Jet engine sim for testing 9/11 planes

FAA information about Wake Turbulence:

www.faa.gov...

Originally posted by weedwhacker
Somewhere there is a graphic that shows the flow patterns behind engines....of course, this refers to engines on the ground, since that is the real 'problem' of 'jet-blast'....

Here you go:
757 Engine Wake and Noise data
Enjoy!


[edit on 4/11/2008 by defcon5]

Originally posted by Zaphod58
If you had actually READ any of the links we have posted, jet blast comes out of the exhaust in a cone of approximately 20 feet wide from the back of the engine IIRC. .

Yes, so you would agree then that if it a jet was within 20 feet of cars the jet blast would hit them?

Originally posted by C0bzz
I already did correct you. The most wake turbulance is created when the aircraft is CLEAN, HEAVY, and SLOW.

But the video shows the the biggest wake was when the jet slow with gear and falps down. Please check the first 15 seconds of the video.

[edit on 11-4-2008 by ULTIMA1]

reply to post by defcon5


Excellent find, defcon!!

There is more, but it's buried in my Flight Manuals. You can ask the line pilots for a copy of their pages, if you get the chance....they'll know what you mean. In fact, why not copy as much as you can, then post it?

WW

Originally posted by weedwhacker
There is more, but it's buried in my Flight Manuals. You can ask the line pilots for a copy of their pages, if you get the chance....

I also have my Air Force manuals. But its still showing jet blast on the ground not in the aair.

[edit on 11-4-2008 by ULTIMA1]

reply to post by ULTIMA1


Ultima, let me make it clear for you.

The worst 'wake turbulence' is produced when the airplane is heavy and slow, with flaps and slats extended, especially in the 'landing' config.

Since full flaps and slats cannot be extended, unless the gear is down, then you assume it has something to do with the gear. It does not. It is simply a fact that there are in-cockpit warnings if the flaps are selected beyond a certain range, and the gear is not yet down and locked.

In an airshow situation, I guess they can pull C/Bs and change that, in order to 'show' the airplane in question....

In the same token, we hae seen low 'fly-bys' of airplanes at about 20 feet off the deck, in the 'cruise' config.....either the pilots have to endure the GPWS saying, over and over...'too low, gear....too low, flaps, too low, gear, too low flaps.....' OR...Whoop! Whoop! Pull Up! Pull Up!....back to .....'Too low, gear.....too low, flaps....'etc....or else they pull the C/B for the airshow.

Which do YOU think is the correct scenario?

WW

Originally posted by weedwhacker
The worst 'wake turbulence' is produced when the airplane is heavy and slow, with flaps and slats extended, especially in the 'landing' config.

Yes thats exactly what i have been saying.

So if the official story is correct the plane at the Pentagon was flying fast anad clean so it would not have made the worst wake turbulence.

reply to post by ULTIMA1


ULTIMA, please see my post on the '737 wheel' thread....

WW

Originally posted by weedwhacker
There is more, but it's buried in my Flight Manuals. You can ask the line pilots for a copy of their pages, if you get the chance....they'll know what you mean. In fact, why not copy as much as you can, then post it?

I have hard copies of ramp manuals still somewhere that I can scan, but its going to show pretty much the same thing by aircraft type. All the other documentation, divided by aircraft type for Boeing is on the next directory level up from that link, here:

Aircraft Characteristics and Airport Planning


[edit on 4/11/2008 by defcon5]

Ultima can we now close this thread as your are wrong in your assumptions and this has been proven. your are twisting and changing your story to allow you to continue, please see all evidance given to you on this thread and actual read it, then you will find the answers that you are looking for.

Wee Mad Mental.

Also stop going on other threads and given it as evidance and that you are right, all you are doing is looking stupid and ignorant. you are not helping anything on anyone other than your self.

reply to post by weedwhacker


If I can call on your experience actually flying these beasts and not that you'd ever consider doing such a thing, but try to picture the disputed 757 coming in cleanly at high speed and descending in order to hit its intended target. At what point would the blast of the engines at full throttle be directed at an angle toward the ground?

To my knowledge of flying, admittedly limited, the engine blast could only be directed at the ground if the plane was stalling or attempting to gain altitude again. At the suggested speed the attitude of the plane would be a little nose-down to overcome ground effect which would angle the blast upward from the horizontal which is logical as you need a vectored downward force to overcome the resistance to descent so close to the ground.

Or am I way off target here?

reply to post by Pilgrum


yeah you are right Pilgrim, this point has been shwon previously however these guys dont want to accept this as it doesnt fit there theories. it is shown in the low flyby thread as well as in this one, there is a video of a 737 at an airshow doing a low speed and high speed pass over crowd and aircraft and there is no evidance of jet wash damaging people or aircraft in the crowd or the effects of wind vortex damage either.

