Towing – why and how?
by Had Robinson
updated September 8, 2023
A hang glider pilot who was towed up with our equipment commented, "This was the safest towing I have done in all my years of towing...and I started towing in January 1978."
Early training is done via pay-in towing which is where the pilot is connected to a line going to a stationary (pay-in) winch. The tow operator uses the winch to pull the pilot up into the air. It has important advantages over training from a hill.
- Pilots have more time in the air for each flight because they begin their flights after the tow up much higher (800-1,000' AGL) than at a training hill.
Typically, we can accomplish in a day of towing what would take a week or more at a hill or a mountain launch.
- Pilots can repeat flights in a fraction of the time compared to a hill or mountain site because they
launch from the same place they land and do not have to wait around for a ride back to launch.
- Training is safer because the launch routine (when the pilot's feet are still on, or near, the ground) can be stopped immediately
and completely, something that can be difficult or impossible at a training hill or at a mountain site.
- Task saturation is less and overall comfort of the student pilot is much greater. It may be daunting for someone who has never flown to launch from a hill or
cliff. Nonetheless, as soon as the pilot is able, he must begin flying from a hill/mountain.
Tasks for the pilot are added slowly and when he is ready.
- New students can learn and practice maneuvers that are
impossible or risky at a training hill such as spiral dives, riser twist-ups, big ears, cravat clearing, deep asymmetric and symmetric deflations, and crosswind launches.
- From launching to landing the student
pilot is always close to the instructor and his watchful eye. The net result is that risk and stress are substantially lessened. Students will have better, faster, and more thorough
training, overall. Those who learn how to tow will be at a greater advantage when that is the only way available to launch, such as when attending SIV clinics or flying in parts of the world
which are relatively flat but have excellent flying conditions e.g. the central United States. Note: site loss due to
- The downside of towing is that it costs more because of the need for more personnel and equipment to train the pilot.
As P2 training progresses, students will begin flying at a mountain site with the confidence required to do it safely. The time needed to train varies depending on the weather, student availability, and student ability.
Training by towing also has the advantage of giving a new student pilot 5-15 flights a day, 600' - 1,000' AGL (above ground level). Beginning a required task happens the moment the pilot disconnects from tow and is at peak altitude rather than having to fly away from the hill and beginning tasks at a lower altitude. This gives substantially more time in the air. This is important when learning how to do spiral dives (getting out of the air quickly) and asymmetric deflations of the glider (e.g. big-ears and big big-ears) which need to be done with plenty of altitude.
However, training via tow for PG pilots must be complemented as early as possible with training from a mountain or hill.
Below, a pilot launches with a cravat in his left wing tip that was put there at launch. What does it feel like? What happens? The pilot learned first hand and successfully fixed it "on the fly"!
- tow of a new student
- typical tows (thank you Steve Crye)
- fun video of towing by Shelley Ballard-McKinlay
- hour long video of a recreational high tow (over 5,000' AGL – thank you Steve Crye)
- video of a recreational tow
showing the launch (here is a high res version of the same tow)
- example of task saturation experienced by a new pilot
- video of a new student being towed
- video of a landing
(actual speed, 50% slow motion - look at the hands)
- 1st time tow of an advanced pilot (watch his hands which make his launch run slower)
Southwest Airsports is indebted to the Armed Forces of the United States for their invaluable help in developing our training techniques. The countless number of active-duty servicemen we have trained, including Navy Seals, have provided important tips that have made our training the safe and effective. How do warriors in combat neutralize or lessen task saturation? Task saturation is dangerous and causes pilots to "freeze" or panic. It cannot be completely eliminated but is greatly lessened by proper training in stages and minimizing the effects of pilot error.
The winch used for towing
The winch has a 25 HP twin cylinder gasoline engine that is direct coupled to a hydraulic pump, the heart of the system. Hydraulic fluid is routed through various valves to a servomotor connected to a 36" diameter aluminum drum which holds 10,000' of a strong and durable line called Spectra. The servomotor is heavy duty and is commonly used to drive the front wheels of farm tractors.
The most dangerous time of any tow is the first 15 seconds and why ONLY trained, competent people should perform the tow.
