NTSB and Rudders
Union Goon
Join Date: Feb 2000
Location: New Jersey, USA
Posts: 1,097
Likes: 0
Received 0 Likes
on
0 Posts
Yep thats exactly what I am saying.
The rudder load limiter in the A300 600 works by limiting the travel of the rudder pedals. The breakout forces are also increased .
On the ground the rudder pedals have a travel of around 8 inches in either direction. In flight the pedals are physically restricted from going further than the rudder travel required. So full throw of the rudder pedal around 250 knots is about 1 inch. The breakout force is higher than the force to reach the stop. so what happens is that the rudder becomes a toggle switch in flight. You get a choice of All or nothing. If you try and correct your all input from one side you will instantly go full travel the other way. There is no way to put in a coordinated amount of rudder without pushing with BOTH feet simultaneously to try and modulate the rudder. And it feels nothing like what you are used to when you are doing V1 cuts, crosswinds etc. Now who would push down with both feet if they didn't know?
They used to have a ratio type load limiter in the A300 b4 where normal travel at slow speed equaled normal pedal travel at high speed, with a different amount of rudder being applied so the rudder always feels the same. Boeing switched to that style of rudder load limiter from the 747 forward (IE 757 767 777) and depowered the rudder in the 727 and removed 1 completely from use so that though the 727 had a blocker limiter, force was also limited.
Some one mocked me for it, but the facts are Airbus had it right for the A300B4 and went wrong from there (All airbus rudders are blocker types)
Cheers
Wino
The rudder load limiter in the A300 600 works by limiting the travel of the rudder pedals. The breakout forces are also increased .
On the ground the rudder pedals have a travel of around 8 inches in either direction. In flight the pedals are physically restricted from going further than the rudder travel required. So full throw of the rudder pedal around 250 knots is about 1 inch. The breakout force is higher than the force to reach the stop. so what happens is that the rudder becomes a toggle switch in flight. You get a choice of All or nothing. If you try and correct your all input from one side you will instantly go full travel the other way. There is no way to put in a coordinated amount of rudder without pushing with BOTH feet simultaneously to try and modulate the rudder. And it feels nothing like what you are used to when you are doing V1 cuts, crosswinds etc. Now who would push down with both feet if they didn't know?
They used to have a ratio type load limiter in the A300 b4 where normal travel at slow speed equaled normal pedal travel at high speed, with a different amount of rudder being applied so the rudder always feels the same. Boeing switched to that style of rudder load limiter from the 747 forward (IE 757 767 777) and depowered the rudder in the 727 and removed 1 completely from use so that though the 727 had a blocker limiter, force was also limited.
Some one mocked me for it, but the facts are Airbus had it right for the A300B4 and went wrong from there (All airbus rudders are blocker types)
Cheers
Wino
Ecce Homo! Loquitur...
LA Times: July 28, 2002
WASHINGTON -- The crash of a jetliner in New York last year after its tail fin ripped off is prompting investigators to question whether government structural standards are tough enough, according to sources close to the inquiry.
Boeing Co. has informed federal investigators that the tail of its comparable Boeing 767 airliner would not have broken under the forces experienced by the Airbus A300-600, said three sources familiar with the investigation.
Both the Airbus and Boeing planes meet Federal Aviation Administration structural standards. But Boeing imposes two additional requirements for its tail fin design, beyond four that are mandated by the FAA, a company document indicates.......
Airbus said in a written statement that comparing Boeing planes with its own "can easily be misleading." The company did not respond to the specific question of whether its tail fin design goes beyond minimum FAA standards, citing trade secrets and NTSB rules barring disclosure of accident investigation data.
"The bottom line is this," the Airbus statement said. "While our designs are proprietary, the [tail fin] on the A300-600--as on all our aircraft--was designed and demonstrated to meet or exceed all certification criteria established by the FAA and European certification authorities".........................
FAA spokesman Les Dorr defended the agency's standards. "There is no information that has come out of the accident investigation to date that would cause us to think any change needs to be made to the requirements. Obviously, if any such information does come to light, we would review it and determine what the proper course of action should be." Dorr also warned against comparing planes built by different manufacturers.
NTSB experts are analyzing Boeing's findings about the strength of its 767 jetliner to see if the comparison is valid. They are "trying to understand the nuances and differences ... to see if [Boeing is] talking apples to apples," said one source close to the investigation......................
No conclusions have been reached.
"Boeing may have [an airplane] that is designed way above the standard, and Airbus may have one that is designed to the standard," said the source, who asked not to be identified. "There are design standards which people are supposed to meet. If someone breaks a tail, then there is an issue with those standards"............................
The FAA standards are intended to safeguard the tail fin from such forces as extreme gusts of wind or pilots aggressively using the aircraft's rudder............
The FAA's hypothetical maneuver is supposed to represent a worst-case scenario. A manufacturer must certify that its design is at least 50% stronger than the hypothetical worst case. This added safety margin is called "ultimate load." Engineers rely on mathematical calculations and data from various kinds of tests to certify to regulators that their designs will hold up under ultimate load.
Airbus has told NTSB investigators that its calculations indicate that Flight 587 experienced forces beyond the A300 design limits, its "ultimate load," said another source familiar with the investigation. But Boeing told the NTSB its engineers tested several scenarios that involved manipulating the rudder of its 767, and "it would appear to them that their loads were below ultimate," the source added. "If you are below ultimate, you wouldn't break the tail."
According to this source, Boeing obtained data on the forces experienced by the Airbus plane and then calculated the effects of those forces on its plane. The NTSB then asked Boeing to do additional tests.
"They tried to get the worst possible scenario, and they [were] getting loads below ultimate," said the source.
The Boeing standards raise the bar on what the FAA requires.
For example, the company calls for its aircraft to withstand full rudder in one direction followed by full rudder in the opposite direction. (The FAA only requires a full turn in one direction, followed by a quick return to neutral.)
"The net result of this approach is that there has been no catastrophic structural failure of a Boeing airplane due to pilot control input in 40 years of commercial operations involving more than 300 million commercial flights," Boeing said in a recent bulletin to pilots.
The NTSB has scheduled hearings in October on the crash. Agency officials have stressed that they are still considering a number of factors, including the actions of the pilots, the design of the tail fin , the operation of the rudder controls, possible preexisting problems with the plane and the performance of the advanced composite material used to build the tail. The NTSB has rejected a call by some American Airlines pilots to recommend grounding all Airbus A300s.
"There are a lot of unanswered questions at this point," Loeb said. "This is a very complicated investigation. The issue is not solely the structural capacity of the tail. It is a combination of that and the rudder control system."
If the crash leads to tougher design requirements, manufacturers literally would have to go back to the drawing board to plan costly changes to many existing aircraft. Another option would be to impose higher requirements on new aircraft, while advising pilots to exercise caution in flying older models...............
The full article can be found here, you need to register, but it's free:
LA Times
WASHINGTON -- The crash of a jetliner in New York last year after its tail fin ripped off is prompting investigators to question whether government structural standards are tough enough, according to sources close to the inquiry.
Boeing Co. has informed federal investigators that the tail of its comparable Boeing 767 airliner would not have broken under the forces experienced by the Airbus A300-600, said three sources familiar with the investigation.
Both the Airbus and Boeing planes meet Federal Aviation Administration structural standards. But Boeing imposes two additional requirements for its tail fin design, beyond four that are mandated by the FAA, a company document indicates.......
Airbus said in a written statement that comparing Boeing planes with its own "can easily be misleading." The company did not respond to the specific question of whether its tail fin design goes beyond minimum FAA standards, citing trade secrets and NTSB rules barring disclosure of accident investigation data.
"The bottom line is this," the Airbus statement said. "While our designs are proprietary, the [tail fin] on the A300-600--as on all our aircraft--was designed and demonstrated to meet or exceed all certification criteria established by the FAA and European certification authorities".........................
FAA spokesman Les Dorr defended the agency's standards. "There is no information that has come out of the accident investigation to date that would cause us to think any change needs to be made to the requirements. Obviously, if any such information does come to light, we would review it and determine what the proper course of action should be." Dorr also warned against comparing planes built by different manufacturers.
