Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Are Boeing A/C FBW  
User currently offlineRazza74 From Australia, joined Mar 2005, 99 posts, RR: 0
Posted (8 years 7 months 3 weeks 2 days 8 hours ago) and read 3225 times:

Just a thought?

Airbus aircraft are all fly by wire, has Boeing taken this philosphy on board with it's range of aircraft, and why no sidestick?

The removal of pulleys and cables would greatly reduce overal weight

This does not need to turn in to an A v's B if possible

Thanks in advance

Razza74


Ahh the joy of living under a flightpath
27 replies: All unread, showing first 25:
 
User currently offlineRazza74 From Australia, joined Mar 2005, 99 posts, RR: 0
Reply 1, posted (8 years 7 months 3 weeks 2 days 8 hours ago) and read 3210 times:

To all

I apologise on accidentaly shortening the topic header

Razza74



Ahh the joy of living under a flightpath
User currently offline7LBAC111 From United Kingdom, joined Jul 2004, 2566 posts, RR: 35
Reply 2, posted (8 years 7 months 3 weeks 2 days 8 hours ago) and read 3168 times:

You'll probably get a better response in Tech Ops ...


Debate is what you put on de hook when you want to catch de fish.
User currently offlineRaggi From Norway, joined Oct 2000, 998 posts, RR: 1
Reply 3, posted (8 years 7 months 3 weeks 2 days 8 hours ago) and read 3158 times:

The 777 is FBW, and the 787 will be. No sidestick though.


raggi



Stick & Rudder
User currently offlineTod From Denmark, joined Aug 2004, 1724 posts, RR: 3
Reply 4, posted (8 years 7 months 3 weeks 2 days 5 hours ago) and read 2989 times:

Some of the pulley and cable controlled systems on 741 - 743 were converted to FBW on the 744.

Tod

[Edited 2005-12-13 16:08:37]

User currently offlineCharliecossie From Germany, joined Oct 2001, 479 posts, RR: 9
Reply 5, posted (8 years 7 months 3 weeks 2 days 2 hours ago) and read 2819 times:

Hi Tod,
Can you tell us all which systems are FBW on the 744?
Your answer will be very interesting.


User currently offlineTod From Denmark, joined Aug 2004, 1724 posts, RR: 3
Reply 6, posted (8 years 7 months 3 weeks 2 days 1 hour ago) and read 2794 times:

Quoting Charliecossie (Reply 5):
Can you tell us all which systems are FBW on the 744?

At least throttles, maybe more.

I learned this the hard way a few years ago. Somewhere about STA920, the side of body shear panels have cutouts for control cables and I was going to modify those panels. I spent days looking for the engineering that installed the cables that went through those cutouts with zero results. Eventually I looked at the control stand installation drawings and surprise surprise, just electrical connectors where you would have expected control cables.

Doh!

Tod


User currently offlineCharliecossie From Germany, joined Oct 2001, 479 posts, RR: 9
Reply 7, posted (8 years 7 months 3 weeks 2 days 1 hour ago) and read 2790 times:

Quoting Tod (Reply 6):
At least throttles

ROTFL!


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17003 posts, RR: 67
Reply 8, posted (8 years 7 months 3 weeks 2 days 1 hour ago) and read 2774 times:

In the end, aircraft manufacturers will build the plane that customers want. Of course, with many customers, you will have to find a good compromise of their demands.

So:
Boeing customers still want a yoke instead of a sidestick, despite the added weight and more complex construction/maintenance.

If the majority of Boeing customers (by value) changed their minds and wanted a sidestick, I'm pretty sure Boeing would sell them a sidestick.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 9, posted (8 years 7 months 3 weeks 2 days 1 hour ago) and read 2757 times:

Quoting Tod (Reply 4):
Some of the pulley and cable controlled systems on 741 - 743 were converted to FBW on the 744.



Quoting Tod (Reply 6):
the side of body shear panels have cutouts for control cables and I was going to modify those panels.

