Chapter 6: Intermediate Trimming | Contents | Chapter 8: Intermediate Competition

Chapter 7: Intermediate Flying

7.1 The League of Silent Flight

The League of Silent Flight (LSF) was established in the 1970's as a non-profit organization dedicated to soaring achievement. LSF pilots can sometimes be recognized by the distinctive LSF logo on their planes or T-shirts, consisting of the letters LSF with a white bird soaring across the background. The LSF charges no dues to its members, and it costs $2 to become a permanent. The subsequent costs are a voluntary $2 per level, which the LSF uses to mail its newsletters. There are no yearly dues or other fees, making LSF one of the great bargains in R/C soaring. Though the LSF sponsors many national events, the primary focus of the LSF is its Soaring Accomplishments Program. This program recognizes achievement in R/C soaring using five levels of achievement. Working upwards through the LSF program is one of the best ways to become a better pilot, because completing each level forces you to focus on specific skills rather than simply boring holes in the sky all day. The LSF currently has just under 7500 members. To become a member you must submit a letter of intent, obtain a voucher from LSF, and complete the requirements for Level I (summarized below). Subsequent levels are achieved by completing additional vouchers, appropriately witnessed and signed. You can obtain a letter of intent and vouchers from:

The League of Silent Flight
10173 St Joe Road
Fort Wayne, IN 46835

Full rules for completing the LSF Soaring Accomplishment program are available from the LSF. A brief summary for each level is included below. For all but Level V, a second thermal flight on a different day from the first may substitute for the slope duration flight. Flights must be witnessed by someone 18 years of age or older. For Levels III and IV, two witnesses are required. For Level V, two witnesses who are LSF Level II or higher must certify each task.

7.1.1 LSF Level I

You must complete these Level I requirements to become a LSF member. First, you must complete a thermal duration flight of at least 5 minutes. A slope flight of 15 minutes is also required, though you can substitute another 5 minute thermal flight on a second day. Finally you must complete 5 landings within 3 meters of a designated point. All activities must be witnessed by someone over 21 years of age or another LSF member.

7.1.2 LSF Level II

Level II has a thermal duration requirement of 15 minutes, slope of 1 hour and you must make 10 landings within 1.5 meters of a spot. In addition a minimum of six contests must be flown against 5 or more participants, with either 1 place (1st, 2nd, 3rd), or 3,000 points using an LSF points system.

7.1.3 LSF Level III

Level III has a thermal duration requirement of 30 minutes, and slope duration requirement of 2 hours. Six contests must be flown against at least 10 participants, with either 2 places or 4,500 points using the LSF points system. In addition a goal and return flight of 1 km must be flown.

7.1.4 LSF Level IV

Level IV has a thermal duration requirement of 1 hour, and slope duration requirement of 4 hours. Six contests must be flown against at least 15 participants, with 2 places and 1 win or 6,000 points. A goal and return flight of 2 km must be flown.

7.1.5 LSF Level V

Level V represents the pinnacle of R/C soaring. A thermal duration flight of 2 hours must be flown in addition to an 8 hour slope flight. A goal and return of 10 km must be flown. In addition, 6 contests must be flown against 20 or more participants, including at least three wins as well as 12,000 points. Only a small handful of pilots (around 75) worldwide have completed Level V.

7.2 Perfect Landings

When I first started soaring, any landing that terminated with the plane in one piece was a perfect landing. As time went on, and I started to occasionally fly from smaller fields, my definition changed little. Even when I began to compete, I tended to make dramatic "spear" style landings that often damaged my plane, and ego as well. I went on for many years blaming my non-computer radio, blaming my stupid airplane, but never blamed myself. Several radios and airplanes later, I was still landing no better.

After many years of sport flying I joined the League of Silent Flight. I figured it was a good organization, with no dues or entry fees, so I invested the stamp and received my first voucher. To complete Level I and become a full member, I needed to make 5 landings within 3 meters of a designated spot. No problem, I thought, just sharpen the nose of my airplane, and I can pop out 5 landings in an afternoon. I tried placing the plane within 3 meters of my feet first. After several afternoons of dodging my plane, I decided a more scientific approach was in order.

A week later, I went to the local department store and made the best single investment of my flying career. For a grand total of $1.50 I purchased 40 feet of lawn chair repair ribbon, which I marked in meters using a measuring stick. I staked one end to the ground using a small nail, and began landing practice in earnest for the first time ever. Every day I flew, on every flight I tried to put the plane in the center of the mark.

