United Flight 93, What actually happened ? [somewhat edited by JT]
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by el !
J_T,
unfortunately in the 9/11 tragedy the aviation technical side is quite small compared to all the rest.
Discussing UA93 here, at the end of the day, we are left debating if it is true that debris fell off the plane before final impact, and if that is true, why it fell and why this is not in the offical report.
Obviously no aviation expert can help in these questions so either we have a totally open, 360º discussion, or the thread is closed because is deadended.
unfortunately in the 9/11 tragedy the aviation technical side is quite small compared to all the rest.
Discussing UA93 here, at the end of the day, we are left debating if it is true that debris fell off the plane before final impact, and if that is true, why it fell and why this is not in the offical report.
Obviously no aviation expert can help in these questions so either we have a totally open, 360º discussion, or the thread is closed because is deadended.
No one has to read this thread if he is not interested!
I belive most readers want to know the truth!
Join Date: Aug 2006
Location: Summer
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
Eh, no supermannn, is not like you say.
UA93 will not teach us nothing in aviation safety nor security, because technically there is nothing to learn from a crash caused by a terrorist fighting heroic attempts to retake control.
People have been very patient with you and gave you many answers. At some point like a miracle the FDR popped up and it is saying that the plane was shaken a lot but crashed in one piece where it was later found.
Now you either:
a) tell us that you believe the FDR, so the only thing left is that you take a trip to Somerset County, collect witnesses reports, with video and all the stuff, then make a big website about the mistery debris.
b) tell us you don't believe the FDR and become Chief Conspirationist with all the consequences.
You've been talking on thin air long enough. Now to the meat, please.
UA93 will not teach us nothing in aviation safety nor security, because technically there is nothing to learn from a crash caused by a terrorist fighting heroic attempts to retake control.
People have been very patient with you and gave you many answers. At some point like a miracle the FDR popped up and it is saying that the plane was shaken a lot but crashed in one piece where it was later found.
Now you either:
a) tell us that you believe the FDR, so the only thing left is that you take a trip to Somerset County, collect witnesses reports, with video and all the stuff, then make a big website about the mistery debris.
b) tell us you don't believe the FDR and become Chief Conspirationist with all the consequences.
You've been talking on thin air long enough. Now to the meat, please.
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Longitudinal, vertical, lateral are three airplane cordinates, i.e. fixed on long axis of the plane, vertical to the long axis and the one spans over the wings, is this correct?
Simplistic forces:
engine thrust, air drag are two longitudinal forces (do not cause vertical acceleration)
air lift, and gravity are two vertical to the ground forces (projected to the vertical axis of the plane, cause vertical acceleration).
The only way to cause the plane's vertical acceleration (without outside forces) is the air lift vs. gravity projected to the plane's vertical axis, depends on the pitch angle. Am I right here? (airlift-g)*cos (pitch angle) = vertical acceleration (is this correct?)
Let's look at the first vertical acceleration peak again, Mad scientist, the vertical acceleration jumped to 3.7 g, the longitudinal acceleration jumped at the same time, to 0.6 g. The air lift is caused by the speed of the airplane and aerodynamics, right? LOOK VERY CAREFULLY on the pitch angle, it didn't change until the vertical acceleration droped. The pitch angle leading edge is very sharp, even with 1" sampling time, it is a jump after the vertical acceleration droped. The vertical acceleration is the projection of gravity+airlift on the plane's vertical axis (is this correct?).
If you look at the take off, see the vertical acceleration, and comparing with the "vibration" before the first peak, I believe the "vibrations" were caused by the wild manuvor by the terrorists. But air lift suddenly caused the plane's vertical acceleration to 3.7 g, it is hard to believe, especially the pitch angle changed afterward, not before.
Look at the longitudinal acceleration before 9:58, it started to increase from close to zero up to about 0.15 g for 2 minutes, pitch angle slowly increased at the same time from close to 0 to about 4 degrees (also change up and down), vertical acceleration was vibrating violently (maybe a roaler coaster ride here? Seems like it was trying to run away from something, or simply trying to threw away passengers?). Then the peak, both vertical and longitudinal at the same time, it is hard to read the lateral at this peak point. pitch angle droped a little before it jumped to 20 degrees. In terms of seconds (considering the sampling rate).