NTSB experts are analyzing Boeing's findings about the strength of its 767 jetliner to see if the comparison is valid. They are "trying to understand the nuances and differences ... to see if [Boeing is] talking apples to apples," said one source close to the investigation......................
No conclusions have been reached.
"Boeing may have [an airplane] that is designed way above the standard, and Airbus may have one that is designed to the standard," said the source, who asked not to be identified. "There are design standards which people are supposed to meet. If someone breaks a tail, then there is an issue with those standards"............................
The FAA standards are intended to safeguard the tail fin from such forces as extreme gusts of wind or pilots aggressively using the aircraft's rudder............
The FAA's hypothetical maneuver is supposed to represent a worst-case scenario. A manufacturer must certify that its design is at least 50% stronger than the hypothetical worst case. This added safety margin is called "ultimate load." Engineers rely on mathematical calculations and data from various kinds of tests to certify to regulators that their designs will hold up under ultimate load.
Airbus has told NTSB investigators that its calculations indicate that Flight 587 experienced forces beyond the A300 design limits, its "ultimate load," said another source familiar with the investigation. But Boeing told the NTSB its engineers tested several scenarios that involved manipulating the rudder of its 767, and "it would appear to them that their loads were below ultimate," the source added. "If you are below ultimate, you wouldn't break the tail."
According to this source, Boeing obtained data on the forces experienced by the Airbus plane and then calculated the effects of those forces on its plane. The NTSB then asked Boeing to do additional tests.
"They tried to get the worst possible scenario, and they [were] getting loads below ultimate," said the source.
The Boeing standards raise the bar on what the FAA requires.
For example, the company calls for its aircraft to withstand full rudder in one direction followed by full rudder in the opposite direction. (The FAA only requires a full turn in one direction, followed by a quick return to neutral.)
"The net result of this approach is that there has been no catastrophic structural failure of a Boeing airplane due to pilot control input in 40 years of commercial operations involving more than 300 million commercial flights," Boeing said in a recent bulletin to pilots.
The NTSB has scheduled hearings in October on the crash. Agency officials have stressed that they are still considering a number of factors, including the actions of the pilots, the design of the tail fin , the operation of the rudder controls, possible preexisting problems with the plane and the performance of the advanced composite material used to build the tail. The NTSB has rejected a call by some American Airlines pilots to recommend grounding all Airbus A300s.
"There are a lot of unanswered questions at this point," Loeb said. "This is a very complicated investigation. The issue is not solely the structural capacity of the tail. It is a combination of that and the rudder control system."
If the crash leads to tougher design requirements, manufacturers literally would have to go back to the drawing board to plan costly changes to many existing aircraft. Another option would be to impose higher requirements on new aircraft, while advising pilots to exercise caution in flying older models...............
The full article can be found here, you need to register, but it's free:
LA Times
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders
You can quote all the technical details about the operation of the A300 rudder but the rudder and its possible operation by the pilots is not relevant!
The 200+ mph force of the rotating vortices striking the FIN, (vertical stabilizer and the rudder), BROADSIDE resulted in an INSTANTANEOUS left YAW! A strong, abrupt left YAW will initiate an INSTANTANEOUS left Dutch roll! GONE MAN GONE!
The pilots were just along for the ride! They did hold full right aileron, but with little or no effect.
Eye witness statement, "The right wing was perpendicular to the ground"!!!!
The 200+ mph force of the rotating vortices striking the FIN, (vertical stabilizer and the rudder), BROADSIDE resulted in an INSTANTANEOUS left YAW! A strong, abrupt left YAW will initiate an INSTANTANEOUS left Dutch roll! GONE MAN GONE!
The pilots were just along for the ride! They did hold full right aileron, but with little or no effect.
Eye witness statement, "The right wing was perpendicular to the ground"!!!!
Union Goon
Join Date: Feb 2000
Location: New Jersey, USA
Posts: 1,097
Likes: 0
Received 0 Likes
on
0 Posts
Comeon Bill you got to be kidding me. We been over this on C&R.
Tell me again how it was windshear that caused the egypt Air 990, and shutting down the engines was the captain trying to save the ship.
I know someone played a dirty trick on you in the sim once but get real. The world has changed alot since your 707 days and the aircraft are very different.
So you opinion is that this is the very first time that anyone hit a 747 wake? If not where are all the other smoking holes.
They werent THAT close
Cheers
Wino
Tell me again how it was windshear that caused the egypt Air 990, and shutting down the engines was the captain trying to save the ship.
I know someone played a dirty trick on you in the sim once but get real. The world has changed alot since your 707 days and the aircraft are very different.
So you opinion is that this is the very first time that anyone hit a 747 wake? If not where are all the other smoking holes.
They werent THAT close
Cheers
Wino
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders
Your statement, "The .8 G loading was after the tail departed." is open to question!
At 16:04.5 Rudder data becomes unreliable. The NTSB states, "The FDR shows lateral acceleration increases to 0.8g, yaw rate of 10 deg/sec. left bank through 25 deg. with pilot applying right wheel, pitch down to -30 deg.! The perfect description of a Dutch roll! Eye witness statement, "The right wing was perpendicular to the ground"!!!
You state, "The other G loadings that you list are not enough to even require a write up under the new AD against the tail." These other G loadings serve to illustrate AA 587's path through the vortex beginning at the fringes and then transitioning through to the core of the vortices.
You state, "If you had been following along you would also know that there is a problem with the rudder load limiter on the A300." I must admit that I pay little attention to all these comments about the rudder system as I deem them irrelevant to the cause of this accident.
The main control surface involved is the total surface of the vertical stabilizer and the rudder. This large surface area is now the major flight control surface on the aircraft and when struck by an enormous force broadside to this surface there is no other maneuver possible except an instantaneous yaw motion!
The rudder movements were the result of these broadside hits, first on one side and then on the opposite side. There were no pilot inputs to the rudder relevant to this accident!
Fraternally
At 16:04.5 Rudder data becomes unreliable. The NTSB states, "The FDR shows lateral acceleration increases to 0.8g, yaw rate of 10 deg/sec. left bank through 25 deg. with pilot applying right wheel, pitch down to -30 deg.! The perfect description of a Dutch roll! Eye witness statement, "The right wing was perpendicular to the ground"!!!
You state, "The other G loadings that you list are not enough to even require a write up under the new AD against the tail." These other G loadings serve to illustrate AA 587's path through the vortex beginning at the fringes and then transitioning through to the core of the vortices.
You state, "If you had been following along you would also know that there is a problem with the rudder load limiter on the A300." I must admit that I pay little attention to all these comments about the rudder system as I deem them irrelevant to the cause of this accident.
The main control surface involved is the total surface of the vertical stabilizer and the rudder. This large surface area is now the major flight control surface on the aircraft and when struck by an enormous force broadside to this surface there is no other maneuver possible except an instantaneous yaw motion!
The rudder movements were the result of these broadside hits, first on one side and then on the opposite side. There were no pilot inputs to the rudder relevant to this accident!
Fraternally
Prefer to wait for wake vortex model
NASA is developing a wake vortex model at NTSB's behest.
We need that model to quantify effects on the sensors, entire a/c, fin and rudder control system that various transects of the wake vortices and region between would produce.
Until then, it's just speculation.
I notice that nobody seems to be in a hurry to fly an A300 or anything else through a low level 747 wake to research the accident profile -- can't say I blame them.
We need that model to quantify effects on the sensors, entire a/c, fin and rudder control system that various transects of the wake vortices and region between would produce.
Until then, it's just speculation.
I notice that nobody seems to be in a hurry to fly an A300 or anything else through a low level 747 wake to research the accident profile -- can't say I blame them.
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders
Reply to WINO post 600.
