Disabling a helicopter

Skyler said:

Where could you hit a flying helicopter that would force it to land but not cause it to crash?

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The pilot's head?

Oh NOT cause it to crash... In that case I think he'd have to be a helicopter mechanic or have a heavy rifle. If it's a .50 or something heavy he could just take out the engine, a good pilot can auto-rotate down. It would need to be a beefy rifle though, I don't think a .30 calibre or lower would reliably take out the engine.

Otherwise you'd have to know the specific internals on that particular model of helicopter to target softer engine parts.

what kind of helicopter? If it is a civilian version with a turbine engine, a .50 could take off a couple of turbine blades.

This would cause the engine to shake a lot and run badly. And if parts got sucked in, engine failure might happen. The pilot would probably not know what had happened, but would put down ASAP to check the damage.

See picture:
http://www.mod.uk/DefenceInternet/T...310HEPT_RTM322.jpg&alt=RTM 322 Engine Diagram

Orange parts to the right in the picture are low pressure fans. they sit at the front end of the engine. If you break off some blades there it will be problems, but AFAIK would be manageable.

The blue parts in the middle are high pressure fans, surrounded by fuel lines and lots of metal. If you hit them parts might blow straight through the heilcopter and shred the engine. but since they are in the middle I don't think the bullet will penetrate that far.

Tail rotor. Copters are designed to auto gyrate if they lose power or the power train goes out to the tail. There's always a risk some persons would die on crash, but most survive. One or two well placed shots to the tail rotor or drive shaft running through the alum tunnel will bring her down.

I would suggest the tail rotor too, but there's always these pesky NOTARS.

I think you'd want to be sure to get it first time. You might not get a second chance!

Skyler said:

It's a .50 cal.

If he puts a hole in the fuel tank, that would force them to land before they ran out of fuel, but of course there's an ignition risk. (Mythbusters tried shooting holes in gas tanks and didn't get a kaboom, but they weren't doing it with a running engine either.)

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I assure you the whole "kaboom" thing with bullets being shot into gas tanks is hollywood drama.

There are numerous cases during war where gas tanks were shot during the operation of an airplane or helicopter and there was no explosion.

Skyler said:

My research indicates that the helicopter in question is probably going to be an Mi-24 (Hind). Which raises a minor technical difficulty in that the Mi-24 is supposed to be armored heavily enough to resist .50-cal rounds.

A small cannon might be able to punch a hole in the tail rotor. I don't know, though. What do you think?

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If you're looking at a Mi-24 (Hind) then you need to look no further than the invasion in Afghanistan in the 80's by the USSR. The Afghan people could not bring down the hind until they were able to get Stinger missiles. The Hind is a formidable helicopter and you are correct in the fact that they are heavily armored. But, tail rotors are not armored, so to speak, so they can move freely. A disabling shot to the tail rotor would work, but it would be one hell of a shot and be able to dislodge or disable at least one rotor to send the tail rotor off-balance.

And this thing is moving at the time? I'm just saying, the Hind is not a slow aircraft. Cruising speed in excess of 150mph, I think (?) Putting a lot of rounds into the tail assembly could be tricky.

Oh dear...

Skyler said:

My research indicates that the helicopter in question is probably going to be an Mi-24 (Hind). Which raises a minor technical difficulty in that the Mi-24 is supposed to be armored heavily enough to resist .50-cal rounds.

A small cannon might be able to punch a hole in the tail rotor. I don't know, though. What do you think?

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Hoo dear. No offense, but have you seen a Hind? It's a bit like an armoured barn covered in cannon and warheads and moving far too fast for something that big.

It was purpose built to wade through sustained .50BMG machine gun fire without difficulty and in most versions the cockpit shrugs of 37mm cannon hits. The rotor blades, head and assembly are titanium reinforced to take repeated hits from .50BMG without degraded performance.

Now, I have never seen an explicit statement that the tail rotor head is reinforced like the main rotor head, but I would think so.

In Afghanistan, the mujaheddin had severe difficulty using 14.5mm machine guns and 23mm cannon against them and only got them down reliably when using direct hit missiles to shut down the engines.

Here is a picture of the tail rotor assembly. (It's on a Mi-8/17, but it's the same as on a hind minus the armour)

http://www.flickr.com/photos/16498755@N07/5302391133/#/photos/16498755@N07/5302391133/lightbox/

To reliably take it out of action with a bullet you would need at least a 20mm round and hit a target smaller than a dinner plate from the right angle.

If he has a choice of weapons I would recommend an upgrade to one of three things. Either an antitank weapon of some sort, like an AT-4 or a RPG-7, and if that is not available, a very large antimateriel rifle like the ntw20, and if all else fails, a 14.5mm machine gun with API-rounds so he can fire bursts at the tail rotor repeatedly.

I'd think it reasonably possible for the shooter to use a Stinger and have it miss the main and take out the tail (due to the craft rotating or some such.)

The Hind has two quirks though that can be exploited.

One, if it is heavily loaded it need it's wings to stay airborne. If you can trick it into a tight turn, it may lose lift from the wings and stall out, forcing it to land in a controlled crash.

Two, since it is so grotesquely heavy, the rotor blades are bent downwards to increase stiffness when flying. If the Hind hits a strong updraft like when it flies to tight over a ridge top, it will lift to fast and the rotor blades will bend down at the tips and hit the tail.

