Why Flight 93?

[Slayhamlet]

Isn't that picture the fruit of Killtown's vast intellect?

 

[Gravy]

Isn't that picture the fruit of Killtown's vast intellect?

Killtown didn't draw it, but he includes it on his flight 93 evidence page.

 

[GregoryUrich]

Tell you what, why don't you whip up a little drawing of what you think the aircraft's orientation was at the moment of impact. Be sure to include the 40° pitch down, 150° right roll, and -20° angle of attack. Then we can see if your interpretation of what those numbers mean to the orientation of an aircraft are correct or not.

I'm very clear on the orientation. The AoA tells us nothing about the orientation relative to the ground only relative to the velocity vector.

 

[Corsair 115]

The AoA tells us nothing about the orientation relative to the ground only relative to the velocity vector.

Uh, yes it does. A 0° angle of attack puts the fuselage of the aircraft in a different orientation relative to the ground than does a 20° or -20° AoA. Think of an aircraft coming in to land - you don't think that nose high attitude changes the direction the fuselage is pointing relative to the ground as compared to a jet flying level over the ground?

 

[Unfit4Command]

“They expect us to believe that a 757 loaded with at least 5,000 gallons of jet fuel crashed into the ground at 580 miles per hour at 45 degrees and basically disappeared upon impact. Let’s say it even burrowed in 40 feet, you’d still have the plane sticking out at that point.”
-Dylan Avery on Flight 93, 9/11 Conspiracy Files

That picture just reminded me of when Dylan said that in one of his interviews.

 

[beachnut]

I'm very clear on the orientation. The AoA tells us nothing about the orientation relative to the ground only relative to the velocity vector.

What are you talking about? Get some aero classes under the belt before posting garbage, or stop posting garbage. You are embarrassing youself.

Who has the tail sticking out of the ground. A 600 mph tail section will not be sticking out of the ground, unless the ground was 1 mile of Aerogel.

I hope Gregory is not a tail out of the ground guy. Or a crushed all in the ground guy. Gee just the impact alone sends some stuff flying at great speed, like instruments bodies on the flight deck expelled. Engines flung as the rolling moment slashes the wings into the ground.

Funny, your post impeaches your post. How do you do that?

 

[GregoryUrich]

Uh, yes it does. A 0° angle of attack puts the fuselage of the aircraft in a different orientation relative to the ground than does a 20° or -20° AoA. Think of an aircraft coming in to land - you don't think that nose high attitude changes the direction the fuselage is pointing relative to the ground as compared to a jet flying level over the ground?

Sorry, you don't get it. A plane can be diving towards the ground with 0 degrees angle of attack. Pitch is relative to the horizon and the ground if the ground is level.

 

[beachnut]

Sorry, you don't get it. A plane can be diving towards the ground with 0 degrees angle of attack. Pitch is relative to the horizon and the ground if the ground is level.

Not for long.

 

[GregoryUrich]

The angle of attack, AOA, was not zero. Oops. Told you to get some aero classes before making, now a foolish post. No a plane can have many different AOAs as it hits the ground (in different cases, are you really this challenged on Aero stuff). Aero.

That was an example for Corsair. If you think a little before posting again I think you will agree that AoA has nothing to do with orientation relative to the ground, it is relative to the velocity vector as I said before. If you don't agree you better check your textbook.

 

[beachnut]

That was an example for Corsair. If you think a little before posting again I think you will agree that AoA has nothing to do with orientation relative to the ground, it is relative to the velocity vector as I said before. If you don't agree you better check your textbook.

No I will not. Please, show me the instument on flight 93 that reports the Velocity Vector? Come-on, please be quick, ok?

 

[apathoid]

I could be wrong, but with the plane being inverted - a negative AoA(trailing edge of the AoA vane being down) is actually positive when trying to work out the flight path vector, or velocity vector. 40 and 20 tells me that the plane struck at 60 degrees relative to normal, at a 20 degree nose up attitude, relative to the flight path. Somebody correct me if I'm wrong..

 

[beachnut]

I could be wrong, but with the plane being inverted - a negative AoA(trailing edge of the AoA vane being down) is actually positive when trying to work out the flight path vector, or velocity vector. 40 and 20 tells me that the plane struck at 60 degrees relative to normal, at a 20 degree nose up attitude, relative to the flight path. Somebody correct me if I'm wrong..

