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Flight 175 plane speed challenged

Terry said:
Just a minor comment - Vne is the speed you should not exceed. It isn't the fastest the aircraft can go.
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Actually if you watch and read the links it's disputed that the plane could actually go that fast at that altitude by Boeing themselves and stay together never mind trying to steer it into a building.
 
ZENSMACK89 said:
I don't know I'm asking on both counts. How did the plane go that fast and how were they able to maintain control? Do you think NIST has it wrong on the speed?

http://www.erau.edu/er/newsmedia/articles/wp7.html

*The problem with the conventional fan/fixed horsepower source combination, is that if the designer optimizes the fan for high altitude cruise, there may be nowhere near enough horsepower to drive the fan at sea level (because of higher air density) and takeoff performance may be severely impaired. If on the other hand the designer optimizes the fan for takeoff, then cruise performance sufferers as the fan can't ingest enough air to fully absorb the engines horsepower.
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Horsepower isn't really needed for a speedy descent, just weight, and 175 had a significant load of fuel. Competition gliders sometimes load themselves with hundreds of pounds of water so they will fly faster.
Incidentally, I can't find that quote in that particular link, using control-F under Firefox.

ZENSMACK89 said:
http://www.erau.edu/er/newsmedia/articles/wp7.html

*Due to the low atmospheric pressure at this altitude, the air density is less than one-third of that at sea level. This reduced density allows the aircraft to fly much faster than it could if the air was as thick as it is at sea level. Because the air at cruise altitude is so cold and dry, the water in the jet exhaust creates ice crystals, which leave behind the familiar streaks in the sky called condensation trails or contrails.

*http://www.democraticunderground.co...mesg&forum=125&topic_id=175931&mesg_id=176252
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If you were really interested in the question, instead of cherry-picking, you might have found the answer to how the pilots kept control in your first link:

[QUOTE = Embry-Riddle]The upper cruise speed is generally limited by the speed of sound. As the temperature decreases with altitude, so does the speed of sound.
[/QUOTE]

So while it takes less power to cruise fast at altitude, the absolute limits to speed are higher down low where it is warmer, and the speed of sound is higher.
 
FWIW = For What It's Worth.

Also, in case Zen hasn't seen these, the videos that Gumboot posted several months ago are fairly demonstrative of what you can do with a commercial airliner when you aren't particularly concerned with the safety and comfort of the passengers.

It's not that you can't perform those types of maneuvers, professional pilots simply don't. That's why it looked odd to people who were accustomed to watching professional pilots fly these things.
 
ZENSMACK89 said:
Actually if you watch and read the links it's disputed that the plane could actually go that fast at that altitude by Boeing themselves and stay together never mind trying to steer it into a building.
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But it did. Or do you suggest it was not a boeing?
 
ZENSMACK89 said:
I don't know I'm asking on both counts. How did the plane go that fast and how were they able to maintain control? Do you think NIST has it wrong on the speed?

http://www.erau.edu/er/newsmedia/articles/wp7.html

*The problem with the conventional fan/fixed horsepower source combination, is that if the designer optimizes the fan for high altitude cruise, there may be nowhere near enough horsepower to drive the fan at sea level (because of higher air density) and takeoff performance may be severely impaired. If on the other hand the designer optimizes the fan for takeoff, then cruise performance sufferers as the fan can't ingest enough air to fully absorb the engines horsepower.


http://www.erau.edu/er/newsmedia/articles/wp7.html

*Due to the low atmospheric pressure at this altitude, the air density is less than one-third of that at sea level. This reduced density allows the aircraft to fly much faster than it could if the air was as thick as it is at sea level. Because the air at cruise altitude is so cold and dry, the water in the jet exhaust creates ice crystals, which leave behind the familiar streaks in the sky called condensation trails or contrails.

*http://www.democraticunderground.co...mesg&forum=125&topic_id=175931&mesg_id=176252
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Zen,

I believe there are a couple of issues here.

1. 500+ mph in level flight at 700 ft ASL seems to be problematic because of the tuning (power) issue. On the other hand 500+ in a dive does not sound unreasonable.

2. The other issue is whether the airplane can withstand drag forces (air resistance) without being torn apart. I have searched the internet a bit and found some information. A number of airplanes have low altitude maximum speeds that are around 50% of the maximum high altitude speeds. It is not clear whether this is due to power issues or structural considerations. For commercial airliners, it would make sense to design the "strength" of the airplane for cruise altitude and limit the lower altitude speeds. Otherwise the plane would be unnecessarily heavy, affecting efficiency and cost of operation. Nonetheless, airplanes do fly through rain which creates additional stress on top of drag forces. Taking safety factors into account, I would be very surprised if the 767 couldn't hold together for a few minutes at 500+ mph at low altitude.
 
Reheat said:
Boeing builds good airplanes, what's the problem?
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The problem is not the Boeings; the problem is that this very high rate of speed makes it even more unlikely the plane was being piloted by an amateur, and is more evidence the planes were actually being piloted by autopilot or some kind of remote navigation system like Global Hawk. All of us agree the high speed increases the difficulty of hitting a target.

This argument is very similar to the one we had on another thread regarding Hani's alleged maneuver with AAL77. That plane was also accelerated to a very high rate of speed before impact. Why would these terrorists, who knew they were poor pilots, have chosen to accelerate at such extreme speeds into their targets, knowing that such a tactic increased the likelihood of a miss?

Sure it is hypothetically possible that amateurs just got lucky three out of four times; just as it is hypothetically possible that War and Peace was composed not by Tolstoy, but by a monkey with a typewriter......

The more likely scenario is that the planes were piloted automatically, by people who wanted high-speed impacts to destroy as much evidence as possible of their nefarious deed.
 