OK, I say again. Wind shear, from turbulence, across the
openings of the Pitot-Static System can cause low pressures which can induce erroneous flight instrument readings. Turbulence can also induce aircraft attitude transitions, (ask Captain Goode about his aircraft's attitude gyrations.) These triggers can induce instinctive pilot flight control inputs that may result in aircraft upset accidents! e.g., NWA 705, EgyptAir 990, SilkAir MI185, etc.,etc. (Reference to EgyptAir 990 accident)
I know the world has changed but the laws of physics have not. The B707 or the 767 still accelerate at the rate of G! Instantaneously! The Captain called for engine shut down after the aircraft was indicating .99 Mach! Incidently, the elevators did not split until after the .99 Mach point! (EgyptAir 990 accident)
This is the first time, in almost 100 years of flight, that we are aware of, that an aircraft has entered the core of a vortex behind a fully loaded B747 at climb power. (AA 587)
A little knowledge can be dangerous, but too much reliance on book learning can lead to obfuscation! Remember the basics!
Fraternally
OK, I say again. Wind shear, from turbulence, across the
openings of the Pitot-Static System can cause low pressures which can induce erroneous flight instrument readings. Turbulence can also induce aircraft attitude transitions, (ask Captain Goode about his aircraft's attitude gyrations.) These triggers can induce instinctive pilot flight control inputs that may result in aircraft upset accidents! e.g., NWA 705, EgyptAir 990, SilkAir MI185, etc.,etc. (Reference to EgyptAir 990 accident)
I know the world has changed but the laws of physics have not. The B707 or the 767 still accelerate at the rate of G! Instantaneously! The Captain called for engine shut down after the aircraft was indicating .99 Mach! Incidently, the elevators did not split until after the .99 Mach point! (EgyptAir 990 accident)
This is the first time, in almost 100 years of flight, that we are aware of, that an aircraft has entered the core of a vortex behind a fully loaded B747 at climb power. (AA 587)
A little knowledge can be dangerous, but too much reliance on book learning can lead to obfuscation! Remember the basics!
Fraternally
Last edited by wsherif1; 29th Jul 2002 at 20:05.
Union Goon
Join Date: Feb 2000
Location: New Jersey, USA
Posts: 1,097
Likes: 0
Received 0 Likes
on
0 Posts
So bill, if the Aircraft dutch rolled you don't think that would be because the TAIL WAS MISSING!
Come on bill, you don't fly the aircraft, you have been out of it for a while, and the greater increase in INS for flight instruments rather than the old DGs and stuff change their ability to be spoofed...
The first input in the DFDR by Sten was a coordinated input (rudder and aileron went the same way) Later events were different.
Your reliance on witness reports is really funny. I choose to use the one that reported the explosion, and the other 1 that reported a missle.
We have been doing those departures out of Kennedy for years bill. Every damn day. They weren't any closer than 100s of other wake encounters. The seperation wasn't especially tight. And like the 727/737 encounter that lead to PITT the only thing that the wake did was start the event. It didn't tear the tail off. You are the only person talking about 200 kts wind blasts shearing off the tail. The NTSB is not, the APA is not, the FAA is not, how is it that you, not a party at all to the investigation come up with this brilliant insight?
ANd the captain didn't shut down the engines of 990 himself to try and save the aircraft. While that would reduce thrust in the 707 days and not change controllability much because of the cable backups. It would be SUICIDE in a 767, Which incidentally is exactly what 990 was (murder suicide to more precise because of all the people he took with him)....
Come on bill, you don't fly the aircraft, you have been out of it for a while, and the greater increase in INS for flight instruments rather than the old DGs and stuff change their ability to be spoofed...
The first input in the DFDR by Sten was a coordinated input (rudder and aileron went the same way) Later events were different.
Your reliance on witness reports is really funny. I choose to use the one that reported the explosion, and the other 1 that reported a missle.
We have been doing those departures out of Kennedy for years bill. Every damn day. They weren't any closer than 100s of other wake encounters. The seperation wasn't especially tight. And like the 727/737 encounter that lead to PITT the only thing that the wake did was start the event. It didn't tear the tail off. You are the only person talking about 200 kts wind blasts shearing off the tail. The NTSB is not, the APA is not, the FAA is not, how is it that you, not a party at all to the investigation come up with this brilliant insight?
ANd the captain didn't shut down the engines of 990 himself to try and save the aircraft. While that would reduce thrust in the 707 days and not change controllability much because of the cable backups. It would be SUICIDE in a 767, Which incidentally is exactly what 990 was (murder suicide to more precise because of all the people he took with him)....
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders
If the tail was missing there could not be a Dutch roll!
It is true that I do not fly the particular aircraft but you still push and pull the same way!
I have survived a B707 pitchup, a 12,500 free fall, a severe aircraft wake turbulence encounter 45 miles behind another B707,(in smooth air) Dr. AA Wray of NASA affirms that in smooth air conditions aircraft wake turbulence can persist for extended periods of time.
Yes there have been many improvements in flight instrument technology but they still rely on the basic pitot-tube static port sensors. Wind shear forces across their openings produce low pressures. See Boeing Publication, "AERO 08" for info. on the possibility of erroneous flight instrument indications. See the TV coverage of the COPA B737 accident over Tucuti, Panama. When they ran the FDR readout through the computer the Boeing engineers declared that the radical maneuvers were impossible for the aircraft to perform!
NASA states that the rotating vortices forces in aircraft wake turbulence can be as high as 300'/sec. When this force strikes the total surface of the vertical stabilizer and the rudder, first on one side and and then immediately on the opposite side, the possibility exists that the bending forces may have exceeded the ultimate load factor of the vertical stabilizer and the rudder. Which obviously it did!
I never said the EgyptAir 990 Captain shut down the engines himself. You obviously have not seen the FDR readout of the 990 accident. The NTSB reported the elevators were split and intimated that the crew were fighting for control of the aircraft. This is absolutely incorrect! The FDR shows that both elevator control inputs were exactly the same until the aircraft reaches .99 Mach! At this time the flight controls are subject to buffeting and the aircraft is now beyond recovery from the dive attitude!
The NTSB also claims that there were no flight anomalies prior to the Co-pilot's first exclamation of a prayer. Again the NTSB is evidently unable to read the FDR. On the FDR readout there is an abrupt right bank input and the Co-pilot says, "control it"! Seconds later the first prayer is voiced!
The NTSB completely ignores the, "Egypt Air 990 Track Plots" which indicates the number of aircraft on crossing flight paths at similiar times.
The NTSB ignores the 'thumps' of the turbulence and the clicks of the stabilizer trim wheels, in the cockpit, as they react to the wind shear of the turbulence!
The Co-pilot of EgyptAir 990 did not commit a deliberate suicide, as Jim Hall claims, but he did commit an INADVERTANT suicide in reaction to turbulence induced aircraft attitude transitions and erroneous flight instrument indications! Excerpt from an NTSB letter dated January 21, 1998. "Pilot reaction to turbulence, MOSTLY INADVERTANT, does cause more problems than the jolt of turbulence itself"!
To indicate further the incompetence of the NTSB, I refer you to the United 826 accident (one fatality, five broken necks and seven broken backs, besides other serious passenger injuries, from supposedly, clear air turbulence.) The NTSB claimed that the aircraft had encountered a force of negative 0.8 G and the passengers had been subjected to a force approaching Zero G. When I received a copy of the FDR, from the NTSB, in response to a letter I had forwarded regarding this accident, it was obvious that the actual reading was 1.8 negative G! How would it be possible to inflict a fatality and the other serious injuries at a force approaching Zero G!
When I asked a senior NTSB investigator , at a hearing, how they had arrived at their reading of 0.8 negative G? He replied , "You start from zero and count down to the maximum point and that is the G reading! When did we start flying around at Zero G!!!
At a later time there was an article in the AW&ST about a French aircraft turbulence encounter. They had a copy of the FDR readout included in the article and believe it or not they were also measuring the G force from the zero G line!
I could remark on other gross errors the NTSB has made in other investigations but will save them for another time. Don't take the theories of the NTSB too seriously. That is the problem with the technology challenged media, they echo whatever the NTSB spouts!
