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Honeywell’s new RDR 7000 can interface with a variety of current-generation cockpit display units as long as they support ARINC 708 or 453 interfaces.
(Images courtesy of Honeywell).
was a change that you would expect to have been met with great joy. Well, not so much...
The fact of the matter was, with 6.5 kilowatts of transmitter power, the old analog type radars did a fine job of punching electronic holes in storms, so pilots could see what was inside. While this was good, it wasn’t without its drawbacks. In some instances, they’d actually give a false impression of the severity of the storm, which led more than one unsuspecting pilot to fly into areas they shouldn’t have.
“It’s a hard thing for people to get their minds around, but our new-gen- eration systems like the GWX70 and GWX80 only use 40 watts of transmit power,” Andrews continued. “They think lower power means less per- formance, but what it comes down to is the difference between raw trans- mitter power and advanced digital processing.”
“What we do with the lower-power, solid-state systems is to use longer pulses and digital processing on the waveform to put the same, if not more, energy on the target,” he says. “Even though we are using a lot less power, we are getting better weather depicting performance from the unit.”
Along with an equal-to, or better- than a magnetron image, today’s ra- dars are a lot more reliable than their Neolithic ancestors.
“As you can imagine, as we go from legacy magnetron-based systems to ful- ly solid-state units, we get a huge spike in the reliability,” stated Vipul Gupta, product line leader, weather radar, Honeywell/BendixKing. “Of course, it’s a bit dependent on the aircraft type, but we are seeing reliability increas- ing two or three times – up to 16,000 to 20,000 hours MTBF.”
While the dramatic increase in re- liability was a driving factor for the manufacturers to begin the switch to digital, solid-state technology, it was just the beginning of the benefits the new format would deliver.
“One of the immediate benefits of digital radars was doppler processing, which is really hard to do with a mag- netron. With digital signal processing, you are transmitting exactly the same
for you today, let’s go back to when all the weather was monochrome green. Radar had been around for a long time, but it took a few leaps in manu- facturing technologies to shrink the antenna, magnetron, and all the as- sociated mechanicals and electronics down to where it would fit in the front
of even a large airliner.
Bendix Avionics (now Honeywell/
BendixKing) introduced the first com- mercial airborne weather radar, its RDR-1, in 1956. The ability for pilots to see rain, and thus avoid turbulence, garnered so much popular press that airlines and aircraft manufacturers went so far as to tout “Radar Equipped” in advertising and on the sides of their aircraft.
“The magnetron is a very high-pow- ered device that’s very similar to what you’d find in an old-style tube TV,” ex- plained Dr. Joel Andrews, team leader design engineering, Garmin Aviation. “And just like those old TVs, the old weather radars had to warm up when you turned them on. They also had is- sues with the magnetrons losing power and the screen images getting dimmer over time.”
That meant that the airlines were having to change out the magnetrons and some of the receiver/transmitter antenna’s mechanical systems every 500 to 600 hours. But, when they also
had to swap out a big radial engine every month or so, it wasn’t that big of a deal.
Then along came the Jet Age, and everything changed. Faster aircraft meant that radars had to show weather at longer ranges and with a higher degree of accuracy. And, the fact that jet engines operated for thousands of hours put pressure on radar manu- facturers to develop more reliable hardware.
As technology evolved, so did the reliability, consistency and signal clar- ity of the magnetrons. In fact, many current-generation weather radar sys- tems still rely on them to generate their beam energy. You’re probably f lying with one right now.
Less Power, Better Processing
“We actually used the magnetron in our first radar, the Garmin GWX68,” Andrews says. “It had 6.5 kilowatts of transmit power at 5,000 volts. It’s not something you want to mess with. They were all very high-power units.”
And that high-power requirement was one reason that the magnetrons powering the legacy-generation ra- dar systems had such short lifespans. The solution was to transition to new- generation magnetrons or, better yet, switch to solid-state designs, which
September 2020 / TWIN & TURBINE • 5