Physics Response to Flight 77 Trajectory Speculation

[Anti-sophist]

Even with large changes in pitch an accelerometer essentially measures the acceleration perpendicular to the earth. This is most important in maneuvering as this is the most significant stress on an aircraft. The most significant longitudinal stress would be from engine power and even in an F-15 or F-22 in full afterburner this would not produce anything even close to excessive stress.

For the record, the aircraft has a 3-axes accelerometer and measures all three: longitudinal, lateral, and vertical. All three measurements are present in the FDR data.

Regarding accelerations - what would vertical acceleration show if the plane was flying upside down?

I like this question. I'm fairly certain that the answer should be -1 G. In order to remain in level flight, upside down, the plane (and the people inside) must exert their own weight worth of force in the opposite direction "as usual".

In this case, "positive" G is defined as directly up relative to the plane of the aircraft. In normal level flight, you exert your own weight upward, relative to the aircraft. In upside down flight, you'd exert that force downward, relative to the aircraft.

 

[celestrin]

I'm fairly certain that the answer should be -1 G. In order to remain in level flight, upside down, the plane (and the people inside) must exert their own weight worth of force in the opposite direction "as usual".

That's not only logically sound, it also appears my search-fu is working better today than the last time I tried this. At least this manufacturer's test procedures appear to show that an inverted accelerometer should indeed show -1.

(a) Hold instrument motionless with dial in vertical position and +5g at top; hand assemblies indicate +1 +/- 0.2g.
(b) Hold instrument motionless with dial in vertical position and -3g at top; hand assemblies indicate -1 +/- 0.2g.
(c) Hold instrument motionless with dial horizontal; hand assemblies indicate 0 ± 0.2g.
(d)Check that friction does not exceed +/- 0.2g with memory pointer engaged.

Bolding mine.

 

[Reheat]

I like this question. I'm fairly certain that the answer should be -1 G. In order to remain in level flight, upside down, the plane (and the people inside) must exert their own weight worth of force in the opposite direction "as usual".

Yes, that is correct, -1 G for level unaccelerated inverted flight.

 

[Reheat]

For the record, the aircraft has a 3-axes accelerometer and measures all three: longitudinal, lateral, and vertical. All three measurements are present in the FDR data.

Just to clarify, I believe you are addressing a B-757 here. As far as I know no USAF Fighter has an FDR and all of the accelerometers are vertical only.

 

[rwguinn]

Just to clarify, I believe you are addressing a B-757 here. As far as I know no USAF Fighter has an FDR and all of the accelerometers are vertical only.

Actually, I am pretty sure the g-meters in fighters measure actual "g" in all 3 directions--IOW, they are oriented with the Z-axis FIXED perpendicular to the wing, X fore/aft.
Because we ain't worried about the pilot so much--he's one guy and in charge of his own destiny (and we hope, the aircraft)--but we do need to know if he exceeded airframe allowables...

 

[Reheat]

Actually, I am pretty sure the g-meters in fighters measure actual "g" in all 3 directions--IOW, they are oriented with the Z-axis FIXED perpendicular to the wing, X fore/aft.

Well yes, when the aircraft is banked and pulling G's they are recorded on the indicator, but that's vertical isn't it. I had never thought of that being lateral. The only time lateral G's are significant is during use of vectored thrust of the F-22 and even then I doubt there is a problem with limits. They do record positive and negative G's and work during banked flight. If that's what is meant by 3 axis, then you're right.

Because we ain't worried about the pilot so much--he's one guy and in charge of his own destiny (and we hope, the aircraft)--but we do need to know if he exceeded airframe allowables...

Hehehehehe! You do realize there is a reset button which when pushed returns the recording needle to zero. That's the only record of any G during flight. Unless the pilot is very honest it's probably similar to an incriminating CVR that has an inadvertent erasure. Well, unless it's really excessive then I think most would admit it to maintenance.

This was somewhat of an issue during the period of the Century Series Fighters because Max positive G was limited to about 7.33, but in today's Fighters with a 10 G limit, it is not a problem simply because that exceeds the tolerance of most pilots. The vast majority of F-16 accidents continue to be LOC (Loss of Consciousness) even while staying within airframe G limits.

