Not sure how the hell you got tail structures as the source of the issue, other than the fact they have recovered the tail (incidentally the main carbon fibre structure in the aircraft, thus likely to float).

In fact, currently it is all speculative.

Necromancer asks a really good question, however, it should not be limited to the 330 but it should be generalized to the entire Airbus design philosophy and the entire Airbus line of aircraft.

 

I have spent a long time dealing with control systems of many types (I actually met Norbert Weiner when I was young and mostly ignorant) and, not for the first time, I am going to explain why I avoid Airbus gear when I can. This has real relevance to me as I travel a great deal -- thankfully not so much as a few years ago when I was doing 200,000 real air miles a year.

 

First, let's talk about structure -- more easily defined and a more rapid discussion. Airbus gear pass all design safety specifications for wing spars, vertical stabilizer attachment and the like. However, if you look at extreme loads and extreme conditions (e.g. engineering over design) you find that whatever aircraft type you care to compare (say MD to Airbus or Boeing to Airbus) that there is a substantive difference. The Airbus is more lightly built. This is a "feature" rather than a flaw as the business case for the aircraft required that it consume less fuel than the equivalent competitive aircraft. To this day the best way to do this is to lighten the aircraft -- given equivalent engines. I got the "whole nine yards" on this from the (then) Chief Pilot of Northwest Airlines on a trip from Osaka to Detroit a number of years ago. He really opposed the 330 purchase.

 

I traded some information to him (I don't know whether he used it but the management of NWA was entirely bean counter at the time -- still is -- so it likely made no difference) that is the second and a little more complex point to be made about Airbus.  The control system used in the Airbus can be dangerous under certain circumstances.

 

Airbus advocates two elements in a fly by wire system. The first is that the system is a "dead stick" system and the second is rule based primacy -- e.g. the computer overrules the pilot when the flight envelope is reached or exceeded.

 

Let's ignore the computer for a moment and talk about the dead stick approach. For generations of pilot training with mechanical systems the pilot has felt the "push back" of wing and stabilizer configuration changes. This push back -- almost a proprioceptive feedback mechanism -- is easily integrated into the pilots overall sensorium as it requires little or no visual or auditory integration (easily overwhelmed in an emergency due to multiple, simultaneous warnings) as it is simply there in the stick or wheel and it innately tells you something about the stress you are putting on the aircraft.

 

The 300 that went down right after 9-11 was lost because of the vertical stabilizer breaking loose from the aircraft. This was caused by the pilot pushing the dead stick radically back and forth in trying to control the aircraft when in a wake turblulence. The pilot simply did not have the data -- e.g. the fact that he was badly over stressing the vertical stabalizer -- and therefore could not act on it. Something very similar may have happened with the 330 that went down over the Atlantic.

 

To their credit, Boeing has introduced a proportional stick / wheel feedback technique for fly by wire that brings this level of the sensorium back to the control system.

 

The most improtant thing to think about, though is the software design philsophy of the supervising computer of the aircraft. Airbus has built a system that allows the aircraft to be flown comfortably and safely in 99.9%+ of circumstances. But, ignoring structural issues, what happens when you are forced out of that envelope? The Airbus system overrides the pilot and pulls the aircraft back into the envelope -- or at least it tries to, assuming that the sensor systems are working. The system is, therfore, rule centric.

 

In Boeings case the fly by wire system is pilot centric. The system will complain about being pulled out of the envelope but the system will comply as best it can.

 

So, the question is "Who do you trust?". The former SAC guy with white hair and thousands of hours or the rules of some anonymous engineer who, BTW, is safely at home? Remember, you are at an extreme, out of the envelpoe and your chances of survival are problematic. On the one hand, the computer will kill you because it cannot go past the envelope and the envelope has collapsed on the other hand the pilot may kill you but at least you have a fighting chance.

 

I choose the fighting chance.

 

Best,

wjr

you get no more. When a MAN reaches his limit.

 

Its called the Coastguard Way. If you send out the surfboat with a 160 HP engine in a sea-state 6, it and the six man crew doesn't come back. Send it out with ten man rowing and a cox'swain leading, and you get the boat  back, along with the five  idiots they rescued off the foundering yacht.

Herald

 

Based on your explanation, it sounds like the Airbus should be flown with kid gloves to avoid extreme flight conditions more so than its Boeing cousins as its rule based system is inherently not designed for out of envelope flight regimes which by definition air emergencies often are. 

 

It makes sense to me if you could somehow override the system like you can with traction control and active suspension systems in consumer vehicles.  

 

There may be more going on here than is obvious. I vividly recall Tex Avery (?) the Boeing test pilot barrel rolling the prototype 707 over Puget Sound. I have heard of several other incidents where MD's or Boeing's have been (inadvertently) rolled or put through aerobatics and surviving. I cannot recall an Airbus with this type of history.

