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

408
AFMAN 11-217V1 3 JANUARY 2005
difference between the solid climb lines from the identical, but dashed, dive lines in the
flight path scale. Any confusion or delay in initiating proper recovery inputs may make
recovery impossible.
20.3.1.1. NOTE: Unless your HUD is endorsed as a PFR, do not use it when
spatially disoriented, for recovery from an unusual attitude, or during lost wingman
situations; use the head down display anytime an immediate attitude reference is
required. Typically, head down displays are inherently easier to use in these
situations due to the larger attitude coverage, color asymmetry between the ground
and sky, and reduced interference from the outside visual scene (glare, optical
illusions, etc.). For this reason, even if your HUD is endorsed as a PFR, current Air
Force guidance requires the head down display be available to the pilot with not more
than one hands-on switch action.
20.3.2. Flight path information. Most HUD flight path information is based on an INS.
Many INSs have the capability to compute and display different types of airspeed
(calibrated, true, or ground) and heading (magnetic or ground track). Though the INS
and HUD have become increasingly more reliable, they can fail insidiously and with little
or no warning. If such a failure occurs the pilot must realize that the types of airspeed
and heading selected may change as the displays revert to a different mode of operation,
and the FPM may disappear, leaving the pilot with a fixed pitch reference at a
surprisingly different climb or dive angle. Be prepared for any such failure by constantly
cross-checking the head-down attitude reference and other performance instruments.
20.3.3. Interpretation. Remember that the HUD picture is only a small piece of the “big
picture,” so what the pilot sees on the HUD must be accurately interpreted. That is to
say, you may be on-speed with the FPM at the correct flight path angle but aiming well
short of the runway, or you may be on-speed with the FPM on the desired aim point, but
at too high a descent angle, resulting in an unacceptably high sink rate, or at too low a
descent angle resulting in a dragged-in final and short touchdown.
20.3.4. Fixation. Fixation on HUD information can cause a breakdown in a proper
instrument crosscheck and contribute to poor situational awareness. Information
displayed on the HUD can be very compelling to the pilot. The tendency for the pilot to
fixate on the HUD is increased by the display of excessive and unnecessary information
or when the HUD brightness level is not adjusted properly for the background contrast.
Minimize the tendency to fixate on the HUD by maintaining an efficient composite
crosscheck and ensuring the HUD brightness level is properly adjusted.
20.3.5. HUD Field of View. HUD symbology may also obscure objects within the HUD
field of view. When non-essential HUD information is displayed or when the HUD
brightness level is excessive, the probability of obscuration is dramatically increased.
Proper HUD settings (including elimination of non-task-essential information and
adjusting the brightness to the proper level) are imperative to prevent potential hazards to
safe flight.
20.3.6. Conventional Crosscheck. Finally, pilots should remain proficient in the
conventional instrument crosscheck for their specific aircraft. Regardless of the type
HUD you have (endorsed as a PFR or not), it is important to occasionally fly an
instrument approach or accomplish a level-off without using the HUD so you retain your