Instruments- Pressure Altimeter Chapter Summary

Instruments
Pressure Altimeter
Chapter

Pressure Instruments
Pitot Static Probes and ADC.
Airspeed Indicator ( ASI ).
Mach Meter.
Pressure Altimeter.
Vertical Speed Indicator ( VSI ).


 Gyroscopic Instruments
Direction Gyro Indicator ( DGI ).
Artificial Horizon ( AH ).
Turn And Slip Indicator.

 Magnetism And Compasses
Magnetism General.
Direct Reading Magnetic Compass.
Sperry Compass System.

Miscellaneous Systems
Inertial Navigation System ( INS ).
Temperature Indicators.
Flight Data Recorders ( FDR ).
Angle Of Attack Indicators.
Flight Management System And Autopilots ( FMS ).

,Pitot Static Instruments

, Pressure Altimeter Introduction
The Pressure Altimeter is basically an Aneroid Barometer.
An Aneroid Barometer is used to measure the ambient Atmospheric pressure or Static pressure.
This pressure measurement is then used to display aircraft altitude.
The Altimeter is calibrated for ISA conditions.

, Pressure Altimeter
The following is a summary of the operation of the Pressure Altimeter


 The Pressure Altimeter measures the ambient Atmospheric pressure or Static pressure.


 The Static pressure is measured by the Static port or vent and is fed into the airtight case of the instrument.


 The Pressure Altimeter has a partially evacuated capsule supported by a leaf spring inside the case.


 As the aircraft climbs the Static pressure decreases and the capsule will expand.


 This expansion is transmitted through the linkages to indicate an increase in altitude.


 As the aircraft descends the Static pressure will increase causing the capsule to contract.


 This contraction is transmitted through the linkages to indicate a decrease in altitude.


 A Bi- Metallic strip is incorporated into the suitable linkages to compensate for the expansion or contraction of the
linkages with temperature changes.