GUY NORRIS / SEATTLE
A host of technologies in development could reduce runway incursions even further by, among other things, enhancing visibility
Visibility is bad. Gusts of rain burst on the cockpit windshield, and ragged cloud obscures the runway lights a short distance ahead. The crew peer anxiously into the night and are advised they are on the tail of another aircraft on short finals to the same runway. Will it clear the runway in time? When will the crew visually acquire the runway and how long will they have to make the crucial decision between a safe landing or a go-around?
In this case the crew has plenty of information to assess the danger of a potential runway incursion. This is the flightdeck of Boeing's 737-900 technology demonstrator (BTD). The crew can view the outside world through a head-up display (HUD) fed with thermal imagery from a cluster of infrared (IR) cameras beneath the radome.
New technologies
The demonstrator is packed with new and emerging flightdeck technologies, at least three of which are aimed at improving crew situational awareness and the detection of runway incursions. Boeing classes all three as "blue sky" - although the system manufacturers believe service introduction is a lot closer than the term suggests. A competing version of one technology, an enhanced vision system (EVS) developed by a Gulfstream-led team of BAE Systems, Honeywell and Kollsman, entered service in May on a US Navy-operated C-37A (Gulfstream V).
Technologies include two Rockwell Collins-developed packages; a synthetic vision system (SVS) and a surface guidance system (SGS) which is in joint development with Smiths Aerospace and Jeppesen. The BTD also mounted two EVSs, one from CMC Electronics of Canada, the other from Portland-based Max-Viz, a relative newcomer formed mostly by ex-employees of BAE Systems Canada, now CMC.
The SVS produces a computer-generated, real-time image of the terrain in front of the aircraft which is displayed on the head-down display (HDD). The SVS is the basis for Rockwell Collins' vision of a "pathway in the sky" and is "probably a Sonic Cruiser idea", says Boeing, which believes introduction of the product could be four to six years away. While SVS can be adapted to display aircraft hazards, including conflicting traffic on the ground, its prime focus is on preventing controlled flight into terrain and on enhancing approach precision and flightpath stability.
A nearer-term option, described by Boeing as "a great one to bundle with EVS", is the surface guidance concept also under study by Rockwell Collins Flight Dynamics. SGS evolved from the company's original head-up-guidance (HGS) development work and comes on the heels of "runway-remaining" and post-landing roll-out guidance features developed for its HUDs. "There are problems of avoiding runway incursions and getting to the gate when visibility is low," says Rockwell Collins Flight Dynamics president John Desmond.
The SGS works with the existing HUD and HDD to guide the crew along pre-approved routes between the terminal and the runway, including the transition to high- and low-speed runway exits after touchdown. "That's where you get the value of reduced runway time, by freeing up concrete and increasing utilisation of the high-speed turn-offs and reducing runway occupancy," says Desmond.
SGS indicates taxiways, forthcoming turns, hold lines, turn-trend vectors and other guidance data. Initially, the system will use pre-defined routes stored in the flight management system database. Advanced systems will transfer clearances by datalink and use global positioning (GPS) and automatic dependent surveillance-broadcast (ADS-B) technology to improve integrity, enhance safety and accuracy.
"We see situational awareness and taxi guidance as the first steps," says Desmond. "We're trying to decide exactly where we are going with it - what functions are of value and which can be implemented." High-speed turn-off guidance and other features that could increase average taxi-speeds in bad visibility or night by 10- 20% could be included in step two or three, says Desmond. SGS is being developed with the help of Delta Air Lines crews in a FlightSafety Boeing 737 simulator in Atlanta. Development flight tests are set for next year. "We expect to have a certificated system at the end of 2004," Desmond says. The SGS will be a software upgrade to the HGS-4000 HUD.
Certification in sight
The HUD is crucial to both EVS options flown on Boeing's demonstrator. CMC Electronics plans to certificate its SureSight EVS in the fourth quarter and is "working closely with a HUD manufacturer and one of the world's larger aircraft manufacturers" (thought to be Thales and Bombardier) on its first application for a corporate aircraft. The system uses a cooled dual-band, focal- plane array IR sensor operating in the 1-5µm range. The CMC system uses INSB (indium antimonide) sensors that convert IR energy into electricity.
The SureSight sensor is housed in the radome, which is modified to include a small IR-transparent window for IR sensor. CMC expects the package, including wiring and harnesses, to weigh "less than 22lb [10kg]". CMC also plans to develop the SureSight product into a modular family with varying capabilities to suit different requirements and budgets. "We are looking at another IR sensor which is less costly as a taxi-aid and situational awareness aid," says CMC commercial aviation marketing manager John Barker. "The image will be displayed on the HDD or any video-capable display such as an electronic flightbag or any cockpit display unit [CDU]. [The sensor] may also be mounted in the tail to give a view of the aircraft, or in the radome. It will be low cost and low weight."
Not far behind is a more sophisticated system encompassing an imaging millimetre-wave (MMW) radar, flight testing of which could start next year. "Our goal is to marry the two [IR and MMW]," adds Barker. CMC is studying a further step in which imagery synthesised from a terrain database could be added to the sensor video.
Max-Viz is developing two systems to address the market: the EVS-1000 for small to medium business aircraft and the EVS-2000 for high-end business jets and air transport applications. The EVS-2000 flown on Boeing's 737 demonstrator is a dual-sensor system using a combination of uncooled short-wave and long-wave IR sensors in the 1.4-1.6µm and 8-14µm ranges, respectively. Both use micro-bolometer technology in which thermal radiation is used to heat the detector elements. The single-band (long-wave) EVS-1000 is aimed mainly at enhancing situational awareness during taxiing and is to be flight tested on a Dassault Falcon. The sensor, which provides a 40¡ horizontal by 30¡ vertical image, will be mounted on the fin cap or radome.
Runway lights
The dual-sensor approach combines the short-wave IR's ability to pick out runway lights with the longer-wave sensor's better weather penetration and terrain imaging. "The 2000 has no difficulty picking up strobe lights," says director of operational requirements Dick Hansen. "On one flight we were following a 737 in to land at night and in bad weather. At 2 miles [3.2km) finals the crew was able to pick it up on the forward-looking infrared. It was really close spacing, but we saw when the aircraft got off the runway and we were able to land."
Although the image is designed to be projected on a HUD, Hansen says a crucial lesson learned from the Boeing demonstrator is the importance of dual-displayed images on the HUD and HDD and their impact on crew co-ordination. "A lot of aircraft without HUDs could take advantage of these additional wavelengths for enhanced situational awareness," he says.
The EVS-2000, a compact system weighing less than 4.5kg, is being flight tested on Max-Viz's Cessna 421 and is expected to be certificated around the end of the year. Max-Viz is not yet ready to say what the first application will be. "We're talking to four or five non-US airlines very seriously. They are taking a hard look at it from a safety perspective," says Hansen. Although certification for Category II approaches to Cat 1-equipped runways was the original target, Max-Viz says initial certification will now be as a flight safety advisory system. Later full-up Cat I/II certification will depend on accumulating landing credit in much the same way as the early HUDs.
Boeing, meanwhile, continues to gather feedback from the BTD exercise, which demonstrated nine key advances over 22 flights to several airworthiness agencies, pilots groups, associations and 87 representatives from 47 airlines. Troy Brekken, Boeing technology analyst, says results will be compiled by July and used to help define the company's strategy for future systems. Boeing is interested in enhancing safety and efficiency. If there's potential and it makes sense to go forward with this technology, we are behind it."
Source: Flight International