Flight Instruments; Pitot-Static System; Maintenance; Inspection And Leakage Test - Thrush Aircraft S2R–T660 Maintenance Manual

Flight instruments consist of the magnetic compass, airspeed indicator, altimeter and bank indicator. The pitot-
static system provides pitot (impact) and static (atmospheric) air pressure to the airspeed indicator and static
air pressure to the altimeter indicator.
The pitot head installed near the wing tip of the right wing lower surface provides pitot pressure. The pitot
pressure line is connected to the airspeed indicator. A static pressure line is connected to the altimeter and to the
airspeed indicator. The static pressure ports are located on both sides of the aft fuselage where they are
connected through a yoke to a tube that runs forward along the left side of the fuselage to the instruments.

MAINTENANCE

Flight instruments utilizing pitot-static pressure are highly sensitive to pressure variations. Therefore, all tubing
and line connections must be absolutely airtight to prevent erratic indications. Moisture drains for the system
are installed in the lines at two different locations; the most in-board end of tubing in wing and in the aft
fuselage just aft of the static ports. Drain the pitot-static system periodically and whenever the system operates
erratically. If after draining, and any of the pitot-static instruments are still inoperative or erratic, clear the pitot-
static vent lines of any remaining restrictions with dry, low-pressure compressed air. Disconnecting the static
line at the altimeter and applying two to four psi air pressure to the static line may purge the lines.
Disconnecting the line from the airspeed indicator and applying two to four psi pressures to the line may purge
the pitot pressure line. Cap instrument inlets before attempting to clear lines.
Be sure air pressure is directed towards the pitot head and not
toward the instruments when purging the system.

INSPECTION AND LEAKAGE TEST

The following procedure outlines inspection and testing of the static pressure system, assuming the altimeter has
been tested and inspected in accordance with current Federal Aviation Administration Regulations.
A. Ensure the static system is free from entrapped moisture and restrictions.
B. Ensure no alterations or deformations to the static lines have occurred.
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THRUSH AIRCRAFT INC - T660 TURBO THRUSH
AIRCRAFT MAINTENANCE MANUAL

FLIGHT INSTRUMENTS

PITOT-STATIC SYSTEM

** CAUTION **
Effective: 12/17/03