3. Vertical Speed Indicator
A. Vertical speed or rate of climb indicators are provided for the pilots. These indicators are operated by corrected altitude rate signals from the air data computers. The rate of change of altitude is indicated by a radial pointer in thousands of feet per minute. Incorporated in the instrument is a power supply, reference voltage supply, a demodulator, amplifier and motor differential mechanism to provide readings of instantaneous vertical speed. A failure monitor will show an OFF flag in the event of electrical power loss, loss of flag power from ADC, loss of input signal and internal malfunction (Fig. 3)
4. Electric Altimeter
A. Electric altimeters are provided for the pilots. Each altimeter is an electric drum-pointer type that receives altitude information from the central air data computer. The altitude is displayed in 1000-, 100-, and 20-foot increments on drum counters and in 100-and 20-foot increments by a pointer which reads against a fixed scale. The range of the altimeter is from -1000 to 50,000 feet with altitudes below sea level displayed by the rotating pointer and a NEG flag covering the counter drums. A red warning flag will cover the counter drums in the event of a failure. The failure monitor will show the flag in the event of the following: loss of electrical power to the indicator, loss of flag power from the CADC, excessive servo null voltage, loss of input synchro signal and internal indicator malfunction. A barometric pressure setting knob is provided to adjust the pressure setting which is displayed in both millibars and inches of mercury (Fig. 4).
B. The captain's altimeter provides coarse and fine altitude synchro signals for the altitude alert system.
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34-12-01 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Feb 20/89
K84719
553 Electric Altimeter
May 20/82 Figure 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-12-01 Page 5
5. Standby Airspeed/Altimeter Indicator
A. The standby airspeed/altimeter indicator is a combination of two flight instruments which presents an integrated display of indicated airspeed and altitude. The indicator is installed on the center instrument panel (Fig. 5).
B. The standby pneumatic airspeed indicator gives indicated airspeed 60 to 450 knots. A diaphragm within the instrument case is actuated by differential pressure from the airplane pitot static system. The diaphragm expands or contracts in proportion to the difference between the pressure around it and the pressure in it. This information is transferred from the diaphragm to the drum counter through mechanical linkage. The pointer shows indicated airspeed on a drum graduated in knots.
C. The standby altimeter is a drum-pointer type having a range of -1000 to 50,000 feet. The pointer, which indicates feet in hundreds, moves once around the dial for each 1000 feet of altitude. The drums display feet in thousands and hundreds. Indicators on the face of the altimeter show barometric pressure in inches of mercury and millibars. The barometric pressure is set by rotating the knob on the front of the instrument. An instrument vibrator is provided in the altimeter to shake the instrument to prevent errors caused by mechanical linkage friction. Power to the vibrator is supplied through a circuit breaker on panel P18.
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