Quick question on 9/11 conspiracy

[lPeregrine]

A while back, I remember someone posting a refutation of the "the 9/11 hijackers were not professional pilots and could not have done what those planes did" argument, from a professional pilot. Now this has come up on another forum, and I can't find the original article. I know enough about the subject to tear the guy to shreds, but he's pulling appeals to authority and I want the expert's point of view to shut him up.

Does anyone know where this is? It was a pretty long article from an experienced commercial jet pilot which went over everything from navigation to the poorly flown visual approach and last-second turn to hit the building. Unfortunately, I have no idea where it was posted or what the author's name was.

[Sea Skimmer]

I don’t know anything about that article, but it would be well worth pointing out that Japanese pilots with as little as one month of training proved quite capable of hitting warships a fraction of the size of one of the towers. Those warships also happened to be moving and turning at 30knts while firing back with dozen or even a hundred plus anti aircraft guns.

[FSTargetDrone]

I don’t know anything about that article, but it would be well worth pointing out that Japanese pilots with as little as one month of training proved quite capable of hitting warships a fraction of the size of one of the towers. Those warships also happened to be moving and turning at 30knts while firing back with dozen or even a hundred plus anti aircraft guns.

And in some cases there were other aircraft up there trying to shoot down their Japanese planes on the way to the target, or near it.

The hijackers didn't even need to know how to pilot the airliners off of the ground and navigate away from the airport, which is what the Japanese had to do (excluding Ohka attacks). The hijackers took over in the air after the aircraft were well underway.

[Broomstick]

A while back, I remember someone posting a refutation of the "the 9/11 hijackers were not professional pilots and could not have done what those planes did" argument

Which is a weird argument, given that at least one of them held a commercial pilot's license and several had had time in professional-level airline simulators (used to be just anyone could rent time in one for several bucks an hour).

I don't know where the meme "these guys weren't real pilots" got started - they most certainly were.

[lPeregrine]

A while back, I remember someone posting a refutation of the "the 9/11 hijackers were not professional pilots and could not have done what those planes did" argument

Which is a weird argument, given that at least one of them held a commercial pilot's license and several had had time in professional-level airline simulators (used to be just anyone could rent time in one for several bucks an hour).

I don't know where the meme "these guys weren't real pilots" got started - they most certainly were.

Exactly. The argument is incredibly stupid, and anyone with even basic research can see the problem (sharp turns = visual approach by inexperienced pilot who almost missed the target). But he's pulling out the "you aren't a veteran pilot like MY source" argument, so I'm trying to find the experienced pilot's detailed dissection of that idiocy.

You might be amused to hear that his "30,000 hour pilot" quoted on these conspiracy sites is claiming that the hijackers needed to be expert pilots to make the "5-7 G turns observed in the attacks". Now, correct me if I'm wrong here, but isn't taking a 757 into a 5-7 G turn well into "rip the wings off the plane" territory?

[Broomstick]

Don't quote me on this....

... but a quick search gives a +g limit of 2.5 for the B757. Airplanes are supposedly built with a minimum %150 factor on the top g limit before structural failures start to occur. That does not mean that at +3.75g the wings fall off - it means that's the point you start to get permanent deformation of the machine's structures. It's possible it could fold up, but you usually have to go way over the limit.

Would 5g, twice the rated g limit, be enough to "snap the wings off"? Possible... 7 g definitely raises the possibility. For some reason Boeing is cagey about publishing the exact failure limit. However, most people tend to pass out around 4-5g. Even without the wings snapping off, the result of a high g maneuver can be a crash because the pilot is unconscious. So, you might get one such turn out of a typical airplane, but not several.

(Aerobatic pilots can train themselves to withstand higher g's than average, and fighter pilots use a g-suit - these are exceptions to the rule and so far as I know the 9/11 guys were neither aerobats nor did they have g-suits)

That said, the turns visible on video prior to the crashes were NOT "high g" to that extent. Yes, they were sharp, but to pull even 3 g's you need a 70 degree bank - the wings would look more vertical/knife edge than horizontal if they were pulling g's like that. From what I recall of the radar tracks, there weren't any turns sharp enough to generate that level of g force, either.

