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Understanding pressure altitude and GPS altitude in aviation apps

iPad Pilot News

Airspeed and altitude differences Consider speed first. The panel in your airplane shows indicated airspeed (IAS, derived from the pitot tube on the wing), while the iPad shows groundspeed (derived from the GPS in your ADS-B receiver or iPad). Here’s a somewhat geeky dive into the details.

Altimeter 111
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Danger lurks in circling approaches

Air Facts

What specific indicated airspeed will be flown/adhered to during the circling maneuver? The rule of thumb is VSI = ½ groundspeed times 10. Is the airport have an operable FAA tower or is it an uncontrolled field environment? A well briefed “transfer of aircraft controls” is paramount. What speed on final approach?