An UNMODIFIED Boeing 767 cannot fly @ 510 knots @ Sea Level. (hoax)

If you tell me the way it was, and "don't ask any questions!"

Here's some questions:
Is the OP claiming that planes did not fly into the World Trade Center?
Is the OP claiming that the reported speeds of the aircraft was incorrect?
What is the OP's point?

reply to post by Phage


PHEW!!! He did say "UNMODIFIED"....the consensus from us so called 9/11 "truthers" is that they were military planes set up as drones!! They were beefed up and able to fly at higher speeds and able to maneuver at higher speeds.

To better understand "Margin Of Safety" with respect to real aviation...

This explains that graph from Boeing for the 767 very well.
(NINETY knots over Vd of 420 knots - bear that in mind, where 425 EAS = .99 Mach at an altitude of 22,000 ft.)And again, to understand Vd, and what a filght test looks like, go here
theflyingengineer.com...

NewAgeMan

Btw, the graph used is not "fake" but perfectly represent the facts, found here

rgl.faa.gov...

Just go to the "TCDS" Type Certificate Data Sheet Information PDF on the left side when you get there.

reply to post by LaElvis


Yes, fair enough.

reply to post by NewAgeMan

(NINETY knots over Vd of 420 knots - bear that in mind, where 425 EAS = .99 Mach at an altitude of 22,000 ft.)

But the plane wasn't at 22,000 feet and it wasn't at 0.99 Mach so that's pretty irrelevant.

reply to post by Phage

Phage
Here's some questions:
Is the OP claiming that planes did not fly into the World Trade Center?
Is the OP claiming that the reported speeds of the aircraft was incorrect?
What is the OP's point?

No.
No.
What the poster above said.

LaElvis
reply to post by Phage

 

PHEW!!! He did say "UNMODIFIED"....the consensus from us so called 9/11 "truthers" is that they were military planes set up as drones!! They were beefed up and able to fly at higher speeds and able to maneuver at higher speeds.

reply to post by Phage


"Irrelevant?"

C'mon Phage, you're the science guy, so you would KNOW that it's certainly relevant.

The air is 2/3rd thicker at Sea Level than it is at 30,000 feet, thus EAS. The Vd structural limit for the Boeing 767 (of 420 knots) is expressed as EAS, because it represent the maximum aerodynamic pressure on the airframe, which makes sense, because according to all precedents (of planes breaking apart) and via wind tunnel and flight testing, which takes place at higher altitude, UNMODIFIED commercial aircraft break apart due to "flutter" at around Mach 1.0 (which is achieved in a dive) or, an EAS of about 425 knots at sea level. It was all covered in the OP, in detail.

EAS:
EAS is sea level airspeed. As a factoral expression of the equivalent dynamic pressures on an airframe at low vs. high altitude, because the air is so much thicker at sea level, there is an airspeed appropriately titled "Equivalent Airspeed" or EAS.
The air is thinner at higher altitudes so the aircraft will need to go faster to match the amount of air hitting the airframe at low altitudes, in thick air.

EAS is defined as:
EAS is the airspeed at sea level which produces the same dynamic pressure acting on the airframe as a True Airspeed at higher altitudes. It is used for determining aircraft performance, structural integrity.. .etc. The Vd limit is expressed in an EAS. In other words, to be more specific, 510 knots at sea level (EAS) would produce the same dynamic pressure as 722 knots True Airspeed (TAS) at 22,000 feet.

reply to post by NewAgeMan


Oh.
So...why? Why beef them up so they could operate at higher speeds?
Why did they need higher speeds?

reply to post by NewAgeMan

because according to all precedents (of planes breaking apart) and via wind tunnel and flight testing, which takes place at higher altitude, UNMODIFIED commercial aircraft break apart due to "flutter" at around Mach 1.0 (which is achieved in a dive) or, an EAS of about 425 knots.

