1,669
edits
Altitude: Difference between revisions
Jump to navigation
Jump to search
m
no edit summary
m (→True altitude) |
mNo edit summary |
||
| Line 26: | Line 26: | ||
==Pressure altitude== | ==Pressure altitude== | ||
*Altitude in terms of the air pressure. | *Altitude in terms of the air pressure. | ||
The altimeter will display the barometric pressure expressed in feet. (i.e. your expensive piece of equipment has been reduced to a barometer) | The [[altimeter]] will display the barometric pressure expressed in feet. (i.e. your expensive piece of equipment has been reduced to a barometer) | ||
*Pressure altitude gives the same result for every aircraft independent from the departing airfield of the aircraft. | *Pressure altitude gives the same result for every aircraft independent from the departing airfield of the aircraft. | ||
*Pressure altitude will change with the weather but this is true for all aircraft sharing the same area. | *Pressure altitude will change with the weather but this is true for all aircraft sharing the same area. | ||
| Line 32: | Line 32: | ||
*Never use Pressure altitude during approach since the altimeter does not display the altitude. | *Never use Pressure altitude during approach since the altimeter does not display the altitude. | ||
===Flight level=== | ===Flight level=== | ||
*[[#Pressure altitude]] divided by 100 is referred to as the flight level, and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions). When the altimeter reads 18,000 ft on the standard pressure setting the aircraft is said to be at "Flight level 180" or FL180. | *[[#Pressure altitude]] divided by 100 is referred to as the flight level, and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions). When the [[altimeter]] reads 18,000 ft on the standard pressure setting the aircraft is said to be at "Flight level 180" or FL180. | ||
==Density altitude== | ==Density altitude== | ||
| Line 43: | Line 43: | ||
*The code [http://en.wikipedia.org/wiki/QNH '''QNH'''] is how a pilot would request the "atmospheric pressure at sea-level". In reply [[ATC]] will repeat QNH followed with the pressure. These days QNH is also transmitted automatically on [[ATIS]]. | *The code [http://en.wikipedia.org/wiki/QNH '''QNH'''] is how a pilot would request the "atmospheric pressure at sea-level". In reply [[ATC]] will repeat QNH followed with the pressure. These days QNH is also transmitted automatically on [[ATIS]]. | ||
To use a barometer as a tool to measure the altitude, the altimeter, means it must be corrected for weather influences. For that the airfield has an accurate barometer and they know the height of the airfield above [[Mean Sea Level]]. From those two they will calculate the barometric pressure at [[Mean Sea Level]], the QNH. It will transmit the QNH and with that the altimeter in the aircraft can be corrected for weather influences and will display the [[#True height]]. This way the [[#Indicated altitude]] will be accurate for a certain area around the airfield as long as the weather remains stable. | To use a barometer as a tool to measure the altitude, the [[altimeter]], means it must be corrected for weather influences. For that the airfield has an accurate barometer and they know the height of the airfield above [[Mean Sea Level]]. From those two they will calculate the barometric pressure at [[Mean Sea Level]], the QNH. It will transmit the QNH and with that the altimeter in the aircraft can be corrected for weather influences and will display the [[#True height]]. This way the [[#Indicated altitude]] will be accurate for a certain area around the airfield as long as the weather remains stable. | ||
QNH is a vital tool to use a height map of an area, hence it is vital during approach of an airfield. | QNH is a vital tool to use a height map of an area, hence it is vital during approach of an airfield. | ||