 

[rwguinn]

Well yes, when the aircraft is banked and pulling G's they are recorded on the indicator, but that's vertical isn't it. I had never thought of that being lateral. The only time lateral G's are significant is during use of vectored thrust of the F-22 and even then I doubt there is a problem with limits. They do record positive and negative G's and work during banked flight. If that's what is meant by 3 axis, then you're right.

yepper.. No gymbals that I know of...

Hehehehehe! You do realize there is a reset button which when pushed returns the recording needle to zero. That's the only record of any G during flight. Unless the pilot is very honest it's probably similar to an incriminating CVR that has an inadvertent erasure. Well, unless it's really excessive then I think most would admit it to maintenance.

This was somewhat of an issue during the period of the Century Series Fighters because Max positive G was limited to about 7.33, but in today's Fighters with a 10 G limit, it is not a problem simply because that exceeds the tolerance of most pilots. The vast majority of F-16 accidents continue to be LOC (Loss of Consciousness) even while staying within airframe G limits.

I've been working Lightning II for the past 5 years...

 

[jaydeehess]

Ok, next question then.
Does the acellerometer data on the FDR tell us what idealized trajectory Ryan should have been working on?

By that I mean that Ryan did his calculations while idealizing the flight path as a parabola.

I know we are using P4T's calculations and showing them to be in error. That ship has sailed now with P4T's acknowledgment that their calculations were, to be kind, in error.

We have the height of the bottom of the plane, the horizontal velocity of the aircraft as it passes the tower and which remains constant, the vertical and horizontal distances, and now the FDR recorded changes in vertical g forces. Does the empirical evidence of the FDR data match a trajectory that would take the plane then over the tower given these initial conditions?

 

[Reheat]

Does the empirical evidence of the FDR data match a trajectory that would take the plane then over the tower given these initial conditions?

IMHO, you're asking for too much speculation on the precise flight path. We don't know that.

Those spikes in the graph posted by Beachnut could possibly be the roll in and out of turns, but that would be sheer speculation. The two main spikes are either too far or too close to be a roll-ups to avoid the tower as indicated by the VDOT folks.

I don't think we know enough about the precise (and it does need to be precise) flight path to even attempt using the G data for any calculations.

The only thing that G graph shows is that there is missing data. Notice there is no trend toward a continuous descent as there should have been except at the very end. Well, even that is speculation as the G indications would depend entirely on how smoothly the pilot made the pitch changes.

If the pft loons have extracted the altitude data correctly (there is no guarantee they have) then there should have been a pretty good descent rate followed by the G's Ryan calculated in one of the stated cases. We don't see that at all, so that is the best indicator of missing data. I'd say he was just beginning his final descent toward the light poles as the data ends.

I am very suspicious of the FDR Data as the cvs file, the animation, and the raw data do not agree according to the amateur experts. They all seem to be different and that doesn't make sense, but it does not indicate an InSiDe JoOb.

 

[uk_dave]

Spin Spin Sugar

johndoex:
By the way, i see many JREFers touting they were the influence for pointing out our errors. That is also wrong. Actually, one of our own core members pointed it out initially. JREFers of course spent the subsequent days, 3 threads (one being removed and one having to be locked due to JREF typical behavior) and a good amount of their free time behind their screens trying to prove us wrong. Once they found the same mistake, they claim "victory". There are other errors they didnt even catch, including their own.

http://www.abovetopsecret.com/forum/thread341556/pg4

Seems they owe TC an apology for making him scurry over here waving his 'smoking gun' around when they already knew there were catastrophic errors in their premise.

Or they're just lying again.

 

[DGM]

http://pilotsfor911truth.org/descent_rate031308.html
03/20/08 - Update: For those who have been following the thread linked in the right margin, this will be redundant. The calculations below used for the purpose of this article are in error. We are currently reviewing the calculations and will publish a revision with the proper formula(s)/calculations consistent with the premise of this article. We apologize for any confusion and thank you for your understanding.

Now that's going to be tough to do. Maybe they can use some of the "new" math.

 

[Confuseling]

Hehehe. That's not a retraction! I don't know what that is. Brazen, might be the word - definitely begins with 'b' anyway.

 

[GregoryUrich]

IMHO, you're asking for too much speculation on the precise flight path. We don't know that.