Tip 26: Use a landing tape to measure every landing, and record each in your log book.

7.2.1 The Landing Pattern

Despite my best attempts, my landings were still very weak. The problem lay in my approach. The key to landing any plane consistently is to fly the same landing every time. This means that you must set up and use a consistent landing pattern for every landing. The entry point landing pattern is simply to put the plane 100' (a football field width) to your left or right, flying about 15-20' above the ground, heading downwind. This point in space is commonly referred to as "the window". After you fly through the window, begin a gentle right (or left) hand turn, using as little elevator as possible. Finish the turn and level out the wings, aligning your plane with the target. If you are high or low, adjust using spoilers or flaps. Never use elevator to adjust your glide path - you will ruin your entire approach. Try to keep the airspeed consistent and slow, and check for level wings to assure a smooth landing.

Tip 27: Use spoilers or flaps to adjust your glide path - Avoid the urge to touch the elevator!

To gain additional control over your pattern, put a couple clicks of up trim (and some flaps if you have them) on your plane as you enter the pattern. This will slow your plane to landing pattern speed, and give you more precise control over the final approach. Trying to slow the plane down after entering the pattern is usually too late, since it will dramatically affect your glide path. Part of the purpose of flying a clean pattern with minimal elevator input is to allow your mind to accurately perceive the glide ratio and speed of the airplane, so it can accurately tell if you are high or low.

If you are serious about improving your landings, you need to train for them. Here are some tips for a training program which will instantly improve your landings:

  • Practice landings as part of every flight. As a first goal, try to place every landing within your landing circle.
  • Make a short high start for landing practice. A good practice high start has 50 feet of latex rubber and 150 feet of fishing line. I use 3/8" OD, 1/8" ID surgical tubing which gives a reasonable launch for everything from 2M to unlimited class. If you already have a full size high start, you can cut the tubing and use small rings to splice the pieces when you want to use it full length. The short high start will give you short flights and quick turnarounds, letting you fly up to 20 flights and landings in an afternoon.
  • Begin practice by landing your airplane clean with no spoilers and minimal flaps. Remember not to touch the elevator on final approach. This will give you a good feel for the glide path of the airplane. Fly as many landings as possible each afternoon - try for 20 per day. After about 4 afternoons (80 landings) you should be able to put the plane in the circle consistently with no spoilers or elevator compensation. Record every landing, including distance to chart your progress.
  • As your skills improve, make the rules tougher on yourself. Begin to count only perfect landings. Locally we call these landings a "hiss" for the sound made when executed properly. A "hiss" is a landing that makes no noise, with wings level, and the plane does not even slightly ground loop. A "boink" is any landing that hits with a noise or ground loops even slightly. Begin to record your landings with an H for hiss and B for boink. For example you might record 2.3B for a 2.3 meter boink. After another 3 afternoons (40-50 landings) you will be able to consistently put your plane in the 5 meter circle with a hiss just about every time.
  • After you have mastered landing without spoilers or full flaps, begin to add these controls back into your landing practice. It is critical that you treat your spoilers and flaps as incremental controls. Too many people think that their spoilers and flaps have only two settings - either full on or full off. Instead you need to apply the right amount of control to adjust the height of the airplane. If you are slightly off of your desired glide path, use a little spoilers or flaps. If you are way off, use a little more. Never make sudden adjustments or you will completely miss your landing. Practice another few afternoons (40 more landings), and you will be able to place your plane in the 3-meter circle about 85
  • Finally, when you have it all down, begin to time your landings. Use a partner or tape recorder to give you a countdown so you know exactly how long it takes to fly your standard pattern both with and without wind. Make a mental note of your "window" time so you know exactly when you need to enter the landing pattern window to achieve a particular overall time. Practice making landings with a countdown so it becomes natural when you do it in competition.
  • All told, it will probably take 8-10 afternoons pulling a mini-high start to achieve a competitive landing proficiency. In most contests this means another 85-100 points to your score - a big advantage over your competitors. Being able to land the plane where you want it is a big advantage, even in sport flying. It allows you to fly from small school yards and congested fields at will. In addition, good landing skills will save many a plane from damage, saving you significant time and money.

Whenever you begin to fly a different airplane, its a good idea to pull out your mini- high start and spend a few afternoons in landing practice. Each airplane has a different glide angle, and you need to be proficient in a given plane to fly precision landings. It is always best to fly the same plane as much as possible, since it is difficult to be proficient in more than one plane at a time.

As a summary, here is a sample landing checklist.