Happy flying
It is true that I do not fly the particular aircraft but you still push and pull the same way!
I have survived a B707 pitchup, a 12,500 free fall, a severe aircraft wake turbulence encounter 45 miles behind another B707,(in smooth air) Dr. AA Wray of NASA affirms that in smooth air conditions aircraft wake turbulence can persist for extended periods of time.
Yes there have been many improvements in flight instrument technology but they still rely on the basic pitot-tube static port sensors. Wind shear forces across their openings produce low pressures. See Boeing Publication, "AERO 08" for info. on the possibility of erroneous flight instrument indications. See the TV coverage of the COPA B737 accident over Tucuti, Panama. When they ran the FDR readout through the computer the Boeing engineers declared that the radical maneuvers were impossible for the aircraft to perform!
NASA states that the rotating vortices forces in aircraft wake turbulence can be as high as 300'/sec. When this force strikes the total surface of the vertical stabilizer and the rudder, first on one side and and then immediately on the opposite side, the possibility exists that the bending forces may have exceeded the ultimate load factor of the vertical stabilizer and the rudder. Which obviously it did!
I never said the EgyptAir 990 Captain shut down the engines himself. You obviously have not seen the FDR readout of the 990 accident. The NTSB reported the elevators were split and intimated that the crew were fighting for control of the aircraft. This is absolutely incorrect! The FDR shows that both elevator control inputs were exactly the same until the aircraft reaches .99 Mach! At this time the flight controls are subject to buffeting and the aircraft is now beyond recovery from the dive attitude!
The NTSB also claims that there were no flight anomalies prior to the Co-pilot's first exclamation of a prayer. Again the NTSB is evidently unable to read the FDR. On the FDR readout there is an abrupt right bank input and the Co-pilot says, "control it"! Seconds later the first prayer is voiced!
The NTSB completely ignores the, "Egypt Air 990 Track Plots" which indicates the number of aircraft on crossing flight paths at similiar times.
The NTSB ignores the 'thumps' of the turbulence and the clicks of the stabilizer trim wheels, in the cockpit, as they react to the wind shear of the turbulence!
The Co-pilot of EgyptAir 990 did not commit a deliberate suicide, as Jim Hall claims, but he did commit an INADVERTANT suicide in reaction to turbulence induced aircraft attitude transitions and erroneous flight instrument indications! Excerpt from an NTSB letter dated January 21, 1998. "Pilot reaction to turbulence, MOSTLY INADVERTANT, does cause more problems than the jolt of turbulence itself"!
To indicate further the incompetence of the NTSB, I refer you to the United 826 accident (one fatality, five broken necks and seven broken backs, besides other serious passenger injuries, from supposedly, clear air turbulence.) The NTSB claimed that the aircraft had encountered a force of negative 0.8 G and the passengers had been subjected to a force approaching Zero G. When I received a copy of the FDR, from the NTSB, in response to a letter I had forwarded regarding this accident, it was obvious that the actual reading was 1.8 negative G! How would it be possible to inflict a fatality and the other serious injuries at a force approaching Zero G!
When I asked a senior NTSB investigator , at a hearing, how they had arrived at their reading of 0.8 negative G? He replied , "You start from zero and count down to the maximum point and that is the G reading! When did we start flying around at Zero G!!!
At a later time there was an article in the AW&ST about a French aircraft turbulence encounter. They had a copy of the FDR readout included in the article and believe it or not they were also measuring the G force from the zero G line!
I could remark on other gross errors the NTSB has made in other investigations but will save them for another time. Don't take the theories of the NTSB too seriously. That is the problem with the technology challenged media, they echo whatever the NTSB spouts!
Happy flying
Last edited by wsherif1; 30th Jul 2002 at 01:59.
Join Date: Mar 2000
Location: Obvious
Age: 78
Posts: 301
Likes: 0
Received 0 Likes
on
0 Posts
An Expanded Theory
Below (the preamble) I've attempted to point out the significance of the A300 FDR's limitation (of only being connected downstream of where FC system data was being "filtered").
The following extract's from the 12 Apr 02 7th NTSB Public Release at:
http://www.ntsb.gov/Pressrel/2002/020412b.htm
My theory (on Pprune) about the probable CADC involvement pre-dated this by some months.
1. "Other Airbus Event
The Safety Board is interested in another upset event last year involving an Airbus aircraft. On November 25, 2001, a Singapore Airlines A340-300 departed Singapore for a scheduled flight to Dhaka, with 96 persons aboard. Shortly after takeoff, the pilots noticed a problem with airspeed indicators. Among other things, there were overspeed warnings and large rudder movements without pilot input. The aircraft returned to Singapore and made a safe landing; there were no injuries.
Inspection subsequently found problems with the pitot and static connections to the air data computers, which may have been introduced during recent maintenance. The Civil Aviation Authority of Singapore is investigating the incident. Due to computed loads that might have been experienced by the vertical stabilizer, it and the attached rudder were removed from the aircraft shortly after the incident and were recently examined in Germany.
Although no damage was found in either the stabilizer or the rudder, the Board is interested in the rudder system’s role in this event."
I consider this prior event to be very significant - and indicative of a design glitch within the A300's FCS. In fact...even Blind Freddy could see that.
2. from http://www.ntsb.gov/Pressrel/2002/020115.htm
Flight Data Recorder
The flight data recorder continues to be analyzed. That process is taking a little longer in this case because signals for some parameters on this aircraft are "filtered" before they reach the flight recorder. The filtering operation is used to smooth data that drive cockpit displays so that the needle (or other indicator) does not jump around. This filtering is accomplished by averaging the data over time. When large, rapid movements are made, this averaging will distort the recorded data; rapid, extreme control movements are clipped off. As a result, the readings on the recorder show what the gauges were telling the pilots, not necessarily what was actually occurring on a real-time basis to the aircraft. This will require some aircraft testing and then further computations by Board staff to get the true readings on some parameters of interest like rudder, elevator, and aileron movement. Although this has added to the workload of investigators, it is not expected to affect the quality or the timing of the Board's final product.
In 1994, the Safety Board recommended to the FAA that such filtering systems be removed from information sent to flight data recorders. The FAA told the NTSB that its 1997 final rule amending FDR requirements "precludes the use of a filter and specifies the seconds-per-sampling interval for all parameters." Based on that information, the Safety Board closed its recommendation as "Acceptable Action" on August 9, 2000. The Safety Board has alerted Airbus and the FAA of the problem noted on the recorder recovered from American Airlines flight 587.
Reference Loral F-800 DFDR (and its unsatisfactory performance in prior accident investigations)
Page 88 of 353 at http://www.caa.co.uk/docs/33/CAP455.pdf - previously declared defective and obsolescent by the UK CAA
wsherif1 said:
"Wind shear, via turbulence induced in the Pitot-Static System, can cause fluctuating pressures which can induce erroneous flight instrument readings. Turbulence can also induce aircraft attitude transitions. ... These triggers can induce instinctive pilot flight control inputs that may result in aircraft upset accidents"
Developing that a little:
If in fact the CADC's response to instantaneous pressure changes are so rapid that the pressure fluxes inside a wake vortex double-whammy can generate instantaneously inappropriate FCS responses and wholly out-of-whack rudder limiter constraint settings and yaw-damper interventions, then that would go a long way towards explaining AA587.
In other words, during a wake encounter the airplane's wild gyrations are continually challenging the FCS to correct - but because of the pressure spikes being input into the CADC and the dynamism being fed to the rate gyros, any satisfactory "derived" outcome becomes unlikely. Why is that? One answer might be "inappropriately interacting FCS algorithms". Consider here the 25 Nov 01 Singaporean A340 that had wild airspeed fluctuations and overspeed warnings plus uncommanded rudder deflections - all (allegedly) because of some CADC maintenance glitch in its pitot-statics. Consider also that the reason why the Loral FDR's record is "filtered" was because the data pickoff is downstream of the point where the FC system itself was being filtered. Now why would you do that to an FCS? (heavily filter its I/O)- unless the input data-rate of some circuits were too high and causing undesirable FCS system reflex confusion or incomplete/over-reaction? I'd suggest that Airbus isn't telling the whole truth about some of the design compromises that were made (forced) once they got into the original experimental test-flying. Maybe the signal filtration (damping) was required to quieten down some control surface/sub-system inter-actions (rudder limiter/ PCU / yaw damper) - that might have been producing undesirable results (the hydraulic chatter or system-induced oscillations that I introduced originally)..
