EasyJet 737 incident debunks Pilot for 9/11 truth V-G diagram video

MikeC

Closed Account
Where did I claim I have "no precedent"?
About 4 or 5 posts ago - have you forgotten already??

Are you denying that you wrote:

You are correct. There is no precedent, because all precedent in fact contradicts what we have been told about 9/11.

I have stated I do have precedent which contradicts the events of 9/11.... and I provided a source.

Make up your mind.

]
It is, at best, stupid hyperbole....
Content from External Source
Well, that isn't very polite.. .is it?

Seems fine to me...and also accurate.

I notice that you are avoiding the actual issue - saying that there was NO evidence when there is evidence, saying there was NO wind tunnel testing when there was wind tunnel testing.

Care to address those at all?
 

SpaceCowboy

Rob Balsamo of P4T
Banned
Mike,

Let me see if I can make this more clear.... (i caught your reply on the way out...)...

There is no precedent which can compare to an aircraft flying at Va+220, Vmo+150, Vd+90, pulling G's, rolling on G's (which significantly lower structural G limitations) to compare and validate the maneuvers performed on 9/11. This is why weedwhacker said there is no precedent to compare to 9/11, and I agreed with him.

However....

The precedent we do have, conflicts with the events reported on 9/11.



Get it yet?

Don't bother to reply here as I am done posting here since my posts just get deleted.

Email us or join the P4T forum. I am also willing to debate you (or anyone else here) on air in front of a much larger audience if you would like to work out the details of a mutual agreed upon venue and moderator.

Up to you...
 

WeedWhacker

Senior Member
Could you go into more detail?

China Air 006 and TWA 841, for instance. The loss of control was pilot induced. Exacerbated by different circumstances. China Air crew were focused on an engine failure, allowed their airspeed to decay and didn't notice (due to the autopilot being in control) until the A/P reached its limit of control authority and disconnected. The asymmetrical thrust caused the yaw and roll and subsequent out-of-control dive. The "structural failure" did not result in a total failure of the airframe -- it landed safely, and was later repaired and returned to service.

TWA 841, although the crew denied it, consensus is (it gets technically complicated) but, let's say they were doing something not approved nor conventional. The loss of control involved another "high-dive" and speeds approaching Mach 1, and as with the China Air flight, excessive G-loads. Yet, even though some structural failure (the leading edge flaps...but THAT was the reason in the first place!) and the landing gear being extended at well above the maximum speed (gear door damage, not really structural...and IIRC the main gear struts were actually bent aftwards a bit), it landed safely, and was repaired and returned to service.

Merely two examples from the P4T "VG-Diagram" representation that are included on the graph in a disingenuous manner. Their inclusion is misleading and inflammatory.

I have more, but will shorten the post here. Point is just those two Boeing airplanes FAR exceeded any predictable flight-test and design tolerances, yet were robust enough to survive, and even fly again.
 

jaydeehess

Senior Member.
Alas, the crux of the matter for a layperson.
"Pilots for 911 Truth" claims that any aircraft that exceeds VD​ will begin to suffer flutter and structural damage and could not possibly remain in flight.
Others cite instances in which aircraft were definitely outside the limits of design and yet either suffered no damage, or some damage but were repaired and returned to service after, of course, landing safely.

While the PfT contentions would on the face of it seem likely to a lay person, the very existance of other aircraft doing this and surviving should compell one to understand that structural damage and loss of control is not a given as an aircraft goes outside of design limits.
 

jaydeehess

Senior Member.
"Airplane speed limits are typically determined by something known as flutter. Flutter is the violent vibration of an airfoil that's usually associated with excessive airspeeds. Flutter can lead to airfoil disintegration, which is of course a very bad thing. Flutter occurs at high speeds, where the normal elastic and inertial dampening qualities of the airfoil prevent excessive vibration. In other words, if a vibration occurs in a control surface, that surface's engineered qualities will dampen the vibration, thus preventing it from increasing in amplitude. Whew! To put it simply, you want to avoid flutter at all costs.
Many years ago, before oscilloscopes and sensitive vibration measuring devices were commonly used, aerodynamicists had a very basic means of identifying an airline's flutter speed. They'd find a skilled test pilot, show him a wheelbarrow full of money, then send him aloft to dive the airplane at dazzling airspeeds. The test pilot's job was to determine the speed at which the airplane experiences flutter.

