Far Back View
Top View
Figure 3-20. Shifting weight to the right pulls the keel to the right
(or lets the crossbar shift to the left) and increases twist on the right
side for roll control.
Strap attached to crossbar
that goes around wing keel,
limiting its travel side to side.
Figure 3-21. Crossbar travel limiter.
Figure 3-19. Hang point wing attachment.
Trim Systems
There are a number of trim systems to relieve the control
pressures for pilots to fl y at different “hands off” trim speeds.
Ground adjustable trim allows the pilot to adjust the trim
speed of the wing on the ground and remain at one speed
during fl ight, while fl ight adjustable trim systems can change
the trim speed in fl ight.
Ground Adjustable Trim Systems
The most common ground adjustable trim system, and typical
of most aircraft, is moving the wing attachment hang point
forward for faster trim speeds and aft for slower trim speeds.
Each manufacturer has different hardware, but the basics of
sliding the carriage wing hang point forward and backward
on the keel is similar for all. As an example, moving the
hang point at the furthest aft position to the furthest forward
position could speed the wing up 20 knots. This in turn
moves the control bar position back to a new “hands off”
trim speed.
pull the control bar in to control pitch. This wing attachment
is different for each manufacturer, but all designs have this
hang point wing attachment so the control bar is always
perpendicular to the longitudinal axis of the aircraft. This
raising and lowering of the nose is the pitch control system
for the WSC aircraft. [Figures 2-7 and 3-19]
Roll Control System
Control bar movement from side to side controls the roll about
the longitudinal axis. The wing attachment hang point allows
the carriage to roll around the wing keel. Thus, it can also be
looked at from the carriage point of view, when the control
bar is moved side to side, the wing rotates around the wing
keel relative to the carriage. [Figures 2-31 and 3-19]
It would fi rst appear that moving the control bar to one side,
thus shifting weight to the opposite side, could alone bank
the aircraft. It is true that shifting weight to the right would
naturally bank the aircraft to the right and put it into a right
hand turn. However, the weight alone is not enough to provide
adequate roll control for practical fl ight.
As weight is moved to one side, the keel is pulled closer to
that side’s leading edge. The actual keel movement is limited
to only 1 to 2 inches each side of center. However, this limited
keel movement is suffi cient to warp the wing, changing the
twist side to side (as discussed earlier in the aerodynamics
section) to roll the aircraft [Figure 2-24] by changing the
lift side to side. Simply, the shifting of weight from side to
side pulls the keel toward the leading edge on that side and
warps the wing to roll the aircraft.
Besides the keel shifting relative to the leading edges and
crossbar, overall roll control is adjusted by the designers to
fi t the mission of the wing through sail material/stiffness,
leading edge stiffness/fl exibility, amount of twist, amount
of travel the keel is allowed, airfoil shape, and the planform
of the wing. [Figures 3-20 and 3-21]
Figure 3-24. More tension on elastic pulling down on the rear of
the wing keel reduces the trim speed and is controlled by the pilot
in flight.
Front Keel
Front Kee
Elastic pulling
down on keel
raising nose.
Keel Pocket
Keel Pocket
Real Keel
Real Keel
NoseNose
Figure 3-22. A crank on the downtube of the control bar that adjusts
the trailing edge reflex during flight.
Figure 3-23. Hydraulic inflight trim systems that move the hang
point in flight controlled by the pilot.
or electrical systems can move the hang point on the wing
for other infl ight trim systems. [Figure 3-23]
Another pilot-actuated trim system in fl ight is an elastic
system in which the pilot increases tension on the elastic
system which raises the nose for climb and slower fl ight.
[Figure 3-24]
Carriage
The carriage is a completely separate structure from the
wing. Without the wing, the carriage can be driven around
if needed. Most of the weight and cost of the WSC aircraft
is in the carriage. There is a wide range of carriage designs
from the most simple and basic open trikes to the more
sophisticated and complex trikes that integrate cowlings and
offer a number of adjustments for the pilot and passenger,
resulting in comfort and less fatigue during fl ying. Generally,
Another less commonly used method of increasing trim
speed is to increase tension on the crossbar by pulling it back
further, slightly increasing the nose angle and reducing twist.
This increases the angle of attack (AOA) of the tips producing
more lift, and it lowers the nose to a higher trim speed. This
is a typical in-fl ight trim adjustment for high performance
hang gliders. The roll control is diminished with this faster
and stiffer wing.
Ground adjustable trim systems are described in the Pilot's
Operating Handbook (POH) for each aircraft. Different loads
may require different pitch settings.
