There is a lot of talk about the unreal precisionflying it would take to attack the Pentagon with a Boeing 757. Many claim that it would be impossible for a pilot with experience only from single engine Cessnas and a 757 simulator. In my experience the reported flying fits very well how an unexperienced pilot would behave.
First of all, if you claim that it would take enormous precision to fly like this, you take for a fact that the pilot intended to fly exactly like that. But do we know that? Wouldn't it have been easier to just point the nose down and krash in the middle of the pretty big target Pentagon makes from the air? Why make a 270 descending turn and aim for the wall? Why use that much harder approach?
I can very well imagine that a pilot with experience mainly from slow Cessnas would grossly underestimate the speed at which a jetplane travels and therefore overshoot the approach to the Pentagon. He then has to make a gentle descending turn, not banking to hard since he's unexperienced with the aircraft. Finally he almost comes in too low and struggles to keep the plane flying until he hits his target.
Some of you might wonder why I said "gentle descending turn" in that last paragraph. Most stories claim that he was basically spiralling down, almost going into a spin. Let's do some math to clear that up. First the data we need to work with. Here's a quote containing what most people, LCers or not, agree is correct:
Radar data shows Flight 77 crossing the Capitol Beltway and headed toward the Pentagon. However, the plane, flying more than 400 mph, is too high when it nears the Pentagon at 9:35 a.m., crossing the Pentagon at about 7,000 feet up. [CBS News, 9/21/2001; Boston Globe, 11/23/2001] The plane then makes a difficult high-speed descending turn. It makes a "downward spiral, turning almost a complete circle and dropping the last 7,000 feet in two-and-a-half minutes. The steep turn is so smooth, the sources say, it’s clear there [is] no fight for control going on."
Source:
http://www.cooperativeresearch.org/timeline.jsp?timeline=complete_911_timeline&day_of_9/11=aa77
1. To better understand speeds here in sweden I start by converting from miles per hour (mph) to meters per second (m/s). The highest speed I heard someone claim is 500 miles per hour so let's use that.
500 mph = 224 m/s (1 mph = 0.44704 m/s)
2. How far will you travel in 2.5 minutes, flying at 224 m/s.
224 m/s * 150 sek =33 600 m
3. What's the diameter of the 33 600 meter long circle you're flying in then?
Diameter = Circumference/pi = 33600/pi = 10695 m
Let's stop and think about this. The plane makes a turn on a circle with 10 km diameter. Isn't that very far from the spiralling stunttricks that some claim?
4. Rate of turn, ie. how many degrees per second is the plane turning and what is normal?
The plane turns 270 degrees in 2.5 minutes.
270 degrees / 150 sec = 1.8 degrees/sec
Searching google we find that a standard rate turn (yes, there is something like that) is 2-3 degrees per second. This means the plane banked less than what is normal. That leads to the conclusion that there were no high G-forces involved as some have claimed.
5. Rate of descent and what is standard? The plane descended 7000 feet in 150 sec.
7000 feet=2 134 m
2134m / 150 sek = 854 m/min
Recommended rate of descent at an airspeed of 130 m/s is 548 m/min which really doesn't matter. The airplane doesn't care if you fly upwards or downwards. Strain on the construction is caused by acceleration (change of velocity) and the only way to get that strain here would be to make a steep turn (which is not done as seen above). Max speed for Boeing 757 is 590 mph and that wasn't exceeded so we're ok here also (
http://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=252) .
In conclusion all values seem to be well within what the aircraft is built for and the rate of turn is even slower than standard. Very far from the dramatic stunt tricks that some claim. But why would some experienced pilots claim that these maneuvers are impossible? Well, if someone asked me if I thought that it was possible for a pilot like me to spiral down in high speed from 7000 feet, return to level flight a few meters above the ground and hit a ground target, I would also have to say I highly doubt that.