Debunked: Pilots for 9/11 truth WTC speeds

[Mick West]

I was trying to see if anybody's paying attention

What you should do is take all the corrections, and reformulate your question.

Really what you need to know is A) how much thrust is needed to maintain that speed at sea level, and B) how much thrust do the engines give at full power.

 

[Chew]

If you can't get the simplest physics of gases right then you aren't going to be able to get the physics of a dive right. You think it couldn't get to that speed, great. Show us your math.

 

[Totaro17]

If you can't get the simplest physics of gases right then you aren't going to be able to get the physics of a dive right. You think it couldn't get to that speed, great. Show us your math.

I understand air density fine. My questions has been avoided. And only mistakes are pointed out. We are talking about level flight at sea level not a dive. It's Not about what I think or my math.

I am asking you guys a question. And I and I feel it's avoided.
Mick can you help answer question I have personally been told that UA175 can't go that fast near level flight at sea level. And this

And this
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." - Source -http://theflyingengineer.com/tag/

 

[Totaro17]

What you should do is take all the corrections, and reformulate your question.

Really what you need to know is A) how much thrust is needed to maintain that speed at sea level, and B) how much thrust do the engines give at full power.

Mick can you help answer the question. I have personally been told that UA175 can't go that fast near level flight at sea level. And this


And this
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." - Source -http://theflyingengineer.com/tag/

 

[jaydeehess]

And this
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." - Source -http://theflyingengineer.com/tag/

"Must not" and "cannot" are two different things. It is odd that PfT would conflate the two.

Furthermore this ignores the research indicating that aircraft must pass a Vd plus 15% factor. Research that involves statements in technical descriptions of aircraft requirements rather than articles in flying magazines.
Did you read the comments to the Airbus article you reference? In it one pilot admits never having heard of dive speed max.
In addition, another comments states

Just to add my two cents, on the A320 structural disintegration due to over-stressing needn't necessarily occur right above VD/MD (especially at non-enveloping g's); the concern rather is about buffeting or flutter above the design dive speed (the buffet on the A380 video is pretty scary!).

One of the easiest ways to over-stress the airframe, oddly, isn't at such high speeds; rather it's at the VC/MC knee point at a pull-up of greater than the certified 2.5g with heavy payload and not much fuel in the wings to relieve the upward bending.

For that, you'd have to be unlucky enough to be close to your MZFW, with the aircraft in alternate law, and facing the need to pull-up that hard, though – thank goodness that's hardly likely!

 

[jaydeehess]

If PfT is making the claim, or for that matter if anyone is making the claim, that a 767 cannot produce enough thrust in a low angle dive, to achieve the velocities that UA175 did, then it is up to them making said claim to do the math to prove it/ it is not encumbant upon others to prove the claim wrong.

 

[Totaro17]

"Must not" and "cannot" are two different things. It is odd that PfT would conflate the two.

Where did they do this. I am not affiliated with P4T. But I am more concerned with the statement -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.

 

[WeedWhacker]

I am not a pilot, but I have 2 high school friends that are. I keep in touch with them and they have agreed with a lot of p4t and disagree with on some.

You are not a pilot, yet are trying to understand a level of aviation expertise far beyond what a layperson usually will fully grasp, and also since you say you have high school friends that are roughly same age category as you? They may indeed have pilot certificates, but certainly the knowledge and understanding needed to know the reality of high-speed flight in a modern airliner is well beyond their current level of experience.

To hear that they "agree" with P4T on any issue that spews forth from that organization is rather disheartening to me. (Unless it is to agree with P4T on the non-existence of "chem"trails? But, a different topic and about the only thing P4T gets correct.

I'd invite them to PM me, if they wished. I have about 20,000 hours total time, with type ratings on the B757/767, and the B737 and MD80 as well. With other experience on various types during my career at an airline.

But what they have a big problem with is the ability of the engines to have enough thrust to Propell the plane ( at near level flight) as you say and we see,a slight decent. They have said to me- that kind of speed is impossible at sea level The engines were not designed to produce enough thrust in that dense of air and it's was a warm day making the air more dense and wet(humid).

No, the air was not particularly "warm" nor humid on that day. But, that is irrelevant. The airspeed was achieved because of GRAVITY assisting in the acceleration of the jet. Having flown that type of airplane, I can attest to how quickly airspeed can build up in even a shallow descent. You pilot friends should certainly understand this basic principle.

 

[Totaro17]

research indicating that aircraft must pass a Vd plus 15% factor

This would be cruising altitudes? Not at sea level? I just want the question answered -can a 767 commercial aircraft engines produce enough thrust to reach 510 knots at sea level near level flight.