Those spikes in the graph posted by Beachnut could possibly be the roll in and out of turns, but that would be sheer speculation. The two main spikes are either too far or too close to be a roll-ups to avoid the tower as indicated by the VDOT folks.

I don't think we know enough about the precise (and it does need to be precise) flight path to even attempt using the G data for any calculations.

The only thing that G graph shows is that there is missing data. Notice there is no trend toward a continuous descent as there should have been except at the very end. Well, even that is speculation as the G indications would depend entirely on how smoothly the pilot made the pitch changes.

If the pft loons have extracted the altitude data correctly (there is no guarantee they have) then there should have been a pretty good descent rate followed by the G's Ryan calculated in one of the stated cases. We don't see that at all, so that is the best indicator of missing data. I'd say he was just beginning his final descent toward the light poles as the data ends.

I am very suspicious of the FDR Data as the cvs file, the animation, and the raw data do not agree according to the amateur experts. They all seem to be different and that doesn't make sense, but it does not indicate an InSiDe JoOb.

As I have understood the discussion so far, increasing the rate of descent results in G values < 1 and decreasing the rate of descent results in G values > 1. If there was a constant rate of descent wouldn't the G value be 1? Shouldn't the altitude data show this?

Maybe Beachnut could post a graph with the altitude (or descent rate) superimposed on the G data. That would give us a better ideas of what was happening. Pretty please?

 

[Myriad]

If the pft loons have extracted the altitude data correctly (there is no guarantee they have) then there should have been a pretty good descent rate followed by the G's Ryan calculated in one of the stated cases. We don't see that at all, so that is the best indicator of missing data. I'd say he was just beginning his final descent toward the light poles as the data ends.

It could also indicate that the plane did not fly over the VDOT tower.

Respectfully,
Myriad

 

[Myriad]

johndoex:
By the way, i see many JREFers touting they were the influence for pointing out our errors. That is also wrong. Actually, one of our own core members pointed it out initially. JREFers of course spent the subsequent days, 3 threads (one being removed and one having to be locked due to JREF typical behavior) and a good amount of their free time behind their screens trying to prove us wrong. Once they found the same mistake, they claim "victory". There are other errors they didnt even catch, including their own.

http://www.abovetopsecret.com/forum/thread341556/pg4


Huh. I reported three errors: miscalculating the initial upward acceleration by multiplying feet per second by elapsed time instead of dividing (causing a 69% overestimate), miscalculating the distance traversed by an object decelerating to zero velocity (causing a 100% overestimate), and scaling a total G force that included the 1G for earth's gravity (causing a +2.8 G error). Are they saying there were more? (And they're proud of that?)

Respectfully,
Myriad

 

[jaydeehess]

http://www.abovetopsecret.com/forum/thread341556/pg4

,johndoex:
By the way, i see many JREFers touting they were the influence for pointing out our errors. That is also wrong. Actually, one of our own core members pointed it out initially. JREFers of course spent the subsequent days, 3 threads (one being removed and one having to be locked due to JREF typical behavior) and a good amount of their free time behind their screens trying to prove us wrong. Once they found the same mistake, they claim "victory". There are other errors they didnt even catch, including their own.

First of all, if one of their 'core members' pointed out the errors then it would seem to have been prudent to take the page down asap. That they did not do. The 3 days spent here pointing out the errors then occured while p4t still had the page up and by inference, still were touting it as correct. If it was taken down because they , on their own, found that they were in error then that is all well and good. However, the fact remains that only after the fact that Myriad and Ryan were publically pointing out the errors did the retraction get put up.

Oddly enough TC was here argueing vociferously that jdx's page of calculations were indeed correct during this time period. It would seem that part of "JREF typical behavior" is not allowing minions of p4t to push erroneous calculations as 'truth'. So it is quite clear that at least he was unaware of any p4t recalculation due to a 'core member's' alert.

Then we also have Terral posting in this very thread on March 17th. However he also says nothing about any recognition that the p4t number crunching was in error. Indeed he says absolutly nothing about any calculations, thus attempting to derail this thread from those calculations and having his post moved to AAH.

Are TC and Terral 'core members' of p4t? If not then obviously few at p4t were informed of the concerns that the numbers were not correct. If they were 'core members' and aware of the bad math what would that say of the motivations of p4t?

