Jet engine sim for testing 9/11 planes

Originally posted by weedwhackerps....but you mentioned it nosed-down at the last split-second....so again, the thrust from the engines would hardly seem to affect anything on the ground....right????[edit on 4/27/0808 by weedwhacker]

Yeah, have heard from friends that flies the 757 that it has a significant pitch down tendency at high speed even at altitude.

Was thinking that it would probably do the same close to the ground at that speed.

(shouldn't post when dead tired)

Originally posted by HLR53K
Correct me if I'm wrong, but doesn't lowering the landing gear shift more weight to the bottom of the airplane (lowering the CG) and help stabilize it? .

Do you understanad what lowering the landing gear at the speed would do?

Let me ask you this, at what speed does a 757 normally land? What speed was the plane at the Pentagon doing ?

Originally posted by Pilgrum
At the last highway crossing it was low enough to clip light poles 30'+ high so it had some descending to do past that point to get low enough. It was moving at approx 700'/sec.

Correct me if i am wrong but wasn't the highway a raised highway?

Originally posted by ULTIMA1

What PDF report are you reading from? Not the 1 i posted.

Haha! How did you miss it? Seems like you don't look over the sites you post close enough. And it looks like I did more research that you did.

Go to the exact same website you posted. There should be a link at the top of the page to the right of the words "Final report".

Click on it and read through that report. The FAA were designing signs to withstand the jet blasts of airplanes taxiing on the ground.

Originally posted by HLR53K
Correct me if I'm wrong, but doesn't lowering the landing gear shift more weight to the bottom of the airplane (lowering the CG) and help stabilize it?

Kind of like adding some extra weight to the bottom of a boat. It'll add more stability for the boat when it encounters rough waters.

Perhaps at normal landing speeds, in this case it would most likely cause an aerodynamic havoc and loss of control.

[edit on 27-4-2008 by Freaky_Animal]

Originally posted by HLR53K
Go to the exact same website you posted. There should be a link at the top of the page to the right of the words "Final report".

So, they are talking about 1 test. You really are reaching aren't you.

If you would have read farther you would have also seen the signs destryed by deprting 747s.



[edit on 27-4-2008 by ULTIMA1]

reply to post by ULTIMA1


ULTIMA.....did they put the gear down? What do you have to show ths occured?

Here's what would happen.....the gear doors would likely get torn off, eventually....the two mains, and the NG would come down and lock, most likely.

When the gear doors got torn off, in the last few milliseconds, there would be a loss of hydraulic pressure.....since the doors are hydraulic...but check valves in the system would close, to ensure flight control availability.

However, I sincerely doubt AAL77 had its gear extended, at the last minute....even these stupid Arabs new it would increase drag, and tend to slow the airplane.....they wanted maximum kinetic energy, for maximum destruction potential.

What's your next imaginary idea, eh???

Originally posted by ULTIMA1

Do you understanad what lowering the landing gear at the speed would do?

Let me ask you this, at what speed does a 757 normally land? What speed was the plane at the Pentagon doing ?

I think landing speed is somewhere around 130 knots?

I've been seeing that the FDR says the B757 was flying around 350 mph (304 knots)?

At those speeds, the landing gear might be sheared off due to the heavy drag they impose. The way I see it, the terrorists might have know that it can help stabilize the plane and might have done it as a last resort out of shear desperation?

reply to post by weedwhacker


From a timing point of view, how long does it take from initiating lowering of the landing gear to the gear actually being lowered?

Or even becoming externally visible to a ground level observer for that matter.

I have doubts about the gear being lowered as one eyewitness mentioned for reasons of speed, altitude and time available to actually watch it happen.

Originally posted by weedwhacker
ULTIMA.....did they put the gear down? What do you have to show ths occured?

Gee, you really have not done any research into what happened at the Pentagon have you?

Sorry not the best site, but i have too much information to go through right now.

www.puertorico-herald.org...

"It seemed like the pilot was scrambling to keep control, and I watched as he dropped lower and lower," Sepulveda said. "Then he dropped his landing gear and started coming down even faster and lower.

As it came down, the plane was hitting light poles, the sergeant said. "Then the right wheel hit a light pole and the plane popped into a 45-degree angle. The pilot tried to recover -- go back vertical - but he hit some more light poles.

"He dipped the plane's nose slightly, and then smashed into the building," said Sepulveda, who was presented the Airman's Medal and Purple Heart by Air Force Chief of Staff Gen. John P. Jumper at the Pentagon April 15, 2002.

[edit on 27-4-2008 by ULTIMA1]

Originally posted by ULTIMA1

So, they are talking about 1 test. You really are reaching aren't you.

