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Prompted by one of the answers to a prior question of mine regarding a scenario involving a helicopter mincing someone with its main rotor in flight:

...I suspect having a human body come in to direct contact with the rotor disk 1) would not “finely mince” a person but instead cause severe blunt force trauma followed by flinging the body or body parts from the disk like a rag doll. -Carlo Felicione

Can a typical full-size helicopter (the linked question was asking primarily about an S-92/CH-148-family copter, but answers regarding any reasonably-typical helicopter are fine) mince a typical adult human with its main rotor at typical inflight main-rotor speeds?

Vikki
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    I'm tempted to say: "Don't try this at home!" ;-) But honestly: I know cass where people lost fingers hitting the rotor of a model helicopter, event if that was "just" made of balsa wood and not being sharp at all. – U. Windl Feb 06 '23 at 07:52
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    @Vikki This doesn't sound like an aviation related question, it's more like a William Osman video title. – user3819867 Feb 06 '23 at 11:59
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    It's neither minced nor blunt force trauma. It's more like being chopped by a sword which is neither like being minced by a blender nor like being hit by a baseball bat. – slebetman Feb 07 '23 at 04:30
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    I suspect that, to finely mince a person, you'd need some sort of mechanism to slowly feed them into the rotor disk. Hang on, I'll just run up FreeCAD... – Dave Gremlin Feb 07 '23 at 10:16
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    Dead is dead, does it really matter whether you're chopped into two pieces or 100? – Barmar Feb 07 '23 at 15:18
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    +1 just for "(the linked question was asking primarily about an S-92/CH-148-family copter, but answers regarding any reasonably-typical helicopter are fine)", and upvote for every horrifyingly reasonable and detailed answer too, i.e., all of them. (And for the comment "Is that also true for the main rotor, though?".) I know little about helicopters but I've learnt a great deal about helicopter people from this question. A quiet backwater of cynical sanity. (I know, I sound sarcastic maybe. I don't mean that, I assure you. This is a great question and answers. What SE is all about!) – lessthanideal Feb 07 '23 at 23:46
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    @U.Windl does a model helicopter's rotor rotate faster than a real one? – Paŭlo Ebermann Feb 08 '23 at 00:22
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    The 1982 fatal accident during the making of 'Twilight Zone: The Movie', although that helicopter's tail rotor assembly had separated and it was in uncontrolled descent. – smci Feb 08 '23 at 00:27
  • @lessthanideal: Full disclosure, I'm not a pilot (the closest I've ever been, or likely will ever be, are paper airplanes and KSP). – Vikki Feb 08 '23 at 01:29
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    U. Windl - even the smallest particle can do great damage at great speed – user3481644 Feb 08 '23 at 11:59
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    Barmar - If you are the victim, is does not matter, however, this is probably from the standpoint of the person who has to clean up the mess, in which case it does matter, especially if you are trying to hide the body parts... – user3481644 Feb 08 '23 at 12:01

7 Answers7

25

Mince:

Cut up or grind (food, especially meat) into very small pieces, typically in a machine with revolving blades.

Blunt force trauma:

Injuries resulting from an impact with a dull, firm surface or object.

Helicopter blades are neither sharp enough, nor spinning rapidly enough to cause the sort of fine mincing you might get with a food processor, nor are they simply a "dull, firm surface." There is a lot very severe damage possible to the body in between "blunt force trauma" and being "minced", but I don't think you will get a detailed answer until they make a "chicken gun" for human cadavers and run some actual tests.

Michael Hall
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    I assume that there have been lots of accidents in that direction and probably accident reports. In the frame of this question there isn't really a need for testing of the unknown – Apfelsaft Feb 07 '23 at 10:21
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    @CarlBerger, I agree, that part of my answer was facetious. – Michael Hall Feb 07 '23 at 15:58
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    @CarlBerger I would disagree with your assumption as it is baseless since you have no citations. Purposes for such testing could include determination if such a death was accidental or intentional, and if accidental, how it happened and how it can be prevented. – user3481644 Feb 08 '23 at 12:04
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    @user3481644 ah well sure you can disagree, if you want. However.. it's common knowledge that aviation is strictly controlled (in US, Europe etc anyway), and accidents are reported & listed in an effort to increase safety. – Apfelsaft Feb 08 '23 at 23:26
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    @user3481644 Just because I didn't cite the data base, doesn't make my statement dismissable. But since you asked, simple google-fu helps: "data base of aviation accidents" leads eg to https://www.ntsb.gov/Pages/AviationQuery.aspx, listing 10488 helicopter accidents and 1038 fatal ones. Other people have analyzed similar data bases & written reports: https://www.unboundmedicine.com/medline/citation/8216149/Helicopter_rotor_blade_injury:a_persistent_safety_hazard_in_the_U_S__Army – Apfelsaft Feb 08 '23 at 23:32
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    @CarlBerger - My disagreement is about your assertion that "there isn't really a need for the testing of the unknown". – user3481644 Feb 22 '23 at 12:58
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    @user3481644, fundamentally I agree with your statements, but what is there to learn by testing that isn't intuitively obvious? (that a rotor blade will mess you up bad...) – Michael Hall Feb 24 '23 at 06:07
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    @MichaelHall Forensic studies are conducted to learn details about how people are killed (among other things). If someone were to be chopped and foul play were suspected, the forensics experts would look over what's left and attempt to determine what happened. I've seen dramatisations of bashing fake human heads to see what splatter patterns are created. Such a study (with helicopters) might lead to determine if the victim was clumsy or pushed. – user3481644 Feb 28 '23 at 18:46
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    @user3481644, I think you over estimate the number of instances where someone is killed by a rotor blade and actual forensic investigation is needed to understand "why" or "how" it occurred... – Michael Hall Feb 28 '23 at 18:49
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It will absolutely cut you to pieces. In fact, there are documented cases of rotor disks flexing enough to cut their way through the cockpit. That's why helicopter helmets are very heavy and uncomfortable, they are rated to take a hit and (potentially) survive it. But having seen helmets that have taken a hit, I can't picture it being survivable. (former helicopter crew member)

