Pressure altitude




Pressure altitude within the atmosphere is the altitude in the International Standard Atmosphere (ISA) with the same atmospheric pressure as that of the part of the atmosphere in question.


The National Oceanic and Atmospheric Administration (NOAA) has published the following formula[1] for directly converting atmospheric pressure in millibars (mb{displaystyle mathrm {mb} }{displaystyle mathrm {mb} }) to pressure altitude in feet (ft{displaystyle mathrm {ft} }{displaystyle mathrm {ft} }):


145366.45[1−(Station pressure in millibars1013.25)0.190284].{displaystyle 145366.45left[1-left({frac {text{Station pressure in millibars}}{1013.25}}right)^{0.190284}right].}{displaystyle 145366.45left[1-left({frac {text{Station pressure in millibars}}{1013.25}}right)^{0.190284}right].}

In aviation, the pressure altitude is the indicated altitude obtained when an altimeter is set to an agreed baseline pressure under certain circumstances in which the aircraft’s altimeter would be unable to give a useful readout of the altitude. Examples would be landing at a very high altitude or near sea level under conditions of exceptionally high air pressure. Old altimeters were typically limited to displaying the altitude when set between 950 mb{displaystyle 950~mathrm {mb} }{displaystyle 950~mathrm {mb} } and 1030 mb{displaystyle 1030~mathrm {mb} }{displaystyle 1030~mathrm {mb} }. Standard pressure, the baseline used universally, is 1013.25{displaystyle 1013.25}{displaystyle 1013.25} hectopascals (hPa{displaystyle mathrm {hPa} }{displaystyle mathrm {hPa} }), which is equivalent to 1013.25 mb{displaystyle 1013.25~mathrm {mb} }{displaystyle 1013.25~mathrm {mb} } or 29.92{displaystyle 29.92}{displaystyle 29.92} inches of mercury (inHg{displaystyle mathrm {inHg} }{displaystyle mathrm {inHg} }). This setting is equivalent to the atmospheric pressure at mean sea level (MSL) in the ISA. Pressure altitude is primarily used in aircraft-performance calculations and in high-altitude flight (i.e., above the transition altitude).



QNE


QNE is an aeronautical code Q code. The term QNE refers to the indicated altitude at the landing runway threshold when 1013.25 mb{displaystyle 1013.25~mathrm {mb} }{displaystyle 1013.25~mathrm {mb} } or 29.92 inHg{displaystyle 29.92~mathrm {inHg} }{displaystyle 29.92~mathrm {inHg} } is set in the altimeter’s Kollsman window. In other words, it is the pressure altitude at the landing runway threshold.


Most aviation texts for PPL and CPL exams describe a process for finding the pressure altitude (in feet) using the following formula:


Pressure altitude (PA)=Elevation+1000×(29.92−Altimeter setting).{displaystyle {text{Pressure altitude (PA)}}={text{Elevation}}+1000times (29.92-{text{Altimeter setting}}).}{displaystyle {text{Pressure altitude (PA)}}={text{Elevation}}+1000times (29.92-{text{Altimeter setting}}).}

For example, if the airfield elevation is 500 ft{displaystyle 500~mathrm {ft} }{displaystyle 500~mathrm {ft} } and the altimeter setting is 29.32 inHg{displaystyle 29.32~mathrm {inHg} }{displaystyle 29.32~mathrm {inHg} }, then


PA=500+1000×(29.92−29.32)=500+1000×0.6=500+600=1100.{displaystyle {begin{aligned}{text{PA}}&=500+1000times (29.92-29.32)\&=500+1000times 0.6\&=500+600\&=1100.end{aligned}}}{displaystyle {begin{aligned}{text{PA}}&=500+1000times (29.92-29.32)\&=500+1000times 0.6\&=500+600\&=1100.end{aligned}}}

Alternatively,


Pressure altitude (PA)=Elevation+30×(1013−QNH).{displaystyle {text{Pressure altitude (PA)}}={text{Elevation}}+30times (1013-{text{QNH}}).}{displaystyle {text{Pressure altitude (PA)}}={text{Elevation}}+30times (1013-{text{QNH}}).}