  • Adjust trim and flaps to achieve slow landing pattern speed.
  • Target and fly the window, 100' out and 15-20' up, at desired "window time"
  • Begin gentle turn, with minimal elevator.
  • Apply flaps or spoilers proportionally to adjust approach height.
  • Wings level on final approach, and don't touch the elevator
  • Fly smoothly to a point about 1-2 meters short of the mark, and let plane slide to the mark
  • Measure each landing, and record whether landing was smooth "hiss" or noisy "boink."

7.2.2 Timed Landings

After you have learned to land with some consistency, the next step is to add time pressure. Under the ceaseless beat of the clock, pretty landings often become ugly. This is, of course, silly since a bad landing score will hurt you more than running over your time by a few seconds. The key, once again, is practice.

How does one practice timed precision landings? There are several methods. The best of all is to get a regular partner for practice. If the same person coaches and times for you in competition as in practice, you will inherently be much more relaxed in competition. This is one of the secrets of west-coast team dominance of national competition. The big-name west-coast F3B and F3J fliers practice and compete together as a team. When one pilot steps up to the line, he is surrounded by his friends offering sound tactical and strategic advice. If you can find a partner who is willing to practice with you every weekend, go for it! Take turns flying. One of you can launch and time while the other flies.

The second best method is to use some kind of audio timer to time your flights. This can be either a cassette tape or a talking timer. I use the talking timer when I don't have a partner handy. To use a cassette tape, simply record a countdown from your target time on the tape. Count down every minute, then every 10 seconds for the last minute, then a 10 second final count. When you go to the field, put the tape in a small cassette recorder, and press play after you launch. The talking timer performs the same function, but is a little easier to use. Radio Shack sells a timer, model #63-877, which has all the necessary features. You can preset any time up to 24 hours and it will count down every minute. In the last minute it counts every 10 seconds and provides a final 10 second count-down. Currently the timer sells for less than twenty dollars.

Tip 28: A talking timer is great for solo timed landing practice.

The procedure for either method is the same. Set your goal time, launch, and start the timer. I recommend setting an easy goal time for the first few flights just to get a feel for how long it takes to get down from a given altitude. Start with maybe a four or five minute goal time, then extend it as you get better at judging time. Have a friend time your regular approach pattern separately so you know approximately how long it takes to fly your landing. Keep this time in mind when you are flying so you leave enough time to fly a regular landing. It takes a lot of practice to really become good at this, so don't be discouraged if you don't get it right away.

Once you have the basics down and can make timed landings, try both very long and very short goals. Setting long time goals will help you learn to find lift, work it, and exit it at the appropriate time to meet your goal. Setting very short goals can help with aborted landings as well as those times when you may be way over your goal and need to come down quick.

Its also a very good idea to practice aborted launches, where you bail out and land immediately. F3B, F3J and many other thermal formats allow you one or more re-launches within a limited working time. To abort, simply fully extend your spoilers or flaps and then spin the plane down from launch height. This can be done by pulling full-up and full-left or full-right. About thirty or forty feet from the ground, apply opposite rudder, ease off on the elevator and fly a precision landing to your feet. The ability to abort the current flight from launch height, land near the winches, and re-launch without using too much working time is critical to many events.

7.2.3 Flaps vs Spoilers

A brief description of the differences between flaps and spoilers is in order since most pilots transition from a polyhedral rudder-elevator-spoiler plane to a flap-aileron plane sometime during their intermediate flying.

Spoilers are, in many ways, ideal for precision landing. They induce drag roughly in proportion to the amount they are extended. Therefore they provide direct control over the glide path of the plane. Coupled with the right amount of elevator compensation, they give you very precise control over how fast your plane comes down. Most spoilers are mounted on the top of the wing, which creates a downward pitching moment on the plane. Without a computer radio, the pilot must hold up elevator as the spoilers are extended to compensate.

Flaps, in contrast, are not quite so ideal. Flaps are multi-functional. Adding just a little bit of flaps effectively cambers the airfoil, slowing the plane, increasing lift, but only slightly increasing drag. As more flaps are added the amount of lift increases until the airflow finally separates from the wing. Beyond this point, up to the 90 degree point, flaps act like spoilers. They create lots of drag, and significantly slow the plane down. Fully extended flaps tend to pitch the plane up, so your computer radio should compensate with down elevator as the flaps are extended.