Does everyone agree that this is simply a wild manuvor?
Simplistic forces:
engine thrust, air drag are two longitudinal forces (do not cause vertical acceleration)
air lift, and gravity are two vertical to the ground forces (projected to the vertical axis of the plane, cause vertical acceleration).
The only way to cause the plane's vertical acceleration (without outside forces) is the air lift vs. gravity projected to the plane's vertical axis, depends on the pitch angle. Am I right here? (airlift-g)*cos (pitch angle) = vertical acceleration (is this correct?)
Let's look at the first vertical acceleration peak again, Mad scientist, the vertical acceleration jumped to 3.7 g, the longitudinal acceleration jumped at the same time, to 0.6 g. The air lift is caused by the speed of the airplane and aerodynamics, right? LOOK VERY CAREFULLY on the pitch angle, it didn't change until the vertical acceleration droped. The pitch angle leading edge is very sharp, even with 1" sampling time, it is a jump after the vertical acceleration droped. The vertical acceleration is the projection of gravity+airlift on the plane's vertical axis (is this correct?).
If you look at the take off, see the vertical acceleration, and comparing with the "vibration" before the first peak, I believe the "vibrations" were caused by the wild manuvor by the terrorists. But air lift suddenly caused the plane's vertical acceleration to 3.7 g, it is hard to believe, especially the pitch angle changed afterward, not before.
Look at the longitudinal acceleration before 9:58, it started to increase from close to zero up to about 0.15 g for 2 minutes, pitch angle slowly increased at the same time from close to 0 to about 4 degrees (also change up and down), vertical acceleration was vibrating violently (maybe a roaler coaster ride here? Seems like it was trying to run away from something, or simply trying to threw away passengers?). Then the peak, both vertical and longitudinal at the same time, it is hard to read the lateral at this peak point. pitch angle droped a little before it jumped to 20 degrees. In terms of seconds (considering the sampling rate).
Does everyone agree that this is simply a wild manuvor?
Join Date: Aug 2006
Location: New York
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SUPERMNNN
I will post some reference later.
"Fleegle, marina owner Jim Brant and two of Brant’s employees were among the dozens who witnessed the crash from Indian Lake. Fleegle had just returned to the marina to get fuel for a boat that had run out of gas when Carol Delasko called him into the drydock barn to watch news of the World Trade Center attack.
“All of a sudden the lights flickered and we joked that maybe they were coming for us. Then we heard engines screaming close overhead. The building shook. We ran out, heard the explosion and saw a fireball mushroom,” said Fleegle, pointing to a clearing on a ridge at the far end of the lake.
Delasko, who ran outside moments later, said she thought someone had blown up a boat on the lake. “It just looked like confetti raining down all over the air above the lake,” she said.
Fleegle, Brant and a fellow marina worker, Tom Spinelli, jumped in a truck and rushed to the crash site.
In the woods, they saw only a crater and tiny pieces of debris.
Fleegle said he climbed on the roof of an abandoned cabin and tossed down a burning seat cushion that had landed there.
By Wednesday morning, crash debris began washing ashore at the marina. Fleegle said there was something that looked like a rib bone amid pieces of seats, small chunks of melted plastic and checks. He said FBI agents who spent the afternoon patrolling the lake in rented boats eventually carted away a large garbage bag full of debris."
http://www.pittsburghlive.com/x/pitt...b/s_12967.html
"The village of New Baltimore is a dozen or more miles by automobile but eight as the wind blows, which it was doing a year ago. Melanie Hankinson was at the church next to her home, transfixed before a television that showed the World Trade Center ablaze, when the man who sprays her lawn stopped by to tell her he was finding odd things in the weeds.
"He said there was a loud bang and smoke and then these papers started blowing through your yard," she said. "I said, 'Oh.' Then I went back to the TV." Then the parish priest, the Rev. Allen Zeth, told her an airplane had crashed in Shanksville.
