Royal Aeronautical Society explores fly-by-wire

Last week the Sydney branch of the Royal Aeronautical Society hosted a panel discussion to explore the fly-by-wire phenomenon.

Around one hundred people heard Virgin Australia’s Captain Rick Howell, V Australia’s Captain Paul Doherty and Qantas’ A380 Technical Pilot Ben Holland talk about their experiences with the Airbus and Boeing technologies.

The discussion was moderated by Captain Ian Watkins.

Amongst the highlights of what was over an hour of fascinating enlightenment were:

* The advantages of FBW include a big overall reduction in weight; a “simpler’aeroplane; superior handling characteristics; ease of maintenance; and flexibility to include new functionality.

* FBW provides the alternatives of either creating a system that’s consistent with the traditional flight deck; or of adopting the full weight of the electronic way of doing things and not have forced feedback, not have moving controls with autopilots, and instead have different methods of monitoring and controlling the aircraft.

* FBW can provide protections which will deter you from doing certain things; or limitations which will prevent you from doing certain things in an aeroplane.

* FBW makes transitioning flight crew much quicker and therefore much less costly. At Virgin Australia one extra day’s training for the whole flight crew costs around A$1 million.

* The sophistication of FBW means that different ‘laws’ can apply within a single phase of operation. For example, just for the takeoff there are currently four laws built in to an A380: the direct law, which means that stick displacement is directly proportional to the elevator displacement (normal); the impulse law, which extends the elevator beyond the normal position matching the stick to provide an instantaneous response; the takeoff rotation rate law, where if you pull the stick back and hold it, the system will provide a rate of rotation associated with that constant stick position; and the tail strike protection law, which stops the nose rising too high. 

* Rick Howell: “The most important part of an Airbus fly by Wire aeroplane is…the table. That’s one of the great advantages of flying an Airbus Fly by Wire aeroplane because there’s not that annoying steering wheel…sitting in front of you, you actually get to act like a pilot and use the table for navigation activities. And it just so happens that if people bring food to you it’s actually a handy place to have it..”

* The Airbus aerodynamicists and the people who write the control laws for the aircraft have worked with the flight test people to determine how the pilot should be able to manage the aeroplane. There are those who argue against FBW saying that it takes the control away from the pilot and hands it to the engineer.  But Rick Howell says, “Having experienced this is in many and various formats over the years, including the flight test acceptance and the demonstration of out of envelope activity with the test pilots, I’d suggest to you that for so many reasons envelope protection is a fabulous thing”.

* The prestigious Flight Safety Foundation has demonstrated that envelope-protected aeroplanes (ie Fly by Wire) have resulted in a step change in hull loss rate, because the loss of control airborne is a much more unlikely event in an envelope-protected aeroplane than in a traditional aircraft. Of course, there have been instances contrary to that, most notably perhaps AF447, but they are definitely the exception.

*  Presenting the perspective from the other side of the philosophical debate, V Australia’s Paul Doherty said that, “With Boeing…  the pilot is the final authority for operation of the aircraft… (and) automation is really a tool… the major difference between the two philosophies in that the Boeing is after that aeroplane pilot relationship, they want the controls and the throttles of all the airliners to be back driven. What that means is where you see the control, that’s what is active. So if you feel that the control is moving to the left the aircraft is going to be banked to the left. If the thrust levers are back at idle, they’re back at idle. If they’re pushed forward the thrust is going up. You have that tactile feel. You are part of the machine, you understand what it’s doing, you have that relationship… “

The RAeS Sydney Branch is to be congratulated on delivering such a quality session. One can only hope that the success of this event spawns further similar discussions.