Beechcraft C-12C Operator And Technical Reference Manual page 857

CAUTION
During hot weather, if fuel tanks are
completely filled, fuel expansion may
cause overflow, thereby creating a fire
hazard.
j. Before Leaving Aircraft.
care to prevent sand or dust from entering the fuel and
oil system during servicing.
release the brake immediately after installing wheel
chocks to prevent brake disc warpage.
8-64. TURBULENCE
OPERATION.
CAUTION
Due to the comparatively light wing
loading, control in severe turbulence and
thunderstorms is critical. Since turbulence
imposes heavy loads on the aircraft
structure, make all necessary changes in
aircraft attitude with the least amount of
control pressures to avoid excessive loads
on the aircraft's structure.
Thunderstorms and areas of severe turbulence
should be avoided. If such areas are to be penetrated,
it will be necessary to counter rapid changes in attitude
and accept major indicated
Penetration should be at an altitude that provides
adequate maneuvering margins as a loss or gain of
several thousand feet of altitude may be expected.
The recommended penetration speed in severe
turbulence is 170 KIAS. Pitch attitude and constant
power settings are vital to proper flight technique.
Establish recommended penetration speed and proper
attitude prior to entering turbulent air to minimize most
difficulties. False indications by the pressure
instruments, due to barometric pressure variations
within the storm, make them unreliable. Maintaining a
pre-established attitude will result in a fairly constant
airspeed. Turn cockpit and cabin lights on to minimize
the blinding effects of lightning. Do not use autopilot
altitude hold. Maintain constant power settings and
pitch attitude, regardless of airspeed or altitude
indications. Concentrate on maintaining a level
attitude by reference to the FD/Attitude Indicator.
Maintain original heading and don't make any turns
unless absolutely necessary.
Take extreme
During hot weather,
AND THUNDERSTORM
altitude variations.
8-65. ICE AND RAIN (TYPICAL).
WARNING
While in icing conditions, if there is an
unexplained 30%
needed to maintain airspeed in level flight,
a cumulative total of 2 or more inches of
ice accumulation
unexplained decrease of 15 KIAS, or an
unexplained deviation between pilot's and
copilot's airspeed indicators, the icing
environment should be exited as soon as
practicable. Ice accumulation on the pitot
tube assemblies could cause a complete
loss of airspeed indication.
a. The following conditions indicate a possible
accumulation of ice on the pitot tube assemblies and
unprotected airplane surfaces.
conditions are observed, the icing environment should
be exited as soon as practicable.
1. Total ice accumulation of 2 inches or more
on the wing surfaces. Determination of ice
thickness
summing the estimated ice thickness on
the wing prior to each pneumatic boot
deice cycle (e.g., four cycles of minimum
recommended 1/2-inch accumulation).
2. A 30% increase in torque per engine
required to maintain a desired airspeed in
level flight, not to exceed 85% torque,
when operating
holding/loiter speed.
3. A decrease in indicated airspeed of
15 knots after entering the icing condition
(not slower than 1.4 power off stall speed)
if maintaining original power setting in
level flight.
comparing pre-icing condition entry speed
to the indicated speed after a surface,
deice cycle is completed.
4. Any variations from normal indicated
airspeed between the pilot's and copilot's
airspeed indicators.
b. Typical Icing. Typical icing occurs because
of supercooled water vapor such as fog, clouds, or
rain. The most severe icing occurs on aircraft surfaces
in visible moisture or precipitation with a true outside
air temperature between –5 °C and +1 °C; however,
under some circumstances,
conditions may be encountered with temperatures
below -10 °C. The surface of the aircraft must be at a
TM 1-1510-218-10
increase of torque
on the wing,
If any of these
can be accomplished
at recommended
This can be determined by
dangerous
an
by
icing
8-31