Razza74
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Are Boeing A/C FBW

Tue Dec 13, 2005 9:21 pm

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
 
Razza74
Topic Author
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Are Boeing A/C FBW

Tue Dec 13, 2005 9:23 pm

To all

I apologise on accidentaly shortening the topic header

Razza74
Ahh the joy of living under a flightpath
 
7LBAC111
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Are Boeing A/C FBW

Tue Dec 13, 2005 9:33 pm

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.
 
raggi
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Are Boeing A/C FBW

Tue Dec 13, 2005 9:35 pm

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


raggi
Stick & Rudder
 
Tod
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Are Boeing A/C FBW

Wed Dec 14, 2005 12:07 am

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]
 
charliecossie
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Are Boeing A/C FBW

Wed Dec 14, 2005 3:16 am

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

Wed Dec 14, 2005 3:53 am

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
 
charliecossie
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Are Boeing A/C FBW

Wed Dec 14, 2005 3:58 am

Quoting Tod (Reply 6):
At least throttles

ROTFL!
 
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Starlionblue
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Are Boeing A/C FBW

Wed Dec 14, 2005 4:15 am

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." - John Ringo
 
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HAWK21M
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Are Boeing A/C FBW

Wed Dec 14, 2005 4:47 am

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
I may not win often, but I damn well never lose!!! ;)
 
Tod
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Are Boeing A/C FBW

Wed Dec 14, 2005 5:49 am

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
 
speedracer1407
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Are Boeing A/C FBW

Wed Dec 14, 2005 11:13 am

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.
 
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Starlionblue
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Are Boeing A/C FBW

Wed Dec 14, 2005 12:17 pm

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." - John Ringo
 
speedracer1407
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Are Boeing A/C FBW

Wed Dec 14, 2005 3:18 pm

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.
 
Tristarsteve
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Are Boeing A/C FBW

Wed Dec 14, 2005 6:09 pm

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.
 
jwenting
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Are Boeing A/C FBW

Wed Dec 14, 2005 8:14 pm

All Boeings are FBW, thick metal wires running from electric motors to hydraulic actuators in most of them  Wink
I wish I were flying
 
HiFi
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Are Boeing A/C FBW

Wed Dec 14, 2005 10:03 pm

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
 
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HAWK21M
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Are Boeing A/C FBW

Wed Dec 14, 2005 10:39 pm

Quoting Tod (Reply 10):

 bigthumbsup 
Thanks.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
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Starlionblue
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Are Boeing A/C FBW

Wed Dec 14, 2005 10:45 pm

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." - John Ringo
 
Klaus
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RE: Are Boeing A/C FBW

Sun Feb 26, 2006 11:42 pm

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.
 
DfwRevolution
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RE: Are Boeing A/C FBW

Mon Feb 27, 2006 1:13 am

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.
 
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Jetlagged
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RE: Are Boeing A/C FBW

Thu Mar 02, 2006 1:54 am

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.
 
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CCA
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RE: Are Boeing A/C FBW

Thu Mar 02, 2006 2:26 am

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)
P1 in A330, A340, A346, B742, B744, B748.
 
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CCA
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RE: Are Boeing A/C FBW

Thu Mar 02, 2006 2:45 am

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.
P1 in A330, A340, A346, B742, B744, B748.
 
Klaus
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RE: Are Boeing A/C FBW

Mon Mar 13, 2006 1:40 am

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...
 
Gr8Circle
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RE: Are Boeing A/C FBW

Fri Mar 17, 2006 2:55 am

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

ALL Airbus aircraft are not FBW...the older A300 and 310 were not....it started with the A320....
 
David L
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RE: Are Boeing A/C FBW

Fri Mar 17, 2006 3:50 am

Quoting Gr8Circle (Reply 25):
ALL Airbus aircraft are not FBW...the older A300 and 310 were not



Quoting Starlionblue (Reply 12):
The A300 and A310 are "traditional",

But thanks for reminding us.  Smile
 
KELPkid
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RE: Are Boeing A/C FBW

Fri Mar 17, 2006 6:31 am

Quoting CCA (Reply 23):
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.

I'll bet a 777 pilot gets a little sloppy on his turns when you stick him back into a GA plane... Big grin
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