New Clues deepen AA587 Crash Mystery

[moggie]

Why is it that any accident involving a european built airliner results in calls of "ground them" when Boeings, apparently, should just fly on?

I am thinking of the two hull losses caused by rudder hard overs on B737, a near hull loss caused by structural failure on an Aloha 737 and two hull losses caused by fuel pumps catching fire (TWA 800 747 and a Thai 737). And if anyone syas "but Boeing say the rudder hardover does not exist" I know that BA had at least one and Boeing also chose to redesign it for the NG model. So why redesign if it is OK?

These are just a few which come to mind - but this is (as best I can tell) the first airbus crash in which structural failure MAY have contributed - the majority of the rest are "operator error".

So lets get it straight guys - if the FAA are happy to let Boeing operators risk pax lives while they have a long slow think about rudder hardover and fuel pumps, why the call to ground the Airbus? protectionism that's why. And I don't care if it's non-PC to say so, it's true.

[basil fawlty]

With ref to the BOAC 707 crash, my father was flight engineer on the previous sector (San Francisco - Honolulu). He recalls that they went thru some serious CAT, "nodding pods", autopilot out and flown attitude etc etc.
The astonishing thing is that he was never called to give any evidence at the board of enquiry!

[allianceair]

Gaunty:

Where did you see this photograph and what newspaper do you write for??

[Shore Guy]

Bob Francis, former NTSB investigator, in an interview said that wake encounter was possibly influenced by the fact that the AA aircraft turned inside the arc of the JAL 747, thereby reducing the already reduced separation (? believe aircraft took off with slightly less than two minute separation ?). This also puts the AA aircraft entering the wake/vortice at an angle, increasing loads/stresses.

[brain fade]

Surely the question of whether or not there was a wake turbulence encounter is irrelevant? The Airbus should be strong enough to survive easily.
What i think we are seeing here is the first instance of structural failure of Carbon fibre composites when used as primary load bearing structure on a composite (ie alloy+CFC) airframe. We all know this material is good for doors, flaps, fairings etc, but these are all either hinged or non load bearing. We also know that it makes great all plastic aircraft.But when you make an aluminium aeroplane with a bolt on Plastic tail, you need to spend a lot of time making a joint which allows all the loads to pass but is good for the different materials on both sides. Perhaps we have a bit of the learning curve still in front of us here. I suppose this amounts to idle speculation, but it was a most unusual accident.

[Wino]

Moggie
My what a short memory you have. The FAA grounded all DC-10's for a very long time after the engine seperation and crash in chicago.

In the case of the 737 rudder hard overs, a fix was immediately implemented. The aircraft speeds were changed to require flying faster than crossover speed so that a hard over rudder could be overcome by the ailerons. That required adding 10 knots or more to approach speeds.

For those of you who are not into aerodymanics, crossover speed refers to a specific angle of attack. An angle of attack lower than crossover will have the ailerons stronger than the rudder and a greater angle of attack would make the rudder stronger. So to reduce angle of attack you either unload (reduce G) or increase speed. The 737 is now flown faster so that a rudder hardover, while exciting, isn't fatal, like an engine failure or other problem we are trained to deal with.

As to the aloha aircraft, much of ALoha's fleet and several other aircraft of similar vintage were immediately grounded. Others were life limited as a result of the ageing aircraft program that followed the initial grounding. (60000 cycle inspection became too expensive)

So, no it is not a plot against airbus, you are free to keep thinking that however. In the meantime there is another similar accident in Africa from about 2 years ago on the A300/310 that is also unsolved. 2 aircraft out of 400 or so vs 2 out of 3500 737s sure doesn't look favorable for airbus.

But go ahead and falsly scream protectionism if it helps you sleep better.

Cheers
Wino

[SaturnV]

The NTSB has a set of pictures of the vertical stabilizer and the empennage attachment points at:
http://www.ntsb.gov/Events/2001/AA587/tailcomp.htm

From the presswires:
NEW YORK (AP) - American Airlines Flight 587 twice ran into turbulence left by a jumbo jet, including a blast of air that sent it
careening sideways seconds before it crashed, investigators said Thursday.