Any Pics.
regds
MEL



Think of the brighter side!
User currently offlineTod From Denmark, joined Aug 2004, 1724 posts, RR: 3
Reply 10, posted (8 years 7 months 3 weeks 2 days ago) and read 2736 times:

Quoting HAWK21M (Reply 9):
Quoting Tod (Reply 6):
the side of body shear panels have cutouts for control cables and I was going to modify those panels.

Any Pics.
regds
MEL

Former SQ 744, STA955 / RBL125



The oval shaped cutout is provisions for two control cables routed to the engines. Of course the left side is the same. The blank brackets just inboard are for pulley supports.


Tod


User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 11, posted (8 years 7 months 3 weeks 1 day 18 hours ago) and read 2646 times:

Quoting Tod (Reply 4):
Some of the pulley and cable controlled systems on 741 - 743 were converted to FBW on the 744.



Quoting Charliecossie (Reply 5):
Can you tell us all which systems are FBW on the 744?



Quoting Tod (Reply 6):
At least throttles, maybe more.



Quoting Charliecossie (Reply 7):
ROTFL!

I think the miscommunication here is that pretty much every modern airliner has FADEC, or digitally controlled throttles. But a FBW plane is quite different, as it employs computers to move all control surfaces based on inputs from a sidestick or yoke that isn't directly connected to servos or cables.

Quoting Razza74 (Thread starter):
Airbus aircraft are all fly by wire, has Boeing taken this philosophy on board with it's range of aircraft, and why no sidestick?

The removal of pulleys and cables would greatly reduce overall weight

Seems like you're equating a traditional yoke in a FBW aircraft with pulleys and cables. If so, well I'm fairly certain there aren't any pulleys or cables in, for example, the FBW 777 or upcoming 787. Starlionblue gives a good explanation why Boeing has opted for a control yoke in its FWB planes above. If you're wondering why existing planes, such as the thoroughly modern 737NG don't have FBW, I've read numerous times on this board that it simply wouldn't have been economical for Boeing to redesign and certify such a substantial upgrade to an already proven design, weight savings or not.



Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17003 posts, RR: 67
Reply 12, posted (8 years 7 months 3 weeks 1 day 17 hours ago) and read 2618 times:

Quoting Speedracer1407 (Reply 11):

I think the miscommunication here is that pretty much every modern airliner has FADEC, or digitally controlled throttles. But a FBW plane is quite different, as it employs computers to move all control surfaces based on inputs from a sidestick or yoke that isn't directly connected to servos or cables.

The other misconception is about the implementation of FBW. The Airbus control systems that take inputs on the controls and "translate" them into a configuration for the surfaces (as opposed to proportional responses) could easily be achieved with mechanical cables instead of electronic linkages. Thus, FBW with "translation" (as on the 318-321, 330/340, 380, Gripen, Typhoon, Rafale) is quite different from the FBW on the 777 and 787. The difference is not in the cables, it's in the software that takes information from the pilots to the surfaces.

Quoting Razza74 (Thread starter):

Airbus aircraft are all fly by wire,

Nope. The A300 and A310 are "traditional", although the A310 has some FBW implemetation, IIRC on the ailerons.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 13, posted (8 years 7 months 3 weeks 1 day 14 hours ago) and read 2582 times:

Quoting Starlionblue (Reply 12):
The Airbus control systems that take inputs on the controls and "translate" them into a configuration for the surfaces (as opposed to proportional responses) could easily be achieved with mechanical cables instead of electronic linkages.

Interesting. But how would a flight control system direct cables and/or hydrolics that "translated" control inputs into unproportional control surface responses without the "intelligence" of computers?

Quoting Starlionblue (Reply 12):
Thus, FBW with "translation" (as on the 318-321, 330/340, 380, Gripen, Typhoon, Rafale) is quite different from the FBW on the 777 and 787. The difference is not in the cables, it's in the software that takes information from the pilots to the surfaces.