[lPeregrine]

Thanks, that clarifies things a bit. That's about what I thought... "rip the wings off" was mostly to highlight just how far beyond the design limits a 7 G turn would be, but it's good to know that's not too far off.


Two questions though, since you have far more flying experience/knowledge than I do:

1) Am I correct in assuming that pilot skill has little, if anything, to do with surviving a turn like that? As far as I can see, the most a pilot could do to increase his chances of surviving a 7 G turn would be praying for divine intervention. This was his "expert"'s major point, that an expert pilot (rather than good engineering design) would be required to make a 5-7 G turn in a 757.

2) Just what kind of stall characteristics would be involved in something like those final turns? Aside from his "expert" claiming that high speed alone could cause a stall (poor wording, perhaps), he also claims that the final turns would be done too close to the stalling point for an inexperienced pilot to manage without losing control. Oddly, his "expert" says this in reference to high-speed stalls, which contradicts my understanding that low speed produces the greatest risk of stalling.

[DavidEC]

Someone needs to ask the pilot how a commercial airliner is even capable of sustained 5-7Gs. In addition, wouldn't the passengers making phone calls contradict this? The majority of untrained civilians would pass out.

[Azazal]

Someone needs to ask the pilot how a commercial airliner is even capable of sustained 5-7Gs. In addition, wouldn't the passengers making phone calls contradict this? The majority of untrained civilians would pass out.

CT MODE Dude!! The planes were remote controlled and the phone calls were faked!! END IDIO.. I mean CT MODE

[Sea Skimmer]

From what I recall of the radar tracks, there weren't any turns sharp enough to generate that level of g force, either.

The radar tracks do however show the planes general courses as having been very ‘weavy’ if that makes any sense, they couldn’t hold the exact heading they wanted and kept turning back and overcorrecting… exactly the kind of behavior you’d expect from an inexperienced but trained pilot.

Here is a not that great image of one of the flight paths; sure doesn't look like they did anything radical to me.

[DavidEC]

CT MODE Dude!! The planes were remote controlled and the phone calls were faked!! END IDIO.. I mean CT MODE

Oh, I forgot. Apparently the supposed passengers are being held in a big alien spaceship under Antarctica.

[Molyneux]

From what I recall of the radar tracks, there weren't any turns sharp enough to generate that level of g force, either.

The radar tracks do however show the planes general courses as having been very ‘weavy’ if that makes any sense, they couldn’t hold the exact heading they wanted and kept turning back and overcorrecting… exactly the kind of behavior you’d expect from an inexperienced but trained pilot.

Here is a not that great image of one of the flight paths; sure doesn't look like they did anything radical to me.

That link takes you to the front page.

[Broomstick]

1) Am I correct in assuming that pilot skill has little, if anything, to do with surviving a turn like that? As far as I can see, the most a pilot could do to increase his chances of surviving a 7 G turn would be praying for divine intervention. This was his "expert"'s major point, that an expert pilot (rather than good engineering design) would be required to make a 5-7 G turn in a 757.

Well, one thing you can do is tighten your legs muscles and your gut like you're straining to squeeze out a turd - this tends to force the blood from your lower body into your upper, as well as increase blood pressure. Might be a little hard to concentrate on that AND pray at the same time, but it's probably possible, particularly under life-and-death circumstances. This maneuver is not a secret and is taught to Air Force and Navy pilots whose normal flying requires high g's. Civilian pilots try to avoid such situations, but a lot of us are at least aware of the technique, even if we don't practice it, and in a pinch might well make use of it. How much this will increase your resistance to high g's I don't know, but it does have that effect. It might enable a normal human to withstand 5 g's - 7 would be kind of dicey.

