System adjusts antenna angles to take account of known terrain, cutting pilot workload
Airbus has completed certification on all its models of Honeywell's autotilt radar system, which works with a terrain database to automatically tilt the weather radar for the optimum picture.
Honeywell, which hopes the recent Airbus clearance will signal a surge in both forward fit and retrofit orders, says the upgrade reduces pilot workload and increases safety by improving situational awareness. Originally developed in 2000, the software-based enhancement correlates data from the radar scan with terrain data taken directly from the aircraft's enhanced ground proximity warning system (EGPWS), and will be further developed for the A380 as part of its aircraft environment surveillance system.
By adjusting the antenna tilt angle to take account of known terrain, Honeywell says the system allows crews to concentrate fully on other flying tasks by removing the ambiguity from the radar data. "It gets you comfortable with what you're seeing because you aren't confused. It makes everything instantly clearer," says Honeywell flight test operations chief pilot Markus Johnson, who flies the company's Convair 580 testbed and autotilt demonstrator.
"What we're aiming to do is to show ground returns on the outer edge of the display and allow storm cells and other weather to appear in the foreground," says Honeywell radar product line manager Bruce Dawson. "Even with diligent manual tilt management this is time-consuming and inconsistent."
In most current aircraft, Dawson says the manually controlled tilt setting is either too high and fails to show any weather, or underscans and becomes confused with ground clutter. The autotilt system works with the EGPWS database and radar transmitter processor to calculate antenna tilt angles in five segments across 180°.
Each scan is made up of two 45° segments at the left and right limits of the horizontal scan, in addition to three higher-resolution 30° segments in the more critical coverage area directly in the flightpath. Alternative scans provide long- and short-range settings for all five segments.
Each segment can have its own value depending on range and underlying terrain. During a demonstration for Flight International, for example, the agility of the system was apparent during an instrument landing system approach to a runway sandwiched between tall mountains and open sea. In a single scan at a range of up to 75km (40nm) the tilt angle rose above 11° for the segment covering the nearby peaks, while angles of segments from the same scan covering the flatter land and sea were only 2-3°.
With more than 340 orders taken for mostly Boeing aircraft operated by major carriers such as Japan Air Lines, Singapore Airlines and United Airlines, Dawson hopes the Airbus certification will boost sales to around 500 by the first quarter of 2005.
In a parallel move, Airbus has also certificated Honeywell's related dual-redundant antenna drive (DRD) on all versions of the A330/A340 family.
The DRD, which is compatible with both RDR-4A and -4B radars, eliminates single-point failure modes in both the azimuth and elevation motors and dramatically increases overall reliability.
GUY NORRIS / SEATTLE
Source: Flight International
