1. SpaceCowboy

    SpaceCowboy Rob Balsamo of P4T Banned

    My point is that the above VG diagram is a direct image from the Illustrated Guide To Aerodynamics. I have made this point over and over again when people like "Weedwhacker" and "TWCobra" claim I made up my own VG diagram. But the fact remains, Vd is the end of the flight envelope and the start of the structural failure zone as determined by wind tunnel and flight testing... and as depicted in the above VG Diagram.

    This is why they have avoided the question.

    So, Mick, it is up to you who you wish to support. Objective and real world analysis... or some guys who dodge and weave when presented with the facts.
    • Disagree Disagree x 2
  2. TWCobra

    TWCobra Senior Member

    Robert, this is the claim I made. It relates to a specific part of your video.
    That is what was being debunked. Address that claim please without ignoring the evidence i.e that the NTSB report specifically says that there is no evidence to suggest structural failure before the FDR's lost power, a regime where VD+23 was recorded. When you address this I will get on to other things. Until you acknowledge the error there is no point engaging with you.
    • Agree Agree x 3
  3. SpaceCowboy

    SpaceCowboy Rob Balsamo of P4T Banned

    Yes, and I already discussed this with you.And it is clear why you have refused to take this discussion to me directly....

    We will now take this step by step since it is clear you missed it the last many times we have discussed this on YT and via email....

    The NTSB states "Peak Speed" in their report... yes or no? What do they claim as "Peak Speed"?
    • Disagree Disagree x 2
  4. WeedWhacker

    WeedWhacker Senior Member

    I have not "avoided" any questions. And to the best of my recollection, neither has 'TWCobra'.

    However, I specifically DID ask a question, about the video titled "Flutter at a Glance" (on page 2) and did not yet receive a meaningful response.

    Again, twofold: RE: the video that 'SpaceCowboy' posted, there were scenes of wind tunnel airframe testing, but there were no annotation nor specific details as the relevance of those video clips.

    Secondly, RE: a VG Diagram, I also asked the poster about the term (in the Diagram) 'Structural Damage' (where labelled), and if the poster was willing to assert that those areas of the aerodynamic envelope result in an immediate and full structural failure of any airplane, in every instance, and in every situation it may encounter?

    If the poster's answer is "Yes", then is this the assertion of P4T as well?
    • Agree Agree x 2
  5. SpaceCowboy

    SpaceCowboy Rob Balsamo of P4T Banned

    The NASA Flutter Video is well known among real pilots. Especially those who understand the history of aviation... It is even written down here on AOPA.

    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.

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  6. TWCobra

    TWCobra Senior Member

    Robert, peak speed as referred to by the NTSB seems to be where it hit M0.99 at 22500.

    Nowhere in the report however are they concerned with EAS or its relationship to Vd as you, and I are. What was the peak EAS recorded?
    • Agree Agree x 2
  7. WeedWhacker

    WeedWhacker Senior Member

    The attempt at impolite insult aside, now you freely admit that the "NASA Flutter Video" refers to the "history" of aviation, and is therefore illustrating the concepts learned decades ago. And those lessons have been applied since to our current, more modern aircraft designs, and as such, is no longer a concern.

    Yes, that is true...I am well aware of this history and the development of aviation, as it is of particular interest to me. Along with other aspects of aerospace design and development.
    • Agree Agree x 1
  8. SpaceCowboy

    SpaceCowboy Rob Balsamo of P4T Banned

    Just for you "TWCobra".


    Let me know if you feel any of the above is inaccurate and/or needs modification.
    • Disagree Disagree x 2
  9. SpaceCowboy

    SpaceCowboy Rob Balsamo of P4T Banned

    It's not an insult. It is fact that Vd is established based on flutter and other control issues. From there, Vc is established based on margin of safety calculation mandated by the FAA (which in turn sets Vmo). You should really check out this video.. .it is pretty accurate with verified Pilots and Flight Instructors... you know them well... because you attack them daily...

