Altitude/Vertical Velocity Indicators

The altitude/vertical velocity indicators are located on panel F6 for the commander and panel F8 for the pilot. These indicators display vertical acceleration (alt accel), vertical velocity (alt rate), barometric altitude (alt) and radar altitude (rdr alt).

The alt accel indicator, which displays altitude acceleration of the vehicle, is read at the intersection of the moving pointer and the fixed scale. The scale range is minus 13.3 to 13.3 feet per second squared, and the scaling is 6.67 feet per second squared per inch. Software limits acceleration values to plus or minus 12.75 feet per second squared.

The alt rate scale displays vehicle altitude rate, which is read at the intersection of the moving tape and the fixed lubber line. The scale range is minus 2,940 to plus 2,940 feet per second with scale changes at minus 740 feet per second and plus 740 feet per second. The negative and positive regions are color-reversed: negative numbers are white on a black background and positive numbers are black on white.

The alt scale, a moving tape read against a fixed lubber line, displays the altitude of the vehicle above the runway (barometric altitude). The scale range is minus 1,100 feet to plus 165 nautical miles (189 statute miles), with scale changes at minus 100, zero, 500 feet and plus 100,000 feet. The scale is in feet from minus 1,100 to plus 400,000 and in nautical miles from plus 40 to plus 165 (46 to 189 statute miles). Feet and nautical miles overlap from plus 40 to plus 61 nautical miles (46 to 70 statute miles).

The rdr alt scale is a moving tape read against a fixed lubber line. It displays radar altitude (corrected to wheels) during major mode 305, below 9,000 feet (normally not locked in until below 5,000 feet; prior to radar altimeter lock-on, the meter is ''parked'' at 5,000 feet). The scale ranges from zero to 9,000 feet with a scale change at 1,500 feet. Each scale on the AVVI displays an off flag in the event of indicator malfunction, invalid data received at the DDU or power failure (all flags appear).

With the air data source switch in the nav position, the alt accel, alt rate, and alt scales are navigation-derived. The rdr alt indicator is controlled by the radar altm switch on panel F6 for the commander and panel F8 for the pilot. Radar altm positioned to 1 selects radar altimeter 1; 2 selects radar altimeter 2.

The air data switch is positioned to left or right to select the right or left air data probe, respectively, after air data probe deployment at Mach 3. The alt and alt rate scales receive information from the selected air data probe. Alt accel receives navigation data. The rdr alt scale receives data from the radar alt select switch.