"A380 is a zero-crash aircraft" say Airbus
Unless it is established that Airbus did say what is alleged in the thread title, can I suggest removing the quotation marks as otherwise this reeks of the journalistic distortion of which this forum is so frequently and correctly critical.
If the actual statement was as per Greek God's quotation above, the provocative title (which, so far as I can see, is a subjective interpretation and not a quotation) would be a travesty of a more reasonable Airbus statement of design philosophy, presumably made by someone with a point of view to promote for whatever reason. Judging by some of the responses, many of the contributors to this debate seem to have swallowed the bait in classic Sun reader fashion.
If the actual statement was as per Greek God's quotation above, the provocative title (which, so far as I can see, is a subjective interpretation and not a quotation) would be a travesty of a more reasonable Airbus statement of design philosophy, presumably made by someone with a point of view to promote for whatever reason. Judging by some of the responses, many of the contributors to this debate seem to have swallowed the bait in classic Sun reader fashion.
Last edited by Max Tow; 26th Nov 2005 at 01:18.
Thread Starter
MT :
As the one who originated this thread with a link to a Dubai news article I can only point out it reads to start with :
'Passengers' safety on board A380 assured
Khaleej Times - 24/11/2005
DUBAI— The Airbus A380, which is considered as the world's largest long-haul airplane featuring two decks, four aisles and the capability to carry 600 to more than 800 passengers on board, is also a "zero-crash aircraft".
"Technology is what we master at Airbus. We just cannot afford to crash. The A380 has been designed to be a zero-crash aircraft and we made sure that it carries passengers safely to and from their destinations," said Jacky Joye, flight test engineer of Airbus......'
which looks to me like a quote, not a journalistic interpretation. Actually the article title "Passengers safety on board assured", which is indeed journalism, reads a lot better than the attributed quote.
Anyone know M. Joye well enough to ask ?
As the one who originated this thread with a link to a Dubai news article I can only point out it reads to start with :
'Passengers' safety on board A380 assured
Khaleej Times - 24/11/2005
DUBAI— The Airbus A380, which is considered as the world's largest long-haul airplane featuring two decks, four aisles and the capability to carry 600 to more than 800 passengers on board, is also a "zero-crash aircraft".
"Technology is what we master at Airbus. We just cannot afford to crash. The A380 has been designed to be a zero-crash aircraft and we made sure that it carries passengers safely to and from their destinations," said Jacky Joye, flight test engineer of Airbus......'
which looks to me like a quote, not a journalistic interpretation. Actually the article title "Passengers safety on board assured", which is indeed journalism, reads a lot better than the attributed quote.
Anyone know M. Joye well enough to ask ?
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Who says debate is dead? lol
FlapsOne, It was an excellent observation in that it made me laugh.
To everyone debating about the 319 that went hedge cutting, it was total pilot error, not even reheat could have got him outta that pickle. Just as they we're spooling up too... Trees really arn't good for Turbofans after all...
Hope eveyone takes things with a pinch of salt
AT
FlapsOne, It was an excellent observation in that it made me laugh.
To everyone debating about the 319 that went hedge cutting, it was total pilot error, not even reheat could have got him outta that pickle. Just as they we're spooling up too... Trees really arn't good for Turbofans after all...
Hope eveyone takes things with a pinch of salt
AT
WHBM
Without wishing to split hairs, if the correct quote is "DESIGNED TO BE a zero-crash aircraft", what's so controversial about that as an aim?
Wouldn't Boeing have the same philosophy?
Without wishing to split hairs, if the correct quote is "DESIGNED TO BE a zero-crash aircraft", what's so controversial about that as an aim?
Wouldn't Boeing have the same philosophy?
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Max Tow, I am glad Airbus finally decided to design an aircraft thats not meant to crash. Its taken a few years. I think all boeings since day 1 were designed to be zero crash aircraft (of course this hasnt been the case, but at least they had the right intentions)
Paxing All Over The World
This sounds like a technician who has been waylaid by a journo and has no idea how his well intentioned remarks will sound!!! The one that is really silly is:
I had not realised that the 380 had completed testing and is now certified ... 
We have tested the aircraft fully ...
