SSR Radar Range at 4000 AGL?

[Richard_K_Spyte]

How far can SSR see a transponder that is 4000 AGL? Or more practically, how far NW of Winnipeg could ATC pick up a transponder equipped aircraft?

[photofly]

The usual line-of-sight formula is distance (nm) = 1.23 x √(height above ground station in feet)

So the range at 4000agl would be about 80nm.

If the radar head is elevated by (say) 200ft, the range is extended by 20 miles or so.

[Richard_K_Spyte]

That's what I thought, thanks for confirming it.

[cyeg66]

Had a little tiff with a terminal controller, did ya?

[AuxBatOn]

It depends on terrain. photofly's theory works on a perfectly flat terrain. As soon as you put hills and valleys in between the radar station and the aircraft, it doesn't work.

[fanspeed]

It depends on terrain. photofly's theory works on a perfectly flat terrain. As soon as you put hills and valleys in between the radar station and the aircraft, it doesn't work.

The OP did say Winnipeg...

[photofly]

It depends on terrain. photofly's theory works on a perfectly flat terrain. As soon as you put hills and valleys in between the radar station and the aircraft, it doesn't work.

It's not my personal theory, it's what TC thinks CPL candidates should know, and something it tests them on. I have no idea if it works in practice or not, I've never seen the need to test it.

[Richard_K_Spyte]

Had a little tiff with a terminal controller, did ya?

A minor difference of opinion betwixt gentlemen.

[BTyyj]

Flying between VORs, I've calculated beforehand the line-of-sight as per TC's formula then tested it in the air. I've found the calculation to be a fairly liberal estimate at best, as the data becomes too unreliable well before reaching the maximum as per the calculation. Obviously, this equation assumes flat ground, so obstacles may be the contributing factor.

[B52]

the square root of the altitude x 1.23 is the correct exam formula to remember.
Practice is entirely different.

Take the 777 that CNN claims has "vanished into the Indian Ocean" etc.

The only credible observer was Michael McKay, several hundred kilometers
and he guessed it was 50-70 kilometers away.

When the moon is low on the horizon, it looks bigger, its an optical illusion.

Radio and optical can bend over the horizon.

Radio can and does travel following the curvature of the earth.

If you have Isobars going between the two locations, and
an inversion, you are "cooking on gas" when it comes to long distance
VHF, UHF and even 2ndry and or even primary radar.

I remember watching Primary radar and the controller explained that the objects
we were looking at were 300 nm away due to tropo ducting.

Inversions, say over lake Winnipeg, would provide a good probability if not certainty of
ducting.

Same goes for UHF.

Live in the tropics, with NO TV local and watch the channels explode when ducting becomes alive..