    • Disagree Disagree x 2
  10. TWCobra

    TWCobra Senior Member

    Robert, I asked you to acknowledge the error in the video. The inclusion of EA990 "NTSB Peak speed VD+5 loss of control/structural failure" in that diagram, is an outright lie and demonstrates how far you are prepared to go to maintain your financial interest in your DVD sales.

    When you get around to being a "Pilot for truth" instead of a "Pilot for a buck based on lies", I'll address the cherry picking and distortions you indulged in for 75% of the other entries to that graph. Until then, I won't deal with a liar.
    • Agree Agree x 6
  11. cjnewson88

    cjnewson88 Member

    Not just 990.

    You include China Air 006, with loss of control/structural failure, as if to say it was that speed+acceleration were what caused the loss of control and failure, but this is not the case at all. The aircraft lost control, then increased in speed, then pulled the g-forces which caused the structural failure. Most importantly the aircraft survived.

    Same for TWA 841

    Same for Easyjet 737

    Your next misleading part is where you plot the 9/11 aircraft. You say UAL93 was in control? It was pointed towards the ground, inverted. You call that control?

    Where are you sourcing the g-forces pulled by AAL77? According to your graph you're claiming AAL77 pulled over 3 g at over 500 mph. That is absolutely false. It never went above 2.25, and for the most part of the final few seconds sat between 0.5 and 2. We also know from the flight data recorder that up to 4 seconds before impact the aircraft was beginning to flutter. Almost every entry and description on your diagram is false, and you know it.
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  12. TWCobra

    TWCobra Senior Member

    Lol... I had all that written out almost word for word... decided that making the point about the lie was more to the point... thanks CJ.
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    • Funny Funny x 1
  13. George B

    George B Extinct but not forgotten Staff Member

    Well I would like to say you all have lost me. Seems we have professional disagreements on many issues: my ignorance makes me ask?

    1) were the standard aircraft structurally capable of maintaining enough integrity to fly into the Towers and Pentagon?

    2). If not: how did the events occur as we witnessed them on 911?

    3) one cannot say the aircraft were not capable of the events without offering an alternate explanation.

    4) If there are alternative explanations, what is the evidence which supports such speculations?
    • Like Like x 1
  14. Jazzy

    Jazzy Closed Account


    It's wrong because the words "Structural failure" are WRONG. What is meant is "anticipated structural failure".

    Structural failure is anticipated beyond those borders but hasn't been dynamically explored.

    Beyond the line rightward (SPEED) is normally transonic flight instability and flutter, and a small material safety margin of 10% and a plus/minus variability in specified material strength of a small fraction of that.

    Failure due to flutter is itself time-dependent. So you can exceed a limit speed briefly - and more deeply in calm air.

    Temporary excursions rightward on the graph are therefore possible. Indeed, they have happened.

    You need to interpret such graphs with some greater foreknowledge of the history of their creation. Then you'll improve.
    Last edited: Mar 22, 2014
    • Agree Agree x 2
  15. Mick West

    Mick West Administrator Staff Member

    I'd recommend reviewing the OP. The topic of the thread is if the fastest speed observed was possible for a few second, or, as PF9 assert, planes fall apart at a specific point on the graph.

    If you consider only that point, it seems to me that PF9's claim has been quite cleanly debunked, and the protestations to the contrary are largely arguments from false authority, distractions, and unfortunately a large degree of scorn.

    Jazzy described the key issue well - a region labeled "structural failure" does not mean the plane will drop out if the sky the instant you enter that region.

    Does your car instantly explode if you rev it into the red zone of your tachometer?
    • Agree Agree x 2
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  16. WeedWhacker

    WeedWhacker Senior Member

    That is the "question" on the table, here. The infamous VG Diagram being used by one side to claim an answer of "No".

    The crux of the problem with the 'other side' and their argument, vis-a-vis the VG Diagram touted as "proof". The difficulty is, there is no alternative narrative nor explanation being offered.

    Agreed, corollary to #2 above.


