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positive stability raises the nose to normal fl ight, as
described in Figure 2-25C.
Phase 2—If the rotational movement is enough to
produce a vertical dive, as illustrated in Figure 2-29,
the aerodynamic dive recovery might raise the nose
to an attitude to recover from the dive and resume
normal fl ight condition.
Phase 3—The rotational momentum is enough to bring
the nose signifi cantly past vertical (the nose has tucked
under vertical), but could still recover to a vertical dive
and eventually resume a normal fl ight condition.
Phase 4—The rotational momentum is severe enough
to continue rotation, bringing the WSC wing into a
tumble from which there is no recovery to normal
fl ight, and structural damage is probable.
Avoidance and emergency procedures are covered in Chapter
6, Basic Flight Maneuverers, and Chapter 13, Abnormal and
Emergency Procedures.
Weight, Load, and Speed
Similar to airplanes, sailplanes, and PPCs, increasing weight
creates increases in speed and descent rate. However, the
WSC aircraft has a unique characteristic. Adding weight to
a WSC aircraft creates more twist in the wing because the
outboard leading edges fl ex more. With less lift at the tips, a
nose-up effect is created and the trim speed lowers.
Therefore, adding weight can increase speed similar to other
aircraft, but reduce the trim speed because of the increased
twist unique to the WSC aircraft. Each manufacturer’s
make/model has different effects depending on the specifi c
design. As described in the Pilot’s Handbook of Aeronautical
Knowledge, the stall speed increases as the weight or loading
increases so some manufacturers may have specifi c carriage/
wing hang point locations for different weights. Some require
CG locations to be forward for greater weights so the trim
speed is well above the stall speed for the wing.
WSC aircraft have the same forces as airplanes during normal
coordinated turns. Greater bank angles result in greater
resultant loads. The fl ight operating strength of an aircraft
is presented on a graph whose horizontal scale is based on
load factor. The diagram is called a VG diagram—velocity
versus “G” loads or load factor. Each aircraft has its own VG
diagram which is valid at a certain weight and altitude. See
the Pilot’s Handbook of Aeronautical Knowledge for more
details on the VG diagram. Load factors are also similar to
the VG diagram applicable to WSC.
Basic Propeller Principles
The WSC aircraft propeller principles are similar to those
found in the Pilot’s Handbook of Aeronautical Knowledge,
except there is no “corkscrewing effect of the slipstream”
and there is less P-factor because the carriage is generally
fl ying with the thrust line parallel to the relative wind. The
wing acts independently, raising and lowering the AOA and
speed. This was introduced at the beginning of this chapter
when angle of incidence was defi ned.
The torque reaction does have a noticeable effect on the WSC
aircraft. With the typical left hand turn tendency (for right
hand turning propellers), turns are not typically built into the
wing. As in airplanes, some cart designs point the engine
down and to the right. Others do not make any adjustment, and
the pilot accounts for the turning effect through pilot input.
It should be noted that many of the two-stroke propellers turn
to the right, as do conventional airplanes. However, many
four-stroke engine propellers turn to the left, creating a right
hand turn. Consult the POH for the torque characteristics of
your specifi c aircraft.
Chapter Summary
Basic principles of aerodynamics apply to all aircraft;
however, the unique design of the wing and the separate
fuselage/carriage provide a simplistic and effi cient aircraft.
The following provide a summary of the unique aerodynamics
for the WSC wing:
• The WSC wing is pitch stable without a tail because
of the combination of airfoil design from root to tip,
sweep, twist, and planform.
• WSC wing fl exibility allows the wing to twist from
side to side by shifting the weight providing the control
to roll the aircraft without control surfaces.
• The WSC wing only has two axes of control, pitch
and roll, while no yaw control is needed because it is
yaw stable.
• The WSC wing is stall resistant because under normal
fl ight conditions the tip chord is still fl ying while the
rest of the wing is stalled—similar to the airplane
canard system.
3-1
Introduction
Weight-shift control (WSC) aircraft come in an array of shapes
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Weight-Shift Control Aircraft Flying Handbook(27)
