Jumping out of a crashing helicopter

Mr_Roger_Bongos · 27-08-2012 01:05PM #1

This is totally random i realise, but was watching a film the other night where a helicopter had rotor failure of some variety (they were still spinning just slower).

My question - If you had a parachute and you jumped out as the helicopter was falling towards the ground, would you get caught up in the blades/rotor?!

Assuming mass of helicopter * gravity = the helicopter falling faster than you jumping out!

/cue abuse

haulagebasher · 27-08-2012 01:13PM

Mass * 9.81 will give you the weight, not the acceleration. Acceleration is W/M so given that the relationship between mass and weight between person and helicopter is the same, both should fall at the same rate. Drag ignored.
Go back to school. Your Cletus Spuckler like avatar is particularly apt for your OP.

Anyway, I don't imagine that it would be completely impossoble to survive a failed helicopter by bailing out with a chute but I would say your chances you be slim enough.

seven_eleven · 27-08-2012 01:31PM

haulagebasher wrote: »

Mass * 9.81 will give you the weight, not the acceleration. Acceleration is W/M so given that the relationship between mass and weight between person and helicopter is the same, both should fall at the same rate. Drag ignored.
Go back to school. Your Cletus Spuckler like avatar is particularly apt for your OP.

Ah jaysus. I dont recall being taught this stuff in school.

Jesus Nut · 27-08-2012 01:57PM

I have a freind from Limerick who has had to do just that on one occasion!
It was in a Robinson R44 helicopter that had an engine failure and him and the other lad jumped out of the machine before it impacted the water (Very risky but the decision paid of and they were both grand).

I have often had same ideas.. I think if I was over water I would always jump out a few feet above the water and get my self into pencil dive position ASAP.

Over the ground, I think one would only jump out of a fallen aircraft if they had a chute!

Mr_Roger_Bongos · 27-08-2012 02:10PM

haulagebasher wrote: »

Mass * 9.81 will give you the weight, not the acceleration. Acceleration is W/M so given that the relationship between mass and weight between person and helicopter is the same, both should fall at the same rate. Drag ignored.
Go back to school. Your Cletus Spuckler like avatar is particularly apt for your OP.

Anyway, I don't imagine that it would be completely impossoble to survive a failed helicopter by bailing out with a chute but I would say your chances you be slim enough.

Thanks for clearing that up, pity you were such an arse about it.

Su Campu · 27-08-2012 04:52PM

Everything falls at an ititial acceleration of 9.81 m/s - choppers and feathers - until terminal velocity is reached. So unless the chopper is still generating some sort of lift then you will not be able to outfall it unless you can achieve a higher terminal velocity than it by nosediving like hell!!

27-08-2012 04:57PM

Assuming that you can actually get a place to propel yourself from (i.e., you're not weightless and away from the walls), all you need to do is push off and away from the helicopter. Once the rotor is no longer above you, deploy the parachute

Stovepipe · 27-08-2012 08:18PM

Russian helicopter crews have used parachutes to bail out of Mi8 and Mi24 helicopters in Afghanistan and various other wars.

regards
Stovepipe

Run_to_da_hills · 27-08-2012 08:19PM

You would have to try and tilt it sideways to avoid the blades.

bluecode · 28-08-2012 12:07PM

Considering how low helicopters operate as a routine and considering that most helicopter accidents seem to involve the pilot hitting something near the ground. Then a parachute is rather pointless. Might be useful for a military pilot as Stovepipe pointed out.

Modern pilot's emergency chutes open very quickly indeed but you have to consider unbuckling yourself and getting out the door in a wildly spinning aircraft. Well I suppose it would give you something to do on the way down.:eek:

Dacian · 28-08-2012 12:26PM

Stovepipe wrote: »

Russian helicopter crews have used parachutes to bail out of Mi8 and Mi24 helicopters in Afghanistan and various other wars....

The latest Russian attack helicopters (KA-50/KA-52) are equipped with ejection seats, explosive charges disconnect the blades before the rocket booster ejects the pilots.

Skyknight · 28-08-2012 12:51PM

As far I know the standard procedure is to auto-rotate to a controlled impact, whether over land or water, and in doing so reducing (if only slightly) the rate of impact. This allows the still turning blades to provide lift(though drastically diminished),reducing the force of the impact, on both the main structure and and on its occupants. Most of the additional energy would, be absorbed though the skids or landing gear(in the case of the Eurocopter Tiger and AH-64), thus increasing ones chances of survival, and reduce injury. I understand that when it is executed properly its very effective from both high and medium altitudes. I think the Ka-50/52(thanks for the correction, Dacian) is one of only a few helos that have explosive bolts that sheer the main blades, thus allowing for the crew to be extracted by ejection seat. A I would therefore assume that, despite what one might think(or instinctively want to do), it is always best to stick with the machine and Auto rotate it to a controlled impact.
Slightly OT, from what I remember, in the 80's,the RAF ran a recruitment commercial, in which the pilots were being trained to get out of a capsized helicopter.

