ARTICLE DATE: March 1997

First question: What’s a trike? In aviation, trikes are two-axis weight-shift flying machines capable of speed ranges as low as 22-50 mph and as high as 30-95 mph. Gliding sink rates are 300-450 feet per minute and glide ratios are as high as 10:1, depending on the size and shape of the wing.

Handling characteristics also vary widely by manufacturer and model as well as the ergonomics, quality and durability. Most manufacturers offer an FAR Part 103 ultralight model, and there are several two-seat kits for the 51% amateur-built experimental category.

You must hold a pilot’s license to fly these, so you have to spend time and money learning to fly in conventional aircraft that has little in common with trike flying…sort of like going to truck driving school to ride a motorcycle. Some trikes are available as plans for those who like to fabricate.

How Do They Work?

Trikes are governed by the same laws of physics that conventional aircraft accommodate. This being the case, we still need a pitch stabilizing force either aft of the c.g. or forward as in a canard. To accomplish this, the trike’s wing is swept back, placing the outboard wing and tips behind the mid span.

This—combined with twist (washout) that varies the high angle of inci­dence at the nose to a low angle at the tip—provides the pitch stabilizing force necessary for trimmed hands-free, stable flight.

Varying the angle of attack to fly fast or slow is accomplished by the use of the control bar, which at a medium-speed trim would rest hands-off about half way between the pilot and the front spar of the tricycle.

When pulled in toward the pilot, it moves the tri­cycle carriage, engine and pilot closer to the nose of the wing. This forward c.g. shift lowers the angle of attack and increases speed: an elevator function on a con­ventional aircraft.

To accomplish roll, it is necessary to alter the shape of the wings as with fixed-wing, hinged ailerons. This is done by allowing the cross bar that holds the wing open to float sideways. Hinging on a restraining cable attached to the back of the keel, this motion is actuated by moving the control bar sideways, causing the cross bar to shift to one side, opening one side of the airframe, flattening and lowering the trailing edge, while simultaneously closing the other side. Twist is added there, and the trailing edge is raised, causing a turn. Because of the wing’s sweep and twist, aileron and elevator function are combined. In an air­ plane, this would be called elevon function.

Trikes don’t have a rudder to control the yaw axis but use a dart-like or weathervaning tendency induced by the drag force generated at the wingtips. The trike can be stalled at a high angle of attack by pushing the bar all the way forward.

Because of washout, the stall occurs inboard first, which shifts the center of lift out toward the tips, which remain unstalled and lifting. Wingsweep now places the lift at the tips (well behind the c.g.), which pushes the nose down, reestablishing smooth inboard flow and returning center of lift to the c.g.

This action causes the bar to monetarily move back toward the central trim position from the stalled, pushed-out position—a phenomenon called negative pressure. Adjusting the trim to accommodate load or speed requirements is accomplished by moving the hang point where the trike attaches to the wing. The pivot or hang point is moved forward for faster speed or heavy loads, or aft for slower speed or light loads.

This is done on the ground by sliding the hang point in front of or behind a removable stop on the wing’s keel. Trim can also be done in flight with an electric actuator that I sell. Ideally, trim is set at best glide angle (maximum L/D), which would typically a few mph faster than best sink rate. The control bar would rest hands off just short of half way between the pilot and the front strut of the tricycle.

Training to Fly One

It is typical for a transition pilot to react with oppo­site control input or to freeze up on final approach and in steep turns; the trike flight instructor must to be on guard even though the student has demonstrated a period with proper use of the flight control.

For a high-time pilot planning the transition to trikes, it’s important to put all assumptions of necessary train­ing time aside or it can be a frustrating and awkward experience. It’s better to go in knowing that you are most likely going to spend a few hours being a klutz even though you are used to being a really good pilot.

Once acclimated, you will find that trike flying is very natural and enjoyable while you hone your new skills with your instructor. But this transition may well take 10-15 hours. New pilots and experienced airplane pilots can take about the same time to master the trike control response. I find that new pilots are more gradual learners as opposed to a more abrupt grasping of the situation by high-timers.

The more experienced pilots must remember to use caution due to the novellas of the trike until the action/reaction scenario is clearly established in the subconscious. I put the new students in the back seat of the trike for about an hour until we establish a rapport in our communication and have some exposure to pattern, approach and landings.

