The next option on the ALTI button is BARO. This will indicate your local
barometric pressure which will usually differ from barometric pressure
in weather reports which are referenced to sea level. Increasing altitude
will cause a decrease in pressure by approx 1mB per 30 feet above sea
level, decreasing at higher altitudes.
This is followed by PRESSURE CHANGE which records how local air
pressure changes over time and can give an indication of a potential
trend in the weather, for example when a low pressure system is
approaching. Allow an hour or so for the trend indicator to register any
change or leave it on overnight before you fly.
In PRESSURE CHANGE mode the segmented scale indicates in quarter
millibar increments. Current pressure is indicated by a flashing segment
while other segments will have registered previous pressure excursions.
This can be reset to the current pressure with a long press on the ALTI
button.
This function will be affected if you fly or change altitude and is only
provided as a guide if you are deciding whether to fly.