The tow force is adjusted by varying the hydraulic pressure to the servomotor by a special valve. The force on the towline does not change whether the line is paying in or paying out. This is especially valuable if the towed pilot enters a layer of air that is going at a much different speed, usually the same direction but higher speed. Rather than break a weak-link, the towline simple pays out.
The advantage of a fully hydraulic system (as opposed to scooter and other mechanical systems) is that tow forces can be precisely regulated at all times. Our type of winch can do pay-out and pay-in during the same tow, as needed. Only a constant-force winch can do this, as opposed to many winches which are only constant speed.
Some of the new winches, like the eWinch, can also do pay-out/pay-in at the same time, just like our winch. However, the eWinch and others like it are not designed for continuous heavy duty use such as all day continuous towing, towing up heavy pilots, tandems, pilots with paramotors, or hang gliders. Only a trailer mounted winch can have a line capacity of over 10,000' which allows recreational pay-out high tows where pilots can get over a mile high. For new P3 pilots it's a taste of what cross-country flying is like. Nonetheless, the eWinch is relatively new and the technology has not been thoroughly tested against electronic failure such as a shorted IGBT which could instantly put the electric motor to 100% torque. This could cause an accident. For this reason, I recommend that schools and recreational towing groups wait a few years until double safeguards are in place to prevent this type of fault.
A weak-link is used to protect pilots when there is a malfunction during the tow. When the force of the tow exceeds a certain value, the weak-link breaks, the pilot is released from the towline, he glides towards the ground, and safely lands. The size we use is less than 1/2 of the typical weak-link (ordinarily 125% of pilot weight). The small weak-link we use prevents glider surge if it breaks. In some cases, it can prevent parachutal stall and the hazards from a fast moving piece of hardware or line going directly at the pilot, often into the face. We can use such a small weak-link because our winch does not experience the typical jerking, surging, and inability to instantly reverse direction that is characteristic of most other high capacity winches. This makes our 100% hydraulic winch, the eWinch, and others like it much safer for towing.
LIMITING THE TOW FORCE The tow force is adjusted so that the pilot does not climb faster than about 100'/min for the first 50' of altitude. If there is an failure of the towing system, such as a towline break, the sudden forward surge of the glider will be minimal and not require any action by the pilot to recover and land safely. If the surge is substantial because the TO wanted to get the pilot up quickly and is not checked by the pilot, he can pendulum into the ground with tremendous force causing injury or worse (and the reason that ONLY trained and experienced TO's should operate a winch).
Once the pilot is away from the ground where a surge is not a problem, the climb rate is increased to 600'-800'/min, the rate of a modest thermal. Exceeding this value requires more towing force and any mishaps or mechanical failures become more complicated and dangerous to the pilot. For example, a break in the weak-link (which is close to the pilot being towed) can result in his being hit in the face by hardware or the towline which could cause an injury with excessive towing force.
If any equipment malfunction occurs, the TO also has a hook knife with which he can quickly cut the towline, if needed. He maintains constant contact with the towed pilot via radio. The pilot and the TO have backup radios in case one fails. If all of the radios become inoperable, there are physical signals that can be used between the pilot and the TO. Just the same, pilots are trained that if, for some reason, they cease to hear or see commands from the instructor they must immediately release from tow and land safely.
In order to maximize safety during tow, Southwest Airsports is developing a device called the HyperCut, a radio controlled hook knife (Link Knife™) that is located between the weak-link assembly and the drogue parachute. In the event of some mishap, the tow can be ended instantly (<1 sec) by activation of the HyperCut.
Typically, cutting the towline at the winch results in the pilot dragging 1,000's of feet of towline around which could get caught on objects (this has not ever happened in many years of towing up pilots). The weak-link might break under such circumstances but if the snag happens at the wrong time, it could result in a surge of the glider near the ground. Another downside of cutting the towline at the winch is that it also takes longer than throwing a switch that is right next to the TO.
Pay-in mode is done typically at airports, large fields, and turf farms. The line goes out from the winch to a truck 1/2 mile away on the other side of the tow area. The truck has a 15' mast with a pulley at the top. The line goes through the pulley and then all the way back to the winch. In this way, the TO is right next to the pilot during the launch segment of the flight and can monitor the student closely.
