The PitotStatic System How It Works Pilot Institute

Cessna 172 Alternate Static Source. Alternate Static Source — Skywagon City The AD requires operators to check the alternate static air source selector valve to assure that the alternate static air source selector valve port is not obstructed by a part number. Example from a Cessna 172 POH demonstrating the impact of the alternate static source has on indicated airspeed in different vent and window configurations

The system is standard with a heated pitot head under the left wing and two static ports on either side of the nose cowling Look at this excerpt from a Cessna 172 PoH and you'll see there's very significant differences, especially with the windows open at low speeds.

S17763, S3471 Cessna 172K Pitot Static Source Button with Plate

Your aircraft's documentation may provide information that should be followed in case the alternate static source is used. In other words, they designed the normal pitot-static system to account for Bernoulli's Principle and keep the static readings accurate. Your aircraft's documentation may provide information that should be followed in case the alternate static source is used.

2008 Cessna 172SP Steel Aviation. Your aircraft's documentation may provide information that should be followed in case the alternate static source is used. Example from a Cessna 172 POH demonstrating the impact of the alternate static source has on indicated airspeed in different vent and window configurations

2015 Cessna 182T Buy Aircrafts. The problem with the alternate static source is it will over or under-read depending on the status of windows, vents and heating The ALT STATIC AIR valve provides static pressure from inside the cabin if the external static pressure source becomes blocked