 

One thing is obvious -- if the aircraft did not survive the maneuver it is highly unlikely that we would know what happened. Based upon a certain amount of paranoia and suspicion I wonder if the reduction of engineering margin means that these aircraft, e.g. the Airbus line, is under designed for edge of the envelope events. I am certain that I would not want to barrel roll an A320 -- I just have this sneaking suspicion that it would fold like a cheap suit.

 

BTW, I like the Coast Guard story. It is the truth.

 

Best,

wjr

There may be more going on here than is obvious. I vividly recall Tex Avery (?) the Boeing test pilot barrel rolling the prototype 707 over Puget Sound. I have heard of several other incidents where MD's or Boeing's have been (inadvertently) rolled or put through aerobatics and surviving. I cannot recall an Airbus with this type of history.

 

One thing is obvious -- if the aircraft did not survive the maneuver it is highly unlikely that we would know what happened. Based upon a certain amount of paranoia and suspicion I wonder if the reduction of engineering margin means that these aircraft, e.g. the Airbus line, is under designed for edge of the envelope events. I am certain that I would not want to barrel roll an A320 -- I just have this sneaking suspicion that it would fold like a cheap suit.

 

BTW, I like the Coast Guard story. It is the truth.

 

Best,

wjr

There may be more going on here than is obvious. I vividly recall Tex Avery (?) the Boeing test pilot barrel rolling the prototype 707 over Puget Sound. I have heard of several other incidents where MD's or Boeing's have been (inadvertently) rolled or put through aerobatics and surviving. I cannot recall an Airbus with this type of history.

 

One thing is obvious -- if the aircraft did not survive the maneuver it is highly unlikely that we would know what happened. Based upon a certain amount of paranoia and suspicion I wonder if the reduction of engineering margin means that these aircraft, e.g. the Airbus line, is under designed for edge of the envelope events. I am certain that I would not want to barrel roll an A320 -- I just have this sneaking suspicion that it would fold like a cheap suit.

 

BTW, I like the Coast Guard story. It is the truth.

 

Best,

wjr

Just rediscovered this discussion, other than asking if you guys will be avoiding the Dreamliner (the wings failed at 70% ultimate load) now, there are a number of flaws in the argument.

 

Lets start with the post 9/11  incident, Boeing stated that their tail fin would have failed under the same conditions, and both A&B re-wrote their respective training manuals to ensure pilots would not do this on either.

 

You have also made a VERY BASIC error in blaming the A300 accident on the airbus fly by wire system and 'dead stick' causing the accident. The VERY BASIC error is that the A300 does not use fly by wire, it uses a traditional yoke, and mechanical linkages The other error is that the tail is controlled by the rudder pedals (so would be unaffected by stick inputs), which even on newer models such as the A330 have a traditional mechanical linkage. 

 

In terms of questions concerning what happens when an aircraft leaves the flight envelope:

 

ABNORMAL ATTITUDE FLIGHT LAW

A completely different law emerges automatically when the aircraft is in an extreme upset as follows:

* pitch attitude > 50 deg nose up or > 30 deg nose down

* bank angle > 125 deg

* AOA > 30 deg or >-10 deg

* speed > 440 kts or < 60 kts

* mach > M0.96 or < M0.1

The abnormal attitude law is:

- PITCH ALTERNATE with no protection except LOAD FACTOR protection. No automatic pitch trim.

- ROLL DIRECT with full authority

- YAW ALTERNATE

After recovery the flight law reverts to:

- PITCH ALTERNATE law

- ROLL DIRECT law

- YAW ALTERNATE

The aircraft returns to a degraded mode (not normal law as usual) because there is a certain level of suspicion about its ability to control the aircraft (that is how could it have got to the extreme flight state in the first place? The protections should have intervened well before the pitch, bank, AOA, speed and mach limits above).

For the record you cant barrel role a (FBW) airbus because the flight control software will not allow the aircraft to bank beyond a set limit (around 20 deg i think but dont quote me) so the pilot canlean on that stick as much as he likes the aircraft will not pernmit him to go beyond a safe condition - same in pitch.

 

 

The A320 accident (breguette was it) at the airshow was because the when pilot flew down the runway then attempted to climb out at the end led to the type being much maligned (see WJR for ref). I also held the aircraft responsible at first until looking into it.

 

Th Plane crashed because it was to low and slow it would not allow the pilot to yank the nose up until it had more airspeed  due to the risk of stall.

 

In many quaters it is now considered that the pilot was at fault for his actions.

 

As to the claims against it for load tolerences

 

quote Anyone can build a bridge that stands up - it takes an engineer to build one that just barely stands up. un quote

 

 

This whole thread is quotable! Great stuff....

 

This is why SP is better than any newspaper... i defy you to pick up a newspaper and come away with one idea, one new thought... SP is indeed a precious commodity.