When he returned-and when his breathing slowed and he regained his ability to speak-he'd tell his tale. He'd inform the engineers about the speed beyond which the airplane experienced flutter. This speed is known as Vd or design dive speed." Source - http://flighttraining.aopa.org/magazine/1998/May/199805_Operating_Within_the_Envelope_Part_1.html



"The dive speed [Vd] is the absolute maximum speed above which the aircraft must not fly. Typically, to achieve this speed, the aircraft must enter a dive (steep descent), as the engines cannot produce sufficient thrust to overcome aerodynamic drag in level flight. At the dive speed, excessive aircraft vibrations [flutter] develop which put the aircraft structural integrity at stake." Source - http://theflyingengineer.com/tag/vdmd/
https://www.isma-isaac.be/past/conf/isma2010/proceedings/papers/isma2010_0321.pdf

Section 3.3 is interesting compared to the above, and a little more current than the above.
Flutter speed to be 15% over maximum design speed
 
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jaydeehess

Senior Member.
My link in post 208 apparently did not work for at least one poster here.
I downloaded it on my tablet and info isn't that easy to get off it. Its a Boeing paper. I found it by searching on google. Let me see this afternoon if the google page is still on my tablet and I'll get the search particulars.
 

jaydeehess

Senior Member.
Flutter also depends on a continuing type of air flow over whatever part is about to experience flutter. Its a resonace effect, changing frequency of the input of energy to the system will destroy the condition for resonance.
In an aircraft that is descending and then at max velocity , turning (and probably not a steady turn) wouldn't that airflow be constantly changing?
 

deirdre

Senior Member.

jaydeehess

Senior Member.
From the link - Bolds mine
<snip>
2 Flutter Clearance Philosophy


The method adopted for flutter clearance involved a combination of pre-flight flutter analysis and

flight flutter testing. The flutter analysis, has been used to identify the flutter characteristics of the aircraft

and establish broad trends over the flight envelope, and thereby provide guidelines for planning the

flutter tests, which includes the configurations to be tested, safe zone to start the tests, flight conditions at

which tests are to be carried out (i.e., flight test points), and the frequency range to be excited. The

analysis also told whether the primary clearance criterion which is the availability of a 15% speed margin

over the flutter speed
(predicted 0% damping) was available for all critical modes. Since the existing

analysis tools do not cater to transonic speeds, this regime was cleared initially based on Wind Tunnel

test results using aeroelastically scaled models, and subsequently through flutter testing,

Flight Flutter tests are mainly aimed at demonstrating that the aircraft is free from flutter and

aeroservoelastic instabilities at all speeds in the flight envelope. Tests are progressively conducted by

increasing the velocity along the constant Mach number lines or Mach number/altitude increments along

constant CAS lines[1]. Tests are initially done in a region of the envelope where high stability is

predicted and subsequently extended to fully cover the envelope. The damping values obtained from the

results of these tests for any global structural mode should be within the limits laid out in the

airworthiness specifications/standards. Clearance was obtained on a „point by point‟ basis, by

computing the frequencies and damping coefficients (%g) of various global aircraft modes from the

flutter test data and ensuring that the damping coefficients are sufficient.


<<snip>>

3.3 Pre-flight Analysis

Flutter computations were carried out using a Finite Element model which was updated based on the

GVT results. The flutter analysis has indicated the following:

1) The MIL requirement of 15% margin in the flutter speed over the maximum design speed is met

at all altitudes.


2) The interaction between modes involving wing antisymmetric bending and antisymmetric wing

Outboard twist (caused by O/B CCM pitching) results in the lowest flutter speed. Since the

damping exhibits a gradual drop with airspeed, this is characterized as mild flutter, as is often the

case with wing-store flutter phenomena. However there is no cause for concern as the flutter

speeds are well beyond the flight Envelope.
 

jaydeehess

Senior Member.
Before anyone suggests I left it out, I should mention that the above testing paper is written with a combat aircraft as the subject.
 

BlindIdiots

Member
Stress is put on the airframe when it experiences speeds past it's VD, the airframe is affected by flutter and then breaks shortly after.
How long is "shortly"? And how has this time period been determined?