Infl ight Adjustable Trim Systems
Being able to adjust the trim systems in fl ight has a number of
advantages as discussed later in the fl ight sections. A number
of infl ight adjustable systems are available with different
manufacturers. A common in-fl ight adjustable trim system
is raising and lowering the trailing edge. Raising the trailing
edge increases airfoil refl ex and slows the wing. Lowering
the trailing edge decreases airfoil refl ex and speeds up the
wing. Typically, a crank on a downtube controls a wire that
runs up the downtube to the top of the wing. As a result of
moving the crank, the trailing edge wires are raised and
lowered and the trim speed changed. [Figure 3-22] Hydraulic
Engine Mount
Seat Frame
Front Fork
Carriage Mast
Front Tube
Carriage Keel
Carriage Wing Attachment “Hang Point”
Wing Keel
RIGHT HAND MAIN
LANDING GEAR*
Shock Strut
Main Strut
Drag Strut
Main Landing Gear Tires
Front Landing Gear
Nose Wheel Steering
* Conventional configuration shown with other configurations
described in main landing gear section of this chapter.
Figure 3-25. Simple basic trike (left) and sophisticated trike with adjustments for pilot and passenger (right).
Figure 3-26. Basic components of the carriage structure.
the more complex the trike, the more it costs, weighs, and the
more power it requires for similar wings. [Figure 3-25]
Structure
Similar to the wing, the carriage is designed with a number
of structural triangles for optimum strength and minimum
weight. Each manufacturer and model have specific
details that vary, but
the carriage structure is
typically a mast, keel,
and front tube that
form the main triangle
components of the
carriage structure with
the wing attachment
at the top of the mast.
A seat frame attached
to the mast and keel
provides rigidity to the
main components while
providing structure for
the pilot and passenger.
[Figure 3-26]
Landing struts attached
to the rear wheels
provide structure for the
main landing gear, and
a front fork provides the
landing gear structure
for the front wheel. An
engine mount attaches
to the mast, providing
structure for the
propulsion system to
attach to the carriage.
[Figure 3-26]
Landing Gear
The landing gear provides support to the WSC aircraft on
the ground and absorbs the shock to reduce the stresses on
the pilot and the aircraft during landings.
Steering Rod Damper
Figure 3-29. Steering rod damper.
Figure 3-30. Mechanical drum brake system.
Figure 3-27. Large foot rests used for steering the aircraft on the
ground (left hand ground brake shown).
Rear Steering
Connection
Rod to Front Fork
Front Seat
Steering
Rear Seat
Foot Steering
Figure 3-28. Foot steering control for instructor in the back seat
and connecting rod to front fork.
The landing gear is made up of the front wheel, which has
a lighter load and is used for steering, and the main or rear
landing gear, which takes most of the load for the aircraft.
[Figure 3-26] The front steering fork for the nosewheel has
foot rests attached that the pilot uses for steering the WSC
aircraft on the ground. Besides ground steering, the foot
controls are similar to driving a car, left foot pedal is brakes
on the ground only, and right foot is throttle and power on the
ground and in fl ight. [Figure 3-27] The front fork typically
has camber so it naturally tracks in the direction of travel
similar to a motorcycle front fork.
For training, a second steering control is installed with a
connecting rod so the instructor can sit in back and steer the
carriage on the ground using the nosewheel. [Figure 3-28]
Steering dampers are sometimes used to stabilize the front
wheel from shimmying at higher speeds during takeoff and
landing. [Figure 3-29] The front wheel sometimes has shock
absorbers or the tire itself can act as the shock absorber. The
front wheel typically has a disk or a drum brake, mechanical
or hydraulic. [Figures 3-30 and 3-31] A front brake is lighter
and simpler than rear brakes, but some carriage brake systems
utilize the rear brakes.
A parking brake is extremely useful for securing the aircraft
on the ground without needing chocks for securing the
aircraft before takeoff and after landing. A number of parking
brake systems are utilized by different manufacturers.
[Figure 3-32]
The main landing gear is the two rear wheels of the WSC
aircraft. Since the center of gravity (CG) is much closer to
the rear wheels, most of the weight for the aircraft is carried
on the rear wheels for taxi, takeoff, and landings.
There are a number of different confi gurations for the main
gear. A conventional confi guration has two separate systems
for each rear wheel. Each side is two structural triangles, one
Figure 3-31. Hydraulic disk brake system.
Lever holding brake on
Figure 3-32. Mechanical parking brake system.
Shock Absorber
Shock Strut
Internal Keel
Drag Strut
Main Strut
Horizontal
Triangle
Horizontal
Triangle
Vertical
Triangle
Figure 3-33. Conventional landing gear configuration.
Figure 3-34. Alternate vertical system utilizing streamlined wires
and bungee cords.
Wires used to hold main strut vertically
in place (instead of shock strut used
on conventional gear)
Drag Strut
Main Strut
Bungee Shock
Absorber System
Figure 3-35. Solid flexible main gear.
horizontal and one vertical. The horizontal triangle consists
of a drag strut from the wheel forward to the keel or forward
structure to maintain the wheel’s fore and aft position, and
the main landing gear strut. Both the main and the drag
struts can pivot about the attachment to the keel as part of
the shock system.
The vertical triangle consists of the main landing strut and the
shock strut attached to the wheel and up to the keel structure
[Figure 3-36] or other structure such as the engine mount
shown in Figure 3-33, which houses the compressed nitrogen
and oil “oleo” shock absorber.
