Honeywell Primus 880, Руководство пилота

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PRIMUS
r
880 Digital Weather Radar System
A28- 1146- 102- 00
Federal Aviation Administration (FAA) Advisory Circulars
A- 12
TURBULENCE IN RELATION TO DISTANCE FROM THE STORM
EDGE
THE CLEAR AIR ON THE INFLOW SIDE OF A STORM IS A PLACE
WHERE SEVERE TURBULENCE OCCURS. At the edge of a cloud, the
mixing of cloudy and clear air often produces strong temperature gradients
associated with rapid variation of vertical velocity. Tornado activity is found
in a wide range of spacial relationships to the strong echoes with which
they are commonly associated, but many of the most intense and enduring
tornadoes occur on the south to west edges of severe storms. The
tornado itself is often associated with only a weak echo. Echo hooks and
appendages are useful qualitative indicators of tornado occurrence but are
by no means infallible guides. Severe turbulence should be anticipated up
to 20 miles from the radar edge of severe storms; these often have a
well- defined radar echo boundary. The distance decreases to
approximately 10 miles with weaker storms which may sometimes have
indefinite radar echo boundaries. THEREFORE, AIRBORNE RADAR IS
A PARTICULARLY USEFUL AID FOR PILOTS IN MAINTAINING A
SAFE DISTANCE FROM SEVERE STORMS.
TURBULENCE ABOVE STORM TOPS
Flight data shows a relationship between turbulence above storm tops
and the airspeed of upper tropospheric winds. WHEN THE WINDS AT
STORM TOP EXCEED 100 KNOTS, THERE ARE TIMES WHEN
SIGNIFICANT TURBULENCE MAY BE EXPERIENCED AS MUCH
AS 10,000 FEET ABOVE THE CLOUD TOPS. THIS VALUE MAY BE
DECREASED 1,000 FEET FOR EACH 10- KNOT REDUCTION OF
WIND SPEED. This is especially important for clouds whose height
exceeds the height of the tropopause. It should be noted that flight
above severe thunderstorms is an academic consideration for today’s
civil aircraft in most cases, since these storms usually extend up to
40,000 feet and above.
TURBULENCE BELOW CLOUD BASE
While there is little evidence that maximum turbulence exists at middle
heights in storms (FL 200- 300), turbulence beneath a storm is not to
be minimized. This is especially true when the relative humidity is low
in any air layer between the surface and 15,000 feet. Then the lower
altitudes may be characterized by strong outflowing winds and severe
turbulence where thunderstorms are present. Therefore, THE SAME
TURBULENCE CONSIDERATIONS WHICH APPLY TO FLIGHT AT
HIGH ALTITUDES NEAR STORMS APPLY TO LOW LEVELS AS
WELL.