Pay-out mode for recreational tows is typically done from a 15 mile long straight highway that has few or no intersections and no power lines crossing the road. The winch is pulled from behind a truck and the line pays out as the pilot is pulled into the air, just like a boy running and launching his kite. Pay-out towing requires more skill, both of the pilot and the TO which is why a P3 rating is required of the pilot for all pay-out towing.
In a towing operation, launching can be made in virtually any direction, depending on wind direction.
Here is a typical reading from a flight made by an experienced pilot who carried a variometer showing the climb rate and maximum altitude reached under each tow. In this tow, the pilot climbed at about 600 ft/min in dead air reaching an altitude of 700'. How high the pilot gets with a pay-in tow depends on wind speed at launch and time of day. Getting higher means more time in the air.
The safety of a tow depends entirely on the TO and why it is extremely important that the tow be conducted by a qualified and experienced operator certified by USHPA.
- You are RISKING YOUR LIFE if you are towed by a non-qualified, non-credentialed operator!
Weather often makes towing the difference between pilots staying on the ground or flying. Wind direction does not matter when towing.
Launching under tow. Photo by Steve Crye
How to launch via towing is also an important skill to have before attending SIV clinics. At these clinics, a pilot can be towed 1,000’s of feet into the air over water in order to safely practice special maneuvers that might be needed in flight. Pilots who learn towing at clinics for the first time can be distracted and overwhelmed by the tow operation itself. As a result, they can lose focus on the main purposes of the clinic.
PPG PILOTS Being towed for the first time can be a safer and more relaxed environment for new powered paragliding pilots. Learning how to control both the paramotor and glider at the same time while launching can be overwhelming. Instead, the pilot can be towed up to altitude with the paramotor OFF, disconnect from tow, start the engine, and fly away. With this technique, the way too common and expensive accident of getting the paraglider and lines wrapped up in the propeller can be avoided.
Hooking up to the towline. The orange drogue parachute is connected to the towline. It helps us find the end of the towline after the pilot disconnects in flight. Pilot safety is our primary concern and everything is done with that in mind.
Pilot's view of a tow shortly after launch – on his way to 9,000' MSL. Photo by Steve Crye.
Steps of a typical pay-in tow
(These steps can be downloaded as a PDF here.)
- Pre-flight & launch preparation – The pilot prepares for the flight by first doing a safety check (pre-flight) with the help of the instructor/tow operator (TO). A special tow bridle is
connected to the pilot's harness which has a quick release handle which can disconnect the pilot from the towline at anytime. The TO ensures that the pilot is ready to fly and all safety
equipment is present and working correctly, including radio communications. The TO chooses the correct weak-link for the pilot's weight.
- Pilot to Tow Operator Instructions
Take up slack – Pilot repeatedly extends one leg out to the side and back into the center
Stop pre-tensioning – Pilot stops leg movement and braces self with both feet
Ready to launch – Pilot makes a single forward bend at the waist
Increase towline tension – Pilot repeatedly flaps both elbows or arms up and down
Decrease towline tension – Pilot repeatedly scissors both legs out to the sides and back into the center
Imminent release – Pilot spreads both legs out to the sides (a BIG scissors) and holds them there
- Layout – The pilot will lay out the glider behind him. Depending on the wind speed, he may face forward for a forward inflation (calm – light winds) or he may
face towards the rear for a reverse inflation (light winds or greater). Most new pilots are more comfortable doing forward inflations until they have practiced their kiting skills.
- Towline – The pilot is hooked to the towline. Between the towline and tow bridle there is a weak-link of the proper size so that if there is some problem during the tow,
such as the towline suddenly jamming, it will break and disconnect the pilot from the tow. There is also a bright orange drogue parachute attached between the weak-link and the towline to
aid in recovering the towline after the tow. It also allows the TO to easily spot the end of the towline in order to bring it back to the launch area. The towline stretches out about 1/2 mile in
front, then goes through a pulley mounted high on a truck, and then all the way back to the winch which is very close to where the pilot begins the tow. The tow operator has a special knife (hook knife) that he
can use at any time to instantly cut the towline, separating it from the winch, if there is some problem during the tow.