For the next few hours, Hankinson gathered charred pages of in-flight magazines, papers from a pilot's manual -- she remembers a map showing the Guadalajara, Mexico, airport -- and copies of stock portfolio monthly earnings reports.
"And there was some black webbing -- a lot of people found that," she said. The webbing, flexible where it hadn't burned, crisp where it had, was from insulation lining the belly of the jetliner."
http://www.post-gazette.com/columnis...oddy0911p5.asp
"Meanwhile, investigators also are combing a second crime scene in nearby Indian Lake, where residents reported hearing the doomed jetliner flying over at a low altitude before "falling apart on their homes."
"People were calling in and reporting pieces of plane falling," a state trooper said.
Jim Stop reported he had seen the hijacked Boeing 757 fly over him as he was fishing. He said he could see parts falling from the plane.
As yet, there have been no official reports of any human remains recovered from the lake area. "
http://www.pittsburghlive.com/x/pitt...b/s_47536.html
"Residents and workers at businesses outside Shanksville, Somerset County, reported discovering clothing, books, papers and what appeared to be human remains. Some residents said they collected bags-full of items to be turned over to investigators. Others reported what appeared to be crash debris floating in Indian Lake, nearly six miles from the immediate crash scene."
http://www.post-gazette.com/headline...somersetp3.asp
BUT ACCORDING TO XPMORTEN'S DATA, THE PLANE SHOULE BE IN A GOOD SHAPE BEFORE CRASHING.
"Fleegle, marina owner Jim Brant and two of Brant’s employees were among the dozens who witnessed the crash from Indian Lake. Fleegle had just returned to the marina to get fuel for a boat that had run out of gas when Carol Delasko called him into the drydock barn to watch news of the World Trade Center attack.
“All of a sudden the lights flickered and we joked that maybe they were coming for us. Then we heard engines screaming close overhead. The building shook. We ran out, heard the explosion and saw a fireball mushroom,” said Fleegle, pointing to a clearing on a ridge at the far end of the lake.
Delasko, who ran outside moments later, said she thought someone had blown up a boat on the lake. “It just looked like confetti raining down all over the air above the lake,” she said.
Fleegle, Brant and a fellow marina worker, Tom Spinelli, jumped in a truck and rushed to the crash site.
In the woods, they saw only a crater and tiny pieces of debris.
Fleegle said he climbed on the roof of an abandoned cabin and tossed down a burning seat cushion that had landed there.
By Wednesday morning, crash debris began washing ashore at the marina. Fleegle said there was something that looked like a rib bone amid pieces of seats, small chunks of melted plastic and checks. He said FBI agents who spent the afternoon patrolling the lake in rented boats eventually carted away a large garbage bag full of debris."
http://www.pittsburghlive.com/x/pitt...b/s_12967.html
"The village of New Baltimore is a dozen or more miles by automobile but eight as the wind blows, which it was doing a year ago. Melanie Hankinson was at the church next to her home, transfixed before a television that showed the World Trade Center ablaze, when the man who sprays her lawn stopped by to tell her he was finding odd things in the weeds.
"He said there was a loud bang and smoke and then these papers started blowing through your yard," she said. "I said, 'Oh.' Then I went back to the TV." Then the parish priest, the Rev. Allen Zeth, told her an airplane had crashed in Shanksville.
For the next few hours, Hankinson gathered charred pages of in-flight magazines, papers from a pilot's manual -- she remembers a map showing the Guadalajara, Mexico, airport -- and copies of stock portfolio monthly earnings reports.
"And there was some black webbing -- a lot of people found that," she said. The webbing, flexible where it hadn't burned, crisp where it had, was from insulation lining the belly of the jetliner."
http://www.post-gazette.com/columnis...oddy0911p5.asp
"Meanwhile, investigators also are combing a second crime scene in nearby Indian Lake, where residents reported hearing the doomed jetliner flying over at a low altitude before "falling apart on their homes."
