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9/11: Impossible Speed & Impact Busted!

BenBurch said:
Isn't there a very tiny amount of Ti in the world? Recalling from the distant past, there is one beach in CA, USA, and two mines in the Urals?
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It can't be too scarce, Frank Gehry sheaths his buildings in it.
 

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The only commercial aircraft that used DU as a ballast were the CV-880 and CV-990. The ballast was located in the tail cone.
 
Titanium is fairly abundant in the earths crust. It's widely dispersed with few deposits that make economical sense to mine.

The usual way to produce one mole of titanium consumes 7 moles of chlorine gas and 2 moles of magnesium metal. That's a large part of the cost.
 
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HL7442 said:
The only commercial aircraft that used DU as a ballast were the CV-880 and CV-990. The ballast was located in the tail cone.
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I'm not sure that's true. Wikipedia claims early 747's used uranium in the "outboard engine nacelles" to deal with high-speed flutter.
 
HL7442 said:
The only commercial aircraft that used DU as a ballast were the CV-880 and CV-990. The ballast was located in the tail cone.
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DU is used to balance flight control surfaces where you need a small dense mass that can be placed forward of the hinge line. I know it was used on MD-80's and MD-11's.
 
AMTMAN said:
Titanium is used in commercial aircraft, however in small amounts in areas that require the sort of strength it provides. The F-14 used titanium for its wing box and box beams. It's difficult to work with and very expensive. That's why you don't see it used for that sort of thing on commercial jets. It's really not needed, aluminum does the job just fine.
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beachnut said:
The SR-71 was made with lots of Titanium; it seemed to get stronger as it aged.
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Oh, yes. I know it was used in critical areas - like AMTMAN said, such as in the frame for an F-14. I was just extrapolating from my (admittedly limited) knowledge of titanium's qualities. If you need a titanium alloy to be rigid, you end up making it brittle. If you make it so it's not brittle, it's not hard enough for weapons applications (I was thinking swords and the like when I made that statement).

So the question is whether a titanium alloyed wing would actually be practical. I thought that, because of the tradeoff between hardness and brittleness, it would be unfeasable, but Beachnut's statement made me look up info on the Blackbird (found this: http://en.wikipedia.org/wiki/SR-71_Blackbird#Titanium_structures_and_skin), and it turns out that I was wrong. The SR-71 was indeed mostly made of titanium, not just the wings. So it's obviously feasable; in fact, it was quite obviously in use for decades. That means there is definitely a point where hardness and lack of brittleness are acceptible for use on an aircraft.

You learn something new every day. Anyway, now that I have a practical example, I'm starting to dream of a supersonic, titanium private jet. :D Wouldn't that be soooooo cool? (is there a "geek" emoticon anywhere??...)
 
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Not sure if it's been pointed out yet, but the formula for kinetic energy shown at around 8:05 is incorrect.
 
JEROME DA GNOME said:
Is dive speed different that flight speed? :confused:
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The dive speed is neat; when you level off you have to slow down~! Pardox; The planes on 9/11 were going faster than they were suppose to for a 5 to 20 seconds before they were destroyed by impact. It is not as simple as the Video woo master thinks, but his ideas are better than the no plane idiots. Orange man has his own truth agenda, but it seems his mental state makes it impossible to explain what his real conclusions are; you can tell by his added BS in the Video. That video would be graded lower, due to introducing extraneous data, a fantasy foray into unexplained woo. C-
 
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Reality Believer said:
DU is used to balance flight control surfaces where you need a small dense mass that can be placed forward of the hinge line. I know it was used on MD-80's and MD-11's.
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I never knew that.
I wonder if the DU in the MD-11's had anything to do with pilot's calling it the Death Star or the SCUD.
The -11 was definately over powered especially when it had PW engines installed.


I also never realized Boeing may have placed DU to reduce engine flutter in the early JT9D-3A engine pylons.
 
HL7442 said:
I never knew that.
I wonder if the DU in the MD-11's had anything to do with pilot's calling it the Death Star or the SCUD.
The -11 was definately over powered especially when it had PW engines installed.


I also never realized Boeing may have placed DU to reduce engine flutter in the early JT9D-3A engine pylons.
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The MD-11 was called the SCUD in it's early years because they never knew where it was going to land. The aircraft had reliablity issues, it was not uncommon for the aircraft to divert enroute. It also did not meet it's range requirements. There was once a Varig MD-11 that had to divert to MCAS El Toro because the cpatain thought he did not have the fuel to make it to LAX. Another nickname for it was Mighty Disapointed-11.
 
AMTMAN said:
. There was once a Varig MD-11 that had to divert to MCAS El Toro because the cpatain thought he did not have the fuel to make it to LAX. Another nickname for it was Mighty Disapointed-11.
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I'm sure the Marines were a bit puzzled when the Varig arrived.
Toro isn't that far to LAX so that plane must've been on fumes for him to divert.
I've always loved the DC-10 and MD-11, it's a shame that the MD got such a bad rap. Swissair 111 sealed it.
 
HL7442 said:
I'm sure the Marines were a bit puzzled when the Varig arrived.
Toro isn't that far to LAX so that plane must've been on fumes for him to divert.
I've always loved the DC-10 and MD-11, it's a shame that the MD got such a bad rap. Swissair 111 sealed it.
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MD did it to itself. They tried to do the MD-11 on the cheap and it came back to haunt them. If they had invested in a new wing it would have had no problem meeting it's performance goals.
 
BenBurch said:
Isn't there a very tiny amount of Ti in the world? Recalling from the distant past, there is one beach in CA, USA, and two mines in the Urals?
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Titanium is widespread, with particularly vast deposits of rutile on Australian beaches (rutile contains Titanium Oxide).

You're probably thinking of platinum and palladium - both of which are extremely rare. South Africa and Russia are the primary suppliers, with the Stillwater complex in Montana being a rare site that has both platinum and palladium.

-Gumboot
 
AMTMAN said:
MD did it to itself. They tried to do the MD-11 on the cheap and it came back to haunt them. If they had invested in a new wing it would have had no problem meeting it's performance goals.
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A bigger horizental would have helped too. I've heard from several MD11 pilots that it was very difficult to land and has some very squirrely handling characteristics at low speed. The worst being that you have to pretty much manhandle the beast to get it to even respond. Not a good thing on approach. See the not one, but two, MD11s that flipped over and crashed on landing for no apparent reason.

I don't know if you've ever worked on them, AMTMAN, but they have an even worse reputation with mechanics. There are a bunch of "gotchas" that make those things really dangerous to work on. Those things are built to be flying, not sitting in the hangar...which is where they spend most of their time...Hydraulics, pneumatics and the APU are designed to be sort of "automatic", meaning that "stuff can start moving" without warning and even the APU will actually start itself if you select APU GEN on the elex panel. The first thing we do after one comes in(yes even though we got rid of them, we also sold our mx services to the new operator) is pull and tag a crapload of breakers and put the elex, hydro and pneumatic panels in manual mode.
It's the only plane we work on in which you have to have been to its initial school to work on it.

You also can't have the parking brake set when transferring fuel into the center tank or simply fuelling(or defuelling) the center tank because of the weird angle of the center mlg strut. Then there's the wet horizental concept which resulted from not meeting its initial range criteria. Another bad idea. And how could I forget the "barking dog" aux pump.

All the crazy stuff aside though, it's not a bad airplane to work on(except #2 engine changes:eek:)
 
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