 

[Landru]

This would be cruising altitudes? Not at sea level? I just want the question answered -can a 767 commercial aircraft engines produce enough thrust to reach 510 knots at sea level near level flight.

As Weedwhacker mentioned, yes. They were only level at the tailend of approach. They had been descending right up until they struck their targets.

 

[WeedWhacker]

As Weedwhacker mentioned, yes. They were only level at the tailend of approach. They had been descending right up until they struck their targets.

This is a correct statement. It is corroborated by the visual sighting by air traffic controllers in (at least) the Newark control tower. It is also recorded by several video cameras that were aimed at the WTC Towers because of the previous AAL11 impact and subsequent fires.

 

[Totaro17]

As Weedwhacker mentioned, yes. They were only level at the tailend of approach. They had been descending right up until they struck their targets.

I am just trying to understand pilot for 9/11 truth claims. The video that says "pilots say no way" the phone calls to Aeronautical engineers is my biggest question when they say that the engine can't do that. I've seen a couple more videos where they actually talk to Boeing and she laughs and say no as well.

 

[Landru]

I am just trying to understand pilot for 9/11 truth claims. The video that says "pilots say no way" the phone calls to Aeronautical engineers is my biggest question when they say that the engine can't do that. I've seen a couple more videos where they actually talk to Boeing and she laughs and say no as well.

Perhaps you should question P4T then.

 

[WeedWhacker]

Mick can you help answer the question. I have personally been told that UA175 can't go that fast near level flight at sea level. And this


And this
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." - Source -http://theflyingengineer.com/tag/

I have addressed that video countless times over the last several years.

That video clip features retired airline pilot Russ Wittenburg speaking. His usage of the word "alleged" when referring to UAL 93 and UAL 175 is appalling, to me. Just disrespectful to the families and friends of the victims. he should be ashamed, because some of those victims were former colleagues of his!

At 0:27 he sets up a "strawman" argument, using the FALSE assertion that the hijackers trained in only a Cssna 172. They had simulator training in an airline-type training environment, enough at least to have had some familiarity with the handling characteristics of a large airliner.

AT 0:41 he says "...make high speed, high banked turns...". Continuing on with the outrageous (and, for an experienced airline pilot to make this claim is astonishing) of "...5, 6, 7 Gs...". Again, either he was woefully misinformed when he made that video, or was willfully lying. I can only speculate as to why and whether he has some agenda that is hidden.

At NO time on either of the two recovered FDRs was the bank angle "excessive" ("excessive" in this context means over 45° angle of bank).

And the claim of 5-7 Gs is simply ridiculous.

Oh, and FYI....as far as I know, that YT clip is from a video produced by--- you guessed it!!!! P4T!

 

[jaydeehess]

Where did they do this. I am not affiliated with P4T. But I am more concerned with the statement -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.

They do it often. In fact Rob Balsamo has stated that no pilot he trains would ever take an aircraft outside the published Vmo. When informed that a suicidal pilot does not care about the no-nos of published parameters he shuts up.

In the article quoted the engineer author starts off saying that Vd is a must not speed, then proceeds to state something he does not back up with calculations. His statement may well be true. If so, and if PfT wishes to use it, then they gotta illustrate it. is. they need to do the math.
http://en.m.wikipedia.org/wiki/Parasitic_drag they or anyone else could start here.

We can probably ignore induced drag as it is lessened at higher velocity.

 

[WeedWhacker]

The video that says "pilots say no way" the phone calls to Aeronautical engineers is my biggest question

Because it was the context OF the question posed by the caller. It was 'bait' and the point of the answers from the engineers was in level flight with the available thrust of the typical B767 engines it is not possible. This is true.

The quotes (audio quotes) of those engineers are "cherry picked" therefore...in order to give the audience a false impression.

 

[Totaro17]

They were in a very shallow decent, not a dive. So how can they reach must less exceed VD by 90knt. Some said by gravity. I can't just take your word for it show me something that proves one way or another that this can be achieved with a normal united airlines 767/200 and it's normal engines

 

[jaydeehess]

They were in a very shallow decent, not a dive. So how can they reach must less exceed VD by 90knt. Some said by gravity. I can't just take your word for it show me something that proves one way or another that this can be achieved with a normal united airlines 767/200 and it's normal engines

Since you are accepting the word of PfT then perhaps you should ask them how they determined their claim. By quoting magazine articles?