The NTSB calculated the peak speed experienced by the aircraft as a value of 0.99 Mach, as the airplane descended through about 22,200 feet msl."

16 seconds after this peak speed was recorded, the FDR and CVR stopped working.

Why do we know it is because structural failure occurred, because the NTSB admits that.

"It is apparent that the left engine and some small pieces of wreckage separated from the airplane at some point before water impact because they were located in the western debris field about 1,200 feet from the eastern debris field."

the left engine and some small pieces of wreckage Separating before the whole of the aircraft impacted the water means they broke off the plane before the rest of the plane hit the water due to the peak speed of .99 mach recorded during it's dive.

What is it called when pieces of an aircraft break off in flight- structural failure.

No speed indication, no reference as to how long the sample airframe was subjected to the airspeed it was experiencing before massive destructive flutter set in.

There was a speed indication, it was about 0.99 Mach, as the airplane descended through about 22,200 feet msl.

It was subjected to that speed for 16 seconds, as that is the period of time from the calculated peak speed and the FDR CVR and stopping their recording due to the structural failure.

How long is "shortly"? And how has this time period been determined?

See above

we must be looking at different reports then the report on the NTSB website lists oodles of evidence - FDR and CVR information, ATC info, reviews of actual wreckage, etc., etc.

You really should read page 118 of the NTSB report to find the Egyptian teams detailed rebuttal of their conclusions and the evidence they base them on.

...... including wind tunnel testing.
Except of course for the wind tunnel testing that was included - eg note 68:
Content from external source
68 Wind tunnel tests and computational fluid dynamics analyses show that a small sideslip angle and/or roll rate could produce large changes in the aerodynamic forces acting on the outboard ailerons at speeds approaching Mach 1.0, but these forces would not likely be strong enough to cause the split elevator condition recorded by the accident airplane.s FDR. For additional information, see Aircraft Performance . Addendum #1.1, Addendum to Group Chairman.s Aircraft Performance Study, including appendixes B and C (correspondence from Boeing, dated April 12 and 16, 2001).

Speeds approaching Mach 1 does not mean wind tunnel tests were done at speeds at mach 1, and the aircraft's peak speed was 0.01 away from Mach 1.

Read from page 118 of the NTSB report to find how their conclusion of how the split elevator condition occurred is flawed.

China Air 006 and TWA 841, for instance. The loss of control was pilot induced. Exacerbated by different circumstances. China Air crew were focused on an engine failure, allowed their airspeed to decay and didn't notice (due to the autopilot being in control) until the A/P reached its limit of control authority and disconnected. The asymmetrical thrust caused the yaw and roll and subsequent out-of-control dive. The "structural failure" did not result in a total failure of the airframe -- it landed safely, and was later repaired and returned to service.

Okay Proudbird, this is incredibly misleading, that aircraft never went past it's vd, it only reached its VMO and did not even exceed it. So it's expected that the aircraft would not completely fail in flight, yet even still it experienced structural failure despite not even exceeding it's VMO and not even touching it's VD.

From Flight 006 NTSB Report

"Although the captain said that the airplane exceeded Vmo twice and also decelerated below 100 KIAS during the dive, all three crew members said that they did not hear the overspeed warning and that the stall warning stickshaker did not activate. Examination of the reliable recorded airspeed data points showed that the Vmo limitation was not exceeded during the descent. However, the recorder data does show airspeeds at or below 100 KIAS. The Safety Board cannot explain why the stall warning stickshaker did not activate, or if it did activate, why it was not felt or heard by the flightcrew."
Content from External Source
This (also from the report) is the structural damage suffered by China Flight 006 despite not even exceeding it's VD and only reaching its VMO

All the damage found on the airplane occurred during the descent and was caused by aerodynamic overload forces.

Wings and Engine Pylons.--The wings were bent or set permanently 2 to 3 inches upward at the wingtips; however, the set was within the manufacturer's allowable tolerances. The left outboard aileron's upper surface panel was broken and the trailing edge wedge was cracked in several places.

Wing and Body Landing Gear.--The left and right wing landing gear uplock assemblies had separated from their attachment points on the fuselage structure. The interior skin and associated ribs on the left and right wing gear inboard doors were damaged in the vicinity of their striker plates and the striker plates also were damaged.

-13-
The doors were damaged in the area where the tires are located when the gears are retracted.

