K84830
Air Data Temperature Indicating System Schematic 5C8
34-14-0 Figure 2 (Sheet 1) Jun 20/85
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(2)
The error signal required to position the rebalance/feedback system is developed in a dc bridge. The air temperature probe forms on leg of the bridge and the rebalance potentiometer does the balancing. DC bridge balance is monitored by a solid-state chopper and when a changing resistance in the temperature probe unbalances the bridge, the chopper converts the inbalances to an error signal to drive the feedback loop. Mechanical motion in the loop then balances the dc bridge by repositioning the rebalance potentiometer to a null condition.
(3)
Positive and negative temperature indication is controlled by the mechanical position of the rebalance/feedback system. System operation is reversed by switching the polarity of the dc bridge power supply when temperature readings pass through zero.
(4)
A yellow OFF flag is held out of view by an energized solenoid controlled by a failure monitor. The failure monitor allows the flag to drop into view upon sensing an excessive null voltage in the reposition/feedback system or the loss of 26-volt ac instrument power.
5C8
Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-14-0 Page 3
EFFECTIVITY
GJ ALL EXCEPT B2509 - B2510
K85187
Total Air Temperature Indicator Schematic 5C8
34-14-0 Figure 2 (Sheet 1) Jun 20/85
Page 4
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
EFFECTIVITY
GJ B2509 - B2510
K85194
5C8 Total Air Temperature Indicator Schematic
Jun 20/85 Figure 2 (Sheet 2) 34-14-0
Page 5
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
AIR DATA TEMPERATURE INDICATING SYSTEM -ADJUSTMENT/TEST
1. Air Data Temperature Indicating System Test
A. Equipment and Materials
(1) Thermometer accurate to士 0.50C.
B. Prepare to Test Total Air Temperature System
CAUTION: THIS TEST SHOULD EITHER BE PERFORMED BEFORE CHECKING HEATERS IN TEMPERATURE PROBE OR SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE THAT TEMPERATURE PROBE HAS RETURNED TO AMBIENT TEMPERATURE.
(1)
Apply electrical power.
(2)
Place thermometer adjacent to total air temperature probe. Shield from direct sunlight and wind.
(3)
Close total air temperature circuit breaker on P6 panel.
C. Test Total Air Temperature System
NOTE: For TAT values of (-60)0C or less and 600C or greater, the indicator will show horizontal bars.
(1)
On GJ ALL EXCEPT B2509-B2510, check that total air temperature indicator reads ambient temperature of probe within 士 40C.
(2)
On GJ B2509-B2510,
(a)
Open total air temperature indicator circuit breaker. Check that OFF flag is visible.
(b)
Close total air temperature circuit breaker. Check that OFF flag is not visible and total air temperature indicator reads ambient temperature of probe within士 20C.
(3)
Apply heat to probe and check that indicator shows increasing reading.
(4)
Apply cold to temperature probe and check that indicator shows decreasing temperature.
D. Return Airplane to Normal Configuration
(1)
Restore total air temperature system to normal and open circuit breaker.
(2)
Remove electrical power if no longer required.
5C8
Jun 20/91 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 34-14-0 Page 501
TOTAL AIR TEMPERATURE PROBE - REMOVAL/INSTALLATION
1. Remove Temperature Probe
A. Check that TOTAL TEMP circuit breaker is open and attach a DO-NOT-CLOSE tag..
B. Support probe and remove six mounting screws (Fig. 401).
C. Pull probe away from airplane to obtain access to electrical connector. Remove electrical connector from probe.
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