Die-By-Wire

[EconomyClass]

I think the sheer size of the wide body jets has made it necessary to substitute motors for human strength. So, fly-by-wire has either made bigger profits possible or company survival in brutal competition as another way of looking at it.

But to me, that means the cables that carry the signals to the motors become the most precious component in the airplane. If you can't move those controlling motors, you can't move the plane.

In which case, I'd say the survival of cables that carry the signals is a prerequisite to the survival of everyone on the plane. And it raises one question (many actually, but one I'm thinking of). Shouldnt every electrical circuit have a breaker switch or fuse? How can electrical wiring BURN in a modern electrical system? Apparently overheated wiring brought down a plane with all aboard lost. First time I heard of this, I thought "why did they overload circuits?" But sometime later, the obvious question is finally coming to me. Why weren't the overloaded circuits broken by some fusing solution? Everywhere that electricity is used, the engineers always include something to prevent overheating and fire? How could aviation engineers neglect something so universal and so basic?

[SYDCBRWOD]

EC what's with the alarmist heading? As usual, you have taken your 1% knowledge and built it into an issue before doing a little investigation first.

Firstly, on large aircraft the human arm and leg is basically useless in moving flight surfaces, servos and hydraulics have been doing that job for the past 50 years - predating fly by wire.

Secondly, FBW has probably saved many more lives than it has taken. It could be argued for instance that if the Colgan Q400 had been equipped with a FBW system the aircraft would not have allowed the pilot to stall the airframe.

Third, the wiring you seem to be commenting on is probably the Swissair flight - that was an issue with the insulation used (Kapton), yes, circuit breakers are used but there is always some part of a circuit that cannot be protected by a fusing device. The wires were not 'deliberately overloaded' IIRC, wire bundles in the In Flight Entertainment system chaffed through and created the shorts that started the fire. Kapton is no longer used as insulation in aircraft wiring.

Your car is the same - there is always a portion of cabling that is not protected by fuses - ideally this is kept as short as possible.

[Gabriel]

Not sure what accident are you talking about.

About the "wires" in FBW systems burning due to overload:

Swissair MD-11 over Canada was brought down by an electrical fire. No FBW.
An MD-80, don't remember which company, was brought down by an elctrical fire. No FBW

About an airplane being uncontrollable if an electric wire i cut in a FBW plane:

JAL 747 lost all hydraulic power after the rear pressure bulkhead failed and the fin was severed with all the hydraulic systems, the crew had absolutely o control over the control surfaces. No FBW.

The DC-10 that crashlanded in Sioux City lost all hidro power, and hence all control over the control surfaces, after a rotor disk of the #2 engine failed uncontained and sever the lines of all three hydro systems. No FBW.

Something similar happened to the A-300 that crashed somewhere in Irak I think, after the left wing was hit by a SAM severing all hydro systems. No FBW.

The American DC-10 that crashed taking off from O'Hare (I thing): the #1 engine separated from the wing, severing several hyro lines, including those that move the slats of the left wing, which retracted and the plane staled asymmetrically. No FBW.

Countless of accidents happened whith pull cables too. Ailerons that were connected inverted, with the airplane rolling immediatly after the take-off when the pilot tried to correct a bank only to worsen it (since a left input would move the ailerons to roll right). The famous turboprop accident that happened a few years back at takeoff and that most people blame the overweight and CG beyond aft limit was in fact caused by a missrigging of the elvator (maint eror), which produced insuficient nose-down elevator travel even wen pushing the yoke to the stops. Severed elvator cables have also caused loss of pitch control, usually with fatal endings. Too loose aileron cables have caused flutter, usually with the destruction of the wing as result.

So do you want to die by wire, die by hydro, or die by cable?

[Evan]

A great example of the benefit of FBW is AA587, where pilots overstressed the rudder and the Vstab separated from the airframe. That was an A310, the last of the non-FBW Airbuses. Had it been a FBW A330, control law would have made the incident impossible.

The Swissair MD11 incident was the result of a chain of corrupted procedures that allowed non-certified installation of an in-flight entertainment system. I read the accident report a few years ago. The system was a lemon, plagued with overheating problems and was wired to the wrong bus. It was a non-standard wiring job by a third party entity and has nothing to do with McD or FBW.

EC, you need to learn more about the technology. I think this thread is pointless.

[ATFS_Crash]

You stole my catchphrase “die by wire” that I’ve been using for decades. However I only selectively use it when there’s a problem or when I have suspicions.