    It's interesting to also note several things: Although the transponders of all four airplanes did indeed stop transmitting to SSR (Secondary Surveillance Radar), which ATC uses for identification via discrete and unique codes assigned per flight, the Primary "skin paint" reflections from the airplane structures were recorded from the moment each transponder stopped transmitting, until impact. There is solid evidence gathered from the multiple radar locations' taped data that were within range to have detected those airplanes.

    Furthermore, in the cases of AAL 77 and UAL 93, the DFDRs were recovered intact, and their data readable, further verification to support all Primary radar observations associated with those two flights.

    The evidence is quite compelling, IMHO.
    • Informative Informative x 2
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  17. Pete Tar

    Pete Tar Senior Member

    Being at the edge of the envelope for structural integrity does not make the plane's manoeuvres impossible without catastrophic failure considering they weren't sustained for very long. And perhaps the plane was about to fail at the moment of impact or would have 2 seconds later if it didn't ram into a building?

    How many manoeuvres were performed above the envelope and for how long?
  18. cjnewson88

    cjnewson88 Member

    UAL175 was by far the aircraft which was put under the most stress on 9/11, and we know UAL175 was the aircraft which hit the South Tower. Therefore it's very simple to conclude the B767 air frame is indeed capable of excessive loads/speeds for a short period of time. Ergo, Robert is wrong instantly.
    • Agree Agree x 2
  19. BlindIdiots

    BlindIdiots Member

    All three of those aircraft only survived because they had to slow down to regain control due to speeds that caused structural failure, the aircraft on 9/11 did not slow down, and continued flying at speeds that far exceeded the flight envelope which would have caused structural failure.

    This image is of data taken from the csv files of UA 93 downloadable here :http://pilotsfor911truth.org/forum/index.php?showtopic=6205

    The numbers on the left is the Vertical Acceleration of the aircraft in G's, the numbers on the right is time in EDT

    Quoting Rob Balsamo

    If you doubt my image, then simply download the CSV file and view this fact for yourself.

    Whether it was in control or not is irrelevant, the fact is that the airplane should have broken apart at these speeds.

    Actually, the G estimate is low for "AA77"...
    View this video

    The placement on the VG should be much much higher... basically off the graph.

    "We also know from the flight data recorder that up to 4 seconds before impact the aircraft was beginning to flutter"
    False, you heard that from some guy on the internet,who goes by the name Warren Stutt, and has been thoroughly debunked here:

    False, several diagrams here from several sources use the term Structural Failure

    This one here (from www.faatest.com/) has a "caution range" while the part past the black line is the structural failure zone. Therefore the only place the "safety margin" you describe could only come before the Structural failure zone, not in it

    Notice that it says "structural failure"not "anticipated structural failure"

    Another diagram depicting the same thing (from www.aero-mechanic.com/)

    Once again, the caution range comes before the "structual failure zone"

    Another one (from http://apstraining.com/)

    And this one, directly from the FAA, though there is no structual failure text present, it can be observed that it is the end of the flight envelope.

    Once again, vd is the end of the flight envelope, the maximum amount of stress an aircraft can endure. Beyond this causes structural failure, period.
    To sum it up, There is no documentation of the "structural failure zone" having a safety margin, such a margin would only come before the structural failure zone, there is also no proof of any graph being labeled "anticipated structural failure".

    The flights Air China 006, TWA 841, EgyptAir 990 and Easyjet 737 all experienced speeds past this zone, sometimes only a few Vd's past it and suffered structural failure, period.

    "Beyond the line rightward (SPEED) is normally transonic flight"

    You once again offer no sources for this claim.

    "Temporary excursions rightward on the graph are therefore possible. Indeed, they have happened."

    Only briefly.

    Quoting Rob Balsamo:

    False, Jazzy provided no sources for his claims, the fact is that the planes on 911 were well in the zone where they should have experienced flutter, and then structural damage.
    • Disagree Disagree x 2
  20. WeedWhacker

    WeedWhacker Senior Member

    More of the same, and still incorrect. Now, please: How would you respond to this, below?:

  21. jaydeehess

    jaydeehess Senior Member

    "UA93" was in fact pulling upwards of 4 G's (according to the FDR data) at high speed when the "hijackers" were allegedly trying to throw the passengers off their feet. The airplane did not break and remained in control... all the way into the ground... again, according to the govt story."