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I am glad Airbus finally decided to design an aircraft thats not meant to crash
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As a fully paid-up member of English Pedantry I must protest at the ungrammatical nature of the expression "zero-crash". It should be "no-crash", "crash-proof" or "crashless". "Zero" is a cardinal number meaning nothing so it cannot be used in an adjectival sense.
What else can you expect when you let foreigners take over your language?!
Zero-crash ? Banzai!
edited for spelling (oops!)
What else can you expect when you let foreigners take over your language?!
Zero-crash ? Banzai!
edited for spelling (oops!)
Last edited by Wingswinger; 26th Nov 2005 at 19:07.
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Barit 1,
Sioux City comments noted.
However, AA 191 was lost as the result of a combination of maintenance error, maintenance management error and design certification error.
Sioux City comments noted.
However, AA 191 was lost as the result of a combination of maintenance error, maintenance management error and design certification error.
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Boeing philosophy is that the pilot is in control of the aircraft all the time, not computers, the automatics is there to help.
Is this entire thread not a testimony to the fact that too many pilots are not working hard enough and have too much time on their hands to pontificate about the minutaie of very little?
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There seems to be an enormous amount of b#ll#cks being written here about the Habsheim A320 accident, from people who should know better.
Some salient points, then:
The crew though they were at 100', but were actually at around 30', due to a failure of the altimeter system - hence their inability to clear the trees.
The captain had disconnected the autothrottles, and therefore had no alpha floor protection (maybe an Airbus pilot could comment on that, I don't know the type).
The reports of an independent air accident investigator, Ray Davies, cast doubt on whether the DFDR information that was included in the report was in fact from the DFDR that was on the accident aircraft. He also found disturbing evidence of a disagreement between the Captains pitch commands and the resultant elevator angle... I remember at the time of the two C4 programmes on the subject, it was suggested that some of the protections had been disabled to allow the display at all, and that the unusual configuration resulted in an incorrect pitch command by the computers. If you want to read more, a basic account can be found at http://www.cs.york.ac.uk/hise/safety...2002/0466.html
I remember at the time, the somewhat pompous Bernard Zeigler (AAI boss at the time), demonstrating an A320 (at altitude) in landing and GA modes, and saying that "it cannot be the aircraft, therefore it was the pilots fault".
I also seem to recall that the pilot concerned ended up in Australia, not prison (although many would say it is the same thing ) having had his French licence revoked on psychological grounds (presumably for questioning the reliability of the Airbus).
In any case, the whole affair stunk of corruption in high places, and a massive cover-up. I still have both C4 programmes on video, they make chilling viewing.
Anyway, my point is, check your facts before spouting such rubbish on PPRuNe.
Some salient points, then:
The crew though they were at 100', but were actually at around 30', due to a failure of the altimeter system - hence their inability to clear the trees.
The captain had disconnected the autothrottles, and therefore had no alpha floor protection (maybe an Airbus pilot could comment on that, I don't know the type).
The reports of an independent air accident investigator, Ray Davies, cast doubt on whether the DFDR information that was included in the report was in fact from the DFDR that was on the accident aircraft. He also found disturbing evidence of a disagreement between the Captains pitch commands and the resultant elevator angle... I remember at the time of the two C4 programmes on the subject, it was suggested that some of the protections had been disabled to allow the display at all, and that the unusual configuration resulted in an incorrect pitch command by the computers. If you want to read more, a basic account can be found at http://www.cs.york.ac.uk/hise/safety...2002/0466.html
I remember at the time, the somewhat pompous Bernard Zeigler (AAI boss at the time), demonstrating an A320 (at altitude) in landing and GA modes, and saying that "it cannot be the aircraft, therefore it was the pilots fault".
I also seem to recall that the pilot concerned ended up in Australia, not prison (although many would say it is the same thing
) having had his French licence revoked on psychological grounds (presumably for questioning the reliability of the Airbus).In any case, the whole affair stunk of corruption in high places, and a massive cover-up. I still have both C4 programmes on video, they make chilling viewing.
Anyway, my point is, check your facts before spouting such rubbish on PPRuNe.
atreyu- Which event are you referring to regarding the CBs???
Dr Dave...
