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# 9/11 plane speeds into the WTCs?

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1. I'm not sure if this factor is overlooked a lot, I have an idea of the speeds involved but I wanted your thoughts on such speeds near sea level.

The speed of one of the planes is 580 mph

http://www.cbsnews.com/2100-500164_162-501989.html

I'm not saying no planes were involved, I don't know what this is saying really, but I'm sure that planes were involved, it's just that for a Boeing, going at this speed near sea level just seems impossible.

EDIT: Problem sorted, it does seem possible, sorted out on page 2, side not; I never doubted the planes hit the building, this was just something new I never thought of so I wanted clarification about it as I had no idea, thanks.
2. It's not impossible.
3. (Original post by TheGrinningSkull)
I'm not sure if this factor is overlooked a lot, I have an idea of the speeds involved but I wanted your thoughts on such speeds near sea level.

The speed of one of the planes is 580 mph

http://www.cbsnews.com/2100-500164_162-501989.html

I'm not saying no planes were involved, I don't know what this is saying really, but I'm sure that planes were involved, it's just that for a Boeing, going at this speed near sea level just seems impossible.
Don't forget they had just made rapid descents, so the speeds quoted are quite conceivable, besides, given the variation between the two studies I wouldn't put much credence in the quoted figures being that accurate.
4. Cruise speed is 500mph, with the taps open and having just dived down from 30,000 feet then its a fairly plausible speed.
5. (Original post by Riderz)
Cruise speed is 500mph, with the taps open and having just dived down from 30,000 feet then its a fairly plausible speed.
Right, cruise speed, as in, at cruise altitude around 30000 feet.

How are such speeds above that maintained in air much denser at sea level?

Considering the maximum operating speed for the 767 is 360 knots, how is it that Vmo (velcoity max) was +155 knots for 180 seconds when Boeing themselves say that exceeding Vmo with regards to a Boeing 767 200 that "Exceeding Vmo/Mmo can pose a threat to exceeding design structural integrity and design stability and control criteria of the airplane."

British Airways examples of serious incidents include:

Vmo +10 knots for 3 seconds.
Vmo +20 knots for 5 seconds

The Vd (Velcoity dive, a dive from a height in an emergency) of a 767 is 420 knots. This is the max speed.
6. (Original post by TheGrinningSkull)
Right, cruise speed, as in, at cruise altitude around 30000 feet.

How are such speeds above that maintained in air much denser at sea level?
It depends on how quickly the planes descended, but the increased air resistance would take a while to slow them down to terminal velocity. Longer when you include the fact that they'd be picking up extra speed as they fell and that the engines were most likely on full throttle.
7. (Original post by TheGrinningSkull)
Right, cruise speed, as in, at cruise altitude around 30000 feet.

How are such speeds above that maintained in air much denser at sea level?
Are you familiar with the concept of momentum?
8. are people not bored of dissecting 9/11 yet
9. I've edited my post above to include more info
(Original post by Arbolus)
It depends on how quickly the planes descended, but the increased air resistance would take a while to slow them down to terminal velocity. Longer when you include the fact that they'd be picking up extra speed as they fell and that the engines were most likely on full throttle.
Considering parasitic drag doubles with velocity and parasitic power cubes with velocity then I'd say I Boeing couldn't attain that speed at 1000ft.
(Original post by Profesh)
Are you familiar with the concept of momentum?
Yes, and are you familiar with the concepts of velocity dive? Parasitic power? Parasitic drag?
10. (Original post by TheGrinningSkull)
I'm not sure if this factor is overlooked a lot, I have an idea of the speeds involved but I wanted your thoughts on such speeds near sea level.

The speed of one of the planes is 580 mph

http://www.cbsnews.com/2100-500164_162-501989.html

I'm not saying no planes were involved, I don't know what this is saying really, but I'm sure that planes were involved, it's just that for a Boeing, going at this speed near sea level just seems impossible.
Why?
11. (Original post by SnoochToTheBooch)
are people not bored of dissecting 9/11 yet
Again with the ad hominem. I bet you think the same "people" believe in fairies and wear tin hats.
12. (Original post by Aj12)
Why?
Because the Vmo (Velocity max) of a Boeing 767 is 360 knots and the Vd (max velocity dive) is 420 knots.
13. (Original post by TheGrinningSkull)
Again with the ad hominem. I bet you think the same "people" believe in fairies and wear tin hats.
Well...

