Eddie Sez:

The first step in understanding airborne radar is knowing what is being transmitted from the radar dish (or plate). Do you need to know this stuff to use your radar? No. Do you need it to effectively use your radar? I think so.

What follows are quotes from the sources listed below, mostly an excellent tutorial from Stephen D. Hammack at Honeywell, as well as my comments in blue.


Radar Energy and Power Tutorial

[Honeywell Direct-To, FMS Quarterly Update and Newsletter, December 2012, page 4.


Radar Example

Figure: Radar antenna assembly, from G450 Maintenance Manual, §34-44-00, figure 2.

A typical aircraft weather radar system, the G450 shown here, makes the mechanics of antenna aim and energy transparent to the pilot. More on that below, under Radar Reflection Characteristics.


Radar Signal Flow

Figure: Radar Signal Flow, from Honeywell Airborne Weather Radar Training Part 1, Slide 12.

The purpose of airborne weather radar is to find the distance and direction of weather in relation to the aircraft, as well as to discern a few of the target's characteristics. The radar transmitter sends a measur ed pulse of energy in a specific direction. The target reflects some of that energy back. The radar times the round-trip distance of the signal to determine distance, the amplitude of the return to determine strength, and the direction of the pulse going out to determine direction. The energy of the pulse has a direct relation to the reflection.


Radar Reflection Characteristics

Figure: Radar Reflection Characteristics, from Honeywell Airborne Weather Radar Training Part 1, Slide 16.

The energy level of the radar signal going out directly impacts the energy of the reflection coming back in. Too little energy will not be reflected at all; too much energy risks going right through the target or skewing the reflection intensity. Getting it just right so that the information display to the pilot is all a matter of gain and calibration. More about:


Book Notes

Portions of this page can be found in the book Flight Lessons 1: Basic Flight, Chapter 28.


References

Gulfstream G450 Maintenance Manual, Revision 18, Dec 12, 2013

Honeywell Airborne Weather Radar Training, Rev E, 12/09/02, Honeywell Inc. Commercial Flight Systems Group, Phoenix, AZ.

Honeywell Direct-To, FMS Quarterly Update and Newsletter, December 2012