Fly by wire has advantages and disadvantages. In some areas you gain safety; in other areas you sacrifice safety. There is no perfect solution.

Most if not all circuits on aircraft have circuit protection; but no circuit protection is flawless. This is the real world not Hollyweird.

You sound a little like chicken little or a lawyer; paranoia and greed.

I agree that there are some weaknesses to fly by wire and there is room for skepticism and criticism. But the same thing can be said about legacy systems.

If you have some specific complaints make them. It seems you just went on a rant to use your catchphrase that many of us thought of a long time ago.

I am very skeptical of some of the new flyby wire systems; however much of that is probably because we have a tendency to fear what we don’t understand. I understand electricity well; but I’m very naïve to the specific systems used in large aircraft like airliners. If I spent a few evenings with engineers going over the wiring diagrams and flowcharts; there’s a good chance I would feel a lot more comfortable with airline fly by wire.

I had a chance to talk with an F-22 pilot and engineers and they were able to put to rest most of my fly by wire fears of the F-22.

Here’s a link to a post I made about fly by wire. It includes some of the advantages of fly by wire in language that is easy to understand to me. The language I used is largely in layman terms; so hopefully someone with a little knowledge of aviation should be able to follow.

http://forums.jetphotos.net/showpost.php?p=516418&postcount=1146

This is an example where I think advanced flyby wire might have saved the day.

It's too bad that Alaskan airline that crashed because the elevator trim screw stripped due to lack of lubrication; didn't have redundant independently controlled control surfaces, controlled from a computer with the ability to compensate for failures.

[TeeVee]

correct me if i am wrong, but FBW does not really require Laws. What I mean is, it would be possible to build a FBW system that is (sorry about my layman's terminology) nothing more than a complex system of rheostats. Airbus created their FBW system to be dependent on laws. But isn't it theoretically possible to have a FBW system that does nothing more than move control surfaces exactly as commanded?

[Evan]

correct me if i am wrong, but FBW does not really require Laws. What I mean is, it would be possible to build a FBW system that is (sorry about my layman's terminology) nothing more than a complex system of rheostats. Airbus created their FBW system to be dependent on laws. But isn't it theoretically possible to have a FBW system that does nothing more than move control surfaces exactly as commanded?

Technically, FBW simply means the interface between the cockpit controls and the control surfaces is electronic, not mechanical. Most (if not all) FBW systems involve a computer that interprets the pilot inputs and calculates the optimum control surface movements. When a pilot moves the stick to the left, he is not actually rolling the aircraft, he is making a roll request. When he moves the throttles, he is not actually adding throttle, he is making a request for power.

Think of it like a large ship, a steamship in the 1920's. The throttle at the helm is not a throttle at all, it is a telegraph. The pilot sends a request for power to the engine room, where the actual throttle is moved. There is no direct mechanical link, there is an informational link. Except there is no possibility of insubordination with FBW (at least as long as you're not flying a BA777 into Heathrow).

The advantages of FBW are reduced mechanical complexity, increased reliability via electronic connections, increased performance through reduced stability designs, weight reduction from reduced stability designs and computerized flight control that can trim with a greater accuracy than is humanly possible. Control laws add another dimension of safety. The aircraft knows its limitations at any given moment and is allowed to govern its own behavior regardless of what a ill-trained pilot might choose to do with it. Think of it as machine self-preservation.

The trouble occurs when the air data and/or inertial reference circuits are inhibited or otherwise degraded. That aspect of FBW needs some upgrading. The current Airbus FBW system might need a clearer means of hand-off to pilots as well. That is what we were discussing on the AF447 thread. We need to kill this negative thread and return the conversation back to there.

[P3_Super_Bee]

Kapton is no longer used as insulation in aircraft wiring.

Sure about that???

No longer installed on aircraft would be the better comment.

Airbus installed it up until 2006. They did start using a Kapton with "Teflon" coating in the 90's, but that was just a "token" fix to shut the unknowing up. The Teflon's only basic fuction is to marking purposes of the wire. In 2006 they started to use there own version of Boeing's TKT.

Boeing quit using it in 91, If you want to count MDD into Boeing then 92

[SYDCBRWOD]

correct me if i am wrong, but FBW does not really require Laws. What I mean is, it would be possible to build a FBW system that is (sorry about my layman's terminology) nothing more than a complex system of rheostats. Airbus created their FBW system to be dependent on laws. But isn't it theoretically possible to have a FBW system that does nothing more than move control surfaces exactly as commanded?

