News Bin Laden Raid Reveals Possible Stealth Helicopter

[Sky Captain]

It looks like at least a modified UH60. Tail section is different and there is no rivets. A picture posted earlier with tail section of standard model shows plenty of rivets, this one has smooth surface.
It wouldn't really suprise me if US has developed a stealthy modification of UH60 for missions like this.

 

[dougkeenan]

The rotate this around and watch the spacing - if it is close to 72°, it is OK, if the variance is too big, you need another number, and I am pretty sure that 90° is fitting better.

"Pretty sure" - is that an orbital mechanics term?

Is it fair to say you're "pretty sure" that Aviation Week - along with a few posters here - errs in viewing this as a non-standard aircraft?

---------- Post added at 08:06 ---------- Previous post was at 07:47 ----------

It looks like at least a modified UH60. Tail section is different and there is no rivets. A picture posted earlier with tail section of standard model shows plenty of rivets, this one has smooth surface.
It wouldn't really suprise me if US has developed a stealthy modification of UH60 for missions like this.

Pretty sure you're right. My eyes see differences here, and I don't mean the paint color.

 

[Urwumpe]

Is it fair to say you're "pretty sure" that Aviation Week - along with a few posters here - errs in viewing this as a non-standard aircraft?

What does "non-standard" mean? That it is no standard UH-60 model? Or no standard MH-60 model? Damn sure. I would not expect more than 24 of such helicopters to fly around.

But if non-standard means, that this is no member of the Black Hawk family, then you, Aviation Week and a few posters there (which are generally less expert as some people you have already found in this thread), have a dire need to get to an optician.

Pretty sure you're right. My eyes see differences here, and I don't mean the paint color.

Yeah, likely they hired a Mi-26 for the mission. :facepalm:

There are already dozens of alternative designs around that get rid of the noisy tail rotor that also makes a lot of radar reflections - and a new design must of course have a tail rotor. Even if the costs of a tail rotor are lower - they are not that much lower that it makes sense to reject them especially if the alternatives are more silent and really invisible to radar (at least from front).

A tail rotor in this means precisely that the basic structure and mechanisms of an existing transport helicopter in that size class had been used. Which is only the MH-60K. What you complain about as critical differences and what likely many aircraft pseudo-experts will believe with religious zeal: You likely think the fuselage is a self-carrying structure that can't be changed. But that is pretty much wrong - most parts at the tail are just fairings, that can easily be swapped. They do nothing else but protecting the main structure and the mechanics inside the tail from wind, weather and shrapnel.

 

[dougkeenan]

What does "non-standard" mean? That it is no standard UH-60 model? Or no standard MH-60 model? Damn sure. I would not expect more than 24 of such helicopters to fly around.

Looks like not more than 23 now. Good then we're all on the same page. Except for the lights thing, but so long as we agree this isn't a standard UH-60 that doesn't matter.

A tail rotor in this means precisely that the basic structure and mechanisms of an existing transport helicopter in that size class had been used. Which is only the MH-60K. What you complain about as critical differences and what likely many aircraft pseudo-experts will believe with religious zeal: You likely think the fuselage is a self-carrying structure that can't be changed. But that is pretty much wrong - most parts at the tail are just fairings, that can easily be swapped. They do nothing else but protecting the main structure and the mechanics inside the tail from wind, weather and shrapnel.

You don't know what I think. More likely I think you haven't given us a number yet on which rotor blade is not a rotor blade. Drei? Vier?

 

[Urwumpe]

You don't know what I think. More likely I think you haven't given us a number yet on which rotor blade is not a rotor blade. Drei? Vier?

Actually, Quick Nick did, and I had nothing to add there, didn't know if this is now personal.

 

[dougkeenan]

Actually, Quick Nick did, and I had nothing to add there, didn't know if this is now personal.

This. Is. Orbiter. Only personal if you want to make it that way.

 

[HarvesteR]

I see five slots on that hub, and four blades, with a probable fifth one bent or sheared out...

The spacing IS weird. that is true. But suppose this:

The helicopter crash landed from a low height, and the tail rotor hit the ground spinning.
Blade 5 (the one that is most pointed towards the camera) struck the ground first, and got bent out of shape.
Blade 4 (the one that can't really be seen) struck much harder, and was partially sheared off.

This would explain the odd placement of the top blades as compared to the bottom ones.

Well, my 2 cents about it...

Anyhow, what if it IS a new BlackHawk variant? wouldn't be a first for the US military to be caught red handed with a new toy (RQ-170 Sentinel comes to mind)... Most likely though, it's some kind of tail rotor mod to improve efficiency/noise suppression...

No idea really... But I can clearly see space for 5 blades there... even if not all of them are there.