To get one's mind around this, and why the airplane sometimes responds normally (and sometimes doesn't), think of it in these terms. The original A300 FCC design probably accommodated trending rate data rather than raw processed flight control surface positions and airplane axis displacements. In other words, if a developing yaw-rate was detected (e.g. heading beginning to change nose-left at a certain rate) the FCS would instantly outguess it by feeding in a minor countering rudder displacement - and restore stability even before any significant yaw had actually happened. The basis for the sensing of such a finely tuned rate-sensitive system would be highly tied and integrated rate sensors (i.e. gyros), control surface position transducers and CADC I/O data (based upon digital integration of raw pitot-static info).... all designed quite early on in the digital age.
In any steady-state near-equilibrant scenario such a system is going to give a very comfortable ride. However if the rate sensing and pressure sensing was subjected to significantly divergent data flux (as in the sizeable rapid pressure reversals and momentary aircraft attitude changes within wake turbulence), the inbuilt lag in the physical FCS (hyd valves, actuators and motors, inclusive of stab and trim) would subside into systemic chaos and the ultimate nightmare of slipping into an out-of-phase response condition.
It's partly a function of the rate of integration of analogue data and partly due to the physical limitations of mechanical interfaces, but even inertia gets to play an increasing role as the flux becomes stronger and the displacements greater. Rudder limiters and yaw dampers would be responding inappropriately (to the point of amplifying rather than damping) and yes, even the pilots could be sucked into trying to resolve any resulting excursions or oscillations by tramping the rudder pedals - and themselves become out-of-phase and part of the complex problem of systemic aperiodicity.
So I remain convinced that an external initiating event (the wake encounter) was necessary to set this "bridge too far" process in train. The gross pressure fluctuations and ever-changing attitude within a strong wake was enough to get the A300 FCS into its high-gear resolution mode - but (contrarily) its built-in ability to rapidly detect and respond to instantaneous trends was then enough to drive the rudder responses into an out-of-phase frenzy. In consequence, at exactly the wrong moment, (and at the wrong angle [in the wrong attitude and flight-path]) the a/c hit the second wake and the fin's port-side attachment failed laterally in overload shear, the fin rocking a few times but then rotating laterally around the three stbd lugs until it tore away.
So perhaps with AA587's rapid breakup we've now seen the very first system-induced oscillation (SIO). Or perhaps that should read SRC (System Reflex Confusion). Underbuild (or underspec?) of the composite fin I see as only contributory - although of course without that factor it may have been just a wake turbulence incident (non-reportable unless someone was injured).
But the FDR's plumbing and deficiencies can perhaps be seen as a clue as to why the A300 FCS was so heavily filtered - and poses questions about why that might have been necessary - and just when might it have been introduced into the design (in consequence of ...?). My guess would be sometime well after that first prototype flew...... and for good reason. It would have been a software implementation I guess. I'd be surprised if "aperiodicity" doesn't make it into the final report. It's a word that belongs with the study of vortex behaviour - but in an entirely different sense than it probably applied to AA587's sudden flight control system's conundrum.
The following extract's from the 12 Apr 02 7th NTSB Public Release at:
http://www.ntsb.gov/Pressrel/2002/020412b.htm
My theory (on Pprune) about the probable CADC involvement pre-dated this by some months.
1. "Other Airbus Event
The Safety Board is interested in another upset event last year involving an Airbus aircraft. On November 25, 2001, a Singapore Airlines A340-300 departed Singapore for a scheduled flight to Dhaka, with 96 persons aboard. Shortly after takeoff, the pilots noticed a problem with airspeed indicators. Among other things, there were overspeed warnings and large rudder movements without pilot input. The aircraft returned to Singapore and made a safe landing; there were no injuries.
Inspection subsequently found problems with the pitot and static connections to the air data computers, which may have been introduced during recent maintenance. The Civil Aviation Authority of Singapore is investigating the incident. Due to computed loads that might have been experienced by the vertical stabilizer, it and the attached rudder were removed from the aircraft shortly after the incident and were recently examined in Germany.
Although no damage was found in either the stabilizer or the rudder, the Board is interested in the rudder system’s role in this event."
I consider this prior event to be very significant - and indicative of a design glitch within the A300's FCS. In fact...even Blind Freddy could see that.
2. from http://www.ntsb.gov/Pressrel/2002/020115.htm
Flight Data Recorder
The flight data recorder continues to be analyzed. That process is taking a little longer in this case because signals for some parameters on this aircraft are "filtered" before they reach the flight recorder. The filtering operation is used to smooth data that drive cockpit displays so that the needle (or other indicator) does not jump around. This filtering is accomplished by averaging the data over time. When large, rapid movements are made, this averaging will distort the recorded data; rapid, extreme control movements are clipped off. As a result, the readings on the recorder show what the gauges were telling the pilots, not necessarily what was actually occurring on a real-time basis to the aircraft. This will require some aircraft testing and then further computations by Board staff to get the true readings on some parameters of interest like rudder, elevator, and aileron movement. Although this has added to the workload of investigators, it is not expected to affect the quality or the timing of the Board's final product.
In 1994, the Safety Board recommended to the FAA that such filtering systems be removed from information sent to flight data recorders. The FAA told the NTSB that its 1997 final rule amending FDR requirements "precludes the use of a filter and specifies the seconds-per-sampling interval for all parameters." Based on that information, the Safety Board closed its recommendation as "Acceptable Action" on August 9, 2000. The Safety Board has alerted Airbus and the FAA of the problem noted on the recorder recovered from American Airlines flight 587.
Reference Loral F-800 DFDR (and its unsatisfactory performance in prior accident investigations)
Page 88 of 353 at http://www.caa.co.uk/docs/33/CAP455.pdf - previously declared defective and obsolescent by the UK CAA
wsherif1 said:
"Wind shear, via turbulence induced in the Pitot-Static System, can cause fluctuating pressures which can induce erroneous flight instrument readings. Turbulence can also induce aircraft attitude transitions. ... These triggers can induce instinctive pilot flight control inputs that may result in aircraft upset accidents"
Developing that a little:
If in fact the CADC's response to instantaneous pressure changes are so rapid that the pressure fluxes inside a wake vortex double-whammy can generate instantaneously inappropriate FCS responses and wholly out-of-whack rudder limiter constraint settings and yaw-damper interventions, then that would go a long way towards explaining AA587.
In other words, during a wake encounter the airplane's wild gyrations are continually challenging the FCS to correct - but because of the pressure spikes being input into the CADC and the dynamism being fed to the rate gyros, any satisfactory "derived" outcome becomes unlikely. Why is that? One answer might be "inappropriately interacting FCS algorithms". Consider here the 25 Nov 01 Singaporean A340 that had wild airspeed fluctuations and overspeed warnings plus uncommanded rudder deflections - all (allegedly) because of some CADC maintenance glitch in its pitot-statics. Consider also that the reason why the Loral FDR's record is "filtered" was because the data pickoff is downstream of the point where the FC system itself was being filtered. Now why would you do that to an FCS? (heavily filter its I/O)- unless the input data-rate of some circuits were too high and causing undesirable FCS system reflex confusion or incomplete/over-reaction? I'd suggest that Airbus isn't telling the whole truth about some of the design compromises that were made (forced) once they got into the original experimental test-flying. Maybe the signal filtration (damping) was required to quieten down some control surface/sub-system inter-actions (rudder limiter/ PCU / yaw damper) - that might have been producing undesirable results (the hydraulic chatter or system-induced oscillations that I introduced originally)..
