SHORT FULL AT AT AT
AT SYSTEM
ABSOLUTE TEST TEST 5,000 25,000 200 KT
300 KT Pitot
30 to 35 0.014
0.017
15 35 3.0
4.0 Pitot
10 to 30 0.014
0.017
15 35 3.0
4.0 Differ-
0 to 10 0.014
0.017
15 35 3.0
4.0 ential
Static 10 to 30
0.014
0.017
15 35 3.0
4.0
NOTES:
(1)
Ideally, the instrumentation used in the performance of pitot and staticsystem leak checks should be as good or better than the accuracy shown above (tolerance of the 747 cockpit instruments).
(2)
To start each pitot test, adjust the pressure to twice the value of the
instrumentation tolerance above the target test speed, and then slowly _________________
lower to target test airspeed without overshoot (i.e. to 6 knots above 200 knots or 8 knots above 300 knots as shown above). This procedure takes out any possible hysteresis. Start pitot system leak check at this point.
(3)
To start each static test adjust the pressure to twice the value of the instrumentation tolerance above the target test altitude and then slowly lower to target test altitude without overshoot (i.e. to 30 feet above 5,000 feet or 70 feet above 25,000 feet as shown above). This procedure takes out any possible hysteresis. Start static system leak check from this point.
(4)
The above procedure should be adjusted to twice the tolerance of whatever instrumentation is used.
Allowable Instrumentation Tolerance for the Pitot/Static Leak Test
Figure 502
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2) Wet pitot-static probe adapters and connect pitot inlet of upper left pitot-static probe to the pitot cutoff valve through pitot system test gage and flow restrictor.
CAUTION: ENSURE THAT PROBE ADAPTER IS FLUSHED WITH WATER
_______ BEFORE ATTACHING ADAPTER TO PROBE, OR PROBE AND/OR ADAPTER MAY BE DAMAGED. A SOLUTION CONSISTING OF HALF PURE ETHYLENE GLYCOL AND HALF WATER SHOULD BE USED IN FREEZING TEMPERATURES DOWN TO -40.F. TO PREVENT PROBE MISALIGNMENT, TEST HOSES AND ADAPTERS MUST BE SUPPORTED IN SUCH A WAY AS TO ADD NO EXTRA WEIGHT ON PROBES.
3) Seal the pitot chamber drain hole with vinyl adhesive tape.
Note: The pitot chamber drain hole located on the bottom of the
____ upper left probe head about 2.25 inches aft of probe tip.
(b) Test captain's pitot system for leakage.
CAUTION: TO PREVENT INSTRUMENT/EQUIPMENT DAMAGE, KEEP RATE
_______ OF PITOT PRESSURE CHANGE BELOW 300 KNOTS PER MINUTE AND DIFFERENTIAL PRESSURE BETWEEN 0 AND 10 INCHES OF MERCURY.
1) Make sure that static system is open to ambient and that test equipment installation is complete and ready for operation.
2) Open pitot cutoff valve. Use pneumatic test unit and pitot control valve to apply pressure equivalent to 1.959 (|0.016) inch Hg or 200 knots to captain's pitot system, as indicated on captain's airspeed indicator or pitot system test gage.
3) When system has stabilized, close pitot cutoff valve.
4) After 1 minute, read and record value indicated on the aircraft airspeed indicators and the system test gage. The pressure must not have decreased more than 0.03 inch Hg or an equivalent airspeed drop of 1.5 knots.
5) Return pitot pressure to normal. 6) Remove adapter and drain seal from upper left pitot-static probe.
CAUTION: TO PREVENT PITOT-STATIC PROBE DAMAGE VISUALLY
_______
CHECK PROBE AND VERIFY THAT NO PIECES OF
COLORED TAPE REMAIN ON PROBE.
EFFECTIVITY
ALL 03.1 Page 505 Oct 25/9834-11-00
(c) Test auxiliary pitot system No. 1 for leakage.
CAUTION: TO PREVENT INSTRUMENT/EQUIPMENT DAMAGE, KEEP RATE
_______ OF PITOT PRESSURE CHANGE BELOW 300 KNOTS PER MINUTE AND DIFFERENTIAL PRESSURE BETWEEN 0 AND 10 INCHES OF MERCURY.
1) Connect test equipment as described in paragraph (2)(a), to lower left pitot-static probe.
CAUTION: ENSURE THAT PROBE ADAPTER IS FLUSHED WITH WATER
_______ BEFORE ATTACHING ADAPTER TO PROBE, OR PROBE AND/OR ADAPTER MAY BE DAMAGED. A SOLUTION CONSISTING OF HALF PURE ETHYLENE GLYCOL AND HALF WATER SHOULD BE USED IN FREEZING TEMPERATURES DOWN TO -40.F. TO PREVENT PROBE MISALIGNMENT, TEST HOSES AND ADAPTERS MUST BE SUPPORTED IN SUCH A WAY AS TO ADD NO EXTRA WEIGHT ON PROBES.
2) On AZ 201-202, 209-211; IB 405, turn on, or remove magazine from ARINC 542 type flight recorder (Ref 31-31-01).
3) On LH 082-099; AF 121, 122, 151-199; AZ 231 WITH SB 27-2343, AND AZ 281-299; SN 351-399; MD ALL; GN ALL; AT ALL; VM ALL, plus airplanes incorp SB 27-2297, open TE FLAP LOAD RELIEF circuit breaker on P12 panel.
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(39)