SteapStepper69
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Dante
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    Have a read here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8574166/ "A Case of Penetrating Head Wound Due to Helicopter Rotor Blade Injury in a 34-Year-Old Naval Helicopter Pilot Who Returned to Active Service 5 Years Later" The primary helicopter pilot was a tall man. He raised his head into the tail rotor tunnel and was hit when he left the cockpit to check the refueling process. Despite being cut by the rotating blade, the helmet had a protective effect, preventing fatal injuries. it (sometimes) works! – EarlGrey Feb 06 '23 at 08:52
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    @EarlGrey -- astoundingly flawed logic (mostly likely an inadvertent error on author's part) shown in following sentence from above link ("Discussion" section) : "This shows that ground crews still have nearly a 15% chance of head injury when performing ground tasks." – quiet flyer Feb 06 '23 at 18:53
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    Into a few pieces, sure... But finely "minced"? – Michael Hall Feb 06 '23 at 22:35
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    @quietflyer I did not go past the abstract, so I could not enjoy the statistic extrapolation :D . I trust doctors for their cases-by-cases knowledge, I let statistics to (other) professionals ;) . – EarlGrey Feb 07 '23 at 07:21
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    @EarlGrey Note that this injury was caused by the tail rotor, not the main rotor: "causing the right side of his helmet to be hit by the tail rotor" – zovits Feb 08 '23 at 13:17
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Minced could be closer than blunt force trauma, but neither is really going to be a great description.

If decapitation is possible as @filo points out in the comments, we're not talking mere blunt-force trauma. Cutting into smaller pieces is partly a matter of feed rate. Someone falling from just above into a blade would be fed through quite slowly and end up in a state closer to "minced" than the image conjured up by blunt force trauma, which implies (largely) intact. But it's still not really mincing, even though that kind of speed there will be a lot of loose little bits flying around. Of course some of the bigger body parts will be flung away, especially if they enter the disc near the blade tips. Conversely falling into the blades above the fuselage would constrain the remains allowing for more chopping.

"Shredded" might be the best word.

Chris H
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    Decapitation is possible. Read up on the Vic Morrow case. Wiki: "Morrow [was] decapitated and mutilated by the helicopter rotor blades..." – Tony Ennis Feb 07 '23 at 18:32
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    @TonyEnnis,yes, that's the same case that I credited filo with finding (I had read about it before) – Chris H Feb 07 '23 at 18:50
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    Decapitation is possible. This medical peer-reviewed article: https://link.springer.com/article/10.1007/s12024-015-9721-5 is a forensic study on an helicopter accident. Please note: it has heavy graphic content. – EarlGrey Feb 09 '23 at 12:28
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    @EarlGrey like Tony you may have missed the meaning of my use of "if" - not a conditional but "accepting that". I'm wondering whether this a mainly a British usage though the discussion at English.se doesn't suggest so. It' smight also be a little dated, and anathema to programmers – Chris H Feb 09 '23 at 13:13
  • (Freely-available copy of the article linked by @EarlGrey, for the benefit of readers who don't have a subscription to Forensic Science, Medicine, and Pathology.) – Vikki Feb 12 '23 at 16:10
  • Note that filo's comment's apparently been deleted, so it's not particularly useful to link it in the answer. – Vikki Feb 12 '23 at 16:14
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"Mince" implies multiple strikes -- and really, more than just two or three. The distance between each main rotor blade of a full-scale (manned) helicopter suggests that multiple strikes from the main rotor blades are unlikely. The body would likely be thrown clear during the first few strikes. Therefore, regardless of whether the nature of the injury from a single strike would be better described as "cutting / slicing", "blunt force trauma", or something in between, the answer to the actual question is "no".

(The number of rotor blades could have some influence on the answer though-- )

quiet flyer
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7

A bunch of good points are being brought up in the comments.

First to point to the differences between the tail and main rotors, despite being locked through the transmission and rotation in synchrony (except when pedals are depressed) the speed of rotation and angle of incidence between the two are quite different. The tail rotor is balanced to only counter the rotational effects of the main disk, not provide the lifting force for the helicopter. So any thoughts of an equal comparison between the two is not appropriate.