Level flight at attitude is just around -16 on the FDR. The reading has to be adjusted. Takeoff is -7, cruise is -16, impact -20. Our truther "scholar" is off trying to find the velocity vector readout. I wonder if people even think about how complicated but simple flying is. I am not sure what the center of mass was doing when it hit. But AOA and Pitch can help, but they would only be used in an accident investigation to confirm ball park stuff. And since 93 was in the ball park, our truther "scholar" is wasting time out of his field. But I will learn something form this.

 

[rwguinn]

No I will not. Please, show me the instument on flight 93 that reports the Velocity Vector? Come-on, please be quick, ok?

Beech:
I apply to your expertise here.
IS AoA reported as "nose up" regardless of aircraft orientation; i.e., is it WRT the Earth, or is it reported as what an "Up Elevator" command would produce?
Generally, since the lift vector is out of the top surface of the wing, and +AoA will increase lift (up to a point, as any true pilot knows) one would expect Aoa indicaters to be referenced to that fact, and be consistent. Pitch angle as reported by the FDR also has me confused--is it also consistent with nose attitude in upright flight, or what.
If these instruments are gyroscopicly stabilized, did the gyro tumble? (or can it? Inertial references are probably not succeptable to that phenomenon)
What I (vaguely) remember from my NASA days at Edwards is that in inverted flight, +AoA was nose toward the ground, and in normal flight, it was nose to the sky--I.e., consistent with pilot position.
But of course, these were aircraft which were expected to become inverted at some point (F-104, F8, etc.), and test aircraft which might end up in just about any attitude and position.
Thanks--and any other rocket scientist answer if you read it first...

 

[apathoid]

Beech:
I apply to your expertise here.
IS AoA reported as "nose up" regardless of aircraft orientation; i.e., is it WRT the Earth, or is it reported as what an "Up Elevator" command would produce?
Generally, since the lift vector is out of the top surface of the wing, and +AoA will increase lift (up to a point, as any true pilot knows) one would expect Aoa indicaters to be referenced to that fact, and be consistent. Pitch angle as reported by the FDR also has me confused--is it also consistent with nose attitude in upright flight, or what.
If these instruments are gyroscopicly stabilized, did the gyro tumble? (or can it? Inertial references are probably not succeptable to that phenomenon)
What I (vaguely) remember from my NASA days at Edwards is that in inverted flight, +AoA was nose toward the ground, and in normal flight, it was nose to the sky--I.e., consistent with pilot position.
But of course, these were aircraft which were expected to become inverted at some point (F-104, F8, etc.), and test aircraft which might end up in just about any attitude and position.
Thanks--and any other rocket scientist answer if you read it first...

AoA in a 757 is measured by a vane on the nose, although I'm quite sure the Inertial Reference System can compute this also. Negative and positive AoA should be relative to the measuring device, that's why I said when the plane is inverted - negative and positive 'flip'.

 

[apathoid]

Level flight at attitude is just around -16 on the FDR. The reading has to be adjusted. Takeoff is -7, cruise is -16, impact -20. Our truther "scholar" is off trying to find the velocity vector readout.
{snip}

Ah, so it's a pretty useless reading. Thanks.

 

[beachnut]

Beech:
I apply to your expertise here.
IS AoA reported as "nose up" regardless of aircraft orientation; i.e., is it WRT the Earth, or is it reported as what an "Up Elevator" command would produce?
Generally, since the lift vector is out of the top surface of the wing, and +AoA will increase lift (up to a point, as any true pilot knows) one would expect Aoa indicaters to be referenced to that fact, and be consistent. Pitch angle as reported by the FDR also has me confused--is it also consistent with nose attitude in upright flight, or what.
If these instruments are gyroscopicly stabilized, did the gyro tumble? (or can it? Inertial references are probably not succeptable to that phenomenon)
What I (vaguely) remember from my NASA days at Edwards is that in inverted flight, +AoA was nose toward the ground, and in normal flight, it was nose to the sky--I.e., consistent with pilot position.
But of course, these were aircraft which were expected to become inverted at some point (F-104, F8, etc.), and test aircraft which might end up in just about any attitude and position.
Thanks--and any other rocket scientist answer if you read it first...

http://www.aerospaceweb.org/question/aerodynamics/q0165.shtml

The web page shows AOA, I never thought about the AOA much in the T-38 (but we used it), the plane could not be crashed trashing around at 20,000 feet upside-down, sideways or any other attitude a crazy kid could do. In the Tanker it was normalized and we took off at .6, and there were marks on the AOA for endurance, around .4, and max range, about .2. The AOA is good for getting max lift, endurance, and max range.

