There are real difficulties involved with flying an aircraft in an enclosed space. During flight, an aircraft pushes air out of the way and generates lift. Any time the air cannot move out the way (like in an enclosed space) pressure builds up round the plane and lift decreases, as well as control. This scene from Octopussy has James Bond flying an Acrostar jet through a hanger - this was a real stunt performed by Corkey Fornof and had to be planned and executed very carefully.
So Ultralights and Helicopters (which have different flying characteristics) are ok in enclosed spaces, but finding a plane that can fly in such a space is much more difficult.
Presumably the “real stunt” part of that was the footage of the plane going into the building and then the external shot of it emerging from the other side (where the gap between the doors is far larger than it appeared from the interior shot).
But if you pause the video at 1:39, during the scene where the plane is actually flying inside the building, you can clearly see that it is mounted on a vertical metal post that moves along the floor of the hangar.
Edit: you can also see it on the first part of the interior scene, at 1:35.
Yeah, I doubt they could have people in the hanger as the plane goes through - if (as another comment on the stunt I read suggests) they were worried about the pressure wave blowing out the windows of the hanger, they couldn’t have people in there to be blown out as well.
They must have done the external shots for real, then mocked up the internal and cockpit shots with a motorised post.
The landing to fill up at the end was based on an incident experienced by Fornof when he had to emergency land between vehicles on a freeway then coasted off at an exit and down to a gas station.
Another great Bond stunt by Fornof was the falling plane caught by a skydiving Bond in Goldeneye - the particular plane used could reverse the prop, so the falling plane was retarded enough that a freefall skydiver could catch up.
Not an aerodynamicist—hell, I can barely spell it—but one difference between ground effect and the enclosed space situation might be that in ground effect, pressure is only building up beneath the wing, while in the enclosed space, pressure will be building up both below the wing and above the wing (due to the roof and walls.)
No idea if this actually happens in practice, but it is a potential difference that came to mind, in the situations you described. Akin to the recent thread on earthquakes and caves, I wonder how small the enclosed space has to be, relative to the wingspan and speed of the a/c, before the upper surface of the wing ‘notices’ a pressure increase from the walls and ceiling?
This is another way of saying that it’s like flying at a somewhat lower altitude - which is actually easier (requires less power).
The increase in pressure in an enclosed space actually large enough to allow flying would be awfully small. Consider that flight in the Seattle Kingdome:
Assumed weight of aircraft and pilot: 500 lbs
Assumed interior dimensions of Kingdome: 500’ diameter x 100’ high
Volume of air in Kingdome: 3.9 * 10[sup]7[/sup] cubic feet
Approximate air density: 0.072 lb/ft[sup]3[/sup]
Weight of air in Kingdome: 2.8 * 10[sup]6[/sup] lbs
Increase due to adding the weight of the aircraft: about 1 part in 5,600
Maybe if the space was large enough, and the aircraft slow enough, it could be done. But even then, the pressure feedback would probably be inconsistent, adding to the aircraft control issues as walls and ceilings were approached.
I didn’t dispute that an ultralight could fly in the Kingdome or similar space - my point is that there are sound aerodynamic reasons that larger and faster aircraft generally won’t attempt similar things, even in a larger space.
As for Ultralights - they have low stall speed (under 45 knots, generally), large control surfaces, and low weight. In many jurisdictions they do not require certification, and some classes do not require any sort of pilot licensing. They do not always have 3-axis control, many rely on the pilot weight-shifting assisting the control, and are often classed as powered gliders. They are a completely different class of flying machine to general aviation aircraft, and the regulations round the world (where specific regulations apply) reflect that.
I think the sound reasons have a lot to do with an absence of spaces that are large enough. I see no aerodynamic reason why a larger aircraft in an appropriately larger space could not fly indoors.
Note that the linked article about flying through the hangar discussed the issue of a maximum speed, but also suggested that below this speed things would work fine (as indeed they did). Also note that this hangar was a small fraction of the size of an indoor space that would allow extended flight (which basically means large enough to allow takeoff, 360-degree turns, and landing).
They are often subject to different aviation regulations, but always to just the same laws of physics.
It could have been done. But it wouldn’t be practical to spew all that jet exhaust into and enclosed space. Perhaps in the development of the aircraft it might have been done. But in general it’s dangerous. An accident could result in an enormous fire.
It’s difficult to fly anything but very small aircraft in an enclosed space. Aircraft aren’t cars, they need a lot of elbow room to account for sudden changes in air speed or pressure around them. A plane slipping 50 feet in open air is nothing. Inside an enclosed space it’s easily a crash.
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Maybe if the space was large enough, and the aircraft slow enough, it could be done.
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I just accept that there would be additional risks involved.
The article mentioned an airspeed window, indicating that there was also a lower limit to the speed, due to the increased drag caused by the raising pressure slowing the aircraft down, and the requirements to maintain altitude while flying wings vertical.
Some of those physical laws are non-linear, meaning the space can’t just be scaled up relative to the size of the plane, and a boundary condition that does not affect an ultralight flying at 45 knots may have a significant impact on a heavier aircraft flying twice that speed. If you don’t believe that, explain why the wing of a high-speed aircraft is so different to one of a low speed aircraft - same laws of physics, but entirely different operating conditions and design.