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Author Topic:   Fly-by-wire
jimh posted 11-10-2013 02:32 PM ET (US)   Profile for jimh   Send Email to jimh  

When modern outboard engines began to use electronic controls to actuate their throttle and shift mechanisms, various writers called these systems "fly-by-wire" systems. The first outboard to have electronic controls was probably the VERADO, and I believe that is where the term was first used. It seems to have become ingrained with many boaters, who continue to use "fly-by-wire" to describe these systems. I have never liked the use of "fly-by-wire" when applied to controls for outboard engines for boats.

The first problem with calling a boat's electronic throttle and shift a fly-by-wire system is that boats do not fly. It made no sense at all to me to talk about their control systems in terms of flight. Second, in the term "fly-by-wire" there is a sense that something more is going on in the controls than just transmission of the operator's input to the actual control function. This is true in the case of some aircraft designs that were used in early stealth war planes. The electronic control system needed to assist the pilot because the aerodynamic qualities of the aircraft were not very good, as they were sacrificed in favor of stealthy RADAR cross section or low heat emission. In an outboard engine, the use of electronic throttle and shift controls is quite a bit less complicated than in a fly-by-wire stealth war plane. That is why I got a laugh when watching a film documentary on the design and building of the Boeing 777 jetliner. In an early segment the chief engineer of the flight control system appears on camera and says:

"Fly-by-wire" is an unfortunate term. Probably "electronic flight control system" is as close as you can come to the real definition. It is simply the idea that we use electrical wires rather than mechanical cables to transfer signals from the front end to the back end of the airplane.

"There's an apprehension anytime you change technology, and particularly when you switch from mechanical, which is visible, to electrical, which is not."

--Jim McWha
777 Chief Engineer, Flight Control
appearing in 21st Century Jet--Making the Boeing 777

Describing why the 777 did not go to the extreme of letting a computer fly the plane, but lets the pilot be in control, he goes on to say, "The biggest disadvantage from a safety point of view is the potential that you haven't thought clearly thought through all the events that may occur and taken enough precaution."

I found this to be quite interesting. Here's an airplane that is generally thought to be a fly-by-wire controlled airplane, and the top engineer of the flight control system says that "fly-by-wire" is an unfortunate term. I have to observe that if "fly-by-wire" is an unfortunate term for a 777's flight control, then it seems rather silly to use that term on an outboard engine control system.

At the present, I believe that modern outboard engines are available from several manufacturers with electronic shift and throttle controls. There stills seems to be apprehension about their use, perhaps a result of the overuse of an "unfortunate" term.

swist posted 11-10-2013 05:23 PM ET (US)     Profile for swist  Send Email to swist     
I also thought it was a silly term with regard to aircraft.

But isn't much of this the usual behavior when adopting new technology? When I worked in high tech, we divided our customers into three pools - (1) "early adopters" - those who wanted the benefits of new technology so much they would risk its growing pains, (2) "average users" want the benefits of new technology but with a near-zero risk of faults, and (3) "not now, not ever" those who don't believe in marching in lockstep with the development of new technology.

I think there are plenty of examples of people from all three groups on this forum. There's nothing wrong with any of those attitudes.

Computers now run cars, airplanes, outboard motors, refrigerators, telephones, and so on. And they get it right close to 100% of the time. Quality control on embedded systems (computers that run bigger pieces of hardware such as cited above) has become a science unto itself because it is so critical to get it right.

But it can definitely be unsettling to turn your life over to a pile of C++ code.

And back to the original topic - "fly by wire" always reminds me of some toy airplane on the end of a wire, or else it reminds me of "fly by the seat of your pants". Neither case is comforting.

jimh posted 11-11-2013 12:23 AM ET (US)     Profile for jimh  Send Email to jimh     
The cited documentary (see above) also mentions another significant reason in aircraft for moving to electronic control systems to replace the usual mechanical controls: the long distance between the actual mechanical surfaces being controlled and the aircraft cockpit. It is much easier to run electrical cables through the aircraft than to run mechanical cables or hydraulic cables. While on small boats the distance between the helm station and the outboard engine is not very great, the use of electrical cables still greatly simplifies the rigging needed to convey the control signals to the engine from the helm.
jimh posted 11-12-2013 11:49 AM ET (US)     Profile for jimh  Send Email to jimh     
Using "fly-by-wire" to describe outboard engine throttle and shift controls is further contradictory because in an aircraft the fly-by-wire controls typically operate flight control surfaces that control the aircraft heading and orientation. In outboard use, remote throttle and shift controls only control engine speed and gear case shifting. I do recall that the latest generation of electronic remote controls may also be able to automatically orient the engine trim position. Such a control would then be more reasonably described by a term other than "electronic throttle and shift". Yamaha has recently introduced an electronic top-mounting remote throttle and shift control that is said to be able to optimize engine trim, which they call Trim Assist:

Trim Assist is a system that automatically adjusts the angle of trim of the engines according to engine revs, ensuring a smooth and comfortable ride without the need to trim the engines manually, although it is possible to adjust the trim manually if required. This means that the boat is always running at its optimal trim settings for any speed.


The very latest generation of joystick controls used with twin (or more) engine outboards that allow for independent steering of the two outboard engines in response to input from a joystick control could reasonably be called "steer-by-wire." These controls override the usual steering wheel input that is applied to both engines equally in order to create independent steering and differential thrust. In such a system we begin to see some control supervision being made by the control system, which suggests that it is much more than just a replacement for mechanical or hydraulic linkages.

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