Please provide evidence that unmodified commercial aircraft will break apart at an IAS (which represents the actual airflow) of 425 kt. Please provide wind tunnel and flight testing data which indicates this.

reply to post by Phage


Why, is "irrelevant". Just going by observation.

Same thing with the Twin Towers, which were quite obviously destroyed with explosives and not as a result of the plane impacts and fire, according to the laws of physics like the first and third law of motion and conservation of momentum, because they were destroyed, rather explosively, from top to bottom to within 4-6 seconds of absolute free fall from the same height in nothing (but air). Thus, it's only within that difference of time that every single weld and bold and joint would have to "fail" all along the entire length of remaining structure. Heck, about half way through the North Tower destruction there was about half less building material above the remaining half and yet the explosively ejecting debris wave continued, unabated and without any loss of momentum, all the way to the ground. Like this observation, it's self evident and as clear as day.

To then ask how did they wire the buildings, or to suggest that such a thing is not possible because it would involve too many people, isn't a rebuttal to the only possible conclusion that may be drawn.

reply to post by NewAgeMan

Why, is "irrelevant".

Oh. They just did. For no particular reason. Got it.

Same thing with the Twin Towers, which were quite obviously destroyed with explosives and not as a result of the plane impacts and fire,

Again why. If the buildings were rigged with explosives. Why bother to reinforce the aircraft? Why not just drive them at cruising speed into the buildings?

reply to post by Phage


The Vd structural limit of 420 knots is arrived at by wind tunnel, and flight testing - see the Airbus example of that process included in the OP for more on how it's determined.

As to precedents in terms of the very outer edge of barely surviving, or breaking up, i'll come back to you with those, of which there are many. At altitude, even in a dive, mostly uncontrolled dives, and always at altitude (or they'd just hit the ground) unmodified commercial aircraft cannot go hardly a hair past Mach 1.0 (or 425 EAS - same diff as far as dynamic pressures on the airframe) without experiencing flutter and ending up at risk of or breaking up.

There's lots of precedent, and anyone is free to search them out. But i'd be happy to furnish some examples, like tomorrow evening because it took a while to pull all this info together.

Rest assured there's precedent, and it's about Mach 1.0 or just a hair over at altitude or an EAS of about 425 knots at sea level which again, is the same difference in terms of dynamic pressures at low vs. high altitude.

In fact, that will make a good addition to this thread, all the best examples of precedent in terms of narrow survival and break-up, so i'm glad you asked. I'll work that up over the next few days, but in the interim, you're more than welcome to go out and bring back examples of just haw fast a Commercial Airliner can go without breaking up.

Of course, this doesn't even begin to factor in the issue of controlled flight at such airspeeds, but we don't even need to go there as far as this evidence goes.

reply to post by NewAgeMan


Exactly, if there is only ONE logical conclusion to a hypothesis why look for others?? The only way the buildings can free fall is with NO resistance, the only way to eliminate resistance is to explode the floors below....or cut them with nano-thermite!!! In the History of steel skyscrapers none had ever been destroyed by fire....and on that day 9/11 the Government is telling us that "3" did......IMPOSSIBLE ODDS!!!

Phage

Again why. If the buildings were rigged with explosives. Why bother to reinforce the aircraft? Why not just drive them at cruising speed into the buildings?

I don't know, and can only speculate. I have some hypotheses, including the potential identity of the aircraft in regards to those modifications, but i'd like to keep this fact-based only in regards to what can be proven. Same goes for the proof that the twin towers were destroyed by explosives and not as a result of the plane impacts and fire.

Take it easy Phage, and please take the time to digest what's been presented before assuming or jumping to conclusions, and laying out all these why's and what if's.

As you know, the basis of science is observation, not mere speculation.

so as precieved, how do they land in bad weather? varying conditions, wind speed, air density, snow filled air(solid particles) how do you land these things without acceptable adjusting parameters? I am not disputing anything, just asking why such hardline limitations???

reply to post by NewAgeMan

but i'd like to keep this fact-based only in regards to what can be proven.

Good. Can you prove that an unreinforced commercial aircraft will break up if it exceeds 425 knots?

