A most important concept to understand when deciding if radical aerobatics is for you is that it involves flying upside down on a wing from which you are hanging by a flexible link.  It all works fine if you always carry enough energy through the maneuver so the centrifugal force keeps your harness straps tight.  However, people make mistakes, especially while learning.  If you intend to pursue radical freestyle hang gliding be advised that you are opening yourself to the potential of a drastic situation.  You can minimize your chance for disaster if you proceed at a cautious rate, and gradually increase your knowledge and ability over the years.  This takes a responsible attitude.

I know people who allowed their ego to hurry them into radical aerobatics with tragic results.  A pilot had asked me "how much turbulence is safe for looping?" Each experienced pilot has his own feelings on what level of turbulence is too much, and it is nearly impossible to articulate.  The best answer is "stick to dead smooth air".  Then if you get hurt you will know it was your fault and not some inopportune turbulence you drove into.  Weeks later this pilot blew-up a glider because he was looping in too-turbulent conditions.  He got his chute out but it was too small for his weight.  He hit hard, badly dislocating his shoulder.  That was a year ago and he still cannot fly a hang glider.  Radical aerobatics can radically affect your life.

There are however, some benefits derived from learning how to do mild aerobatic maneuvers.  The benefits are a more in-depth knowledge of your glider's control capabilities, and greater awareness of, and confidence in the strength of your wing.  High-speed handling is an aspect of flight that some hang glider pilots never explore.  I feel that it is important if only to allow a more relaxed attitude during the necessary high-speed approach to landing in a turbulent LZ.  It is better to familiarize yourself with high-speed control when you are high and comfortable than to learn it in a difficult situation when you have serious decisions to make.

Modern hang gliders are very strong aircraft.  Many pilots never get a personal feel for how much load they can handle.  Of course it is NOT a good idea to test your glider's strength by pulling excessive G's.  Some pilots have found the load limit of their glider in this way.  It is difficult to do because it requires a steep, high speed dive with an abrupt pull-up, but once accomplished it always becomes a very interesting and pivotal point in one's life.  In an instant your existence comes down to just you and your parachute, and you have the rest of your life to figure out how to save yourself (which might be only seconds).

Mild wingovers will not overstress an airworthy glider.  It might put 2 or 3 G's on your wing, which is safe.  However, a stall at 90 degrees can be very dangerous.  It is best to start at 45 degrees and work up gradually only after you have developed smooth habits.  Remember, smoothness is more important than steepness.  This initial period of learning about your glider's reaction to control inputs at various speeds and G-loadings before you start getting steep is essential in developing a smooth style with its long-lasting rewards.

An additional benefit of practicing mild aerobatics is that you will have experience at unusual attitudes.  To become comfortable with unusual attitudes means you will be less likely to panic when you get upset by turbulence while flying in strong thermal conditions.  The reaction to any mistake in aerobatics is to pull the bar in all the way and hang from it if necessary (in certain cases perhaps movement to one side in addition).  The reaction to turb-induced stalls/upsets is the same.

EQUIPMENT

Any glider you fly should be airworthy of course, but if you plan to go out and intentionally "load it up" it makes sense to select a worthy wing, adhere to the manufacturer's maintenance schedule and preflight it attentively before launching.  All hang gliders can handle mild maneuvers.  Most are capable of steep maneuvers, but for radical aerobatics - choose wisely.

The characteristics I like in a glider are good dive ability, reasonably light pitch pressure, excellent energy conversion and quick roll response at high G's.  Of course superior strength is a valuable quality.  Those who live where there is no expert aerobatics pilot to talk with are at a considerable disadvantage.  You might know that your glider model has been looped, but if you cannot hear from someone that the glider converts extra energy rather than just enough to loop when technique is precise, your alternative is to experiment yourself.  Obviously this is not a safe situation if you are inexperienced.  Be sensible.

There is an experienced radical freestyle pilot in San Diego, California named Eric {the lifeguard) Smith.  Eric is a BIG man.  He is tall with long arms.  He hooks in at about 240 pounds (109 kilograms).  His great strength, long arms and high hook-in weight make him a hang glider's worst nightmare.  Eric can essentially load test a glider while flying it, which he demonstrated at Telluride in 1987.  In Eric's zeal to win the World Aerobatics Championship, he pushed out a little too hard during a rolling maneuver and broke his cross spar.  He got his chute out very quickly and survived the high elevation landing with some injuries.  A bigger chute would have helped.

