Helicopter flying through canyon - sideways?

I recently watched the new Jumanji: Welcome to the Jungle movie starring “The Rock”: https://www.imdb.com/title/tt2283362/?ref_=nv_sr_1

There is one CGI’d scene where the characters are in a helicopter flying through a vertical walled canyon. At one point the chopper pivots and flies forward with it’s main rotor blades perpendicular to the ground, i.e.: parallel to the vertical walls of the canyon.

I get they didn’t do that in reality, since the scene is obviously CGI’d but it did make me wonder if that was even possible.

So, is it possible for a helicopter to fly with its main rotors perpendicular ot the ground, in a canyon or not?

As a helicopter can fly sideways, it can in theory get some lift if its blades are perpendicular to the ground. I have doubts it could get enough lift though.

When I was in Hawaii, I took a helicopter ride over Kilauea volcano. At one point we were over a pool of red-hot lava, and since both of us in the right-hand seats were into photography, the pilot turned the helicopter on its side to give us better views. It was very hot through that little window, but I did get a great shot of the lava pool.

I don’t know how long the helicopter was on its side, probably around 10-15 seconds.

If you want to accelerate a helicopter in some direction - sideways, forward, backward - you need to tilt the helicopter a bit in that direction with the cyclic control. You also need to add some collective (i.e. increase the total thrust being provided by the main rotor) if you want to maintain your altitude; if you don’t, you’ll start to descend, since a small portion of the vertical force you had in level hover is now being directed horizontally.

if you want to accelerate hard in some direction, you tilt the helicopter a lot in that direction, and add a lot of collective. But you can only add so much collective, which means there’s a limit to how far you can tilt the helicopter before you are unable to prevent it from descending.

If you tilt a helicopter to 90 degrees so that its main rotor is in a vertical plane, then it’s not possible for it to exert a downward force against gravity at all; it will at that point behave like a thrown rock (albeit one with some control over horizontal movement).

So no, there is no helicopter that can sustain horizontal flight with its main rotor in a vertical plane.

Here’s a helicopter that gets pretty close to vertical shortly after liftoff; this is done deliberately to start a rapid descent down the mountainside.

Can you explain more what you mean by “on its side?” Was he perhaps in level forward flight, banking in a right-hand turn, causing the heli to lean to its right?

You can’t maintain the position for any sustained amount of time, but a helicopter is capable of pulling off a lot of weird flying angles temporarily. I think a lot of it is using momentum and lift generated in flight to roll the machine over and then recover, not actually generating lift from the weird position (sort of like how a diver will launch off the board from a stable platform and do a bunch of flips and spins while in free fall before hitting the pool below). Note that the helicopter in this video has been specially modified and your average pilot won’t be capable of doing a lot of those maneuvers.

Many off the shelf military helicopters can do loops and rolls. It depends on the type of rotor mast it has. In a helicopter with a non-rigid mast system like a Huey it’s good way to chop off your own tail.

But to be clear, there’s no good reason for this maneuver, outside of a military context of evading enemy fire or something. The pilot is showing off what’s possible.

Seems like a good way to quickly build up speed using hard-won gravitational potential energy instead of fuel.

And radio-controlled helicopters can do even more amazing stunts. It looks like it’s sustaining a vertical (nose up) attitude at one point, but I guess it’s alternating between a few degrees short of vertical and a few degrees past it.

A gentler maneuver achieves the same thing at a cost of a few seconds, with less stress on the machine and less vomit to clean up. Not that this was exceptionally high or low g or outside the limits for that aircraft, there’s nothing wrong with it. But the primary purpose was certainly to show off, not to save a few seconds.

Christ I’d be wearing a suit of armour if I were controlling one of those things… looks like a great way to turn your own face into chopped salad if you’re a tiny bit off on the controls.

Relatively recent fatality

There are probably other cases in the newspaper archives.

The helicopter was temporarily not moving, and positioned 90 degrees from its normal position. Those of us on the right side could look straight down at the lava pool by looking to our right. We were held in place by our seat belts.

It’s my understanding that any aircraft at all can do a barrel roll, if it starts with enough altitude to sacrifice.

This may have been a violation of Federal Aviation Regulations, which include this:

I imagine that, to a passenger in the helicopter, a bank of 60 degrees would feel like “we’re looking straight down”.