    According to the data above it was "upwards" of 4 g for a fraction of a second but PFT seems to imply that it was at this level of stress for quite some time,
    The characterization that it was under control is the most specious statement I have ever read I do believe. It was essentially sent into a death dive.
  22. WeedWhacker

    WeedWhacker Senior Member

    It should also be noted here....UAL 93 at the time of the attempt to delay the passengers who were trying to break through the Flight Deck door, the airspeed was only about 290 - 295 knots. (A/T appeared to be controlling speed). This video, starting at 1:18:00 --

    Starting at 1:20:45, the throttles were pushed to their full forward stops, and airspeed increased near Vmo. There were some abrupt pitch movements with speed between 320-345 knots. The airplane was only minutes from ground impact, however.

    From the NTSB, a graphic:

    UAL 93.
    Last edited: Mar 22, 2014
    • Informative Informative x 1
  23. Jazzy

    Jazzy Closed Account

    The structural failure zone is as I described. It is a zone never voluntarily entered by a test pilot, so exactly when the predicted consequences occur is NOT KNOWN because it cannot be statically simulated in a laboratory, and will only occur in flight.

    It has already been shown that the tower planes were at around 80% of their structural failure speed, the Pentagon plane at 65% of that speed. That is nowhere near the zone, so you are uttering terminological inexactitudes.

    And you are also conflating when you include Flight 93. The G-versus-time plot shows a plane fluttering in a near-vertical dive, accelerating to its terminal velocity. Out of control. It had definitely passed beyond that boundary. But it was the only one that had.

    You are engaging in polemics instead of properly concerning yourself with present-day practical aeronautical engineering. And, incidentally, the truth.
    • Agree Agree x 2
  24. JRBids

    JRBids Senior Member

    Which means? What? It did not hit the tower? We all know it did. We saw it.
    • Agree Agree x 2
  25. Pete Tar

    Pete Tar Senior Member

    Okay let's assume this is true for a second - it didn't break apart. Therefore, at what point in the various planes service history was the super secret work done that would allow these planes to apparently do the impossible?

    That is an event in time that will have left traces.
    • Agree Agree x 3
  26. BlindIdiots

    BlindIdiots Member

    Show how it is incorrect then.

    I do not see how this relates to the discussion, which refers to the speeds of the 9/11 aircraft, not whether they were present or not, I don't deny that they were there.

    Please note that the serial numbers of the DFDRs were never released in any of the reports, and the FBI says it has no record of them, therefore they are not verifiable as coming from those flights.
    However, this once again has nothing to do with the topic, which again regards the speeds of the aircraft on 9/11.

    Take a look at the image again, notice how UA 93 went from 4G's to negative G's in just a second, this occurs several times in its flight.


    Graph of G loading experienced by UA 93 versus EA 990
    Know that "the oscillations exceeding both positive and negative G load limits of the airframe at high speeds are more dangerous than gradual increasing of G loading"

    The "UA93" G loads you see plotted here were prior to the alleged inverted dive.

    It is seen here that the sudden oscillations have occurred several times the flight of UA 93, yet it remained completely stable and in control despite experiencing G's way beyond the capabilities of a 757.

    Correct, the zone is not entered because according to various precedent's structural failure will occur at those speeds. Speeds that are sometimes only a bit beyond that zone.

    Where is it proven that the planes speeds that were only 80 and 75 percent past their structural failure speeds?

    How am I conflagrating? I am showing once again that the aircraft has gone way past its design limits, and how is it the only plane that had done that?

    How dare you, I have not insulted you at all in my post. Unless you take offense to the fact that you have provided no sources for your claims, and have continued to do so.