Much has been made, recently, of Airbus's FBW philosophy, what with hard limits and all. Several Airbus pilots have contributed, but I can't seem to recall reading posts from any 777 pilots on this forum. I'd love to hear from pilots and/or engineers who are familiar with the day in /out operation of Boeing's FBW philosophy, and how flying such a plane is different from flying either a modern Airbus or a non-FBW boeing.

O



Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineTristarsteve From Sweden, joined Nov 2005, 3983 posts, RR: 34
Reply 14, posted (8 years 7 months 3 weeks 1 day 11 hours ago) and read 2566 times:

Quoting Charliecossie (Reply 5):
Can you tell us all which systems are FBW on the 744?

The reason you havent got a reply yet is no-one can remember, and we all need to look in the book. From memory (I am at home)
The B744 has FBW throttles and flaps.
The A320 has steel cable controlled rudder.
The B777 control columns are connected to sensors and actuators. If the A/P is flying the aircraft the actuators move the control columns and throttles. The B777 has a couple of cable controlled spoilers.

As engineers we work on many different aircraft. I work on B777 B744 B757 B767 A319/20. All have varying degrees of FBW. Even the B757/B767 have FBW spoilers. The B767 has FBW throttles.


User currently offlineJwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 18
Reply 15, posted (8 years 7 months 3 weeks 1 day 9 hours ago) and read 2549 times:

All Boeings are FBW, thick metal wires running from electric motors to hydraulic actuators in most of them  Wink


I wish I were flying
User currently offlineHiFi From Brazil, joined Apr 2005, 192 posts, RR: 0
Reply 16, posted (8 years 7 months 3 weeks 1 day 7 hours ago) and read 2519 times:

Quoting Speedracer1407 (Reply 11):
If you're wondering why existing planes, such as the thoroughly modern 737NG don't have FBW, I've read numerous times on this board that it simply wouldn't have been economical for Boeing to redesign and certify such a substantial upgrade to an already proven design, weight savings or not.

Another reason is that the weight issue for aircraft the size of a 737 is questionnable... a FBW control system means a LOT of wire...  Wink




As to "direct control" versus "translated inputs", a FBW aircraft can have both, with a yoke or with a sidestick.

FBW only means that there aren't any mechanical linkages (cables, pulleys, rods, ...) and that the control device (yoke/column or sidestick) is monitored by position sensors that send the position information through wires to the actuators for them to respond accordingly. It does not assume that a computer applies control laws. The system can be analog or digital. Digital is easier if you want to put a computer in the loop enhancing or modulating pilot commands.

When a computer is in the loop, it gives the pilot the opportunity of commanding the aircraft by inputing an attitude, instead of a surface deflection. When pulling on the sidestick or column, the aircraft interprets it as "give me a 5º positive pitch" and commands the surfaces in order to achieve and maintain a 5º pitch attitude. When directly controlling the surfaces, by pulling on the column or sidestick, the pilot will command the elevators proportionally and the resulting pitch angle will depend on aircraft speed and AOA. The pilot will have to trim the aircraft in order to maintain the 5º pitch attitude.

FBW also gives you the choice of using force feedback or not, whether you use a yoke or a sidestick.

I don't know the 777 and 787 well enough to say if their s/w "translates" pilot inputs, but I believe it does. Do we have any 777 pilots here? When pulling on the column, do you command pitch or elevator deflection? The huge difference between Airbus and Boeing philosophies is envelope protection (BOTH use envelope protection), but that's a whole different discussion!  box 



no commercial potential
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 17, posted (8 years 7 months 3 weeks 1 day 7 hours ago) and read 2509 times:

Quoting Tod (Reply 10):

 bigthumbsup 
Thanks.
regds
MEL



Think of the brighter side!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17003 posts, RR: 67
Reply 18, posted (8 years 7 months 3 weeks 1 day 7 hours ago) and read 2508 times:

Quoting Speedracer1407 (Reply 13):
Quoting Starlionblue (Reply 12):
The Airbus control systems that take inputs on the controls and "translate" them into a configuration for the surfaces (as opposed to proportional responses) could easily be achieved with mechanical cables instead of electronic linkages.

