Honeywell's Enhanced Ground Proximity Warning System has undoubtedly saved many lives. But new enhancements offer to make aviation even safer

If anyone is sleepless in Seattle, it is probably Don Bateman. The tireless chief engineer for Honeywell Flight Safety Systems is usually quite bothered with commercial aviation safety, and the skies are safer as a result.

Bateman is best known as the chief architect of the Enhanced Ground Proximity Warning System (EGPWS), a tool that uses a Honeywell-developed worldwide terrain and obstacle database along with GPS navigation or other inputs to warn pilots both visually and aurally of an impending conflict with the ground. He patented an earlier system, which used a radio altimeter as its core technology, back in 1975.

SAM Unstabilised app

Rather than marking the zenith of Bateman's safety achievement, however, the widespread deployment of EPGWS into the world's aircraft as a controlled flight into terrain countermeasure is turning out to be just the beginning.

With reams of accident data as a guide, Bateman and his team of eight safety engineers are creating a palette of new EGPWS add-on features that he says could drastically reduce commercial aviation crashes. Honeywell estimates that with such interventions, many based on software changes to the EGPWS functionality already available, the industry could prevent the loss of 2,300 lives and $5.5 billion over the next decade, assuming an accident rate similar to the past decade.

Potential loss

Leading the way

By Honeywell's count there are more than 48,000 EGPWS units or computers flying today, not including the more than 2,900 terrain awareness and warning systems made by other manufacturers flying on business or corporate aircraft.

The US Federal Aviation Administration mandated TAWS, the generic name for Bateman's invention, for all US turbine-powered aircraft in 2005. With the possible exception of one accident last year, no aircraft equipped with EGPWS has been involved in a classic CFIT crash since its introduction in 1996. Bateman says the 2006 loss of an Armavia Airbus A320 in the Black Sea was most likely caused by the pilots' spatial disorientation and loss of control, although French authorities prefer to call it a CFIT. EPGWS provided 15s of warning to the pilots, he explains.

Honeywell gave Flight International a glimpse of some of the new developments in the company's Beechcraft C90 King Air at Paine Field in Washington last month. Included were demonstrations of the runway awareness and advisory system (RAAS) a stable approach monitor a wing flap advisory and a barometric altimeter error detection system. Others not demonstrated but in development include a runway traffic advisory system, a cockpit altitude advisory and a tailwind warning for landings. Honeywell is also developing an aircraft and helicopter synthetic vision system that draws a computer generated picture of the landscape outside the cockpit using the information in the EGPWS database. The system is designed to help pilots maintain better situational awareness in low-visibility situations.

Southwest 737 Burbank 
© Mike Meadows / Empics   
A Southwest Airlines 737 overran the runway at Burbank airport, California in March 2000, in part due to an unstabilised approach

RAAS, already certificated by the FAA and now in use at Air France, Alaska Airlines, FedEx Express and Lufthansa, is an EGPWS add-on that provides pilots with aural advisories when approaching or entering a runway, among other options, by creating a "virtual box" around runways using information from a worldwide database of runway information in the EGPWS. On our demonstration flight, RAAS called out "approaching one-six right" as we taxied up to the hold lines for departure on runway 16R at Paine Field.

Honeywell pilot Markus Johnson, director of flight operations, deliberately set the wrong take-off flap position in the King Air to demonstrate the new flap advisory system before take-off. Immediately after the aircraft entered the virtual box and the RAAS advisory sounded, a male voice called out: "Check flaps". Once lined up, RAAS called out: "On runway one-six right", followed again by "check flaps".

The simple intervention, in Bateman's estimation, could have prevented most of the 368 deaths that resulted from three commercial airline accidents related to incorrect flap settings on take-off between 1995 and 2004. Although configuration horn warnings exist to prevent the same problem, the horns generally will not sound until the aircraft is on the runway and power is applied for take-off. Pilots must also interpret the meaning of the particular horn, potentially slowing the response.

Bateman says airlines are particularly interested in the flap alert to help pilots remember to set flaps during winter operations. In cold weather, crews are asked not to set take-off flaps until entering the runway to prevent water and slush from freezing, potentially interfering with the flap retraction after take-off.

Happy landings

Another runway aid will arrive with the roll-out of automatic dependent surveillance - broadcast (ADS-B) infrastructure. Once ADS-B is in place later next decade, Honeywell may offer a runway traffic advisory system that will alert pilots entering the virtual box if the runway is occupied or if an aircraft is on final approach.

Bateman's group has simulated the system using aircraft position data sent over from an on-board traffic alert and collision warning system or a low-cost ADS-B receiver. Honeywell calculates that runway collisions have cost the industry $690 million over the past 10 years, or roughly $3.70 for each departure.

Landing accidents have also been costly. Honeywell estimates there are roughly 25 runway overrun accidents every year by turbine-powered aircraft, resulting in $900 million a year in losses. In 1999, overrun accidents claimed 109 lives and destroyed 10 aircraft. In response, Bateman's group has developed the stabilised approach monitor (SAM) software in the EGPWS. Johnson demonstrated the technology as we approached runway 16R for landing at Paine Field. EGPWS computes the warnings using airport-provided glideslope information and the aircraft's altitude, airspeed and configuration. In this case, Johnson was deliberately too high, too fast and improperly configured on final approach with the landing gear stowed and the flaps only partially deployed.

At roughly 1,100ft (335m) above the runway, the system called out: "Gear, gear" and at 800ft: "Flaps, flaps". Soon after, we heard: "Too fast - too high," meaning the aircraft's approach angle was greater than 5° (3° is typical for an instrument approach) and the speed was more than 20kt (37km/h) above the reference approach speed in the band from 1,000ft to 500ft above the runway.

As the wayward approach continued below 400ft, the system issued its final plea: "Unstable, unstable!" This warning also appeared in text on the multifunction display. Conditions that day did not allow us to see the SAM's tailwind monitor, which will provide an aural alert of a tailwind in the zone between 150ft and 1,000ft above the runway on final approach. A tailwind increases an aircraft's landing distance.

Another simple intervention helps pilots realise that altimeter settings are incorrect - errors that have led to numerous CFIT accidents and incidents. Using the EGPWS as independent source, the altimeter alert that sounded off with "altimeter setting" when Johnson, flying at 3,000ft, deliberately dialled in a too-low setting in his altimeter. Bateman says the ability to incorrectly set or manage pressure altitude is a potential problem even in the latest cockpits, and that there is currently no real-time measure of the "vertical integrity" for satellite-based approaches.

A similar advance could also help with pressurisation problems, highlighted by the Helios Airways Boeing 737-300 accident in Athens, Greece, on 14 August 2005.

In that accident, the aircraft failed to pressurise as it ascended, ultimately killing all 121 on board. Using EGPWS and an independent pressure sensor, Bateman and his team have developed a monitor that will post a visual warning and call out: "Cabin altitude" if the environment inside the aircraft indicates an altitude above the usual pressurisation altitude of roughly 7,000ft. Such an alert would take the uncertainty out of existing warning horns that in the 737-300 relate to cabin altitudes above 10,000ft as well as to incorrect flap or trim settings.

A life's work

Woven through all these efforts is Bateman's driving role as the aviation safety czar of the company, perhaps of the industry. Despite nearing 75, he shows no signs of slowing - checking up on the progress of these latest initiatives by his hand-picked group of technology developers at least every half-hour, they estimate.

Source: Flight International