"People were calling in and reporting pieces of plane falling," a state trooper said.
Jim Stop reported he had seen the hijacked Boeing 757 fly over him as he was fishing. He said he could see parts falling from the plane.
As yet, there have been no official reports of any human remains recovered from the lake area. "
http://www.pittsburghlive.com/x/pitt...b/s_47536.html
"Residents and workers at businesses outside Shanksville, Somerset County, reported discovering clothing, books, papers and what appeared to be human remains. Some residents said they collected bags-full of items to be turned over to investigators. Others reported what appeared to be crash debris floating in Indian Lake, nearly six miles from the immediate crash scene."
http://www.post-gazette.com/headline...somersetp3.asp
BUT ACCORDING TO XPMORTEN'S DATA, THE PLANE SHOULE BE IN A GOOD SHAPE BEFORE CRASHING.
edit: Note that in the highlighted passage about parts falling from the plane, it seems he's saying he saw parts falling from the plane as it flew over, but I've read most of the witness accounts, and I've found the reporting of them to be temporally vague. Like others witnesses, he may have been describing debris from the plume after the crash. Or he may have imagined he saw things fall from the plane.
Last edited by MarkRoberts; 16th Aug 2006 at 01:29.
Join Date: Aug 2006
Location: New York
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SUPERMNNN
Does everyone agree that this is simply a wild manuvor?
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SUPERMNNN
Longitudinal, vertical, lateral are three airplane cordinates, i.e. fixed on long axis of the plane, vertical to the long axis and the one spans over the wings, is this correct?
Simplistic forces:
engine thrust, air drag are two longitudinal forces (do not cause vertical acceleration)
air lift, and gravity are two vertical to the ground forces (projected to the vertical axis of the plane, cause vertical acceleration).
The only way to cause the plane's vertical acceleration (without outside forces) is the air lift vs. gravity projected to the plane's vertical axis, depends on the pitch angle. Am I right here? (airlift-g)*cos (pitch angle) = vertical acceleration (is this correct?)
Simplistic forces:
engine thrust, air drag are two longitudinal forces (do not cause vertical acceleration)
air lift, and gravity are two vertical to the ground forces (projected to the vertical axis of the plane, cause vertical acceleration).
The only way to cause the plane's vertical acceleration (without outside forces) is the air lift vs. gravity projected to the plane's vertical axis, depends on the pitch angle. Am I right here? (airlift-g)*cos (pitch angle) = vertical acceleration (is this correct?)
You're not that far off, but there are some subtleties that can really throw you off, especially in extreme manoeuvres. Specifically:
Yes, you have the three axes identified correctly; for these discussions it doesn't matter which way the lateral axis is oriented. In flight dynamics positive vertical is down, but as long as we don't get into specific equations that wont matter either.
Again, yes, simplistically those are the forces. But strictly the way you've described it IS a simplification. The actual forces in longitudinal axis system (fore-aft/up-down/pitching angle) are:
- Gravity : acts down in the EARTH reference.
- Thrust : made of two components:
Gross thrust acts along the engine thrust line (straight out the back of the nozzle) usually closely aligned to (but not identical to) the aircraft longitudinal axis
Intake or "ram" drag : drag due to the air slowing down to enter the engine - acts "backwards" along the aircraft flightpath vector
Note that these two forces need not be parallel - for simplicity we sometimes assume they are, and speak of "net thrust" - gross thrust minus ram drag - but again at extreme attitudes this approximation becomes less valid - Aerodynamic Lift ; acts normal to the flightpath vector
- Aerodynamic drag : acts along the flightpath vector
Note that, strictly, NONE of these forces act in the aircraft reference system, which is where the accelerations are measured. Therefore to correlate the accels with the forces requires knowing the angles which enable the translations. The most import of these are pitch attitude, which defines the relationship between the aircraft and EARTH, and angle of attack - "alpha" - which defines the relationship between the flightpath vector and the aircraft
Which means that the vertical acceleration at any point contains:
- the gravity component in the plane vertical axis - gcos(pitch)
- the lift component in the plane vertical axis - LIFTcos(alpha)
- the drag component in the plane vertical axis - -1*DRAGsin(alpha)
- any engine ram drag (same resolution as the DRAG)
- engine gross thrust (depends on engine thrustline)
Now, if you assume an aircraft in nice straight level flight, alpha=pitch and everything simplifies a bit. But, this isn't stable flight by any means. To really look at the coherence between the accels and flightpaths would need a 6dof sim tool AND access to the real data. We have neither.
