Second 747-800 customer!

Will a composite fuselage be able to survive such catastrophic damage?

Sure, they don’t differ so much in design, so the load paths are similar. Structure is designed for ultimate loads, that is maximum load in service with a factor of 1.5 added. So, when flown carefully there are plenty of reserves.
The ALOHA flight crew didn’t exercise a 2.5g pitch-up or a hard landing, which normally designs the forward fuselage upper shell (and pressurization wasn’t an issue any more).

Very true Paul, I was going to say that you can get on board the safest plane with an incompetent crew and all the testing goes out the window….
regards
Ralph

I’d like to think there arn’t all that many “incompetent” crews out there to be honest!

Paul

Very true Paul, I was going to say that you can get on board the safest plane with an incompetent crew and all the testing goes out the window….
regards
Ralph

That is right as far as I’m concerned because they are always sending software updates to correct bugs that escaped the extensive testing. Otherwise Microsoft and other software giants would hire those programmers and never have to send out corrections again.

It’s OK saying that but again, where do we stop? With the safest aircraft in the world there’s no guarantee turbulence won’t bring your plane down or some mad man won’t fire a rocket at it, so shall we stop flying altogether based on that minimal yet still entirely possible risk?

Systems and software are tested to the very highest standards we know of, and we won’t advance anywhere or improve anything unless we continue developing new systems, testing them and getting them out working. Mistakes will happen; there’s no doubt about that, but they always do happen when things progress. I don’t really see how aviation is or should be any different.

Paul

There have been some very scary actual inflight incidents caused by the computers. At least two 777 incidents were traced to problems with some of the onboard computers, you can read about one of them here:
http://www.airlinesafety.com/faq/777DataFailure.htm
This incident and another related one caused an emergency Airworthiness Directive to be issued by the FAA.
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/25F9233FE09B613F8625706C005D0C53?OpenDocument

And then again there is AF447, which the investigators haven’t fully figured out yet.

And then there were the F-22’s whose were unable to navigate after crossing the International Date Line the first time….good thing they had a tanker to follow.

So I believe it can be stated that even with “multiple redundancies” and “extensive testing and simulation,” incidents can still happen. I’ve only listed a few of the commonly known ones. The scary part of theses types of incidents is that they were induced by the new technology. You didn’t hear about these kinds of problems on the DC-8 for example. I don’t believe it is unreasonable for observers to say the system of testing and approving new computerized technology for aviation could be more bulletproof.

That is right as far as I’m concerned because they are always sending software updates to correct bugs that escaped the extensive testing. Otherwise Microsoft and other software giants would hire those programmers and never have to send out corrections again. Wikipedia says that the A320 has suffered at least 50 incidents of EFIS blackout whilst the figures given for the 757 and 767 are much lower (or not all are mentioned). Although I must agree that modern testing programs are very thorough.

There have been some very scary actual inflight incidents caused by the computers. At least two 777 incidents were traced to problems with some of the onboard computers, you can read about one of them here:
http://www.airlinesafety.com/faq/777DataFailure.htm
This incident and another related one caused an emergency Airworthiness Directive to be issued by the FAA.
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/25F9233FE09B613F8625706C005D0C53?OpenDocument

And then again there is AF447, which the investigators haven’t fully figured out yet.

And then there were the F-22’s whose were unable to navigate after crossing the International Date Line the first time….good thing they had a tanker to follow.

So I believe it can be stated that even with “multiple redundancies” and “extensive testing and simulation,” incidents can still happen. I’ve only listed a few of the commonly known ones. The scary part of theses types of incidents is that they were induced by the new technology. You didn’t hear about these kinds of problems on the DC-8 for example. I don’t believe it is unreasonable for observers to say the system of testing and approving new computerized technology for aviation could be more bulletproof.

Very fair points but surely ‘everything’ could be more bullet-proof? There have also been countless incidents on other aircraft types due, for example, to inadequate training or a lack of knowledge on the part of the crew (Aeroflot A310 for one). The question to me is where do we stop and draw the line between what is and isn’t acceptable and safe? Sometimes mistakes have to be made to discover a flaw and many of the things we know now and that have made flying safer have sadly resulted from the loss of aircraft and lives.

