Still not getting how excactly it (the radar) works though, sounds like I was correct in saying that it uses the radar to determine doppler shift on precipitation returns?
Yes it is doppler shift. If you don't understand doppler do a little research, it is a basic concept.
But how does it sense wind direction and velocity ahead of the airplane? (horizontal head/tail) What is it painting? As it is true your not always going to have rain with windshear.
Predictive radar systems are targeted at downbursts coming from thunderstorms. Even so-called "dry" microbursts contain some precipitation so the radar system should be effective to some extent in that environment.
Predictive windshear using radar requires the presence of precipitation. This is not really a limitation. There is no historical evidence of windshear bringing down commercial aircraft in the absence of significant precipitation.
As for my question regarding the beam itself, I understand it is x wave and is transmited as a frequency signal is in watts. But how is the power generated?
The microwave power is generated like any radio signal. There is both a transmitter and a receiver as components of the radar. The key to radar is, the transmission is focused into a narrow beam which is deliberately focused on the area ahead. Traditionally that is what the saucer shaped antenna is for. (Much like the light of a flashlight is focused into a narrow beam.) The reason it detects rain so well is that rain also has a concave surface to focus the return back at the antenna. This is why snow and ice particles don't paint well, if at all. Instead the signal gets dispersed in all directions whereas rain drops focus the return signal back at the transmission point. The X frequency was selected because it is the best compromise of frequencies as far as ability to penetrate into weather and give a more accurate display. But it is still very prone to attenuation of signal by heavy rain.
I have flown the system for a few years in thunderstorm environments. I've found it to be reliable and not prone to false alarms in sharp contrast to reactive systems.
Last edited by saline; 29th Apr 2005 at 13:55.