- #1
JaredJames
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Hi, I am currently studying aerospace engineering and recently have been doing some research on the airbus fly by wire system, (this was before the Air France crash although it has spurred me on a bit). I am posting this here as I am not certain whether it is truly an aerospace issue.
Basically, I have a few questions on the system that I cannot find the answer to anywhere despite hours of searching:
On the A320, there was a mechanical backup system, but on the A330-40 aircraft I have been unable to find any information regarding what happens in various power failure situations (however unlikely any may be, they are all still possible).
I understand the backup computer/electrical/hydraulic systems, how many there are and how they work with each other. My question comes from a number of different scenarios which may arise.
Firstly, what happens if all flight computer systems fail? Can the pilots still provide input to the hydraulic systems? Are the electrical signals still transmitted simply without the computer monitoring?
Secondly, if there is complete electrical failure (including all backups), however the engines are still running. Can they still be controlled? If so, I understand this would allow the pilot basic pitch control, but what would (s)he do about yaw/banking? Do the hydraulics work off of the engines or do they require electrics?
Thirdly, as above except with the engines offline. How would pitch/yaw/banking be controlled? (I understand that an answer for yaw/banking may be dependant on the answer to number two).
The questions above stem from my main issue with the fly by wire system, which I never see someone answer directly. I see everywhere that the hydraulics can work even during electrical failure. But is this with/without backup power (Batteries and RAT)? If there is a complete loss of electrics (again all backups lost), even if the hydraulics work, how can an electrical signal be sent from the flight controls in the cockpit to the hydraulic systems?
And finally, if there is a complete failure, how would the pilot fly the aircraft without electrics and hydraulics? Does a 767, which is not fly by wire require hydraulics? Or can it be flown without them (anyone who has seen Freefall - Flight 174, a true story, will know what I am aiming for here). The pilot managed to glide the aircraft with, as far as I am aware, no hydraulics or power what so ever (until the RAT kicked in after a certain amount of time although he did manage it without anything for quite a while). Is this possible in an Airbus A330-40 without the above mentioned systems or dead stick I should say? Even without the RAT the 767 was gliding quite well, would an Airbus?
I do apologise for the long windedness of the questions but I have spent hours researching it and cannot find anything that even comes close to answering my questions.
Any help very much appreciated, thanks in advance.
Jared James
Basically, I have a few questions on the system that I cannot find the answer to anywhere despite hours of searching:
On the A320, there was a mechanical backup system, but on the A330-40 aircraft I have been unable to find any information regarding what happens in various power failure situations (however unlikely any may be, they are all still possible).
I understand the backup computer/electrical/hydraulic systems, how many there are and how they work with each other. My question comes from a number of different scenarios which may arise.
Firstly, what happens if all flight computer systems fail? Can the pilots still provide input to the hydraulic systems? Are the electrical signals still transmitted simply without the computer monitoring?
Secondly, if there is complete electrical failure (including all backups), however the engines are still running. Can they still be controlled? If so, I understand this would allow the pilot basic pitch control, but what would (s)he do about yaw/banking? Do the hydraulics work off of the engines or do they require electrics?
Thirdly, as above except with the engines offline. How would pitch/yaw/banking be controlled? (I understand that an answer for yaw/banking may be dependant on the answer to number two).
The questions above stem from my main issue with the fly by wire system, which I never see someone answer directly. I see everywhere that the hydraulics can work even during electrical failure. But is this with/without backup power (Batteries and RAT)? If there is a complete loss of electrics (again all backups lost), even if the hydraulics work, how can an electrical signal be sent from the flight controls in the cockpit to the hydraulic systems?
And finally, if there is a complete failure, how would the pilot fly the aircraft without electrics and hydraulics? Does a 767, which is not fly by wire require hydraulics? Or can it be flown without them (anyone who has seen Freefall - Flight 174, a true story, will know what I am aiming for here). The pilot managed to glide the aircraft with, as far as I am aware, no hydraulics or power what so ever (until the RAT kicked in after a certain amount of time although he did manage it without anything for quite a while). Is this possible in an Airbus A330-40 without the above mentioned systems or dead stick I should say? Even without the RAT the 767 was gliding quite well, would an Airbus?
I do apologise for the long windedness of the questions but I have spent hours researching it and cannot find anything that even comes close to answering my questions.
Any help very much appreciated, thanks in advance.
Jared James