SEMS and ATMOSPHERIC PRESSURE

According to the two new physical laws, Aeroelasticity can be defined as "the study of the action of air over the bodies (or structures) and the elastic effect that produces upon them, be at rest or in motion." Said elastic effect depends on the force of air, which is directly proportional to the atmospheric pressure; where said pressure as well as its density varies with the altitude.

Two fundamental measures in air navigation are the speed and altitude. Both displacements are obtained directly from the measurement of the atmospheric pressure (Pa) by barometers or aneroid instruments, which base their measures in the elastic effect of the atmospheric pressure on the capsules or aneroid valves, also known as wafers or diaphragms according the following figures.

ALTIMETER SPEED INDICATOR

Images: Federal Aviation Administration

ALTIMETER

Fig. 1 Fig. 2

Wafer

Connection for Static Atmospheric Pressure

-Pa

-Pa

Atmospheric pressure in flight

+Pa

+PaAtmospheric pressure on runway or sea level

SPEED INDICATOR

Static connection

Pitot TubeWafer

Airflow

Fig. 3

SIMPLIFIED DRAWINGS ABOUT THE PHYSICAL BASIS OF ANEROID METERS IN AIRCRAFTS:ALTIMETERS AND SPEED INDICATORS.

In the case of the altimeter, the altitude of the aircraft is obtained by the direct measure of the atmospheric pressure by conversion of the wafer’s elastic deformation; while in the case of the speed measurement, this is obtained by the relationship between the atmospheric pressure and the aerodynamic pressure or dynamic pressure of the air through the Pitot tube.

In the same way that for every load and given speed there is a unique flight elastic envelope (EE), also there will be a unique flight elastic envelope for the altitude, according to said given load and speed.

By interrelation of measures or taking the wafer’s elasticity of each indicator as reference measure, we could make the whole aircraft in an indicator of the speed and altitude with an accuracy as exact as safe, according with an integrated system made by SEMS sensors and WAFER sensors, as the distribution example in Fig. 4. In this way we get a safety redundancy directly proportional to the number of sensors or indicators used.

ELASTICITY’S INTEGRATED SENSORS SYSTEMS

WHOLE AIRPLANE ELASTICITY SENSORS NETWORK

Fig. 4

= Elasticity’s Integrated Sensors Systems (SEMS sensors and WAFER sensors)

Miguel Cabral Martín