Software enhancements take the guesswork out of interpreting weather radar
Why am I bouncing around in a 60-year-old aircraft, somewhere over southern Virginia? Because I am on a demo flight, in 's Convair 580 radar testbed, to see the latest in weather hazard-avoidance technology.
And the improvements become clear within seconds of lifting off fromas Honeywell's RDR-4000 IntuVue weather radar probes the clouds ahead of us. On the workstation screen in front of me, the radar display (see image) shows a swath of magenta indicating turbulence in the clouds.
But also on the display are new symbols indicating the likely presence of hail and lightning in the storm. And in the radar “shadow” beyond the clouds, which on a normal display could look deceptively dark and quiet, magenta cross-hatching warns the crew that the attenuated radar returns from the region are not reliable, and storms could exist there.
The flight is showcasing an enhanced version of the RDR-4000, which includes predictive hail and lightning detection as well as extended-range turbulence detection. Certified this year, the enhanced radar has entered service with a “large airline” launch customer, which is equippingwith the system.
Flight demonstrations to additional potential forward-fit and retrofit customers are underway using the twin-turboprop Convair 580, first flown in 1962 and the oldest of its type still flying, but used because its capacious nose makes it ideal as a radar testbed.
The radar enhancements are a result of a detailed analysis of inadvertent weather encounters resulting in hail and lightning damage or injuries caused by turbulence. This showed that a key factor was the crew's failure to gain weather situational awareness in time to reroute or avoid hazards, says Ratan Khatwa, Honeywell senior chief engineer for human factors.
Poor antenna tilt management and misinterpretation of radar returns were revealed as major factors, as well as a lack of knowledge of radar fundamentals and large variability in pilots' use of radar and in training standards. Honeywell has approached the identified programs in two steps.
“Part 1 was to simplify operation of the radar,” says Khatwa. This led to introduction of the RDR-4000 pulse-compression radar in the early 2000s. “Part 2, in 2012, is to make it easier to interpret the data,” with a software-only upgrade to add hail and lightning indication and increase turbulence-detection range by 20 nm to 60 nm.
The baseline RDR-4000 automates operation of the radar, and scans and stores a three-dimensional database of weather ahead of the aircraft from the ground to 60,000-ft. altitude, out to 320-nm range. The system automatically removes ground clutter from radar returns, using the terrain database from Honeywell's enhanced ground proximity warning system, and stores the weather data in a volumetric buffer.
In automatic mode, the radar displays weather along the flight path. Primary weather, within 4,000 ft. above and below the aircraft's altitude, is displayed in solid colors. Secondary weather, at higher or lower altitudes, is shown cross-hatched, to make the crew aware of storms that could affect the flight if they climb or descend.
In a conventional radar, a crew will probe the weather ahead by changing the radar-antenna tilt angle to look up and down to see whether it is possible to fly over or under approaching storm cells. With the RDR-4000, in manual mode, the pilot can select an altitude and see a horizontal slice through the volumetric buffer.
The software enhancements being introduced add the ability to predict the presence of hail or lightning in weather cells based on their radar reflectivity and to superimpose warning icons on the radar display. The density of icons on the screen is an indication of the likely intensity of hail or lightning in a storm.
The upgrade also adds rain echo attenuation compensation technology (React), which displays magenta “keep out” arcs behind intense storm cells, indicating where weather data in the radar shadow may not be reliable because the returns are outside a calibrated range. React has been a feature of Honeywell's business-aircraft radars since the 1980s, says Katwa, and the company is working on a version of the enhanced InuVue radar for business aviation.
Turbulence-detection range is extended by lengthening individual pulses within the pulse trains transmitted by the radar. This increases the radar power on target and extends range. And, as the Convair enters a limb of the storm towering to our starboard so the television news crew on board can film us bouncing around, I can personally vouch—this radar detects turbulence.