~Ultima is wrong full stop.

Wee Mad Mental

Originally posted by weemadmental
your are twisting and changing your story to allow you to continue, .

I never twisted or changed my story.

I have posted plenty of facts to support my statement and will be posting more.

Originally posted by Pilgrum
At what point would the blast of the engines at full throttle be directed at an angle toward the ground?

You keep forgetting about the jet blast having at least a 20 foot diamter around the exhaust.

So these statments about the blast of the engines being angled at the ground are void.

Since when are airport signs directly behind aircraft?

www.airporttech.tc.faa.gov...

Airport signs at certain critical locations at O’Hare International Airport and other major U.S. airports are being sheared off their mounting legs at the frangible coupling from aircraft jet engine blast and/or wake turbulence forces.

Originally posted by ULTIMA1
You keep forgetting about the jet blast having at least a 20 foot diamter around the exhaust.

So these statments about the blast of the engines being angled at the ground are void.

Let's consider your figure of a 20' diameter for the blast which would be around the centreline of the engine and widening, therefore getting weaker as it gets further away from the engine. A high bypass jet engine on a 757 is about 8' or so in diameter so (20-8)/2 gives us how close that engine has to be to the ground which turns out to be less than 10'.

It would help if you could provide a typical distance from the rear of the engine for the 20' diameter figure but the attitude of the engine will still be a critical factor in the amount of blast experienced at ground level.

We also have to consider whether it's the full blast or the turbulence created at the edges of the blast interacting with ambient air. The engine designers go to a lot of trouble to achieve a very tight exhaust cone because it's more efficient in terms of thrust/fuel.

Originally posted by Pilgrum
Let's consider your figure of a 20' diameter for the blast which would be around the centreline of the engine and widening, therefore getting weaker as it gets further away from the engine.

Did you see what i posted about the airport signs?

And again, you are talking about a plane that is on the taxiway, sitting on the ground, where jetblast WILL damage objects and cause problems like that.

Originally posted by Pilgrum
reply to post by weedwhacker

 

If I can call on your experience actually flying these beasts and not that you'd ever consider doing such a thing, but try to picture the disputed 757 coming in cleanly at high speed and descending in order to hit its intended target. At what point would the blast of the engines at full throttle be directed at an angle toward the ground?

To my knowledge of flying, admittedly limited, the engine blast could only be directed at the ground if the plane was stalling or attempting to gain altitude again. At the suggested speed the attitude of the plane would be a little nose-down to overcome ground effect which would angle the blast upward from the horizontal which is logical as you need a vectored downward force to overcome the resistance to descent so close to the ground.

Or am I way off target here?

Pilgrum, the exhaust forces from the engines will never be directed downwards. The exhaust forces from the engines are particularly noticable during ground operations, and only affect nearby objects, say a few dozen feet behind.

In flight, of course, what is encountered is the 'wake turbulence'....this is a common term to describe the wingtip vortices, produced while in flight.

Think of them as horizontal tornados, rotating off of each wingtip....left wingtip rotates clockwise, right wingtip rotates counter-clockwise.

If you boat, you know that your boat leaves a 'wake'. This is similar, except it is in the air, not the water.

Also, if you boat, you'll know that other wakes, or the prevailing current, can affect YOUR wake. Not the best analogy, except to say....a wingtip vortice will be produced, and will descend approx 300 - 400 feet behind the airplane, and will tend to spread out, and away... They can persist for several minutes. If you are looking at an airplane that is taking off, or landing, and if there is a prevailing crosswind, then the wingtip voritce that is 'Upwind' could be 'blown' back over the runway surface, and 'linger'.

This is why, and it's a very simple rule when you fly small airplanes, always land BEHIND the point of a larger airplane's lift-off point, if landing behind a large jet that just took off. AND, always land AFTER the landing point, stay above the path of a larger jet, if you are landing behind a large jet.

As professional aviators we are taught to land within the 'landing zone'...this is the first 3000 feet of the runway...the 'touchdown zone' is designated at the first 1000 feet, and when you look at runway markings, you will see and understand.

BUT, as I said above, if you are flying a small airplane, and landing behind a big jet, then you are landing on a long runway, and avoiding wake turbulence is more important than landing in the 'landing zone', since you're a small airplane, and only need about 1500 feet of runway at most, to begin with!!

WW

Originally posted by Zaphod58
And again, you are talking about a plane that is on the taxiway, sitting on the ground, where jetblast WILL damage objects and cause problems like that.

How does jet blast damage a sign that is not behind it, maybe when the plane flys over it close then the jet blast will hif the signs?

Originally posted by weedwhacker
In flight, of course, what is encountered is the 'wake turbulence'....this is a common term to describe the wingtip vortices, produced while in flight.

But wake turbulence decrease with speed.


[edit on 12-4-2008 by ULTIMA1]