A. Make sure the ATC transponders are not in an altitude reporting mode.
B. This subject gives two tasks for each pitot-static system. The first task is a full-range leak test. The second task is a low-range leak test. These leak tests pressurize the system or systems that are tested. For each test, you take measurements and compare them to the specifications for the system or systems.
C. The full-range leak test makes sure that the pitot-static system does not leak at an altitude of 22,500 feet and an airspeed of 300 knots. You can do a test of each pitot system separtely. You must test all static systems at the same time so that too much differential pressure does not start. During the full-range static system test, the pitot systems must also be pressurized to prevent too much differential pressure.
D. You must do the leak test after you flush the pitot-static system, after each major airframe overhaul, or when you remove a fitting. A leak test is not required when you use a quick-disconnect fitting.
E. The low-range static system leak test makes sure that the static system does not have leaks at an altitude 5,000 feet above the field elevation.
F. You can do the low-range static system leak test to quickly make sure that the static system is operational. A full-range leak test is recommended when there is a leak or the results of the low-range leak test are inconclusive or unsatisfactory.
G. You do not have to do a leak test when you connect a quick-disconnect fitting. A visual examination of the quick-disconnect for a complete seal is necessary. You must do a full-range leak test when you cannot make sure that the quick-disconnect has a complete seal.
H. These general instructions apply to the pitot-static system leak test.
(1)
The rate of the applied vacuum to a static system must be 5000 feet or less for each minute.
(2)
The release of the vacuum from a static system must be 5000 feet or less for each minute.
(3)
The rate of the applied pressure to a pitot system must be 300 knots for each minute.
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A 737-300/400/500MAINTENANCE MANUAL
NOTE: AIRPLANE CONFIGURATION IS TYPICAL.
Pitot Static System Test Connections
Figure 501
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K62942
A
737-300/400/500MAINTENANCE MANUAL
(4)
The release of pressure from a pitot system must be 300 knots or less for each minute.
(5)
Absolute pressure in the pitot system must be equal or larger than the pressure in the static system.
(6)
The differential pressure between the pitot and static systems must not be larger than 10.00 inches of mercury.
(7)
The absolute pressure applied to a static system must not be larger than ambient pressure when an instrument is connected to that static system.
(8)
The pressure in a static system must not be larger than 32.10 inches of mercury.
(9)
Do not connect or disconnect equipment or indicators when you apply pressure or a vacuum to the pitot-static system.
(10)
AIRPLANES WITH SOURCE SELECT VALVES; you must not set the source selector valve to the ALTERNATE position when you apply a vacuum to a static system.
(11)
AIRPLANES WITH SOURCE SELECT VALVES; make sure that the source selector valve stays in the NORMAL position unless the procedure tells differently.
(12)
Remove the drain fitting caps during the leak test.
CAUTION: MAKE SURE THAT YOU DO NOT APPLY ELECTRICAL POWER THE ELECTRICAL
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