    Claims such as this
    "Beyond the line rightward (SPEED) is normally transonic flight"

    And you also have not addressed my images from various sources which prove that there is no fault in using the terminology "Structural Failure".
  27. Svartbjørn

    Svartbjørn Senior Member

    Question: How long were the planes "at these speeds?"
  28. WeedWhacker

    WeedWhacker Senior Member

    Good to hear that you do not deny that they were there. My points relate directly since, now that we've agreed that they were there, this means that they were observed. When something is observed, it can be measured.

    There are numerous ways, and tools to use, in order to measure something's characteristics.

    This thread proves that claims made in a particular video are bunk.
  29. BlindIdiots

    BlindIdiots Member

    Maybe I did not make myself clear enough, what I mean't is that I don't deny the aircraft that hit their targets were present on 9/11. Though it is arguable whether they were in fact UA 93, 175 and AA 77.

    In other words, I ain't a no-planer


    Sorry WeedWhacker, it appears we are not in agreement with one other, though that does not prevent us from being respectful of one other in our arguments, right?
  30. NoParty

    NoParty Senior Member

    Well. I'm glad to see you assert that position.
    Just yesterday there was some jerk--I think his name was Maurice--
    who took the complete opposite approach. Glad you're nothing like him!
    • Funny Funny x 2
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  31. cjnewson88

    cjnewson88 Member

    Nope, there is no argument. They figured what aircraft crashed within minutes of that day. It's taken you 12 years and you still can't figure it out. What is wrong with you?

    Radar, debris, DNA, records, ATC recordings, airphone and cellphone calls, and more, show those aircraft crashed on 9/11. That is a long established fact. Anything you try to say otherwise makes you instantly wrong.
    • Agree Agree x 1
  32. BlindIdiots

    BlindIdiots Member

    This is just an insult

    Stay on topic, I could argue this in another thread that refers to the other evidence if I wanted to. But once again, this thread only discusses the speeds of the aircraft on 9/11.
  33. Pete Tar

    Pete Tar Senior Member

    Though not apparently in our choice of user name hey @BlindIdiots?

    (though of course I endorse the sentiment, unfortunate irony aside)
    Last edited: Mar 22, 2014
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  34. TWCobra

    TWCobra Senior Member

    No, this thread discusses a video put out by Pilots for truth which claimed that EA990 broke up at Vd+5, a claim debunked comprehensively.

    So Blindidiots, do you agree that the specific claim addressed in the OP is correct?
    • Agree Agree x 2
  35. Svartbjørn

    Svartbjørn Senior Member

    Which still hasnt been answered completely yet... How long were the planes at those speeds?
    • Agree Agree x 1
  36. Jazzy

    Jazzy Closed Account

    A point of agreement.

    Nowhere. No-one has said "80 and 75 percent past their structural failure speeds". Only you.

    I'm talking about the approach speeds of the aircraft that weren't in a terminal velocity dive. Namely 460, 510, and 565 mph. They were at only 65%, 72% and 80% of their structural failure speeds.

    Now that's a question I cannot answer.

    How you are conflating - I can. You are mixing three aircraft traveling horizontally at speeds above their Vne with a fourth in a terminal velocity dive. That's conflation.

    Reread my previous answer.

    You have in your previous posts, and you do so with your name in your new sock-puppet. There is no special "source" for my data. It's common knowledge. You have already found it and ignored it.

    That's the way they are engineered in the design stage, because they are expected to cruise at high speed and high altitude. I have already described this.

    I have already explained to you that it's your interpretation of the structural failure zone boundary that is at fault. It's up to you to understand this properly.

    All four aircraft were designs by Boeing, who use an airframe design which begins to exhibit trans-sonic flutter instability at Mach 0.93. That's 707 mph at sea level. That's what they work to.

    You will appreciate that three of the four aircraft were significantly slower than that by the percentages I have indicated. The fourth wasn't.

    Last edited: Mar 23, 2014
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  37. Pete Tar

    Pete Tar Senior Member

    • Funny Funny x 5
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  38. WeedWhacker

    WeedWhacker Senior Member

    That isn't really the topic, here. (Although I remain puzzled by that rash assertion, based on the hordes of other evidence to the contrary that corroborate the identities of all four airplanes involved).

