(a)
Connect the pitot (pressure) source in the pneumatic test unit through the pitot control valve to the pitot cutoff valve.
(b)
Connect the pitot inlet of the probe adapter to the pitot cutoff valve through the test gage and flow restrictor.
(c)
Open the pitot cutoff valve.
(4)
Do a leak test of the auxiliary No. 2 pitot system.
S 795-055
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A
747-400
MAINTENANCE MANUAL
CAUTION:_______ MAKE SURE THAT THE PITOT LINE PRESSURE IS EQUIVALENT OR
MORE THAN THE STATIC LINE PRESSURE. KEEP THE PITOT
PRESSURE CHANGE BELOW 300 KNOTS 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 pressure to the auxiliary No. 2 pitot system equivalent to 300 |5 knots of airspeed (ambient pressure plus 4.53 |0.16 in. Hg).
CAUTION: MAKE SURE THAT YOU HOLD THE PRESSURE BEHIND THE CUTOFF
_______ VALVE DURING THE CUTOFF TIME. YOU CAN CAUSE DAMAGE TO THE EQUIPMENT WHEN YOU OPEN THE CUTOFF VALVE WITHOUT THE PRESSURE.
(b)
Close the pitot cutoff valve to the auxiliary No. 2 pitot system when the instrument shows the necessary airspeed.
(c)
Stop for 5 to 6 minutes to permit the system to become stable.
(d)
Write the airspeed.
(e)
Stop for 1 minute and read the airspeed again.
(f)
Make sure that the airspeed does not go down by more than 5.0 knots (0.16 in. Hg).
S 865-056
CAUTION: MAKE SURE THAT THE PITOT LINE PRESSURE IS EQUIVALENT OR MORE
_______ THAN THE STATIC LINE PRESSURE. KEEP THE PITOT PRESSURE CHANGE BELOW 300 KNOTS 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 pitot cutoff valve.
(6)
Put the auxiliary No. 2 pitot system to ambient pressure.
S 865-270
NOTE: You must release the pressure from the cutoff valves slowly.
____
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747-400 MAINTENANCE MANUAL
S 085-057
CAUTION: MAKE SURE THAT THE PITOT-STATIC PROBE HAS NO ADDED WEIGHT FROM
_______ THE TEST HOSES. YOU CAN BEND OR TWIST THE PITOT-STATIC PROBE OUT OF TOLERANCE.
CAUTION: DO NOT DISCONNECT THE PNEUMATIC TEST SET WHEN THE PITOT-STATIC
_______ SYSTEM IS NOT AT AMBIENT PRESSURE. YOU CAN CAUSE DAMAGE TO THE EQUIPMENT.
(7)
Disconnect the pneumatic test set from the pitot-static probe adapter.
S 085-058
(8)
Remove the pitot-static probe adapter from the lower right pitot-static probe.
(a) Remove the probe adapter from the probe.
NOTE: Dry off the pitot-static probe with a soft rag when you
____ use ethylene glycol.
CAUTION: MAKE SURE THAT YOU REMOVE ALL OF THE PIECES OF TAPE FROM
_______ EACH PITOT-STATIC PROBE. THE SYSTEM WILL NOT OPERATE CORRECTLY WHEN THE TAPE IS IN ITS POSITION.
(b) Remove the vinyl adhesive tape from the drain hole of the probe pitot chamber.
S 215-059
(9)
Examine the drain hole for unwanted materials and rough locations on the inner and outer surfaces (Ref 34-11-01/601).
S 215-060
(10)
Make sure that the pitot-static probes do not show damage to the probe tip or the static ports (Ref 34-11-01/602).
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