 

[Coolhand]

I concur, based on the notches its easy to see that the tail has a 5 blade rotor, assuming there's a notch for each blade. I've illustrated this, taking into account perspective distortion and the depth of the hub cover... You can tell this from the notches indicated 1 and 2 in the image along with the estimated centre point of the hub - in plane with the blades, not the visible centre, which is projected out from the centre.

the reason the spacing might look weird is just a perspective thing. in the image, the angle between notches 1 and 2 is around 78 degrees, too much for a 5 bladed rotor.. but of course you have to correct for perspective, and in this case that angle shrinks to approx 72 degrees - it certainly cannot grow larger on perspective correction.. so its never anywhere near 90 degrees.

 

[Urwumpe]

it certainly cannot grow larger on perspective correction.. so its never anywhere near 90 degrees.

Currently it is a vertical ellipse, what should be a disc when rotated into proper perspective. What does that projection mean to all vectors in the image that are not vertical?

 

[Tex]

There are already dozens of alternative designs around that get rid of the noisy tail rotor that also makes a lot of radar reflections - and a new design must of course have a tail rotor.

Are you referring to something like this?

IMO that would be the best stealthy option for a helicopter. On topic with this particular crash, I too see 5 blades, sorry mate!

 

[dougkeenan]

Could something like that be used to redirect exhaust heat?

 

[Urwumpe]

Could something like that be used to redirect exhaust heat?

Sure, it could mix the exhaust with cool air and make it less prominent.

This system just has the disadvantages that it consumes more engine power and costs more.

 

[Tex]

This system just has the disadvantages that it consumes more engine power and costs more.

Good point. Makes sense, the engine has to work harder to push all that air down to the tail vs having a traditional tail rotor. It must have proved too difficult to make a helicopter like that which would be capable of carrying the same load as a Black Hawk or I suspect they would have incorporated that design by now. :shrug:

 

[Turbinator]

any guess about the badges? bet they know how many lights

Is that a reference to the Star Trek: The Next Generation episode called Chain of Command?

Relating to this:
http://en.wikipedia.org/wiki/2_+_2_=_5

 

[statickid]

Currently it is a vertical ellipse, what should be a disc when rotated into proper perspective. What does that projection mean to all vectors in the image that are not vertical?

they would stretch into proper shape, but not rotate or disappear

 

[Urwumpe]

they would stretch into proper shape, but not rotate or disappear

But how would the angle between two vectors in the projection change? lets say, you have 45° between (1,1) and (0,1), what would happen to the angle if you have both stretched by 2 in x : (2,1) and (0,1) ?

(I simplified the math a bit for making the point easier, in reality it would be a different general formula for the angle between two vectors that has the same results)

[math]\alpha_0 = \arctan{\frac{1}{1}} = 45°[/math]
[math]\alpha_1 = \arctan{\frac{2}{1}} = 63.43°[/math]
It does grow, because you actually de-rotate the disk, not rotating a disk into the observed angle.

Who wants to check the data on the general formula:

[math]\alpha = \arccos{\frac{\vec{v_1} \cdot \vec{v_2}}{\left| \vec{v_1} \right| \cdot \left| \vec{v_2} \right|}}[/math]

 

[dougkeenan]

Is that a reference to the Star Trek: The Next Generation episode called Chain of Command?

Relating to this:
http://en.wikipedia.org/wiki/2_+_2_=_5

I see four lights. And five blades.

 

[Ark]

Good point. Makes sense, the engine has to work harder to push all that air down to the tail vs having a traditional tail rotor. It must have proved too difficult to make a helicopter like that which would be capable of carrying the same load as a Black Hawk or I suspect they would have incorporated that design by now. :shrug:

Perhaps that suggests that the helicopter was a heavily modified Blackhawk, instead of an entirely new design. If you really wanted to build a new, stealthy helicopter, you probably wouldn't have a conventional tail rotor. At least it would be shrouded like the Comanche.

 

[CigDriver]

Looks like Ark hit it on the nose, at least according to this article:
http://www.armytimes.com/news/2011/05/army-mission-helocopter-was-secret-stealth-black-hawk-050411/

A blackhawk with applique stealth panels over the airframe

*edit* Here is a speculative sketch I just found:
http://cencio4.wordpress.com/2011/05/05/stealth-black-hawk-down-revised-sketch/

 

[Hlynkacg]

Perhaps that suggests that the helicopter was a heavily modified Blackhawk, instead of an entirely new design. If you really wanted to build a new, stealthy helicopter, you probably wouldn't have a conventional tail rotor. At least it would be shrouded like the Comanche.

The H-60 is a very modular design, and it is worth noting that the tail rotor and it's gearbox are a self-contained module (likewise for the main rotor). We'd routinely remove the entire assembly for inspections/overhauls, so I imagine that installing a non-standard rotor on an existing airframe would be fairly easy.

Further-more the classic shape of the h60's tail is simply alluminium and fiber-glass fairings that wrap around the underlying frame. Non-standard fairings = non-standard shape. Note that the TGB Inspection/servicing window is in the same spot on both versions.



---------- Post added at 06:01 PM ---------- Previous post was at 06:00 PM ----------

Oops, scooped by Cigdriver