The fact that flaps first increase lift, and later act like spoilers as they are extended explains why our sailplanes tend to balloon on landing. As the flaps go down, they first create plenty of lift, pitching the plane off. Once the airflow separates, they create more drag than lift, reducing the pitching moment. Since most of us set elevator compensation based on fully extended flaps, this compensation is insufficient during the transition. The newest computer radios have multi-point mixing, which allows a non-linear mix to compensate for this behavior. Alternately, many people offset their flaps so that the first couple clicks of the throttle stick puts some down elevator in before engaging the flaps. This pitches the plane down slightly as flaps are extended to compensate for ballooning.

Tip 29: Have an experienced pilot help you program the flaps on your first full-house sailplane.

Because spoilers and flaps work differently, the transition from one to another can be painful at times. First, have someone help you program and trim out your new six servo lead-sled. They may have critical tips for programming in elevator compensation to avoid ballooning. Second, realize that flaps must be extended a little farther to control your glide path. Even on a properly set plane, if you pull the flap stick only a little your plane will probably balloon. You need to extend your flaps at least half-way in most cases to get a flat glide path. They will not have the same smooth glide path control as spoilers. Most pilots develop a good sense of when to apply the flaps, and then just pull them fully out on landing. Practice will make it easier.

Finally, if you can, consider using CROW for landing. In CROW, both flaps are extended down while both ailerons are extended upward. CROW has the advantage of creating less pitching moment, reducing the tendency to balloon. You need a six-servo plane and computer radio to do it, but some planes will land more easily using CROW than standard 90 degree flaps. What you finally decide to use is a matter of personal choice and experience.

7.2.4 Sliding vs skegs

A difficult problem, particularly with today's large fast sailplanes, is the fact that you never know how far your plane might slide after it hits the ground. When you transition from your polyhedral plane to your first fast six-servo ship, you will see exactly how big of a problem this is. I've seen many pilots put their plane down on the spot and slide completely through the landing circle during competition. Since the amount of slide varies with plane, terrain, approach speed and many other factors, the best insurance is practice. If you can, get to your contest site early and fly a few practice landings from hand launch or a small upstart to get a feel for how far your plane might slide on the ambient surface. Keep your approach speed slow and steady and resist the urge to fool with the elevator. In F3J, F3B and many other contests this is your only option.

In some US contests, particularly on the west-coast, another alternative is available -- the skeg. Skegs are inexpensive plastic or fiberglass teeth that you mount on the bottom of your fuselage to grab the ground when you land. The net result is the plane stays pretty much where it touched the ground. If you land at very high speed, the effect can be rather jarring, but overall skegs put less wear and tear on your plane than sliding. Since the plane stops immediately, your flaps are protected from potentially servo damaging slides. Be sure, however, to check your servo mounts if you hit really hard.

Skegs come in all kinds of shapes and sizes. Early skegs were often home built, and included spikes and other dangerous shapes. Commercial skegs, now becoming popular, frequently have shark-tooth shapes and are molded from nylon or fiberglass. Skegs are mounted much like towhooks, with a plywood plate in the bottom of the fuselage providing support. Most commercial skegs can be removed in a few minutes for conventional competitions. Most often they are placed forward of the towhook, and many people use two skegs to improve holding power.

7.3 Thermaling on Windy Days

Thermaling on a windy day is a real challenge. Even the best pilots can come down fast in high winds, and often land way off the mark. Some of the coolest pilots seem to lose their minds, letting their planes drift all over the sky like little Roo in Winnie the Poo and the Blustery Day . I used to be a fair weather pilot, never wanting to risk my plane in high winds. Inevitably every contest I went to had at least one windy day, and my scores suffered accordingly. Now I see every windy day as a chance to really improve my skills, and aggressively attack flying. The lessons from windy days have improved my fair weather flying as well - I'm better able to read the air aloft and hang in lift much longer because I can read the subtle hints my plane gives me about the moving river of air.

Here's some of the top tips I've accumulated for surviving in gale force winds.

7.3.1 Preparing for the Blustery Day

Preparing to fly in high winds is a two step process:

  • Mental Preparation
  • Preparation of the Airplane

Mental Preparation

Mental preparation is, by far, the most important! Thermaling in wind is nothing more than a contest of will. Your plane is going to get knocked all over the place, and do all kinds of strange maneuvers you've never seen before. Your job is to maintain control of the plane at all times and tell it where you want it to go! You must drive the airplane, and you cannot let it drive you. This is a significant shift from fair weather thermaling where the goal is to accomplish maneuvers with the absolute minimum of control input.