- Forward inflation launch – When the pilot is ready (and is doing a forward inflation), he will bow deeply to indicate that he is ready to launch. The TO will
never launch the pilot until he is certain that the pilot is ready and wants to launch. After bowing deeply (he is ready to fly), the tow
operator will slowly increase the pulling force on the towline. Typically, to make the launch quick and easy, the pilot will resist the tow force by leaning back against the force of the
towline. When the force becomes irresistible, the pilot will lunge forward and run with all his strength. The glider will popup overhead. At this time, the pilot may need to apply brake on
one side or the other to ensure that the glider is flying in the forward direction. If it is and all things looks good, the tow operator will continue the tow, gently increasing the tow force
as the pilot is running forward. If the winds are calm (most often), the pilot may run 10-20 yards during which time the lift on the glider will increase and the pilot will feel it in the
harness. As often as not, the new pilot will think, "I'm flying! I'm flying! I'm flying!" – and promptly sit down in the harness. But
there is not enough lift and he will be sitting on the ground, bouncing along for a second or two while the glider dives forward. The tow operator will stop the tow – and we
must start over. Aborting the launch at this time is harmless. Depending on how the pilot feels, we may try things again, take a break, or quit for the day.
Thankfully, with forward inflations the glider almost launches itself, requiring minimal input from the pilot. The TO must carefully observe the towed pilot for task saturation which is
a common problem for those new to paragliding.
- Reverse inflation launch – If the pilot is doing a reverse inflation, he will inflate (bring up) his
wing and, facing backwards, kite it for moment in order to check everything. When he is ready, he will turn forward. This tells the TO that the pilot is ready to launch. The tow
operator will gradually increase the tow force as the pilot begins his launch run. Depending on the level of training desired and the conditions, the tow operator may have the pilot run a
long distance or short. Running a long distance might be typical of a launch from a shallow sloped site and it will require the pilot to both stay directly under the glider and control its
direction while he is on the ground. It is a great workout to run across the field and then slowly leave the earth. Recreational tows are somewhat different as the pilot must be
experienced (P3 with the surface tow (ST) rating.
- Tow force during launch – Before the pilot's feet leave the ground, the tow force can be light (experienced pilots) or stronger (new pilots). The reason
for a stronger force for new pilots is that the glider will come up quickly and stabilize faster, making it easier for the pilot to get safely in the air. More experienced pilots can
skills and experience controlling the glider by less towing force. This will require them to run more and faster, watch, and control things more carefully and deliberately. It all
happens on a flat grassy surface so errors, even bad ones, usually result in little more than grass stains on one's clothing.
Despite whatever the tow force is, the exact moment the pilot's feet leave the ground, the TO must instantly back-off on the tow force to the point where the pilot is just climbing out (<100'/min.) for the initial 50' to 75' of altitude. Why is this?
There are two serious hazards when towing. One is known as lockout. The other is an uncontrolled surge of the glider when close to the ground and is typically caused by a break of the weak-link or the towline itself. An uncontrolled surge is what must be prevented during launch when the pilot is less than 50' to 75' above the ground. Also, gently lifting the pilot off the ground will prevent parachutal stall (where the paraglider becomes a parachute with a much greater sink rate).
If there is a sudden stoppage of the tow when light tow force is being applied, the glider will be just a little bit behind the pilot as it rises, but not far behind. The glider and pilot will gently sink down and he can land safely and easily with an ordinary flare. On the other hand, if there is a stoppage of the tow when strong force is being applied, the glider will be far behind the pilot. If the resultant surge is not instantly stopped by applying the brakes the correct amount (something difficult to do for a new pilot), the glider quickly surges forward. In the next moment of an uncontrolled surge, the pilot will immediately begin to swing under the glider and down, potentially hitting the ground with enough force to cause serious injury or worse. At an altitude of 50' - 75' or more, this would be a benign event but not when near the ground!
