On the ground at my base airport, the elevation is 400 feet, which the altimeter shows. Lets say for example that the pressure is standard at 29.92. I fly any direction and land at an airport with an elevation of 1000'. The pressure at that other airport is 29.92 as well. But – my altimeter will show 400 feet
On the ground at my base airport, the elevation is 400 feet, which the altimeter shows. Lets say for example that the pressure is standard at 29.92. I fly any direction and land at an airport with an elevation of 1000'. The pressure at that other airport is 29.92 as well. But – my altimeter will show 400 feet still since it reads off of pressure. How can this be? Can altimeters be set knowing the actual MSL altitude?
The altimeter setting is not the actual pressure, it's the value that gives you the accurate altitude on the altimeter. The only time you could be sure that the barometer reading and the altimeter setting are the same would be a sea level under standard temperature conditions (15C).
That both airports are reporting the same altimeter setting does not mean the atmospheric pressure is the same. A barometer at the higher airport would read a bit lower than one at the lower airport.
If both airports have the same current altimeter setting, when you land at that airport at 1000 feet, your altimeter will read 1000 feet. If it does not, you do not have the correct altimeter setting.
If you do not have an official altimeter setting, once on the ground you can set the altimeter so it reads the correct local elevation.
The altimeter is a barometer, you set it to a reading 29.92 inches, which is the atmospheric pressure CORRECTED TO SEA LEVEL!
Thus your altimeter will read 400 ft if that is the airfield elevation. When you arrive at the destination airfield, also showing 29.92, that is also the atmospheric pressure corrected to MSL The ACTUAL pressure there will be slightly lower, because you are 600 feet higher. The altimeter will read accordingly, ie 1000 feet
If, en-route, you have climbed up to, say, 10,000 feet, the pressure up there will be lower still, equivalent to 10,000 feet at 29.92 at sea level. again the altimeter will read accordingly.
Any time an altimeter is set to QNH that is set to mean sea level.
QFE is the setting to field elevation and the altimeter will read zero. The Kollsman window will show somewhat less than 29.92. On this setting, when you arrive at your destination the altimeter will read 600 feet, because you are 600 feet higher than you were. If the tower can give you a QFE setting and you set the altimeter to that, it will read zero when you reach the ground.
QFE is of little value, except for parachuting or low level aerobatics, when knowing how high off the ground you are is critical.
The altimeter setting is the airport pressure corrected to sea level. Most pilots set their altimeter to the field elevation before takeoff and only use the pressure window to set it in the air before landing if the flight is long enough for the pressure to change.
If the altimeter setting is 29.92 inches at departure airport and destination airport, the altimeter will show 400 feet on the ground when you depart, and will show 1,000 feet when you land at destination –
It will read 1,000 feet because that is the elevation at the airport at destination –
If you set the proper altimeter setting, the altimeter will always read the field elevation –
Wherever it is…