Good fair weather fliers seem to almost will their airplanes around the sky, while the windy flier must attack the air much more aggressively. Prepare yourself mentally by reciting the following sayings 100 times in a lotus position with burning incense before each flight:

  • I am the master of my airplane, it obeys my every command.
  • My plane must become one with the wind if I am to find lift.
  • The wind is my friend, it can do me no harm.
  • If it crashes, I can rebuild it.

Flaps, Ballast

Now that you have achieved the proper state of mind, you can move on to preparing your airplane. Speed is the name of the game on windy days for two reasons. First, you need speed to penetrate and search for lift. If your plane is flying 12 mph and the wind is 10mph, you won't have too many search options if you want your plane to land somewhere near the field. Your thermal search will consist of keeping the plane headed into the wind, and going to pick it up when it lands. This was the most popular windy day flight in the golden age of gas-bags (1960's, 1970's and early 80's). Second, speed offers you a margin of error. The difference between the flight speed and stall speed of the airplane determines the likelihood of stalling. In turbulent wind, different parts of the wing face slightly different relative speeds and angles of attack. If you are flying your plane slow, near stall speed, the likelihood that this turbulence will cause a stall somewhere along the wing is high. Conversely if the plane is flying safely above the stall speed, it will be much more stable and reactive despite the turbulence. You will be less likely to dork it on launch or landing, and it will be more stable in flight.

How do we achieve more speed? First, you should slightly reflex your flaps when cruising if your plane is equipped with flaps. The correct amount of reflex to apply depends on the plane and airfoil. For a SD7037 or similar airfoil, you can usually get into the ballpark if you place a straight edge along the bottom of the rear of the airfoil and raise the flaps until the ruler is as flat as you can make it. If you've done it correctly the plane should cruise faster without losing much more altitude than it would in a normal position. If your radio supports it, reflex the entire trailing edge including the ailerons. Also, if possible program the setting into your flap switch (usually bottom on three position switches) so you can cruise at will. The reflex position will often let you fly in substantial winds (up to 15mph) with little or no ballast.

Tip 30: A little reflex will significantly enhance your windy weather performance. It is also useful to get out of down air on calm days.

Second, if it is windy, you should add ballast to your plane. Ballast is good on windy days, no matter what kind of airfoil or plane you have. Ballast increases the speed and penetration of your airplane, and as important it adds stability to the plane. A heavier plane will fly faster and not get knocked around as much by turbulence on landing. A heavier plane will also come down faster, but it is more likely to come down in one piece than an unballasted plane.

Tip 31: Ballast is the best method for increasing stability and speed in windy weather.
The first step to adding ballast is to first mark where your current center of gravity is on the plane. This is a good idea even if you have a nice ballast box stationed right over your CG, because where you place the weight can change the CG, which can be disastrous in some cases. If you don't have a ballast box, you might want to be able to return to your marked CG when the ballast is removed. The best method for adding ballast is to create a strong box in the fuselage or tubes in the wing at your preferred center of gravity. If your planes are like mine, you probably already have that location filled with radio equipment and you forgot to put ballast tubes in the wing.

Method two is to use small pieces of lead and put them anywhere you can reasonable secure them. Another method is to create your ballast box aft of the CG, and then put some lead in the ballast box and a little in the nose to keep the center of gravity somewhere near your marks from above.

How much ballast to add is a matter of personal preference. I recommend a minimum of 8oz for any plane over 2M, since anything less won't do much. Adding 8oz also makes me feel like I'm doing something -- after all windy weather flying is 99 There are a few practical considerations, however. First you need to consider what your plane can take. If you are flying an all kevlar F3B airplane, and your entire extended family can stand on one of the wings without bending it, you can probably add as much weight as you want. If you are flying a Gentle Lady with the spar spliced in 10 places from previous blustery days, you might want to be more conservative. A good rule of thumb is to start with maybe 1/6th of your dry plane weight, and not exceed 1/4 of your dry plane weight in ballast unless you have a strong plane.

Towhook Position and Center of Gravity

Towhook position can also change on windy days. The extra speed gained from headwind permits a steeper launch for a given method. If you have an adjustable towhook, you might want to try moving the hook back an eighth of an inch or so from its normal position in windy weather. For high-start launches, in particular, this can lead to better windy day performance. Never place the towhook behind your CG, however. Always leave the towhook at least 1/8" to 1/4" forward of your CG or you will instantly pop-off on launch.

