Fly-by-Wire advantages above conventional

[Austin_Powers]

Hi all,

I am looking for material to point out the advantages of fly-by-wire A/C above conventional ones. When I did my training in Airbus I saw a little booklet with all the major advantages and nice pictures, but unfortunately I don't posess a copy of it. If anybody can help me with material - preferably electronically as an attachment - about this topic, I would really appreciate, because I have to prepere a lecture and I am also quite busy with flying.

Many thanks!

PLS mail to: [email protected]

[atomic]

Oh, Oh !!!! Somebody just opened old Pandora's Box......!!!!!
Let's hear it from the Boeing guys!!!!

[WOK]

ADVANTAGES:

Cheaper to design your big a/c, owing to much simplified control runs.

Enables you to add in lots of clever devices to make it "easier" to fly.

DISADVANTAGES:

Enables whizzkid designers to add lots of devices to make a/c "easier" to fly.


The foregoing applies to both Boeing and Airbus......so no controvesy there, then.

[Brenoch]

The advantage of the Airbus fly by wire is that you´ll hit the mountain exactly on the numbers spot on whereas in a Boeing you´ll actually fly the aircraft outside it´s intended flight envelope but miss the mountain.. :)

[This message has been edited by Brenoch (edited 01 November 2000).]

[atomic]

See, that's exactly what I mean, this is exactly at the heart of the discussion: Does the FBW restrict me in getting the maximum performance (including max engine performance through 'thrust-by-wire')or does it enable me to get optimum performance by going immediately to the max AOA and/or max load factor instead of fiddling with the pitch?? My 10 cents: If you pull the stick way back on the bus, it gives you an immediate pitch up at 2.5g (if clean or slats only) , and when it enters the low speed regime, it directly controls AOA to the max allowed, sounds very optimized to me!
On a conventional plane, you can pull more, but will the pilot do so??!! Aren't we all trained to 'fear' , to 'honor the stickshaker, which, when activated, doesn't have the plane at the max allowable/optimum AOA??!! Yes, the plane can probably take a bit more than the g limits published in the book, but who will , consistently throughout the maneuver, pull those g in a terrain avoidance situation?? So, yes, the 737 might be able to outperform the A320 by exceeding the limits sucessfully, but what if you fly along and suddenly the GPWS starts yelling at you?? On the bus, I just yank the stick all the way back and thrust to max, can you follow the same path in your 737 ??? OK, Boeing guys, into the ring !!!!!!

[WOK]

Ah, another rerun of the Boeing/Airbus debate.......

The points about optimised max energy recovery made above are true, but a red herring. I can't think of any failed CFIT recoveries which would have been helped by FBW (no doubt will be proved wrong).

The real safety issue is that of accidents caused by mode confusion or lack of understanding of the system limitations, of which the FBW Airbus have suffered several. The fact is that FBW allows a much bigger range of subtle and just plain different modes whether in coupled or 'manual' flight.
i.e. as we all know these a/c are just plain different.

This in itself should not be a problem so long as ADEQUATE TRAINING IS GIVEN to relearn some of the fundamentals which are changed. Some of the FBW accidents suggest that this was not the case. Of course, if you're selling these machines you don't want to suggest they require more training so it is left to the responsible operators to recognise the fact.

Just my two penn'orth.


PS I've not flown any Airbus, and admit to not particularly wishing to. I still think, though, that the foregoing is fair comment. :)

[alosaurus]

Wok-Re your original posting it cost Airbus a fortune to design the A320.One reason an A320 s initial cost is so much higher than a 737 is that Airbus have to put on $1Million to recover their FBW costs.Another is that the build quality of an Airbus is much higher.The primary advantage is weight of electrical looms vs conventional control cables.The life cycle cost of an A320 is massively less than a 737 partly as a result of of reduced fuel burn/flying control maintenance costs.
The weight saving is significantly easier to justify on an A330/340 but you have to remember where Airbus were when the A320 was conceived twenty years ago.They had sold less than 400 A300/310s and had to leapfrog Boeing/MacDac with a step change in operating costs.If Airbus is to displace the 747,at the top end of the market,a similar significnt improvement to operating costs will be essential.

[atomic]

Wise words there, WOK !

[Saint-Ex]

The main advantage of the Airbus FBW system is speed of action. As soon as the GPWS goes off you pull full back on the stick to 2.5g and get optimum AOA. Try that on any Boeing, Brenoch, and see where you end up.

[52049er]

Only speaking from memory, but wasnt there a 757 cfit in S America where a manouevre to the limits of the envelope would have meant them missing the terrain?

As for the ol' bus vs boeing debate - all the engineers ive spoken too are much more impressed with the Airbus build quality/quality of materials than with Boeing. Apocraphol (sp? :) ) stories over heavy landings seem to bear this out. As far as the actual flight laws, well they aint perfect but they are pretty good. As with all these things, training is all!!

I still think Boeing misseed a trick with the 777. Why have a bloody great yoke if it's only attached to electronic sensors?

Yours in entirely unbiased Airbus love

52

[SID the STAR]

that bloody great yoke on that bloody great b777 bothers you does it? i bet you would give your left ball to fly that beast!