To get one's mind around this, and why the airplane sometimes responds normally (and sometimes doesn't), think of it in these terms. The original A300 FCC design probably accommodated trending rate data rather than raw processed flight control surface positions and airplane axis displacements. In other words, if a developing yaw-rate was detected (e.g. heading beginning to change nose-left at a certain rate) the FCS would instantly outguess it by feeding in a minor countering rudder displacement - and restore stability even before any significant yaw had actually happened. The basis for the sensing of such a finely tuned rate-sensitive system would be highly tied and integrated rate sensors (i.e. gyros), control surface position transducers and CADC I/O data (based upon digital integration of raw pitot-static info).... all designed quite early on in the digital age.
In any steady-state near-equilibrant scenario such a system is going to give a very comfortable ride. However if the rate sensing and pressure sensing was subjected to significantly divergent data flux (as in the sizeable rapid pressure reversals and momentary aircraft attitude changes within wake turbulence), the inbuilt lag in the physical FCS (hyd valves, actuators and motors, inclusive of stab and trim) would subside into systemic chaos and the ultimate nightmare of slipping into an out-of-phase response condition.
It's partly a function of the rate of integration of analogue data and partly due to the physical limitations of mechanical interfaces, but even inertia gets to play an increasing role as the flux becomes stronger and the displacements greater. Rudder limiters and yaw dampers would be responding inappropriately (to the point of amplifying rather than damping) and yes, even the pilots could be sucked into trying to resolve any resulting excursions or oscillations by tramping the rudder pedals - and themselves become out-of-phase and part of the complex problem of systemic aperiodicity.
So I remain convinced that an external initiating event (the wake encounter) was necessary to set this "bridge too far" process in train. The gross pressure fluctuations and ever-changing attitude within a strong wake was enough to get the A300 FCS into its high-gear resolution mode - but (contrarily) its built-in ability to rapidly detect and respond to instantaneous trends was then enough to drive the rudder responses into an out-of-phase frenzy. In consequence, at exactly the wrong moment, (and at the wrong angle [in the wrong attitude and flight-path]) the a/c hit the second wake and the fin's port-side attachment failed laterally in overload shear, the fin rocking a few times but then rotating laterally around the three stbd lugs until it tore away.
So perhaps with AA587's rapid breakup we've now seen the very first system-induced oscillation (SIO). Or perhaps that should read SRC (System Reflex Confusion). Underbuild (or underspec?) of the composite fin I see as only contributory - although of course without that factor it may have been just a wake turbulence incident (non-reportable unless someone was injured).
But the FDR's plumbing and deficiencies can perhaps be seen as a clue as to why the A300 FCS was so heavily filtered - and poses questions about why that might have been necessary - and just when might it have been introduced into the design (in consequence of ...?). My guess would be sometime well after that first prototype flew...... and for good reason. It would have been a software implementation I guess. I'd be surprised if "aperiodicity" doesn't make it into the final report. It's a word that belongs with the study of vortex behaviour - but in an entirely different sense than it probably applied to AA587's sudden flight control system's conundrum.
Join Date: Sep 2001
Location: 38N
Posts: 356
Likes: 0
Received 0 Likes
on
0 Posts
Belgique - You're hitting close to the mark. I have reached essentially the same view (also aka Systemsguy) as the facts (and gaps) have emerged. It now seems plausible that the failure could have resulted - in part - from System-Induced rudder Oscillations originating in an adversely resonant combination of sensor sampling rates, sample-errors and averaging effects -- with those made possible by design gaps in the conception and testing of the rudder control SYSTEM for a full range of boundary cases.
The uncomfortable aspect of this idea is that it implies an inherent weakness of design characteristics in the system which could be triggered again in another situation under similar or quite different circumstances.
One point on which I differ slightly is that I do not think (after rather many hours driving experimental control systems around in various situations, including aircraft) that signal filtering and pre-processing is inherently a bad thing - so long as one does not destroy too much useful information in the process. Out-of-sync timing of control responses - or some processes using filtered data and some using unfiltered - can get you resonating faster than mere hamfisted filtering.
At a philosophical level, the current cohort of civil FBW and non-FBW transport aircraft designs may be seen as straddling the line between all-direct-coupled (mechanical:analog) and all-robotic (electrical/optical:digital) sensing and control systems. Prior generations were mostly mechanical, and the successor ones will be mostly robotic. We are just at the cusp. The problem accompanying this is that the two philosophies do not always mesh well at either technical or human (design and support) levels, so such hybrid systems can have unique failure modes which simply do not apply in either form of the 'pure' implementation.
And it seems really very unfortunate that the inflexible, mysterious, and not-overly-strong tail design was added to this broth.
Whatever the official conclusions, some timely re-engineering seems prudent and likely.
The uncomfortable aspect of this idea is that it implies an inherent weakness of design characteristics in the system which could be triggered again in another situation under similar or quite different circumstances.
One point on which I differ slightly is that I do not think (after rather many hours driving experimental control systems around in various situations, including aircraft) that signal filtering and pre-processing is inherently a bad thing - so long as one does not destroy too much useful information in the process. Out-of-sync timing of control responses - or some processes using filtered data and some using unfiltered - can get you resonating faster than mere hamfisted filtering.
At a philosophical level, the current cohort of civil FBW and non-FBW transport aircraft designs may be seen as straddling the line between all-direct-coupled (mechanical:analog) and all-robotic (electrical/optical:digital) sensing and control systems. Prior generations were mostly mechanical, and the successor ones will be mostly robotic. We are just at the cusp. The problem accompanying this is that the two philosophies do not always mesh well at either technical or human (design and support) levels, so such hybrid systems can have unique failure modes which simply do not apply in either form of the 'pure' implementation.
And it seems really very unfortunate that the inflexible, mysterious, and not-overly-strong tail design was added to this broth.
Whatever the official conclusions, some timely re-engineering seems prudent and likely.
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
Re: An Expanded Theory
Belgique,
Your reference to my comments on wind shear affecting the pitot-static system causing erroneous flight instrument indications, while valid in 'upset' accidents are not applicable in the AA 587 accident.
The strength of the clockwise rotating vortices striking the left side of the fin, BROADSIDE, initiated such an instantaneous left yaw motion, and resultant Dutch roll, that the flight instrument readings were of no significance.
Ths instantaneous left yaw then presented the right side of the fin to the slipstream and the same vortices forces on the right side of the tail surfaces. This immediate reversal of the bending forces, exceeding the ultimate load point, sheared off the fin just above the attaching lug connections.
The tremendous forces involved in this radical, instantaneous maneuver were beyond any possible pilot induced flight control, (rudder), input to initiate or recover from. The forces striking the combined surface area of the large vertical stabilizer, (two engine aircraft design), and the rudder, together, was the initiating source of this accident.
Eye witness statement, "The right wing was perpendicular to the ground"!
Any time two engines are sheared off the structure there will be fire, smoke, and explosive noises!
Best regards
Your reference to my comments on wind shear affecting the pitot-static system causing erroneous flight instrument indications, while valid in 'upset' accidents are not applicable in the AA 587 accident.
The strength of the clockwise rotating vortices striking the left side of the fin, BROADSIDE, initiated such an instantaneous left yaw motion, and resultant Dutch roll, that the flight instrument readings were of no significance.
Ths instantaneous left yaw then presented the right side of the fin to the slipstream and the same vortices forces on the right side of the tail surfaces. This immediate reversal of the bending forces, exceeding the ultimate load point, sheared off the fin just above the attaching lug connections.
The tremendous forces involved in this radical, instantaneous maneuver were beyond any possible pilot induced flight control, (rudder), input to initiate or recover from. The forces striking the combined surface area of the large vertical stabilizer, (two engine aircraft design), and the rudder, together, was the initiating source of this accident.
Eye witness statement, "The right wing was perpendicular to the ground"!
Any time two engines are sheared off the structure there will be fire, smoke, and explosive noises!
Best regards
Last edited by wsherif1; 30th Jul 2002 at 23:41.
