Historically, ultralights and
ultralight trainers with wings mounted above a tricycle undercarriage have
been called trikes and powered hang gliders. In sport pilot/light-sport
aircraft the FAA officially named this two-place lightsport aircraft category
a “weight shift aircraft.”
Trikes first appeared in the late 1970s when
hang gliders evolved from primitive delta wings to efficient flying wings
with higher aspect ratios, defined airfoils, and wing twist providing
stability and performance. The wings have evolved over 25 years along with
hang glider wings to be highly refined performance machines. Trikes have been
certificated to strict government standards in Europe and Australia.
how a trike flies
First, it’s important to understand that a trike
is trimmed to fly at a certain speed (we’ll use 45 mph). In calm air you can
let go of the controls and the trike will fly straight and seek the trim
speed designed into the aircraft. Just as is in cars and airplanes, flying
hands off requires slight corrections in direction. Unlike airplanes, which
have three axes—ailerons (roll); elevators (pitch);
and rudder (yaw)—controlled by a stick/yoke and rudder pedals, the trike has
two axes—roll and pitch—that are controlled by a bar connected to the wing.
The design of the trike’s swept wing, with a
certain amount of twist and airfoil shape, provides automatic yaw control. In
other words, trikes are comparatively easy to fly because you are only
controlling two axes rather than three axes. An easy touch on the controls is
the key to learning to fly a trike. When you shift your weight to one
side of the trike, it warps the wing by providing more twist on one side than
the other. Similar to the Wright brothers’ wing warping, the increased twist
generates more lift on that side, and that produces roll.
In the 1980s, when hang gliders evolved from
crude delta wings to flying wings, the “floating crossbar” became the
industry standard control system. This simple wing warping is the key to the
weight-shift wing efficiency and rapid roll response. To pitch the nose up
you simply push on the bar, and you pull it toward you to pitch the you pull
it toward you to pitch the nose down. Control is intuitive because you have
hold of the wing, and it goes wherever you move it. The motions are similar
to riding a bicycle or motorcycle.
Airplane and trike controls are different, so
airplane pilots will have to “unlearn” their stick and rudder skills when
learning to fly a trike. Adding to the difference is the sitting in the open
and the loss of the airplane’s “window” reference to the horizon. Typically,
airplane pilots feel disoriented for the first 20 minutes and must think
about the necessary control inputs for the first hour or two. Normally,
airplane pilots are comfortable flying trikes after about two hours in the
air, and many have developed the proper “habits” and are ready to solo after
five hours. Some pilots pick it up immediately, and others take a little
longer. It is no big deal to learn to “fly the wing” rather than move and
coordinate the controls.
Stalling the wing of a trike is an easy, gentle,
and forgiving manoeuvre. The wing’s “nose” is at a higher angle of attack
than the wingtips. At high angles of attack the nose buffets first, loses
lift, and naturally falls through while the tips in back keep flying. In
addition, with the weight of the cart and occupants below, the pendulum
effect naturally brings the nose down. Both factors result in a
speed and range
Traditionally, trikes have flown in the
slow—30-40 mph cruise and 25 mph stall—and medium—40-60 mph cruise and 30 mph
stall—speed ranges. With newer wings and larger engines, trikes are now
moving into the fast speed range, cruising at 60 to 90 mph. The wing’s size
affects speed. A trike with a large 19-meter wing (200 square feet) will fly
slowly. A 16-meter wing (170 square feet) gives you the medium speed range.
And a small wing, 11 meters (115 square feet), provides the fast speeds
A trike undercarriage (or chariot) can be fitted
with different wings, which means you can easily expand your flying options
by having more than one size wing. Generally, the wing represents about 25
percent of the trike’s total cost, but smaller wings generally need more
engine power. New trikes currently being tested have enclosed cockpits to
keep the wind off you at higher speeds. We will see trikes evolve into higher
speed machines considering creature comfort and fuel efficiency. Speed is one
part of the range equation. Endurance—how much time you have in the fuel
tank—is the other. A trike cruising at 50 mph for three hours will travel
roughly 150 miles— nless it’s flying into a head wind, which reduces the
distance. Trikes are powered by two- or four- ycle engines. With the same
fuel capacity, four-cycle engines give better range because they use
significantly less fuel than the two-cycle engines.
Generally, an intermediate or advanced trike
pilot can fly in a head wind that’s about two-thirds your stall speed and a
crosswind of one-half your stall speed. Trikes and fixed-wing aircraft can
taxi, take off, and land in comparable crosswind conditions. The
configuration and size of the wing affects crosswind capabilities for both
types of aircraft. Higher-speed aircraft typically have greater crosswind
capabilities because higher speeds mean less crab angle on approach.
To land a trike in a crosswind, you line up on
the runway centreline naturally crabbed into the wind and fly it crabbed to
touchdown. As your back wheels touch, the nose wheel swings around straight
down the runway. Crosswind takeoffs are similar. When you lift off the
runway, the wing naturally weathervanes into the wind setting up a crab angle
for you to proceed directly down the centreline of the runway. Naturally,
each pilot’s wind limits depend on his or her experience. In turbulence, the
wing moves more than the undercarriage resulting in less bumping around.
Because the weight is under the wing, the undercarriage naturally wants to
seek level flight. In moderate to severe turbulence you must hold onto the
bar, which takes some muscle and can be fatiguing on long flights.
Trikes have an advantage over airplanes —no
tail—meaning they are not burdened by the weight, drag, and down-force
associated with the tail structure. This gives trikes better climb rates and
the ability to carry greater loads.
For example, with a small but efficient 50-hp
engine, a medium trike can climb 1,000 feet per minute, and (with oxygen) it
is possible to climb to 17,000 feet. Fully loaded with two people, it will
climb at 500 fpm at sea level and can reach 11,000 feet. In this
configuration of small engine, low drag, and medium wing, the trike stalls at
30 mph, flies hands-off at 45 mph, and has a maximum cruise of 65 mph. A
large engine (100 hp) on a single-seat chariot with a smaller wing (13
meters) climbs at 60 mph and 2,000 fpm. Your speed, climb rate, and service
ceiling depend on your configuration.
Trikes are efficient aircraft and glide nicely
at about a 6-to-1 glide ratio with the engine shut off. It is common practice
to shut down the engine and land on a spot.