In the T-38 we had a doughnut with two sets of '' at the top of the o and bottom of the o. When the o was green and on we were max lift, on the burble. On final we would be green. Not used much but to check your loops and landing. And since that was in 1975, I may of forgot something.

AOA is a good check if you have an instrument to show it. It beats looking up max range speeds in the books, just make the AOA good for the thing you want, and cross check it with your know speeds. But many argued the AOA in the KC-135 was not that accurate for cruise but it still was close.

I think the web page verifies the things you are saying. http://www.aerospaceweb.org/question/aerodynamics/q0165.shtml

 

[rwguinn]

AoA in a 757 is measured by a vane on the nose, although I'm quite sure the Inertial Reference System can compute this also. Negative and positive AoA should be relative to the measuring device, that's why I said when the plane is inverted - negative and positive 'flip'.

I'm not quite following here...
Let us assume a coordinate system, such that
+ X axis (FS) is aft.
+Z axis (WL) is up, i.e., vertical tail is +WL (Z axis).
+Y (+BL) is then out the left wing.
These references do not change, regardless of aircraft orientation.
The vane (fairly typical--test aircraft used 4 holes in a ball-end probe) has as its reference the axis of the tube it is mounted on (or aircraft x-axis)
Thus, a nose-up attitude (+AoA) would indicate a + rotation about the Y axis, regardless of the aircraft attitude in 3D space, right? Or am I totally hosed, here?
Then we can get into pitch attitude...

 

[apathoid]

I'm not quite following here...
Let us assume a coordinate system, such that
+ X axis (FS) is aft.
+Z axis (WL) is up, i.e., vertical tail is +WL (Z axis).
+Y (+BL) is then out the left wing.
These references do not change, regardless of aircraft orientation.
The vane (fairly typical--test aircraft used 4 holes in a ball-end probe) has as its reference the axis of the tube it is mounted on (or aircraft x-axis)
Thus, a nose-up attitude (+AoA) would indicate a + rotation about the Y axis, regardless of the aircraft attitude in 3D space, right? Or am I totally hosed, here?
Then we can get into pitch attitude...

The AoA vane on Boeings is like a miniature airplane wing that swivels about the lateral axis(y axis), there are no pressure sensing holes in this type of vane. If the plane is rolled upside down, negative to the vane should actually be positive, but since 757s are semi-smart, there may be may more inputs involved in AoA/Stall warning system - so the airplane will still know when it's stalling when inverted.

ETA: Here is a good picture of an AoA vane(at right)
http://www.sensors.goodrich.com/images/aoapic.gif

 

[rwguinn]

The AoA vane on Boeings is like a miniature airplane wing that swivels about the lateral axis(y axis), there are no pressure sensing holes in this type of vane. If the plane is rolled upside down, negative to the vane should actually be positive, but since 757s are semi-smart, there may be may more inputs involved in AoA/Stall warning system - so the airplane will still know when it's stalling when inverted.

ETA: Here is a good picture of an AoA vane(at right)
http://www.sensors.goodrich.com/images/aoapic.gif

Don't get side-tracked on the vane--I know what they are--I am just trying to get a view as to what they reference...
And just how smart can any system be when thrown so far outside its operating parameters? My best SWAG is that they continue to read from reference 0, which is straight and level flight, +alpha is + rotaion about Y-axis, +Beta is +rotation about Z (Use the Right Hand rule, guys) if for no other reason than to help the investigators figure out how the hell it got so far out of whack when they pick up the pieces.
I will assume that Boeing, the FAA, NSTB, and those guys have answers, but I can also see why they don't publish that sort of stuff...

 

[apathoid]

And just how smart can any system be when thrown so far outside its operating parameters?

Too true!

My best SWAG is that they continue to read from reference 0, which is straight and level flight, +alpha is + rotaion about Y-axis, +Beta is +rotation about Z (Use the Right Hand rule, guys) if for no other reason than to help the investigators figure out how the hell it got so far out of whack when they pick up the pieces.

Yeah, I've gathered that you know what AoA vanes are - I just wanted to throw out some gee-whiz info for others who may not have a clue what they are and what they do. And to add a little, the whole purpose of the AoA vane is stall warning, outside of that and the FDR - it has no outputs. No gauges, no cues on the Electronic Flight Instruments, nada!

And as beachnut mentioned, it appears that readings were fluky the entire flight.

Ideally, they should work exactly the same upside down. positive airflow is positive airflow. But do they? Paging R.Mackey!!