Interesting. But how would a flight control system direct cables and/or hydrolics that "translated" control inputs into unproportional control surface responses without the "intelligence" of computers?

You would still need computers. They would be driving servos that drove mechanical cables that drove surfaces.

Quoting HiFi (Reply 16):
As to "direct control" versus "translated inputs", a FBW aircraft can have both, with a yoke or with a sidestick.

Indeed, and if a FBW Airbus reverts down from normal law do direct law yo upretty much get "direct control", that is proportional.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKlaus From Germany, joined Jul 2001, 21418 posts, RR: 54
Reply 19, posted (8 years 5 months 1 week 1 day 6 hours ago) and read 2253 times:

Quoting HiFi (Reply 16):
Another reason is that the weight issue for aircraft the size of a 737 is questionnable... a FBW control system means a LOT of wire...

Not necessarily. At least the A380 (and probably the 787) has a modified ethernet networking system, which uses packetized information flow. A single cable can accomodate multiple signal flows simultaneously, and intelligent routers can automatically circumvent faulty cables if required. This way you can both save weight and increase redundancy and safety at the same time.


User currently offlineDfwRevolution From United States of America, joined Jan 2010, 962 posts, RR: 51
Reply 20, posted (8 years 5 months 1 week 1 day 4 hours ago) and read 2238 times:

Quoting Klaus (Reply 19):
Not necessarily. At least the A380 (and probably the 787) has a modified ethernet networking system, which uses packetized information flow. This way you can both save weight and increase redundancy and safety at the same time.

In the case of the 737NG, it really doesn't matter. The 737NG is lighter than its respective A320 counterparts, so there was little reason for Boeing to shell out millions of dollars when there is little value to be gained.

It doesn't always make sense to implement technology just for the sake of technology.


User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 24
Reply 21, posted (8 years 5 months 5 days 3 hours ago) and read 2072 times:

Quoting Klaus (Reply 19):
At least the A380 (and probably the 787) has a modified ethernet networking system, which uses packetized information flow. A single cable can accomodate multiple signal flows simultaneously, and intelligent routers can automatically circumvent faulty cables if required.

ARINC 429 buses have carried multiplexed digital flight control signals, in the form of digital words with a label and direction indicator (SDI) for many years (in one direction and without intelligent routing of course). The 777 introduced ARINC 629 which allows bi-directional databuses.

An ARINC 429 word is not really a packet in ethernet terms but it is a self contained packet of information (including data, status, label number, SDI, parity, etc) which only the addressed equipment will read, other equipment on the bus ignores it.

The wires used are shielded twisted pairs, very light compared to control cables. Early analogue FBW (e.g. Concorde) did require heavier gauge wires but data could still be mechanicaly multiplexed.

I think the main reason Boeing didn't put FBW on the 737NG was that the aircraft would have had to be re-certified at great cost, for no real gain. FBW technology is only any benefit if applied from original design.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineCCA From Hong Kong, joined Oct 2002, 830 posts, RR: 14
Reply 22, posted (8 years 5 months 5 days 3 hours ago) and read 2058 times:

Quoting Jwenting (Reply 15):
All Boeings are FBW, thick metal wires running from electric motors to hydraulic actuators in most of them

For the 747 there are no electric motors involved unless using an alternate system for the LE flaps, TE flaps & Landing Gear.

The -400 had the following cables removed and replaced by an electrical (FBW) system.

Flap lever to flap control module.
Manual stab trim levers to stab control module.
Rudder trim to rudder trim unit.

