Disclaimer: IFlyTailies aka Alex aka Schleppmeister is sharing his personal experiences with aerotowing here. Most recommendations are general, but some are specific to tow planes he has used (such as the Sr. Telemaster and Pilatus Porter 3.2m) and the type of gliders he typically tows (up to 10.6m/34ft). You still need to follow all safety guidelines and rules as established by your country's laws, modeling association, club, etc.! Following his suggestions might help you become a better tow plane and sailplane pilot. But he can not guarantee you flights without incidents. IFlyTailies will not assume any liability claims for anyone following the guidelines below. Use and apply at your own risk.
Initial Thoughts for Preparing a Tow Plane
- Big idea: Better too much than too little! This applies to motor size, structural reinforcement, servo torque, etc.
- What size (weight and wingspan) of gliders are you going to tow?
- Better too much power than too little
- What parts of my tow plane need to be reinforced?
To get in touch with me regarding questions or comments please use the Contact form
Preparing the Tow Plane
- Power system: Rule of thumb - tow plane power must be at least 100W/pound (sailplane & tow plane weight combined!). This applies for electric, gas, and glow power. Tows with 70-90W/pound are possible, but require experienced tow and sailplane pilots
- Propeller: large diameter (improves climbing), low pitch (we don't need a lot of speed)
- Custom landing gear: might be needed to provide sufficient prop clearance. Needs to handle added weight (e.g. bigger motor, structural reinforcements, bigger batteries, more fuel, etc.)
- Tow release: install right on or right after the trailing edge. Release servo: metal gear, better too much torque than too little. Mechanism needs to be slop-free (no servo binding or friction). Tow releases for tow plane and sailplane are available in my store
- Reinforcement of fuselage structure: use plywood sticks to support the spars at the leading and trailing edge from all sides. Ensure that the firewall is strong enough for your big motor or engine. Inspect the rest of the structure to reinforce as necessary
Preparing the Glider
- Tow release servo: metal gear, better too much torque than too little, mechanism needs to be slop free (no servo binding or friction)
- Personal recommendation: use a release where the diameter is big enough to easily insert the tow line = at least 10mm
Preparing the tow line
- General: There are different strength tow lines for different applications available. If you are not an expert, it is a good idea to have a center line and a break line on each end of the center tow line. The break line might break in cases where something goes wrong during tow, and relieve the tow plane and glider from structural stress
- Braided line with a breaking strength of 73lbs. is sufficient for towing smaller gliders up to 3m/118in. wingspan such as the Multiplex Easy Glider or Multiplex Cularis
- I have used the 250lbs. tow line without break lines on gliders up to 55lbs. with success
- Total tow line length: beginner 60-75ft. / 20-25m; advanced 90-120ft. / 30-40m
Tow line specifications: two different lines are used - a center line and one breaking line at each end
- Center line length: beginner 40ft./13m; advanced 70-100ft / 22-30m. Material: Braided Nylon Seine Twine. Breaking strength: 250lbs / 110kg
- Breaking line length (each): 10ft / 3m. Material: Braided Nylon Seine Twine. Breaking strength: 73lbs / 30kg. Advanced pilots or those flying large scale sailplanes might not need a break line
- Connect center and breaking line through swivels so the whole line will not twist
- Tie a loop at each end: one going to the tow plane and one going to the glider
- Visibility: attach a flag or a banner or any other highly visible material to the center line
- Tow line hook up test: once the line is hooked up to the release, grab the loop with both hands. Move the loop back and forth with your hands to ensure that the tow line can move freely and is not caught in the release mechanism --> might cause problems to actually release otherwise!
- If the tow line does not move freely, release it, and hook it up again. Perform the tow line hook up test again
Tow lines are available in my store
Communication: most important part! Tow and glider pilot need to communicate constantly.
- Discuss flight pattern before take off
- Discuss in which direction (right or left) the tow plane and sailplane will fly once they release
- Announce when you are going to release
- Announce landings
- Helper holds glider wings level during when glider starts rolling during take off; or use a dolly
- Glider is a little above tow plane's tail
- Not too fast, not too slow
- Tow pilot announces when making a turn
- Tow pilot uses rudder (not ailerons - important!) to steer the tow plane in the desired direction. Uses ailerons only to keep wings level or to support during turn
- Turns are going away from the pilots. When flying away from you, make either 90 degrees right & left turns (practical if there is stronger head wind), or fly a Figure 8 pattern (harder to do)
- Sailplane follows tow plane smoothly at all times and flies a slightly larger circle than the tug in turns
- Sailplane pilot uses slight rudder input to correct flight path (important!) and uses ailerons only to keep wings level
- Pilots communicate when they are ready to release
- Sailplane pilot verbally confirms tow line separation after release
Not so perfect tow:
- Wing tip of sailplane touches ground and glider twists 90 degrees to any side - release immediately!
- During take off, engine of tow plane quits - release immediately!
- During take off, sailplane veers erratically to one side or the other - release immediately if you can not stabilize by using rudder input!
- During tow, sailplane needs lots of elevator/ailerons/rudder input - slow down tow plane; maybe CG problem? Release immediately if system becomes uncontrollable
- During a turn, the sailplane cuts the corner (= does not fly a slightly wider circle than the tug) - very dangerous because of slack in tow line followed by a sudden stretch and possible stall of tow plane and sailplane or both
- Visibility: avoid flying into the sun. Visibility will get tricky at certain flight angles and altitudes
- Release does not work - start thinking about your next plane:-) Tow & glider pilot could try a landing together (that video would get a lot of hits on YouTube)
- If anything else goes wrong - use common sense; communicate; consider releasing immediately
- Tow Plane:
- Don't forget: you have a tow line dragging behind you! If there are any obstacles such as bushes, trees, fences, or even corn or other plants at the beginning of the runway, be aware that the tow line might get entangled and your tow plane will come to a stop in a very short time, even if the tow line will break. This might result in more or less damage. You have to carefully check your tow plane to see if it suffered any structural damage in case that happens!
- If there are obstacles in the landing approach area:
- Consider flying over the runway in a safe altitude and dropping the tow line. Then, land your tow plane. Be aware that the tow line will drop below your tow plane because of its own weight below a certain speed!
- If you do not want to or cannot drop the tow line, you must either land way down the runway so the tow line stays clear of any obstacle (favorable option) or approach in a high angle (unfavorable option)
- Consider coming in at an angle where there are no obstacles
- If there are no obstacles, you should not have problems landing with or without your tow line
- Make sure there is no tow plane in your way waiting on the runway. If you or someone else is using a dolly, have a helper retrieve it and clear the runway