TBC's rudder reversals were related to thermal shock on the dual acting servo causing jamming of the secondary servo and incorrect fluid porting according to the internal investigation done by TBC as a result of the continued investigation into UAL585, March 3. 1991, US427, September 8, 1994, and the serious incident of Eastwind 517. Both deals had correct parts/serviceable tolerances, as did Eastwind.
"National Transportation Safety Board
Washington, D.C. 20594
Safety Recommendation
Date: November 10, 1992
In reply refer to: A-92-118 through-121
Honorable Thomas C. Richards
Administrator
Federal Aviation Administration
Washington, D.C. 20591
On July 16, 1992, during a check of the flight controls in a United Airlines (UAL) Boeing 737-300, while taxiing to takeoff from Chicago-O'Hare International Airport, the captain discovered that the airplane's rudder pedal stopped at around 25-percent left pedal travel. The airplane returned to the gate and the main rudder power control unit (PCU) was removed.
The PCU was tested at UAL's maintenance facilities in San Francisco, California, on July 20, 1992. During that testing, the PCU operated in an anomalous manner. Under certain conditions, the actuator piston would move in a direction opposite to the commanded and intended input. However, during other demonstrations, the PCU operated normally.
As a result of the initial observations, the unit was taken to the facilities of Parker Hannifin, the valve manufacturer, at Irvine, California, for further testing by Boeing, Parker Hannifin, and UAL. Test results showed that the dual concentric servo valve installed on the main rudder PCU could, under some circumstances, result in motion opposite to that commanded by the rudder pedals. Boeing and Parker Hannifin then initiated a design review to better understand the nature of the reversal, to develop a design change to preclude the reversal, as well as a plan to implement the design change.
On July 30, 1992, the Safety Board became aware of the taxi incident at Chicago and the subsequent investigation of the PCU. Testing and design change efforts are continuing, and Safety Board specialists have participated in these efforts.
During subsequent testing of the rudder PCU, anomalous actions, ranging from sluggish movement of the actuator piston to full reversal in the commanded direction of piston travel, were observed when the input crank was held against the PCU body stops and the yaw damper piston was in the extend position. High internal fluid leakage was also noted. The capability of the PCU to produce force to move the rudder against aerodynamic loads was not measured. The interaction of the yaw damper and the PCU operation as observed is not fully understood. In addition, it is unknown whether the yaw damper was commanding rudder movement at the time that the UAL captain performed the rudder control check. During the tests, it was noted that lower hydraulic operating pressures aided in achieving anomalous actions. Tapping on the dual servo valve body or actuator summing levers prompted the PCU to return to normal operation. Releasing the force on the input crank also returned the PCU to normal operation.
In normal operation, the pilot applies force to the input crank through the rudder pedals. If the pilot releases pressure on the pedal when a direction reversal occurs, the tests show that the PCU should return to normal operation. However, it is highly unlikely that pilots would respond to a rudder reversal by releasing pedal pressure. If, as is for more likely, rudder pressure is held until the rudder has reversed position, the centering unit may supply sufficient force to the input crank to sustain the anomalous condition even though pedal pressure is released.
Analysis by Boeing and Parker Hannifin shows that the potential for rudder reversal could exist in all B-737 main rudder PCUs. The internal stops of the dual concentric servo valve can allow the secondary slide of some valves to overtravel under some conditions. Normally, the primary slide moves about 0.045 inch before the secondary slide moves. If the primary slide is pinned or jammed to the secondary slide, control inputs resulting in the normal movement of the primary slide can lead to the overtravel of the secondary slide. If the overtravel of the secondary slide is sufficient, hydraulic fluid could be routed through a flow passage located outside the normal valve travel range that could result in piston (and rudder) motion in the direction opposite to the input command.
According to Boeing and Parker Hannifin, the effects of an overtravel condition of the secondary slide would not be apparent during approved acceptance tests. Accordingly, one part of the acceptance test was modified to facilitate the investigation. During this rest, the primary and secondary slides were pinned together to prevent relative motion and were moved through an extended range of motion, as allowed by the internal secondary stops. This range of motion is greater than the normal range of motion of the secondary slide. As the overtravel progressed, the valve porting moved out of normal range, and the pressure and return porting to the respective slides of the actuator piston were interconnected and eventually reversed. The initial effect was excessive internal leakage. Full movement of the slide produced a 3,000 pounds per square inch (psi) reversed pressure drop across the actuator piston with the leakage slowed.
