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What does an altimeter do?
An altimeter is a device that measures altitude—a location’s distance above sea level. Most altimeters are barometric, meaning they measure altitude by calculating the location’s air pressure. Air pressure decreases as altitude increases.
How does a pressure altimeter work?
The altimeter measures the height of an aircraft above a fixed level. The instrument senses this by taking the ambient air pressure from the static port. Inside the altimeter is a sealed disc called an aneroid, or bellows. As the aircraft goes up, the pressure inside the case decreases and the bellows expand.
What are the procedures for setting the barometric altimeter?
The aircraft cruising altitude or flight level is maintained by referencing the barometric altimeter. Procedures for setting altimeters during high and low barometric pressure events must be set using the following procedures: Below 18,000 feet mean sea level (MSL). Barometric pressure is 31.00 “Hg or less.
What happens if the altimeter is not set to the current setting?
If the altimeter is not set to the current altimeter setting when flying from an area of high pressure into an area of low pressure, the aircraft will be closer to the surface than the altimeter indicates. An inch Hg. error in the altimeter setting equals 1,000 feet of altitude. For example, setting 29.90 “Hg instead of 30.90 “Hg.
When to add or subtract altitude from altimeter?
If the given altimeter setting is less than 29.92, then you ADD to your altitude If the given altimeter setting is greater than 29.92, then you SUBTRACT from your altitude The pressure altitude corrected for temperature variations This is most important to takeoff and climb performance of an aircraft
What happens when you leave the altimeter in the Kollsman window?
When you leave the number in the Kollsman window the same (let’s say you have it set to 29.92 to see the pressure altitude) and the atmospheric conditions change so that the correct altimeter setting increases–i.e. the air pressure has increased– then the reading on your altimeter decreases.