If you're like me, you probably have your flying CG adjusted way behind the CG shown on the plans to make the plane very unstable and hard for beginners to fly -- its no fun if just anyone can fly your plane! While this does improve the responsiveness of the airplane, and makes the tail wave at you every time your plane hits lift, this kind of trim is lousy for windy weather. In addition to adding ballast, I often add a little nose weight in windy weather to bring the CG forward 1/8" to 1/4". Many pilots place their ballast tubes slightly forward of the CG, which creates the same effect. This adds stability to the airplane without sacrificing much in performance.

7.3.2 The Launch

Launching properly in the wind can be a simple process, and can result in spectacular launches hundreds of feet above your normal launch height. First, you must understand that the wind is your friend (remember the chant?). When you launch into a 15-knot headwind, your plane gets a free 15 knots as soon as it leaves your hand. Further, that 15 knots is added to your normal tow speed for the entire launch, whether winch or highstart, significantly enhancing the effectiveness of your tow device. This extra power gives you more flexibility, but can also be dangerous.

I've seen more than a dozen planes bite the dust on blustery launches. The leading causes of death from windy day launches are:

  • The Heavy Foot Winch Launch
  • The Tip Stall

Heavy winch launches are, by far, the leading cause of launch death on windy days. New composite laminated spars have reduced this somewhat, but I still regularly see people collecting the shattered pieces of their airplane from below the winch at any windy contest. A gentleman at our local field thought it would be neat to do a light zoom launch with his all wood Bird-of-Time. Half of the left wing did not like this maneuver, and decided to divorce itself from the rest of the airplane. An experienced pilot quickly grabbed the transmitter and through a series of truly heroic maneuvers and lots of left turns actually landed the remainder of the airplane intact.

The tip stall, while usually not fatal, tends to cut many launches short. How many times have you launched your plane in a crosswind only to see it dramatically zig or zag to one side or another? The upwind wing achieves flight speed well ahead of the downwind wing, resulting in a sharp roll to the downwind side.

The release is important in cross wind launching. I generally try to gauge the crosswind before launch, and tilt the plane slightly towards the wind when launching. By tilting the plane slightly into the wind, and giving your plane a solid heave, you significantly reduce the chance of tip stalling. If you tilt and heave properly, the entire wing will achieve flight speed immediately, and your plane will zoom straight up the line. If you do not tilt and heave, the downwind wing will often stall and the plane will immediately veer sharply to the downwind side. By the time you correct for this you will already have lost a lot of potential height.

For a windy launch, you can get a little more aggressive in the wind. If you are launching into heavy wind, you can take a much steeper ascent angle (more up trim) than normal, because your launcher may be doubled in power by the extra windspeed. If you are flying a light plane, you also need to be a little wary of this extra power, and be prepared to put some down trim in if the wings start bending excessively or flapping. I've actually seen very few planes break up on high-starts, unless the plane was a total mismatch for the high-start. In general windy weather really adds zip to your launch with low risk.

When you reach the end of your towline (as often happens on windy days), you may notice that the model is still being pulled down by the highstart and won't come off the towhook. Generally some down elevator is required to get it off the hook. If you have a real problem with the high-start pulling you down on windy days, there are two solutions. The first involves adding another 50-100' of line to the highstart. I generally carry a 75' spool of precut line for use on windy days.

The second option is to do a mini-zoom launch. This maneuver involves purposely putting the plane in a dive to gain speed, and then sharply pulling up after the plane separates from the high start to trade your speed for altitude. Push the nose down to level as your plane starts to slow down to avoid a stall. This can be done with any plane, and if executed properly will result in at least a slight altitude gain. If you have a wooden spar wing, you need to be cautious, since a hard zoom can lead to a wing break with subsequent plummet and swearing. Carbon-fiber reinforced spars will generally take anything a high-start can throw at them.

For a winch launch in wind there are two primary techniques. The zoom launch, as described above, should be used only with very strong airplanes (fully sheeted, carbon fiber spars, etc) in windy conditions, and basically involves using a heavy foot and lots of up elevator on the launch, followed by a strong dive and zoom when the plane nears apogee on the line. For further information on zoom launches see section ( ).

A second, more gentle method is to kite the plane up the line, and may be used with any airplane. This technique involves relying on the wind speed to carry the plane up the winch with minimum pull from the winch itself. The launch starts normally with tension and launch. Once airborne, one tries to pulse the winch as slow as possible while still retaining a solid climb. In heavy winds, you can literally "kite" light planes up the winch using very little pull, and achieve launches very close to the length of your launch line. A light zoom can be added at the end to increase height if your plane can support it. I never recommend zoom launching from a winch without a carbon reinforced wing, however - the risk is too high.