Boeing and UAL have developed a field test procedure to verify the proper operation of the dual servo valve. A total of 212 UAL B-737 airplanes were checked. One main rudder PCU was removed as a result of "hissing" sounds during part of the test. The source of these sounds was attributed to minor leakage in the PCU that was not associated with the dual servo valve. The unit passed acceptance tests and could have been returned to service. There were no other indications of abnormally operating PCUs during the fleet-wide checks. Tests and design analysis indicate that the anomalous operation will occur only when a unique condition prevents independent movement of the primary and secondary slides of the servo valve (a condition that could develop suddenly or occur intermittently). Thus, a onetime check may not ensure that reversal will not occur.
The dual servo valves removed from the B-737s that crashed in Colorado Springs, Colorado on March 3. 1991, and in the Darien Province of Panama on June 6, 1992, were also tested. The results show that a 50 percent pressure drop could have developed on the Colorado Springs unit if a failure mechanism produced an overtravel of the secondary valve slide. As understood thus far, if such a pressure drop occurred, the main rudder PCU could only develop 50 percent of the rudder hinge moment capability, working in the proper direction. The pressure drop would be similar to losing either A- or B redundant hydraulic systems. Moreover, the results show that a complete pressure drop, without reversal, could have developed on the Panama unit only if a failure mechanism produced an overtravel of the secondary slide valve. The unit would lose hinge moment capability, but movement of the rudder in the opposite direction beyond neutral would not occur.
Boeing aerodynamic data for the B-737-200 airplane shows that full rudder deflection (approximately 26 degrees) may be uncontrollable with full control wheel deflection (approximately 107 degrees) under certain conditions. Flap position and airspeed are important when determining controllability during full rudder deflection.
Historical maintenance data shows that there have been five other incidents related to the main rudder PCU. It is believed that two of them were detected in flight.
On July 24, 1974, the flightcrew of a: B-737 reported that the rudder moved "full right" on touchdown. The investigation revealed that the primary and secondary control valves were stuck together by a shot peen ball lodged in the valve.
On October 30, 1975, the flightcrew of a B-737 reported that the rudder pedals moved to the right "half-way" and then jammed. This action was repeated three times and then corrected by cycling the rudder with the standby rudder system. Further examination indicated that the system was contaminated by metal particles.
Another report on October 20, 1975, indicated that during a PCU inspection a jammed control valve was found. 'The data associated with this report is insufficient to determine the cause of the PCU removal.
On August 31, 1992, a B-737 reported that the rudder "locked up" on approach and that the flightcrew initiated a go-around and activated the standby rudder system. The landing was uneventful. The examination of the PCU revealed internal contamination and worn seals. It was suspected that high leakage from the worn seals resulted in the PCU having a limited capability to generate enough force to move the rudder.
On November 8. 1990, during an overhaul, a PCU was found to have internal corrosion. The primary slide was stuck at neutral to the secondary as a result of corrosion. There were no reports of malfunction prior to the disassembly.
Boeing and Parker Hannifin are currently developing design changes to the dual servo valve that would limit the travel of the secondary slide to eliminate the potential for pressure and return porting reversal. The Safety Board understands that the rudder PCUs would most likely be returned to Parker Hannifin for modification. Newly defined tolerances would require that parts from the dual servo valve be selectively fit and/or modified to produce acceptable test results. Boeing is planning a retrofit program.
...
NTSB recommends
Require that Boeing develop a repetitive maintenance test procedure to be used by B-737 operators to verify the proper operation of the main rudder power control unit servo valve until a design change is implemented that would preclude the possibility of anomalies attributed to the overtravel of the secondary slide. (Class 11, Priority Action) (A92-118)
Require that Boeing develop an approved preflight check of the rudder system to be used by operators to verify, to the extent possible, the proper operation of the main rudder power control unit servo valve until a design change is implemented that would preclude the possibility of rudder reversals attributed to the overtravel of the secondary slide. (Class II, Priority Action) (A-92-119)
Require operators, by airworthiness directive, to incorporate design changes for the B-737 main rudder power control unit servo valve when these changes are made available by Boeing. These changes should preclude the possibility of rudder reversals attributed to the overtravel of the secondary slide. (Class 11, Priority Action) (A-92-120)
Conduct a design review of servo valves manufactured by Parker Hannifin having a design similar to the B-737 rudder power control unit servo valve that control essential flight control hydraulic power control units on transport- category airplanes certified by the Federal Aviation Administration to determine that the design is not susceptible to inducing flight control malfunctions or reversals due to overtravel of the servo slides. (Class II, Priority Action) (A.92-121)
Chairman VOGT, Vice Chairman COUGHLIN, and Members LAUBER, HART, and HAMMERSCHMIDT concurred in these recommendations."
