Controlled flight into terrain could be virtually eliminated as a mishap category for US Air Force fighters by loading a new set of algorithms into the flight computer.
Two months ago, the Air Combat Command erred when responding to a query about the status of the decade-old automatic ground collision avoidance system (auto-GCAS). The technology has not been shelved, as was said at the time.
To the contrary, the USAF has finally approved funding to install the system on Lockheed Martin F-16 Block 40s and above and has programmed to insert auto-GCAS for Lockheed F-22 Increment 3.2 fighters and future F-35s, says Mark "Tex" Wilkins, a retired USAF colonel now working as senior aviation safety analyst for the defence safety oversight council.
Auto-GCAS is a software application that keeps track of the aircraft's position, speed and altitude against a digital terrain map of the Earth.
The system intervenes if the pilot becomes disoriented, or suffers a g-induced loss of consciousness (G-LOC). A warning is issued 5s before the flight computer takes control of the aircraft.
If the pilot fails to react to the warning within 1.5s of approaching a point of no return, the auto-GCAS system takes control of the aircraft. It rolls the aircraft violently to a wings-level orientation and then initiates a 5g pull-up. The computer gives control back to the pilot after it restores the aircraft's stability.
The algorithms are also designed to keep from interfering with the pilot's mission, Wilkins says. A particular concern is high-angle strafing attacks. Pilots do not want the computer to take control at the wrong time.
For each mission, the system allows the pilot to set a minimum distance over terrain that will be flown, Wilkins says. The system does not become engaged unless the system pilot flies beneath that altitude.
If the system were installed across the fleet today, it would have saved the life of Capt George Bryan Houghton, who died on 22 June after losing track of his altitude, Wilkins says.
According to the USAF mishap report, Houghton was practising high-angle strafing attacks at night in the F-16, an aircraft relatively new to his experience. The report concluded that Houghton focused too intently on the laser spot illuminating his target as he began to dive. Houghton failed to respond to any of three different cockpit alert systems - and urgent calls by a ground controller - telling him to "pull up".
In addition, flight-test activity should not pose problems for auto-GCAS, Wilkins says, citing the fatal F-22 accident in March involving Lockheed test pilot David Cooley. He was performing a high-g manoeuvre to collect a test point, but briefly suffered a condition known as "almost g-induced loss of conciousness", according to the USAF mishap report. By the time he regained awareness, the F-22 was in an unrecoverable position, diving through 14,000ft (4,267m) at Mach 1.6.
In this, auto-GCAS would not have interfered while Cooley performed the high-g manoeuvre, Wilkins says. "Auto-GCAS was fine with that," he says. "But when he pulled the nose down there, and hit somewhere around 70° nose-low, that's when auto-GCAS kicks in."
Developed over the past 25 years between NASA, the Air Force Research Laboratory and Lockheed Martin's Skunk Works, auto-GCAS will finally be deployed on F-16 Block 40s and above after 2012,
The upgrade is included in the 6.2 block upgrade for the F-16 operational flight programme, Wilkins says. The USAF also plans to integrate auto-GCAS in the F-22 Block 3.2 software upgrade, which is scheduled to be deployed in 2016. The USAF's Lockheed F-35 Joint Strike Fighter fleet also will receive the safety application, Wilkins says.
The system is integrated differently depending on the aircraft type. For the F-16, the software is managed through the avionics system, Wilkins says. The F-22 programme has decided to run the application through the flight-control computer, he says.
The USAF and NASA first demonstrated auto-GCAS in 1998, but the idea has been in development for decades.
"They've been tinkering with this technology since the mid-1980s," Wilkins says.
Even after the 1998 demonstration, the Skunk Works-built software system had a few bugs, but the flights proved the idea was feasible, Wilkins says.
The system has faced resistance from pilots over concerns about turning over control of the aircraft to the flight computer. But the USAF has also been pushing to reduce mishap rates, particularly as the tactical aircraft is projected to dwindle over the next decades.
Source: Flight International
