quote There have been studies done (NASA?) with a view to someday include a "thrust only" reversion into future flight control software. unquote
NASA (Dryden) developed the PCA (Propulsion Controlled Aircraft) concept using a MD-11 as testbed. There was a very nice article on this on an old Flight Internatinal magazine. The plane being controlled via the MCP, no need to direct handle the levers.
The green and yellow double failure seldomly occurs as two independent failures. Mostly the second failure is caused by the continuous operation of the PTU that connects both systems. Three simultanious failures are even more remote.
If the problem cant be solved with the QRH then you are in "no mans land" How it works is probably of of little use. One instructor I had in the USA talked about the "BRT" levers. These were the thrust levers. " When you push the BRT levers forward the big round things make more noise, that all you need to know"
Look at the rudder system, all 3 hydraulic systems are operating very closely to each other, Souix City, Japan Airlines, both lost all systems from one problem. So why is everyone so certain it will never happen on a a320. Murphys Law Anyone? If it can happen, it WILL happen.
What should be of more concern than a loss of all hydraulics, is the apparent lack of understanding from qualified crews of how the primary flight controls of their aircraft function.
What you should be concern about is that a manufacturer like airbus do not even consider possible that one of his planes could suffer by a triple Hyd fail. Infact, the Initial Airbus training (cbt) doesnt talk about it,the Fcom doesn talk about it.There is nowere any reference were you can get a secure reply about this question. The only thing you can do is to go throw the aircraft systems charts (flight control) and say ah yes, with no hyd you are on the ground.
Pilots are human beings and it's not 1 month course for a type rating which would give them the full kwnoledge about the airplane tey will fly. You need time, lot of study and questions like the one i have asked before say that you really know an aircraft. And i am surely not the kind of person that would feel is the best just because i'm sitted on a 320.
They do the maths and they come out with chances of it happenning so low, that it doesn't justify the installing of the fourth system.
Less than 10^-9 per flight hour. Just like other catastrophic failures.
Would be interesting what the "maths" say about DUAL HYD SYS LOSS.....
Off the top of my head I can't think of a G and Y hyd failure that wasn't caused by inadvertent use of the PTU. Certainly it's the biggest cause by far. It's interesting that despite all the cries from pilots about over automation in FBW Airbuses, pilot control of the PTU is a problem. Should Airbus remove the PTU p/b and automate the system further to prevent overheating and a resulting dual hyd loss?
757 and 767 also have three hydraulic systems, albeit without a PTU.
NASA proved the concept of PCA, FAA desided that it's not justified. They have calculated all safety improvements and do the relation between costs and lifes saved. Those improvements with the most "lifes for the buck" get the nod.
Yes, it may be a problem. Are you aware that faulty PBs kept YELLOW PTUs running?
Aside from that, IIRC the ECAM action for a G or Y hyd loss doesn't say turn off the PTU! And of course, in the event of a G or Y reservoir low quantity (or overheat) the PTU p/b will be shining away with a lovely 'FAULT' light. The PTU isn't FAULTy though and will be happily pumping the other system into a reservoir overheat. Moral of the story, know your systems.
Or maybe add some more logic to the PTU controller and remove the button altogether...?
It was not meant as a personal attack, but more as an attack on the industry. There seems to be a move towards the "no need to know" philosophy, rather than the "need to know" one. I trust you understand the difference.
As a classically trained engineer, who do give ground courses to aircrews, I find the level of training, and basic knowledge of those participating, to be seriously lacking in one very important aspect, understanding! There is no emphasis on understanding. Complete the exercise and tick the box, that is what training seems to have become. Ham and Enos would have been right at home.
This thread, and many other, are examples of this.
Three cheers! What is even worse, is there does not seem to be a place to go look it up either! While the aircraft systems of today can be so interconnected, it would be impossable to keep them all straight during an oral or PC, it would be great to have a "reference" manual that tells the real story.
It seems the older aircraft were built on the thought that the crew would be smarter than the aircraft, and today's aircraft are built on the, oh never mind.
By the scope of this thread, I assume that the cause of the triple failure is running all three systems dry. I'll see if I get some time in the simulator next week and see what ours does. I agree it might not be completely correct, but since the simulator models what happens with each system dry, it should be able to do it with all three empty. Also, some simulators have the real computers, they are just feed inputs.
AA DC-10 had a jammed stabilizer. Not the same as a total hydraulic loss but they were able to land using the #2 engine to change the pitch attitude. Using the wing mounted engines also has a pitching moment(power up, nose up, power back, nose down)
DC-10 into KSUX had total hydraulic failure. Read the NTSB witness statements, and not the final report. CKA Dennis Finch(sp?) saved the day.
A300 had total hydraulic failure after SAM impact. Did one go-around and then landed on the runway.
Total hydraulic failure is possible. It can be survivable but is tough to accomplish. I'm 2 out of 3 in my attempts. Fairly easy, very tough, and then a crash.