Surely there’s always a risk in every element of flying, even if for no other reason than the fact we’re human and will probably never create the ‘perfect’ machine or the ‘perfect’ line of code?

Paul

I don’t think you quite understand the concept of multiple-redundant systems, or the battery of extensive testing and simulation that has to be satisfied before code is cleared for live service. It’s not just some bloke sitting there with a PC, you know!

After all, there is also a probability of a chunk of an aircraft’s wing being torn off by a passing meteorite. Let’s ground every aircraft in the world just to be on the safe side, shall we?

There have been some very scary actual inflight incidents caused by the computers. At least two 777 incidents were traced to problems with some of the onboard computers, you can read about one of them here:
http://www.airlinesafety.com/faq/777DataFailure.htm
This incident and another related one caused an emergency Airworthiness Directive to be issued by the FAA.
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/25F9233FE09B613F8625706C005D0C53?OpenDocument

And then again there is AF447, which the investigators haven’t fully figured out yet.

And then there were the F-22’s whose were unable to navigate after crossing the International Date Line the first time….good thing they had a tanker to follow.

So I believe it can be stated that even with “multiple redundancies” and “extensive testing and simulation,” incidents can still happen. I’ve only listed a few of the commonly known ones. The scary part of theses types of incidents is that they were induced by the new technology. You didn’t hear about these kinds of problems on the DC-8 for example. I don’t believe it is unreasonable for observers to say the system of testing and approving new computerized technology for aviation could be more bulletproof.

Agreed. Now what I would like to know is what is the probability of there being a latent error in a line of software code in one of the zillions of algorithms in an entirely computer controlled aircraft? I think this has happened before. And with 600 souls on board, a rogue comma could cause a lot of misery.

To be honest I’m not entirely convinced we’ll ever see a ‘pilotless’ computer controlled passenger aircraft. I certainly wouldn’t want to fly on one anyway!

Paul

Agreed. Now what I would like to know is what is the probability of there being a latent error in a line of software code in one of the zillions of algorithms in an entirely computer controlled aircraft? I think this has happened before. And with 600 souls on board, a rogue comma could cause a lot of misery.

I don’t think you quite understand the concept of multiple-redundant systems, or the battery of extensive testing and simulation that has to be satisfied before code is cleared for live service. It’s not just some bloke sitting there with a PC, you know!

After all, there is also a probability of a chunk of an aircraft’s wing being torn off by a passing meteorite. Let’s ground every aircraft in the world just to be on the safe side, shall we?

…when critical lines or systems are damaged…
Paul

Agreed. Now what I would like to know is what is the probability of there being a latent error in a line of software code in one of the zillions of algorithms in an entirely computer controlled aircraft? I think this has happened before. And with 600 souls on board, a rogue comma could cause a lot of misery.

Simple

United232 still had an element of control. The pilots were still connected to the controls via cables. The Hyraulics merely powered the actuators for the control surfaces, making moving them a much easier process. When the hydraulic lines were cut enough fluid was left inside the actuators to allow for some restricted movement. So, for United 232, they was just enough command of the control surfaces left for them to “fly” the plane, albeit not without great difficulty.

Onboard THY981 however, IIRC, all those cables that physcally linked the cockpit to the tail were cut. There was no way the pilots could have controled the up and down and yaw movement of the plane.
What doomed them was the way the cables were cut. The process actually moved the elevators. When the floor collapsed, it first pulled the cables down with it, this seems to have moved the elevators to a downward facing position. The cables then overstressed and snapped. All this happened within the blink of an eye.
Once the cables snapped, there was no way for the crew to move the elevators back to neutral or up. With its elevators pointing down, the plane entered a dive.

No ammount of engine power available to the pilots would have saved them.

I take it you mean JAL123.
What you’re forgetting is that JAL123 did not just loose hydraulics. They physically lost almost all of the control surfaces on the tail section. The explosion left them with no rudder, hardly any vertical stabiliser and so little elevator surface that they could not have hoped to bring that ship home, with or without hydraulics.