    Your post #99 was a gish gallop of the sort commonplace from the site where you likely obtained it. I can only surmise that you found this thread due to the title, since it mentions the site (I'll just abbreviate, it's easier - P4T).

    I will also surmise that you were "impressed" by the "arguments" and claims in the video ("SKYGATE 911..."), and by other material put out by P4T? Is this a correct guess on my part?

    If this is the "opening position" that you hold, then we have a long way to go in de-mystifying the gross errors that are a hallmark of P4T, in my several years of dealing with them. This latest video (subject of thread) is no exception. Unfortunately, since there is so much ground to cover, addressing all of the other P4T fallacies will be outside the scope of this thread. However, I'd suggest as a baseline approach to this specific topic, re-reading the OP, post #1.
    • Agree Agree x 1
  39. BlindIdiots

    BlindIdiots Member

    Actually, you did in fact say that, I was referring to this sentence of you post referring to the tower planes and the pentagon, unless you think I mean't to deceive you by saying "past" rather than "of".

    Your statement is in direct conflict with Boeing, all of the recorded speeds of those aircraft are beyond the documented speed of 410-420 knots at which structural failure occurs. You still have not proven that they were "at only 65%, 72% and 80% of their structural failure speeds".

    I was showing how the aircraft experienced stress way past the limit they are designed for. And the fact is that the aircraft were traveling in the structural failure zone.

    Saying "common knowledge" is no excuse for a source, the fact remains that you still have not provided a single one. I cannot ignore something that does not exist. And no, I am not Rob Balsamo.

    NTSB concludes 510 knots and 430 knots at impact for United 175 and American 11 and 565 knots for AA 77. The max operating speed for a 767 is 360 knots, while the vd is 420 knots at sea level, beyond those speeds causes flutter and then failure, this is shown from various precedents.

    Where did you get the figure "707 mph at sea level" from? That is 614 knots, way past Boeing's documented VD speed.

    You are ignoring low altitude limitations and assuming high altitude limitations apply to all altitudes

    From the Boeing 767 Type Certificate Data Sheet


    As you can see, the VD at sea level is in fact 420 KCAS. Past this zone causes flutter leading to structural failure, period.

    Each object has it's own flutter resonance and is not dependent exclusively on Mach .It is based on dynamic pressure, which is why manufacturers set two limitations based on wind tunnel and flight testing... one for low altitude, and one for higher altitudes. High Mach number is much more dangerous at low altitude than at high altitude due to high dynamic pressure at low altitudes.

    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 develop which put the aircraft structural integrity at stake.

    Wrong, it is your interpretation of it that is at fault. I have already shown you several VG diagrams with the Structural Failure zone defined as such. You were claiming that it should say "anticipated structural failure" even though various sources on aviation disagree with this statement. You are also claiming that there is some sort of safety margin beyond the flight envelope, when there is no documentation for that statement as well.

    For AA 77, refer to this article http://www.historycommons.org/timeline.jsp?timeline=complete_911_timeline&day_of_9/11=aa77

    And this


    And this

    You may verify the sources if you wish. But this shows that the aircraft was already well beyond its structural limits when it was 12 and 14 miles away from the Pentagon, and then accelerated to a speed of 565 knots on impact.

    For UA 175 and AA 11 , I recommend you read the following


    Note this part of the study


    Notice that from 8:55 from 9:05 the NTSB states here that the aircraft speed was 500-520 knots.


    And also see this


    WeedWhacker, I have seen that many of your arguments against the claims of P4T have all been rebutted on the forum, which you are invited to come to for debate.

    You also have yet to respond to the "gish gallop" I have posted with a point by point rebuttal.

    I will address the OP in a bit, though others are attempting to argue with me here, which Is why I am doing the same.
  40. Landru

    Landru Moderator Staff Member

    Because gish gallops are against the posting policy here at Metabunk. You should read it.
    • Agree Agree x 1