Only after the pilot is high enough where a sudden release of the tow force would not result in him swinging into the ground, is it safe to increase the tow forces so that the pilot climbs up quickly (approximately 600'/min or 1,600 psi hydraulic pressure on the winch gauge). Towing up faster than this increases the forces on all of the equipment and pilot to uncomfortable and hazardous levels. With the proper location and equipment, 600'/min is completely adequate to get pilots to a reasonable altitude to do maneuvers.
In any case, tow force should never result in the glider being more than about 40 degrees from the vertical behind the pilot. While full stall (but not parachutal stall) is virtually impossible under tow because of the physics, a sudden release of the tow force is still frightening to the pilot. Such an event can lead to panic and is something we take the greatest pains to avoid in interest of pilot safety. All towed pilots are warned that sudden stoppage of the tow can occur at any time and to be ready to land normally. "It may just be a short flight – and let's try it again."
Ground school is an important and required venue where pilots become acquainted with the many possibilities of what can happen at launch, in particular. Eliminating surprise helps reduce panic when something goes amiss, such as a break in the towline, a hidden cravat in the glider, a sudden change in wind speed and direction, a wrap of the brake line around the riser, etc.
- During the tow – Once the pilot has left the ground, he has only ONE job and that is to ensure that the glider and the towline are perpendicular to each other.
This means that he must be looking up at the glider (the tips) and then down to the towline while making adjustments with one brake or the other as needed. New pilots are so overwhelmed
that they usually are incapable of knowing what to do, even if thoroughly briefed beforehand. This is why new pilots are given two radios attached directly to the helmet right next to
the ears so that the TO can give them the correct commands on how to keep the glider and towline perpendicular.
- If the tow goes wrong – What happens when the tow "goes wrong"? If the pilot, for whatever reason, cannot keep the glider and the towline perpendicular to each
other, the glider
will begin to enter lockout. Uncontrolled lockout is exceedingly dangerous! Referring to the boy with the kite, everyone knows what can happen to a kite. In the air, it may
turn sharply to the left or to the right and then, if the boy does nothing but continue to pull on it, it will quickly dive towards the ground and hit with tremendous speed. A
paraglider or hang glider will do the same, usually with fatal results to the attached pilot. At first, the glider gets a little off perpendicular with little change in attitude.
But as it continues to veer away from the direction of tow, the forces increase as the square of the difference in the angle off the perpendicular and both glider and pilot begin to head for the ground
with increasing speed, like the
Thankfully, the remedy to lockout is simple, foolproof, and quick: immediately stop the tow. The moment the tow stops, the glider will immediately – and safely – stabilize directly over the pilot's head, where it should be. This is the passive safety only present in paragliders. If a pilot does absolutely nothing, the wing will fly overhead at trim in a straight line through the air. TO's must be thoroughly trained and certified to know exactly what to do in an emergency. What if the pilot does a sudden 180 degree turn while under tow? The glider will enter lockout very quickly – so quickly that the TO may have to cut the line.
Typically, new pilots who are towing for the first few times have difficulty keeping things lined up and, as a result, the TO will have to slow or stop the tow and wait for the pilot to fly "straight" (the direction of tow). If it does not happen, the TO will instruct the pilot to release from tow, if he is able to respond in that way, and then land somewhere. At the turf farms, we have hundreds of clear acres for pilots to land. Most new pilots require two or three tows to learn how to fly their gliders correctly while being towed.
- End of tow – The end of tow can be any time the pilot or TO desires. There can be many reasons why. He may feel airsick or encountered
rough air. Sometimes he may be so nervous that he wants to end the flight ASAP. Experienced pilots may sense a thermal and need to get off tow so they can grab it and fly
up and away! Ordinarily, we desire the pilot to
release at the highest part of the tow. This is usually when the pilot approaches the "turn around pulley" that is attached to the truck. If he flies past this point, he will begin descending and the TO will have to release the tow by letting the towline free-wheel or by cutting the line.
a.) TIME TO RELEASE As the pilot approaches the point where he wants to release from tow, the TO asks that he performs a big "scissors kick" with his legs so the TO knows he is about to release. The TO backs off slightly on the tow force to lessen the surge of the glider after it is released from tow.
b.) LET GO of the brakes. You cannot pull the release handle AND hold the brakes at the same. To do so may cause the glider to stall (another extremely dangerous event) because he will have to bring the brake toggles why down and past the karabiners.