By: Carl W. Vogt
Chairman
no wrong parts.....
http://www.ntsb.gov/events/usair427/images.htm
http://ntsb.gov/Events/usair427/items.htm
http://www.ntsb.gov/events/usair427/docket/d206.pdf
http://www.ntsb.gov/Recs/letters/1999/A99_20_29.pdf
Simulation as an Atmospheric Motion Analysis Tool for Accident Investigation
http://www.ntsb.gov/publictn/2001/AAR0101.pdf
D. Crider, National Transportation Safety Board, Washington, DC
AIAA-2004-5034
AIAA Modeling and Simulation Technologies Conference and Exhibit, Providence, Rhode Island, Aug. 16-19, 2004
[numerical modelling of vortex entry by B737-200, using matlab simlink, sobering stuff]
at least the b737-800/900 servo depowering is better.
cheers
Dr Dave...
TBC's rudder reversals were related to thermal shock on the dual acting servo causing jamming of the secondary servo and incorrect fluid porting according to the internal investigation done by TBC as a result of the continued investigation into UAL585, March 3. 1991, US427, September 8, 1994, and the serious incident of Eastwind 517. Both deals had correct parts/serviceable tolerances, as did Eastwind.
"National Transportation Safety Board
Washington, D.C. 20594
Safety Recommendation
Date: November 10, 1992
In reply refer to: A-92-118 through-121
Honorable Thomas C. Richards
Administrator
Federal Aviation Administration
Washington, D.C. 20591
On July 16, 1992, during a check of the flight controls in a United Airlines (UAL) Boeing 737-300, while taxiing to takeoff from Chicago-O'Hare International Airport, the captain discovered that the airplane's rudder pedal stopped at around 25-percent left pedal travel. The airplane returned to the gate and the main rudder power control unit (PCU) was removed.
The PCU was tested at UAL's maintenance facilities in San Francisco, California, on July 20, 1992. During that testing, the PCU operated in an anomalous manner. Under certain conditions, the actuator piston would move in a direction opposite to the commanded and intended input. However, during other demonstrations, the PCU operated normally.
As a result of the initial observations, the unit was taken to the facilities of Parker Hannifin, the valve manufacturer, at Irvine, California, for further testing by Boeing, Parker Hannifin, and UAL. Test results showed that the dual concentric servo valve installed on the main rudder PCU could, under some circumstances, result in motion opposite to that commanded by the rudder pedals. Boeing and Parker Hannifin then initiated a design review to better understand the nature of the reversal, to develop a design change to preclude the reversal, as well as a plan to implement the design change.
On July 30, 1992, the Safety Board became aware of the taxi incident at Chicago and the subsequent investigation of the PCU. Testing and design change efforts are continuing, and Safety Board specialists have participated in these efforts.
During subsequent testing of the rudder PCU, anomalous actions, ranging from sluggish movement of the actuator piston to full reversal in the commanded direction of piston travel, were observed when the input crank was held against the PCU body stops and the yaw damper piston was in the extend position. High internal fluid leakage was also noted. The capability of the PCU to produce force to move the rudder against aerodynamic loads was not measured. The interaction of the yaw damper and the PCU operation as observed is not fully understood. In addition, it is unknown whether the yaw damper was commanding rudder movement at the time that the UAL captain performed the rudder control check. During the tests, it was noted that lower hydraulic operating pressures aided in achieving anomalous actions. Tapping on the dual servo valve body or actuator summing levers prompted the PCU to return to normal operation. Releasing the force on the input crank also returned the PCU to normal operation.
