3-18: Basic F-15C HUD symbols
• In the center of the HUD is a fixed aircraft datum “W”, which shows the position of the
aircraft’s longitudinal axis.
• The current heading scale is positioned in the upper part of the HUD. The inverted caret
along the scale indicates the aircraft’s current heading. (For example, 04 corresponds to
the value of 40 degrees).
• On the airspeed scale, which is positioned along the left side of the HUD, the indicated
aircraft airspeed is shown in indicated knots. Speeds less than 150 knots are not indicated.
The caret position on the scale indicates the aircraft’s current speed.
• On the altitude scale, along the right side of the HUD, absolute (barometrical) altitude is
shown in feet. The caret position on the scale indicates the aircraft’s current altitude.
• The aircraft’s total velocity vector (aka flight path marker) indicator is positioned in the
HUD but can move all around depending on the maneuvering of the aircraft. It indicates
the current aircraft flight direction.
• The pitch scale is positioned in the central portion of the HUD and is linked with the velocity
vector indicator. The scale is graduated for 5 degrees. Depending on the banking
direction, the scale moves either to the right or to the left, indicating the aircraft’s banking
direction and value. In fact, it backs up the bank indicator on the ADI.