Back then Eric was flying a metal airframe glider of course.  Today he flies a 160 TRX RACE carbon fiber glider.  Recently Eric decided he wanted to get back into looping.  He had not looped since his accident in 1987.  He got himself very high in smooth Santa Ana conditions at Elsinore and went into his max dive.  He was determined to find out if he could trust this glider.  To the best of his ability he duplicated the control inputs that had broken his other glider six years earlier, but instead of breaking, the glider pulled up into a graceful near-180 degree rollover.  Eric is back, and the carbon fiber age has arrived.

For any aerobatics the glider should be of unquestioned airworthiness, meaning no damaged tubes or wires, virgin downtubes, and a sail without excessive UV exposure.  Be confident of your main and backup hang loops.  There is nothing worse than precipitating out of your glider just when everything is going great.  Always use a steel carabiner, and be sure your harness is strong and of reasonably recent manufacture.  UV exposure degrades harness strength.  Check your harness for frayed ropes or straps and strained stitching.  Also check the construction of your harness by feel.  There should be webbing on the bottom, not just fabric.

There are new parachute designs on the market with smaller pack volumes for a given descent rate, but the old rule still applies - bigger is better.  Flying with two chutes is a good idea if the extra chute does not interfere with your ability to ball-up for the dive.  If you are making a custom harness for aerobatics, place the chute all the way forward for knee clearance.  A rocket chute might give you an advantage in deployment time in some situations, but hand-deployed chutes are un-complicated and proven.  Be sure your parachute has pins so it does not come out during high G's.

Although good fortune comes in many forms, I know of a pilot whose life was saved because his chute popped out during excessive G's when he broke both leading edges off an Axis 15 by pulling up too abruptly for a maneuver at 300 feet (90 meters)!  This is a pilot whom I had observed doing 120 degree wingovers, which looked fairly clean until he got just past apex when he would push out hard.  This would pitch the glider around quickly which ruined the flowing smoothness of the maneuver, and left him with little airspeed for the next maneuver.  The last word on parachutes is to get familiar with the deployment process of your back-up system.  Practice some deployment throws while hanging in your harness.

Type of harness is a consideration.  The trend in the general hang gliding community is toward pods of course, but the top aerobatics pilots in the USA still prefer the cocoon.  A cocoon with thin foam is the best for turning your body into a centralized mass (balling-up) for the purpose of getting maximum forward for the dive.  Some aerobatics pilots do well with a flexible pod.  You can get into max dive by doing an initial steep banked maneuver and dive out of it.  However, I am not willing to give up the ability to pull straight in from normal flight with little or no mush to achieve max dive for loops.  This is what the cocoon provides, and that extra confidence in your dive is valuable.

High Energy Sports makes a great cocoon for aerobatics.  It is thin for better balling-up and surrounds you with 2 inch seat belt webbing, all seven-class stitched.  Always have a hook knife on your harness.  When the time comes you will know why.

DYNAMICS OF A MANEUVER

Gliding aerobatics or freestyle as some call it, when analyzed as mechanical physics, becomes a matter of energy conversion, conservation and efficiency.  You build potential energy (due to the height of a mass) by gaining altitude.  You convert this stored energy into kinetic energy (due to the speed of a mass) by diving.  Once you have converted an adequate amount of potential energy into kinetic energy (by attaining a certain speed) you have to efficiently reconvert a portion of your kinetic energy back into potential energy as you climb to the apex of your maneuver.  At the same time you must conserve enough kinetic energy to carry you past the apex and into your next dive.

As a matter of physics it is fairly simple, but in reality the complexity is great enough that people have been killed trying to do it.  The process involves two key elements, the efficiency of the wing at high G loading and the knowledge and ability of the pilot.  The problem of the glider is simple.  You choose one that someone else has proven to be good for aerobatics.  The problem of knowledge is more difficult.  It is a trial and error situation since you cannot have a dual instructor.  Trial and error is a harsh way to acquire a life and death skill.  Perhaps it is not worth it to you.  Only you can make that decision.