Of course tricking the pilot might not be the easiest thing to do.

Igla

Williebee said:

I'd think it reasonably possible for the shooter to use a Stinger and have it miss the main and take out the tail (due to the craft rotating or some such.)

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The stinger is a direct impact missile with pretty good maneuverability. If there are Hinds, there might be other russian things perhaps? An Igla (Nato name Sa-2 Grouse) is like a stinger, but somewhat more primitive except that it has a magnetic fuze so a near miss due to the Hind dropping flares, would still make the warhead explode if it came close enough to the tail.

Skyler said:

Although on second thought I love that NTW-20. A BFG would really fit his personality.

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I wanted one too, but then my SO pointed out that since I am usually too lazy to carry out the trash, what were the odds that I would lug that thing to the range?

Yeah, taking out a Hind with small-arms is quite a task... For starters, it's a mil-spec vehicle, so it's armoured. Not on the level of ground vehicles, because it has to fly, but enough to shrug off most small-arms fire. A hit to the tail rotor would do it, as would a round through a turbine (a mil-spec vehicle suggests a military pilot, who'd be trained to deal with forced landings). The problem is that the rotor downwash would throw most shots off unless they're heavy rounds at high speed, so the sniper would have to be a damn good shot, and lucky to boot.

If he is absolutely superhumanly accurate, I'm wondering if there's anywhere in the tail rotor assembly that a perfectly positioned .50 round could stop it rotating, if it jammed in there just right.

To be honest, though, that sort of shot is pushing even my suspension of disbelief, and I'm well into superheroes

When people say that the Mi-24 was armored, they weren't lying, but that's a far cry from the entire aircraft being armored like a tank. The crew compartment was protected from the front, and like all Russian military helicopters of the day, was grossly overbuilt. But, it was not covered in armor -- it wouldn't get off the ground if it were.

The helicopter couldn't hover when carrying a full combat load. It had many tweaks to make it fast: tilted rotor system, stub wings, and a tilted tail rotor all of which are cool innovations for making it fast. However, like mentioned before, it couldn't always hover because of the weight and the compromises to make it faster. It was deployed much like an airplane because of these limitations and it's pig-like maneuverability (when compared to other attack helicopters). It is a flying tank, from that perspective.

So, your .50 caliber sniper rifle can do plenty of damage to the engines. If your bullet does knock off some compressor blades, the engine will shred itself because of either the imbalance or because of the debris flying through the engines. These things turn at ungodly RPMs so any slight balance problem cause much bigger problems.

The rotor system was a typical aluminum honeycomb and a bullet will go right through them. This is really hard to do since a bullet flies a lot faster than a rotor blade and will pass right through the gaps unless your sniper has magic powers and can see and hit a spinning blade. Same for the tail rotor. But, a hole in the main rotor blade will not force the helicopter down unless the pilot decided to do so for safety.

Shooting the fuel tank is pointless. All modern tanks are self-sealing and won't leak. You might get really lucky and hit a high pressure fuel line and that will cause problems -- and the possibility for a fire if it's near the hot parts of the engine.

Your best bet to bring it down without killing everybody would be to hit one or both of the engines. The helicopter can autorotate down and if the pilot is skilled and the conditions are correct, the helicopter can be landed without significant damage. The engines would have to be replaced.

You can shoot out control linkages and other rotor components if you're lucky, but this would most likely lead to an uncontrolled crash where survivability is questionable.

Technical stuff on the construction:
STRUCTURE :
Five-blade constant-chord main rotor; forged and machined steel head, with conventional flapping, drag and pitch change articulation; each blade has aluminium alloy spar, skin and honeycomb core; spars nitrogen pressurised for crack detection; hydraulic lead/lag dampers; balance tab on each blade; aluminium alloy three-blade tail rotor; main rotor brake; all-metal semi-monocoque fuselage pod and boom; 5 mm hardened steel integral side armour on front fuselage; all-metal shoulder wings with no movable surfaces; swept fin/tail rotor mounting; variable incidence horizontal stabiliser.

pilot27407 said:

Good luck trying to bring a Mi-24 with a bullet (or a whole mag full). Even a hit from a 30mm canon won’t do it every time. Tanks are armored, and engines are heavily armored. Even the cockpit windows are resistant to anything below a .50 cal. In ’82 (during Iran Iraq war) they shielded even the tail rotor head. Suggest you switch to a Mi-8. Or, have your sniper fire from above. Have him on a mountain top with the chopper below. A lucky shot (nothing to do with the sniper’s efficiency) by a .50, through the cockpit’s top, hitting the electronics “blue box” would force the pilot to land.

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Again, there's a lot of myths about the Mi-24. A well placed bullet will bring it down, just like any other helicopter. It's not impervious. It does have armor, but not all over and not completely protecting the engines according to the technical sources I've seen. A helicopter with that power level and size will not fly if it were completely armored as popular culture seems to think it is. For example, the engine intakes are completely open. Put a round through that, and you'll destroy the engine. A really good sniper could do it.

Most mooks shooting at a Hind probably never hit the damn thing. There's also a lot of surfaces that have nothing important so if it were hit, it wouldn't make any difference. Stingers did work really well to bring them down, but again, that's more to do with actually hitting the target than anything else.