TRIKE TALK

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TRIKE TALK
By Dick Jim
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What is a TRIKE anyhow?

• Ultralight aircraft which looks a lot like Hang
  Gliders with a tricycle undercarriage suspended
  below that the pilot sits in.
• Weight-shift rather than aerodynamic control and
  have flexible, rather than rigid wings, and have
  no tails.

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Why is it called a Trike not a powered Hang
Glider?

• While sharing similar technology, modern Trikes
  are not Hang Gliders.
• Calling them Hang Gliders leads to some
  difficulties in such things as sales tax.
  Aircraft (other than gliders and hang gliders are
  exempt in Australia from sales tax and import
  duties.
• Therefore, Trike (derived from the tricycle
  undercarriage) or Weight-Shift Ultralight are
  the Politically Correct terms.

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Why Fly A Trike?

• The performance of modern Trikes compares
  favorably with conventional Ultralights. Cruise
  speeds range from 30 to 70 mph, and have among
  the most spectacular climb rates of all
  Ultralights.
• New Trikes are generally cheaper than new
  conventional Ultralights.
• There are less moving parts to go wrong.
• Trikes have an enviable safety record.

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Why Fly A Trike? (cont.)

• Can be assembled or disassembled within half an
  hour and easily transported.
• You can store it in your garage and still have
  room for your car.
• Theyre the motorcycles of the air.
• Can do most anything or go anywhere in a Trike
  that you can in any conventional Ultralight
• .AND HAVE MORE FUN DOING IT!

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The Main Bits
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The Main Bits (cont.)
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So, How the Heck Does it Fly?

• The controls, what there are of them
• The Control Bar is the primary control. With it,
  you can move the whole Trike undercarriage fore
  aft and side to side under the wing. This will
  control Pitch and Roll.
• You have a throttle, but unlike conventional
  aircraft, its a foot throttle just like a car.
• Your left foot has a nose wheel brake pedal.
• And apart from the ignition switch choke,
  thats basically all there is!

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So, How the Heck Does it Fly?

• Aerodynamics of the flexible wing
• The flexible swept wing airfoil provides high
  lift, a high L/D, a small pitching moment and
  subdued stall characteristics.
• The undercarriage (trike body) is suspended from
  a pitch roll joint attached to the wing
  structure.
• Angle of Attack and Roll are controlled entirely
  by shifting the trike body either to the sides or
  fore and aft via pilot pressure on the control
  bar (A-frame).
• This action effectively shifts the CG in relation
  to the wing aerodynamic center, hence Weight
  Shift.

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So, How the Heck Does it Fly?

• Pitch Stability (without a tail)?
• The wing is aerodynamically balanced in pitch
  because a download is applied at the rear of the
  wing by a reflexed airfoil (the T/E is bent up
  reverse cambered) and the outer wing sections are
  washed out.
• Wing is flexible, root cord always has highest
  AOA, and the tips the lowest.
• Pitch stability is derived from the reversed CP
  movement as AOA increases the CP moves backward
  which pitches the nose down (see next page)

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So, How the Heck Does it Fly?

• Pitch Dynamics

Wing root high AOA, wing tips low AOA. Spanwise
tension tries to keep the tips as flat as
possible.
Tip AOA increases, root already close to max
lift. When root stalls tips still lifting. Tips
behind you forces nose down (positive nose-over)
Speed up, the tips dump load, the root is major
contributor of lift. Since the roots aerodynamic
center is FWD, you get bar pressure that opposes
the speedup.
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So, How the Heck Does it Fly?

• How a Flex Wing turns
• With roll input from pilot, the Cross-bar
  (spreader) is allowed to float slightly w/respect
  to the keel, and allows the sail to billow
  shift (example On ground, grab T/E of one wing,
  and push up, you would notice the other wing
  become tighter).
• The extra load on the inboard wing causes sail to
  shift to that side. That tightens the sail on the
  outside wing, increasing AOA, while decreasing
  the AOA on the inboard wing (see diagram below).

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3-Axis Conversions

• Are you a 3-Axis pilot thinking converting to
  (or trying) Weight-Shift?
• Trikes have reverse sense controls compared with
  3-Axis aircraft.
• Pull control bar toward you to speed up, and away
  to slow down.
• Move control bar right to turn left and vice
  versa.
• Nosewheel steering is billy-cart style. Push
  right, go left.

You can be a Bi-Wingual Pilot
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Questions?