A Altimeters.

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MIL-PRF-83419E

3.5.8 Case grounding. The altimeter case shall be internally grounded to pin 14. The

electrical system in the altimeter shall be DC isolated from the case.

3.5.9 Power common leads. The power common leads of the 28V DC power and the

115V 400Hz power shall be connected together. The 5V AC or DC lighting common shall not

be connected to the 28V DC and 115V 400Hz common leads.

3.5.10 Synchro input. The altimeter shall be designed to operate electrically from a

synchro signal originating in an altitude or air data computer. The computer synchro shall be a

Bendix AY100GZ-88-A1, or equivalent or an approved electrical/electronic equivalent. The air

data computer synchro shall be excited by 26V 400Hz power from the altimeter power supply

through pins 3 and 15 of the receptacle as shown on FIGURE 3. The 26V 400Hz synchro

excitation signal available from the altimeter on pin 15 shall be in phase (within 1%) with the

115V 400Hz input to pin 2. The synchro excitation shall be provided continuously when 115V

400Hz power is provided to the altimeter, regardless of the mode of operation or failure of the

altimeter. The synchros in the altitude and air data computer shall be as shown in FIGURES 6

and 7. The scale factor of the altitude and air data computer synchros or electronic

electrical/equivalents shall be 36�/1000 feet (360�/10,000 feet). Coarse altitude information

required to compute the correct altitude in the normal mode shall be by means of the integral

pressure sensor of the altimeter. Electrical zero of the altimeter shall be at zero altitude with the

barometric setting at 29.92 inches Hg or 1013 millibars, as applicable.

3.5.11 Internal vibrator. The altimeter shall not require an integral vibrator to reduce

friction to meet performance requirements.

3.5.12 Display. The display shall be as shown in FIGURES 4 and 5 for the AAU-34B/A

and AAU-34C/A Altimeters. The display shall provide a direct reading of altitude in feet by

means of a five digit electronic presentation. An electromechanical servo driven pointer shall

provide a display of altitude information as required to supplement the digital display. A four

digit display of barometric setting shall also be provided having a selectable scale to display the

setting in inches of Hg (FIGURE 4) or millibars (FIGURE 5). An electronic display (flag) to

indicate when the altimeter is operating in the standby mode shall be incorporated. The

markings and finishes for the display shall be as specified by 3.12. The display shall be

consistent with the uniformity of other panel displays and the uniformity of the integral lighting

of the cockpit at all times. Prior approval by the procuring activity is required for any variations

or changes in the display from those specified herein.

3.5.12.1 Control lever (reset). A control lever shall be provided as shown in FIGURE 1,

FIGURE 4 and FIGURE 5 to enable the pilot to select the normal (NORM) mode of operation

for display of static pressure defect corrected altitude received from a remote altitude (synchro)

transmitter. The control lever shall also enable the pilot to revert to standby operation for the

display of pressure altitude sensed by the integral pressure sensor of the altimeter. Clockwise

movement of the lever shall select the normal mode of operation and counter-clockwise

movement of the lever shall enable reversion to the standby mode.