c.) LOOK for the release handle and grab it. Use the OTHER hand to grab the tow bridle strap that does NOT have the release handle.
d.) PULL the release handle. The drogue parachute and towline will usually drop away.
e.) SEPERATE BRIDAL STRAPS With BOTH hands, separate the tow bridle straps. Why do this? Rarely, the release line may form a friction-knot that might prevent the towline from disconnecting from the bridle. Sometimes pilots can get confused and yank on the straps rather than pull the release handle. They then might have to reach down and unclip the karabiner that connects them to the towline. There is no danger because the TO knows they are having trouble and have stopped the tow or, in extreme situations, have cut the towline. In case things jam at the turn around pulley or at the winch, the weak-link will break long before the towline can cause dangerous lockout. In over (10) years, we have never had the line jam in the turn-around pulley. It could be possible so we have to be prepared.
In this video, the new pilot experienced 100% task saturation prior to releasing from tow – an easy task that he practiced on the ground. He got free eventually but it demonstrates what can happen to us when we get in the air.
- Flying away – AFTER the tow, the pilot will use his hands to get comfortable in the harness and THEN reach up and grasp the brakes. It is then we will do maneuvers.
- Getting ready to land – The first thing a pilot MUST do before landing is to stand up in the harness when he is about 100' above the ground. He is not quite
vertical but his feet are down and ready. When he is a few feet or less above the ground (depending on the type of glider), he may bring his hands down 7"-10" to start slowing the glider
down. Right before his feet touch the ground he must pull the brakes all the way down as far as he can. This will flare/stall the glider and it will stop moving forward and,
depending on the glider type, it may "jump" making the landing a softer one. Once he lands, it is important for him to keep his hands down. He may then turn, face the glider, and
gather it up (rosette it). He may also release the appropriate amount of brake by raising his hands the moment his feet touch the ground and kite the glider for as long as he wants. More detail on how
to land safely and comfortably can be found on this page.
- After landing – At this time, the pilot should quickly rosette his glider because winds in the LZ can suddenly re-inflate the glider, pull the pilot over, and drag him. This is not a worry at the turf farms but at your typical LZ, it might matter!
The pilot's view at the top of a high tow. He cannot even see the tow vehicle which is a mile down and a mile in front of him.
photo courtesy of Lee Baker
All new pilots (including those having discovery flights) should review Dixon White's notes on towing before being towed. The course fees include instruction on how to be towed safely. Paraglider pilots will receive the "surface tow" special skills USHPA certification upon completion of the P2 or higher course. Powered Paragliding certifications do not have a specials skills certification for towing.
Below, a student pilot demonstrates perfect form at launch from tow. Note the position of his hands – they are even in height and close to the pulleys (full up position). He is still pushing on the "A" lines (but just barely now) to give the wing the speed it needs to get overhead. In a second, he will release the "A" lines and have only the brakes in his hands. He continues to run. In 4-5 seconds he will leave the ground! The orange object is a drogue parachute which helps recover the towline after the pilot disconnects. The white line across the photo is the other end of the towline that comes from the "turn around" pulley across the field. Paragliding is easier in the beginning stages because the glider – basically – flies itself.
Here is a complete explanation of how towing works (Courtesy of the Hang Gliding/Paragliding Association of Canada).
Launch events with PPG
Events such as timing the throttle on the paramotor, inflating the wing, staying under it, preventing the glider from diving to one side or the other, and enduring the noise of a fully powered engine can be a bit much for the beginning pilot. So how do we fix this issue?
With our special training technique we add new events one at a time when the pilot is ready rather than overwhelm him with a host of new tasks at the same time. We begin with a simple launch and landing – all under tow, in a straight line, and with no paramotor (or, in the case of wheeled PPG, the engine will not be running). Then, step by step, we increase the necessary tasks required. This method of instruction increases pilot safety and helps prevent damage to the equipment. Training for wheeled powered paragliding is slightly different.
Training at a hill still has advantages, such as being more like what a pilot actually does at a mountain site.
What end of tow looks like to the pilot approximately 1,000' AGL. Photo by Steve Crye