Fly-by-wire for light aircraft ?
FADECs and glass-cockpits have made their way from military and commercial aircraft market down to the light aircraft market. Will FADEC lead to auto-throttles ? Will glass-cockpit lead to head-up displays ? I think so. These are natural developments which will help to reduce pilot workload and improve safety. When this will be done the last important difference will be the absence of fly-by-wire systems for light aircraft.
In a classical aircraft the controls in the cockpit are mechanically linked to the control surfaces like the ailerons and elevator. In large aircrafts an hydraulic system supports the pilot, just like power-assisted steering in cars. In “fly-by-wire” aircraft the control column is directly linked to a computer. The computer interprets the inputs from the pilot and in turn actuates the control surfaces. The interpretation step has always been subject to debate, particularly since Airbus introduced this technology on the Airbus 320 family. Different “control laws” are used depending the phase of flight and in certain modes the computer protects the plane and does not follow blindly what the pilot tries to do. My conviction is that it is perfectly safe as long as the pilots are properly trained and have a good understanding of the system – but this is not the topic of this post.
One of the advantages of the “fly-by-wire” system it’s relative simple mechanical aspect. It’s much easier to transport digital data to the actuators than it is to have a direct mechanical link. It also saves weight and having a computer in the loop has many advantages. If you hate me before of the last point, feel free to express yourself in comments.
Will the fly-by-wire technology once reach the light aircraft market ? Light aircraft have direct controls because the force required to actuate the control surfaces are not large enough do not require an hydraulic system. This is not a really a no-go for a fly-by-wire system. Autopilot systems on light aircraft use servo actuators which are accurate enough to fly an ILS approach more accurately than a human pilot. What Garmin and Cirrus developped with the “attitude recovery” button is one more step towards flight automation. I’m not sure it would take a lot of effort to replace the control column by any USB joystick and send the information to the flight-director and auto-pilot systems. Some force-feedback could be helpful but this should not be too complex to implement. The technology used in certified simulators like FNPT-II is more than realistic…
Could a “fly-by-wire” system for light aircraft save lives, in example by avoiding inadvertent stall / spin when pilots fly their base turn with too much bank and not enough speed ? What do you think about it ?
6 Comments, Comment or Ping
Axel
Hey Vincent,
With the developments that we have already seen in light aircraft regarding FADECs, glass etc. these new steps really don’t seem all that far fetched! 
That sure is an exciting future for general aviation and light aircraft you are describing.
I am completing my end-of-course checkride for the Instrument rating tomorrow, so hopefully by this time tomorrow I’ll be an instrument rated pilot!
I did most of my training for the instrument rating on the G1000 with the GFC700 autopilot/flight director. That sure is one neat autopilot! I was all excited to discover a new feature on the GFC700 called FLC (flight level change). This new feature controls constant airspeed climbs and descents. All you need to do is to adjust the power and the autopilot will control the rate of climb/descent to maintain a constant airspeed. I can only predict that this feature is one of the first few baby steps towards a future implementation of auto throttle in systems like the G1000.
Hope everything is going well for you and that you enjoy studying the DA42. When do you plan on starting with the flying lessons?
Regards,
Axel
Mar 5th, 2009
Vincent
Hi Axel,
I already heard about the flich (FLC) but never had the opportunity to fly with it. The DA42 I’ll fly here is equipped with a KAP140, so no flight director. To answer your question I’ll start my training begin of April, and the plan is 8 hours of FNPT-II and 5 of actual flight.
Let me know about tomorrow.
Vincent
Mar 5th, 2009
Axel
Hey Vincent,
Because the check pilot got sick the checkride was postponed a bit, but now it is all done.
Then I have joined the club of instrument rated pilots!
Now it is back to flying VFR working on my commercial certificate. Probably in just a week or two I’ll be flying solo from Daytona Beach to Key West and back. That is more than 7 hours in the air flying past Kennedy Space Center and Miami Beach as well as the entire Florida keys….and I get to use the G1000 with the GFC700 autopilot for the flight! That sure is gonna be fun! I’ll bring my camera and try to take plenty of pictures. Since I no longer have a blog/website of my own, maybe you’ll want to use them…
Good luck further on with the DA42 training. I am looking forward to hearing more about that!
Axel
Mar 12th, 2009
Vincent
Congrats Axel ! What a great day for you. Welcome in the club.
Mar 12th, 2009
Russ Kotlarek
The reality is FBW already exsist in some Experimental Light aircraft. I am in the middle of designing my system for a Mazda Rotary in my Experimental. Technology although not flawless has offered much int he way of advancement that is not being taken advantage of do to cost restrictions of certification. A real problem but a necessary one to some degree.
For instance FBW with the advancements in say the Mazda engine I can achieve 320HP from an engine with accessories and such that is well over 200 lbs lighter than an IO-540 at 300HP. The cowl size facial area is less than half the area. Bottom line technology has offered up these wonderful advantages. After all who cannot appreciate a plane that is 10% lighter, and faster all in the same basic design?
Can FBW fail? absolutly ! but form someone who has had a cable failure in his throttle rest assure the mechanical failure is also real. The design in an aircraft that is Fly by Wire should differ greatly from a DBW Drive by Wire in a car. For instance DBW throttle upon most failures mechanically fades back to idle. Not what I desire in an aircraft! I would prefer fat failure the engine mechanically go to full power or hold at the current power setting knowing I can always cut fuel and kill the engine when I see fit to make a safe landing.
Imagine at 300 ft if the system fails and it rolls back to idle …. Yikes not healthy. But if it stayed at the current setting (Full) or was spring loaded the other way to go to full power I’m likely to live through it. Sure on the ground a failure to full power may take me into a hangar but assuming I am quick enough to kill fuel I can likely prevent that as well. or even if I can’t I’m thinking I have a better chance of living through a hangar strike at 30 than a forced landing at 80 and into trees.
FBW … it is here ask the Experimental’s they will be happy to share the hours of success, in which I trust I will be one in the near future.
Jan 20th, 2010
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