Pressure Altitude Calculation

Pressure altitude calculations

Calculate PA for an airfield at sea level and altimeter setting of 29.32 or QNH 993mb

• PA = 0 + 1000 x (29.92 – 29.32) (altimeter setting)
• PA = 0 + 1000 x (0.6)
• PA = 0 + 600
• PA = 600ft

or

• PA = 0 + 30 x (1013 – 993) (QNH setting)
• PA = 0 + 30 x (20)
• PA = 0 + 600
• PA = 600ft

Taking the above calculation into account the aircraft at the airfield at sea level would in fact perform as if it were already at 600ft above sea level. Therefore a longer take off run would be expected before actually getting airborne or your multirotor propellers would need to spin at a higher RPM before the RPA would lift off.

How does PA affect RPAS operations? If your area of operation is currently under a high pressure then you could expect better performance and longer battery run times. The opposite would be true for low pressure conditions.