The doomed plane's flight data recorder indicates the Airbus A300 had two turbulent "wake encounters'' during its three-minute
flight, said Marion Blakey, chairwoman of the National Transportation Safety Board.
"The second was similar in intensity to the first,'' she said.

Flight 587 began banking hard with its left wing down within eight seconds of the second wake encounter, said Tom Haueter, the NTSB's deputy director of aviation. The flight data recorder cut off at that point.

"Obviously, the whole time we're talking about is the last eight seconds,'' he said. "We have eight seconds we're going to be
looking at in extreme detail.''

Earlier, NTSB investigator George Black Jr. said investigators were almost certain the tail broke off before the jetliner's twin
engines. While cautioning that investigators are not ready to rule out sabotage, he said the tail "doesn't appear to have been sabotaged in any way.''

Black also said the pilots of Flight 587 were probably unaware its tail fin had broken off as they struggled to control the plane.

"They don't have a rearview mirror,'' he told The Associated Press. "They have no idea they've lost a tail.''

In Washington, the Federal Aviation Asministration was preparing to order inspections of Airbus A300s, focusing on the tail. The order would cover 90 of the European-built planes used by three U.S. airlines - American, FedEx and United Parcel Service. American has already agreed to do voluntary inspections of its 34 remaining A300s."

[Cisco Kid]

Wino, By a "Fix" do you mean merely increasing approach speeds or was the Yaw Damper system modified?,I don´t know & am just curious.As you may know a similar "Fix" has been applied to A319/320 A/C. After a "landing".. when a low go around had been commanded,A/C remained in landing flare...software problems!,so until it´s really corrected add 10 kts,& use a reduced flap setting for ldg. in gusty conditions.Real "fixes" would be nice,I don´t believe in conspiracies either;Cisco.

[Willie Everlearn]

I was wondering if this latest FAA inspection mandate for the A300 in the US shouldn't include the A310, A330 and A340.
Do they all not have the same or very similar Vertical Stab including attachment design???

[boofhead]

Of course I dunno the facts but it seems unlikely that the Airbus was going fast enough, so soon after takeoff, for it to break up in any sort of turbulence, or pio.
But I was told by an old and boldy when I first flew the classic 747 that if I was to over-react to an engine failure by using too much rudder, too quickly, engine pods would start breaking away, especially in cruise flight. The inference was that one should not jam in full control at high speed. If this airplane had some existing vert stab damage, it might have been susceptible to failure if the crew did use full rudder, even at 250 knots.

[ 16 November 2001: Message edited by: boofhead ]

[TechFly]

I suppose a combination of "fatigue/aeroelasticity/cycles/construction type" together with the aerodynamic flow encounter (i.e. high energy vortex) may give an overall answer or contribution to the disaster.

We will remember all of them forever.

Thanks to everybody around the world for contributing and detailing.

Cheers

[chillpill]

If we are talking about fatigue of the vertical stabilizer, irrespective of its construction being composite or conventional, has anyone ever noted the considerable vertical movement of the B757 horizontal stabilizer when take off power is applied and felt by this control surface. The more eagle eyed may have noted that the larger exhaust cone exit of the RB211 efflux causes considerable more movement to the stabilizer surface than the alternative engine CFM with a multi cone exit. Has Mr B noted this in the B757 fatigue test bed airframe?

[pigboat]

What are the Dutch roll characteristics of an aircraft that has just lost it's vertical stab? Sounds to me that after the loss of the fin, any Dutch roll may have progressed to the point where the aircraft may have actually snap rolled. That'd explian why both engines were pulled off the pylons. In that scenario, wake turbulence would indeed have exacerbated the initial rolling action.

[Deaf]

Boofhead

Don't forget the 250kts, if that was the speed, would be close to the IAS and that is essentially the IAS (and associated forces) of cruise at altiude.