Even if you can accumulate the knowledge there is yet another factor to consider.  It is some intangible facet of the mental make-up of the aerobatics pilot that allows him to operate upside down with intermittent loss of ground reference.  One of the finest, massively experienced aerobatic hang glider pilots in the world, who performs incredible and beautiful 180 degree rolling maneuvers cannot do loops because he cannot take his eyes off the ground.  Do not underestimate the affect of this aspect of the aerobatics mentality.  It might be responsible for many of the mishaps that occur on first loop attempts.  It is important to know your own limitations.

PRACTICING BASIC MANEUVERS

Intermediate and advanced pilots who are interested in expanding your knowledge of the control of your glider should begin by getting accustomed to speed and how your glider responds to roll inputs at high speeds and G's.  If you are in doubt as to your level of proficiency for this, always consult a senior pilot who is familiar with your level of experience.  Of course be high and away from the hill in smooth air for this period of feeling-out your glider so any over control will not put you into the hill.  Be sure to be well away from other flyers.

SMOOTHNESS

The most important habit to develop at this early stage is smoothness.  When I was first learning to fly fifteen years ago I happened to choose the home site of some excellent early pilots whose behavior I observed.  I learned much of what I know about hang gliding from David Beardslee.  The most outstanding quality of David's flying is his smoothness.  He launches smoothly, soars smoothly and lands smoothly.  He flies like a soaring bird, with maximum efficiency.  If you have occasion to watch him fly, notice his technique.  From the moment he starts his launch run, through his landing flare, every move he makes is smooth.

Smooth maneuvers look better; moreover, you are less likely to over stress your glider if you are smooth.  Smoothness means efficiency; therefore, to be smooth is to conserve energy.  Remember, energy management is what freestyle hang gliding is all about.  Because of the limitations of flexible wings there is little extra energy to squander.  Concentrate your attention to smoothness on your pitch control.  While it is important to be smooth in all aspects of your control, it is actually difficult to look jerky in roll.  Due to something referred to as apparent mass, a hang glider responds to roll inputs slowly, but to pitch inputs quite quickly.

There are only two times when it is OK to be abrupt with the pitch control during aerobatics: when trying to get aimed toward the ground for the max-dive and if you should stop inverted.  Note that both of these cases are pull-in.  Never be abrupt on the push-out.  I see people getting away with abrupt pitch control, but they are walking a thin line.  If you are too abrupt with pitch control one of three things might happen:

     1.   Over stress the glider and break a leading edge or cross spar (a world renown hang glider designer once did this)

     2.   Twist out the wing causing rapid loss of energy, possibly resulting in an inverted stall/tumble

     3.   Get away with it but the maneuver looks jerky

MILD WINGOVERS

Visualize a figure 8 lying on its back with the ends curved up.  Your mild wingovers should describe this pattern approximately, but do not confine yourself to it.  Each glider design has its own natural frequency or rhythm that it "likes" during these reversals from left bank to right bank etc.  Some are slow, some are quick.  Now is the time to learn your glider's rhythm before you get into steep bank angles.  Start with 40 to 60 degree bank without excessive dive between maneuvers, and remember smoothness.  It is impossible to practice too long.  The more you practice the smoother you will become.

STEEP WINGOVERS

There should not be a point at which you decide to stop doing mild wingovers and start doing steep ones.  The proper and safe way to proceed is to first get very, very comfortable at mild bank angles.  Then the transition to steeper bank angles should be automatic.  As you gain confidence you will find yourself diving longer between maneuvers.  The additional energy (speed) will allow a steeper banked maneuver.  If you pay your dues by long practice of the basics without progressing too quickly, you will be rewarded with a smooth appealing style.  Eventually (if you wish) you should find yourself rolling to near 180 degrees before even thinking about straight-over loops.

THE DIVE

When the time is right for you to start thinking about radical maneuvers your main focus will become THE DIVE.  There is great importance in your ability to get the glider diving steeply because the glider's pitch stability is intended to prevent it from diving steeply.  This restricted dive characteristic is a result of the designers' efforts to prevent inadvertent inversion.  Consequently, you can pull in all the way as abruptly as you wish (from any speed above stall) and you will not tumble provided you are flying a certified, pitch-stable glider.  In a sailplane you ease the stick forward and you are diving.  Most hang gliders take some technique to achieve the max dive.

