9/11 even real pilots couldn't do it

Originally posted by trebor451

Originally posted by 4nsicphd
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OK Tiff, we have one taker who denies that supersonic compressibility can cause a compressor stall. We can rep

As far as you making the big bucks to sit in the front, care to tell the world what organization you flew for? That way we can repair top the other pilot's lounge and have a good belly laugh at the pilot who claims a compressor stall occurs on a wing.

The first organization I flew for in turbojets (F-4D) was the United States Air Force out of Udorn (Thani) Royal Thai Air Force Base. (555th TFS, Tail Code OY)
And I reread my initial post and nowhere does it refer to a compressor stall on a wing. It talked about a stall in the compressor section of a turbofan. In fact, it went on at great length about fan section diameter. A wing doesn't have a fan section or a diameter. Need a picture of a wing? It gave details of rpm. A wing doesn't have rpm, except a rotary one, and it sure ain't in the neighborhood of 3500 rpm.
I know what it is. You're just mad because I said something uncomplimentary about Rolls Royce, and being English, you took affront. You know, you shouldn't use the same screen name on all online accounts. It makes it easy to trace your rants and screeds and the stuff you peddle on Ebay. Anyway, time for a Carib by the pool.

reply to post by 4nsicphd

FACT: At full power, the tips of the fan blades would be traveling at 4309.5 x 3.14159 x 74.5 inches/minute or 1 008 581 inches per minute or, when added to the forward speed, as reported, would be traveling 1490 mph or about mach 2.0.

The direction the fan blades are turning and the direction the aircraft is traveling are 90 deg to each other.

Please explain how they can be added together.

Originally posted by waypastvne
reply to post by 4nsicphd

 

FACT: At full power, the tips of the fan blades would be traveling at 4309.5 x 3.14159 x 74.5 inches/minute or 1 008 581 inches per minute or, when added to the forward speed, as reported, would be traveling 1490 mph or about mach 2.0.

The direction the fan blades are turning and the direction the aircraft is traveling are 90 deg to each other.

Please explain how they can be added together.

I made a scientific mistake when I said "speed" It is actually velocity, which is a vector. The track of the leading edge of each rotor describes a helix with components of each vector. Vectors are added together by, in effect, putting arrows describing each magnitude and direction nose to tail. But your point is a good one. Jet engines such as the Rolls RB211, or the Trent which replaced it, are designed to operate with the airflow into them at normal speeds. Too slow or too fast and the alpha (AOA) is not what it was designed for. Ever seen (or heard) a jet using reversers to blow back rather than a tug to push back? That very loud and very expensive bang was a compressor stall.

reply to post by TiffanyInLA


IN deference to the solemn remembrance of this date, I have (historically) tried to restrict my postings.

However, this last of yours requires no other response than, HUH?!

What planet/alternate universe are you residing on, and HOW did you manage to make an internet connection to OURS????

Originally posted by 4nsicphd

I know what it is. You're just mad because I said something uncomplimentary about Rolls Royce, and being English, you took affront. You know, you shouldn't use the same screen name on all online accounts. It makes it easy to trace your rants and screeds and the stuff you peddle on Ebay. Anyway, time for a Carib by the pool.

Forgive me for pointing this out, but you are the one who stated:

FACT: Supersonic airflow disrupts airflow over an airfoil, often causing compressor stall.

I won't get into any definitions of what an "airfoil" is, but suffice it to say a wing is most definitely an airfoil, making your comment "Supersonic airflow disrupts airflow over an airfoil, often causing compressor stall" complete jabberwocky.

Think of a logic 101 problem.

A. A stator blade is an airfoil.

B. Supersonic airflow disrupts airflow over an airfoil, often causing compressor stall.

C. A wing is an airfoil

D. Supersonic airflow disrupts airflow over a wing, often causing compressor stall.

It doesn't work.

Specificity begets credibility. If you want to establish (and maintain) credibility, please work on being specific with your comments. You've already had to acknowledge one verbal faux pas ("speed" vs "velocity") in your short time on this board. Of course, you are following in Tiffany's high-heeled footsteps, so you have a ways to go to beat "her" keepers.

