S21161 (Use 201314210) Cessna 172L Alternate Static Air Source Valve

Cessna 172 Alternate Static Source. S21161 (Use 201314210) Cessna 172L Alternate Static Air Source Valve Example from a Cessna 172 POH demonstrating the impact of the alternate static source has on indicated airspeed in different vent and window configurations In other words, they designed the normal pitot-static system to account for Bernoulli's Principle and keep the static readings accurate.

Is (was) the alternate static source not standard? I can't find the plumbing, bracket, placard, etc 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.

The Aircraft Pitot Static System AeroToolbox

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

Aircraft Systems Pitot Static & Vacuum Systems Cessna 172 (FREE. Your aircraft's documentation may provide information that should be followed in case the alternate static source is used. Is (was) the alternate static source not standard? I can't find the plumbing, bracket, placard, etc

PitotStatic System 60 Second Flight Training YouTube. If erroneous instrument readings are suspected due to water or ice in the pressure line going to the standard external static pressure source, the alternate static source valve should be pulled on. Check Your Cessna's Alternate Static Port A new airworthiness directive from the FAA applies to certain Cessna 172, 175, 177, 180, 182, 185, 188, 206, 207, 208, 210, 303, 336, and 337 series airplanes