I'm not sure why you keep bring up mach numbers. Yes, at transonic speeds stresses and turbulence due to the development of shock waves become concerns but the aircraft was not transonic at the altitude it was flying. That is why talking about 0.99 mach at 22,000 feet is irrelevant.

Phage

Good. Can you prove that an unreinforced commercial aircraft will break up if it exceeds 425 knots?

425 knots EAS. Yes.

And again, the Vd structural limit for the Boeing 767 is 420 EAS, where the flight testing for structural integrity takes place at altitude, and usually pushes something around .96 Mach or thereabouts, as with the Airbus example cited in the OP, which itself required serious redesign and modifications to achieve flight testing certification as the real-life, full scale follow up "flutter test" to the wind tunnel testing.

In that video, for the Airbus380 flutter test, they descended in a steady dive from 38,000 feet aiming for a Vd of Mach .96 (it's a big plane with lots of surface area) which to certify required some major modifications.

I don't think i need to re-quote the meaning of EAS again, to explain the difference in aerodynamic pressures on the airframe at high vs. low altitude. Will have to check the Airbus380's Vd as expressed in EAS, but it's probably very close to 420 knots, as it is for the Boeing 767, since 425 knots EAS is the equivalent airspeed of .99 Mach at 22,000 ft.

It's elementary.

Just to be clear, it's an equivalent airspeed. No one is suggesting that the plane was travelling near Mach at 700 ft. alt. Not even the Concorde can travel at Mach 1 at Sea Level.

I'm not trying to deceive or mislead anyone here. EAS is most definitely relevant though.

Will come back to the thread later with examples of precedent, which again are or will be at altitude, and thus will require an EAS to understand the equivalent airspeed at sea level in regards to the farthest outer reaching threshold where a diving commercial airliner will either barely survive or break up, which is indeed at around an EAS, at sea level, of about 425 knots.

No need to keep going 'round on this Phage.

I'll bring back some precedents, to highlight and prove this, but you cannot maintain that EAS from high altitude TAS is not relevant because there's no other way to express the equivalent dynamic pressures involved at high vs. low altitude.

reply to post by NewAgeMan

425 knots EAS.

Yes. I know.

Just to be clear, it's an equivalent airspeed. No one is suggesting that the plane was travelling near Mach at 700 ft. alt. No even the Concorde can travel at Mach at Sea Level.

And yet you keep quoting mach numbers for some reason. Mach numbers at 22,000 feet.

Will come back to the thread later with examples of precedent, which again are or will be at altitude, and thus will require an EAS to understand the equivalent airspeed at sea level in regards to the farthest outer reaching threshold where a diving commercial airline will either barely survive or break up, which is indeed at around an EAS at sea level of about 425 knots.

Lot of words to express a simple thought but good, that's what I'm looking for.

because there's no other way to express the equivalent dynamic pressures involved at high vs. low altitude.

Well you could use IAS which is a direct measure of those pressures.

teslahowitzer
so as precieved, how do they land in bad weather? varying conditions, wind speed, air density, snow filled air(solid particles) how do you land these things without acceptable adjusting parameters? I am not disputing anything, just asking why such hardline limitations???

It was addressed in the OP

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.

theflyingengineer.com...

and HERE.

I'm not sure what the average landing speed is - check that, it's about 135 knots

www.boeing.com...

reply to post by NewAgeMan

Here's a little something for you to chew on.

Vne/Mmo - Mach .80 (Never Exceed/Maximum Mach Number)

www.flywestwind.com...

The yellow arc terminates at the red line—VNE—the velocity that should never be exceeded. VNE is 90 percent or less of the demonstrated dive velocity (VD), a calculated value and/or the speed at which a test pilot flew the plane with no vibration or buffeting severe enough to result in structural damage.

flighttraining.aopa.org...


So, what was the Mach number for the speed and altitude we're talking about again? I'll help you. Seems its about 0.67, seems the plane was flying within placard limits.