Here’s a familiar scenario: An owner steps up to a twin or a high-performance single that’s equipped with an older radar system. Unwilling to spend the money and effort to fix it or replace it, they pay to have the system removed. Sadly, many of these owners don’t recognize the benefits of ship’s radar.
The decision to fly without radar—particularly at high altitudes—might seem easy to pilots who grew up with satellite-delivered cockpit weather. Depending on your view of weather avoidance, or tactical penetration, real-time ship’s radar might be imperative for your mission.
There’s no question that weather radar maintenance and upgrades can be pricey. We're talking the potential for several thousands of dollars for repair and tens of thousands for upgrade. On the other hand, ship’s radar can expand the mission. In volatile weather, there’s a reason why controllers ask if you have onboard weather radar.
Where radar upgrades were once in decline, the ability to overlay weather radar on GPS navigators, multi function display systems and integrated glass cockpits has jump-started the radar upgrade market. In our view, radar design and technology that was once only available to the jet market is making radar system upgrades more convincing for lower-end applications.
Ship's Radar 101
For those that are unfamiliar with ship’s weather radar, here’s a basic review.
Pulsed radar locates targets (precipitation or ground clutter) by transmitting a microwave pulse beam that reflects off the precipitation and back to the radar receiver as a return; this is often called an echo. The microwave pulses are focused and radiated by the system’s antenna (often called a dish) that’s located in the nose of twins or enclosed in a wing pod on singles. This structural enclosure is called a radome. The same antenna is used for both transmitting and receiving.
The returned signal is processed and displayed on either a dedicated radar display, or as a remote input to an MFD. The MFD option has been the saving grace for a somewhat stagnant GA radar market because the color MFD has greatly enhanced the display and effective usefulness of aging systems. If you’ve made the switch from a monochrome radar display to a VGA display you understand the benefits and can appreciate the enhanced view.
Think of the radar beam that’s transmitted from the aircraft as a spotlight. As the beam travels farther it gets wider, limiting performance. The smaller the antenna, the wider the radar beam and the more its energy is dispersed over each mile it travels away from the aircraft. As a rule, the larger the antenna, the better the performance. Smaller twins and singles might be limited to radar systems with 10-inch antennas (10-degree beam) because the aircraft’s nose or wing-mounted radome simply can’t accommodate a larger antenna. Consider that an airliner might have a 30-inch radar antenna.
It’s all about beam width. When scanning longer distances with a smaller antenna, precipitation can’t fill the entire beam width, so a real-deal Level-5 might be displayed as something much smaller. As a result, you’ll need to fly closer to the storm to obtain a more accurate return.
Bendix King RDR2000 Vertical Profile
The digital RDR2000 has an earned reputation for both reliability and performance. We searched the used market and discovered that used ART2000 units (the ART2000 is the main radar system less a display) demand well over $10,000. According to seasoned radar repair shops, including Fieldtech Avionics and Duncan Avionics, the RDR2000 is one of the most demanded radar systems for piston singles, twins and even light turbine applications. There's also the high-powered RDR2100 that's appropriate for jets.
The vertical profile feature provides just that—a vertical picture of a pilot-selected cross-section of a storm. The RDR2000 has a 270 nautical mile range, paints in four colors and has 4.0 kW of power output. The higher-powered RDR2100 has 6.0 kW of power that can scan out to 320 nautical miles.
The RDR2000-series has long been a part of the Bendix King product line and is a major optional interface for the company's new KSN770 retrofit GPS navigator. It's still used by some aircraft manufacturers as standard equipment, including Pilatus, on the PC12NG.
The ART2000/2100 was originally designed to display on the IN-182 dedicated radar display (no longer available). You can, however, interface the system with Avidyne's EX600 MFD when equipped with the proper radar interface kit. This kit comes with a premanufactured radar interface cable that connects the MFD with the radar. Avidyne says the future IFD540 GPS navigator will be compatible with the ART2000 system.
A new ART2000 has a list price of nearly $23,000. We don't see anything wrong with buying a used ART2000, as long as you buy it from a reputable source that has radar testing and repair capability. It should include a warranty and appropriate airworthiness paperwork.
Garmin's Digital GWX-series
Flash back to the year 2000 when Garmin purchased the rights to the King KWX56 radar (a system that was supported by the late Narco Avionics). It was then that we realized Garmin was serious about stepping into the heavier aircraft market.