7.3.3 Finding Lift in High Winds

Where do you find lift on a windy day? Before you can find it you need to understand how the wind affects the thermals we all seek. Wind fundamentally changes the way thermals form, rise, and join to create larger thermals at altitude.

Thermals and Wind

On a dead calm day, thermals generally form directly over some kind of dark ground like a parking lot or farmers field. Fundamentally all that is needed is some ground that is a few degrees hotter than the surrounding area. Thermals form like big bubbles near the ground, until a large enough bubble is formed to break free of it. Once free, the thermal essentially rises straight up, expanding as it goes. Eventually, it may meet up with other rising bubbles to form larger thermals. The air surrounding the thermal is typically "down" air because some cooler air falls around the thermal to replace the warmer air rising. In the middle of the thermal there is often a hot "core" of warmer, sharply rising air. On calm days, you try to find some favorable air, and then begin circling trying to stay as close to the core as possible, and the sink surrounding the thermal usually lets you know when you've flown out of it. Staying in a strong thermal is quite easy since the thermal only changes position slightly as it rises.

The situation on a windy day is much different and vastly more complex. The nice bubbles rising vertically from thermal sources have been replaced by what Dave Thornberg calls The River of Air . In the river of air, thermals no longer rise directly from their source, and may in fact rise some distance from their source. Near the ground, all kinds of turbulence is created by the wind moving across and around trees, buildings, slopes, etc. The situation near the ground is not at all unlike watching water move down a rapids, forming eddies around rocks, bends, and slopes in the river bed.

Some facts about the river of air:


  • Wind Speed - The speed you perceive at the ground is usually much less than the wind speed aloft. This is due to the fact that air at grass level is not moving at all. A foot off of the ground, its moving a little faster, just as 100 feet off the ground its moving faster than the speed you perceive from a height of six feet. Adding 5 knots to your perceived wind speed gives you a good guestimate of winds aloft.
  • Wind Direction - The human mind tends to play tricks on us. One particularly annoying feature is its attempt to place order where their is none. No matter which way the wind is actually blowing, your mind will try to tell you that the wind is actually blowing parallel to one of the four sides of your current flying field. Check this out next time you go flying with a little wind. You will most likely orient your search pattern to one of the field's edges. If you catch a thermal and try to chase it downwind, you will find yourself flying down a field edge rather than the actual wind direction. Finally, when you come in for a landing approach, you will likely come in perpendicular to an edge of the field rather than directly into the wind. If you want to be a better windy day flier, you need to break yourself of all of these habits, and always ask where the wind is actually coming from.
  • Thermal Formation - Thermals no longer statically form over a single source of heat on the ground. As air starts to heat near the ground, it is simultaneously pushed by the wind, often to cooler spots. As a result the air often needs heat from several sources before it will reach a critical temperature high enough to break free of the ground. The most likely place for this to happen is still your favorite thermal source at the field. However, its good to keep in mind that on windy days you need to look for stretch of favorable terrain upwind of your location, and not just a little patch of dark dirt. Also its good to keep in mind that the thermals will most likely be found downwind of the best thermal source, not directly over it.
  • Thermal Motion - Thermal sources and the thermals themselves drift with the wind. This is a critical fact that escapes many novices. If you hit a great thermal and begin to circle or S-turn, you will quickly fall out of it. Again, your mind will unconsciously orient your flying to its frame of reference (i.e. the ground), and you will begin to circle a static point on the ground. The thermal, and even its source will continue to move with the wind leaving you high and dry. In fact, you will drift upwind of the thermal, which on windy days is usually a very strong area of sink.
  • Slope Lift - On windy days, slope lift can form in strange places. Tree lines, very modest hills and slopes, and even cars or bushes can create lift at very low altitude. I've seen many experienced fliers play this turbulent low level lift for as much as 10 minutes, never losing or gaining much altitude. Small slope lift will usually appear directly above the obstacle, and be turbulent and narrow. An S-turn pattern is most effective for exploiting it.

    Locating Thermals in Wind

    Locating a thermal on a windy day is largely the same as finding it on a calm day. If at all possible you want to use strategy to find the thermal before you launch! The key to look for is a subtle shift in winds as larger thermals pass near your location. If you feel a cold wind pass through, feint a radio problem (see sandbagging in section ( )) -- it is most likely down air passing through the area. If you feel a nice warm breeze pass through and the wind calms or shifts to one side, launch and move in the direction of the wind shift. Remember that the wind will shift towards the thermal. The cold and warm breezes are a dead giveaway on a windy day. For additional thermal signs, refer to section ( ).

