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

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AFMAN 11-217V1 3 JANUARY 2005
Figure 15.1. Downward Vision Angle.
15.2.4.3. Downward Vision Angle (Figure 15.1). There is an area hidden by the nose
of an aircraft that cannot be seen from the cockpit. The downward vision line from
the pilot's eye projected over the nose of the aircraft forms an angle with the
horizontal vision line. This angle is called the "downward vision angle." The area
hidden from the pilot's view can then be determined from a trigonometric relationship
based on aircraft elevation and downward vision angle. An aircraft with a 14°
downward vision angle 100 feet above the surface will conceal about 400 feet
beneath its nose. Consider an approach in 1,600-foot visibility. This means your
visual segment at 100-foot elevation with a 14° downward vision will be reduced to
about 1,200 feet. Other factors, such as a nose-high pitch attitude and a slant range
visibility less than the RVR, can further reduce your visual segment.
15.2.4.4. Pilot Reaction Time. At 100-foot elevation and a 3° glide slope, an aircraft
is approximately 1,900 feet from the runway point of intercept (RPI). If your
aircraft's final approach speed is 130 knots (215 feet per second), you have about 9
seconds to bring visual cues into the crosscheck, ascertain lateral and vertical
position, determine a visual flight path, and establish appropriate corrections. More
than likely, 3 to 4 seconds will be spent integrating visual cues before making a
necessary control input. By this time, the aircraft will be 600 to 800 feet closer to the
RPI, 40 to 60 feet lower, and possibly well into the flare. Therefore, it is absolutely
essential to be prepared to use visual cues properly and with discretion during the
final stages of a low visibility approach. Prior to total reliance on visual information,
confirm that the instrument indications support the visual perspective.
15.2.4.5. Crew Procedures.
15.2.4.5.1. Copilot. A copilot can assist the pilot in a number of ways. The
copilot can fly the approach, control airspeed, be responsible for communications,
direct the checklist, perform the missed approach, establish aircraft