Just my five cents,
Skyknight

Chuck Stone · 28-08-2012 01:31PM

Related. Landing with no engine power.

https://www.youtube.com/watch?v=3fKtKy-FIfo

Zulu · 28-08-2012 01:36PM

The blades "push the air down", not "suck it up", so you'd be grand.*

*T&C's apply

Run_to_da_hills · 28-08-2012 03:43PM

Zulu wrote: »

The blades "push the air down", not "suck it up", so you'd be grand.*

*T&C's apply

That's only if its powered up but if its auto gyring?

Growler!!! · 28-08-2012 03:53PM

You can jump out of a working heli no bother...

http://m.youtube.com/#/watch?v=bV7ccOdonCo

Zulu · 29-08-2012 07:08AM

Run_to_da_hills wrote: »

That's only if its powered up but if its auto gyring?

Same, but not as much power. Also, consider the following: the helicopter is more massive & creates far more air resistance, thus would have a lower terminal velocity (although you'd be feiced were you to be relying on that).
And helicopters can glide (somewhat) when the rotors are free to move (not locked).

lomb · 30-08-2012 05:04AM

There is absolutely no problem bailing out of a heli, skydivers do it all the time.
Also autorotation without power is a standard manoeuvre and if executed properly has a very good chance of working.
Whats scary is all the choppers you see at night flying about-even if some are twin turbine I cannot see how a forced landing is possible at night with limited visibility. You couldnt pay me to go up in one at night.

bluecode · 30-08-2012 12:14PM

Yes a forced landing at night would not pleasant. But the only helicopters flying at night are either military or coastguard in Ireland. They either have night vision equipment or spotlights. So they can see what they're about to hit. Civilian choppers don't fly at night here unless they are equipped for it, which is rare if not unheard of.

EI-DOR · 01-09-2012 03:51PM

It was in a Robinson R44 helicopter that had an engine failure and him and the other lad jumped out of the machine before it impacted the water (Very risky but the decision paid of and they were both grand).

They jumped out because it had an Engine Failure?! Mother of god. Your friend shouldn't be let loose in a Helicopter. Every Helicopter Pilot is trained to Auto-Rotate the machine to the ground / water in the event of an engine failure. If he was flying over water the R44 should have been equipped with floatation devices or the PIC should of had a life-vest on.

The survivability will be much greater if you carry out the auto-rotation correctly the whole way to the ground. Plus you can save the machine at the same time. Engine failures are the least of your worries when Piloting Helicopters. Tail Rotor failures can be a different story. They also require the Pilot to auto-rotate to the ground but only with more airspeed to keep the airframe stabilized until touch-down.

There is absolutely no problem bailing out of a heli, skydivers do it all the time.

That is different. Skydivers use Professional Companies with experienced pilots to take them to a high altitude. The aircraft will be close to a hover or moving forward at slow speed before they disembark.

Stinicker · 02-09-2012 01:35PM

Don't helicopters have ejector seats anyway!

Mr Benevolent · 02-09-2012 01:41PM

Zulu wrote: »

The blades "push the air down", not "suck it up", so you'd be grand.*

*T&C's apply

That's like saying planes fly by pushing the air down. That's not correct.

The blades suck up to fly. Air being pushed down only comes into the equation during a heli landing.

Su Campu · 02-09-2012 04:35PM

Confab wrote: »

Zulu wrote: »

The blades "push the air down", not "suck it up", so you'd be grand.*

*T&C's apply

That's like saying planes fly by pushing the air down. That's not correct.

The blades suck up to fly. Air being pushed down only comes into the equation during a heli landing.

Are you for real? Both helis and planes get their lift through the vertical force of the angle of attack of the blades/wings on the relative airflow. The surfaces exert a downward force on the air, which returns an equal and opposite (upward) force....lift. It's like driving along in a car with your hand flat out the window. Tilt it upward slightly and it lifts, like a wing. Contrary to what is generally taught, the curved upper surface of the blades/wings only aid in retaining laminar flow, and while this flow induces a lower pressure above through the Bernoulli equation, this pressure difference is not enough to provide the lift required.

Zulu · 03-09-2012 06:21AM

Confab wrote: »

That's not correct.

What is not correct is your post, and possibly your grasp of physics.
A wing works by creating a higher air pressure below it that above it, thus life is achieved. How is the higher air pressure achieved under the wing?

As Su Campu said, put your hand out the window of a moving air. Tilt the angle of the hand upwards at the front and air is forced under the hand creating a higher air pressure under the hand, and this in turn lifts the hand. Air is essentially being forced from "up" to "down". This same airflow will force you down if you are below the wing/rotor.

It will not suck you up.

St. Leibowitz · 03-09-2012 12:30PM

http://www.youtube.com/watch?v=3F2k-GWKW-w

Watch the guys who jumps (or falls) out of this helo. He survived, but it wasn't wasn't pleasent. He would've been safer inside ... maybe.

Mr Benevolent · 03-09-2012 07:11PM

Zulu wrote: »

What is not correct is your post, and possibly your grasp of physics.
A wing works by creating a higher air pressure below it that above it, thus life is achieved. How is the higher air pressure achieved under the wing?