I would not hold my breath waiting for p4t to redo the calculations. It is patently obvious that no calculations will show that the plane could not perform the manouvers attributed to it even if such manouvering takes it directly over the VDOT tower. This would in no way bolster any arguement that p4t would want to make and thus they will not bother to post any recalculations.

 

[jaydeehess]

IMHO, you're asking for too much speculation on the precise flight path. We don't know that.

Those spikes in the graph posted by Beachnut could possibly be the roll in and out of turns, but that would be sheer speculation. The two main spikes are either too far or too close to be a roll-ups to avoid the tower as indicated by the VDOT folks.

I don't think we know enough about the precise (and it does need to be precise) flight path to even attempt using the G data for any calculations.

The only thing that G graph shows is that there is missing data. Notice there is no trend toward a continuous descent as there should have been except at the very end. Well, even that is speculation as the G indications would depend entirely on how smoothly the pilot made the pitch changes.

If the pft loons have extracted the altitude data correctly (there is no guarantee they have) then there should have been a pretty good descent rate followed by the G's Ryan calculated in one of the stated cases. We don't see that at all, so that is the best indicator of missing data. I'd say he was just beginning his final descent toward the light poles as the data ends.

I am very suspicious of the FDR Data as the cvs file, the animation, and the raw data do not agree according to the amateur experts. They all seem to be different and that doesn't make sense, but it does not indicate an InSiDe JoOb.

Right, I see, I was still looking at the g data as being in a plane that was only moving in two dimensions (horizontal along the line of the fuselage and vertical).

I also see that it would be difficult to match the position over the Earth to the FDR data with enough precision to plot a precise flight path in 3 dimensions and referenced precisely to a map.

So it comes down to only the last few thousand feet along the flight path and the lamp post damage that are still the most accurate indication of the flight path of the aircraft.

 

[Reheat]

Right, I see, I was still looking at the g data as being in a plane that was only moving in two dimensions (horizontal along the line of the fuselage and vertical).

I also see that it would be difficult to match the position over the Earth to the FDR data with enough precision to plot a precise flight path in 3 dimensions and referenced precisely to a map.

So it comes down to only the last few thousand feet along the flight path and the lamp post damage that are still the most accurate indication of the flight path of the aircraft.

Yes, I think you've got it. If you'll remember the prevalent opinion in the FDR threads here at JREF was/is that none of the data we now have is precise/reliable enough to reach provable conclusions. There are simply too many variables to even try. Using the G data to attempt to prove anything would be even more imprecise than what there is now. There are simply too many variables, which I tried to indicate in the previous post.

The three FDR files (csv, animation, raw data) do not agree, yet they (pft) try to combine the three to imply the aircraft was too high to hit the poles or that it was north of the Citgo Station. They use their rendition of the raw data to obtain altitude and the csv file for DME even tho' the two files indicate different positions geographically. The INS positional data is over 3000' off as admitted by everyone, so it's no good. That is why the DME position is now crucial to them. Why is the DME not in the raw data? A problem with the FDR, maybe? Right now the DME is crucial to their delusional position, but as we all know DME is not precise enough to use it as they are attempting to do. There could easily be a 600+ feet variable in that DME readout and that's precisely why JDX used the shorter 6000' for measuring the 1.5 DME rather than the correct 6076.11549 feet. DME is simply not precise enough, nor can it be correlated precisely with the altitude data.

Based upon what we have now, the FDR data is never going to conclusively prove anything. The physical evidence is the trump card as it always is. This latest foray into the obstacle analysis backfired on them when JDX miscalculated using twoofer math.

At this point, we best let them flounder with the math and the spin of revising their obstacle article. Remember, they have yet to realistically address the physical evidence in any substantial way and won't because that destroys their fantasy.

 

[uk_dave]

So johndoex is a lying waste of space who is happy to sacrifice a devotee such as LC with a half baked premise so long as a few people buy the crap.

What's new?

 

[jaydeehess]

So johndoex is a lying waste of space who is happy to sacrifice a devotee such as LC with a half baked premise so long as a few people buy the crap.

What's new?

Stay tuned, in about a month there will be a truth mover here saying that the plane would have experienced g forces that would tear it apart if it had flown over the VDOT tower and into the Pentagon and that the calculations, an 'da fisiks proofs it.'