(6)
Test auxiliary No. 2 static system for leakage.
(a)
Place shutoff valve in open position.
(b)
Apply vacuum to upper right probe (preferred) or drain fitting No. 8.
(c)
Repeat steps E.(3)(c) and (d) above using test vacuum indicator and altimeter.
(7)
Test for leakage between auxiliary static system No. 1 and captain's static system.
(a)
If captain's altimeter is the electrical type, verify that CADC No. 1 circuit breaker is closed.
(b)
Connect the vacuum source to one of the static ports on the upper left or lower right (preferred) pitot-static probe aft static pressure section or to the drain fitting for auxiliary static system No. 1.
(c)
Seal all ports of captain's static system.
(d)
Apply a vacuum equivalent to 12.37 +0.10 inches of mercury (absolute pressure) (equivalent to an altitude of 22,500 +200 feet).
(e)
After the system has stabilized, maintain the vacuum for 5 minutes.
(f)
Check that the captain's altimeter does not show an increase in altitude.
(8)
Test for leakage between auxiliary static system No. 2 and first officer's static system.
(a)
If first officer's altimeter is the electrical type, verify that CADC No. 2 circuit breaker is closed.
(b)
Connect the vacuum source to one of the static ports on the upper right or lower left (preferred) pitot static probe aft static pressure section, or to the drain fitting for auxiliary static system No. 2.
(c)
Seal all ports of first officer's static system.
(d)
Apply a vacuum equivalent to 12.37 +0.10 inches of mercury (absolute pressure) (equivalent to an altitude of 22,500 +200 feet).
(e)
After the system has stabilized, maintain the vacuum for 5 minutes.
(f)
Check that the first officer's altimeter does not show an increase in altitude.
(9)
Test alternate static system for leakage.
(a)
Place shutoff valve in open position.
(b)
Apply vacuum to right flush to body mounted static ports (preferred) or drain fitting No. 5.
(c)
Repeat steps E.(3)(c) and (d) above using test vacuum indicator and altimeter.
(d)
Remove seals and adapters from captain's and first officer's static systems. Check that static source selector valve is in NORMAL position.
(e)
Repeat steps E.(7) to ensure no leakage through static source selector valve.
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F. Restore Airplane to Normal Configuration
WARNING: Failure to remove the vinyl adhesive tape from the static ports before flight may cause large errors in airspeed sensing and altitude sensing signals which may lead to loss of safe flight.
(1)
Remove all seals and adapters from all pitot static probes that were tested. Check that no deposits or roughness exists in or about static ports or pitot head apertures.
(2)
Remove flush to body mounted adapter from alternate static port and seal if system was tested.
(3)
Remove all pitot pressure chamber drain seals.
(4)
Replace all drain fitting caps.
(5)
Ensure that flight recorder (if installed) is returned to normal operating configuration.
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PITOT STATIC SYSTEM -DESCRIPTION AND OPERATION
EFFECTIVITY
GJ B-2524
1. General
A. The pitot static system consists of four combined pitot static probes; two alternate static ports; and connecting tubing to air data instruments, air data equipment, and drain trap and test fittings (Fig. 1 and 2). These instruments measure dynamic (pitot) and ambient (static) air pressures to determine airplane vertical speed, airspeed, mach number and altitude.
B. Heater circuits are provided for anti-icing of the pitot static probes (Ref Chapter 30, Pitot Static Tubes and Temperature Probe Anti-Icing System).
2. Pitot System (Fig. 2)
A. Four pitot tubes are used to sense dynamic air pressure. Two probes are mounted on each side of the fuselage below control cabin window No. 3. The captain's pitot source is from the upper left pitot static probe and the first officer's from the upper right pitot static probe. These pitot pressures are applied to the appropriate instruments and equipment as shown in Fig. 2.
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