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747-400
MAINTENANCE MANUAL
CAUTION: MAKE SURE THAT YOU DO NOT APPLY ELECTRICAL POWER TO THE
_______ PITOT-STATIC PROBE HEATERS. YOU CAN CAUSE DAMAGE TO THE PITOT-STATIC PROBES.
(1) Open these circuit breakers and attach DO-NOT-CLOSE tags:
(a) P6 Main Power Distribution Panel
1) 6D31 PROBE HEAT PITOT R
2) 6D32 PROBE HEAT AUX PITOT L
3) 6E01 PRIM T/E FLAP CONT AC
4) 6E02 PRIM T/E FLAP CONT DC
S 485-502
WARNING: WHEN THE STATIC PORTS ARE COVERED, MAKE SURE THAT CONDITION IS
_______ VISIBLE FROM THE GROUND. FAILURE TO OBSERVE AND REMOVE COVERINGS OVER STATIC PORTS BEFORE FLIGHT MAY CAUSE LARGE ERRORS ON AIRSPEED SENSING AND ALTITUDE SENSING SIGNALS, WHICH MAY LEAD TO LOSS OF SAFE FLIGHT.
WARNING:_______MAKE SURE THAT THE PROBE HEAT IS NOT ON. YOU CAN CAUSE INJURY TO PERSONS.
CAUTION:_______DO NOT EXTEND THE SEALS INTO THE PITOT DRAINS. YOU CAN CAUSE DAMAGE TO THE SURFACE IN THE AREA WHEN YOU REMOVE THE SEALS.
(2) Seal these locations with vinyl adhesive tape:
(a)
The forward static ports (S1) in the lower left pitot-static probe.
(b)
The aft static ports (S2) in the upper right pitot-static probe.
S 485-095
(3) Connect the pneumatic test set to the auxiliary No. 2 static system test fitting.
(a)
Connect the static (vacuum) source in the pneumatic test unit through the static control valve to the static cutoff valve.
(b)
Connect the auxiliary No. 2 quick-disconnect test fitting to static cutoff valve through the test gage and flow restrictor.
NOTE: You will find the test fitting on the right side of the
____ airplane above the pitot-static system drains at STA
400.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
(c) Open the static cutoff valve.
S 795-096
(4) Do a leak test of the auxiliary No. 2 static system (low-range).
CAUTION: MAKE SURE THAT THE PITOT LINE PRESSURE IS EQUIVALENT OR
_______ MORE THAN THE STATIC LINE PRESSURE. KEEP THE STATIC PRESSURE CHANGES LESS THAN 5000 FEET FOR EACH MINUTE. MAKE SURE THAT THE DIFFERENTIAL PRESSURE STAYS BETWEEN 0 AND 10.19 INCHES OF MERCURY. YOU CAN CAUSE DAMAGE TO THE PITOT-STATIC SYSTEM.
(a)
Apply vacuum to the auxiliary No. 2 static system equivalent to 5,000 feet of altitude above field elevation (ambient pressure minus 5.25 |0.25 in. Hg).
VACUUM.
(b)
Close the static cutoff valve to the system when the instrument shows the necessary altitude.
(c)
Stop for 5 to 6 minutes to permit the system to become stable.
(d)
Write the altitude.
(e)
Stop for 1 minute and read the altitude again.
(f)
Make sure that the altitude does not go down by more than 80 feet (0.07 in. Hg).
CAUTION:_______ HOLD THE VACUUM, AS AN ALTERNATIVE, BEHIND THE CUTOFF
VALVE DURING THE CUTOFF TIME. YOU CAN CAUSE DAMAGE TO THE
EQUIPMENT WHEN YOU OPEN THE CUTOFF VALVE WITHOUT THE
S 865-097
CAUTION: MAKE SURE THAT THE PITOT LINE PRESSURE IS EQUIVALENT OR MORE
_______ THAN THE STATIC LINE PRESSURE. KEEP THE STATIC PRESSURE CHANGES LESS THAN 5000 FEET FOR EACH MINUTE. MAKE SURE THAT THE DIFFERENTIAL PRESSURE STAYS BETWEEN 0 AND 10.19 INCHES OF MERCURY. YOU CAN CAUSE DAMAGE TO THE PITOT-STATIC SYSTEM.
(5) Open the static cutoff valve.
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