Ed Rasimus wrote:
On 19 Jun 2006 07:50:02 -0700, "Don McIntyre" wrote:

While reading through Hans-Heiri Stapfer's "Walk Around MiG-21 Fishbed
Part 1" (Squadron-Signal), he makes mention of a temperature probe
mounted low on the nose on an MiG-21F-13. Why would a radar rangefinder
need to know the OAT?

Dunno about MiGs, but every high performance tactical aircraft I ever
dealt with had an OAT input to the Central Air Data Computer (or
whatever it was called on a particular system.) Air temp is a
component of density and that is a factor that impacts range of a
weapon.


AFAIK temperature determins the speed of sound all on its own. Air
density seems to have nothing to do with it unless you get to near
space. Air density of course would determin dymanic pressure.

Technically the speed of sound is the square root of the ratio of air
pressure over air density all multiplied by a constant known as adiatic
exponent of air. However as the ratio of pressure to density is a
constant at a specific temperature temperature is all that is needed.

Best look at it here
http://www.sengpielaudio.com/SpeedOfSoundPressure.pdf

The WW2 British blind bombing system Oboe made compensations for air
density variations so possibly modern radars use it as well, probably
not so much for ranging but for doppler or anti-jamming measures.

Since dum**** fighter drivers don't like numbers the presentation on
the radar screen would be little lines indicating min and max ranges.
When the radar gets a range, the computer whiz-bang calculates how far
the gizmo can get at the current density altitude.


Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
www.thunderchief.org
www.thundertales.blogspot.com