Yes. And that is basically what is supposed to exist in the A330's systems once the AIDRU's drop out (no second guessing, no protection laws).

In relation to AF447 the question is do we know whether this was the problem? For all we know the aircraft was probably doing exactly what the pilot commanded - the problem is possibly that the pilot didn't know whether the info he was relying on was correct as his instruments may have been feeding misleading information to him.

[SYDCBRWOD]

Sure about that???

No longer installed on aircraft would be the better comment.

Airbus installed it up until 2006. They did start using a Kapton with "Teflon" coating in the 90's, but that was just a "token" fix to shut the unknowing up. The Teflon's only basic fuction is to marking purposes of the wire. In 2006 they started to use there own version of Boeing's TKT.

Boeing quit using it in 91, If you want to count MDD into Boeing then 92

Agreed - no longer installed. Didn't know Airbus kept using it as late as that though.

[TeeVee]

Thanks Evan and SYD. That's what I thought.

p.s. wasn't the BA 777 a fuel line freezing issue?

[EconomyClass]

Has anyone ever created a multivariant equation expression how much of the variation in air accident reduction actually derives from all the many changes made in the last half century? Every time an issue comes up, the apologists for technology always quote the aggregate change as if some particular technological change is totally responsible. Frankly, I could just as well say the change occurred due to government mandating fixes to badly engineered mechanisms. It wouldnt really be valid,but it would be just as valid as the claims people make here. Truth is you don't really know if technology made flying safer, you just like to assume so.

I don't regret my thread title at all. Unlike you folks, the real people of the world are asking the exact questions of the world. Outside this controlled and slanted environment, people are losing their awe of aviation insiders because these insiders are losing people too often.

[EconomyClass]

Apparently the MD-11 had circuit breakers, but poorly-installed ones.

1999, May 7. AD 99-09-04, MD-11, for incorrect installation of circuit breakers, during production.
�inspection to verify correct wire terminations of certain circuit breakers in the cockpit overhead switch panel; and correction of incorrect wire termination�. This amendment is prompted by incidents in which the wiring of circuit breakers on the overhead switch panel lighting were found to be terminated improperly during production of the airplane, which bypassed the circuit breaker protection. The actions specified in this AD are intended to prevent smoke and possible fire in the overhead switch panel lighting circuitry due to an overload condition, as a result of lack of circuit breaker protection.
�the FAA has become aware of an incident in which the wiring to a circuit breaker on the overhead switch panel lighting was found to be terminated improperly on a�MD-11�.The bus assembly and the wire were connected on the same lug with nothing connected to the load side of the circuit breaker (i.e., bypassing the circuit breaker protection).
A subsequent line check of Model MD-11 series airplanes in production revealed that the wiring to three other circuit breakers on the overhead switch panel also were terminated improperly on some airplanes. Further investigation revealed that the MD-11 production build paper did not reference the wire hook-up chart for wire termination of the circuit breakers of the overhead switch panel lighting. (These incidents are not considered to be related to an accident that occurred off the coast of Nova Scotia involving a McDonnell Douglas Model MD-11 series airplane. The cause of that accident is still under investigation.)
Lack of circuit breaker protection for the circuit of the overhead switch panel lighting, if not corrected, could result in smoke and possible fire in the overhead switch panel lighting if the circuit breaker has an overload condition.

[atcvector]

I think the sheer size of the wide body jets has made it necessary to substitute motors for human strength. So, fly-by-wire has either made bigger profits possible or company survival in brutal competition as another way of looking at it.

But to me, that means the cables that carry the signals to the motors become the most precious component in the airplane. If you can't move those controlling motors, you can't move the plane.

In which case, I'd say the survival of cables that carry the signals is a prerequisite to the survival of everyone on the plane. And it raises one question (many actually, but one I'm thinking of). Shouldnt every electrical circuit have a breaker switch or fuse? How can electrical wiring BURN in a modern electrical system? Apparently overheated wiring brought down a plane with all aboard lost. First time I heard of this, I thought "why did they overload circuits?" But sometime later, the obvious question is finally coming to me. Why weren't the overloaded circuits broken by some fusing solution? Everywhere that electricity is used, the engineers always include something to prevent overheating and fire? How could aviation engineers neglect something so universal and so basic?

Are you related to Scary Mary?

[B757300]

Are you related to Scary Mary?

LOL!

The level of intelligence in the arguments is about what one would expect from that dumb b*tch. (And for anyone who doesn't get it, I am calling Scary Mary a dumb b*tch.)