The left and right body landing gear uplock hooks were found in the locked-up position, but the fasteners of their uplock support bracket assemblies had failed at the attach points to the fuselage bulkhead.

The left and right body gear actuator doors had separated, but the forward lateral beams and associated door actuators had remained attached to their respective assemblies, and there were tire marks on the sections of structure attached to the lateral beams. (Note: The uplock assemblies hold the body gear in the retracted position after gear retraction is completed. Except for the body gear tilt assembly, which is pressurized by the No. 1 hydraulic system, the body gear actuators are unpressurized. The tilt assembly is pressurized and remains pressurized so that the body gear wheel bogies can enter or leave their wheel wells without their tires striking the forward wheel well structure.)

Empennage.--The major damage to the empennage was limited to the Auxiliary Unit APU) compartment, the horizontal stabilizers, and elevators. The APU had separated from its mounts and was resting on the two lower tail cone access doors. The forward side of the APU fire bulkhead appeared to be deflected forward in the area adjacent to the two lower attachment fittings and the two lower support rods had buckled. In the area of the APU, there were several punctures in an outward direction on both sides of the tail cone.

The aft pressure bulkhead was undamaged.

A large part of the left horizontal stabilizer had separated from the remainder of the stabilizer. The separated portion, which began at the outboard tip of the stabilizer, was about 10 to 11 feet long and included the entire left outboard elevator. The hydraulic lines from the No. 1 hydraulic system to the left outboard elevator actuator were severed near the actuator. (See figure 8.)

The right horizontal stabilizer incurred a similar separation. The separated portion included the entire tip of the stabilizer. However, beginning about 5 feet inboard of the tip, the separation moved directly aft to the area of the rear spar and then inboard an additional 5 to 6 feet along the forward edge of the box beam area. The separated portion of the stabilizer included the outboard three-quarters of the outboard right elevator. The hydraulic lines to the outboard elevator actuator remained intact. (See figure 8.)

Powerplants.--Except for some rotational scrubbing on the fan rotor rub strips of the Nos. 1 and 4 engines, none of the four engines were damaged during the accident. A boroscope examination of selected accessible areas of the No. 4 engine's front and rear compressors did not disclose any damaged areas.
Content from External Source

TWA 841, although the crew denied it, consensus is (it gets technically complicated) but, let's say they were doing something not approved nor conventional. The loss of control involved another "high-dive" and speeds approaching Mach 1, and as with the China Air flight, excessive G-loads. Yet, even though some structural failure (the leading edge flaps...but THAT was the reason in the first place!) and the landing gear being extended at well above the maximum speed (gear door damage, not really structural...and IIRC the main gear struts were actually bent aftwards a bit), it landed safely, and was repaired and returned to service.

That aircraft did not exceed it's VD, only it's VMO/MMO by just 30 knots!
Yes the damage was repairable but still, the aircraft experienced structural failure despite not even exceeding it's VD, which defines the "structural failure" zone where structural failure becomes imminent.

Merely two examples from the P4T "VG-Diagram" representation that are included on the graph in a disingenuous manner. Their inclusion is misleading and inflammatory.

No, they support the conclusions of P4T because they show that aircraft can still experience structural failure even when they experience speeds that are not even close to VD.

Yet, I am supposed to believe that UA93, UA175, and AA77 can go far beyond the VD range, remain in perfect control, and not experience structural failure when two planes suffered structural failure when they were not even close to approaching their VD speeds.(Of course, that topic is not the debate here)

Now do you see why those flights are on the VG diagram?

Alas, the crux of the matter for a layperson.
"Pilots for 911 Truth" claims that any aircraft that exceeds VD will begin to suffer flutter and structural damage and could not possibly remain in flight.
Others cite instances in which aircraft were definitely outside the limits of design and yet either suffered no damage, or some damage but were repaired and returned to service after, of course, landing safely.

See above.

You should read through the thread again. They are there. Probably could be separated out though.

See above.

Flutter also varies greatly with the air conditions. In calm or laminar air it will occur at a much higher speed than in turbulent air. The testing for flutter is an incredibly complex thing nowadays - and actually has been pretty complex since the 1930s.
http://www.nasa-usa.de/centers/dryden/pdf/88390main_H-2077.pdf

The testing for flutter is an incredibly complex thing nowadays - and actually has been pretty complex since the 1930s.

