Your flight instructions guide


Airspeed and altitude information

The speed of an aircraft relative to itsairspeed to the speed of sound. For example,
surrounding air mass is called airspeed anda speed of Mach 0.7 means the aircraft is
is  normally  measured  in  Knots.flying  at  70%  of  the  speed  of  sound.
As you know already from school, the termThe speed of sound is variable. Depending on
"speed" relates to distance traveled per unitair temperature, relative humidity and
time.pressure, it is approximately 1 117 feet or
340.48 meters per second at 59 degrees
One Knot refers to one nautical mile perFahrenheit.
hour. One nautical mile is equal to 1.151
statute  miles  or  1.852  kilometers.By the way, Concorde crosses the Atlantic
ocean  with Mach 2.0 at 55 000 feet altitude.
The airspeed indicator displays the speed of
your airplane or helicopter through the airAltitude seems like a simple term, it means
by comparing ram air pressure with static airheight. But in aviation, it can have many
pressure. The greater the differential, themeanings. In this article I will guide you
greater  the  speed.through  the different terms and definitions.
Now let us take a closer look at the various1.  TRUE  ALTITUDE
definitions and meanings of the term
"airspeed".This is the actual or exact altitude above
mean  sea  levelnormally  measured  in  feet.
1.  INDICATED  AIRSPEED  -  IAS
2.  ABSOLUTE  ALTITUDE
This is the speed shown on the aircraft
airspeed indicator and is used in pilotThis is the actual or exact altitude above
controller  communications.the surface. We also refer to height above
ground level. If you fly over open water,
2.  CALIBRATED  AIRSPEED  -  CASabsolute  and  true  altitude  are  the same.
Calibrated airspeed is the indicated airspeed3.  INDICATED  ALTITUDE
corrected for installation and instrument
errors. Although these errors are minimizedIt is the altitude above mean sea level
by the manufacturer, they cannot be totallyindicated on the altimeter when set to the
eliminated throughout the full range ofcurrent  local  altimeter  setting.
operating  speeds.
Altimeter setting is the value to which the
3.  EQUIVALENT  AIRSPEED  -  EASpressure scale of the altimeter is set so the
altimeter indicates true altitude at field
Equivalent airspeed is calibrated airspeedelevation.
corrected for the compression of the air at a
particular altitude. In the higher speed4.  PRESSURE  ALTITUDE
ranges, an aircraft passes through the
atmosphere so rapidly that the air isPressure altitude is the altitude in the
compressed  in  front  of  it.standard atmosphere where pressure is the
same as where you are. It is indicated by the
This error, often called compressibility, isaltimeter when the barometric scale is set to
generally considered insignificant when29.92 inches of mercury or 1013.25 millibars.
operating  below  200  Knots.
5.  DENSITY  ALTITUDE
4.  TRUE  AIRSPEED  -  TAS
It is simply the pressure altitude corrected
True airspeed is the calibrated airspeed orfor non-standard temperature, pressure and
EAS as appropriate corrected for pressurehumidity.
altitude  and  temperature.
Density altitude is not a height reference.
It is the airspeed of an aircraft relative toIt is primarily used as an index to aircraft
undisturbed air and is used primarily inperformance.
flight planning. On a calm day, your true
airspeed is the same as ground speed assumingOn a hot day, the air becomes thinner and
level  flight.density altitude increases and vice versa on
a cold day. High density altitude is a real
5.  MACHhazard since it reduces aircraft performance
in three ways. It reduces engine power,
Mach is theratio of the aircraft's truethrust and lift.



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