In normal operation, the pilot applies force to the input crank through the rudder pedals. If the pilot releases pressure on the pedal when a direction reversal occurs, the tests show that the PCU should return to normal operation. However, it is highly unlikely that pilots would respond to a rudder reversal by releasing pedal pressure. If, as is for more likely, rudder pressure is held until the rudder has reversed position, the centering unit may supply sufficient force to the input crank to sustain the anomalous condition even though pedal pressure is released.
Analysis by Boeing and Parker Hannifin shows that the potential for rudder reversal could exist in all B-737 main rudder PCUs. The internal stops of the dual concentric servo valve can allow the secondary slide of some valves to overtravel under some conditions. Normally, the primary slide moves about 0.045 inch before the secondary slide moves. If the primary slide is pinned or jammed to the secondary slide, control inputs resulting in the normal movement of the primary slide can lead to the overtravel of the secondary slide. If the overtravel of the secondary slide is sufficient, hydraulic fluid could be routed through a flow passage located outside the normal valve travel range that could result in piston (and rudder) motion in the direction opposite to the input command.
According to Boeing and Parker Hannifin, the effects of an overtravel condition of the secondary slide would not be apparent during approved acceptance tests. Accordingly, one part of the acceptance test was modified to facilitate the investigation. During this rest, the primary and secondary slides were pinned together to prevent relative motion and were moved through an extended range of motion, as allowed by the internal secondary stops. This range of motion is greater than the normal range of motion of the secondary slide. As the overtravel progressed, the valve porting moved out of normal range, and the pressure and return porting to the respective slides of the actuator piston were interconnected and eventually reversed. The initial effect was excessive internal leakage. Full movement of the slide produced a 3,000 pounds per square inch (psi) reversed pressure drop across the actuator piston with the leakage slowed.
Boeing and UAL have developed a field test procedure to verify the proper operation of the dual servo valve. A total of 212 UAL B-737 airplanes were checked. One main rudder PCU was removed as a result of "hissing" sounds during part of the test. The source of these sounds was attributed to minor leakage in the PCU that was not associated with the dual servo valve. The unit passed acceptance tests and could have been returned to service. There were no other indications of abnormally operating PCUs during the fleet-wide checks. Tests and design analysis indicate that the anomalous operation will occur only when a unique condition prevents independent movement of the primary and secondary slides of the servo valve (a condition that could develop suddenly or occur intermittently). Thus, a onetime check may not ensure that reversal will not occur.
The dual servo valves removed from the B-737s that crashed in Colorado Springs, Colorado on March 3. 1991, and in the Darien Province of Panama on June 6, 1992, were also tested. The results show that a 50 percent pressure drop could have developed on the Colorado Springs unit if a failure mechanism produced an overtravel of the secondary valve slide. As understood thus far, if such a pressure drop occurred, the main rudder PCU could only develop 50 percent of the rudder hinge moment capability, working in the proper direction. The pressure drop would be similar to losing either A- or B redundant hydraulic systems. Moreover, the results show that a complete pressure drop, without reversal, could have developed on the Panama unit only if a failure mechanism produced an overtravel of the secondary slide valve. The unit would lose hinge moment capability, but movement of the rudder in the opposite direction beyond neutral would not occur.
Boeing aerodynamic data for the B-737-200 airplane shows that full rudder deflection (approximately 26 degrees) may be uncontrollable with full control wheel deflection (approximately 107 degrees) under certain conditions. Flap position and airspeed are important when determining controllability during full rudder deflection.
Historical maintenance data shows that there have been five other incidents related to the main rudder PCU. It is believed that two of them were detected in flight.
On July 24, 1974, the flightcrew of a: B-737 reported that the rudder moved "full right" on touchdown. The investigation revealed that the primary and secondary control valves were stuck together by a shot peen ball lodged in the valve.
On October 30, 1975, the flightcrew of a B-737 reported that the rudder pedals moved to the right "half-way" and then jammed. This action was repeated three times and then corrected by cycling the rudder with the standby rudder system. Further examination indicated that the system was contaminated by metal particles.
Another report on October 20, 1975, indicated that during a PCU inspection a jammed control valve was found. 'The data associated with this report is insufficient to determine the cause of the PCU removal.