You should know that VD is based on the onset of flutter by wind tunnel testing, the VD(flutter speed) for a 767 is 420 KCAS [from sea level] to 17,854 ft.

Meaning that at sea level to 17,854 feet , a 767 will experience flutter if it is beyond the range of 420 KCAS.

From the link - Bolds mine
<snip>
2 Flutter Clearance Philosophy
The method adopted for flutter clearance involved a combination of pre-flight flutter analysis and
flight flutter testing. The flutter analysis, has been used to identify the flutter characteristics of the aircraft
and establish broad trends over the flight envelope, and thereby provide guidelines for planning the
flutter tests, which includes the configurations to be tested, safe zone to start the tests, flight conditions at
which tests are to be carried out (i.e., flight test points), and the frequency range to be excited. The
analysis also told whether the primary clearance criterion which is the availability of a 15% speed margin
over the flutter speed (predicted 0% damping) was available for all critical modes. Since the existing
analysis tools do not cater to transonic speeds, this regime was cleared initially based on Wind Tunnel
test results using aeroelastically scaled models, and subsequently through flutter testing,
Flight Flutter tests are mainly aimed at demonstrating that the aircraft is free from flutter and
aeroservoelastic instabilities at all speeds in the flight envelope. Tests are progressively conducted by
increasing the velocity along the constant Mach number lines or Mach number/altitude increments along
constant CAS lines[1]. Tests are initially done in a region of the envelope where high stability is
predicted and subsequently extended to fully cover the envelope. The damping values obtained from the
results of these tests for any global structural mode should be within the limits laid out in the
airworthiness specifications/standards. Clearance was obtained on a „point by point‟ basis, by
computing the frequencies and damping coefficients (%g) of various global aircraft modes from the
flutter test data and ensuring that the damping coefficients are sufficient.
<<snip>>
3.3 Pre-flight Analysis
Flutter computations were carried out using a Finite Element model which was updated based on the
GVT results. The flutter analysis has indicated the following:
1) The MIL requirement of 15% margin in the flutter speed over the maximum design speed is met
at all altitudes.
2) The interaction between modes involving wing antisymmetric bending and antisymmetric wing
Outboard twist (caused by O/B CCM pitching) results in the lowest flutter speed. Since the
damping exhibits a gradual drop with airspeed, this is characterized as mild flutter, as is often the
case with wing-store flutter phenomena. However there is no cause for concern as the flutter
speeds are well beyond the flight Envelope.

MIL Requirement refers to a United States Military Standard, which means that a requirement of a 15% margin in the flutter speed(VD) over the maximum design speed being met at all altitudes is only a requirement for military aircraft, which is what this document is referring to.

There is no evidence that that requirement is present in Boeing commercial airliners.

Such a requirement is also not present in FAR 25.335 which refers to design airspeed for transport category airliners.
 
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MikeC

Closed Account
What is it called when pieces of an aircraft break off in flight- structural failure.

Indeed - even a panel coming off in flight is a structural failure - and because of that it should be obvious that not all structural failure results in eth disintegration of the aircraft or loss of control.

And limits are not "hard" - you do not fall apart immediately upon breaching them - eg see this article about an Air Fiji A330 that experienced 2.9g landing which overstressed its landing gear......but it subsequently still flew another sector!


That aircraft did not exceed it's VD, only it's VMO/MMO by just 30 knots!
Yes the damage was repairable but still, the aircraft experienced structural failure despite not even exceeding it's VD, which defines the "structural failure" zone where structural failure becomes imminent.

Your examples are excellent evidence supporting the case that "structural failure" does not equate to loss of control or disintegration

MikeC said:
...... including wind tunnel testing.
Except of course for the wind tunnel testing that was included - eg note 68:
Content from external source
68 Wind tunnel tests and computational fluid dynamics analyses show that a small sideslip angle and/or roll rate could produce large changes in the aerodynamic forces acting on the outboard ailerons at speeds approaching Mach 1.0, but these forces would not likely be strong enough to cause the split elevator condition recorded by the accident airplane.s FDR. For additional information, see Aircraft Performance . Addendum #1.1, Addendum to Group Chairman.s Aircraft Performance Study, including appendixes B and C (correspondence from Boeing, dated April 12 and 16, 2001).
Click to expand...
Speeds approaching Mach 1 does not mean wind tunnel tests were done at speeds at mach 1, and the aircraft's peak speed was 0.01 away from Mach 1.

