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OAT for RADAR on fighters?
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? |
#2
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OAT for RADAR on fighters?
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. 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 |
#3
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OAT for RADAR on fighters?
Thanks, Ed, I knew you'd come through. Ah, dum**** RADAR operators in
the back of big airplanes don't really like numbers, either, but once you get engineers involved who know better than the people that have to use the systems... Don 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. 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 |
#4
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OAT for RADAR on fighters?
In message , Ed Rasimus
writes 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. I love Ed's knack for concise, elegant and accurate descriptions. If only we were allowed to use such enjoyably accessible styles in official handbooks... (I do what I can with a war on the passive voice, but it's a slow and uphill fight) -- Paul J. Adam |
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OAT for RADAR on fighters?
On Mon, 19 Jun 2006 21:38:42 +0100, "Paul J. Adam"
wrote: In message , Ed Rasimus writes 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. I love Ed's knack for concise, elegant and accurate descriptions. If only we were allowed to use such enjoyably accessible styles in official handbooks... (I do what I can with a war on the passive voice, but it's a slow and uphill fight) Bless you and know that the fight against the passive voice is a noble crusade. We are dealing with it in the US Congress even as we speak. Those damn passivists are simply cowards...and their voices are so whiney. I think I manage to stay away from passivity pretty well, but got taken to task the other day by someone who read my blog regarding my dangling particles or some-such. That's an indignity up with which I need not put. Ed Rasimus Fighter Pilot (USAF-Ret) "When Thunder Rolled" www.thunderchief.org www.thundertales.blogspot.com |
#6
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OAT for RADAR on fighters?
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 |
#7
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OAT for RADAR on fighters?
On 20 Jun 2006 07:27:56 -0700, "Eunometic"
wrote: 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 You are correct, but irrelevant to the discussion of the relationship between OAT and radar ranging. Mach is temperature dependent and since the atmosphere gets colder as you rise, the speed of sound will change. But, while high performance aircraft do have mach indicators, they operate on the basis of airspeed--which leads to an entirely more complex discussion as we start to grapple with indicated, calibrated, equivalent and true airspeeds as well as ground speed along with the trigonometric impact of dive/climb angle relating to bombing. Highly recommend you don't fly landing approach on mach. Ed Rasimus Fighter Pilot (USAF-Ret) "When Thunder Rolled" www.thunderchief.org www.thundertales.blogspot.com |
#8
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OAT for RADAR on fighters?
Hey, Ed, M 0.1 is a maximum cruising speed for most old fuds on the
Green Stamp. BTW I don't think that OAT probe has much to do with the radar. I'd suspect it's for the air data computer to feed the Machmeter (for some reason the 21 has a big one, probably so the pilot will fly the exact Mach commanded by his controller) and the engine and anti-ice systems. BTW when the 21 was first placed in commission Sov philosophy didn't allow the interceptor pilot much freedom at all; he was essentially just the interface between the GCI controller and the two Atolls. I used to watch their training intercepts on GCI radar at one base i was at. Cheers - Walt BJ |
#9
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OAT for RADAR on fighters?
Ed Rasimus nicked: That's an indignity up with which I need not put. Churchill. Gotcha. (hah -- it's a pretty good line.) Billy http://www.two--four.net/weblog.php |
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