Yes. On United 232, rudder and elevator surfaces remained attached to the tail, but there was no hydraulic control over them.

All the control cables that lead to the tail were severed. Hydraulics, IIRC were not affected.

Which means that THY 981 had throttle control over both wing engines, like United 232.

Why did THY 981 enter into an out of control dive?

Will a composite fuselage be able to survive such catastrophic damage?

That’s a question for someone more qualified than me to answer! 😀

Paul

Will a composite fuselage be able to survive such catastrophic damage?

Let’s start another thread ” Remarkable survivors” or similar. Great topic.

There is a limit to how much you can blow off a plane till it stops flying, varies from plane to plane and incident to incident and the crew’s ability. Look at Aloha Airlines B737 and the thread http://forum.keypublishing.co.uk/showthread.php?t=96175 and what about that 747 whose side blew out over the ocean(I forget the operator). Good old fashioned engineering. Surely one fatal accident claim can cost a lot more than the pennies that were being saved on fuel? Thats what operators seem to go for at the expense of comfort and solid reliability.

In both the Aloha 737 and the United 747 incidents the part of the aircraft that was lost didn’t compromise any critical systems, so both were able to continue flight and land safely. I don’t think it’s a case of good old engineering as much as they just got lucky. Problems seem to occur (not that having a chunk out of your fuselage isn’t a problem, but still…) when critical lines or systems are damaged. AA 191 seems good example. Although the engine separated from the aircraft in exactly the way it was designed to do (flying up and over the wing), it took hydraulic lines with it. The crew sadly had no warning the left wing flaps were retracting due to the loss of hydraulic fluid, and hence that wing stalled ultimately causing the crash. Had they known the flaps were retracting there’s a chance they may have been able to retract the flaps on the right wing and make a higher speed landing.

I do think it’s quite remarkable the crew of the DHL A300 were able to get their aircraft back on the ground using purely differential engine thrust though, despite part of the wing not being there anymore!

Paul

There is a limit to how much you can blow off a plane till it stops flying, varies from plane to plane and incident to incident and the crew’s ability. Look at Aloha Airlines B737 and the thread http://forum.keypublishing.co.uk/showthread.php?t=96175 and what about that 747 whose side blew out over the ocean(I forget the operator). Good old fashioned engineering. Surely one fatal accident claim can cost a lot more than the pennies that were being saved on fuel? Thats what operators seem to go for at the expense of comfort and solid reliability.

Which did little good to the 500+ souls on JAL.

I take it you mean JAL123.
What you’re forgetting is that JAL123 did not just loose hydraulics. They physically lost almost all of the control surfaces on the tail section. The explosion left them with no rudder, hardly any vertical stabiliser and so little elevator surface that they could not have hoped to bring that ship home, with or without hydraulics.

Which controls were directly destroyed by the Ermenonville THY DC-10 door blowout?

All the control cables that lead to the tail were severed. Hydraulics, IIRC were not affected.

The actual number of hydraulic systems, 3 or 4, did not matter because a single point of damage would drain them all.

Absolutely correct, which is why your point of the DC-10 and A300 “doing rather better” made no sense.

Paul

P.S. I assume the “wingtip rocket explosion” refers to the DHL A300?

I suspect that it was correct, yes.

Crashes directly from draining all redundant hydraulic systems have happened to several airplane types – 747 (tail bulkhead explosion), DC-10 (tail engine fan explosion), A300 (wingtip rocket explosion). What made a difference to the outcome was handling the backup system/s. The actual number of hydraulic systems, 3 or 4, did not matter because a single point of damage would drain them all.

Which controls were directly destroyed by the Ermenonville THY DC-10 door blowout?

DC-10 with just 3 hydraulic systems, did rather better.

Are you sure you’ve done your research correctly there?

Plus, what does a rear pressure bulkhead failure (as happened in the JAL incident) have to directly do with hydraulics? Yes, it severed all 4 hydraulic lines but the cargo door incidents on the DC-10 did similar damage.

Paul