[Charlie O]

A composite or honeycomb structure may have its strength reduced by the actions of high altitude to low altitude operation. Any space, no matter how small, in which air might be enter, will eventually lead to material separation. This can include microscopic cracks created by prior operational stresses, which might be easily overlooked by inspectors.

When an A/C changes from low temperature, high altitude operation (cruise) to a low level, low altitude condition (landing), the low pressure inside the composite material with microscopic cracking will draw in air, which will accumulate water inside due to condensation created by the cold interior. With a return to high altitude, low temperature operation, the water will freeze inside and NOT be expelled on landing.

With repeated cycles of low pressure, low temperature operation to areas of high humidity and high pressure, water can accumulate inside a composite material which has spaces in which air can enter. Eventually water will accumulate in these spaces until its freezing will can cause separation of the composite material.

Enough of these microscopic (internal and unseen) seperations and operational cycles may lead to complete failure of the composite assembly during "normal" operation. The same process has already caused the failure of many (vented) honeycomb structures in the past. No proof for the present accident, just another theory based on physical facts.

[moggie]

Wino- The rudder PFCU on the B737 was not "Fixed" but flight techniques were developed which reduced the risks inherent in the poor design. Note however, that the NG version has been fixed, although no changes to the classics took place.

It was not just 2 out of 3500 aircraft - there have been others (as I said in my last post, at least 1 at BA and other "unexplained" problems have occurred at toher operators.

Still no explanation as to why B737 and 747 fuel pumps have not been sorted - none of them were grounded - just asked to fly with a bit of uel in the tanks to keep the pumps cool. Now that sounds like a good idea to me - much cheaper than actually fixing the problem.

If you read my post it is not about how the FAA react but the outcry form the anti-European lobby every time a european built aircraft has a problem. I do remember the FAA grounding DC10s, but I don't recall the pro-Boeing lobby asking for B737 and 747 to be grounded when they hit a problem. Who called for the MD 80/83 etc. series of aeroplanes to be grounded after the Alaska crash? No-one west of Shannon, that's who!

[SaturnV]

A-310's are to be inspected as well. It does seem the authorities and experts are still deciding how best to inspect for voids or delamination in the composite structure.

Excerpted from the Nov 16 New York Times:
"American Airlines said on Wednesday that it would inspect its 34 surviving Airbuses. John L. Hotard, a spokesman for the airline, said yesterday that it was still planning how to carry out the inspections. The part to be inspected most carefully is a section at the base of the tail fin that was torn apart.

"The [FAA] order is expected to cover the 91 A300's registered in this country and another 46 A310's, which are similar but shorter planes. It will give the operators about 10 days to inspect the tails.

"The shaking incident evidently followed the encounter with the wake, but the connection is not yet clear. Airplanes leave two wakes behind them, disturbances in the air that resemble horizontal tornadoes, one trailing each wingtip. The plane that crashed bumped over the first one about 28 seconds before the flight data recorder stopped working, and the second one about 8 seconds before the data ended.

"In the first seconds after clearing the second wake, "the airplane appears to be consistent with flight control inputs," said Thomas Haueter, the board's deputy director of aviation safety, meaning that the plane's performance still matched the pilot's working of the controls.

"But shortly after that second encounter with a wake vortex, the plane was shaken laterally, changing its direction suddenly and forcefully. Forces on the plane are measured in G's, with one G being equal to the normal force of gravity.

"In mere seconds, passengers felt a sudden powerful swing in one direction, and then another slightly more forceful one in the same direction. They were being hit with forces 30 or 40 percent as strong as the normal force of gravity. (In contrast, the bumps from the wake vortices were equal to only 10 percent of the force of gravity, Mr. Haueter said; he said that the 10 percent was
"the type that sloshes your drink."

"Investigators said the plane's rudder moved in concert with the swings, apparently causing the sideways movements, but Mr. Haueter said investigators were looking into whether the rudder had moved on its own or the pilots had manipulated it. Then, in the last 2.5 seconds or so that the data recorder was still working, the plane lurched wildly to the side, its left wing lowered and its nose pitched forward. The drop to the ground had begun.