Union Goon
Join Date: Feb 2000
Location: New Jersey, USA
Posts: 1,097
Likes: 0
Received 0 Likes
on
0 Posts
Bill Go buy a balsa wood glider, take the tail off of it and I will show you an airplane with the wing vertical to the ground.
587 cut across the radius of the 747s turn it wasn't following it strait so it wasn't a 90 degree hit.
When the tail came off the aircraft became onstable in Yaw and went through the air sideways decelerating at .8 g...
I know you old guys are set in your ways but please....
Wino
587 cut across the radius of the 747s turn it wasn't following it strait so it wasn't a 90 degree hit.
When the tail came off the aircraft became onstable in Yaw and went through the air sideways decelerating at .8 g...
I know you old guys are set in your ways but please....
Wino
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders
Wino,
Obviously in your relatively limited experience you have never been in a strong yaw maneuver!
They did not have a yaw damper in the early days of the 707 operation!
Never shove the nose down in a 'pitchup'!
Obviously in your relatively limited experience you have never been in a strong yaw maneuver!
They did not have a yaw damper in the early days of the 707 operation!
Never shove the nose down in a 'pitchup'!
Last edited by wsherif1; 1st Aug 2002 at 00:10.
Join Date: Mar 2001
Location: us
Posts: 694
Likes: 0
Received 0 Likes
on
0 Posts
wsherif1, you repeatedly assert that a witness saw AA587 with the right wing perpindicular to the ground. The NTSB has logged 349 witness accounts, and has summarized these as follows:
"The Witness Group has received 349 accounts from eyewitnesses, either through direct interviews or through written statements. An initial summary of those statements follows:
· 52% specifically reported seeing a fire while the plane was in the air, with the fuselage being the most often cited location (22%). Other areas cited as a fire location were the left engine, the right engine or an unspecified engine, and the left wing, the right wing or an unspecified wing.
· 8% specifically reported seeing an explosion.
· 20% specifically reported seeing no fire at all.
· 22% reported observing smoke; 20% reported no smoke.
· 18% reported observing the airplane in a right turn; another 18% reported observing the airplane in a left turn.
· 13% observed the airplane "wobbling," dipping" or in "side to side" motion.
· 74% observed the airplane descend.
· 57% reported seeing "something" separate from the airplane; 13% reported observing the right wing, left wing or an undefined wing separate; 9% specifically reported observing no parts separate."
It would seem from the great variance in these accounts that one could find support for an assertion that the right wing was perpindicular, the left wing was perpindicular, or the plane was in a horizontally level descent.
I also don't think you advance your argument by insisting that SilkAir and EgyptAir 990 were caused by wake turbulence. Surely you don't believe that wake turbulence induced a sequential disconnection of SilkAir's FDR and CVR while the plane was in cruise. EgyptAir 990 crashed at about 1:50AM EST, a time of light North Atlantic traffic in that sector, as the ATC transcript indicates. Looking at the FDR tabular data sets, it would seem that the EgyptAir flight anomaly you are referring to is a very brief -0.53 roll several seconds before the co-pilot is believed to say 'control it'. Yet this same degree of roll also briefly occurred at 01:43:28 EST, without comment or concern. (The captain leaves closing the cockpit door at 01:48:22; 01:48:24 roll of -0.53; 01:48:27 roll of -0.35; 01:48:30 'control it'; 01:48:30, roll of -0.18; 01:48:40, the first of the "I rely on God" statements by Bahouty; 01:48:40, roll of 0.00. The AoA, pitch, and roll values do become anomalous startring at 01:49:40; at 01:50:04, pitch of -22.50, roll of -10.72; the captain re-enters the cockpit at 01:50:07, asking "what's happening? what's happening?"
"The Witness Group has received 349 accounts from eyewitnesses, either through direct interviews or through written statements. An initial summary of those statements follows:
· 52% specifically reported seeing a fire while the plane was in the air, with the fuselage being the most often cited location (22%). Other areas cited as a fire location were the left engine, the right engine or an unspecified engine, and the left wing, the right wing or an unspecified wing.
· 8% specifically reported seeing an explosion.
· 20% specifically reported seeing no fire at all.
· 22% reported observing smoke; 20% reported no smoke.
· 18% reported observing the airplane in a right turn; another 18% reported observing the airplane in a left turn.
· 13% observed the airplane "wobbling," dipping" or in "side to side" motion.
· 74% observed the airplane descend.
· 57% reported seeing "something" separate from the airplane; 13% reported observing the right wing, left wing or an undefined wing separate; 9% specifically reported observing no parts separate."
It would seem from the great variance in these accounts that one could find support for an assertion that the right wing was perpindicular, the left wing was perpindicular, or the plane was in a horizontally level descent.
I also don't think you advance your argument by insisting that SilkAir and EgyptAir 990 were caused by wake turbulence. Surely you don't believe that wake turbulence induced a sequential disconnection of SilkAir's FDR and CVR while the plane was in cruise. EgyptAir 990 crashed at about 1:50AM EST, a time of light North Atlantic traffic in that sector, as the ATC transcript indicates. Looking at the FDR tabular data sets, it would seem that the EgyptAir flight anomaly you are referring to is a very brief -0.53 roll several seconds before the co-pilot is believed to say 'control it'. Yet this same degree of roll also briefly occurred at 01:43:28 EST, without comment or concern. (The captain leaves closing the cockpit door at 01:48:22; 01:48:24 roll of -0.53; 01:48:27 roll of -0.35; 01:48:30 'control it'; 01:48:30, roll of -0.18; 01:48:40, the first of the "I rely on God" statements by Bahouty; 01:48:40, roll of 0.00. The AoA, pitch, and roll values do become anomalous startring at 01:49:40; at 01:50:04, pitch of -22.50, roll of -10.72; the captain re-enters the cockpit at 01:50:07, asking "what's happening? what's happening?"
Join Date: Jul 2002
Location: Sweden
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
My experience as a pilot is very limited (Gliders). I have been working with software development and testing since the 60's. I am on the PPRuNe out of interest and to learn.
Reading the input from Belgique and arcniz gives me a nasty feeling of recognition.
There is no such thing as a complex software system without bugs in it. Combine this with filtering of the input, maybe errors in the input due to failures in the sensors and you may end up with a very strange response from the system.
From my experience. If I had to choose between two boxes doing the same thing:
1 A proven mechanical device
2 The latest computer controlled gadget in the market
and it was vital to me that the thing performed as advertised I would choose number 1.
Reading the input from Belgique and arcniz gives me a nasty feeling of recognition.
There is no such thing as a complex software system without bugs in it. Combine this with filtering of the input, maybe errors in the input due to failures in the sensors and you may end up with a very strange response from the system.
From my experience. If I had to choose between two boxes doing the same thing:
1 A proven mechanical device
2 The latest computer controlled gadget in the market
and it was vital to me that the thing performed as advertised I would choose number 1.
Join Date: Jul 2002
Location: 40N, 80W
Posts: 233
Likes: 0
Received 0 Likes
on
0 Posts
Re: NTSB and Rudders
The F-meter
It seems to me that w.r.t. tail fins coming off a/c, and what is too much (or too little) rudder input in various circumstances, that there is an existing potentially useful technology which is not getting any attention.
Many aircraft have G-meters. As you know, these are based on strain gauges which measure forces on things. An electrical resistance element gets stretched and the resistance goes up. Very simple and cheap.
You fly a plane with a G-meter so that the needle does not go into the red. Doesn’t matter whether you are heading vertically down at speed, you do whatever you have to do to the controls to keep the needle out of the red (particularly at speed).
The tail-fin problem seems to me to have some similarities. You use a G-meter to keep the wings from coming off. We need an F-meter to keep the fin from coming off.
Fins come off (I am assuming) because the stresses and strains are more than the fin can stand. As has been pointed out, this might arise from wake vortex action without any pilot input. So put a strain gauge on the fin and a display in the cockpit. No debate now as to what is too much pilot rudder input or too little, just keep the needle out of the red. In a pronounced yaw the pilot rudder input may have to be to keep the rudder inline with the airflow and hence will seem to the pilot to be in a direction to INCREASE the yaw. However, if you don’t the needle may go into the red.
