PITOT STATIC INSTRUMENTS, PITOT , STATIC, DYNAMIC PRESSURE, .ppt

PITOT STATIC INSTRUMENTS, PITOT , STATIC, DYNAMIC PRESSURE, .ppt

1. PITOT STATIC INSTRUMENTS

2. Altimeter
•An instrument is used to indicates the altitude of
the aircraft from sea level.

3. •The altimeter senses the normal decrease in air
pressure that accompanies an increase in
altitude.
•It translates a change in atmospheric pressure
into a change in altitude based on the idea of a
'standard' atmosphere.
•A decrease in pressure is approximately one
milibar is equivalent to an increase in height of
30 feet.

4. The facts
The graduation of Pressure Altimeter
Is done.
•According to the ICAN law assumes a mean sea
level barometric pressure of 1013.25 milibars.
•The temperature is 15ºC.
•The temperature lapse of 1.98ºC per 1000 feet
up to an altitude of 36,090 feet.
•Above that the temperature is constant at
-56.5ºC.

5. TYPES OF ALTITUDETYPES OF ALTITUDE

7. Operation.
1.As the aircraft gains height cause decreases in
atmospheric pressure.
2.Allows a spring to pull the capsule faces
further apart.
3.This movement is magnified by a system of
levers and communicated to a pointer which
moves around the dial.
4.A bimetallic bar in the transmission
compensates for variations in the temperature
characteristics of the capsule and leaf spring.

8. Simple Altimeter
•It has a single pointer.
•It indicates 10,000 feet for one complete
revolution.
•Each small graduation is 200 feet.
•The instrument is not very accurate.

9. Basic Altimeter.
INDICATOR
POINTER
HAIRSPRING
DIAPHRAGM
STATIC PRESSURE
SET KNOB
BARO
Figure 6 Basic Altimeter operation

10. Theory of operation of Basic
Altimeter.
1.A diaphragm in a sealed chamber is
connected to static pressure.
2.An expansion or contraction of capsule
will cause the rod and gear mechanism
move up and down.
3.As the coupling elements move, the
pointer will dial around the scale.
4.The hairspring loads the pointer to zero
position.

11. The barometric adjustment
Procedure
1.As the atmosphere changes with the weather.
2.The adjustment on actual atmospheric pressure must
be done.
3.The flight crew get the information from the tower at
the time of departure.
4.The baro knob is used to adjust the MB for millibars or
IN.HG for inches of mercury.
5.The adjustment is done by push in the knob and turn it.
6.The adjustment on atmospheric pressure at sea level
is 29.92 inches of mercury , which same as 1013.25
millibar.
7.The knob will return automatically to out position after
knob is released.
8.This adjustment will give correct reading of the
Altimeter.

12. Sensitive Altimeter

13. Sensitive Altimeter
1.More accurate.
2.Have three aneroid mounted together.
3.A ‘U’ bracket is used to prevent capsule collapse and
acts as temperature compensation.
4.The three pointer are geared.
5.The smallest pointer reads 10000 feet, middle pointer
read 1000 feet and big pointer reads 100 feet.
6.The scales are graduated in millibar.
7.The pressure-setting knob in front of case used to
adjust the asmospheric pressure.
8.The indicator will indicate zero after adjustment on
local atmospheric pressure (1013 millibars).

14. Servo Altimeter.
Figure 8 Typical Servo Altimeter mechanism

15. Servo Altimeter
1.It operates with electrical power.
2.A servo is employed.
3.The movement of capsules is transmitted
through the I bar and I and E inductive pick off.
4.Pressure changes on I bar cause induce an
AC output on it due to deflection of capsule.
5.The output is fed to an amplifier and it being
amplified.
6.The output will move the motor and turn the
pointer, counter and differential gear.
7.The gear move the cam to alter the I bar.
8.The process is repeated as increase or
decrease in pressure.

16. Error on Altimeter
•The Altimeter is exposed to false indication,
because of several error in it operation.
They are:
1.Barometric error.
2.Temperature error.
3.Instrument error.
4.Position error.
5.Lag error.
6.Blockage error.

17. 1.Barometric error - it is due to fail in existence
of standard pressure at sea level.
2.Temperature error – the temperature where
the Altimeter being calibrated and it location it
flies are different.
3.Instrument error – it is due to the expansion
and contraction of capsules.
4.Position error – it is cause by the disturbance
of static vent.
5.Lag error – it is due to the rapid change of the
altutude.
6.Blockage error – due to static vent become
blocked by ice or other obstruction.

18. ICAO “Q” CODE
•QFE – Baroscale is set to ambient pressure of
airfield, so that altimeter will indicate ‘0’ feet on
landing or take off.
•QNH – Baroscale is set to pressure at mean sea
level, so that altimeter will indicate height above
mean sea level.
•QNE – Barometer is set to standard sea level
pressure of 1013.25 millibar, so that the
altimeter indicate pure altitude.