Bartman
Defender of the Noob!
AERO-TOW involves towing sailplanes to altitude and then releasing them via a servo actuated mechanism but what's involved and what do the parts look like?
To put it in terms of the big parts there's a tow plane, a long tow line, and a sailplane or glider. The tow planes pull the gliders up to altitude via the tow line and when the glider pilot is happy with the altitude and position he/she hits the release and flies off while the tow plane returns to land and hooks up to another glider for another launch.
I should emphasize that just about any plane can be made to tow gliders and just about any glider (sailplane, glider, motor-glider, etc.) can be launched via aero-tow. The only catch is that a small plane can't necessarily aero-tow a very large glider, the power has to be there to tow the glider at the aft end of the line. Bigger tow planes can tow very small gliders though.
So let's look at the small pieces involved in making this work. First there needs to be a place on the tow plane and on the glider to connect the tow line. Both connection points have be controlled by servos so that the tow pilot or the glider being towed can disconnect at any time.
On the glider the connection point is either centered in the nose cone or somewhere just below and aft of the nose. The tow line isn't connected directly to the release mechanism, a loop is used between the glider and the tow line to facilitate quicker turnaround times on the runway when aircraft are lined up awaiting launch.
These pictures show the loops attached to the fronts of the sailplanes
A few sample release mechanisms can be found here
http://www.iflytailies.com/store/tow-releases/
The tow line is then attached to the loop via a fishing clasp
The loop stand is the center of activity at an event
The tow line is pretty long, depending on the size of the aircraft being flown it can be as short as 20 ft for foamies pulling foamies or 100 ft or more for giants scale tugs pulling giant scale sailplanes. Also, as the aircraft get larger and heavier, the tow line has to be thinker/stronger.
The tow line attaches to the tow plane in a way that is different from full scale aircraft. Although it's been tried, when the tow lines are attached to the tail (as it is done with full scale tow planes) the tow planes are harder to control and are more affected by the glider being towed. So to make the tow plane fly well for the RC tow pilot, the tow line is attached to the top of the fuselage somewhere just behind the wing's trailing edge. By doing this, when the glider is at its optimum position above and behind the tow plane, the tow line is very nearly in line with the tow plane's CG allowing it to fly almost unaffected by the glider being towed behind it.
A mechanism called a "tow hitch" is where the tow line is connected to the tow plane. It is servo controlled allowing the tow pilot to release the tow line (and the glider being towed) in the event of an emergency with either the glider or the tow plane.
In this picture of @JimD 's 100cc Hangar 9 Super Decathlon (with a DA-120 and 100 ounces of fuel) you can see the tow line attached to the hitch just above the cabin. It is very rare but it has happened where the tow line has damaged the vertical stabilizer.
Here's a sample of how things go when everything is running smoothly
Giant scale soaring is fun and very relaxing, flights can be hours long when there's lift and everyone works hard to maintain that very friendly environment that we all love to be a part of!
To put it in terms of the big parts there's a tow plane, a long tow line, and a sailplane or glider. The tow planes pull the gliders up to altitude via the tow line and when the glider pilot is happy with the altitude and position he/she hits the release and flies off while the tow plane returns to land and hooks up to another glider for another launch.
I should emphasize that just about any plane can be made to tow gliders and just about any glider (sailplane, glider, motor-glider, etc.) can be launched via aero-tow. The only catch is that a small plane can't necessarily aero-tow a very large glider, the power has to be there to tow the glider at the aft end of the line. Bigger tow planes can tow very small gliders though.
So let's look at the small pieces involved in making this work. First there needs to be a place on the tow plane and on the glider to connect the tow line. Both connection points have be controlled by servos so that the tow pilot or the glider being towed can disconnect at any time.
On the glider the connection point is either centered in the nose cone or somewhere just below and aft of the nose. The tow line isn't connected directly to the release mechanism, a loop is used between the glider and the tow line to facilitate quicker turnaround times on the runway when aircraft are lined up awaiting launch.
These pictures show the loops attached to the fronts of the sailplanes
A few sample release mechanisms can be found here
http://www.iflytailies.com/store/tow-releases/
The tow line is then attached to the loop via a fishing clasp
The loop stand is the center of activity at an event
The tow line is pretty long, depending on the size of the aircraft being flown it can be as short as 20 ft for foamies pulling foamies or 100 ft or more for giants scale tugs pulling giant scale sailplanes. Also, as the aircraft get larger and heavier, the tow line has to be thinker/stronger.
The tow line attaches to the tow plane in a way that is different from full scale aircraft. Although it's been tried, when the tow lines are attached to the tail (as it is done with full scale tow planes) the tow planes are harder to control and are more affected by the glider being towed. So to make the tow plane fly well for the RC tow pilot, the tow line is attached to the top of the fuselage somewhere just behind the wing's trailing edge. By doing this, when the glider is at its optimum position above and behind the tow plane, the tow line is very nearly in line with the tow plane's CG allowing it to fly almost unaffected by the glider being towed behind it.
A mechanism called a "tow hitch" is where the tow line is connected to the tow plane. It is servo controlled allowing the tow pilot to release the tow line (and the glider being towed) in the event of an emergency with either the glider or the tow plane.
In this picture of @JimD 's 100cc Hangar 9 Super Decathlon (with a DA-120 and 100 ounces of fuel) you can see the tow line attached to the hitch just above the cabin. It is very rare but it has happened where the tow line has damaged the vertical stabilizer.
Here's a sample of how things go when everything is running smoothly
Giant scale soaring is fun and very relaxing, flights can be hours long when there's lift and everyone works hard to maintain that very friendly environment that we all love to be a part of!
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