Once this is accomplished, the student goes up front with access to the throttle and brake pedals. For this, the trike needs to be equipped with dual steering extensions for the front fork and the wing, as well as an easily accessible throttle and kill switch for the instructor to maintain authority over the situation from the rear seat. The tandem seating arrangement is friendly with instructor and student actually touching each other, like riding tandem on a motorcycle.

While landing, the instructor follows through with the tran­sition student on the bar extensions or with the palms of your hands behind the student’s elbows to avoid an inadvertent reaction of pulling the bar back and putting us onto the ground nosewheel first.

I weigh just 115 pounds and fly in most cases with just my index finger and thumb on the control bar. But when ther­mal soaring at slow speeds, it is necessary to be more assertive with the wing, and this can be a challenge; not everyone likes this kind of aggressive flying.

Ground steering is also different from airplanes. Nosewheel steering is like a child’s tricycle and is therefore reversed; push left to turn right on the ground. The feet also operate two additional pedals. The left pedal is a wheel brake, and the right one is a supplemental throttle for momentary power changes when both hands are needed on the control bar such as for takeoff and landing. The primary throt­tle is on the side and can be set for cruising.

“These powered hang gliders offer a lot of performance and fun.”

Turning the trike in the air is initiated by lowering the wing in the direction you want to go. Let’s compare it to driv­ing a car. In a conventional aircraft, roll is begun as if your hands are on top of the steering wheel. In a trike, however, it is like driving with your hands on the bottom of the wheel: Move the bar left (which moves you and the entire tricycle including the engine to the right) to roll to the right.

Once the bank angle is established by the appropriate movement in either aircraft, the controls are neutralized to maintain the bank. Depending on airspeed, bank angle, and type of trike wing, the control bar is pushed out slightly to maintain altitude and airspeed while in the turn. This is like using back pressure on a stick or yoke while in a turn.

Landing is conventional aside from the different control movement and a fast approach so that as you pass through 50 feet AGL with the bar already pulled in and held. The wing having attained an appropriately fast speed will have a positive pressure (you’re holding back; it’s pulling forward) that is trying to restore itself forward to the trim position. Close to the ground, this is followed by a smooth roundout that is simply letting the bar move forward, releasing some of the forward pressure to fly level in ground effect. Then, as the airspeed bleeds off, the bar is pushed forward to maintain the glide until the desired landing air­ speed is reached.

As the trike settles and touches down, a little more push on the bar will make the wing flare, resulting in a nice, soft landing. Recovery from ballooning during a landing is accomplished by pulling the bar back to the appropriate position for a slight descent for the remaining airspeed, followed by a push and flare at touch­ down. After landing, the bar should be pulled to neutral or just slightly back from there to prevent unplanned flight and to keep weight on the nosewheel for positive ground steering.

Questions, Anyone?

Here are answers for two commonly asked questions from conventional pilots: First, yes a trike can spin if it is aggressively forced with exaggerated control inputs. This is accomplished by pulling the high wing (known as high-siding the bar) while aggravating the stall by pushing out all the way.

You might get a one-turn spin before the nose drops and the stalled wing begins to fly again. Proper recovery from this unchar­acteristic position would be to neutralize the bar or to facilitate recovery by pulling on the bar momentarily. Spins are not characteristic of trikes and do not pose a concern in normal operation.

Second, yes trikes can land in a cross­ wind. This is accomplished by flying crabbed into the crosswind while main­taining ground track on final. After the flare, enough roll input is initiated to point the nosewheel in direction of trav­el but not so much as to roll into a bank. The result is a landing as uneventful as with a direct headwind.

In Summary

Flying a trike is just enough different from the regular light plane to challenge the conventional pilot. It is like a wind­ surfer, motorcycle and bird all rolled into one. You’re out in the open and the view is great!

Trikes are portable and offer very natural and fluid flight. I recommend spending a few hours getting to know one. They are great fun to fly. CREDIT: Kit Planes Magazine

John Kemmeries is a USUA weight­ shift trike instructor and an advanced­ rated hang glider and aerotow adminis­trator with the USHGA, the hang glider national organization.

Prior to flying hang gliders, he was a member of the Sky-High Pioneers parachute team in the Phoenix area in the mid 1970s and made more than 160 jumps before a serious parachute accident put him on crutches. Yet today he averages 100 hours of flight instruction per month.