ZENSMACK89 said:
Actually if you watch and read the links it's disputed that the plane could actually go that fast at that altitude by Boeing themselves and stay together never mind trying to steer it into a building.
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"by boeing themselves"?

is this an official position of the company? who at boeing said this? is it someone who would actually know one way or the other?
 
A-Train said:
The problem is not the Boeings; the problem is that this very high rate of speed makes it even more unlikely the plane was being piloted by an amateur, and is more evidence the planes were actually being piloted by autopilot or some kind of remote navigation system like Global Hawk. All of us agree the high speed increases the difficulty of hitting a target.

This argument is very similar to the one we had on another thread regarding Hani's alleged maneuver with AAL77. That plane was also accelerated to a very high rate of speed before impact. Why would these terrorists, who knew they were poor pilots, have chosen to accelerate at such extreme speeds into their targets, knowing that such a tactic increased the likelihood of a miss?

Sure it is hypothetically possible that amateurs just got lucky three out of four times; just as it is hypothetically possible that War and Peace was composed not by Tolstoy, but by a monkey with a typewriter......

The more likely scenario is that the planes were piloted automatically, by people who wanted high-speed impacts to destroy as much evidence as possible of their nefarious deed.
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No! This video says the plane could not do this. Are agreeing with this?
 
ZENSMACK89 said:
Wow can I use this? It describes the official version perfectly.
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:rolleyes: Oh, please. You have to have a theory before you can accuse anyone of attempting to spread FUD about your theory. This is just another pathetic attempt to belittle the generally accepted version of events.


ZENSMACK89 said:
Now do you have any factual information of the planes, the speed, or the skill needed to perform the maneuvers witness or as the air traffic controller called "Unheard of"?

"Unheard of" hmmmmm

Is like an anomaly?
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Equivocation. When we speak of "anomaly" in relation to the "official story," we mean "an incongruity or inconsistency." You are using the definition "a deviation from the common rule, type, arrangement, or form," in a transparent attempt to score a few rhetorical points. (Definitions from dictitionary.com anomaly.)
 
ZENSMACK89 said:
Actually if you watch and read the links it's disputed that the plane could actually go that fast at that altitude by Boeing themselves and stay together never mind trying to steer it into a building.
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We've had this discussion before.

Mr. Zen Smack, I was at Boeing Commercial on the morning of September 11th. They do not dispute that what happened was possible, plausible, or even likely.

While it is not clear a 767 could maintain those speeds at that altitude flat-and-level indefinitely, there isn't anything even faintly suspicious about it reaching those speeds after a power dive and maintaining it for 30 seconds or so.

You cannot produce a single Boeing engineer who states otherwise.
 
A-Train said:
The more likely scenario is that the planes were piloted automatically, by people who wanted high-speed impacts to destroy as much evidence as possible of their nefarious deed.
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I'll play along with you here, and ignore for the moment that you have no evidence at all for your "likely scenario" to counter the mountains of evidence for what I guess you'd say is the "unlikely scenario".

Flesh this out some more... I think you're the guy who proposes secret agents of some sort parachuting out of the planes after killing the pilots with a smuggled gun? Tie this all together if you can - when, how and where were the planes modified for remote control, why no maintenance crews noticed all that extra hardware on the plane, why they wanted a high-speed impact if they had a complex system of bombs in the towers, why they would draw attention to it by what you call a "very high rate of speed makes it even more unlikely the plane was being piloted by an amateur, and is more evidence the planes were actually being piloted by autopilot or some kind of remote navigation system", etc etc etc.
 
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TjW said:
Horsepower isn't really needed for a speedy descent, just weight, and 175 had a significant load of fuel. Competition gliders sometimes load themselves with hundreds of pounds of water so they will fly faster.
Incidentally, I can't find that quote in that particular link, using control-F under Firefox.

If you were really interested in the question, instead of cherry-picking, you might have found the answer to how the pilots kept control in your first link:

...

So while it takes less power to cruise fast at altitude, the absolute limits to speed are higher down low where it is warmer, and the speed of sound is higher.
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Warmer air is less dense (= less drag), so that is not the issue. Also the speed of sound has nothing to do with the issue at hand.

Nonetheless, the air pressure (and density) is higher at lower altitudes creating more drag which create more stress in the airframe. The air being more dense also causes the airplane to react more sensitively to pilot input making the airplane harder to control. High speed accentuates this. Also, there is usually more air turbulance at lower altitudes further increasing the difficulty of controlling the aircraft
 
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No, the speed of sound is quite relevant. Once the control surfaces stall, you lose control authority, and that is probably the true limit of controlled speed. The closer you get to Mach 1, the more likely this becomes.

Flight near the sound speed also produces much of the turbulence through Mach buffeting and the like.

As a result, a (diving) transport has a higher maximum ground speed a low altitude, not high altitude. For flat and level speed, the maximum speed is determined by inlet efficiency, and could go either way.

Sound speed, by the way, is basically a function of temperature alone. It's not very sensitive to pressure.
 
R.Mackey said:
No, the speed of sound is quite relevant. Once the control surfaces stall, you lose control authority, and that is probably the true limit of controlled speed. The closer you get to Mach 1, the more likely this becomes.

Flight near the sound speed also produces much of the turbulence through Mach buffeting and the like.

As a result, a (diving) transport has a higher maximum ground speed a low altitude, not high altitude. For flat and level speed, the maximum speed is determined by inlet efficiency, and could go either way.

Sound speed, by the way, is basically a function of temperature alone. It's not very sensitive to pressure.
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Um...aren't we talking about speeds ranging from 500-600 mph at 700 ft ASL?

The speed of sound is 761 mph at sea level so I don't see how it is relevant.
 
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