CHAPTER 34
PAGE 5
PAGE DATE: 7. July 2010
MAINTENANCE MANUAL EXTRA 300LT
34-10-02 Altimeter
The altimeter is designed to measure pressure changes of the
atmosphere by means of an aneroid capsule, the pressure
changes corresponding to changes in altitude. In this
instrument the pinion shaft drives the pointer shaft of the
large pointer via gearwheels . Further gearwheels are used to
move the small pointer. The altimeter has a scale marked in
feet (ft) or meters (m). By turning the knob at the bottom left
of the instrument, the barometric pressure reading is set in
millibars and/or in.Hg.
Removal/Installation
1 Remove the instrument cover per chapter 31-10-03 (rear
altimeter only).
2 Remove the vinyl tube and the tube-to-pipe adapter if
necessary.
3 Remove the attachment bolts and clip nuts.
4 Remove the altimeter.
5 Install in reverse sequence of removal.
6 Perform an operation test.
34-10-03 Airspeed Indicator
The airspeed indicator shows the speed of the aircraft relative
to the atmosphere. The airspeed indicator measures the
difference between pitot pressure and static pressure, the
former being picked up by the pitot tube at the pitot location
of the air flow and applied to the airspeed indicator via
tubing, the latter also being picked up by the pitot tube. The
sensing element of the airspeed indicator is an open
diaphragm which senses internally the pitot pressure and
externally the static pressure, the difference between the
two increasing with increasing speed. This difference
produces distortion of the diaphragm which is translated to
the pointer via a system of levers and gearwheels.
The reading of the airspeed indicator is in knots.
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