The KWX56 was a case study for how to make an older radar new—and more reliable. It was the magnetron that Garmin focused on the most, since this component is notoriously the most expensive and problematic component on a ship's radar.
Garmin also reworked the dish array into a flat plate antenna, which provided a sizable gain in transmit power. How much power? The GWX68 is spec'd at 6500 watts—nearly twice that of vintage systems. More power improves range and resolution not only at the higher end but also at the lower end of the spectrum. Where other systems struggle at painting reliable returns at close distance, the GWX68 excels and has a 2.5-mile scan range. This means better awareness on an approach and when trying to weave a path around cells.
As you might expect from a higher-end radar (and perhaps to mimick Honeywell's RDR2000) there's also a vertical mode that scans a 60-degree vertical arc. Since Honeywell calls this vertical profile, Garmin calls it vertical scanning. There's even a high-end function borrowed from jet radar systems, called sector scanning. With sector scan, the system can look out at angles up to 90 degrees, even when manuevering. Again, this is helpful when manuevering in close proximity to storms. For better awareness at greater distances, the target alert feature can sniff out stronger returns in better detail.
The recently-introduced GWX70 picks up where the GWX68 left off (both are available in Garmin's line-up) and utlizes a solid-state transmitter. This transmitter eliminates the magnetron while also bringing turbulence-sniffing Doppler capability to the system.
You would think that a solid-state transmitter increases the transmit power of the radar, but that's not the case. Consider that the GWX68 has 6500 watts of power through its high-power magnetron, but the solid-state GXW70 only has 40 watts of power, while still providing better range and reducing ground clutter.
The other enhancement comes from a new processor that utlizes digital signal processing technology (DSP). Garmin says that by using a DSP processor it's able to gain better control of the radar's pulse width and signal output. DSP, says Garmin, overcomes the challenge of obtaining an accurate picture at longer ranges. While a magnetron-powered radar pumps out huge amounts of power, the clarity of the resulting long-range returns are compromised—or in some cases, missed entirely.
Doppler capability requires a larger antenna (either the 12, 14 or 18-inch models). While the GWX70 is offered in a 10-inch configuration and can bolt into an existing Garmin GWX68 installation, the Doppler model will be off limits to aircraft with a smaller radome. The GWX70 with a 10-inch antenna starts at $21,000—the same price as the magnetron-equipped GWX68.
Caring For The Radome
No matter which system you chose, you’ll want to be certain the existing radome is up to the task. A radome lives a hard life and can ultimately contribute to poor radar performance. The surface paint and primer often erodes, peels or cracks. Take a look at the nose on a radar-equipped aircraft and you’ll see the damaging effects of rain, high velocity airflow, grit and other contaminants.
It’s not a simple task to refinish a radome surface (spraying the surface with a can of spray paint isn’t the correct approach). The typical radome is made of a honeycomb core, layered fore and aft with resin-impregnated fiberglass facings. It's generally not enough to rattle-can a deteriorated radome. It might make it look better, but don't expect gains in performance.
Before sending a radome out for professional evaluation, you might conduct a crude test of your own. One is the coin test to evaluate the bonding of the lamination. Take the thin edge of a larger coin and tap various areas of the radome while listening for undesirable dull thunking sounds. Instead, a firm click is what you generally want to hear.
You can also remove the radome for a visual inspection (this could be a two-person job on some aircraft). Hold the radome in the bright sunlight and look carefully at the honeycomb for debonding, cracks and puncture holes. When putting the radome back on, be sure to reconnect the glideslope antenna that's often attached to the inside, which is the case on smaller Beech twins.
Finally, whatever you do, don't operate the radar on the ground (in any mode other than test and standby) anywhere near major structures and humans unless you want to toast the magnetron and the human.
Put a Pencil On It
When getting proposals for avionics that can accomodate radar overlay, it's worth it to at least get a quote for a new or used radar upgrade. Your shop will know which systems are compatible with the gear being installed and which systems will fit the existing radome.
The physical radar installation isn't necessarily complex but could require sizable electrical interfacing, especially when tying into an AHARS system for roll and pitch stabilization. Garmin's GWX systems are interconnected via ethernet databus and will require healthy amounts of configuration, set-up and flight testing.
A new radar installation won't be cheap, but it could be the better choice than sinking money into older systems that are likely to fail again. Better yet, it could expand your mission while complimenting an onboard satellite weather and lightning detection system.