(b)
Remove the sealant from the switch.
(c)
Loosen the nut.
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MAINTENANCE MANUAL
(d) Remove the nut, the switch, and the two washers.
TASK 30-21-05-404-006
3. Engine Cowl Overheat Switch Installation (Fig. 401)________________________________________
A. Consumable Materials
(1) A00247, Sealant - Chromate Type BMS 5-95
B. References
(1)
AIPC 26-12-00, Fig. 1
(2)
SSM 30-21-01, SSM 30-21-02, SSM 30-21-03, SSM 30-21-04
(3)
WDM 30-21-12, WDM 30-21-22, WDM 30-21-32, WDM 30-21-42
C. Access
(1)
Location Zone 451 Engine 1 - Strut Forward Fairing, Fan Cowl Support Beam 461 Engine 2 - Strut Forward Fairing, Fan Cowl Support Beam 471 Engine 3 - Strut Forward Fairing, Fan Cowl Support Beam 481 Engine 4 - Strut Forward Fairing, Fan Cowl Support Beam
(2)
Access Panel
414 Engine 1 - Right Fan Cowl Panel
424 Engine 2 - Right Fan Cowl Panel
434 Engine 3 - Right Fan Cowl Panel
444 Engine 4 - Right Fan Cowl Panel
D. Procedure
S 424-007
(1) Install the engine cowl overheat switch with the 2 washers and the nut.
(a)
Torque the nut to 60-75 pound-inches.
(b)
Install lockwire on the nut.
S 394-010
(2)
Apply sealant to make a fillet seal around the base of the switch.
S 434-011
(3)
Install the electrical connector on the switch.
(4)
Close the right fan cowl panel.
S 864-013
(5)
Close this circuit breaker on the P6, Main Power Distribution Panel for the applicable engine:
S 414-012
6J10 NACELLE ANTI-ICE 1
6J11 NACELLE ANTI-ICE 2
6J12 NACELLE ANTI-ICE 3
6J13 NACELLE ANTI-ICE 4
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747-400 MAINTENANCE MANUAL
PITOT STATIC, TOTAL AIR TEMPERATURE PROBE AND ANGLE OF ATTACK
_____________________________________________________________ SENSOR ANTI-ICE SYSTEM - DESCRIPTION AND OPERATION
__________________________________________________
1. General (Fig. 1)_______
A. Electric heaters are built into the four pitot-static probes, two total air temperature (TAT) probes, and two angle of attack (AOA) sensor vanes to prevent ice formation. The heaters operate automatically.
B. The Pitot-Static/TAT/AOA Anti-Ice System consists of dual heaters in each pitot-static probe, a heater in each TAT probe, a heater in each AOA sensor vane, and the anti-icing system relays. The heaters are powered by 115 volts ac through circuit breakers on the P6 panel. System relays are powered by 28 volts dc through circuit breakers on the P6 panel.
C. The Pitot-Static/TAT/AOA Anti-Ice System provides inputs to the EIUs for EICAS fault indication. There is a current sensing relay in line with each heater which can provide a fault signal to the EIUs. If a heater loses its 115 volts ac power source or becomes open-circuited, an advisory message will be displayed on EICAS.
D. The system is connected to the Central Maintenance Computer System (CMCS) for ground testing purposes. During a ground test, any faults that exist with the heaters will be displayed on EICAS.
2. Operation (Fig. 2)_________
A. Functional Description
(1) When the N2 tachometer for any engine is greater than 50%, the AOA sensor heaters and the pitot-static probe strut heaters energize, while the pitot-static probe head heaters energize in their low heat mode. At lift-off, the TAT probe heaters energize and the pitot-static probe head heaters switch to their high heat mode. All probe heaters are self-regulating.
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