    If you can't find obvious pre-launch signs of a thermal, and you've already faked your third radio problem today, then launch and head a little downwind of the nearest dark earth or parking lot you can find. Unless you know where a thermal is, it's a good idea to search primarily upwind for two reasons. First, by heading primarily upwind you will always be flying into new air. If you fly downwind then turn upwind, you will likely fly into air you have already visited. Second, if you actually find a thermal downwind, you will have to follow it further downwind to stay in it. This will degrade into a dangerous game of chicken where you try to estimate how far downwind you can fly before bailing out to come home. In contrast, if you catch the same thermal upwind, you can ride it all the way down the field, and have more time and altitude when your plane starts drifting far downwind.

    At the tactical level, there are two basic flying methods based on the two types of prevalent windy day lift. First, let's examine tactics to exploit lift at altitude (i.e. more than 50 feet). At high altitude, try to free-flight your plane as much as possible. This is hard to do -- the natural tendency is to impose control over the plane in high winds, but save that tendency for maneuvers close to the ground. If you over-control the airplane at altitude, you will never pick up the subtle signs that indicate lift. You need to free fly it to find turbulent air -- yes you heard me right -- you want to find turbulent air. The tendency for most fliers is to try to get out of turbulent air, but on windy days thermals are turbulent . They tend to be narrower than calmer days, so the line between lift and surrounding sink is very thin. When you find turbulent air, look for any signs of lift. If you find some, put the plane up on one wing tip and turn into it.

    Now comes the most crucial part. As you begin to turn, let your plane drift with the wind . If the wind is blowing hard, you need to drift fast. A ten mile-per-hour wind is faster than most people can run for any distance. Your plane should be drifting at least that fast downwind. If you have a 15 mph wind, your plane should be sprinting downwind. Resist the mental model that tells you the thermal is not moving - it is moving at least as fast as the wind aloft. Also, resist the natural tendency to try to make upwind turns tighter than downwind turns. This will only result in a tip stall, because your plane is moving relative to the wind and not the ground. Make a smooth even turn with constant pressure on the stick, and your plane will naturally drift with the winds aloft. The whole action is a matter of will to fly steadily even though your mind perceives the plane flying much faster on its downwind leg than upwind.

    Turning evenly in the wind takes a lot of practice. It is almost like learning to fly all over again. If you practice drifting in high winds again and again, you will eventually get the hang of it, and will find that despite popular opinion, thermals do exist on windy days.

    Assuming you have been successful in drifting and climbing, the next problem you will be faced with is how far to take it. Drifting in a 10 mph wind will take you a mile downwind in only six minutes! Even if the thermal is a boomer, you may need all of the flaps and ballast you can muster to get back. How far you can range downwind is a function primarily of your airfoil, and to a lesser degree ballast. Any reasonable lead-sled full function sailplane can easily muster 20 mph with a little reflex and will likely make it back from a mile downwind given reasonable height. An average gas-bag like the gentle lady that can barely beat 15mph with ballast and full down trim will likely end up short of the trees at the end of the field. This is one more reason why fast planes perform better in wind.

    Ultimately, returning from downwind is a matter of practice. You need to experiment develop a feel for how far you can go with your plane. One final note on returning upwind. I highly recommend bringing the plane back at a slight angle. This has two advantages. First, you will be able to better see what the plane is doing. Second, you are less likely to fly through the severe sink that is directly upwind of most thermals. Exit the thermal at a slight angle coming towards you so you can see the plane, and judge how rapidly it is sinking.

    A different approach to windy flying is required below 50 feet. Below fifty feet you can encounter both small developing thermals and slope or wave lift. Determining which you are in is critical, since wave lift will stay put and thermal lift will drift. If there are no obstacles nearby assume it's a thermal and try drifting for a few circles. If you are over a tree line or hanging near a hill, or even a fence, it is probably slope or wave lift -- try some gentle S-turns into the wind to see if you can find the center. Alternately, if you really know your plane, you can sometimes camber it a bit to match the wind speed and try to stand in the lift. In either case, look for the core, and stay with it. Slope and tiny thermals can disappear rapidly if the wind shifts, so be ready to bail out and head for the landing circle.

    Chapter 6: Intermediate Trimming | Contents | Chapter 8: Intermediate Competition

    Copyright 1997-1998 Bradley J. Smith
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