Is there a difference between fly by wire on a 777 and on an Airbus??...

[UALdave]

Boeing criticizes the usage of fly-by-wire by Airbus, but the 777 family uses fly-by-wire. Are the folks at Boeing just being hypocrites, or is there a difference? For example, can you turn it off and hand-fly a 777 easier??

[cegro27]

Boeing's criticism has more to do with the level of control authority the pilots have. In Airbus jets, the FBW system has full control authority, preventing the pilots from making any control inputs that would put the aircraft outside its normal flight-envelope, however there is a mechanical and/or electrical backup if there is a failure of the FBW system.

Boeing's 777 FBW system is not full authority, so the pilots have the ability to fly the aircraft outside it's normal flight-envelope, as well as there being a mechanical backup in case of FBW failure.

Other than that, Boeing hasn't been (and still isn't) a big fan of sidestick/joystick flight controllers, preferring the more conventional yoke and column cockpit controls, believing that sidestick controls don't give pilots enough 'realistic' feedback of aircraft control.

[3WE]

WOW...only one other reply.

[UALdave]

Boeing's criticism has more to do with the level of control authority the pilots have. In Airbus jets, the FBW system has full control authority, preventing the pilots from making any control inputs that would put the aircraft outside its normal flight-envelope, however there is a mechanical and/or electrical backup if there is a failure of the FBW system.

Boeing's 777 FBW system is not full authority, so the pilots have the ability to fly the aircraft outside it's normal flight-envelope, as well as there being a mechanical backup in case of FBW failure.

Other than that, Boeing hasn't been (and still isn't) a big fan of sidestick/joystick flight controllers, preferring the more conventional yoke and column cockpit controls, believing that sidestick controls don't give pilots enough 'realistic' feedback of aircraft control.

Thanks so much for the reply with all that info that I wasn't aware of! It's always cool, as an aviation fanatic, to learn more about aircraft systems!

BTW, I was reading about the TU-204 aircraft, and the book mentioned that it has a "triplex" FBW system? What does the author mean by triplex? That there are 3 levels of redundancy, or is it something different.

[cegro27]

Yes, three levels of redundancy...three separate channels (or signals) being sent to the controlling computer. The signals are measured for accuracy before being sent to the actual flight control to be moved (aileron, elevator, rudder, trim tabs...). If any one channel (or channels) is deemed faulty, that channel is locked out of the control process...the remaining channel(s) takes over in order to maintain flight control function. There may even be an independent backup FBW computer (depending on the aircraft make and model), although as I said before, both Airbus and Boeing use some sort of mechanical or electrical backup flight control system.

[UALdave]

Yes, three levels of redundancy...three separate channels (or signals) being sent to the controlling computer. The signals are measured for accuracy before being sent to the actual flight control to be moved (aileron, elevator, rudder, trim tabs...). If any one channel (or channels) is deemed faulty, that channel is locked out of the control process...the remaining channel(s) takes over in order to maintain flight control function. There may even be an independent backup FBW computer (depending on the aircraft make and model), although as I said before, both Airbus and Boeing use some sort of mechanical or electrical backup flight control system.

Gotcha! At close to 7:00 in this video: http://www.youtube.com/watch?v=6kn7sH2TLvQ there is an interesting look at the cables on the MD-11, which is not fly-by-wire. The cables don't look that thick! But they are probably made out of steel, or something like that.

So, who makes the computers that are on board all commercial aircraft, fly-by-wire, or otherwise? Companies like IBM??

[B757300]

Gotcha! At close to 7:00 in this video: http://www.youtube.com/watch?v=6kn7sH2TLvQ there is an interesting look at the cables on the MD-11, which is not fly-by-wire. The cables don't look that thick! But they are probably made out of steel, or something like that.

So, who makes the computers that are on board all commercial aircraft, fly-by-wire, or otherwise? Companies like IBM??

If Boeing and Airbus follow the usual standards of redundancy, each computer comes from a different manufacturer and is built with different components so as to avoid a design/manufacturing defect from affecting all the computers at the same time.

[Gabriel]

Gotcha! At close to 7:00 in this video: http://www.youtube.com/watch?v=6kn7sH2TLvQ there is an interesting look at the cables on the MD-11, which is not fly-by-wire. The cables don't look that thick! But they are probably made out of steel, or something like that.

These cables don't move the flight contol surfaces directly. Instead, they move the hydraulic valves that control the flow of hydraulic fluid into the hydraulic actuators which, now yes, move the flight control surfaces.

That's why they are so thin. It's lighter and less expensive to take a cable from the cockpit to the tail than a hydraulic line from the engine to the cockpit and back to the tail.

[UALdave]

These cables don't move the flight contol surfaces directly. Instead, they move the hydraulic valves that control the flow of hydraulic fluid into the hydraulic actuators which, now yes, move the flight control surfaces.

That's why they are so thin. It's lighter and less expensive to take a cable from the cockpit to the tail than a hydraulic line from the engine to the cockpit and back to the tail.

OK, interesting! Now, here's a Cessna aircraft that uses a side stick, and rods instead of cables or fly by wire: http://www.youtube.com/watch?v=0SFi7..._order&list=UL That looks and sounds pretty unique, IMO.

[UALdave]

So what about the 787-is it "completely" fly-by-wire, or is it the same as the 777??