 

[WeedWhacker]

They were in a very shallow decent, not a dive. So how can they reach must less exceed VD by 90knt. Some said by gravity. I can't just take your word for it show me something that proves one way or another that this can be achieved with a normal united airlines 767/200 and it's normal engines

I think that you are not familiar and/or have a misconception of the terms "descent" and "dive". I am wondering what you envision with the word "dive"? IOW, what angle relative to the horizon do you consider a point where an airplane is in a "dive"?

Now....as I alluded to earlier, I have actual experience on that type airplane. I can tell you absolutely that even with the engines in flight idle, a descent can increase the airspeed right up to VMo. In fact, this is a situation they YOU as a passenger might have been onboard when it occurred. There is no need for any excessive nose down pitch angle. (You'd notice anything greater that 5° usually...and this is not atypical).

Since the speed can accelerate to the "barber pole" so easily with NO thrust, now consider what can be achieved with FULL thrust, and a bit more aggressive nose-down pitch attitude.

Watch this short video, increase to full size if you can (I wish it had sharper video quality):


This is a B767 crew conducting the OverSpeed Warning test. Note the very shallow nose-down angle.

Also pay attention as the Captain reduces thrust, and levels to allow the airplane to decelerate as soon as they reach VMo. Note also another action he performs: He raises the Speed Brakes. When you fly as a passenger and can see the top of the wing, you will often see these in action. They add drag, and help (slightly, they really aren't that effective in usage) to curb airspeed excesses.

 

[Totaro17]

from the engineers was in level flight with the available thrust of the typical B767 engines it is not possible. This is true.

If That's true, then you are saying that a shallow decent at sea level it would be able to have the available thrust?

 

[Totaro17]

Since you are accepting the word of PfT then perhaps you should ask them how they determined their claim. By quoting magazine articles?

I have not said I accept what they said I am trying to understand what they're saying and I am on thier form ask the same questions

 

[Mick West]

If That's true, then you are saying that a shallow decent at sea level it would be able to have the available thrust?

That's certainly what appeared to happen. The very fact that we all saw it happen seems adequate evidence that it's possible, in the absence of contrary evidence. The claimant needs to bring the evidence here.

 

[Pete Tar]

show me something that proves one way or another that this can be achieved with a normal united airlines 767/200 and it's normal engines

Well unless you believe the plane that crashed into the tower wasn't a 767-200 or the airspeed records are wrong, obviously it can.

 

[WeedWhacker]

If That's true, then you are saying that a shallow decent at sea level it would be able to have the available thrust?

Yes, you got it!

A "powered descent" as it is called allows airspeed to increase VERY rapidly....if allowed to. (whether by pilot error, or intentional suicidal hijacker terrorists).

Again, as a passenger, you will notice (if paying attention) a variety of techniques used in normal airline operations during a descent. Sometimes if it's just a minor altitude change (a few thousand feet) the thrust will be reduced, but not all the way to idle. A combination of the thrust setting, and the pitch attitude (nose relative to the horizon, or "ground") maintains the desired airspeed.

The most fuel-efficient descent is one that begins at an optimal distance from the desired level-off point, and done with engines at idle ("Flight Idle"). Again, as a passenger if paying attention, you may become aware of this. With engines at idle, then airspeed is controlled exclusively by pitch attitude.

 

[jaydeehess]

I have to note that one of the audio quotes in the video refers to a 727 that exceeded Mach 1 and recovered. It was in a steep dive. Others quoted made the statement that yes, pointing the aircraft down would change things significantly. Part of the reason for that, IMO, is the reduced requirement to create lift, further reducing induced drag(speed itself lowers induced drag)..
The people on the calls were all responding to a question of level flight.

 

[Pete Tar]

Poaching an informative post from ATS... (assuming details are correct)

bbracken677
link


1. The speed of the aircraft that hit the WTC was officially reported as between 500mph and 560mph ground speed, calculated by the observed point to point distance covered over time.
2. A Boeing 767-200 airframe is rated to .86 of Mach speed (speed of sound) at any altitude before the risk of structural failure. It as the aircraft approaches the speed of sound when the properties extreme high and low pressure areas can have destructive effects on the airframe. This figure is as with all limits set conservatively.
3. The speed of sound at approximate sea level is 761 mph on a standard day. Therefore the theoretical maximum speed the 767-200 can reach intact is, conservatively, .86 x 761mph = 654mph or approximately 100mph above the officially reported speed of AA11 or UA175.
4. The 767-200 is an aircraft that's considered highly powered due to its requirement to function with only one engine for ETOPS - Extended-range Twin-engine Operational Performance Standards. It is capable of taking off fully loaded with only one engine.
5. The 767-200 is considered by pilots and aviation professionals to be a "slick" or "low drag" aircraft, being without bulbous construction and with highly swept 31.5 degree wings. It is well known that it is difficult to keep the 767 aircraft from over-speeding during decent; due to its low drag/high power configuration.

