TM 55-1520-240-23-7
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FLIGHT INSTRUMENTS
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PITOT-STATIC SYSTEM
Description
The pitot-static system senses dynamic and static air
pressure. It supplies these pressures to the AFCS
computers and to the vertical speed indicators, and
to the altimeters and the airspeed indicators on the
pilot’s panels. The system consists of pitot tubes, static
pressure ports, and interconnecting tubing. A heater is
an integral part of the pitot tubes and uses 115 vac.
NO BREAK - WORK HARDER
Teflon tubing and flexible hoses are used to connect
the components of the pitot-static system. The flexible
hoses are installed between the tubing and the flight
instruments and the AFCS computers. Compression
sleeve fitting assemblies are used to connect tubing
together or to pitot-static system components.
NO BREAK - WORK HARDER
The pitot tube senses dynamic air pressure. The left
tube supplies pressure to the copilot’s airspeed indicator
and No. 1 AFCS computer. The right tube supplies
pressure to the pilot’s airspeed indicator and No. 2
AFCS computer.
NO BREAK - WORK HARDER
The static ports sense air pressure. This pressure is
supplied to the vertical speed altimeter and the airspeed
indicators and the AFCS computers.
NO BREAK - WORK HARDER
The airspeed indicator is a sensitive differential pressure
gage. It measures and indicates the pressure differential
between pitot (dynamic) and static air pressures. Two
airspeed indicators are installed, one in each pilot’s
instrument panel. The indicators are calibrated from 20
to 250 knots. A restrictor in the pitot port of the indicator
dampens pointer fluctuations.
NO BREAK - WORK HARDER
Two altimeters, one in each pilot’s panel, are installed.
The copilot’s altimeter is a barometric instrument. It
indicates the height of the helicopter above sea level.
The pilot’s altimeter is an AIMS instrument. In addition
to providing the barometric altitude, it provides data to
the IFF system for ground readout of helicopter altitude.
NO BREAK - WORK HARDER
The vertical speed indicator measures and displays rate
of ascent or descent in feet-per-minute. An adjustment
screw, on the front of the indicator, is used to zero the
pointer. Two indicators are installed, one in each pilot’s
instrument panel.
NO BREAK - WORK HARDER
Four yaw sensing ports are in pairs on the sides of
the lower nose compartment. Each port is heated by
a 25 watt heater. The sideslip sensing ports provide
differential air pressure to both No. 1 and No. 2 AFCS
computers.
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