So, we can use "EJ" but it's already another source of error.
Let's look at the first vertical acceleration peak again, Mad scientist, the vertical acceleration jumped to 3.7 g, the longitudinal acceleration jumped at the same time, to 0.6 g. The air lift is caused by the speed of the airplane and aerodynamics, right? LOOK VERY CAREFULLY on the pitch angle, it didn't change until the vertical acceleration droped. The pitch angle leading edge is very sharp, even with 1" sampling time, it is a jump after the vertical acceleration droped. The vertical acceleration is the projection of gravity+airlift on the plane's vertical axis (is this correct?).
Its not just a question of low sample rates, but of asynchronous sampling. Because of data rate issues to the FDR, data is sampled continuously across all the parameters, which means that related parameters are sampled out-of-synch.
With a 64 word/sec FDR, I wouldn't be surprised if pitch were in, say, the first and 33rd words (2Hz), AoA in perhaps the 17th (pilot side) and 49th (copilot), normal accel in the 8th, 16th, etc (8Hz) and so on. So in a case like that, if a manoeuvre starts just after the 1st word you'd have 4 nz raedings before the next pitch reading - so ON THE DATA nz would "lead" pitch, and also alpha. BUT NOT IN REALITY.
You're going to get sick of hearing me say this, but reading FDR data is as much an art as a science; you need to know all the tricks of the trade to really read it properly, and we're stuck with a single plot at poor scales.
Does everyone agree that this is simply a wild manuvor?
But my professional opinion, as someone who has spent most of his working life looking at flight data of various kinds, including FDR data, is that the traces presented in the FDR report are consistent with the 'official' version of events i.e. they show a plane being violently manoeuvred in the final couple of minutes of flight, and do not show evidence of an inflight breakup or of an attempt to recover the aircraft by a non-suicidal 'hero passenger'.
@el ! - I agree there's nothing remarkable on the FDR; but I'd rather try to explain why that is so, than just make a declaration ex cathedra.
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
Somewhat off the topic, but this might help illustrate why you can't use an FDR to deduce intentions and can get led astray easily.
Postulate:
We have FDR data for an airliner, which crashed killing all aboard, with the usual eyewitness reports of fireballs and diving into the ground.
On inspection the FDR data shows the aircraft in straight level flight at a decent speed, say 250kts. Then, in the space of one second, all the following are evident on the data:
Aircraft parts are found in a fairly spread debris field, indicating in-flight breakup.
OK, what happened? I can give you half a dozen scenarios which ALL could fit that data. Some are sinister, some not.
The point Im trying to make is that the FDR data can (usually, but not always) say *WHAT* happened - if it recorded it. It can almost *NEVER* say *WHY*.
Postulate:
We have FDR data for an airliner, which crashed killing all aboard, with the usual eyewitness reports of fireballs and diving into the ground.
On inspection the FDR data shows the aircraft in straight level flight at a decent speed, say 250kts. Then, in the space of one second, all the following are evident on the data:
- master caution sounds (confirmed on CVR)
- aircraft rolls violently to right, 60+ deg bank
- aircraft increases AoA rapidly, 'g' increases
- sudden change of heading
followed in the next second by - further increase in 'g' and bank
- pilot voice saying "what the ****"
- CVR captures break-up noises
- FDR data becomes invalid
Aircraft parts are found in a fairly spread debris field, indicating in-flight breakup.
OK, what happened? I can give you half a dozen scenarios which ALL could fit that data. Some are sinister, some not.