 

[WeedWhacker]

Poaching an informative post from ATS... (assuming details are correct)

They are.

This points out another (thanks for reminding me) of the P4T "red-herrings" in their claims RE: UAL 175....Mach speed.

P4T is careful to NEVER bring up Mach....they (well, he) focuses solely on EAS and the made-up "V/G Diagram" that has been trotted out time and again.

(ETA: The post courtesy of ATS was made by someone who used units of MPH. Which is fine, as long as everyone knows this, and knows how to convert to Knots where appropriate. MPH is usually more "familiar" to the casual audience, hence some people use them. A "Knot" is technically a "Nautical mph"....which leads to confusion, sometimes).

 

[jaydeehess]

What was the descent angle? I have no pen and paper but at a shallow five degree down descent my off the cuff calcs puts the contribution to line of flight force due to gravity at about 20% the straight down force on the aircraft.( or have I misplaced the decimal?)

So contribution to flight line velocity due to descent, lessened induced drag due to lesser requirement to use power for lift and due to increased speed.

 

[Totaro17]

I have not said I accept what they said I am trying to understand what they're saying and I am on thier form ask the same questions.

 

[WeedWhacker]

Interesting. Would need to bring in aeronautical engineers, but I'd speculate that 5° nose-down pitch attitude (relative to the horizon) and as indicated by cockpit instrumentation might not always equate to an actual (if viewed from outside) equivalent angle (relative to the horizon).

TWCobra might be able to help, since he's still flying...modern "glass cockpit" jets include a feature called the FPA, or 'Flight Path Angle' as an indication on the EADI. IF (say) you are showing a 5° nose-down pitch attitude on the EADI (this is the angle of the airplane fuselage relative to the Earth) then the FPA may (or may not) "match up" with it...depends on various factors.

 

[WeedWhacker]

I have not said I accept what they said I am trying to understand what they're saying and I am on thier form ask the same questions.

It will be interesting to see if or when the owner of the site decides to "ban" you, or heavily edit your posts.

I will add that this type of venue (online forum posting) is absolutely the WORST method of learning and understanding something as complex as flying an airplane. One-on-one training, with a variety of educational aids and tools, is a much more efficient and useful way for the student to learn, and for the instructor to impart knowledge.

 

[Pete Tar]

A video of a 757 at 500 knots at ground level. (well it's claimed, but not sure if true).
Is this a fair indication of a 767's ability?

 

[jaydeehess]

What was the descent angle? I have no pen and paper but at a shallow five degree down descent my off the cuff calcs puts the contribution to line of flight force due to gravity at about 20% the straight down force on the aircraft.( or have I misplaced the decimal?)

So contribution to flight line velocity due to descent, lessened induced drag due to lesser requirement to use power for lift and due to increased speed.

Ack, that may be more like 8 percent. However at 160,000kg , one percent of the force due to 'g' would be 15 kilonewtons. Thrust available is between 220 and 280KN so each 1 percent of force due to gravity contribution to line of flight velocity would add the equivalent of about 5% more thrust.
Like I said, no pen and paper available where I sit now and only a very poor calculator on my phone.

 

[Keith Beachy]

Mick can you help answer the question. I have personally been told that UA175 can't go that fast near level flight at sea level. And this


And this
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." - Source -http://theflyingengineer.com/tag/

The flying engineer is a journalist.

At high altitude in my trusty (okay, your ) KC-135, I did not have enough thrust to go faster, or higher within the limits of long term engine use, temperature limits etc. Thus if I was to demonstrate 1.2Vd speed, I would have do it in a dive, or as prescribed by FAA regulations to be certified. But at sea level my trusty under-thrust J-57 quad noise maker of smoke, the typical SAC trained killing machine of fuel, could quickly exceed Vmo as I demonstrated at 300 feet during a fly over for change of command, I thought I would make noise and smoke, the only cool thing a tanker is good for, and keep my trusty jet at or above maneuver speed and avoid crashing etc which showing off can end in.
I only had 44,000 pounds (old engines) of total thrust at 300 feet, and quickly exceed 350 knots, almost overrunning the SR-71, as I pitched up to downwind to slow the jet, after I caught the copilots hands with the throttles slammed to idle as I noticed were were way over Vmo... oops.