Read from page 118 of the NTSB report to find how their conclusion of how the split elevator condition occurred is flawed.

I wasn't addressing the adequacy or nature of wind tunnel testing - the assertion was that there was NO WIND TUNNEL TESTING DONE AT ALL.

My point was that this was not true.
 

BlindIdiots

Member
That aircraft did not exceed it's VD, only it's VMO/MMO by just 30 knots!
Yes the damage was repairable but still, the aircraft experienced structural failure despite not even exceeding it's VD, which defines the "structural failure" zone where structural failure becomes imminent.
Your examples are excellent evidence supporting the case that "structural failure" does not equate to loss of control or disintegration

The only reason they did not equate to complete structural failure is because that aircraft exceeded VMO, where structural failure is not even guaranteed, yet it still happened.

Flight 006 and 841 were experiencing speeds far before the VD range where structural failure becomes imminent and still experienced structural failure.

I notice that I am repeating myself, do you understand what my point is yet?
 

BlindIdiots

Member
What is it called when pieces of an aircraft break off in flight- structural failure.
Indeed - even a panel coming off in flight is a structural failure - and because of that it should be obvious that not all structural failure results in eth disintegration of the aircraft or loss of control.
And limits are not "hard" - you do not fall apart immediately upon breaching them - eg see this article about an Air Fiji A330 that experienced 2.9g landing which overstressed its landing gear......but it subsequently still flew another sector!

The left engine fell off when EA990 was experiencing the speeds the NTSB calculated.
 

BlindIdiots

Member
I wasn't addressing the adequacy or nature of wind tunnel testing - the assertion was that there was NO WIND TUNNEL TESTING DONE AT ALL.
My point was that this was not true.

I understand, I was just using that quote from the NTSB report to show there are problems with it.
 

WeedWhacker

Senior Member
Flight 006 and 841 were experiencing speeds far before the VD range where structural failure becomes imminent and still experienced structural failure.

Yes. But, they also experienced very high G-loads too. Something not seen with UAL175.

And China Air 006 and TWA 841 all landed safely, correct? Again, the term "structural failure" is used misleadingly by P4T on that VG Diagram example.

This is rather blatantly obvious.
 

BlindIdiots

Member
And China Air 006 and TWA 841 all landed safely, correct? Again, the term "structural failure" is used misleadingly by P4T on that VG Diagram example.

The structural failure zone of that diagram is located in the VD range, while Flight 006 and 841 are located in the VMO range, or not in the structural failure zone. Yet they still experienced it.
 

WeedWhacker

Senior Member
The left engine fell off when EA990 was experiencing the speeds the NTSB calculated.

Prove this. How did you determine this, since the power to the FDR and CVR had already been cut off when this allegedly happened. There were two debris fields on the ocean bottom, only 1,200 feet apart center-to-center. One field had the left engine, small pieces of wreckage (including two wing panel portions), fuselage skin, stabilizer skin and the majority of the nose landing gear assembly (NTSB Report, page #34).

So, did the left engine "fall off" along with the nose gear strut? They were in the same location on the seabed.

Or, isn't it much more rational to surmise that the airplane was mostly intact on impact with the water's surface, and was fractured at that point, with debris falling through the water and settling in the patterns seen??
 

BlindIdiots

Member
Prove this. How did you determine this, since the power to the FDR and CVR had already been cut off when this allegedly happened. There were two debris fields on the ocean bottom, only 1,200 feet apart center-to-center. One field had the left engine, small pieces of wreckage (including two wing panel portions), fuselage skin, stabilizer skin and the majority of the nose landing gear assembly (NTSB Report, page #34).
So, did the left engine "fall off" along with the nose gear strut? They were in the same location on the seabed.
Or, isn't it much more rational to surmise that the airplane was mostly intact on impact with the water's surface, and was fractured at that point, with debris falling through the water and settling in the patterns seen??

"It is apparent that the left engine and some small pieces of wreckage separated from the airplane at some point before water impact because they were located in the western debris field about 1,200 feet from the eastern debris field."