- Aircraft hit by missile which pilot tried to avoid at last minute (lets assume he's ex-military,as many are)
- Aircraft had to swerve violently to miss unidentified stealthy aircraft (or UFO) and suffered structural breakup
- aircraft suffered flight control malfunction (mechanical or FBW software)
- Aircraft was manoeuvring to avoid mid-air collision with non-conspiracy theory aircraft
- Pilot suicide (always a popular theory since its impossible to disprove)
- Practicing a manoeuvre to avoid mid-air collision (unlikely with pax, maybe not if a ferry flight)
- Other miscellaneous illegal barnstorming by flight crew
The point Im trying to make is that the FDR data can (usually, but not always) say *WHAT* happened - if it recorded it. It can almost *NEVER* say *WHY*.
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MarkRoberts
Right. The only materials found far from the sight were small enough to be windborne, NOT "flight manuals" and "magazines." The only anomalous report is from one man who thought he saw debris falling from the plane. I am not aware of similar reports from the many other eyewitnesses.
edit: Note that in the highlighted passage about parts falling from the plane, it seems he's saying he saw parts falling from the plane as it flew over, but I've read most of the witness accounts, and I've found the reporting of them to be temporally vague. Like others witnesses, he may have been describing debris from the plume after the crash. Or he may have imagined he saw things fall from the plane.
edit: Note that in the highlighted passage about parts falling from the plane, it seems he's saying he saw parts falling from the plane as it flew over, but I've read most of the witness accounts, and I've found the reporting of them to be temporally vague. Like others witnesses, he may have been describing debris from the plume after the crash. Or he may have imagined he saw things fall from the plane.
Webbing pieces: several reports mentioned them. They came down right after the crash. They were isolatedly spread in New Baltimore. (no reports showed that they were found in Indian Lake). If wind blow those pieces there, it couldn't concentrate in an isolated area. We would see trails from the crash site to New Baltimore (a slice of pizza shaped debris field).
For canceled checks, there were reports said that they were found from both locations.
Signature debris in Indian Lake were seat cushions which were not found in New Baltimore.
Yes all eyewitness reports were not organized, not very accurate. But many cross-references confirmed the debris I used for analysis.
But accurate or not, it is much harder to cook eyewitnesses than data, we'd better show respect for them.
Last edited by SUPERMNNN; 16th Aug 2006 at 08:45.
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Very clear explainations, thanks Mad. I should find some books from the library. "To busy" is a lame excuse, but a true reality.
1. "In flight dynamics positive vertical is down..." is this mean that the "up" direction of vertical accelleration (on the FDR plot) is actually down (pointing to the earth)? But from the plot, the plane flied at 1 g all the way after takeoff, which means that the vertical acceleration on the plot is the combined "lift" of all the vertical components. (not "lift accel"-g).
2. Which of the following (or combined) forces could possible generate 3 to 4 g, considering the low sample rate, let's say in 5 seconds?
the gravity component in the plane vertical axis - gcos(pitch)
the lift component in the plane vertical axis - LIFTcos(alpha)
the drag component in the plane vertical axis - -1*DRAGsin(alpha)
any engine ram drag (same resolution as the DRAG)
engine gross thrust (depends on engine thrustline)
Besides gravity, all the air components (lift and drag) are gentle forces, which means that they grow slowly and reduce slowly.
Only hard core force I can see is the engine gross thrust (when it is out of line from the longitudinal direction?).
For a BOEING 757, engine force (MAX THRUST): 193.5 KN (EACH?), take off weight: 1156.80kg. So the max thrust acceleration is 3.4 g. How can it be projected to the vertical direction to more than 1 g?
1. "In flight dynamics positive vertical is down..." is this mean that the "up" direction of vertical accelleration (on the FDR plot) is actually down (pointing to the earth)? But from the plot, the plane flied at 1 g all the way after takeoff, which means that the vertical acceleration on the plot is the combined "lift" of all the vertical components. (not "lift accel"-g).
