The National Oceanic and Atmospheri

The National Oceanic and Atmospheric Administration has published the following formula for converting directly from pressure in millibars to altitude in feet:[1]

(1-(millibars/1013.25)^{.190284})*145366.45

In aviation, pressure altitude is the indicated altitude when an altimeter is set to an agreed baseline pressure setting under certain circumstances where the aircraft's altimeter would be unable to give a useful readout of altitude. Examples would be landing at a very high altitude or near sea level in conditions of exceptionally high air pressure. Old altimeters were typically limited to show altitude when set between 950 mbar and 1030 mbar. "Standard" pressure, the baseline used universally, is 1013.25 hPa, equivalent to 1013.25 mbar or 29.92 inHg (inches of mercury). This setting is equivalent to the air pressure at mean sea level (MSL) in the International Standard Atmosphere (ISA). Pressure altitude is primarily used in aircraft performance calculations and in high-altitude flight (above the transition altitude). The term "QNE" refers to the indicated altitude at the landing runway threshold when 1013.25 mbar or 29.92 inHg is set in the altimeter's Kollsman window and not the setting itself, as is commonly misconceived.

Most aviation texts for PPL and CPL exams describe a process of finding pressure altitude using the following formula:

Pressure Altitude (PA) = Hgt + 1000 x (29.92 - altimeter setting)

For example if the airfield elevation is 500 feet and the altimeter setting is 29.32 inHg then

PA = 500 + 1000 x (29.92 - 29.32)

= 500 + 1000 x 0.6
= 500 + 600
= 1100 feet

Alternatively, Pressure Altitude (PA) = Hgt + 30 x (1013 - QNH)

For example if the airfield elevation is 500 feet and the QNH is 993 mbar then

PA = 500 + 30 x (1013 - 993)

= 500 + 30 x 20
= 500 + 600
= 1100 feet

Aircraft transponders report the pressure altitude; corrections for atmospheric pressure variations are applied on the ground.

The relationship between static pressure and pressure altitude is defined in terms of the properties of the International Standard Atmosphere.

Results (English) 3:

美国国家海洋和大气管理局发表了以下公式将直接从压力毫巴高度在脚：[ 1 ]

（1 -（毫巴/ 1013.25）
{ 190284 }。）* 145366.45

航空，压力高度是当高度表被设置为在某些情况下，在某些情况下，飞机的高度表将无法给出一个有用的高度的高度的一致的基准压力设定的指示高度。例子将登陆在非常高的高度或接近海平面的条件下，特别高的空气压力。老高度计通常限于显示海拔在950毫巴和1030毫巴之间。”标准”的压力，普遍使用的基线，是1013.25帕，相当于1013.25毫巴或29.92英寸（英寸汞柱）。这个设置是相当于在平均海平面气压（MSL）在国际标准大气（ISA）。压力高度主要用于飞机性能计算和高空飞行（高于过渡高度）。“一”是指显示海拔高度在降落跑道的阈值时，1013.25毫巴或29.92英寸汞柱设置在高度计的柯尔斯曼窗不设置本身，通常是错误的。

大多数PPL和CPL考试航空文本描述了使用以下公式发现压力高度的过程：

压力高度（PA）= 1000×（29.92－HGT高度计）

例如如果机场海拔500英尺的高度设置为29.32英寸，然后

PA＝1000×（500 29.92 - 29.32）

= 500 x 0.6 = 500 600 1000

= 1100英尺

或者，压力高度（PA）= 30×（1013－HGT QNH）

例如如果机场海拔500英尺，修正海压993毫巴然后

PA = 500 x 30（1013 - 993）

= 500 x 20 = 500 600 30

= 1100英尺

飞机应答机报告气压高度；大气压力的变化修改应用在地面上。

静态压力和压力高度之间的关系是指在国际标准大气的性质方面。