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The importance of the angle of impact comes from the effects of gravity and the distance that can be travelled across surface structures before hitting the ground. I don't see where you mentioned the impacted medium. Which medium you had professional experience with compares to a building with a dozen lines of parallel support columns and various walls?

This discussion is frustating because it's like shadow boxing. You make claims without going specific about them. As Migeru pointed out, I have a level of physics education to at least follow your technical arguments if made explicit.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Sep 15th, 2006 at 04:02:49 PM EST
[ Parent ]
now you're clutching at straws.  gravity is a minor matter in this type of event - with forward velocity equaling 520 mph?  it affects lift and drag, but we're not looking at aeronautical effects, we're talking about destructive effects of impact

and we're not talking about the molecular level either

this is the FIRST incident of a plane "vaporising" due to an impact and you can't even see any metal vapour coating on the buildings or on the cable spools in front of the building, about 15 feet from the impact point.  amazing!  a plasma effect from Jet-A1 fuel (which has about the same properties as diesel fuel)

by manon (m@gmail.com) on Fri Sep 15th, 2006 at 04:09:57 PM EST
[ Parent ]
now you're clutching at straws.  gravity is a minor matter

Gravity was just a small part of what I wrote, picking it out of context, and as the only bit to respond to, more fits your charge.

with forward velocity equaling 520 mph?

For a falling plane, gravity adds to speed before impact and adds 1G to impact force. For a plane flying into a building more or less level, the speed you name is initial speed. This was of course an academic point making part of my argument countering your dismissal of impact angle as a factor, not a specific Pentagon impact argument.

this is the FIRST incident of a plane "vaporising"

Vaporising??? Are you now taking figurative speech literally? I again refer you to the photographs of wreckage from the wings.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Sep 15th, 2006 at 04:20:58 PM EST
[ Parent ]
there is no wreckage from the wings.  

there is a burn pattern on the building but nothing that would indicate the geometry of the object that caused it.

by manon (m@gmail.com) on Fri Sep 15th, 2006 at 04:37:32 PM EST
[ Parent ]
By now its pretty obvious that you haven't really looked at the photos in my link, or just scrolled across them without reading even the captions, not to mention the explanatory text.

No wreckage? I must be hallucinating:

Here I must be seeing paper clips and the piece of the Global Hawk:

Bur damages? These aren't burn damages:

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Sep 15th, 2006 at 04:52:07 PM EST
[ Parent ]
no, sorry, I see a part of a nose cone that should have been the first thing to strike the building, but it doesn't seem to be discoloured in any way

I don't see anything except some soot on a building that was hit by something which some people tell me was an airplane.  I can't see anything on the building that convinces me of that.  There is some debris, but very little for such a large object such as a 757.  

Sorry but that's what I see

by manon (m@gmail.com) on Fri Sep 15th, 2006 at 05:20:35 PM EST
[ Parent ]
Okay but - have you considered what's involved in crashing an airliner into a building * exactly * at ground level?

This may have been debunked already, in which case I'm happy to see links explaining how it was done.

But otherwise, this one has me baffled.

Normal airport landings use a system called ILS which guides the pilot to the runway, and optionally autolands if visibility is poor, or the pilot is feeling lazy.

The Pentagon obviously had no ILS. So we're talking about aiming something with the handling characteristics of a very, very large and unwieldy object, travelling at a very high speed.

I'd estimate the target corridor subtends an angle of a couple of degrees. Too high and you overshoot. Too low and you crash into the ground well ahead of the target, spraying the facade with debris, but not doing any structural damage.

You have to get this angle right while flying at between 300 and 500mph. This doesn't give you a lot of time to make pitch and altitude corrections during the final approach.

You can't use the altimeter to improvise a glideslope because there are no clear horizontal cues outside of the windows that you can check against - and everything is happening too fast to run a checklist anyway.

So you're:

Not using instruments or other aids

Approaching at a rate at which everything is happening between 2 and 4 times faster than for a typical landing.

Hitting a target corridor, which has to be accurate to (let's be generous) a few degrees

In something with the handling characteristics of an airborne express train

This may be exactly what happened. But if so, it's extremely impressive flying.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Fri Sep 15th, 2006 at 06:15:48 PM EST
[ Parent ]
If the target was the Pentagon (you know, the largest building on earth), it's not that impressive, unless you say that the pilot actually targetted the part where he actually hit.

The fact that he hit so low suggests that he almost missed the target, which is not surprising, as you point out.

In the long run, we're all dead. John Maynard Keynes

by Jerome a Paris (etg@eurotrib.com) on Fri Sep 15th, 2006 at 06:23:23 PM EST
[ Parent ]
It's not that simple. Come on - think this through.

The Pentagon may cover the biggest surface area of any building, but it's not particularly tall. In fact it only has four storeys, at maybe fifty feet. There's a scale photo from a recent study here. For comparison the tail fin on the 757 is just over 44ft.

Let's be conservative and say the approach speed is 300mph, or five miles a minute.

Let's say you're a minute away from your target at an altitude of a couple of thousand feet. How tall does a four storey building look five miles away at a shallow angle?

Fifteen seconds from impact, that four storey building is still more than a mile away.

Because I'm in a pedantic mood, I've worked out the visible width of the target corridor from a mile away. It's a little more than half a degree. And that's just to hit the damn thing at all, never mind score a bullseye on the ground floor.

Let's call it a degree if you assume that some overshoot into the body of the building still counts as a success. (And that's generous considering the actual shallow angle of approach.)

Unlike a car, which is fairly responsive, any altitude and pitch correction is going to take at least a few seconds to work itself through your brain, the avionics, the engines and flaps. Mostly likely you'll overshoot any correction and have to compensate in the other direction, which will eat further into your time allowance. What you certainly can't do is throw a 757 around the sky like a sports car.

Still, being even more generous, the reality is that if you're more than a few degrees out a mile away, you've already missed - by a long way.

As I said - impressive flying.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Fri Sep 15th, 2006 at 07:25:08 PM EST
[ Parent ]
I doubt it's much harder to hit than a runway.

In the long run, we're all dead. John Maynard Keynes
by Jerome a Paris (etg@eurotrib.com) on Fri Sep 15th, 2006 at 07:27:32 PM EST
[ Parent ]
Hitting the ground floor is impressive only if the pilot was aiming at the ground floor.  

Do you if the pilot was aiming for the ground floor?

And if so ... how?

(Just being my usual amiable self  ;-)

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre

by ATinNM on Sat Sep 16th, 2006 at 12:33:40 AM EST
[ Parent ]
extremely good argument.  
by manon (m@gmail.com) on Fri Sep 15th, 2006 at 06:47:59 PM EST
[ Parent ]


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