Of course, in practice it won’t be quite as simple as I am making out. For instance:
(a) where do you put the strain gauge(s)? You may have to use a number of gauges at a number of points, each output scaled to the max. permitted strain at that point, and feed the largest value to the cockpit display.
(b) can you retrofit gauges? Gauges are usually just glued to a surfaces, so this may not be a great problem. Maintenance may be a problem for gauges exposed to the weather and the fingers of the curious. But at least some could be applied to or near the internal protected fin-attachment lugs, and within the fin.
The greatest potential advantage seems to me to be that in normal flying pilots will get a feel of how stresses on the fin are related to rudder inputs and turbulence in various phases of flight (regardless of how yaw-dampers and computers may be modifying your control inputs).
You would get a direct reading of what matters, as with a G-meter.
What do YOU think?
It seems to me that w.r.t. tail fins coming off a/c, and what is too much (or too little) rudder input in various circumstances, that there is an existing potentially useful technology which is not getting any attention.
Many aircraft have G-meters. As you know, these are based on strain gauges which measure forces on things. An electrical resistance element gets stretched and the resistance goes up. Very simple and cheap.
You fly a plane with a G-meter so that the needle does not go into the red. Doesn’t matter whether you are heading vertically down at speed, you do whatever you have to do to the controls to keep the needle out of the red (particularly at speed).
The tail-fin problem seems to me to have some similarities. You use a G-meter to keep the wings from coming off. We need an F-meter to keep the fin from coming off.
Fins come off (I am assuming) because the stresses and strains are more than the fin can stand. As has been pointed out, this might arise from wake vortex action without any pilot input. So put a strain gauge on the fin and a display in the cockpit. No debate now as to what is too much pilot rudder input or too little, just keep the needle out of the red. In a pronounced yaw the pilot rudder input may have to be to keep the rudder inline with the airflow and hence will seem to the pilot to be in a direction to INCREASE the yaw. However, if you don’t the needle may go into the red.
Of course, in practice it won’t be quite as simple as I am making out. For instance:
(a) where do you put the strain gauge(s)? You may have to use a number of gauges at a number of points, each output scaled to the max. permitted strain at that point, and feed the largest value to the cockpit display.
(b) can you retrofit gauges? Gauges are usually just glued to a surfaces, so this may not be a great problem. Maintenance may be a problem for gauges exposed to the weather and the fingers of the curious. But at least some could be applied to or near the internal protected fin-attachment lugs, and within the fin.
The greatest potential advantage seems to me to be that in normal flying pilots will get a feel of how stresses on the fin are related to rudder inputs and turbulence in various phases of flight (regardless of how yaw-dampers and computers may be modifying your control inputs).
You would get a direct reading of what matters, as with a G-meter.
What do YOU think?
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders: The F Meter
Having a G meter reading available in the cockpit would be of considerable value to the pilot, however in the case of the AA587 accident it would have been of little use.
When the vertical stabilizer and the rudder were struck broadside by the forces of the 747's clockwise rotating vortices the resulting instantaneous yaw maneuver was initiated before the pilot had a chance to react to what would have been erroneous flight instrument indications anyway. The pilots were just along for the ride!
When the vertical stabilizer and the rudder were struck broadside by the forces of the 747's clockwise rotating vortices the resulting instantaneous yaw maneuver was initiated before the pilot had a chance to react to what would have been erroneous flight instrument indications anyway. The pilots were just along for the ride!
Union Goon
Join Date: Feb 2000
Location: New Jersey, USA
Posts: 1,097
Likes: 0
Received 0 Likes
on
0 Posts
I love a guy who goes into the investigation with the whole thing solved ahead of schedule.
As to limited myexperience...
10 years of airline line flying 3 years as a FCF (funtional test flight) pilot. engine out ferry, new aircraft receipt and delivery, post maint test flying. I have moved aircraft in and out of the desert (that usually involves lots of interesting things not being installed on the aircraft). So don't assume that I don't know about yaw and manuevering. I have personally stalled 42 B727 aircraft. Full stalls as required by the RAM 738k boeing's post D check flight test checklist.
I have done PLENTY of flying without yaw dampers bill. I have also had a 727 depart at 18k and recovered at 6 after 3 inverted turns when the bullnose on a kruger was misrigged (that's the whole point of the test flights) and the aircraft departed 4 knots before predicted shaker, as the right engine surged from the disrupted airflow just as the wing broke down...
So Bill, we are in an area where I probably have more experience that you as you only flew the line. You should know who you are talking down to.
I say again. There was nothing Unique about 587's departure. Plenty of other aircraft have gotten much closer and more perfectly aligned with the wakes of 747s and they still have their tail.
What that person demonstrated to you in the sim was a crock. Its like what Airbus did in the sim with me when I went to Miami Airbus factory school to get my A320 rating. They have what they call the "dollar ride" to get you used to the sidestick controller on your first day. after you fly around for a little they tell you to close the close the throttles and peg the stick in the back right corner of its movement. That gives you a 2.5 G 66 degree climbing spiral as you bleed speed off Alpha Floor kicks in and the engines go to full power that the sim goes up at 10k per minute. Now that is really cool, but ask yourself if ANY airbus product can sustain a 10k per min climb wing level. Of course the answer is no, so there is no way that adding 2.5 G loading on the aircraft is gonna improve climb performance so its just a game they put in the sim to make you go Gee whiz what a cool plane. Doesn't mean its real.
Samething goes for your sim experience where that instructor crashed you... There was a bug in the program and the sim guy exploited it.
Cheers
Wino
As to limited myexperience...
10 years of airline line flying 3 years as a FCF (funtional test flight) pilot. engine out ferry, new aircraft receipt and delivery, post maint test flying. I have moved aircraft in and out of the desert (that usually involves lots of interesting things not being installed on the aircraft). So don't assume that I don't know about yaw and manuevering. I have personally stalled 42 B727 aircraft. Full stalls as required by the RAM 738k boeing's post D check flight test checklist.
I have done PLENTY of flying without yaw dampers bill. I have also had a 727 depart at 18k and recovered at 6 after 3 inverted turns when the bullnose on a kruger was misrigged (that's the whole point of the test flights) and the aircraft departed 4 knots before predicted shaker, as the right engine surged from the disrupted airflow just as the wing broke down...
So Bill, we are in an area where I probably have more experience that you as you only flew the line. You should know who you are talking down to.
I say again. There was nothing Unique about 587's departure. Plenty of other aircraft have gotten much closer and more perfectly aligned with the wakes of 747s and they still have their tail.
What that person demonstrated to you in the sim was a crock. Its like what Airbus did in the sim with me when I went to Miami Airbus factory school to get my A320 rating. They have what they call the "dollar ride" to get you used to the sidestick controller on your first day. after you fly around for a little they tell you to close the close the throttles and peg the stick in the back right corner of its movement. That gives you a 2.5 G 66 degree climbing spiral as you bleed speed off Alpha Floor kicks in and the engines go to full power that the sim goes up at 10k per minute. Now that is really cool, but ask yourself if ANY airbus product can sustain a 10k per min climb wing level. Of course the answer is no, so there is no way that adding 2.5 G loading on the aircraft is gonna improve climb performance so its just a game they put in the sim to make you go Gee whiz what a cool plane. Doesn't mean its real.
Samething goes for your sim experience where that instructor crashed you... There was a bug in the program and the sim guy exploited it.
Cheers
Wino
Join Date: Jan 2002
Location: San Diego, CA
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
NTSB and Rudders
Please cancel all references to experience levels!
I still see all the evidence pointing to a radical yaw induced Dutch roll from strong aircraft wake vortices striking the fin and rudder broadside.
I guess we will have to wait till NASA comes out with their wake analysis to get a true picture.
Fraternally
I still see all the evidence pointing to a radical yaw induced Dutch roll from strong aircraft wake vortices striking the fin and rudder broadside.
I guess we will have to wait till NASA comes out with their wake analysis to get a true picture.
Fraternally