Flying Blind Takes on Whole New Meaning

Pilots in military and civil aircraft can now land at small, rural, secondary or unprepared airfield runways despite conditions of heavy fog, snow, rain or smoke. Millimeter-wave radar-based technology originating in missile-seeker research allows aircraft landings in zero visibility and zero ceiling conditions. Ground-based airport equipment is not required.

Known as the autonomous landing guidance, or ALG, system, the aircraft-mounted millimeter-wave technology’s two-year proof-of-concept phase involved development, demonstration and flight testing on various aircraft to verify ALG’s air worthiness.

The ALG system includes a millimeter-wave radar antenna/transceiver and a signal processor that converts the radar output to video for head-up display (HUD) or to standard HUD symbology. The radar was tested on a Cessna 402, a United Airlines 727-200 transport, the U.S. Air Force Speckled Trout program’s C-135 and a Hercules C-130 aircraft.

BAE Systems, the British company that also developed fly-by-wire and airport autonomous-landing technologies, developed the ALG prototype and put it through more than 100 hours of flight testing in all types of weather conditions during day and night operations. Additional flight tests on a C-130 aircraft, often used for special operations, involved instrument-landing conditions down to 700 feet runway visual range.

After approximately 50 hours of successful ALG flights using a vision restriction device in the cockpit for prepared airfield operations, approval followed for landings in actual instrument-landing conditions down to zero/zero. Landings took place on austere runways—unimproved dirt landing strips. Special operations forces gain significant advantages when units can be inserted by aircraft in remote unprepared areas to surprise an adversary during adverse weather conditions.

During flight testing, company officials emphasize, radar performance met all operational objectives in low-visibility testing. “The runway was consistently identified at 500 to 600 feet above ground level. Runway light structures were consistently visible on the radar image throughout the approach. Even in dense fog, the ALG let the pilot clearly see the runway to land,” the officials add.

The millimeter-wave system provides a clear image of the runway to the pilot on a head-up display. Landing in low-visibility conditions would otherwise require Category III autonomous-landing equipment for the runway as well as on the aircraft. ALG-configured aircraft are capable of landing at Category I (small) airports in Category III (extremely adverse) conditions. During flight testing, obstacles were intentionally moved onto the runway to determine if the pilot could locate them.

In one flight demonstration using the C-130, a jeep was purposely parked on the runway as the ALG-equipped aircraft made a landing approach. The co-pilot could see only dense fog out of his right seat windows and could not spot the runway. Meanwhile, the pilot could clearly see not only the runway but also a parked vehicle and a human walking away from it. This sensor system can easily be mounted on any type of aircraft to allow precision and nonprecision approaches in instrument-landing conditions in day or night.

This system gives the pilot the ability to taxi, take off, land and roll out on a range of surfaces—concrete, asphalt, dirt and dry lake bed—regardless of weather or light conditions. The ALG provides the capability to outline unmarked runways by using radar reflectors or other aids, if necessary. With this radar, weather becomes an ally instead of a barrier, providing a strategic advantage and the element of surprise. The ALG system also improves safety of ground troops in situations requiring rapid deployments.

Commercial airline advantages with the ALG include improved on-time performance, a major competitive edge and enhanced passenger satisfaction. Direct operational cost savings could be gained from a decrease in flight diversions and delays due to low-visibility conditions. Other benefits include improved safety in landings and takeoffs when a pilot can see obstructions, difficult terrain and other aircraft or vehicles on the runway despite bad weather. The technology also will give planners more choices for route expansions because of decreased pilot dependence on airport ground infrastructure.             —CAR