![[pitot static instruments diagram from IFH.png]] # Static Pressure - Used by the Airspeed Indicator / Altimeter / Vertical Speed Indicator # Static Port - Links instruments to the outside air pressure - Typically flush mounted on the fuselage or integrated into the electronically heated pitot tube - In locations that are proven by flight tests to be in undisturbed air (can also be paired) - Connected to the Air Data Computer and All Standby Instruments # Pitot Pressure - Also referred to as impact air pressure - Sensed through an open-end tube pointed directly into the relative wind flowing around the aircraft - Connected to the Airspeed Indicator and Air Data Computer # Sensitive Altimeter - Aneroid barometer that measures the absolute pressure of ambient air and displays it in feet / meters above a selected pressure level - Comprised of a stack of evacuated, corrugated bronze aneroid capsules - The air pressure acting on the aneroids tries to compress them - Their thickness changes as the air compresses them, which results in an accurate altitude reading ![[Library/Instrument Flying/files/Pasted image 20240121105029.png]] # Cold Weather Altimeter Errors - True altitude will be lower than indicated when temperature is lower than standard - In extremely cold conditions, it may be necessary to add a temperature correction [ICAO cold temperature error table](obsidian://open?vault=Flying&file=ratings%2FCFI-I%2Ffiles%2FPasted%20image%2020240121110131.png) - Always follow ATC assigned altitudes, and advise ATC if you're using a correction for charted IFR altitudes - Effects of temperature on altimeter readings is called "inherent altimeter error" ![[Library/Instrument Flying/files/Pasted image 20240121105707.png]] # Airspeed Indicator - A differential pressure gauge that measures the dynamic pressure of the air through which the aircraft is flying $ \text{Airspeed} = \text{Ram air pressure} - \text{Static pressure} $ ![[Library/Instrument Flying/files/Pasted image 20240121112525.png]] # Static Port Blockages - If the pitot tube remains clear $\rightarrow$ the airspeed indicator will remain functional but become inaccurate - Increases in altitude $\rightarrow$ indications lower than actual airspeed - Decreases in altitude $\rightarrow$ indicates higher than actual airspeed - Altimeter will freeze at the altitude where the blockage occurred - VSI will indicate zero # ![[Alternate Static]] # Pitot Tube Blockages - If dynamic pressure cannot enter the pitot tube but the drain port is open $\rightarrow$ airspeed will slowly drop to zero - If ram pressure hole and drain hole become obstructed $\rightarrow$ airspeed will operate like an altimeter