(b)
A high pressure ground cart providing air to the airplane and the applicable isolation valve opened (flight engineer's panel).
(c)
The APU operation and the applicable isolation valve opened.
(2)
Verify the application of air by observing that the duct pressure indicator on the flight engineer's panel registers approximately 40 PSI.
(3)
Verify air flow from the applicable TAT probe.
NOTE: Air should exit TAT probe at a rate of approximately two
____
cubic feet per minute.
L. Install cord with one full wrap at bottom of cavity and one full wrap at outer surface of cavity (barely covered with sealant). If gap is too small to install cord around entire periphery, install cord in gap where possible.
M. Fill cavity between probe base and airplane skin full and flush with skin (Ref 20-30-05).
N. On airplanes with clearance notch, remove protective covers from electrical connectors and flexible hose (on airplanes with aspirated probe). Connect aircraft connector and flexible hose to probe base and lock down.
EFFECTIVITY
ALL 09 Page 403 Oct 25/9734-12-02
AIR DATA PRESSURE INSTRUMENTS - DESCRIPTION AND OPERATION
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1. General (Fig. 1)
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A. The air data pressure instruments comprise a group of eleven indicators providing a visual readout of airplane speed (both vertical and horizontal) and height relative to the surrounding atmosphere plus the temperature of that atmosphere. The essential air data displayed by these instruments are determined by sampling the air external to the airplane.
B. The captain and first officer each have a servo-pneumatic altitude indicator, an indicated airspeed/mach indicator, and an instantaneous vertical velocity indicator (Fig. 1). The first officer also has an indicator for static air temperature. A total air temperature indicator and true airspeed indicator can be used by either the captain or the first officer. The captain's indicators are mounted in the captain's instrument panel, the first officer's indicators in the first officer's instrument panel, and the shared indicators in the pilots' center instrument panel. Another total air temperature indicator is installed on the flight engineer's panel.
C. Three air data instruments also act as signal conditioners, creating an additional interface with some auto flight systems and the altitude alert system. The captain's altitude indicator interfaces with the autopilot/flight director to provide a correction factor for two altitude select error signals and the first officer's altitude indicator provides corrected altitude select error signals to the altitude alert system. The captain's indicated airspeed/mach indicator interfaces with the auto throttle system to provide an airspeed select error signal.
D. All instruments require variable 0- to 5-volt 400-Hz power for scale illumination. This is provided, through transformer-dimmer controls, from the 115-volt 400-Hz essential bus. Refer to 33-11-00, Pilots' Panel Lights. All but the two vertical velocity indicators require 26 volts, 400 Hz, single phase as basic indicator power. The captain's indicators receive this from transformer No. 3 of the essential flight instrument bus. The first officer's and pilots' indicators receive this from transformer No. 6 of flight instrument bus No. 2. The flight engineer's total air temperature indicator receives power from transformer No. 6 of flight instrument bus No. 2. The 28-volt dc essential flight instrument bus powers a vibrator in the captain's altitude indicator. The 28-volt dc flight instrument bus No. 2 powers a vibrator in the first officer's altitude indicator and vibrators in both the captain's and first officer's airspeed indicators.
2. True Airspeed Indicator (Fig. 1, Sheet 2)
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A. The true airspeed indicator provides a visual indication of true airspeed as computed by the central air data computer system. True airspeed is read on a three-drum numerical counter from 150 to 650 knots in one knot increments. In case of system or indicator failure, a yellow OFF flag covers the readout counter.
B. True airspeed indicator input is a DC analog voltage from an operational amplifier provided by air data computer No. 1. For computer description and operation, refer to 34-12-00, Central Air Data Computer System.
EFFECTIVITY
ALL 19 Page 1 Jul 25/7834-13-00
(1)
The instrument transforms a computer dc analog output into a visual indication. As shown in Fig. 2, the rebalance/feedback system slaves the numerical counter to a dc analog input from air data computer No. 1 such that the counter is providing a continuously variable readout of true airspeed.
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