Let's see - does it take "expert" flight skills to get through a high g maneuver? Hmm... no, I'd expect it would mostly take a strong heart, to keep the blood pumping up your neck and into your skull. Also, holding the controls in position could become challenging as not only your arms now weigh 5-7 times what they normally do, but the controls themselves do, too. So, instead of moving something with (wild ass guess) a kilo or two of mass and a required force of 5 kg you're now moving something weighing 10-14 kilos with the equivalent of a large ham or two strapped to each arm. Doing things with finesse becomes more difficult, but that's about it. The mechanics of such a turn don't really change - when doing routine 2g maneuvers I always found dealing with my bodily discomforts (high g forces can also affect your perception of ascent/descent/level flight as well as balance, not to mention the way your appendages drag on the rest of your body in a way they don't normally do so) more of a challenge than maintaining the turn. Granted, I don't fly at 4+ g's, but I know people who do and they assure me that the mechanics of such maneuvers don't radically change from lower g maneuvers.

2) Just what kind of stall characteristics would be involved in something like those final turns?

Nothing unusual, although the "break", the point at which the stall occurs, is likely to be more abrupt and any unwanted/undesirable flight effects might occur more quickly and with greater force. For example, entering a spin might be a LOT more exciting from a 5 g turn than a 1.5 g turn, but the fundamental phenomena will be the same. Such a thing would be considered an accelerated stall if I properly recall my terminology (it's been awhile since I studied such phenomena), but from my limited experience of entering stalls at higher speeds than usual in practice situations it's the same damn thing as at slower speeds. The human involved might have some issues about it (then do tend to be more alarming than slower-speed stalls) but the airplane doesn't as long as you don't exceed design limitation either during the maneuver or during the subsequent recovery.

Aside from his "expert" claiming that high speed alone could cause a stall (poor wording, perhaps)

VERY poor wording, so poor it makes me think there is a lack of understanding of concept.

Stalls occur when you exceed the maximum angle of attack. That's it. Speed has little to nothing to do with it. You can exceed the angle of attack at low speed, high speed, any speed. If you recall the initial sub-orbital flight of Rutan's SpaceShipOne, at a certain point near the peak of it's ascent it started rotating on its axis. That's because Mike Melville had exceed the angle of attack on the wings and it was in a genuine spin - despite the fact it was still accelerating away from the Earth, that is, going up (aren't rockets fun?). On his second flight, going just as fast, he didn't spin because he didn't exceed that angle of attack. It wasn't the speed that spun it, it was the angle of attack.

Which also, by the way, proves that you can stall an aircraft at supersonic speeds AND recover safely.

Likewise, while practicing stalls and learning about them, I was able to demonstrate that you can quite easily stall an airplane in a descent, whether at cruising speeds or at low speeds.

Part of the misunderstanding is that the experience of most pilots, including civilian airline pilots, is of stalls at low speeds. This is the standard way to practice them because it means the maneuver is less forceful (I'd say violent but the emotional baggage on the term isn't appropriate) and, because recovery tends to be sooner, allows for practicing them at a lower altitude. Myself, I practice stalls high enough to allow for recovering of an accidental spin - a minimum of 3,000 feet or about 1,000 meters in a tame, docile aircraft with potential for quick recovery. Some general aviation airplanes would, for safety, require 3-4 times that. These days, stalls are not practiced in airliners, for that type of aircraft they are practiced in simulators, but back pre-1970's they certainly did do stalls in airliners as part of training (in passenger-free airliners - doing so wasn't cheap, when you consider the costs of running an empty 7x7 or Airbus and such cost is a major reason it's all simulator based now) and minimum altitudes were at least 20,000 feet, or well over 3,000 meters and even then I'm not sure you'd be able to recover from spinning one - but by that level your stalls should never lapse into accidental spins anyway. (I once asked an Airbus pilot about spin recovery in his airplane. He thought about it, but expressed doubt you could get the airplane high enough in the first place to have enough altitude to recover, although it's theoretically possible. You'd almost certainly break the sound barrier on the initial descent, but as long as the controls didn't lock up due to aerodynamic forces acting on them you should be able to control it - it's just that if you're headed towards the ground at Mach 1+ you need a LOT of room to recover/slow down)

But although speed could screw up your recovery options (too little altitude, controls locking up in the airstream) it is in no way a primary cause of a spin.