I here some people say they whip stall to get into a dive.  I am sure they are just misinformed on terminology.  NEVER do any kind of aggravated stall in a tailless wing except when you flare to land.  To whip stall is to push out rapidly from a higher speed with the resulting potential of getting the glider much more nose high than if you ease out slowly from minimum sink speed.  A nose high stall spells tumble.  In the case of most gliders, in order to get the nose aimed at the Earth for the max-dive, you need to ease out to mush (NOT FULL STALL!).  Once into the mush range near stall you will feel some back pressure and the nose will start to drop.  Immediately go with this nose down motion and pull the bar in all the way as you ball-up and get as much of yourself as possible in front of the bar.  If you are nearly dead-in-the-air it stands to reason that if you should push out again right away you could tumble, so hold this position for at least 2-3 seconds.

Some gliders will start to pull out after 4-5 seconds due to their pitch stability.  Others will continue to dive as long as you hold your dive position.  If your glider starts to pull out of the dive it is time to pull up because you are losing efficiency, and you no longer have the energy you had.  The term "pull-up" means to exit the dive and start to convert your kinetic energy back to potential as you pass through pitch-level and begin to climb.  There is nothing more important to the safety of a radical freestyle pilot than competence and confidence in the dive.  If you are cut out to be a radical aerobatics pilot and you master this dive technique through long practice, you will have the means to do a straight over loop without the need for an initial speed-building maneuver.  If you are to become a safe and competent radical freestyle pilot, you must learn to love the dive.

Each time you practice a dive you end up with an amount of kinetic energy converted, and you will want to do something with it.  Resist the urge to try turning it into a radical wingover or loop.  The only way to develop accurate judgement as to how much energy you convert (or speed you build) is through long practice.  If you try to loop before you possess the judgement, you cannot be sure if you have enough energy to make it through the maneuver.  There is also the matter of "spending" your energy wisely (proper pull-up rate) throughout the maneuver.  Since there is little tolerance for wasted energy, it is essential to be sure through judgement.

There are two things you can do safely with your dive energy.  You can do a 90 degree wingover by starting your pull-up and then initiate hard roll input before you reach pitch-level.  This is not the best way to convert your dive energy into a steep bank angle, but at this point you are not trying to do steep maneuvers.  You are trying to perfect the dive and stay alive long enough to turn it into radical maneuvers.  For later, the way to convert maximum dive energy into climb energy is to initiate roll input just after pitch-level.  Do NOT try this until you have perfected the dive!  If you try this technique without enough dive energy, or without spending your dive energy properly on a glider that does not roll easily at high G's you might find yourself stalled going straight up.  If you stall at or near this attitude you WILL tumble.  Obviously this is to be avoided at all cost, so be wise and play it conservatively for now.  Start your roll before pitch level.  Be ready for excessive pitch pressure.  Some gliders develop fairly heavy pitch pressure on the pull-up, but if you experience excessive pitch pressure you are pulling up too rapidly.

The other thing you can do with your dive energy is something Eric Raymond told me about when I was preparing myself for loops.  He suggested I do straight-ahead 45 degree climb-outs as I pull up from the dive.  This allows you to experiment with a range of pull-up rates and find the rate that gives you the best regain of altitude.  The pull-up rate that leaves you the highest as measured from the bottom of your pull-up is right for maximum energy conversion.  Remember that this all out dive practice is an advanced stage of your training, and should be reserved until after you become very comfortable with mild wingovers.

A glider with loose side wires even when the VG is tight can display a phenomenon known as wing lurch.  While diving at a certain angle the wings oscillate between the limits of the top and bottom side wires.  This is not a structural problem; however for me it detracts from the exhilarating purity of the all out dive experience and possibly hinders efficiency.

REALITY CHECK

I have been conducting aerobatics seminars for the last four years.  My motivation is not financial since a psychological analysis of an aspiring aerobatics pilot would probably show that if he had money he would not have that special need to do loops.  I try to impress upon my students that they cannot expect to make great advancements during a two-day seminar.  They can only hope to pick up a few gems of information to take away and infuse into their learning. 

One notable student completely ignored my advice apparently thinking he was living in a separate reality.  On the second day of the seminar he quietly decided he was ready for his first loop.  He towed up to 3000 feet, did some wingovers and went for a loop.  He might have had enough energy to make it over, but at some point he lost his orientation (did not know his attitude).  He pulled in to abort the maneuver when he was past vertical and stopped going straight up!  He tumbled a few times and then the glider broke as he became part of the worst mass of rapidly rotating wreckage I have seen.  He was at about 1500 feet (450 meters) when he tumbled.  Once the glider broke he was rotating so fast that I feared he might not have the strength to overcome the G-force on his arms and get to his chute.  At about 300 feet (90 meters) he got his chute out and landed uninjured except for wire burns.