As Su Campu said, put your hand out the window of a moving air. Tilt the angle of the hand upwards at the front and air is forced under the hand creating a higher air pressure under the hand, and this in turn lifts the hand. Air is essentially being forced from "up" to "down". This same airflow will force you down if you are below the wing/rotor.

It will not suck you up.

Why the 'Skipping Stone' theory is wrong

There are many theories of how lift is generated. Unfortunately, many of the theories found in encyclopedias, on web sites, and even in some textbooks are incorrect, causing unnecessary confusion for students.

The theory described on this slide is often seen on web sites and in popular literature. The theory is based on the idea that lift is the reaction force to air molecules striking the bottom of the airfoil as it moves through the air. Because this is similar to the way in which a flat rock thrown at a shallow angle skips across a body of water, it is called the "Skipping Stone" theory of lift. It is sometimes called a Newtonian theory of lift, since it involves Newton's third law, but to avoid confusion with the correct Newtonian theory of flow turning, we shall call it the "Skipping Stone" theory.

This theory is concerned with only the interaction of the lower surface of the moving object and the air. It assumes that all of the flow turning (and therefore all the lift) is produced by the lower surface. But as we have seen in our experiment, the upper surface also turns the flow. In fact, when one considers the downwash produced by a lifting airfoil, the upper surface contributes more flow turning than the lower surface.

bluecode · 03-09-2012 08:18PM

Lift of course is generated by interaction of air on both the lower and upper surfaces of the wing. However any attempt at a simple explanation of how lift is generated is doomed to failure, I'm afraid. It's a very complex subject invoking aspects of Bernoulli's and Newton's work. It really doesn't lend itself to any intuitive explanation.

I for one won't even attempt it being a mere pilot who taught using the standard but incorrect explanation at the time. In fact the PPL version taught to students today is barely correct and can only be considered a mere introduction to the subject.

Suffice to say airfoils are neither pushed up by higher pressure underneath or sucked up by lower pressure on top. That NASA website might be a good place to start studying the subject.

So when my son asks me how aeroplanes fly. I tell him, 'Magic, my son. Magic'.:P That's better than 'I don't know' which in truth is the case for most pilots. We only really need to know that exceeding the critical angle of attack results in a loss of lift. :eek:

Zulu · 03-09-2012 08:18PM

Unless you're attempting to suggest that lift is obtained by having a lower air pressure below the wing, your post is much about nothing.
Suggesting, like you did, that lift is obtained by "sucking up" would mean that there would need to be a low air pressure under the wing ("sucking" air from the high pressure above the wing). This is not the case as is easily observed in formula 1.

Feel free to Google, prove me right, and continue to ignore modern laws of physics.

Zulu · 03-09-2012 08:27PM

bluecode wrote: »

Suffice to say airfoils are neither pushed up by higher pressure underneath or sucked up by lower pressure on top. That NASA website might be a good place to start studying the subject.

I've yet to see a paper that refutes that lift is achieved by creating a higher pressure below the wing. Could you please provide a link for the same?
I acknowledge that there are conflicting ideas on HOW a higher pressure is created, but I've yet to see a credible source refute that the air pressure is higher below the wing.

EI-DOR · 03-09-2012 09:55PM

Watch the guys who jumps (or falls) out of this helo. He survived, but it wasn't wasn't pleasent. He would've been safer inside ... maybe.

He fell out. As you's can see what happens when the Tail goes at low airspeed or basically no airspeed. The procedure in the Piston Helicopters (Robinson / Schweizer) is too roll the Throttle off into the Over-Travel Spring as quick as you can, allow the aircraft to settle and cushion the landing by lifting the Collective. I'm not sure of the procedures in the Turbine / Multi-Crew machines but I'd say there is a lot more to do regarding the Engines.

bluecode · 04-09-2012 09:09AM

Zulu wrote: »

I've yet to see a paper that refutes that lift is achieved by creating a higher pressure below the wing. Could you please provide a link for the same?
I acknowledge that there are conflicting ideas on HOW a higher pressure is created, but I've yet to see a credible source refute that the air pressure is higher below the wing.

You won't because pressure is higher below the wing. I'm not really sure why you would I thought otherwise? Of course higher pressure is part of the story but only part of it.

You said this:

What is not correct is your post, and possibly your grasp of physics.
A wing works by creating a higher air pressure below it that above it, thus life is achieved. How is the higher air pressure achieved under the wing?

I suggest you provide a link to a paper that suggest higher pressure below the wing is the main provider of lift. You won't be able to because of course it's not. You are also ignoring the Newtonian principle of equal and opposite reaction. As the air is pushed down the wing is pushed up. Basic physics there.

I suggest a good read is in order. There are plenty of references on the web and plenty of books too. It is a complex subject as I said.

Zulu · 04-09-2012 09:14AM

bluecode wrote: »

You won't because pressure is higher below the wing.

I'm glad we agree.

I'm not really sure why you would I thought otherwise?

I didn't; Confab did.

Jumping out of a crashing helicopter

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