B. References
 (1)  34-11-01/601, Pitot-Static Probe
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MAINTENANCE MANUAL

 C. Access
 (1)  Location Zone
 115 Area Between Nose Gear Well and Fuselage, LH
 116 Area Between Nose Gear Well and Fuselage, RH
 117 Electrical and Electronics Compartment, LH

 D. Procedure
 S 865-295
 WARNING: MAKE SURE THAT YOU DO NOT APPLY ELECTRICAL POWER TO THE FLIGHT
_______ CONTROLS. FLIGHT CONTROL SURFACES CAN MOVE AUTOMATICALLY WHEN YOU PRESSURIZE THE PITOT-STATIC SYSTEM. THIS CAN CAUSE INJURIES TO PERSONS AND DAMAGE TO EQUIPMENT.
 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 the DO-NOT-CLOSE tags:
 (a)  P6 Main Power Distribution Panel
 1) 6D30 PROBE HEAT PITOT L
 2) 6D33 PROBE HEAT AUX PITOT R
 3) 6E01 PRIM T/E FLAP CONT AC
 4) 6E02 PRIM T/E FLAP CONT DC

 S 485-496
 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 upper left pitot-static probe.
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747-400 MAINTENANCE MANUAL
 (b)  The aft static ports (S2) in the lower right pitot-static probe.
 S 485-065
 (3)  Connect the pneumatic test set to the captain's 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 quick-disconnect test fitting of the captain's static system to the static cutoff valve through the static system test gage and flow restrictor.

 NOTE: You will find the test fitting on the left side of the
____ airplane above the system drains at STA 400.
 (c)  Open the static cutoff valve.
 S 795-066
 (4)  Do a test of the captain's 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 captain's static system equivalent to 5,000 feet of altitude above field elevation (ambient pressure minus
 5.25 |0.25 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 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).

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