Thanks for the explanation, M2dude, and please excuse the thread drift, as I was confused in prior posts who was what kind of engineer. I'm truly asking to learn. As you must know, signing for return to service in the US requires a licensed A&P, Aircraft & Powerplant mechanic. Engineers in the US usually have more theoretical education than A&P, but are not licensed. They are the design engineers at the manufacturers and the service engineers at airlines who design and document repairs and modifications. Are only your licensed engineers authorized to release for return to service, or do you have other levels of mechanics and technicians with authorization?
Still, a person calling himself engineer without specifying what type confuses me.
Oh, I'm sure most of the airlines have their radar antenna maintenance "on condition," rather than on "hard time." I knew one FAA Principal Avionics Inspector who required radar antenna overhaul at 9,000 hours, as he insisted, rightly, that mechanical parts wear out. Their MTBUR, Mean Time Between Unscheduled Removals, was much higher than other airlines as a result.
As for too many early radars in the area causing ATC radar problems: highly unlikely, as ATC radar has been S band, around 2 GHz, like your microwave oven, while the early RCA radars were C band, above 5 GHz. More likely, too many transponder replies were overloading ATC. That was one reason for the ALT OFF switch on the transponder control panel.
The RCA radars of the 1960s and 70s, AVQ-10 and AVQ-30 and the Bendix RDR-1E and RDR-1F of the same era - and beyond - used magnetrons of about 55KW peak output. (The RDR- and some later RCA are X-band, 9.3 GHz.) That works out to about 750 watts average (heating) power - hmmm - the same as a full size microwave oven. The actual unsafe distance for personnel is a 15 foot arc in front of the radome. McDouglas used to have those areas painted in red on the concrete on the flight ramp where the new planes were parked.
Sometimes there would be rabbit tracks on the radar display in the days of old, from picking up another plane's radar. That was eliminated with the Arinc 700 generation by varying the pulses so the radar would track only its own.
With the 767 came Arinc 700 avionics, and the first new generation of Wx radars, the Collins WXR-700, and the Bendix RDR-4A. They had solid state transmitters of 60 to 150 watts peak power, for an average heating power of less than one watt. You will have to be close enough to get pranged in the head by the swinging antenna before you are harmed by that power level.
Why do these radar distance cautions still exist? Old beliefs and old airplanes die hard. There are still airliners flying with the old magnetron radars.
Meanwhile, your DMEs and maybe transponder and TCAS are probably transmitting continuously with up to 500 watts peak power. Ever see a precaution about being too close to their antennas?
GB
Last edited by Graybeard; 29th January 2010 at 15:59.
Reason: mispel