FACT: Supersonic airflow disrupts airflow over the fan (stator and rotor) blades in the compressor section of many aircraft engines, often causing a compressor stall.

There. Fixed it for ya.

reply to post by trebor451


Please, guys....trebor AND the Ph.D. guy ( smile ) we all know that you (and I) are pilots.

Off-topic bickering will just confuse the issue, here.

Let's not provide "Tif" (aka as...well, I won't say, I think it's obvious to most of us) any "ammo" to further twist and contort posts.

Instead, "she" shall continually rely upon the same tactics .... that is, the continued "efforts" of posting the same unsubstantiated "diagrams", always with the intent to fool the ones who are NOT pilots, and further their baloney claims.

The specifics of aerodynamics, and aeronautics that most of us understand intrinsically are difficult to convey, in writing, to those who haven't personally experienced it.

It's like: Teaching a kid to tie his/her shoelaces. You can write reams of words describing it....But, until you actually DO it a few times, and learn the "muscle memory" aspects that are employed....any number of words is insufficient, lacking the practical.....AKA, the "hands on" learning.

I see the score still remains after FOURTY-THREE pages -


Evidence for my argument (Reported speeds/control "impossible", "improbable", "The Elephant In The Room") -

Data - NTSB, Boeing, Limits set by the manufacturer based on flight/wind tunnel testing
Precedent - EA990, China Airlines 747SP, TWA 727, 737, Modified DC-8, all suffered in flight structural failure, crash and/or lost control and needed 10's of thousand of feet to recover, or was modified to exceed it's manufacturer's set limits.
Numerous verified experts - (Many posted in this thread - www.abovetopsecret.com...)



Evidence for the argument of those who blindly support the OS (It is easy to control an aircraft at Vmo+150) -

"Because the govt told me so..."

Data = 0
Precedent = 0
Verified Experts = 0

Again -

Please let us know when you find one verified pilot willing to support your claims that it is "easy" to control a 767 at Vmo+150, Va+220 --and pull G's-- for a pilot with less experience than one who couldn't control a 172 at 65 knots. Please let us also know when you have any type of evidence for your argument other than assumption or "Because the govt told me so..."

It *IS* possible to fly aircraft into buildings. Pilots land their aircraft very accurately onto runways by hand flying visual approaches, so therefore they can hit a building by hand flying into it visually, too.

I flew the alleged flight path to the Pentagon in the sim, and it was easy, as it would be for anyone who remotely knows how to fly an aircraft. It also didn't require "jet fighter" manouvers to do it, either. I didn't even exceed 25 degrees of bank or -5 degrees of pitch (normal bank/pitch for an aircraft during normal, everyday operations with fare paying passengers on board).

Anyone who tells you it is very hard to do is either lying, or attempting to fly a flight path not flown that day.

Compressibility applies beyond Mach 0.30. Above Mach 0.75 you are in the trans-sonic range. Unless the aircraft went supersonic, the engines would be fine.

You may find that beyond VMO at 2000 ft you get buffeting and maybe aileron control reversal, but only a flight test would actually tell you.

The aircraft VMO would be about 340 kts; it was reportedly flying at 450 kts. This is approx. Mach 0.67.

If you're going to discuss aerodynamics, controlability etc.. please do your research carefully.

Originally posted by trebor451

D. Supersonic airflow disrupts airflow over a wing, often causing compressor stall.

It doesn't work.

So at 250 kts the blades go past mach 1 and the engine compressor stalls then...right?

Originally posted by Xtrozero

Originally posted by trebor451

D. Supersonic airflow disrupts airflow over a wing, often causing compressor stall.

It doesn't work.

So at 250 kts the blades go past mach 1 and the engine compressor stalls then...right?

Probably not at a low aircraft AOA because the inlets and ducting is designed to handle flows at normal operating speeds and attitudes. I'm going to quit even trying to explain the the aerodynamics of axial flow engine compressor sections. Like the previous poster said, it's like trying to write someone a lesson on how to tie shoelaces and since I live in Besseterre, I rarely wear shoes. So I'll just give some reading materials.

aviationglossary.com...

www.thaitechnics.com...

www.worldlingo.com...

