New Theory and Speculation On AA A300 Crash In New York
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I just talked to a friend of mine that went to the APA meeting in Miami. The latest information that the guys on our accident investigation team have is that the speed of the rudder oscillation was such that it could not have been made by the pilot. He simply would not have been able to move his feet that fast. They timed the rudder movement using CFR data and came up with some rediculously high number. This is consistent with rudder events concerning American A300's at both Miami and Lima.
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Long time before I was born, revolutionary airplanes called COMET started to fall out of the skies. What has happened ?. .I try to recall some facts : engineers and designers have overlooked the fact that square passenger window frames with "sharp" corners in a cyclic pressurized vessel were the fatal origin of subcritical crack growth within the aluminum frame (oh yes aluminum !). The learning process started..... .Did anybody subsequently ban aluminum as a structural material to be used in modern airplanes ? No, people started to learn from those accidents.. .Ever heard of fracture mechanics and life time prediction ?. .This highly developed sience and technology is one of the fundamentals of our daily civilized life in cars, on bridges, sky scrapers, trains ..... and of course airplanes !
I am very new to the pilots business, flying as an F/O on a Jet since nearly 6 months for a big european airline an I enjoy it very much(no, not on an Airbus !). However, within the composites science and technology I have more than 10 years of profound experience especially in the area of fracture mechanics and reliability.. .I have followed this topic since this tragic event. With my little experience of flying jets I am not at all in the position to comment on the flying aspects of this accident.. .I have read many of my fellow ppruner statements concerning the materials and design issues and must say that most of it is just a mirror of pure incompetence and lack of solid scientific and technical education and understanding.
The knowledge base of fracture mechanics and life prediction within large composite structures is due to historical reasons not as big as with metals. Nevertheless, before anybody of our "hobby-experts" within this forum will come to the final composite bashing conclusion, let us stand by for the final crash investigation report.. .The learning process will start again.....
No design has ever been and will ever be 100% fool proof. Everybody who can not live with this fact, should get out of the plane and look for an other job.
CB
I am very new to the pilots business, flying as an F/O on a Jet since nearly 6 months for a big european airline an I enjoy it very much(no, not on an Airbus !). However, within the composites science and technology I have more than 10 years of profound experience especially in the area of fracture mechanics and reliability.. .I have followed this topic since this tragic event. With my little experience of flying jets I am not at all in the position to comment on the flying aspects of this accident.. .I have read many of my fellow ppruner statements concerning the materials and design issues and must say that most of it is just a mirror of pure incompetence and lack of solid scientific and technical education and understanding.
The knowledge base of fracture mechanics and life prediction within large composite structures is due to historical reasons not as big as with metals. Nevertheless, before anybody of our "hobby-experts" within this forum will come to the final composite bashing conclusion, let us stand by for the final crash investigation report.. .The learning process will start again.....
No design has ever been and will ever be 100% fool proof. Everybody who can not live with this fact, should get out of the plane and look for an other job.
CB
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I flown in a lot of bad turbs -- over Japan (egads the pressure lines get bad over there, as well as 12 seconds behind KC-135s during heavy minimum interval takeoffs during the Cold War. I've also experienced a full rudder hardover on a KC-135 that was strong enough to bounce my head of the side window, but the aircraft sustained NO damage. There is NO WAY that any of that should be able to cause catastrophic structural failure. . .This is starting to smell like a controls design problem and maybe a weak structure to boot.
There was a test B-52 many years ago that sustained almost complete loss of the vertical stab. The details there were they were deliberatly out looking for mountain wave turbulence over the Rocky Mountains, and found it in spades. They lowered the landing gear for additional yaw stability and landed safely.
If there's any US govt agency associated with aviation that competent, it's the NTSB. Let's wait for their report.
[ 26 January 2002: Message edited by: Roadtrip ]</p>
There was a test B-52 many years ago that sustained almost complete loss of the vertical stab. The details there were they were deliberatly out looking for mountain wave turbulence over the Rocky Mountains, and found it in spades. They lowered the landing gear for additional yaw stability and landed safely.
If there's any US govt agency associated with aviation that competent, it's the NTSB. Let's wait for their report.
[ 26 January 2002: Message edited by: Roadtrip ]</p>
Very interesting story about the B-52 vertical stab. This was all I could find about it, anyone got any other information about this incident?
