Piper PA-34-200T Seneca II Service Manual Download

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PIPER SENECA II SERVICE MANUAL

01/01/09

X - INSTRUMENTS

2E15

10-18. PITOT-STATIC SYSTEM.

Pitot pressure for the airspeed indicator is sensed by the pitot mast mounted under the left wing. Static
pressure for the altimeter, vertical speed and airspeed indicators is sensed by two static pressure units,
one located on each side of the rear part of the fuselage.

An alternate static source control valve is located below the instrument panel to the right of the power
quadrant. If one or more of the pitot-static instruments malfunctions, these pressure systems should be
checked for leaks, dirt or water. If moisture is present, the static system can be drained by turning on the
alternate static system. The selector valve is located at the low point of the system. Another drain is
provided in the lower left front side panel to drain moisture from the pressure line running between the
pitot mast and the instrument panel. At any time an instrument, fitting, line, pitot head or static button is
disconnected, tests must be performed prior to the next flight. Refer to Advisory Circular 43.13-l, latest
revision, for the testing procedures.

10-18a. PITOT-STATIC SYSTEM TEST.

(PIR-PPS60035, Rev. N.)

This test requires a pitot/static test fixture (i.e. - Aerosonic Air Data Test Set - Model 90000-0168 or
equivalent) and calibrated air source (i.e. - airspeed simulator) and should be performed at any time an
instrument, fitting, line, pitot head, or static button is disconnected. The test should be performed prior to
the next flight.

NOTE: Ensure the lines and fittings are free of any entrapped moisture or restrictions.

Attach the test fixture to the pitot head. Align the holes in the fixture with the holes in the head.

Attach the airspeed simulator hose to the pitot (pressure) port of the fixture.

Operate the simulator to obtain a reading of 75 knots on the airplane airspeed indicator(s).

Check that the airspeed indicator needle follows in the same direction as the simulator airspeed
indicator needle.

Raise airspeed to 195 knots and wait 15 seconds to allow the airplane airspeed indicators to
stabilize.

Observe the simulator and airplane airspeed indicators for 15 seconds. If a leak is present, the
indicator needles will move toward zero.

If a leak is present, check the fixture installation, hose connections, and pitot system lines and
fittings. Repair the leak when found, then repeat steps (1) - (6), above.

Attach static test fixture to the static port and pitot test port of the aircraft. Tape over the other static
button.

9. Set the aircraft altimeter needles to read zero altitude. Operate the static simulator to cause the

aircraft altimeter needles to read 1,000 feet altitude. Momentarily open the alternate static port.
There should be a decrease in altimeter indication. If no change occurs the system is blocked and
must be repaired prior to further testing.

Piper PA-34-200T Seneca II, Service Manual

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