BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

AFMAN 11-217V1 3 JANUARY 2005 339
of action and act without hesitation to prevent the development of an unsafe
situation.
15.2.4.1.7. Snow. Blowing snow is accompanied by many of the same hazards as
rain, such as turbulence, difficulties in reading the flight instruments, obscured
visual cues, and aircraft control problems. Of special interest will be a lack of
visual cues for runway identification for the visual portion of the approach. The
approach and runway lights will provide some identification; however, runway
markings and the contrast with relation to its surroundings may be lost in the
whiteness. Therefore, depth perception may be difficult, requiring more emphasis
on instruments for attitude control. It is extremely important to avoid large
attitude changes during approaches in snow.
15.2.4.2. Visual Cues.
15.2.4.2.1. Runway Contact Point. Approach lights, runway markings, lights,
and contrasts are the primary sources of visual cues. At some facilities,
touchdown zone and centerline lights may also be available. Become familiar
with the lighting and marking patterns at your destination and correlate them with
the weather so you will be prepared to transition to visual flight. In minimum
visibility conditions, the visual cues and references for flare and runway
alignment are extremely limited compared to the normal references used during a
visual approach. Therefore, the aircraft's projected runway contact point may not
be within your visual segment until considerably below published minimums.
15.2.4.2.1.1. WARNING: Any abrupt attitude changes to attempt to bring the
projected touchdown point into your visual segment may produce high sink
rates and thrust or lift problems at a critical time. Those so-called duck-under
maneuvers must be avoided during the low visibility approach.
15.2.4.2.2. Duck-under. Another potential duck-under situation occurs when you
attempt to land within the first 500 to 1,000 feet of the runway after breaking out
of an overcast condition. In this case, you may attempt to establish a visual
profile similar to the one you use most often. Establishing the visual profile
usually involves reducing power and changing attitude to aim the aircraft at some
spot short of the end of the runway. In this maneuver you may attempt to use as
much of the available runway as possible because of a short runway or due to
poor braking conditions. The duck-under is not recommended since high sink
rates and poor thrust/lift relationships can develop which may cause undershoots
or hard landings. Base your landing decision upon the normal touchdown point
from the instrument approach, and if stopping distances are insufficient, proceed
to an alternate.