2. Which of the following (or combined) forces could possible generate 3 to 4 g, considering the low sample rate, let's say in 5 seconds?
the gravity component in the plane vertical axis - gcos(pitch)
the lift component in the plane vertical axis - LIFTcos(alpha)
the drag component in the plane vertical axis - -1*DRAGsin(alpha)
any engine ram drag (same resolution as the DRAG)
engine gross thrust (depends on engine thrustline)
Besides gravity, all the air components (lift and drag) are gentle forces, which means that they grow slowly and reduce slowly.
Only hard core force I can see is the engine gross thrust (when it is out of line from the longitudinal direction?).
For a BOEING 757, engine force (MAX THRUST): 193.5 KN (EACH?), take off weight: 1156.80kg. So the max thrust acceleration is 3.4 g. How can it be projected to the vertical direction to more than 1 g?
Last edited by SUPERMNNN; 16th Aug 2006 at 08:51.
Join Date: Aug 2006
Location: Somerset, UK
Age: 75
Posts: 82
Likes: 0
Received 0 Likes
on
0 Posts
Besides gravity, all the air components (lift and drag) are gentle forces, which means that they grow slow and reduce slow
Join Date: Aug 2006
Location: New York
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SUPERMNNN
When I sort through those reports, I tried to located some "signature" debris:
Webbing pieces: several reports mentioned them. They came down right after the crash.
Webbing pieces: several reports mentioned them. They came down right after the crash.
They are isolatedly spread in New Baltimore. (no reports showed that they were found in Indian Lake).
If wind blow those pieces there, it couldn't concentrate in an isolated area. We would see trails from the crash site to New Baltimore.
signature debris in Indian Lake were seat cushions which were not found in New Baltimore.
Yes all eyewitness reports were not organized, not very accurate. But many cross references confirmed the debris I used for analysis.
But accurate or not, it is much harder to cook eyewitnesses than data, we'd better show respect to them.
But accurate or not, it is much harder to cook eyewitnesses than data, we'd better show respect to them.
Bottom line: the only debris found far from the crash site was light enough to be carried by the wind, and is consistent with the wind direction. Debris was not found along the plane's flight path.
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by XPMorten
3.5 g's has been pulled in 757's before.
An incident at ENGM an Icelandair 757 pulled 3.59 g's positive.
the report;
http://www.sht.no/items/427/144/2216...TF_FIO_eng.pdf
(Paragraph 1.1.14.5)
M
An incident at ENGM an Icelandair 757 pulled 3.59 g's positive.
the report;
http://www.sht.no/items/427/144/2216...TF_FIO_eng.pdf
(Paragraph 1.1.14.5)
M
It read "load" of +3.5 g, I assume it is the load to the engine? Sorry, again, I am not in the field and too lazy to go to library, could you explain this to me?
Join Date: Aug 2006
Location: Somerset, UK
Age: 75
Posts: 82
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SUPERMNNN
M, is this the vertical acceleration?
It read "load" of +3.5 g, I assume it is the load to the engine? Sorry, again, I am not in the field and too lazy to go to library, could you explain this to me?
It read "load" of +3.5 g, I assume it is the load to the engine? Sorry, again, I am not in the field and too lazy to go to library, could you explain this to me?
Join Date: Aug 2006
Location: Summer
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
M (F) S,
I had already noticed not only the competence but the completeness and detail of your answers in this forum.
You made no exception in this case of evident fixation, yet I feel that only a moderator's hand can stop further idle questioning. So far that hand got busy only to remove my commend that Mr. S. doesn't have anything to say and is only willing to socialize. Thing that is not an insult nor a false stament. But such is life on pprune.
I usually look with simpathy to anything that challenges authority, but it must come with intelligence, and that does not appear to be case.
I had already noticed not only the competence but the completeness and detail of your answers in this forum.
You made no exception in this case of evident fixation, yet I feel that only a moderator's hand can stop further idle questioning. So far that hand got busy only to remove my commend that Mr. S. doesn't have anything to say and is only willing to socialize. Thing that is not an insult nor a false stament. But such is life on pprune.
I usually look with simpathy to anything that challenges authority, but it must come with intelligence, and that does not appear to be case.