There are a number of other main landing gear confi gurations
and shock absorbing systems such as wire bracing
with bungee cord shocks [Figure 3-34], fiberglass or
flexible (fiberglass or steel) main gears with no struts
[Figure 3-35], and any variation of these. Carriages designed
for faster speeds may have streamlined landing gear systems.
[Figures 3-36 and 3-37]
Figure 3-38. WSC aircraft with large tundra tires for soft or rough
field operations.
Figure 3-37. Solid flexible main landing gear that is streamlined.
Figure 3-39. Flying boat.
Figure 3-36. Conventional landing gear with streamlined drag
and main struts.
As discussed in the nosewheel section, the carriage can have
main landing gear brakes on both main landing gear wheels
that can be drum or disk and controlled by mechanical or
hydraulic actuation. Each manufacturer has different designs
and options.
Tires can also assist as shock absorbers for landings. Large
tundra tires add signifi cant shock absorbing capability and
are used for operations on soft fi elds, rough fi elds, and sand.
[Figure 3-38] Generally, the faster WSC aircraft used for
airport operations have narrower tires to eliminate drag.
Landing Gear for Water and Snow
Besides landing gear for land, there are landing gear systems
for water (Weight-Shift Control Sea) and snow (ski-
equipped). If ski-equipped, skis are added to the bottom of
the wheels or replace the wheels. If sea-equipped, a complete
system provides aircraft fl otation and steering using rudders
similar to a boat. The water rudders are foot controlled,
similar to WSCL steering on the ground. Two types of sea-
equipped systems are the fl ying boat and pontoon.
The fl ying boat is a solid or infl atable boat that the WSC
aircraft fi ts into, and its fuselage is secured to as well.
[Figure 3-39] This is generally used for rougher seas in the
ocean and, with the extra drag of the boat itself, this typically
uses a larger wing and is therefore a slower fl ying WSC
aircraft. The boat design is known to be more stable in rough
seas and assists in keeping less water from splashing up so
pilot and passenger stay dryer.
The pontoon system is used for calmer water, has less drag
while fl ying, and therefore can accommodate faster, smaller
wings. [Figure 3-40] Both the fl ying boat and the pontoon
system need more horsepower than land operations for two
reasons: fi rst, to provide enough thrust to accelerate to takeoff
speed with the extra drag of the boat or pontoons on the water,
Figure 3-40. Pontoon system.
and second, to provide enough extra thrust to overcome the
additional drag of the boat or pontoons in the air for fl ight.
Electrical Systems
WSC aircraft are typically equipped with a 12-volt direct
current (DC) electrical system. A basic WSC aircraft
electrical system consists of a magneto/generator, voltage
regulator, battery, master/battery switch, and associated
electrical wiring. Electrical energy stored in a battery provides
a source of electrical power for starting the engine and other
electrical loads for the WSC aircraft.
The electrical system is typically turned on or off with a
master switch. Turning the master switch to the on position
provides electrical energy from the battery to all the electrical
equipment circuits with the exception of the ignition system.
Equipment that commonly uses the electrical system energy
includes:
• Position lights
• Anticollision lights
• Instrument lights
• Radio equipment
• Navigation equipment
• Electronic instrumentation
• Electric fuel pump
• Starting motor
• Electric heating systems (gloves, socks, pants, vests,
jackets, etc.)
Fuses or circuit breakers are used in the electrical system to
protect the circuits and equipment from electrical overload.
Spare fuses of the proper amperage should be carried in the
WSC aircraft to replace defective or blown fuses. Circuit
breakers have the same function as a fuse but can be manually
reset, rather than replaced, if an overload condition occurs in
the electrical system. Placards at the fuse or circuit breaker
panel identify the circuit by name and show the amperage
limit.
An ammeter may be used to monitor the performance of
the electrical system. The ammeter shows if the magneto/
generator is producing an adequate supply of electrical power.
It also indicates whether or not the battery is receiving an
electrical charge. A voltage meter also provides electrical
information about battery voltage, an additional status of
the electrical system.
Ballistic Parachute
An additional safety system available is a ballistic parachute
system. In the case of a structural failure because of a mid-air
collision or an engine out over hostile terrain such as a forest,
the ballistic parachute provides an added safety system. The
parachute is sized so that when used, the complete aircraft
comes down under canopy. Details of ballistic parachute
system use are covered in more detail in Chapter 13,
Abnormal and Emergency Operations.
When the system is activated, a rocket shoots out, pulling the
parachute system to full line stretch, and forcing the parachute
out and away from the carriage and wing.
The preferred point of attachment for the parachute is on top
of the wing at the hang point. This allows the WSC aircraft
to descend level and land on the wheels, helping to absorb
the shock. This requires routing from the chute to the top of
the wing with “O” rings to be able to remove this routing to
easily take the wing off the carriage. Alternate attach points
where there is no routing to the top of the wing are the mast
and engine attachment points; however, this has the WSC
aircraft descending nose down when activated.
The ballistic parachute canister can be mounted in a number
of locations on the WSC, typically on the carriage pointed
sideways to avoid entanglement with the propeller. The
actuation handle is mounted in the fl ight deck for pilot use
when needed. [Figures 3-41 and 3-42]