And some of the efforts to design around the problem are:

For the earlier Learjets, Westwind, and Hansa - (GE CJ610 with variable inlet guide vanes) www.scramble.nl...

The F-4 with a General Electric J-79 had a different solution - variable stator vanes www.gas-turbines.ca... 5&t=70

The F-4 also used variable inlet ramps that were controlled by the air data computer httpc://www.aviation-history.ciom/mcdonnell/f4.html As a trivia note, the painting of the Phantom at the beginning of that article is of Robin Olds over the Cong River in Thai Nguyen Province in North Vietnam. The aircraft is one that was in our squadron, the 555th TFS, the "Triple Nickel." based in Udorn, Thailand.

The problem was extreme on the J-85 powered SR-71 Blackbird and required a variable inlet spike, two sets of inlet bypass doors, suck-in doors, and centerbody bleed valves to dump air out. www.enginehistory.org...

I'm beginning to wonder if perhpas too many 9/11 "deniers" (like "Tiffany" here) get all of their physics and aeronautics/aerodynamics education from cartoons?

Like, this one. (Especially the last minute or so....):

Originally posted by Guenter

Originally posted by Doctor G
I thought the article was really interesting in that you just cannot hit the Pentagon in a 757 or 767 flying 20 feet off the ground for a mile. These planes are just not designed to do it. Not even an expert can do it.

That is correct. A phenomena called "ground effect" would make it extremely difficult to fly such a heavy plane with a low wing loading at such a high speed that low above the ground. Fighter and attack jets are designed with a high wing loading and thus they are able to perform the stunts at airshows to fly past the crowds at a few ft above the runway. It is a stunning and impressive act, but can't be copied with a 757.
Those of you who may be regular air-travelers will have on occasion experienced this "ground effect" when a pilot for what ever reason miscalculates his landing speed and approaches too fast. Then the sensation is that the plane seems to be "floating" for ever over the runway till it finally bleeds off the excessive speed and settles its wheels onto the pavement.
The 2 planes hitting the WTC is not to be disputed, but it can be said with pretty much 100% certainty that they were NOT piloted by people who could not even manage a Cessna 172. The Pentagon was definitely NOT hit by a 757.
A bit of a fact concerning aircraft crashes: The 2 planes hitting the WTC, well it's obvious that nothing is left of them. However any "normal crash" - and any news pictures on sees of a crash, ONE thing always stands out, namely the TAIL of the aircraft. This is almost always that remains pretty much in one piece after a crash. Either it rips off because it is the 1st to get ground contact or it simply survives because it is the last piece of the plane experiencing any impact, - either or, the tail remains in one piece 95% of times. So where is this tail of the 757 at the Pentagon?
A little information on the Cessna 172 and its smaller "Sister" the 150. Many flight instructors are divided in what is the best plane to train a new pilot. The Cessna 150 & 172 series are the so called "VW of the Air" - meaning that almost anyone with a bit of brains can manage this plane. The landing speed on the Ce-150 & 172 is very "stretchable", - meaning you do not have to be exactly at 45kts flare out speed, you can do it anywhere between 35 to 50 kts. This is what many instructors see as a problem since it teaches students "not to care too much about the correct speed", which then becomes deadly once the student progresses to higher performance aircraft. Remember the Baseball player or what ever who flew his plane into a NYC apartment building? He too was a Ce-172 trained pilot that then invested in a much more powerful and more skill demanding aircraft, and subsequently got killed. Some flight instructors, I am one of them, prefer planes for their 1st time students that have a set speed without much of a lee-way for "playing with the numbers". These planes are harder to train on in the beginning but instill a discipline in the novice pilot that will make it easier for him to transition later on to more complex aircraft.
So what the OP meant in this article is that "IF" these terrorists could not even fly a Cessna, then there is no way they could manage a 757, even with simulator training.
To play devils advocate, the ONLY way they could have done it would have been that they had been in reality ex air-force pilots and commercial pilots and had just played "dumb" before their flight instructors to throw them off the radar for the FBI.