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Choxolate
Go to the library - I think it is a little insulting to expect others to do your work for you. This subject is obviously of great importance to you as you will not let it rest so how about doing your own leg work.
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MarkRoberts
Bottom line: the only debris found far from the crash site was light enough to be carried by the wind, and is consistent with the wind direction. Debris was not found along the plane's flight path.
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by SUPERMNNN
1. "In flight dynamics positive vertical is down..." is this mean that the "up" direction of vertical accelleration (on the FDR plot) is actually down (pointing to the earth)? But from the plot, the plane flied at 1 g all the way after takeoff, which means that the vertical acceleration on the plot is the combined "lift" of all the vertical components. (not "lift accel"-g).
2. Which of the following (or combined) forces could possible generate 3 to 4 g, considering the low sample rate, let's say in 5 seconds?
the gravity component in the plane vertical axis - gcos(pitch)
the lift component in the plane vertical axis - LIFTcos(alpha)
the drag component in the plane vertical axis - -1*DRAGsin(alpha)
any engine ram drag (same resolution as the DRAG)
engine gross thrust (depends on engine thrustline)
the gravity component in the plane vertical axis - gcos(pitch)
the lift component in the plane vertical axis - LIFTcos(alpha)
the drag component in the plane vertical axis - -1*DRAGsin(alpha)
any engine ram drag (same resolution as the DRAG)
engine gross thrust (depends on engine thrustline)
Besides gravity, all the air components (lift and drag) are gentle forces, which means that they grow slowly and reduce slowly.
Only hard core force I can see is the engine gross thrust (when it is out of line from the longitudinal direction?).
Only hard core force I can see is the engine gross thrust (when it is out of line from the longitudinal direction?).
An engine can take seconds to change thrust (there's one certification regulation that specifies that the "thrust after 8 seconds" is used to calculate go-around performance) - engine forces generally are at least an order of magnitude slower than aerodynamic forces
For a BOEING 757, engine force (MAX THRUST): 193.5 KN (EACH?), take off weight: 1156.80kg. So the max thrust acceleration is 3.4 g. How can it be projected to the vertical direction to more than 1 g?
Thread Starter
Join Date: Aug 2006
Location: usa
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Ok, the load factor is vertical acceleration. When you dive then pull up, at the bottom of the curve, high vertical acceleration can occur. Rollercoaster ride will have high positive and negative g at the top and bottom of the curve.
For a dive, don't the pitch angle turn negative, then pull up to positive, on the bottom, there would be a high vertical g. There are three small peaks and valleys on altitude plot. With speed, pitch angle, altitude change, is the g can be calculated to verify that it is indeed the rough handling caused the vertical g?
Actually we missed a force, centrifugal force can also give you a high vertical g.
For a dive, don't the pitch angle turn negative, then pull up to positive, on the bottom, there would be a high vertical g. There are three small peaks and valleys on altitude plot. With speed, pitch angle, altitude change, is the g can be calculated to verify that it is indeed the rough handling caused the vertical g?
Actually we missed a force, centrifugal force can also give you a high vertical g.
Last edited by SUPERMNNN; 16th Aug 2006 at 12:19.
Join Date: Aug 2005
Location: Estonia
Posts: 834
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Mad (Flt) Scientist
No, as stated, aerodynamic forces can change VERY fast - as fast as the airflow can change, which is limited only by the speed of sound in a fluid dynamics sense. if you take the typical wing chord as, say, 30ft, and the aircraft speed at 300knots, you'll see that the wing is encountering a completely new "patch of air" every 0.06 seconds (~150m/s speed, 10m length) which means that the order of magnitude time for significant changes in aerodynamic forces is also less than one tenth of a second.
Originally Posted by Mad (Flt) Scientist
Please ignore the engines; they are NOT anything to do with the peaks and troughs in vertical accel for this incident. it's changes in angle of attack, causing changes in lift, and there's nothing unusual required to explain it.
Turning a 50 m long plane by 30 degrees of pitch axis takes some time...