THE feat of two heroic pilots who saved 185 lives when they crash-landed a
crippled airliner has inspired the development of a new computer-controlled
safety system that could one day allow damaged airliners to land themselves.
In 1989, hydraulic failure left a United Airlines DC-10 with nothing but two
of its engines to control steering and altitude. The plane crash-landed at Sioux
City airport in Iowa, killing 111 people. But aviation safety experts say 185
other passengers would have perished if it weren鈥檛 for the pilots鈥� clever use of
the engine throttles to guide the plane.
Impressed by the pilots鈥� skills, aerospace engineers at the Georgia Institute
of Technology, NASA and Boeing have developed a system that will let the
autopilot fly and land the plane using only engine power. 鈥淚t can even cope with
damage to the airframe or part of its wing shot off,鈥� says aerospace engineer
Anthony Calise at Georgia Tech.
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The system is designed to detect any damage to either the engines or any of a
plane鈥檚 flight control surfaces, and instantly adjust the remaining control
surfaces or power resources to compensate.
Their system has already been successfully tested on an F-15 fighter and an
MD-11 passenger jet. In both cases the planes landed without human assistance
using power-only control (POC), says NASA researcher John Kaneshige. It has also
been tested in simulators of a variety of other aircraft, including Boeing 747s
and the X36, a prototype space shuttle replacement.
But POC is limited in that it doesn鈥檛 make use of any parts of control
surfaces that might still function. So it is now being combined with an adaptive
neural network developed by Calise. The resulting system, with the unwieldy name
of the Integrated Neural Flight and Propulsion Control System (INFPCS), should
be capable of responding to 鈥渟ingle failures or multiple failures, all the way
down to full loss of control surfaces on the 747,鈥� says Calise.
Other neural networks have been developed in the past to do a similar job,
but these require offline 鈥渢raining鈥� and take up to four seconds before the
neural network reconfigures the plane and compensates for the damage
(快猫短视频, 24 April 1999, p 5).
Calise鈥檚 neural network has been designed
to react within a few tenths of a second, fast enough for the reconfiguration to
go unnoticed by the pilots flying the aircraft鈥攁nd far faster than a
person could react.
Rather than constantly scanning for failures or damage to the plane, the
INFPCS compares what the pilot is doing with the aircraft鈥檚 behaviour. If they
don鈥檛 match, it assumes a failure has occurred and attempts to compensate. 鈥淚t
uses a desired handling module,鈥� says Kaneshige. 鈥淚f it鈥檚 not behaving in a
particular way [the INFPCS] modifies it.鈥�
But the development of INFPCS raises a disturbing question. 鈥淚f you don鈥檛
need to have a pilot trying to make these desperately difficult manoeuvres, then
why have a pilot at all?鈥� asks Tom Anderson of the Centre for Software
Reliability at the University of Newcastle upon Tyne.
But don鈥檛 expect your next holiday flight to be equipped with an INFPCS
system, warns Kaneshige. 鈥淚t鈥檚 still to be determined whether this is a
passenger-carrying technology.鈥