For example, if the airfield elevation is 500 ft{displaystyle 500~mathrm {ft} }{displaystyle 500~mathrm {ft} } and the QNH is 993 mb{displaystyle 993~mathrm {mb} }{displaystyle 993~mathrm {mb} }, then


PA=500+30×(1013−993)=500+30×20=500+600=1100.{displaystyle {begin{aligned}{text{PA}}&=500+30times (1013-993)\&=500+30times 20\&=500+600\&=1100.end{aligned}}}{displaystyle {begin{aligned}{text{PA}}&=500+30times (1013-993)\&=500+30times 20\&=500+600\&=1100.end{aligned}}}

Aircraft Mode “C” transponders report the pressure altitude to air traffic control; corrections for atmospheric pressure variations are applied by the recipient of the data.


The relationship between static pressure and pressure altitude is defined in terms of properties of the ISA.



See also



  • QNH

  • Flight level

  • Density altitude

  • Standard conditions for temperature and pressure

  • Barometric formula



References





  1. ^ "Pressure Altitude" (PDF)..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output .citation q{quotes:"""""""'""'"}.mw-parser-output .citation .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-maint{display:none;color:#33aa33;margin-left:0.3em}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}




External links



  • Newbyte Atmospheric Calculator, Android Version



Comments

Post a Comment

Popular posts from this blog

Information security

Image
This article is part of a series on Information security Related security categories Internet security Cyberwarfare Computer security Mobile security Network security Threats Computer crime Vulnerability Eavesdropping Malware Spyware Ransomware Trojans Viruses Worms Rootkits Bootkits Keyloggers Screen scrapers Exploits Backdoors Logic bombs Payloads Denial of service Defenses Computer access control Application security Antivirus software Secure coding Secure by default Secure by design Secure operating systems Authentication Multi-factor authentication Authorization Data-centric security Encryption Firewall Intrusion detection system Mobile secure gateway Runtime application self-protection (RASP) v t e Information security , sometimes shortened to InfoSec , is the practice of preventing unauthorized access, use, disclosure, disruption, modification, inspection, recording or destruction of information. Th...
Read more

Volkswagen Group MQB platform

Image
The Volkswagen Group MQB platform is the company's strategy for shared modular design construction of its transverse, front-engine, front-wheel-drive layout (optional front-engine, four-wheel-drive layout) automobiles. Volkswagen spent roughly $60bn [1] developing this new platform and the cars employing it. The platform underpins a wide range of cars from the supermini class to the mid size SUV class. MQB allows Volkswagen to assemble any of its cars based on this platform across all of its MQB ready factories. This allows the Volkswagen group flexibility to shift production as needed between its different factories. Beginning in 2012, Volkswagen Group marketed the strategy under the code name MQB , which stands for Modularer Querbaukasten , translating from German to "Modular Transversal Toolkit" or "Modular Transverse Matrix". [2] [3] MQB is one strategy within VW's overall MB (Modularer Baukasten or modular matrix) program which also includes th...
Read more

Daniel Guggenheim

Image
Daniel Guggenheim 1925 photo Born ( 1856-07-09 ) July 9, 1856 Philadelphia, Pennsylvania Died September 28, 1930 (1930-09-28) (aged 74) Port Washington, New York Alma mater Peirce College Known for Battle for control of ASARCO Daniel Guggenheim Medal Spouse(s) Florence Shloss Children Meyer Robert Guggenheim Harry Guggenheim Gladys Eleanor Guggenheim Parent(s) Meyer Guggenheim Barbara Guggenheim Daniel Guggenheim, 1910 Daniel Guggenheim (July 9, 1856 – September 28, 1930) was an American mining magnate and philanthropist, and a son of Meyer and Barbara Guggenheim. Contents 1 Biography 2 Personal life 2.1 Aviation 2.2 Alaska 3 See also 4 References 5 Further reading 6 External links Biography Born and raised in Philadelphia, Daniel Guggenheim was sent to Switzerland as a young man to study the Swiss lace and embroidery business, and to serve as a buyer for his father's import firm. The...
Read more