If you would have read farther you would have also seen the signs destryed by deprting 747s.



[edit on 27-4-2008 by ULTIMA1]

One of the two live tests that they did that pertained to the study at hand. It did say what I wrote in exact quotes. A 747 that turned adjacent to the sign. Correct me if I'm wrong, but I don't know many 747s that can make an adjacent turn while flying. Taxiing is just a logical assumption.

You may have read differently, but I read departing to mean that the B747s were destroying the signs when they were stationary and throttled up their engines right before actually rolling down the runway.

reply to post by Freaky_Animal


This is really an answer to HLR.....lowering the gear does NOT change the CG....well, except for the fact that the nose gear (NG) moves aft as it comes down from the 'retract' position....it is minimal effect on the CG.

The idea that the gear DOWN changes, or adds to the 'stability' of the airplane is erroneous.

Well....it does add drag...the 'Gear Operating' limit airspeed on the B757 is 220 knots.....this is because of the load limits on the gear doors, during the cycle. The 'Gear Extended' speed is 250 Knots...once the gear is down and locked (three green lights) means the gear is, obviously, locked and the gear doors are closed.....this is what you learn when you train on the specific airplane you are flying.....

Any more questions, I'm the Answer Man!!!

WW

Originally posted by HLR53K
You may have read differently, but I read departing to mean that the B747s were destroying the signs when they were stationary and throttled up their engines right before actually rolling down the runway.

But doesn't departing also mean getting into the air?

Do you think jet blast just dissapears when the plane gets into the air?

Originally posted by weedwhacker
Any more questions, I'm the Answer Man!!!

Well answer man tell us what happens when the gear is lowered above 500 mph at 60 feet or less above the ground?

Originally posted by weedwhacker
reply to post by Freaky_Animal

 

This is really an answer to HLR.....lowering the gear does NOT change the CG....well, except for the fact that the nose gear (NG) moves aft as it comes down from the 'retract' position....it is minimal effect on the CG.

The idea that the gear DOWN changes, or adds to the 'stability' of the airplane is erroneous.

Well....it does add drag...the 'Gear Operating' limit airspeed on the B757 is 220 knots.....this is because of the load limits on the gear doors, during the cycle. The 'Gear Extended' speed is 250 Knots...once the gear is down and locked (three green lights) means the gear is, obviously, locked and the gear doors are closed.....this is what you learn when you train on the specific airplane you are flying.....

Any more questions, I'm the Answer Man!!!

WW

Alright, time to scrap that thought!

I'm sure it does change the CG in some way, but the amount is so minute that it doesn't really matter. The weight of the landing gear themselves is pretty much nothing compared to the rest of the airplane.

I just went back to some calculations I did in college and confirmed what I said above.

Originally posted by ULTIMA1
Correct me if i am wrong but wasn't the highway a raised highway?

No you're not wrong, the highway is raised and actually has underpasses in that area which places the plane even higher above the surrounding true ground level doesn't it?

Originally posted by ULTIMA1

Originally posted by HLR53K
Correct me if I'm wrong, but doesn't lowering the landing gear shift more weight to the bottom of the airplane (lowering the CG) and help stabilize it? .

Do you understanad what lowering the landing gear at the speed would do?

Let me ask you this, at what speed does a 757 normally land? What speed was the plane at the Pentagon doing ?

For flaps 30 landings vref should be 105-125 kts. The B757-200 is slow on
final approach.
Maximum gear operating speed on most Boeings are 270 kts, gear is selected down before selecting flaps 15, in most cases between 160-180 kts.
(unless it's needed as rubberbrakes)

Originally posted by Pilgrum
No you're not wrong, the highway is raised and actually has underpasses in that area which places the plane even higher above the surrounding true ground level doesn't it?

But it also places the plane closer to the cars.

Originally posted by Freaky_Animal
For flaps 30 landings vref should be 105-125 kts. The B757-200 is slow on
final approach.
Maximum gear operating speed on most Boeings are 270 kts, gear is selected down before selecting flaps 15, in most cases between 160-180 kts.

I will ask you the same queston.

What happens when the gear is lowered above 500 mph at 60 feet or less above the ground?

Originally posted by ULTIMA1

But doesn't departing also mean getting into the air?

Do you think jet blast just dissapears when the plane gets into the air?

The FAA didn't specify and I just thought of where the jet blast would be at its maximum to the signs is where they were being destroyed.

No, of course it doesn't "disappear". I just believe jet blast becomes less and less of a factor on objects on the ground as the airplane goes higher. Wake turbulence takes over as the primary force.