Have you flown on a jet lately? They have lots of thrust, what would stop the jet from going real fast is the engines not liking high speed airflow, doubt they could go MACH 1. The airliners that went MACH 1 used g as extra thrust.

In a decent of 6 degrees I could exceed all limits, normal glide path with no engines at 300 knots is 3 degrees, no engines required - free airspeed till earth stops you.

Flight 77 is a good example of speed increase due to thrust and decent. 26 seconds to go from 350 knots to 483.5 knots. The terrorist pilot pushed the throttles to 100 percent.
The terrorist pilot in 77 was going ~300 knots, and then pushed up the throttle to 100 percent, and he exceeded Vmo (like I did) in 10 seconds.

 

[jaydeehess]

Interesting. Would need to bring in aeronautical engineers, but I'd speculate that 5° nose-down pitch attitude (relative to the horizon) and as indicated by cockpit instrumentation might not always equate to an actual (if viewed from outside) equivalent angle (relative to the horizon).

TWCobra might be able to help, since he's still flying...modern "glass cockpit" jets include a feature called the FPA, or 'Flight Path Angle' as an indication on the EADI. IF (say) you are showing a 5° nose-down pitch attitude on the EADI (this is the angle of the airplane fuselage relative to the Earth) then the FPA may (or may not) "match up" with it...depends on various factors.

Like I said, not real sure about my numbers. In fact in a 90degree straight down dive I see that gravity seems to supply 1.55 MegaNewtons of force out performing the engines by a factor of 7. IOW with engines maxed in a straight down dive, were that even possible w/o flameout, the engines are contributing only 1/8th of the total force on the a/c.

 

[WeedWhacker]

A video of a 757 at 500 knots at ground level. (well it's claimed, but not sure if true).

That is a video I have referred to often, over the years, as it soundly (pun) refutes so many claims by the 9/11 "truth movement". I cannot recall a single instance, however, when the owner of P4T ever addressed it. Might have happened, and I missed it.

Unable to verify the actual "500 knots" value of that B757. It was operating at an airshow, and despite being a military-use airplane, is basically "off-the-shelf" as a B757. The B767 shares a commonality, so much so that for pilots it is a "common" type-rating. Minor differences, easy to learn. The B767 engines have more powerful thrust "numbers", though.

Back to "500 knots" in that example? I am certain it was beyond the VMo of 350 knots, but not certain as to how much.(350K for the B757, 360K for the B767....but, keep in mind, that the limit RE: IAS...the "Barber Pole" varies by altitude. But, we can presume this demonstration was well below 20,000 feet MSL!!).

Still, it is a very strong example of the robust nature of the Boeing airliner product (oh, and I'll toss a bone to Airbus too...they are built to the same certification requirements, in terms of airframe structural integrity).

 

[WeedWhacker]

In a decent of 6 degrees I could exceed all limits, normal glide path with no engines at 300 knots is 3 degrees, no engines required - free airspeed till earth stops you.

Sorry, I added an enhancement to the quote above.....because it was SO SPOT ON!!!

 

[jaydeehess]

Sorry, I added an enhancement to the quote above.....because it was SO SPOT ON!!!

Actually Keith's comment makes me a bit more confident in my numbers above.

 

[TWCobra]

I doubt the 757 in that video was exceeding VMO. The RNZAF operates it to airliner standards.

With regards to UA175, the aircraft was in a substantial dive before impact.

I had a couple of VMO exceedences during my time on the aircraft, usually occurring either climbing into a jetstream or descending out of one. The aircraft will exceed VMO easily in those circumstances.

In the days when Australia didn't have a speed limit below 10000 feet, I have vivid memories of entering the circuit at Coolangatta (Gold Coast) at 330 knots plus with idle thrust from a long descent. The aircraft required speed brake to slow down.

The fastest of all the speed analyses from 9/11 puts the aircraft doing around 510 knots at impact, therefore it is up to P4T to prove that isn't possible with a standard jet.

In my experience, it is.

 

[WeedWhacker]

Actually Keith's comment makes me a bit more confident in my numbers above.

Yes, I see what you mean, but in reality UAL 175 certainly did not fly a vector 90° vertical to the earth's surface, so..although a fun math calculation and hypothetical, it really doesn't apply. I am waiting for an answer about what the definition of an airplane in a "dive" is.

90° is of course the extreme. (And unrealistic, except in Bugs Bunny cartoons).