1) The alternate static ports are mounted flush with the airplane skin and care is taken to see that no roughness exists on the surface of the skin to disturb air flow and compromise the ambient pressure in that area. To further assure accurate ambient pressure sensing, static pressure inputs are equalized by cross-connecting the ports on each side of the airplane. At each port, pressure is sensed through small holes which open into the alternate static source tubing. Either the captain, the first officer or both may choose this alternate source of static pressure by setting their static source selector valve to the ALTERNATE position.
(f)
Auxiliary Pitot-Static Systems (Fig. 2)
1) The auxiliary pitot-static systems operate similarly to the captain's and first officer's systems and differ only in use and connection.
(g)
Trailing Cone Static Test System Provisions (if installed).
1) Provisions for a trailing cone static test system are installed in the empennage assembly. The provisions consist of a 1 inch teflon tube, capped on each end, extended from the pressure bulkhead to the aft end of the airplane.
B. Control
(1)
Each of the pitot-static subsystems is always open to the atmosphere so there is no on or off mode of operation. Should it become necessary to subject any one of the subsystems to operational conditions (Ref 34-11-00, Maintenance Practices).
(2)
A protective cover is made for use on each pitot-static probe during airplane storage and maintenance (tool number HTC-74/76-PP). It is a slip-on cover with an attached warning streamer. Cover removal or installation is performed with the aid of tool ME65B40136-1.
CAUTION: PITOT-STATIC PROBES ARE DELICATE INSTRUMENTS AND
_______ CRITICALLY ALIGNED ON THE AIRPLANE. EXTREME CARE MUST BE EXERCISED WHEN INSTALLING, REMOVING OR HANDLING. DO NOTHING THAT PLACES ADDED WEIGHT OR STRAIN ON PROBE.
EFFECTIVITY
ALL 05 Page 10 Sep 25/9434-11-00
PITOT-STATIC SYSTEM - TROUBLE SHOOTING
______________________________________
1. General
_______
A. The following trouble shooting procedures are presented in tree-type format. The test steps (heavy-line boxes) are connected by shaded arrows to show the OK condition path. When all steps in the OK condition path check out, the system is operable.
B. When a test step does not check out, follow the NOT OK line to the box containing the trouble symptom. Turn to the procedure indicated and continue to follow a single line by analyzing the results of each test step until the required corrective action is determined. Perform the specified corrective action; then repeat the step at which the failure was encountered.
C. If no failure can be isolated in pitot-static system being checked, turn trouble shooting efforts to those instruments and/or equipment using the pitot-static input where test gages give good readings. Refer to applicable chapters for those individual trouble shooting procedures.
D. In isolating a leak, first disconnect each instrument or piece of equipment associated with system one at a time, checking for leakage after each disconnection. Should leak disappear, trouble shoot last item disconnected per the applicable chapter and section.
E. Should trouble shooting tree lead to component replacement with no further instructions and trouble is not eliminated, the problem may lie in connections. A visual inspection may help determine this possibility.
2. Prepare for Trouble Shooting
____________________________
A. Leakage check requires a pneumatic test unit, adapters and gages (Ref 34-11-00, Adjustment/Test).
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本文鏈接地址：747飛機維護手冊AMM CHAPTER 34 - NAVIGATION 第34章導航1(23)
