Quote:
Originally Posted by Peter Ward
I disagree. With degraded systems, rather than struggling to keep in control as in non-FBW, FBW makes the push-pull bit easier, giving you more brain power to manage the failure and come up with a solution.
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The "push-pull" may well be easier, but you've substituted it with complex flight computer issues and as we have recently seen in that case of Airbus (Air France) pitot data input issues as well...which may be beyond a pilots capability to diagnose in the heat of the moment and in time sensitive scenarios. Being able to fly 'hands-on' and forget diagnosing a computer's hissy-fit is THE primary objective during a flight issue. Let me know what airline disagrees with that I promise you I'll stay clear of them. I bet this exact issue is being addressed at Airbus right now (just remember they're French and I've worked on Mirage; they're never wrong...NOT!). Aeroflot 593 was a classic case of trying to recover an aircraft (A330) in a classical manner but what resulted was an inevitable fight between the pilot, the flight computer. I would not be surprised if the pilots of AF447 had done the right thing and let the computer do the flying when the issues occurred, the aircraft became unrecoverable for the computer, the computer then handed the controls back to the pilots during the unrecoverable state.
I don't really want a pilot to be flying with his brains, I would much prefer his flying skills, gut instinct and a good eye...as for grey matter, that's highly overrated in an emergency...just a cool head and an automatic (trained) response within a classical system is the best. Don't work the problem, work a solution to your current situation. Worry about bugs in Microsoft when it asks you to send a failure massage...coz that means that you're alive still.
Quote:
Originally Posted by Peter Ward
No aviator in their right mind would want a total (flight control) hydraulic loss. I have never had one in a non-FBW type, simulated or real. Wouldn't want one either.
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Totally besides the point.
Quote:
Originally Posted by Peter Ward
United Flight 232 (Soux City) had one and despite some very remarkable flying by the crew, the aircraft still crashed and burned.
Yet the A380, (a FBW type) can have this type of failure and remain very flyable....which was my point in the first place.
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As the Hstab was shredded, the only way United 232 could have survived was if the ailerons were on a separate system and that they could be run as AilerVons.
There are two issues here;
1. Total Hyd failure
2. FBW failure
In case 1, the A380 should be usable IF the failure is limited to just the main Hyd systems and the EHAs are not affected, reverting to local hyd circuit. If an aileron becomes locked (stuck valve or flight computer), and ports fluid then you'll have max throw or a fight between EBHA and EHA (EHA will win). EBHA shifts from main hyd to local hyd under electric power under main hyd failure. Both EHA and EBHA circuits seem entirely dependent upon flight computer input. If you have both Hyd and electrical failure (not likely), better pray there's a good battery and ram air generator somewhere.
In case 2, you're dead. And this brings us right back to the original FBW discussion.
Quote:
Originally Posted by Peter Ward
Most heavy (non-FBW) types have hydraulic systems with artificial feel making them no more friendly than FBW systems, hence I do not understand why you would be "against FBW" , as in both cases it is not possible (to downright dangerous) to develop/test their systems for real at high levels of degradation without serious risk of a hull loss.
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But they still have mechanical feedback. For instance, a push-pull tube which is hyd assist (99%) will still give good flight control feed back as there is only so much a hyd system can dampen strain and vibrations. Go Hyd off and everything weights a tonne and with near 100% feedback. Of course they introduce stick shakers and force gradients, but these can be disables during hyd off operations.
What manufacturers could look for is more hyd assist in larger A380 size aircraft, and in hyd off (failure of prim and sec), offer 70% hyd assist via accumulator/local elect-hyd systems. FBW merely looks for pilot (strain) input and provides assistance, knowing what inputs are being done by the crew, and porting hyd power BEHIND the pilots [force] input, rather than IN FRONT of the pilots input as in the case of current FBW.
Think of a CNC milling machine. If it has an image and just cuts away according to a program it will simply break the tooling. But if the mill is able to sense the dimensions of the material to be cut, rate of rotation etc, then it is able to apply the milling process in an intelligent manner. This is where FBW fails, it looks at side stick (& pedal) input. I'm saying it should look for strain within the physical linkages and get behind the pilots' actions at the actuator end AND mid stream too!
You're actually a pilot, you should agree with the pilot being in control, but as it stands, you really aren't. And you can come up with whatever computer to pilot algorithm model you like, the fact is-is that you aren't. Your inputs aren't being inputted at all, they're being analysed (assessed actually) and then inputted. I'm not saying pilots are redundant, since FBW looks for your input, but you are being handed your hat and coat on the flight deck.