B-52 Vertical Tail Failure
A B-52 lost about 75 percent of its vertical stabilizer and rudder while flying at 350 knots indicated airspeed (KIAS) at a pressure altitude of 14,300 feet msl 5.4 miles east of Spanish Peak in Colorado, on January 10, 1964. The ground elevation was about 8,500 feet. The mountain top level was 13,500 feet. Boeing calculates the angular velocity at .66 radians per second for this event. Maximum gusts exceeded 140 feet per second.
B-52 Vertical Tail Failure
A B-52 lost about 75 percent of its vertical stabilizer and rudder while flying at 350 knots indicated airspeed (KIAS) at a pressure altitude of 14,300 feet msl 5.4 miles east of Spanish Peak in Colorado, on January 10, 1964. The ground elevation was about 8,500 feet. The mountain top level was 13,500 feet. Boeing calculates the angular velocity at .66 radians per second for this event. Maximum gusts exceeded 140 feet per second.
Ecce Homo! Loquitur...
You might also read up on the history of the English Electric Lightning. The F1 and F2 had a round topped fin. From the f3 onwards this was replaced with a larger square top fin.
I seem to recall the problem was a high speed flutter mode in which the fin failed and separated from the aircraft. Happened on several occasions before the redesign.
I seem to recall the problem was a high speed flutter mode in which the fin failed and separated from the aircraft. Happened on several occasions before the redesign.
Did find a little more on that B-52.
B-52H-170-BW S/N 61-0023 From a famous series of photographs taken after severe turbulence sheared off most of the vertical stabilizer. The aircraft had been specially instrumented for air turbulence research after some operational B-52s were lost. The tail was lost after a severe and sustained burst (+5 seconds) of clear air turbulence violently buffeted the aircraft. The Boeing test crew (Pilot - Chuck Fisher & Copilot - Dick Curry) nursed to aircraft to Blytheville AFB, Arkansas and landed safely. Also note the (inert) AGM-28 Hound Dog missiles still attached to the wing pylons. The dotted line shows the normal outline of the vertical stabilizer and rudder.
B-52H-170-BW S/N 61-0023 From a famous series of photographs taken after severe turbulence sheared off most of the vertical stabilizer. The aircraft had been specially instrumented for air turbulence research after some operational B-52s were lost. The tail was lost after a severe and sustained burst (+5 seconds) of clear air turbulence violently buffeted the aircraft. The Boeing test crew (Pilot - Chuck Fisher & Copilot - Dick Curry) nursed to aircraft to Blytheville AFB, Arkansas and landed safely. Also note the (inert) AGM-28 Hound Dog missiles still attached to the wing pylons. The dotted line shows the normal outline of the vertical stabilizer and rudder.
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I note that the rudder and the vertical stab landed separately in the bay. I would have thought that they would be firmly attached to each other with hinges etc. Does anyone know if the rudder actuator reacts against the tail of the fuselage or the vertical stabilizer?
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Airbus fin and rudder are connected by 7 hinges, 3 of them are also used by the actuators which react to the fin, not to the fuselage.
All 3 Actuators are installed closed together in one gropp at about 40% of the fin height. The rudder front spar broke between upper and middle actuator attach point. These attach brackets are also made of composites mainly from CFRP but also from GFRP in the reinforced area of the actator attach bushing (to prevent galvanic corrosion). The fittings are riveted to the rudder front spar by use of multiple <a href="http://www.huckaerospace.com/products/threaded/hilok/" target="_blank"> HiLok </a>shear pins. (26 HiLoks for the uppermost hinge, don´t know the exact number for the others but it will be some more at the actuator attach brackets). .There is only 1 hinge in the lower rudder area but 3 above the actuators. This lower hinge (let´s call it No. 1) seems to broken at the hinge pin, No. 6 is broken at the fins aft spar attach point. All other 5 hinges failed in the HiLok connection from the composite brackets to the composite ruder spar. This can be seen clearly in the NTSB videotape.
Seems to me the key lies somewhere in this rudder from fin separation and the damage to the rudder in the actuator attach area, but I still wonder what could be the first part that failed.
All 3 Actuators are installed closed together in one gropp at about 40% of the fin height. The rudder front spar broke between upper and middle actuator attach point. These attach brackets are also made of composites mainly from CFRP but also from GFRP in the reinforced area of the actator attach bushing (to prevent galvanic corrosion). The fittings are riveted to the rudder front spar by use of multiple <a href="http://www.huckaerospace.com/products/threaded/hilok/" target="_blank"> HiLok </a>shear pins. (26 HiLoks for the uppermost hinge, don´t know the exact number for the others but it will be some more at the actuator attach brackets). .There is only 1 hinge in the lower rudder area but 3 above the actuators. This lower hinge (let´s call it No. 1) seems to broken at the hinge pin, No. 6 is broken at the fins aft spar attach point. All other 5 hinges failed in the HiLok connection from the composite brackets to the composite ruder spar. This can be seen clearly in the NTSB videotape.