No doubt it felt like that, but this could only have been in forward motion (not hovering), in a steep banked turn to the right at much less than 90 degrees.

Think about how a helicopter moves.
You are hovering in place. play with the controls so the copter tilts forward, and it starts to move forward. If you didn’t give it more power (more collective for more blade “bite”) it would also start to go down. The “force vector” of the rotor blades is an angle, and the vertical component of the vector is what keeps the copter up, the horizontal component of the vector moves the copter in the forward direction.

At a certain angle, there is not enough vertical component to keep the copter at the same altitude and it will start to go downward. Of course, trying to gun it enough to stay up is probably also creating a massive forward push… say 45 degrees.

It’s pretty simple, actually - the rotor is a propeller pushing the copter (in general) in the direction perpendicular to the rotor, i.e. along the direction of the shaft. The same applies at any angle - The rotor is agnostic, it does not care which way the cockpit is pointed, just which way the controls are forcing it. Left, right, backwards, forwards - same idea.

It is impossible to maintain lift beyond a certain angle.

Many helicopter tricks, as mentioned, rely on momentum. Follow one of the links and watch a few more of YouTube helicopter tricks. There’s one where the helicopter goes vertical sideways. What it actually does - it’s going forward fast, then tilts and its path curves upward until it’s almost 90 degrees to the ground - then back down again. What it’s doing is using the momentum, much as if it was starting a loop. As it tilts sideways and goes up, the rotor is pushing against the forward momentum; when it runs out of forward momentum, it starts to fall back and the pilot controls it back from sideway to horizontal going in the other direction.

The only way to actually do the trick OP describes is to tilt the craft hard over onto its side while killing any collective/lift (so it doesn’t smash into the wall above the pilot’s head) then once through the gap, hopefully there was a hundred feet or two of room to fall until the craft is horizontal again. power is applied and it can get decent lift. While sideways, it’s a flying block of stuff and will simply fall downward. There is not vertical support. As with most truly lethal stunts, CGI is better provided it doesn’t look like Roadrunner cartoon physics.

Does it though? (We really need a SME like Johnny L.A. here for this. If you’re a helicopter pilot, I apologize.)

As a lay person, to me it’s conceivable that being in the mountains like that, the pilot’s lift margin of safety was not great. Therefore he wanted the helicopter out of ground effect and into a more predictable part of the flight envelope dominated by translational lift as soon as possible. I dunno. I’m not a helicopter pilot.

Low airspeed can also, depending on the local winds, which in the mountains can be quite severe, lead to ‘loss of tail rotor effectiveness’, which can be a problem for the type of pinnacle/ridgeline takeoff the pilot was trying to do. Then again, assuming the tail rotor was one that pushed the tail away from its disc, he was giving the helicopter max tail rotor, and it was enthusiastically pushing the tail away from the spinning rotor disc. I would think, in a truly high performance takeoff, that the pilot would want a near-neutral tail rotor, and let the main rotor torque do the work of pivoting the helicopter for the turn. Further, that would allow a larger portion of the engine’s power to go to the main rotor instead of having to also go to a fully pitched tail rotor.

Of course, the helicopter could be a type where the tail rotor acted to pull the tail towards the spinning tail rotor, in which case, the pilot was probably turning nearly as fast as he could.

I’m with Chronos on his statement about aircraft passengers being able to accurately note the degree of bank from their seats.

I haven’t responded to this thread because Machine Elf covered it pretty well. But ‘Speak of the devil, and his horns will appear.’ As far as the video…

Pretty much. They’re in the mountains. Even though it looks like a cold day, they might have been concerned with density altitude because of… well, their actual MSL altitude. A helicopter (or an airplane) can lift off while in ground effect, but may not be able to fly out of ground effect. Pointing the nose downhill and trading altitude for airspeed gets air over the rotor disc so that the aircraft can fly OGE.

Anecdote: I attended a screening of a Warren Miller film. Miller was there telling his stories to the audience. (I don’t remember if this was before or after the film.) He said he was on a mountain slope and people needed to be taken down. The helicopter could land and lift off because of ground effect, but it couldn’t take of and fly away. So they put a passenger in, and the pilot lifted off and ‘hopscotched’ IGE down the slope until he had enough empty space below him/in front of him to point the nose down and make the altitude/airspeed trade.