Fly-by-Wire: Redefining flight and maintenance

Fly-by-Wire Redefining flight and maintenance By Jim Sparks September 2001 One of my favorite toys as a youngster was a model aircraft equipped with a single-cylinder, air-cooled engine fueled with cigarette lighter fluid. The method of...

Monitoring malfunctions
Comparators look for any discrepancy in the data supplied by the three flight control computers and should any error be found, the source computer will be identified and subsequently isolated from the system, while the two remaining computers continue to fly the aircraft. Likewise, should any of the four Actuator Control Electronics devices malfunction, it too will be automatically isolated and the system can still function even with multiple failures. In addition to observing pilot inputs, the Flight Control Computers also observe data from systems sensing airframe parameters such as airspeed and attitude.
This data is blended with the pilot request and the Flight Control Computers issue the orders for aerodynamic response. More often than not, the commanded action is in line with the pilot’s request; however if the demand from the flight deck exceeds the structural or aerodynamic limitations of the aircraft, the Flight Control Computer will do what is required to keep the aircraft operating within a safe envelope. Boeing, unlike Airbus, has designed a pilot override system so that in the event of extreme situations, the flight crew can initiate excessive commands in an attempt to get the aircraft back into a safe flight regime.

Benefits for maintenance
Obviously, this degree of sophistication will require sensors observing all means of entering pitch, roll and yaw commands as well as devices to measure flight control deflections and range of movement. Imagine the benefit of this technology for maintenance. For example, there will rarely if ever be a requirement to install rigging fixtures for flight controls or control columns as positions are monitored electronically, plus the before mentioned removal of mechanical controlling devices. Even the computer systems are self-monitoring and self-testing so should any malfunction exist, it should be adequately logged into a fault memory and then supplied electronically to appear as a fault message to flight crew and maintenance technicians.
Taken to the next step, fly-by-wire could be made to operate the entire aircraft with little or no human intervention. Taking into account that extraordinary things may occur and with this new technology, new problems might actually be introduced and manufacturers have elected to bank on qualified and experienced pilots to prevent the aircraft from being flown only on electronics, but still want to include sights, sounds and the age-old "seat of the pants" approach to provide continual feedback on how things are going.
As far as we who have made aircraft maintenance our profession and the ones who will be assigned the task to maintain this new technology, a degree of apprehension is often sensed. This is yet another challenge to learn new methods and what may at a distance appear to be more complex technology, in reality may make our jobs simpler.
I still think about my childhood airplane on a tether, but then I see children of today operating radio control models and I think "Wow, where was that when I was growing up?" Then reality settles in and I realize I don’t need the model, I’m dealing with the real thing.

Jim Sparks is Manager of Technical Information Support Services for Dassault Falcon Jet. He is an A&P and an Electrician, who began his aviation career as a technician in General and Business Aviation. Later, he became a Technical Instructor on Falcon aircraft and then a Field Representative.

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