Seems to me the key lies somewhere in this rudder from fin separation and the damage to the rudder in the actuator attach area, but I still wonder what could be the first part that failed.
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Volume - Your knowledgeable remarks about the rudder actuators are tantalizing. I am having difficulty visualizing how the three actuators work independently & together at the same time. A sketch or pix would be sooo helpful.
One guesses that the actuators are push-me pull-you variety, each with authority to command some arc of movement. How do they keep out of each others' way? What mechanism negotiates the battle if each of the three wants to move in a different way, and what does THAT lever against? And how does IT fail?
This is probably a dumb question - my coffee to sleep ratio is runnng way too high right now. Your specific knowledge of rudder details seems like a beacon in the fog that surrounds this.
One guesses that the actuators are push-me pull-you variety, each with authority to command some arc of movement. How do they keep out of each others' way? What mechanism negotiates the battle if each of the three wants to move in a different way, and what does THAT lever against? And how does IT fail?
This is probably a dumb question - my coffee to sleep ratio is runnng way too high right now. Your specific knowledge of rudder details seems like a beacon in the fog that surrounds this.
I am a figment of my own imagination
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One point raised in the thread with regard to a second vortice caught my attention having experienced it. In a light jet 10 miles in trail of a 74 configured for landing we hit his vortices and were spun violently onto one wingtip. Having recovered, and before there was time to even make a comment about what had just happened, we were spun just as violently in the opposite direction. Luckily no injuries and plane sustained no damage but very thought provoking. . . In 72 dutch roll training we were instructed to keep firmly away from the rudder.
Ecce Homo! Loquitur...
Date: 06/06/1994. ."The NTSB has said the yaw damper on the doomed American 587 flight in New York had to be re-set before the crew could push back from the gate the morning it crashed......
However, an American Airlines Airbus preparing to land in Miami after a flight from Bogota, Colombia, on May 11, 1999, experienced control problems that were traced to the yaw damper.
An FAA report said that when the plane aborted the landing and flew over the airport, "the yaw deviations increased and became extreme." The plane landed safely.
The NTSB has said two wires in the yaw damper had been inadvertently reversed. The FAA issued a directive which appears to have corrected the problem".
and
"Location: Xi'an, China. .Airline: China Northwest Airlines. .Aircraft: Tupolev TU-154M. .Registration: B-2610. .Fatalities/No. Aboard: 160:160. .Details: The plane broke-up in flight 10 minutes after taking off. Auto-pilot induced oscillations caused the aircraft to shake violently. The autopilot yaw-channel was accidentally connected to the bank control and the bank-channel to the yaw controls".
Without implying this was in any way the same problem, it does show that faulty or incorrect wiring can induce an output capable of causing an aircraft to exceed limits and break up.
[ 06 February 2002: Message edited by: ORAC ]</p>
However, an American Airlines Airbus preparing to land in Miami after a flight from Bogota, Colombia, on May 11, 1999, experienced control problems that were traced to the yaw damper.
An FAA report said that when the plane aborted the landing and flew over the airport, "the yaw deviations increased and became extreme." The plane landed safely.
The NTSB has said two wires in the yaw damper had been inadvertently reversed. The FAA issued a directive which appears to have corrected the problem".
and
"Location: Xi'an, China. .Airline: China Northwest Airlines. .Aircraft: Tupolev TU-154M. .Registration: B-2610. .Fatalities/No. Aboard: 160:160. .Details: The plane broke-up in flight 10 minutes after taking off. Auto-pilot induced oscillations caused the aircraft to shake violently. The autopilot yaw-channel was accidentally connected to the bank control and the bank-channel to the yaw controls".
Without implying this was in any way the same problem, it does show that faulty or incorrect wiring can induce an output capable of causing an aircraft to exceed limits and break up.
[ 06 February 2002: Message edited by: ORAC ]</p>
Iconoclast
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On the A-310 it is possible to cross connect the cannon plugs on the Power Control Units, the PPUs both wing tip and PCU the wing tip brakes and the Command Sensor Unit. Not with each other, but within themselves. If the PPUs are cross connected the systems (flap and/ or slat system will lock up. If the Command sensor unit is cross connected nothing bad will happen but if a problem arises the troubleshooting will be extremely difficult and if the solenoids on the PCU are mismatched the system will not operate properly and things could happen out of sequence.