Now for the ideas about the main rotor system, there is certainly a difference in speed between the center of the rotor and the tips, with the tips traveling at a speed somewhere on the order of .6 mach. Depending on the position of the collective the angle of incidence of the main rotors is changed. A worst case scenario could be achieved through a horizontal blade angle at time of incident.

Having seen 2 helicopter flight helmets which were struck by the main rotor in my time as a flight medic I can say that the mechanism of injury is certainly severe enough to result in clean cuts to unprotected human anatomy. This is also in line with the actual fatalities that have occurred from contact with the rotor system.

The speed of the blade compensates for the perceived dullness of its leading edge. Try pressing your finger against a sharp knife, versus dragging it down one. If you dont believe that the edge is relevant (since its too sharp compared to a rotor) maybe try an axe, since they are honed to being roughly 2x as blunt as a knife. if you cant draw blood on the axe, move your finger quicker, im sure it will feel just like a razor blade, from personal experience.

Dante
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A friend who served as a helicopter repair station crew chief in Viet Nam says that will happen if a human walks into the tail rotor of a Huey. He himself heard the sound of a human skull getting buzzed to pieces in this way.

niels nielsen
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    Is that also true for the main rotor, though? – Vikki Feb 05 '23 at 23:26
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    It depends on how the body came into contact. If slowly, then it could since there isn't enough mass to stop the rotors. If it was in flight and someone jumped on to it, well, that will require a very specialized test. – Nelson Feb 06 '23 at 01:26
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    @Vikki Isn't it mainly about the "impulse divided by area" (basically mass and speed of the rotor divided by the impact surface)? So the main rotor may be "less sharp than the tail rotor, but the mass should compensate that easily. Maybe someone can impress us with realistic numbers... – U. Windl Feb 06 '23 at 07:56
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    @U.Windl I could be wrong, but I thought that the tail rotor and main rotor are usually mechanically linked through a geared shaft. So if your unfortunate head tries to slow down the tail rotor, it also has the inertia of the main rotor to deal with. – Wayne Conrad Feb 06 '23 at 19:06
  • @WayneConrad I could be wrong, but it is my understanding that the tail rotor speed can be adjusted to change the direction the aircraft is facing. – user3481644 Feb 08 '23 at 12:11
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    @user3481644 I believe that the tail rotor pedals change the pitch of the tail rotor blades, in a similar mechanism that the main rotor's collective control uses. The tail rotor's RPM remains proportional to the main rotor's RPM. – Wayne Conrad Feb 08 '23 at 15:33
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ah well. not sure how much this has to do with aviation, but here it goes..

Hitting the rotor tip of a modern Helicopter:

Rotor tip speed is usually designed to be slightly below the speed of sound. Let's find something we can compare it to: a 0.45 ACP bullet is also blunt and subsonic maybe traveling at similar speeds. I have yet to hear of that story where a person got a blunt force trauma when shot by a 0.45. I'd assume the way a helicopter blade interacts with a body will be somewhat similar, just a lot larger and more powerful..

Hence. You won't get a heap of finely minced meat, but likely a few chops. The body won't be thrown around away by "blunt force". The question apparently was addressed already and some people have run simulations on it. For the less faint hearted, here's a visualization of the the 100% accurate simulation: www.youtube.com/watch?v=VDcDQX7TjhE

I also don't buy that the helmets will withstand much. If you move very slowly, and the first strike is only grazing, then maybe the person realizes soon enough what's going on - else it's a (subsonic) cannon ball to the head.

Hitting the rotor close to the hub:

There seems to be a non-minced case from the early days of helicopter development: www.youtube.com/watch?v=ixDn8Ak4kz8

Apfelsaft
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  • A nice animation, but not really a physics simulation. – Vladimir F Героям слава Feb 07 '23 at 10:06
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    Well it is a physics simulation in the sense that physics simulations are also just mathematical models that approximate the physics. The result is always just a solution of the mathematical model - and often only an approximate solution of that. It's true that I don't know the tensile / shear yield stresses that were used in the animation – Apfelsaft Feb 07 '23 at 10:14
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    Still, I read that .45acp ballistic gel peneration is still deeper than a lot of human bodies are wide - and a chain of that will ultimately sever the two body into two parts. That's what the helicopter blade will do, too. – Apfelsaft Feb 07 '23 at 10:15
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    The "100% accurate simulation" are your wodse, not mine. But this actually does not look like serious physics simulation at all. Rather some simplified physics in Blender or other similar video generation software. Also, ..45ACP is a much smaller object that will penetrate much more easilly. And don't forget that a human body also contains bones (which also the video appears to ignore). – Vladimir F Героям слава Feb 07 '23 at 11:45
  • I do believe that the blade can cut a person in half. But these particular arguments are simply not convincing. – Vladimir F Героям слава Feb 07 '23 at 11:49
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    I agree .. "100% accurate" in Blender was for laughs, and obviously the whole animation was made for laughs. It was my geek side that felt compelled to take up that argument about the accuracy. – Apfelsaft Feb 08 '23 at 09:27