"Despite witness accounts to the contrary, Mr. Haueter also said that there was no evidence of any fire in the engines before impact."

Excerpted from the Nov 16 Washington Post:

"According to information released by Blakey today, this was what happened during the last seconds before the flight data recorder stopped working:

"• The American Airlines plane moved abruptly in a way consistent with hitting wake turbulence, but was not affected in any significant way. A similar movement occurred seconds later. Again, the plane was not significantly affected. The force of the encounters were about 10 percent of the force of gravity, certainly enough for passengers to notice but not particularly
dangerous.

"• About one second after the second wake turbulence encounter, and eight seconds before the recorder cut off, the plane made a violent movement to the right, jerking passengers sideways at about 30 percent of the force of gravity. It then made an even more abrupt move to the right, affecting
passengers with about 40 percent of the force of gravity. Then it moved left at about 30 percent the force of gravity. The data show that the rudder moved abruptly at the time of each movement. "This was a very significant lateral acceleration," Blakey said.

"The board said the rudder pedals in the cockpit moved in tandem with the rudder itself. That would almost always mean that the pilots induced the movements by pushing the rudder pedals. At this point, however, investigators cannot rule out some other explanation, including an autopilot malfunction or, perhaps, events that may never have happened before. The rudder -- the movable flat plate at the rear of the vertical tail fin -- is seldom used in flight
except when an engine fails, or to keep the plane from fishtailing in turbulence or when coming out of turns.

"• At 2.5 seconds before the end of the tape, rudder data on the recorder became "unreliable," possibly because the rudder had cracked off.

"• Side pressure increased to 80 percent of the force of gravity, and the plane rolled left to 25 degrees left-wing down as the nose pitched down 30 degrees. Passengers were pushed down into their seats at twice the force of gravity. The recorder cut off at that point.

"According to accident and incident records, at least two other A300-600s have
experienced serious in-flight emergencies, one apparently crew-induced and one
caused by an autopilot malfunction.

"On May 12, 1997, an American Airlines aircraft went through a series of violent maneuvers somewhat similar to Flight 587's as it prepared to land in Miami. The safety board determined that the crew first had inadvertently allowed the plane to stall, then mishandled the plane's recovery. The aircraft landed safely at West Palm Beach, Fla., but seven passengers and crew members
were injured.

"On May 17, 1999, an American Airlines plane experienced uncommanded rudder movements. The crew was unable to move the rudder with the foot pedals but used other controls to make the landing. The problem was caused by the autopilot."

[ 16 November 2001: Message edited by: SaturnV ]

[moggie]

Coincidentally, there are two post on "tech Log" about Boeing fuel pumps/wiring and B737 rudder PFCUs. Now, if the FAA has just decided that B737 rudders DO actually need to be fixed properly, why have they been happy to let them fly for the last 5 years in an unsafe state? If it needs fixing, it needs fixing NOW and not over the NEXT 5 YEARS as proposed.

Concorde was grounded and fixed straigh away - after the Air France crash (and I agree that it needed doing) but more people have died in the TWA 800 and the B737 hardover accidednts (not mentioning Alaskan MDs) than in the Concorde/A300 crashes.

I think consistency is what we need.

[gaunty]

allianceair

I think it was on one of the news sites if not an aviation news site.

I do not write for any newspaper. PERIOD. end of story.

I will for my own peace of mind go see if I can find it again, sorry to disappoint you but I am not in the habit of imagining these things either.

[gaunty]

In any event there has always been controversy surrounding all composite main structures.
Beech tried with their ill fated all composite Starship. They were an outstanding failure insofar as the market was concerned and if my memory serves me correctly a presurisation fuselage test article failed catastrophically without any/or the sort of warning you get with impending failure in metal.
Failure prediction in composites as far as I am aware is not an exact science, unless it has become so in recent times.
Boeing and other large manufacturers take a much more conservative approach in there use.
I dont work for Boeing or any of the others either.

I think Pandoras box has just been opened.