page 44 in this PDF, As well as see PDF Page 53 for tow plane upset..

http://doc.glidingaustralia.org/inde...als&Itemid=101

If you cannot or do not want to open the link, here is the text.

10.1.12.High-tow and Low-tow An aircraft in flight generates a “slipstream” behind it.This is a region of turbulent air, originating mainly from large vortices streaming from the wingtips, with small amounts of mechanical turbulence such as propeller wash thrown in for good measure. A glider pilot may choose to fly either above or below this turbulent slipstream(Refer 10.1.10).Australia tends to favour the “low-tow” position.Other countries prefer “high-tow”.
10.1.12.1.Low-tow With a glider in low-tow, below the slipstream, the combination tends to be less pitch sensitive and tow pilots have less difficulty in maintaining attitude for a constant air speed and a stable platform for the glider pilot to follow.
10.1.12.2.High-tow In high-tow, above the slipstream, the combination feels a little more pitch sensitive and tow pilots need to work harder to maintain a constant climb attitude and air speed.The difference is not large and tow pilots should have no difficulty in maintaining a stable platform whichever position the glider pilot chooses.WARNING: HIGH-TOW IS, BY DEFINITION, ABOVE THE SLIPSTREAM, NOT ABOVE THE TOW PLANE. There is one important difference between low-tow and high-tow and this becomes apparent if a glider gets out of position vertically(i.e. too high). In low-tow a glider can get very low and still not cause significant difficulty for the tow pilot in controlling his aircraft.Furthermore, out-of-trim forces tend to change at a slow enough pace that the tow pilot has ample time to release the glider if there is any fear that the limits of elevator control might be reached. In high-tow, things happen more rapidly and the tow pilot will have less time to react to a glider going too high.If a glider that is out of station in high tow(i.e. too high)is not released immediately, there is a risk of the tow plane being pulled out of control.See Section 10.3“The tow plane upset”. Tow pilots need to be trained to tow gliders in both high and low-tow and to experience a glider transitioning between the two positions.To avoid subjective judgements about high-tow and low-tow, the reference for the glider pilot establishing the towing position is always the slipstream.



Regarding the safety difference between high and low tow, I'm not sure that the relatively small vertical difference between high and low tow (about 50ft max?) is very important for tow safety. In my experience, getting unusually high from the high-tow position (eg in preparation for demonstrating a slack rope) causes no difficulty for the towplane, provided one moves high slowly (and always keep the towplane in sight). It does not affect the towplane much because the tension in the rope (glider drag is probably only about 50lbs during normal tow) probably changes very little during this maneuver, and the angle of the rope changes little too (50ft in 200ft would be about 15 degrees). The problem of kiting occurs when the glider moves high QUICKLY, causing the tension in the rope to increase rapidly. Probably a similar downward kiting effect could occur if the glider was in low tow, and dived quickly.
  #199  
Old June 3rd 20, 02:10 PM posted to rec.aviation.soaring
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Default Fatal Towplane Accident 5-9-20

If the glider is climbing due to inattention, then from low tow he has further to go and also flys thru the prop wash. A little extra time and a wakeup might not fix it, but shouldn't hurt?
  #200  
Old June 3rd 20, 03:00 PM posted to rec.aviation.soaring
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Default Fatal Towplane Accident 5-9-20

On Wednesday, June 3, 2020 at 8:58:23 AM UTC-4, wrote:
On Tuesday, June 2, 2020 at 5:11:34 PM UTC-7, Neal Alders wrote:
To answer the Australia Low Tow question, as seen in the The Gliding Federation of Australia Inc Aerotowing Manual

Go to page 44 in this PDF, As well as see PDF Page 53 for tow plane upset.

http://doc.glidingaustralia.org/inde...als&Itemid=101

If you cannot or do not want to open the link, here is the text.

10.1.12.High-tow and Low-tow An aircraft in flight generates a “slipstream” behind it.This is a region of turbulent air, originating mainly from large vortices streaming from the wingtips, with small amounts of mechanical turbulence such as propeller wash thrown in for good measure. A glider pilot may choose to fly either above or below this turbulent slipstream(Refer 10.1.10).Australia tends to favour the “low-tow” position.Other countries prefer “high-tow”.
10.1.12.1.Low-tow With a glider in low-tow, below the slipstream, the combination tends to be less pitch sensitive and tow pilots have less difficulty in maintaining attitude for a constant air speed and a stable platform for the glider pilot to follow.
10.1.12.2.High-tow In high-tow, above the slipstream, the combination feels a little more pitch sensitive and tow pilots need to work harder to maintain a constant climb attitude and air speed.The difference is not large and tow pilots should have no difficulty in maintaining a stable platform whichever position the glider pilot chooses.WARNING: HIGH-TOW IS, BY DEFINITION, ABOVE THE SLIPSTREAM, NOT ABOVE THE TOW PLANE. There is one important difference between low-tow and high-tow and this becomes apparent if a glider gets out of position vertically(i.e. too high). In low-tow a glider can get very low and still not cause significant difficulty for the tow pilot in controlling his aircraft.Furthermore, out-of-trim forces tend to change at a slow enough pace that the tow pilot has ample time to release the glider if there is any fear that the limits of elevator control might be reached. In high-tow, things happen more rapidly and the tow pilot will have less time to react to a glider going too high.If a glider that is out of station in high tow(i.e. too high)is not released immediately, there is a risk of the tow plane being pulled out of control.See Section 10.3“The tow plane upset”. Tow pilots need to be trained to tow gliders in both high and low-tow and to experience a glider transitioning between the two positions.To avoid subjective judgements about high-tow and low-tow, the reference for the glider pilot establishing the towing position is always the slipstream.



Regarding the safety difference between high and low tow, I'm not sure that the relatively small vertical difference between high and low tow (about 50ft max?) is very important for tow safety. In my experience, getting unusually high from the high-tow position (eg in preparation for demonstrating a slack rope) causes no difficulty for the towplane, provided one moves high slowly (and always keep the towplane in sight). It does not affect the towplane much because the tension in the rope (glider drag is probably only about 50lbs during normal tow) probably changes very little during this maneuver, and the angle of the rope changes little too (50ft in 200ft would be about 15 degrees). The problem of kiting occurs when the glider moves high QUICKLY, causing the tension in the rope to increase rapidly. Probably a similar downward kiting effect could occur if the glider was in low tow, and dived quickly.


There is no downward kiting. Descending glider reduces or removes rope tension so glider is losing energy, not gaining it. The vertical distance between high tow and low tow( both being just out of the wake)is less than 20 feet.
When pilots go high for slack rope exercises the affect on the tug, and required back stick, is quite a bit.
UH
 




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