Guenter

reply to post by 4nsicphd


To be honest I never heard of an issue of aircraft speed and engine RPM creating engine compressor stalls. All compressor stalls I have experienced were caused by rapid deceleration of the engines with a mechanical issue associated with it. When the Air Force switched to the safer JP-8 fuel we did have them on startup if the fuel controls were not properly tuned to the different fuel. In this case we could get a 25 foot fire ball out the rear end, scaring the crap out of everyone, but unless compressor stalls are uncontrollable they do not do damage.

As people have stated, and yourself, if this condition is true then the engines are basically designed within a range and with a mach 1 combination of speed and power there would not be compressor stalls since that would mean a plane flying 250 knots at high power would experience this, so I guess my question is how do you know that 450 knots is still not within that range?

reply to post by pacific_waters


The question I have that seems to hit in this area is whether ground effect creates an easier flying environment or a harder one. I been at a little over 300 KTS at 25 feet above the ocean flying into Diego Garcia and once we entered ground effect the airplane started to ride on the pressure bubble underneath it with little effort needed in controlling the altitude.

Originally posted by Xtrozero
reply to post by 4nsicphd

 

To be honest I never heard of an issue of aircraft speed and engine RPM creating engine compressor stalls. All compressor stalls I have experienced were caused by rapid deceleration of the engines with a mechanical issue associated with it. When the Air Force switched to the safer JP-8 fuel we did have them on startup if the fuel controls were not properly tuned to the different fuel. In this case we could get a 25 foot fire ball out the rear end, scaring the crap out of everyone, but unless compressor stalls are uncontrollable they do not do damage.

As people have stated, and yourself, if this condition is true then the engines are basically designed within a range and with a mach 1 combination of speed and power there would not be compressor stalls since that would mean a plane flying 250 knots at high power would experience this, so I guess my question is how do you know that 450 knots is still not within that range?

I was a big problem with the U-2. It was designed to fly high enough that the Russian air to air missiles couldn't reach it. But at 60,000' it was necessary to fly it in what came to be called "coffin corner", or that part of the flight envelope where the high altitude stall line meets the high speed limit, usually being the critical mach speed.. With the early U-2s, powered by the Pratt and Whitney J-57-P-37, the engine would, at high speed and high altitude, flame out (quit) from compressor stalls. www.spyflight.co.uk... The J-57 had no variable geometry inlet or stator vanes or variable ramps. The Air Force remedy was to re-engine all of the existing aircraft with the Pratt and Whitney J-75 and calling the new variant a U-2C. That engine, with a swept forward air intake to reduce intake shock wave was used in the F-105B Thunderchief II, nicknamed the "Thud" for the sound it made hitting the ground.www.globalsecurity.org...
To assure proper engine operation in all flight regimes, the manufacturer does both wind tunnel and flight tests. Boeing has been asked for those test results with respect to the 757 but has refused to release them. citing their proprietary nature.And noone has come forward to talk about having taken a 757 to Vmo + 150.

Originally posted by weedwhacker
I'm beginning to wonder if perhpas too many 9/11 "deniers" (like "Tiffany" here) get all of their physics and aeronautics/aerodynamics education from cartoons?

Thanks for the old cartoon, but I think you've put this shoe on the wrong foot.

Tiffany is the only one who is actually posting technical diagrams and showing the hard facts of the issue.

Others have just been making fools of themselves trying to contradict her without contradicting the basic facts she is stating. Which is apparently very difficult for them and their responses come across to me as very forced and reaching.


Here is the relevant diagram:




I watched this thread and for I don't know how many pages, she kept asking a single question of weedwhacker and others based on this diagram and what it plainly shows, and for all those pages they avoided giving a straight answer. Why? Then when they did finally give a straight answer, it was blatantly wrong. That's why they avoided giving a straight answer for so long. Then I guess in the end they just decided they would rather be wrong and keep pretending to believe a fairy tale than actually admit being wrong.

If anything this thread has only made me question if some of these "debunkers" are really pilots in the first place, or if they are exaggerating or outright lying, or just totally incompetent. Pilots have to be on public record to fly in this country after all. It's like a college degree or any other information verifying qualification. Why are they afraid to show it?

Originally posted by bsbray11
It's like a college degree or any other information verifying qualification. Why are they afraid to show it?