Stalls (spins being a sub-set of stalls) are caused by exceeding the critical angle of attack of the wing. That's it.

He also claims that the final turns would be done too close to the stalling point for an inexperienced pilot to manage without losing control.

Well, that's about 50% horseshit.

In order to get my license I had to demonstrate an ability to fly and maneuver the airplane at just above a stall for several minutes. It's a basic skill for even a minimal license (and remember, the 9/11 hijackers had more than the minimum skill/experience to get a private license, as demonstrated by Mr. Atta holding a commercial license). This does require a certain finesse as your control response isn't so wonderful. As I pointed out, your finesse suffers at higher g's due to increased weight. Maintaining an extended turn at such g's would be problematic - but since I doubt the Boeings used on 9/11 had the engine power to maintain level flight in a high g turn you won't be experiencing such circumstances for long. You'd be swinging through those turns on momentum, not engine power.

OK, a bit about lift and weight. Lift is what holds you up (hence the name) and there is a definite relationship between lift, speed, and angle of attack (AoA). You can increase lift by going faster, by increasing AoA, or both. However, there are limits - too much AoA you stall. Too much speed you run into problem with controls or structural limits (yes, you can "rip the wings off" by going too fast). There is also a relationship between weight and lift - the more weight, the more lift required. A fully loaded airplane needs a higher speed to take off (and hence a longer take off roll to get up to the required speed) and a higher AoA for the same in-flight speed. In order to maintain a high g turn you need speed AND AoA because g is a measure of a weight and as weight/g's go up you need more lift. If you don't maintain sufficient quantities of both either you will lose altitude (not enough airspeed while maintaining flyable AoA), or you'll stall (increasing AoA to maintain lift to compensate for what you're not getting from airspeed) Stall speed is said to go up as weight increases not because the airspeed causes the stall, but because there is a relationship between AoA and airspeed such that your airspeed can be used to give you information about your AoA.

As an example (which should be taken with a grain of salt as this will not scale up precisely for airliners), in the Cessnas and Pipers I trained in for my license I'd routinely demonstrate 2 g turns (the highest they are certified for, although they are capable of doing more in an emergency). At full power, a fully loaded Cessna 150 maintains level flight (barely - don't do this on a hot, humid day or at high altitudes) in a 2 g turn at around 88-90 mph airspeed. It would stall at around 83-85 mph. That's pretty darn close. This is considered within the capability of even student pilots. I was able to do this before I was deemed competent to solo.

Oddly, his "expert" says this in reference to high-speed stalls, which contradicts my understanding that low speed produces the greatest risk of stalling.

Speed has little to nothing to do with - it's angle of attack that causes stalls, not speed, either lack or excess of it.

Pilots are cautioned against low-speed stalls, and practice preventing them, for the simple reason that they are significant cause of landing accidents. When landing you're slowing down AND increasing your AoA in preparation to touchdown - the lift you are no longer generating by high airspeed must come from increased AoA. This puts you much closer to a stall than you would be at cruise, or even take off (another time you use higher AoA, in order to get the hell away from the ground quickly). It's because the pilot is edging towards high AoA during a normal landing that there is reason for caution and practice to avoid bad outcomes. But this isn't rocket science. When I fly tailwheel airplanes the goal is to deliberately stall the airplane about a handwidth above the runway. Every time. It's how you land them. Tricycle gear airplanes - including modern airliners - usually land a little further away from stall, but not much. For short airfields, you can land those at stall speeds, too, just like a tailwheel.

Bottom line, pilots routinely fly at high AoA/near stall. It's not a big deal in competent hands.

