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In non-pressurized airplanes, most alternate static
sources are plumbed to the cabin. On pressurized airplanes,
they are usually plumbed to a non-pressurized
baggage compartment. The pilot must activate the
alternate static source by opening a valve or a fitting in
the cockpit. Upon activation, the airspeed indicator,
altimeter, and the vertical speed indicator (VSI) will be
affected and will read somewhat in error. A correction
table is frequently provided in the AFM/POH.
Anti-icing/deicing equipment only eliminates ice from
the protected surfaces. Significant ice accumulations
may form on unprotected areas, even with proper use
of anti-ice and deice systems. Flight at high angles of
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12-8
attack or even normal climb speeds will permit significant
ice accumulations on lower wing surfaces, which
are unprotected. Many AFM/POHs mandate minimum
speeds to be maintained in icing conditions. Degradation
of all flight characteristics and large performance losses
can be expected with ice accumulations. Pilots should
not rely upon the stall warning devices for adequate stall
warning with ice accumulations.
Ice will accumulate unevenly on the airplane. It will
add weight and drag (primarily drag), and decrease
thrust and lift. Even wing shape affects ice accumulation;
thin airfoil sections are more prone to ice
accumulation than thick, highly-cambered sections.
For this reason certain surfaces, such as the horizontal
stabilizer, are more prone to icing than the wing. With
ice accumulations, landing approaches should be made
with a minimum wing flap setting (flap extension
increases the angle of attack of the horizontal stabilizer)
and with an added margin of airspeed. Sudden and large
configuration and airspeed changes should be avoided.
Unless otherwise recommended in the AFM/POH, the
autopilot should not be used in icing conditions.
Continuous use of the autopilot will mask trim and
handling changes that will occur with ice accumulation.
Without this control feedback, the pilot may not
be aware of ice accumulation building to hazardous
levels. The autopilot will suddenly disconnect when it
reaches design limits and the pilot may find the airplane
has assumed unsatisfactory handling characteristics.
The installation of anti-ice/deice equipment on airplanes
without AFM/POH approval for flight into icing
conditions is to facilitate escape when such conditions
are inadvertently encountered. Even with AFM/POH
approval, the prudent pilot will avoid icing conditions
to the maximum extent practicable, and avoid extended
flight in any icing conditions. No multiengine airplane
is approved for flight into severe icing conditions, and
none are intended for indefinite flight in continuous
icing conditions.
PERFORMANCE AND LIMITATIONS
Discussion of performance and limitations requires the
definition of several terms.
• Accelerate-stop distance is the runway length
required to accelerate to a specified speed (either
VR or VLOF, as specified by the manufacturer),
experience an engine failure, and bring the airplane
to a complete stop.
• Accelerate-go distance is the horizontal distance
required to continue the takeoff and climb
to 50 feet, assuming an engine failure at VR or
VLOF, as specified by the manufacturer.
• Climb gradient is a slope most frequently
expressed in terms of altitude gain per 100 feet
of horizontal distance, whereupon it is stated as
a percentage. A 1.5 percent climb gradient is an
altitude gain of one and one-half feet per 100 feet
of horizontal travel. Climb gradient may also be
expressed as a function of altitude gain per nautical
mile, or as a ratio of the horizontal distance
to the vertical distance (50:1, for example).
Unlike rate of climb, climb gradient is affected
by wind. Climb gradient is improved with a
headwind component, and reduced with a tailwind
component. [Figure 12-5]
• The all-engine service ceiling of multiengine
airplanes is the highest altitude at which the airplane
can maintain a steady rate of climb of 100
f.p.m. with both engines operating. The airplane
has reached its absolute ceiling when climb is
no longer possible.
• The single-engine service ceiling is reached
when the multiengine airplane can no longer
maintain a 50 f.p.m. rate of climb with one engine
inoperative, and its single-engine absolute ceiling
when climb is no longer possible.
The takeoff in a multiengine airplane should be
planned in sufficient detail so that the appropriate
　
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