4?eechcraft
Single Engine (Piston)
Section X
Safety Information
level of the ridge is in excess of 25 knots and approximately
perpendicular to the ridge, mountain wave conditions are
likely over and near the lee slopes. If the wind velocity at the
level of the ridge exceeds 50 knots, a strong mountain wave
is probable with extreme up and down drafts and severe tur-
bulence. The worst turbulence will be encountered in and
below the rotor zone, which is usually 8 to 10 miles down-
wind from the ridge. This zone is sometimes characterized
by the presence of "roll clouds" if sufficient moisture is
present; altocumulus standing lenticular clouds are also vis-
ible signs that a mountain wave exists, but their presence is
likewise dependent on moisture. Mountain wave turbulence
can, of course, occur in dry air and the absence of such
clouds should not be taken as assurance that mountain
wave turbulence will not be encountered. A mountain wave
downdraft may exceed the climb capability of your airplane.
Avoid mountain wave downdrafts.
VFR - LOW CEILINGS
If you are not instrument rated, do not attempt "VFR on Top"
or "Special VFR" flight or clearances. Being caught above a
solid cloud layer when an emergency descent is required (or
at destination) is an extremely hazardous position for the
VFR pilot. Accepting a clearance out of airport control zones
with no minimum ceiling and one-mile visibility as permitted
with "Special VFR" is a foolish practice for the VFR pilot.
Avoid areas of low ceilings and restricted visibility unless
you are instrument rated and proficient and have an instru-
ment equipped airplane. Then proceed with caution and with
planned alternates.
VFRATNIGHT
When flying VFR at night, in addition to the altitude appro-
priate for the direction of flight, pilots should maintain a safe
minimum altitude as dictated by terrain, obstacles such as
May, 1994 10-33
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