So what is the point in that? It's kind of funny that this has been the only thread in the years I been on ATS that people all of a sudden want to see personal information. As I said this is not about the people here (as some want it to be) it is about what happened. If you think anyone can come here and post their Youtubes and "diagrams” and say case solved then you either want to believe no matter what or are somewhat naive. Not to jump in with both feet with these other theories doesn’t mean blind devotion to the OS either, but that seems to be the trend for what people call it.

I guess you believe that a plane will come apart at 421kts, right. Well that is what the chart...oops I mean diagram says. If you say well no it can go a little over that…well just what number is that? Boeing has not come out and said it is impossible, and it is unfortunate we do not have a huge amount of data of airliners flying Kamikaze style at full power into buildings to establish a history on what can or cannot be done…we also do not have too many live pilots to ask either….

.... Hey 1/3 did do it! Two hits out of two would be lucky. Who said the aircraft did a roll manouver?

reply to post by bsbray11


Apparently you missed the answers....they WERE given. Just, were ignored.

That ubiquitous (and generic) 'V-g diagram', again. Is it being interpreted correctly, by the "9/11 hoax believers"? What does it mean, and HOW do they read it?

All it indicates is the relationship of g-loads and airspeeds. Any pilot knows this, and can 'feel' it when flying.

Still, in terms of 9/11 in general, and United 175 in particular, the 'diagram' is useless. It shows that "structural damage" will occur under certain condiitons, or combinations of conditions. People know this, already.

But, just what IS "structural damage". Apparently the "9/11 hoax believers" interpret that phrase to mean instant and total destruction of vital structures, leading to the failure of the airplane to remain airborne. That misconception seems to be the goal of "Tiffany", and "her" merry band of ridiculous cheerleaders at the (discredited many times ) "Pilots" website.

The "diagram" is like a dangling participle, and is used to IMPLY something that distorts reality. In fact, in direct questioning (multiple times) "Tiffany" has refused to answer when asked if "she" thinks that a Boeing 767 will immediately come apart upon eaching one knot over 420....


So, what will happen when the airframe is subjected to exessive (as in, outside published design limits) airspeeds? AND, how much of a "buffer zone" is built in to those speeds, and their derivation?

For Boeings (and other manufacturers), I'd say at least 150% safety margin, to be conservative. That's just an over-all average, as specific items and structures and components will vary. That is a total WAG, as there really are no hard numbers on it, from Boeing. But, having flown them for many years, they DO have a feeling of solidity and strength that is comforting.

As to exceeding the published "max" speeds, and damage. It will vary, again....but the severity of any 'lasting' damage would depend on not only the amount of speed "over the max", but the elapsed TIME as well. Along with any excessive g-loading that occurs simultaneously. What might be 'damamged' first? Well, non-critical components, most lkely. Fairings, removable panels, etc. But, the major structure and airworthiness would require extreme and repeated abuse in order to result in the airplane "falling out of the sky".

Finally, "Tiffany" keeps tossing about the instance of (it was Hani Hanjour, I believe....the 'pilot' of AAL 77, NOT UAL 175) of the poor flying ability in a Cessna 172. Big deal....undoubtedly, he WAS a poor pilot. But, in the case of wanting to be "signed off" to rent the airplane, he was deemed to not be good enough for any of the instructors' satisfaction. This entails the ENTIRE assessment of his abilities. Not just "drilling hiles in the sky". It was that underwhelming performance that led to their decision not to entrust him to a rental.

Chalk it up to his being weak in general, and to low experience (and, as I understand it, his unfamiliarity with the Cessna --- having done most of his general aviation flying in Pipers). I imagine, also.....personality, language, culture --- all factored in as well.

Originally posted by bsbray11

Here is the relevant diagram:

That's why they avoided giving a straight answer for so long.

Perhaps you can give us a straight answer. If you could be so kind as to:

1) Plot on that chart exactly where UAL 175 was at the moment of impact.

2) Let us all know that this chart represents precisely - to a knot - Boeing's flight test, wind tunnel and design test flight parameters and data points. Then, having done that, tell us how you know that since Boeing doesn't release such data.

Thanks. Looking forward to your straight answer.