Now, psychological factors can be important. The discomfort/pain of high g maneuvers can be distracting, and the flight attitudes required to achieve a high g turn can be disorienting or even frightening. These could cause the pilot to lose control and crash. HOWEVER - the airplane doesn't care (unless you exceed structural limits). But on 9/11 the pilots didn't lose control. They weren't exactly neat and polished on the maneuvers, but they didn't lose control.

[Broomstick]

Someone needs to ask the pilot how a commercial airliner is even capable of sustained 5-7Gs.

I don't think they have the engine power to maintain it, but I don't know for sure, that's another WAG.

In addition, wouldn't the passengers making phone calls contradict this? The majority of untrained civilians would pass out.

A very good point!

[DavidEC]

I don't think they have the engine power to maintain it, but I don't know for sure, that's another WAG.

What I'm thinking is, are their control surfaces even large enough, and can they deflect enough?

A very good point!

Er... I'm not sure how to take this.

[Broomstick]

I don't think they have the engine power to maintain it, but I don't know for sure, that's another WAG.

What I'm thinking is, are their control surfaces even large enough, and can they deflect enough?

I don't know. Nor do I have the information or knowledge base to give a good answer to that question, but I will state that the higher the airspeed the proportionally smaller control surfaces you need. I suspect engine power is the critical factor in maintaining sustained g loads in such an airplane, but I can't confirm it.

A very good point!

Er... I'm not sure how to take this.

It's more proof that there weren't high g maneuvers involved.

[DavidEC]

I don't know. Nor do I have the information or knowledge base to give a good answer to that question, but I will state that the higher the airspeed the proportionally smaller control surfaces you need. I suspect engine power is the critical factor in maintaining sustained g loads in such an airplane, but I can't confirm it.

I suspect you can compare the theoretical max G-loads of fighter aircraft nowadays - 12 G for a Flanker series IIRC - and compare the size of their rear elevators in proportion to the whole aircraft, and its mass, and compare that against the size of the control surfaces of airliners, versus their whole size and mass. Fighters are designed for tight turns and high speed; airliners, high cargo and long range.

The whole elevator on a modern supersonic fighter moves as a control surface IIRC (something to do with supersonic aerodynamics), that's why I refer to the elevators on a fighter versus just the control surfaces on an airliner.

It's more proof that there weren't high g maneuvers involved.

Alright, I just had a false positive on the ol' sarcasm detector, that's all.

[Broomstick]

The whole elevator on a modern supersonic fighter moves as a control surface IIRC (something to do with supersonic aerodynamics), that's why I refer to the elevators on a fighter versus just the control surfaces on an airliner.

That control surface - where the entire horizontal surface of the tail moves and not just a hinged portion - is used on airliners and is even present in the Piper Cherokee line, which are very, very basic 4-seat trainers. While that sort of "stabilator" is most needed for supersonic flight there's actually no reason you can't use it while flying slower.

[DavidEC]

Aha, schooled. Still, the 757 doesn't look like it has them from photos.

[lPeregrine]

VERY poor wording, so poor it makes me think there is a lack of understanding of concept.

Yeah... that was the strong hint that the supposed "expert" was just bluffing his way through. This "expert" really looked like he was claiming that just reaching sufficient speed (even in level, zero AoA flight) would stall the plane. And even worse, that getting a plane to exceed the maximum (safe) speed required any kind of skill beyond "full power dive and pray you don't go too far over".

Thanks for confirming all of that... his statements seemed way too mistaken to attribute to poor wording, especially for someone who is also claiming 30,000 hours in the relevant airplane. But since I won't start on my serious aerodynamics courses until the spring, I wasn't sure if I might somehow be missing something.


Unfortunately, the troll has run away in shame, saying "you have good points... but MY expert still makes me question the official story. Why don't you go debate him, instead of arguing with someone uninformed like me?". Pathetic, but he's got a pattern of doing this... and I'll remember this thread.