“TRIKE TALK”
By Dick & Jim
What is a “TRIKE” anyhow?
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Ultralight aircraft which looks a lot like Hang
Gliders with a tricycle undercarriage suspended
below that the pilot sits in.
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Weight-shift rather than aerodynamic control
and have flexible, rather than rigid wings, and
have no tails.
Why is it called a “Trike” not a
powered Hang Glider?
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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.
Why Fly A Trike?
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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.
Why Fly A Trike?
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(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.
They’re 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!
The Main Bits
The Main Bits (cont.)
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,
it’s a foot throttle – just like a car.
 Your left foot has a nose wheel brake pedal.
 And apart from the ignition switch & choke, that’s
basically all there is!
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”.
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)
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.
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).
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.
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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
Questions?