They fell off before water impact, not on water impact
 

WeedWhacker

Senior Member
The structural failure zone of that diagram is located in the VD range, while Flight 006 and 841 are located in the VMO range, or not in the structural failure zone.

You sure about that claim?

Flight 006 and Flight 841 are placed on the chart in a red zone labelled (by P4T) as "Structural failure". But my point is, they are also located up high in the chart, indicating the high G-load factors.
 

WeedWhacker

Senior Member
They fell off before water impact, not on water impact

The nose gear strut "fell off" the airplane?? It "fell out" of the nose wheel well?

DO you really want to stand by this assertion?

Adding...the FDR and CVR were not recording. What leads to the conclusion that "They fell off before impact"? Is there a video I can watch that proves this?
 

BlindIdiots

Member
They fell off before water impact, not on water impact
The nose gear strut "fell off" the airplane?? It "fell out" of the nose wheel well?
DO you really want to stand by this assertion?

I mean't the left engine.


You sure about that claim?
Flight 006 and Flight 841 are placed on the chart in a red zone labelled (by P4T) as "Structural failure". But my point is, they are also located up high in the chart, indicating the high G-load factors.

Yes, I will say they are a bit too high, but that is all the faults I see.
 

WeedWhacker

Senior Member
I mean't the left engine.

OK. But, as I wrote a few posts up above, the nose gear strut assembly was also in the same debris field as the left engine. How could this be, if the left engine broke away from the airframe before impact with the water?

And I want to once again emphasize a very important point: Egypt 990 experienced severe G-loads as part of the accident sequence. UAL 175 did not.

Also from the NTSB Report (Egypt 990) on Page #34:
"The locations of the two main wreckage debris fields were consistent with the accident airplane's flightpath, as indicated by the primary radar data."
 
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BlindIdiots

Member
I mean't the left engine.
OK. But, as I wrote a few posts up above, the nose gear strut assembly was also in the same debris field as the left engine. How could this be, if the left engine broke away from the airframe before impact with the water?

So, you are saying that you do not agree with the NTSB then?

The left engine fell off on the same trajectory as the plane was going, is it not possible that the plane would then follow this same trajectory, causing the debris to scatter the way it did?
 

jaydeehess

Senior Member.
The structural failure of flight 587 illustrates that forces generated by means other than velocity are as important as those generated simply by velocity. For the most part flight 175 was in a low angle descent with little manoeuvering. It was only on the last ten seconds that a left bank was performed. It was a constant or increasing bank, not a reversal of control commands.
It is entirely possible that structural cracks such as quoted above by blindidiots, had developed in 175, it's possible that some panels came off and are not visible in the videos due to their size, location, or, if this occurred directly before impact, among the debris coming off the tower a split second later.
Had 175 deployed landing gear I am sure that would have been catastrophic, had it entered into a large pitch down, that would have been catastrophic, had the pilot tried to roll to his right or apply full stop right rudder after already having rolled left, that would have been catastrophic..

The characterization of Vd as "flutter speed" does not appear to be backed by any solid evidence presented thus far. In addition, flutter is not a simple concept that could apply to any one speed as flutter development in different airframe components occurs at different combinations of speed and aircraft attitude.
Flutter is a consequence of resonance and is destructive only if it builds to high enough amplitude. Getting to a high amplitude resonant condition requires time at the specific combination of speed and aircraft attitude for any particular air frame component.
 
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WeedWhacker

Senior Member
So, you are saying that you do not agree with the NTSB then?

Do NOT attempt to put words into my mouth!


The left engine fell off on the same trajectory as the plane was going, is it not possible that the plane would then follow this same trajectory, causing the debris to scatter the way it did?

Now you are just making things up, and speculating? OK, I'll play along: The answer is "no".

Basic physics 101. When something "falls off" an airplane, it is now going to arc in a path determined by two vectors of motion: Its forward velocity component as a (former) part of the airplane structure, and gravity. The airplane, however, will still have a wing producing lift and will travel on its own vector as a result.

This is rather obvious, at least to me.

Here, this video shows the arc of a falling object with a forward velocity vector:

The airplane in the animation is in level flight, but even if it were descending at an angle, say of 40° to the horizon, the object "dropped" will still follow an arced path.
 
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jaydeehess

Senior Member.
It is difficult to imagine how aerodynamic forces could tear the nose gear out of an aircraft while keeping the rest of it intact except for one engine.
 