He says he has given up the idea of looping a hang glider.  This is a man who wanted to loop in the worst way, and he did.  It has been my observation that part of the incentive to loop is to gain the respect of your peers.  Think about this.  If you try it before you have prepared yourself with long practice at the basics and you blow it, you accomplish exactly the opposite effect.

I know another experienced pilot who wanted to show his friends how well he could fly.  His friends were visiting from abroad and he would not see them for a long time.  He towed up and tried a radical maneuver without sufficient experience (or airspeed).  As he tumbled he threw his chute with the glider still intact.  The type 18 parachute bridle happened to route past the left leading edge rear section as the canopy opened.  The motion of the glider and the great tension on the bridle caused the leading edge to break.  At the same time the bridle melted by friction with the lower side wire.  The pilot had removed the coating from the cables for performance increase although it is unclear weather that makes a significant difference.

Suddenly he was in a much worse situation than a tumble.  He had a broken glider and his parachute bridle had been cut.  He must have hit the ground on a fortunate up oscillation since he was not killed.  He suffered severe and lasting injuries.

There are many more stories like this one.  This is my motivation to write this information and do freestyle seminars.  I appeal to all pilots to use this information wisely.  Do not make the mistake of trying to enjoy the fun and freedom of aerobatic flight without paying your dues during a serious learning period.  Nothing is free.  One of the earliest lessons in life is: if you try to take something that you have not earned there is a penalty.  I know of several dead pilots who apparently thought this rule does not apply to freestyle hang gliding.

TEN REASONS FOR NOT DOING RADICAL AEROBATICS ON A HANG GLIDER

1.     Low margin for error, flex wing hang gliders can convert little more energy than necessary for one loop

2.     Tailless wings can tumble when stalled, especially at unusual attitudes

3.     "Hanging pilot" configuration does not allow for negative situation

4.     The necessary pitch stability designed into a flex wing hang glider makes diving difficult

5.     Trailing edge flutter can occur at looping speed causing sail condition degradation

6.     Danger of diving into unnoticed pilots flying below

7.     Excessive G loading by heavier pilots might stretch sail

8.     Considerable practice time required curtails cross-country flying

9.     Mistakes are often life threatening  (for comparison, mistakes in sailplane aerobatics are seldom life threatening)

10.   Your mother will sleep better

DEFINITIONS

Mild maneuvers -       90 degrees bank angle or less

Steep maneuvers -      90-120 degrees bank angle

Radical maneuvers -   120-180 degrees bank angle and spin

Wingover -        colloquial term of hang gliding aerobatics meaning a non-stalled maneuver in which increased airspeed is traded for momentarily higher than normal bank angle with an approximately 180 degree heading change

Apex-   highest point in the maneuver

Pitch level -       lowest point in maneuver when cord line (or keel) is parallel to horizon

G's -  force due to change in speed or direction causing loading on glider and pilot

Tumble-   sudden and violent nose down rotation about the pitch axis initiated by aggravated stall   Rotation can continue indefinitely if pilot weight remains behind hang point.

Attitude -  relative orientation of glider using the Earth's surface as a frame of reference

Spin-   condition in which part or all of the inside wing is stalled and radius of rapid yaw rotation is much less than that of a normal coordinated turn (usually less than half span)

TEN IDEAL CONDITIONS FOR LEARNING RADICAL AEROBATICS SAFELY

1.     Home flying site with smooth "glass-off" type conditions at which you can soar at least 2000 feet AGL (920 meters)

2.     A schedule/weather situation that allows you to fly at least four times per week

3.     A local hang gliding aerobatics expert who can observe and coach you frequently

4.     A recently manufactured high performance glider of a model that has been proven by an expert to be aerobatically worthy

5.     A strong, very flexible harness (preferably thin-foam cocoon with back strap)

6.     A large parachute (with hand deploy option if rocket extracted)

7.     A hook-in weight of less than 200 pounds (90 kilograms)

8.     Good physical condition and muscular coordination

9.     A responsible attitude with cautious enthusiasm and good spatial orientation ability

10.   Trust fund income

Published in July 1994 HANG GLIDING Magazine