Couldn't resist
14. Sounds plausible to me, if the plane was cruising at 500ish mph and it had just done a massive dive with the taps open then it only seems logical that it'd hit the trade center at that speed
15. (Original post by TheGrinningSkull)
Right, cruise speed, as in, at cruise altitude around 30000 feet.

How are such speeds above that maintained in air much denser at sea level?

Considering the maximum operating speed for the 767 is 360 knots, how is it that Vmo (velcoity max) was +155 knots for 180 seconds when Boeing themselves say that exceeding Vmo with regards to a Boeing 767 200 that "Exceeding Vmo/Mmo can pose a threat to exceeding design structural integrity and design stability and control criteria of the airplane."

British Airways examples of serious incidents include:

Vmo +10 knots for 3 seconds.
Vmo +20 knots for 5 seconds

The Vd (Velcoity dive, a dive from a height in an emergency) of a 767 is 420 knots. This is the max speed.
You may not have noticed, but in the event the hijackers actually did not have a lot of regard for the structural integrity of the plane. It did not appear to be high on their list of concerns.

Regardless, I think there is an apt analogy to be drawn here. Imagine you are going at 500mph and you are on top of a 30000ft mountain, and you begin to travel down the mountain. What usually happens to your speed as you travel downwards? It is implicit in your post that you believe you would slow down, which has not been my experience at all.
16. Vmo isn't like reading the top speed off for a bugatti.
17. (Original post by Bobifier)
You may not have noticed, but in the event the hijackers actually did not have a lot of regard for the structural integrity of the plane. It did not appear to be high on their list of concerns.

Regardless, I think there is an apt analogy to be drawn here. Imagine you are going at 500mph and you are on top of a 30000ft mountain, and you begin to travel down the mountain. What usually happens to your speed as you travel downwards? It is implicit in your post that you believe you would slow down, which has not been my experience at all.
Of course they wouldn't have regard, but how do you control a plane going that fast (Assuming it even is going that fast). It would just break apart.

The engines of the plane wouldn't be able to handle the speed and it'd just start to choke. From the videos I see, then plane doesn't dive down into the WTCs but they crash in at a level altitude and they come in at a level altitude.

Surely the minute they leveled off they would start to slow down after recovering from the velocity dive, which even then, is only 420 knots.
18. (Original post by Joinedup)
Vmo isn't like reading the top speed off for a bugatti.
It depends on altitude does it not?
19. (Original post by TheGrinningSkull)
It depends on altitude does it not?
yeah... But a cruising plane doesn't have the throttles anywhere near max. The engines are only at high power for takeoff and climb.
Somewhat suprising fact about passenger jet cruising speeds is that they're lower on modern planes than early passenger jets... The old hawker trident used to cruise at 580m/h... It doesn't seem like an outlandish speed to me really. Mostly cruise speed and the other parameters have been about fuel economy after the 1970s oil shock afaict.
20. (Original post by Joinedup)
yeah... But a cruising plane doesn't have the throttles anywhere near max. The engines are only at high power for takeoff and climb.
Somewhat suprising fact about passenger jet cruising speeds is that they're lower on modern planes than early passenger jets... The old hawker trident used to cruise at 580m/h... It doesn't seem like an outlandish speed to me really. Mostly cruise speed and the other parameters have been about fuel economy after the 1970s oil shock afaict.
Cruise speeds are at altitudes near 30000 feet.

Air pressure and density at cruising altitude is nearly 3 times smaller than near sea level.

Just take these figures for example:

At altitude 1000 ft air pressure is 97.6kPa
At altitude 30'000 ft, air pressure is 30.1kPa

Here's a link of the table http://www.engineeringtoolbox.com/ai...ume-d_195.html

The engines wouldn't be able to handle the denser air with such speeds near sea level.

Also, we're not talking about a hawker trident, we're talking about a Boeing 767, with a cruising altitude of 533mph anyway. Not at 1000ft either.

I'm not aware of any airliners exceeding 500mph near sea level (without breaking apart as well) so if you have any examples I'd like to see them please.

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