Factual error: A tank's main gun could not blast Iron Man out of the sky, as depicted in this film, and the "lucky shot" theory holds no water. In military history, there are only a couple of instances of tanks using their main guns to shoot down aircraft by chance, and those involved tanks repeatedly firing their main guns on known flight paths until an aircraft literally ran into a tank round. However, in this movie, Iron Man comes out of nowhere on no known flight path, he's not recognizable as an aircraft, he's traveling at hundreds of miles per hour, and he's only airborne for about 4 seconds before he's hit with a tank round. The tank gunner could not possibly identify Iron Man as a new target, elevate the main gun, track him and fire in 4 seconds. Modern tanks do not have the ability to acquire and track fast-moving targets with the main gun, nevermind fast-moving aerial targets.
Suggested correction: All that might be true in the real world but in this movie we know that the forces of the Ten Rings have been supplied with advanced weapons from Stark Industries. A retrofitted tank weapon that can engage a superhero in a flying suit is no more fanciful than a hand held paralyzing noise device or an arc reactor.
Yes, it's a fantasy film. You could even fairly say that no fantasy film can be in error by virtue of its fantastical premise. That does not negate a factual error.
Tony Stark is an extremely intelligent inventor that makes advanced weapons for the military. A targeting system for made for tanks lies entirely within the realm of possibility presented within the world of this franchise.
And, yet, it is established in this first movie that the Ten Rings terrorists only possess as much Stark technology as Obediah Stane allows them (which isn't much). Obviously, the tank is not very advanced technology, as Tony merely sidesteps the second tank round and he utterly destroys the tank with a wrist-rocket. There is no indication in the film that the Tank is advanced Stark technology.
No one is saying that the tank itself is Stark technology, only that it's weapon can be retrofitted with a targeting system. It wouldn't be much different than retrofitting an older model car with a GPS system. The reason Iron Man is able to sidestep the second shot is because he's expecting it, and even then, he barely dodges it.
No way the single-shot main gun of ANY style tank would be "retrofitted" to track and fire on high-speed aerial targets. Any refit would require rebuilding and automating the tank and turret and replacing the main gun (which fires only single rounds) with an automatic repeating cannon, essentially turning it into an advanced mobile anti-aircraft platform. The tank in the movie is recognizable as a standard, slow, single-shot British Chieftain MK10, so it's not Stark industries.
Well you definitely know a hell of a lot more about tanks than I do, so I concede my previous points.
It takes a man to admit he's wrong. I doff my cap to your courage.