Thrust levers to engines (FADEC)



C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineCCA From Hong Kong, joined Oct 2002, 830 posts, RR: 14
Reply 23, posted (8 years 5 months 5 days 3 hours ago) and read 2053 times:

777 FBW

The actuator control electronics (ACEs) receive input signals from all pilot controls. In the normal mode during manual flight, the ACEs receive pilot control inputs and send these signals to the three Primary Flight Computers (PFCs). The PFCs verify these signals and information from other airplane systems in order to compute control surface commands. These commands are then sent back to the ACEs. The ACEs send enhanced signals to the flight control surface actuators.

Flight Envelope Protection

The flight envelope protection system reduces the possibility of inadvertently exceeding the airplane's flight envelope. The flight envelope protection system provides crew awareness of envelope margins through tactile, aural, and visual cues. The protection functions do not reduce pilot control authority.

Normal Mode Pitch Control

In the normal mode, airplane pitch control characteristics are like conventional airplanes, with improved handling qualities. Unlike conventional airplanes, the control column does not directly position the elevator in flight. The control column commands the PFCs to generate a pitch maneuver. The PFCs automatically position the elevator and the stabilizer to generate the commanded maneuver. The PFCs constantly monitor airplane response to pilot commands and reposition the elevator and stabilizer to carry out these commands. Airplane pitch responses to thrust changes, gear configuration changes, and turbulence are automatically minimized by PFC control surface commands.

The PFCs also provide compensation for flap and speedbrake configuration changes, and turns up to 30° of bank. The PFCs automatically control pitch to maintain a relatively constant flight path. This eliminates the need for the pilot to make control column inputs to compensate for these factors. For turns up to 30° of bank, the pilot does not need to add additional column back pressure to maintain altitude. For turns of more than 30° of bank, the pilot does need to add column back pressure. As airspeed changes, the PFCs provide conventional pitch control characteristics by requiring the pilot to make control column inputs or trim changes to maintain a constant flight path.

Elevator Variable Feel

The PFCs calculate feel commands based on airspeed. In general, control column forces increase:
• as airspeed increases for a given column displacement, or
• as column displacement increases.



C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineKlaus From Germany, joined Jul 2001, 21418 posts, RR: 54
Reply 24, posted (8 years 4 months 3 weeks 3 days 4 hours ago) and read 1877 times:

Quoting Jetlagged (Reply 21):
An ARINC 429 word is not really a packet in ethernet terms but it is a self contained packet of information (including data, status, label number, SDI, parity, etc) which only the addressed equipment will read, other equipment on the bus ignores it.

That is pretty much exactly how every serial bus communication works, including ethernet...


25 Gr8Circle : ALL Airbus aircraft are not FBW...the older A300 and 310 were not....it started with the A320....
26 Post contains images David L : But thanks for reminding us.
27 Post contains images KELPkid : I'll bet a 777 pilot gets a little sloppy on his turns when you stick him back into a GA plane...
Top Of Page
Forum Index

Reply To This Topic Are Boeing A/C FBW
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Why Are Boeing Planes Lighter Than Airbus Planes? posted Sun Sep 18 2005 17:40:22 by A380900
What A/c Are FBW? posted Sat Feb 21 2004 13:46:10 by Dexter
Airbus FBW More "advanced" Than Boeing's? posted Tue Feb 25 2003 20:40:46 by Mhsieh
Airbus And Boeing Throttle Controls posted Tue Dec 5 2006 15:30:41 by Treeny
Structural Seminar - Boeing posted Thu Nov 9 2006 13:41:45 by HAWK21M
Boeing 737 Minimum Take-off/Landing Requirements posted Fri Nov 3 2006 16:22:57 by NZ8800
What Are These Intakes For On The 777? posted Wed Nov 1 2006 04:13:28 by Gh123
What Pressure Are Aicraft Pressurised At? posted Thu Oct 19 2006 01:20:07 by RootsAir
Boeing 747-400BCF posted Sun Oct 15 2006 13:43:57 by Qantas744ER
How Do Boeing/Airbus Conduct Pressurization Tests? posted Fri Oct 13 2006 08:02:04 by Brenintw

Sponsor Message:
Printer friendly format