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Before all is said and done, this is going to get a lot more intensive, and the press will add the fuel. Check out
<a href="http://www.usatoday.com/news/nation/2002/02/06/usat-rudder.htm#more" target="_blank">http://www.usatoday.com/news/nation/2002/02/06/usat-rudder.htm#more</a>
<a href="http://www.usatoday.com/news/nation/2002/02/06/usat-rudder.htm#more" target="_blank">http://www.usatoday.com/news/nation/2002/02/06/usat-rudder.htm#more</a>
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NTSB Advisory. . National Transportation Safety Board. . Washington, DC 20594
. .February 7, 2002
NTSB CHAIRMAN TO HOLD PRESS BRIEFING FRIDAY. .UPDATING FLIGHT 587 INVESTIGATION
WASHINGTON, D.C. - National Transportation Safety Board Chairman Marion C.. .Blakey will hold a press briefing tomorrow to provide an update on the. .Board's investigation into the November 12, 2001 crash of American Airlines. .flight 587.
WHAT: News Conference on flight 587.
WHO: NTSB Chairman Marion C. Blakey
WHEN: Friday, February 8, 2002. .11:00 a.m.
WHERE: NTSB's Board Room and Conference Center. .429 L'Enfant Plaza, S.W., Washington, D.C.
. .February 7, 2002
NTSB CHAIRMAN TO HOLD PRESS BRIEFING FRIDAY. .UPDATING FLIGHT 587 INVESTIGATION
WASHINGTON, D.C. - National Transportation Safety Board Chairman Marion C.. .Blakey will hold a press briefing tomorrow to provide an update on the. .Board's investigation into the November 12, 2001 crash of American Airlines. .flight 587.
WHAT: News Conference on flight 587.
WHO: NTSB Chairman Marion C. Blakey
WHEN: Friday, February 8, 2002. .11:00 a.m.
WHERE: NTSB's Board Room and Conference Center. .429 L'Enfant Plaza, S.W., Washington, D.C.
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"Final" wake vortex?. .LL ATCO here, question?. .We have been talking recently about the application of wake vortex spacing at LL when crossing behind heavy traffic to get on to the other runway. Early in the morning, for example, the traffic is all heavy and we are often asked to use both runways requiring some crossing over (Inevitably some traffic from the north wants the southerly runway and vice versa).
I have always interpreted our book to demand the application of "Final Approach" w/v spacings when crossing behind traffic onto the other runway, even if still on "Base Leg" i.e. not actually on Final Approach. Irrespective of what the book actually says, it seems to me to be a most sensible precaution to apply Final Approach w/v spacings once the lead aircraft has begun to configure for the Final approach.
However, I now discover that not all agree and some ATCOs only apply Final spacing when actually on final. Having discussed the matter with many and varied it seems that our book is not absolutely clear on this point. I was wondering what our pilot friends thought on the issue. What do you think you are getting and what do you think you should get? If I am wrong then it is legal to cross a LR35, 3 miles behind a B757 at the same level for the other runway, when I would have to use 6 miles if approaching the same runway.
Anybody care to comment?
Point 4
I have always interpreted our book to demand the application of "Final Approach" w/v spacings when crossing behind traffic onto the other runway, even if still on "Base Leg" i.e. not actually on Final Approach. Irrespective of what the book actually says, it seems to me to be a most sensible precaution to apply Final Approach w/v spacings once the lead aircraft has begun to configure for the Final approach.
However, I now discover that not all agree and some ATCOs only apply Final spacing when actually on final. Having discussed the matter with many and varied it seems that our book is not absolutely clear on this point. I was wondering what our pilot friends thought on the issue. What do you think you are getting and what do you think you should get? If I am wrong then it is legal to cross a LR35, 3 miles behind a B757 at the same level for the other runway, when I would have to use 6 miles if approaching the same runway.
Anybody care to comment?
Point 4
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The more I read the happier I am that I am retired. Flying use to be fun. Now, golf is fun.. .The latest:
<a href="http://www.cnn.com/2002/US/02/08/ntsb.flight587/index.html" target="_blank">http://www.cnn.com/2002/US/02/08/ntsb.flight587/index.html</a>
<a href="http://www.cnn.com/2002/US/02/08/ntsb.flight587/index.html" target="_blank">http://www.cnn.com/2002/US/02/08/ntsb.flight587/index.html</a>