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the ocean where there was typically an inverted midday sea
breeze with little to no convective turbulence (thermals). This
developed confi dence for fl ying in winds up to 15 knots but
no experience was gained in thermals. In fact, the pilot was
not aware that strong thermals could be hazardous.
Now, with a new license, the pilot visits his parents in the
middle of the high desert of Colorado. Unfamiliar with
the local conditions, the new pilot gets a weather report
of winds to 15 knots, something the pilot has experienced
before. By the time the pilot arrives at the airport, discusses
the situation with the airport offi cials, and sets up the WSC
aircraft, it is 2:00 in the afternoon. The wind is generally calm
but increasing to 15 knots occasionally. There are towering
6-25
Phase 4 Phase 3 Phase 2 Phase 1 Whip Stall
Wing completely
stalled and very
high pitch angle
Any nose down
rotation—pilot pushes
control bar full
forward and applies
full throttle
Vertical dive—
pilot continues
to hold control
bar full forward
and full throttle
Nose rotates down
Nose is tucked under—
pilot continues to hold
control bar full forward
and full throttle
Tumble—with complete
loss of control of aircraft, it
will most likely have
structural failure.
Use ballistic parachute
system (if so equipped).
Figure 6-23. Whip stall/tuck/tumble sequence.
cumulus clouds in the sky surrounding the current airport
similar to clouds that the pilot had seen far inland from where
he or she took instruction and soloed.
The pilot takes off in relatively calm winds, but it is unusually
bumpy air. Without any experience in the high desert or with
thermal conditions, the pilot has misjudged the conditions and
is fl ying in strong thermal convection. The new pilot climbs
out trying to get above the turbulence, which usually works
near the beach because of the mechanical turbulence near the
ground. However, the turbulence increases.
As the pilot is climbing to a pattern altitude of 1,000 feet
AGL at full throttle, the aircraft is pitched nose up while the
pilot lets the force of the updraft raise the nose. Never has
the pilot felt the nose rise with this type of force before. The
pilot is shocked and disoriented at this high pitch attitude,
but eventually lets up on the throttle. But now at an unusually
high pitch angle, the WSC nose fl ies into the downdraft of
the thermal. At the same time, the updraft is still pushing up
on the tips of the wing while the downdraft is pushing down
on the nose creating a forward rotation with a weightless
sensation. Before the pilot knows it, the wing is rotating
pitch down for a vertical dive. [Phase 1 in Figure 6-23] The
student remembers from training that “in a nose down rotation
into a steep dive the control bar is pushed full forward and
full throttle applied” and initiates this corrective action. The
pilot reaches the vertical dive, but because of the corrective
action the WSC aircraft recovers from the dive and proceeds
back to land safely.
What went wrong? What were the errors? How could this
near catastrophe have been avoided?
• In a new area and unfamiliar with the conditions, the
new pilot should have asked the local instructor or
other pilots about the conditions for the day. Local
WSC pilots are a great resource for fl ying the local
conditions, but pilots of any category aircraft are
knowledgeable of the conditions and could have
provided advice for the new pilot. This might have
prevented the new pilot from attempting this fl ight.
• Flying in a new environment and not understanding
the power of midday thermals in the high desert should
have forced the new pilot to scrap this midday fl ight.
The pilot should have started fl ying in the morning
when there is little thermal convection and gained
experience and understanding about the weather in
this new area.
6-26
• Better preflight planning should have been
accomplished, especially in a new location. The pilot
should have known to obtain convective information
and realize it was going to be too bumpy for his or
her limited experience. The pilot was accustomed
to seeing towering cumulus clouds where he or she
trained, but they were way inland and not in the normal
fl ying area. Here clouds were observed all around.
• Site observations indicated strong thermal activity.
Observation of winds picking up to 15 knots and then
becoming calm normally indicates thermal activity.
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Weight-Shift Control Aircraft Flying Handbook(84)
