BASIC INSTRUMENT PROCEDURES
AAU-19/A SERVO Altimeter (2F101 Simulator). The AAU-19/A counter-drum-
pointer servo altimeter (Figure 1-1) consists of a pressure altimeter combined with an
AC powered servomechanism. The altimeter has a primary (servo) mode and a
standby (pressure mode) of operation, controlled by a spring-loaded self-centering
mode switch placarded RESET and STBY. In the primary (servo) mode, the
altimeter displays altitude, corrected for position error, from the synchro output of the
altitude computer. In the standby mode of operation, the altimeter displays altitude
directly from the static system (uncorrected for position error) and operates as a
standard pressure altimeter. A DC powered internal vibrator is automatically
energized while in the standby mode to minimize friction in the display mechanism.
AAU-34B/A Solid-State Barometric Altimeter (T-2C Aircraft). All VT-86 T-2C
aircraft are equipped with the AAU-34B/A Solid-State Barometric Altimeter (Figure
1-1). This altimeter is functionally similar to the AAU-19/A, but incorporates a direct
digital reading of altitude by means of a liquid crystal display.
The servo-driven pointer used by the AAU-19/A altimeter has been retained to
provide analog rate information and redundant altitude information between 100-foot
levels. The AAU-34B/A incorporates a vibrating cylinder system similar to that in
the AAU-19/A to minimize friction in the analog display system. The baroset knob
of the AAU-34B/A is used to insert barometric pressure and is used to select between
inches of Hg and millibars. The altimeter has a primary and a standby (pressure)
mode similar to the AAU-19/A. The primary mode of operation is the NORMAL
mode analogous to the RESET mode of the AAU-19/A. The standby mode of
operation uses a solid-state pressure sensor to provide altitude information. The
AAU-34B/A altimeter uses LCD readout rather than a mechanical counter. There is
no altimeter lag inherent in aircraft equipped with this system. Operation of the
AAU-34B/A is functionally identical to the AAU-19/A with the exception that the
primary mode of operation is labeled NORMAL instead of RESET.
The AAU-34B/A requires 115-Vac power. In the event of a
complete electrical failure, the altimeter will not display digital
altitude information, and the servo-driven pointer will freeze.
BASIC INSTRUMENT PROCEDURES 1-9