[WOK]

WRT the above posting - the S American 757 incident was at Cali. They were not far below the top of the peak which they sadly hit, but FBW wouldn't have made enough difference (esp with spoilers out).

Before I start sounding too prejudiced I should point out that I do fly a FBW machine - just not an Airbus.

[Diesel8]

Not sure about the Boeing, but the Airbus will automatically retract the spoilers at Alpha protection. maybe the bus could have made it.

Why they have not made it ToGa power yet is beyond me, heard a software fix was about to happen.

[This message has been edited by Diesel8 (edited 01 November 2000).]

[manuel ortiz]

If my memory serves right our A 320´s will auto retract spoilers once almost max AOA is reached ( Alpha Prot. )
Our 319´s will do it as soon as TOGA is reached.

There are a few things which I personally don´t like abaut this FBW system but after almost 30 years in non fly by wire and just a couple in the Airbus I would rader be on this one for a windshear and most likelly also for a GPWS .
The G limitation is in my humble opinion not that important in probabbly 95% of this two cases , it´s more of an immediate action . Full aft stick providing a 2.5 G´s pull up and then knowing that Alpha max. will be kept when stick held full aft will hopefully promote pilots to expedite the escape maneuver.
( Don´t be picky abaut the difference between one vrs. the other procedure :)

Would I have liked to have some sort of an override option for the G protection ?

Yes I would , most likelly used in a differen scenario.

Manuel


[This message has been edited by manuel ortiz (edited 02 November 2000).]

[Brenoch]

Well, that is the neat thing with the Boeing´s.. You have the option of survival.. :)

[manuel ortiz]

WOK :

Do you have any sort of flight envelope protection on the Concorde FBW system ?
Nice to handfly ?

Anyone out there who has flown the 777 to tell us a bit abaut their soft protections?
Windshear procedure ?
Pitch autotrim system when hand flying?
Does it also seek for 1 G when released with wings leveled hand flown ?

BRENOCH , maybe you can tell us , are you on the 777 ?

There is a good report by Ron Rogers called Flight tests results of the CFIT avoidance maneuver in FBW transports , March 1 99
available at Bluecoat forum "Reports"
It compares 777 vrs. A320/330

At conclusions/ Recomendations it basically
favors a bit on the Airbus , this mainly due to the better performance in closed loop escape maneuver results.

Evaluation team still favored the soft limits protection of the 777 based on the subjective judgement on the premise that there may be situations unforseen by the designers where the pilot might need to achive full aerodynamic capability .

Hard limits protection (With Override capability )to perform as good as the airbus on the closed loop escape maneuver and with automatic speedbrake retraction is recomended for the 777 .

Override authorithy for hard limit protection is recommended for future designs.

Makes sense to me Folks but better yet , read the article !!


[This message has been edited by manuel ortiz (edited 02 November 2000).]

[WOK]

The conc has some kind of envelope protection at all corners of the envelope, some nothing to do with FBW (eg mach,speed & alpha trim), some by virtue of the FBW - autostabs, superstab, outer elevon lockout etc.

There is a requirement for some of these facilities because a slender delta needs them to make the handling good.

The conc's handling is outstanding.

[buck-rogers]

That bl**dy great yoke thing does give you a feeling that you're actualy doing something, I suppose. It won't come off in your hand. (A twiddle stick does seem a wild way to control tons of metal in the air).

Side issue is that military a/c use fly by wire as it allows aircraft to be designed unstable. The computer keeps it flying straight but just watch it whip round when you wack the stick over!

[atomic]

That old yoke on the 777 was a brainchild of our Captains (UAL) involved in the development of the plane. And it was less an engineering but a I-have-flown-with-a-yoke-for-the-last-30 years-and-I-won't-touch-a-joystick-ever-kinda thing. Doesn't matter what kind of 'feeling' it gives you!!! We have a bunch of Captains on the Airbus who came from the 777 and they all agree that this wonderful plane should have a stick!!

[Tor]

Also, a sidestick leaves you with more room for your crewmeal http://www.pprune.org/ubb/NonCGI/tongue.gif

Tor

[This message has been edited by Tor (edited 05 November 2000).]

[AKAAB]

Took off yesterday in our 320 with a nice low-time lady pilot in the jumpseat. After passing 10k, she confessed, with wide eyes, "this airplane scares me!" "How do you even fly it?"

About halfway through my explanation of how the FCU is used to command the computers I suddenly realized what had scared her...

She didn't realize we had a sidestick! All she saw was there was no yoke, and she thought we were doing everything with the buttons!!!

Cheers!

AKAAB
Life's a pitch...then you sing!

[Smurfjet]

ROFLMAO!!! :)

Reminds me of this!

http://cogc.aircadet.com/dc9vsa320.jpg

------------------
SmurfJet (http://www.smurfjet.n3.net)

In this life, you have to think ahead to survive, not just on the flightdeck.

[Old Dog]

I have flown Boeings and Airbus. I like the Airbus a lot more. I am looking forward to go back to flying the Airbus. I didn't need a big yoke to fly that big bird.