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PA-46-350P, MALIBU
IN FLIGHT (Cont'd)
If the ice is removed from the empennage following inflation, the "deice"
annunciator will extinguish. If less than 90% of the ice cap located over
the sensor within the right horizontal deicer has been removed, the select
deice annunciator will remain illuminated. If a fault should develop with
either the sensor or controller, the amber "ice detector fail" annunciator
will illuminate.
In the light to moderate icing conditions a smaller radius
surface accretes ice faster than a larger radius surface.
Therefore, the horizontal and vertical stabilizers will accrete
ice faster than the main wing. This phenomenon is known
as tailplane icing which can significantly reduce pitch
control of the aircraft, particularly during flap extension for
the approach and landing phases of flight.
In some cases the deice annunciator will illuminate before the main wing
has accumulated 1/4 to 1/2 inch thickness of ice. Because the select deice
light is illuminated when the ice thickness reaches 1/4 inch on the vertical
fin deicer, the main wing may only have an ice thickness of 1/8 inch or
slightly less. However, it may be prudent to inflate the deicer boots when
the deice annunciator illuminates to ensure the tailplane is properly deiced
especially prior to flap extension.
It has been shown in icing wind tunnel tests at temperatures
below -18°C (0°F), that after multiple deicer sheds, an ice
cap may form which cannot be detected by the system
sensors. Caution should be exercised when flying in icing
conditions at cold temperatures, i.e. below -10°C (+14°F).
In all cases, the most prudent course of action is to attempt to immediately
exit the icing conditions as well as to use good pilot judgement.
ISSUED: FEBRUARY 23, 1999
CAUTION:
CAUTION:
SECTION 9
SUPPLEMENT 4
REPORT: VB-1710
3 of 4, 9-33
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