On August 31, 1992, a B-737 reported that the rudder "locked up" on approach and that the flightcrew initiated a go-around and activated the standby rudder system. The landing was uneventful. The examination of the PCU revealed internal contamination and worn seals. It was suspected that high leakage from the worn seals resulted in the PCU having a limited capability to generate enough force to move the rudder.
On November 8. 1990, during an overhaul, a PCU was found to have internal corrosion. The primary slide was stuck at neutral to the secondary as a result of corrosion. There were no reports of malfunction prior to the disassembly.
Boeing and Parker Hannifin are currently developing design changes to the dual servo valve that would limit the travel of the secondary slide to eliminate the potential for pressure and return porting reversal. The Safety Board understands that the rudder PCUs would most likely be returned to Parker Hannifin for modification. Newly defined tolerances would require that parts from the dual servo valve be selectively fit and/or modified to produce acceptable test results. Boeing is planning a retrofit program.
...
NTSB recommends
Require that Boeing develop a repetitive maintenance test procedure to be used by B-737 operators to verify the proper operation of the main rudder power control unit servo valve until a design change is implemented that would preclude the possibility of anomalies attributed to the overtravel of the secondary slide. (Class 11, Priority Action) (A92-118)
Require that Boeing develop an approved preflight check of the rudder system to be used by operators to verify, to the extent possible, the proper operation of the main rudder power control unit servo valve until a design change is implemented that would preclude the possibility of rudder reversals attributed to the overtravel of the secondary slide. (Class II, Priority Action) (A-92-119)
Require operators, by airworthiness directive, to incorporate design changes for the B-737 main rudder power control unit servo valve when these changes are made available by Boeing. These changes should preclude the possibility of rudder reversals attributed to the overtravel of the secondary slide. (Class 11, Priority Action) (A-92-120)
Conduct a design review of servo valves manufactured by Parker Hannifin having a design similar to the B-737 rudder power control unit servo valve that control essential flight control hydraulic power control units on transport- category airplanes certified by the Federal Aviation Administration to determine that the design is not susceptible to inducing flight control malfunctions or reversals due to overtravel of the servo slides. (Class II, Priority Action) (A.92-121)
Chairman VOGT, Vice Chairman COUGHLIN, and Members LAUBER, HART, and HAMMERSCHMIDT concurred in these recommendations."
By: Carl W. Vogt
Chairman
no wrong parts.....
http://www.ntsb.gov/events/usair427/images.htm
http://ntsb.gov/Events/usair427/items.htm
http://www.ntsb.gov/events/usair427/docket/d206.pdf
http://www.ntsb.gov/Recs/letters/1999/A99_20_29.pdf
Simulation as an Atmospheric Motion Analysis Tool for Accident Investigation
http://www.ntsb.gov/publictn/2001/AAR0101.pdf
D. Crider, National Transportation Safety Board, Washington, DC
AIAA-2004-5034
AIAA Modeling and Simulation Technologies Conference and Exhibit, Providence, Rhode Island, Aug. 16-19, 2004
[numerical modelling of vortex entry by B737-200, using matlab simlink, sobering stuff]
at least the b737-800/900 servo depowering is better.
cheers
Pegase Driver
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Interesting how 100 computers became 100 " Black boxes " then 100 FDR-CVR. and how a test flight engineer became the spokesman for Airbus .
Goog journalistic work I would say.
As to the bashing of Airbus , of course the 787 will have no automation whatsoever, and the 777 is cable driven
Goog journalistic work I would say.
As to the bashing of Airbus , of course the 787 will have no automation whatsoever, and the 777 is cable driven
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The crew though they were at 100', but were actually at around 30', due to a failure of the altimeter system - hence their inability to clear the trees
The captain had disconnected the autothrottles, and therefore had no alpha floor protection
I still have both C4 programmes on video, they make chilling viewing.
Anyone know M. Joye well enough to ask ?
I've followed this thread from the start and have seen some keen observations about just what contributes to a zero crash airplane. Most everything else in this thread is a debate about semantics.
Safety proffessionals don't care much about debating semantics and we certainly don't write news articles for the public. We do care about meaning however, and I'm happy to see that many on this forum have got that about right.
Now it's up to Airbus PR to clarify the meaning at least in the sense of fair marketing value.