BlindIdiots

Member
So, you are saying that you do not agree with the NTSB then?
Do NOT attempt to put words into my mouth!

No, I am not putting words into your mouth, you said this:

OK. But, as I wrote a few posts up above, the nose gear strut assembly was also in the same debris field as the left engine. How could this be, if the left engine broke away from the airframe before impact with the water

Yet the NTSB said that it did break from the airframe before impact with the water.

"It is apparent that the left engine and some small pieces of wreckage separated from the airplane at some point before water impact because they were located in the western debris field about 1,200 feet from the eastern debris field."


The left engine fell off on the same trajectory as the plane was going, is it not possible that the plane would then follow this same trajectory, causing the debris to scatter the way it did?
Now you are just making things up, and speculating? OK, I'll play along: The answer is "no".
Basic physics 101. When something "falls off" an airplane, it is now going to arc in a path determined by two vectors of motion: Its forward velocity component as a (former) part of the airplane structure, and gravity. The airplane, however, will still have a wing producing lift and will travel on its own vector as a result.

You seriously are disagreeing with the NTSB here, who said that it is apparent that the engine broke off before water impact because it was located in a different debris field, it is possible however, for the rest of the aircraft to end up in said debris field.
 

jaydeehess

Senior Member.
What's the beef anyway if 990 was at 0.99Mach and at high g when its engine tore off? Flight 175 was no where near 0.99 Mach and no under the same g's
 

WeedWhacker

Senior Member
Yet the NTSB said that it did break from the airframe before impact with the water.
"It is apparent that the left engine and some small pieces of wreckage separated from the airplane at some point before water impact because they were located in the western debris field about 1,200 feet from the eastern debris field."

OK, I have now found that in the NTSB report, from Page #36 (would help if you could cite this for me, saves time).

And here is the exact sentence: "Although the recovery location of and damage to the left engine were consistent with it separating from the airplane before impact ..."

Not quite what you had in "quotes" there! Now then, thanks for helping me to hunt through the NTSB Report to find that nugget...however, the question remains "when" did it separate (if it did). One second before impact? Two? One-half? Based on the debris field, it's safe to surmise that a very brief amount of time occurred between separation (if it happened) and airplane impact. (Otherwise, the left engine would be somewhere else, and not surrounded by other airplane debris).

Yet again, I (third time?) must point out the G-loads involved! Also, are you aware of the frangible engine mounting attachment points? If you wish I could find a link for you, but maybe it'd be better to do the research yourself. **BTW, remember American Airlines 191, at KORD? A different airplane (DC-10), but its engine came off during a normal takeoff. Might want to look into that tragedy.

I bring this up because with the "gyrations" that airplane was enduring during the accident sequence (and the G-loads...fourth time), the stress on those engine mounting points would have been severe.

Again, NOT seen on UAL 175.
 

Mick West

Administrator
Staff member
You should know that VD is based on the onset of flutter by wind tunnel testing, the VD(flutter speed) for a 767 is 420 KCAS [from sea level] to 17,854 ft.
Meaning that at sea level to 17,854 feet , a 767 will experience flutter if it is beyond the range of 420 KCAS.

Then Why do federal regulations say:
The airplane shall be designed to be free from flutter of wing and
tail units, including all control and trim surfaces, and from divergence (i.e. unstable
structural distortion due to aerodynamic loading), at all speeds up to 1.2 VD.
Content from External Source
See full discussion here:
https://www.metabunk.org/threads/de...roelastic-flutter-in-the-events-of-9-11.3359/
 

jaydeehess

Senior Member.
Then Why do federal regulations say:
The airplane shall be designed to be free from flutter of wing and
tail units, including all control and trim surfaces, and from divergence (i.e. unstable
structural distortion due to aerodynamic loading), at all speeds up to 1.2 VD.
Content from External Source
See full discussion here:
https://www.metabunk.org/threads/de...roelastic-flutter-in-the-events-of-9-11.3359/
I could swear I said much the same thing.
Thanks Mick
 

jaydeehess

Senior Member.
Damping decreases with speed, as a general rule, but damping would also increase as load increases. Stress a structure and its is less likely to resonate.
Of course load increases stress which, while it would increase damping thus decrease probability of flutter, it also has a limit, fracture.
 
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