Digital vs Manual Flight controls

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hornetfinn

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Unread post07 Jan 2020, 12:33

I'm sure Digital FBW system could do many things that would be impossible with manual flight controls or even analog FBW. Especially when the aircraft has been designed for it from the beginning with really relaxed stability and ability to control all control surfaces independently.
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rheonomic

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Unread post01 Mar 2020, 05:22

zero-one wrote:See with FBW, whats impossible is pretty much set in stone, specially with modern CLAWS, if the limiter says you can't do it, then you can't do it no matter how hard you try.

This isn't really true; it's almost always possible to defeat the limiters if you try hard enough. It's difficult to make a "hard" limit without degrading performance too much.
zero-one wrote:And some, like the F-16's is optimized to pull Gs. If I'm not mistaken if you pull back on the stick, you're essentially asking for Gs not AoA.

Modern fighters are generally G command systems in up-and-away mode and angle-of-attack or pitch rate systems in powered approach mode.
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zero-one

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Unread post01 Mar 2020, 11:40

Thanks rheonomic.
I remember when the Soviets were designing the Su-27 and Mig-29 there was a heated debate into including or excluding FBW.

One of them remarked
FBW makes a bad pilot good but makes a great pilot mediocre.

Obviously we're going to dismiss that as total BS, but I can't help but think, what was his basis for that, obviously they wanted to benefit Soviet fighter design so why would they oppose something that they are well capable of developing anyway.

Maybe he was referring to early soviet versions of FBW that restricted pilot's too much and limited what the aircraft could do. just my guess.
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quicksilver

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Unread post01 Mar 2020, 15:19

“FBW makes a bad pilot good but makes a great pilot mediocre. Obviously we're going to dismiss that as total BS...”

BS? Perhaps ‘semantically imprecise.’ My observation is that fbw makes certain things ‘safely repeatable’ by (almost) every pilot in a given squadron. There are clear differences in hand/eye talent between some, but most of what makes someone a ‘bad’ pilot is about what happens between his or her ears, and thus a fbw system isn’t going to have much effect there. These days, most do not have enough time in ’manual’ systems to notice a difference, and ‘manual’ these days is generally ‘well-augmented‘ by strong stab aug systems — i.e. the machine has a vote about what happens when you make control inputs.

Also, some think that fbw is ‘limiting’ because there’s some extra ‘something’ out there performance-wise beyond the limits that they are being prevented from accessing. My opinion is that’s not the case; you learn to fight the jet ya got. If there’s some edge of the envelope stuff you think you need because you’re getting your a$$ handed to you all the time, you may wanna rethink all the stuff that is happening before you get to that part of a fight in those circumstances.
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rheonomic

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Unread post01 Mar 2020, 22:26

I think a lot of that comes with the introduction of a new technology, particularly one that is so flight critical. I'll make the claim that a well-designed FBW system will always result in an airplane that can outmaneuver a similar aircraft with a manual control system. In particular, modern FBW systems remove a lot of the effort of flying the airplane, and let you focus on fighting the airplane. Early on though, there was a lot of concern about HAL taking over the airplane and overriding the pilot. A good CLAW design team will work with test pilots to address the aircraft handling qualities and performance during the CLAW design process.

I don't know enough about Soviet/Russian flight control systems to really comment on them; the only thing I've ever seen is a partial block diagram of the longitudinal control system of the Su-37 demonstrator reprinted in Gary Balas's article "Flight Control Design: An Industry Perspective" (slide 49 of this), which is a classical system roughly comparable to what you would find on an F-16, but far less advanced than F-35's Nonlinear Dynamic Inversion. If anyone has more information on this I'd love to see it; there doesn't seem to be much English-language literature on Russian flight control system design available in open sources.
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quicksilver

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Unread post02 Mar 2020, 00:09

FBW = “New technology...” ???

:lmao: :lmao: :lmao:

How old are you?
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outlaw162

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Unread post02 Mar 2020, 00:27

The future is EMI resistant FBL, followed by.....FBPFM. :mrgreen:
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rheonomic

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Unread post02 Mar 2020, 00:33

quicksilver wrote:FBW = “New technology...” ???

:lmao: :lmao: :lmao:

How old are you?
Lol, I was referring to its historical introduction in the 70s and all the related concerns then, not saying it's a new technology now.

I do know a few people that could say that and actually mean it, though...
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quicksilver

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Unread post02 Mar 2020, 00:43

rheonomic wrote:
quicksilver wrote:FBW = “New technology...” ???

:lmao: :lmao: :lmao:

How old are you?
Lol, I was referring to its historical introduction in the 70s and all the related concerns then, not saying it's a new technology now.

I do know a few people that could say that and actually mean it, though...


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