Easier than designing a stealth/low observable utility helicopter from scratch, or massively modifying a UH-60 to represent some of the artist illustrations in this thread.

Being a design engineer, my assumption is that the process would be along the lines of cost/benefit analysis of varying degrees of modification.

The technical complexity of altering the forward fuselage structure around the cabin, engines, and transmission for low observability to any great degree would be unappealing. Whereas, treating the rotor heads to some radar absorbent hats, and maybe putting radar absorbent mats over the cabin windows on the other hand seems an easy win. Design and rapid prototype/manufacture of a tailboom specifically with low observability in mind sits somewhere between the two.

OK.
In particular for the tail rotor changes, as one starts adding weight way back there at the end of the tail the W&B and Vibe issues that crop up can be a bugger. Though likely achievable.
.I am thinking that the whole tail boom would a be bit more than needed, given your point on the rest of the airframe.
Maybe only the last bit, aft of the intermediate gear box (significant changes in shape and reflective geometry back there already) but the point I refer to above in re the W&B and vibes would take some sorting out. (Though achievable if one has the budget).

To what degree does the fuse skin on the Blackhawk transmit loads?
I assume it's an integral load bearing part of the airframe, and you couldn't simply `re-skin' a standard UH-60 with some exotic RAM material and add a few rotor hats etc.
The other thing that is very odd about the photo is the tail-rotor blades.
Even taking into account that weird coolie hat that sits on it - the blades looked shorter than a standard UH-60 tail-rotor.
The stabilator was also not a standard UH-60 one.
I'm as cynical as the next punter, but in this case, I do think there's some substance to the story.
Have a look at HaveBlue, Tacit Blue and some of the other weird predecessors to the F-117 and B-2.
Landing gear from an F-5, engines from a T-2C - FBW from F-16.
Noting that rotorcraft are in some senses an order of magnitude more complex than fixed wing aircraft, surely It's still possible to build something quite unusual in small numbers - using off the shelf components - landing gear, transmission, rotor system engines, avionics.
If it proved to be stable and reliable enough - one might even consider using it as a tactical advantage on such a mission...

Assuming the dynamics of the rotor system are maintained (including the effect of the fruit bowls) then the issue is one of airframe stiffness. Matching the stiffness of the structure you are replacing, or, at least not negatively impacting it, preserves the existing response. Computationally this is pretty trivial to calculate even by hand so I don't see that as an issue, and I am thinking in 2005 terms for software tools. I would suggest looking towards the ACCA/X-55A as an example of how this kind of modification can be achieved on a larger scale than the tailboom of a UH-60 variant.

I do take your point about the extent of the mod not needing to be the entire tail boom. I looked at the UH60 and it seems that for a non-Naval variant, the easiest place to split the airframe is at the panel line just aft of the exhausts, where the contours change. You would be able to maintain the tail rotor torque tube positioning and layout. It occurred to me whilst looking at photos and drawings that if you parts binned the airframe, you could use a Naval variant tail which would allow you to develop just the parts aft of the fold point.

In terms of how and where these mods were carried out, you'd obviously need tooling and jigs. There are re-configurable fixturing systems out there, like Meccano for grown ups. I've used it to prove out robotics systems on commercial airline sized wings, and I know it has been used for much much more besides. You could keep that all in-house, no need to get any heavy steel people involved for jigs other than some laser cut plates, besides just buying the meccano kit. I imagine that there are discrete facilities in the US that could accommodate and carry out all this mod work without issue.

As ever with low observables you have to decide what you want to achieve before you get going. Do you want to just reduce detection range a bit or a lot? do you just want to confuse radar computers by presenting a signature that won't be in anyone's data? what frequency ranges do you want to optimise for? I'll admit that the tailboom is not likely to be giving that great of a signature in comparison to the rotating parts or the cabin returns through the windows. But it does seem the most appealing on cost/benefit to me.

The handling qualities, weight and power are referred to negatively more than once in discussions around this mission. This suggests that there could be changes to both rotor systems to reduce signature at the expense of performance, and that there is obviously a load more weight (either because they were over filled or because they were covered in older RAM? or, more likely both! ).

I don't think anyone would produce a dog from scratch to be the taxi for the guys at the tip of the spear. That doesn't sit well with me.

The easiest way to avoid a structural resonance with one of the N/rev frequencies is to have your engineers design the structure to hit it. In my experience, including through 2005, is that it is not that easy!

The Blackhawk structure is very conventional semi-monocoque construction. The skin definitely transmits loads, especially in the tailcone.

Don't shoot the messenger... :cool:
Link to the story...



https://cimg8.ibsrv.net/gimg/pprune....5803a0a7cb.jpg

Just out of curiosity, why the round (cross section) external fuel tank rather than one with different angles? Also, the tail rotor in that photo does not align with some of the pictures from the 2011 raid, so perhaps that photo is the old "this is a work in progress" deal.

Perhaps because non stealthy round tanks could be jettisoned before reduced cross section was really needed on certain missions? External tanks are rarely jettisoned, but for a a really high profile mission such as Eagle Claw or OBL raid maybe tanks could be jettisoned before reaching the higher threat target area. Maybe even the whole stores pylon could be jettisoned? I do agree with you this has the appearance of a development bird, with incremental bits and bobs being trialed.

Interesting possible link to Felker Field at Ft. Eustis. Usually a pretty sleepy field but always with some interesting relics from various 1960's and 1970's rotor projects dumped about the field and a few preserved on base, such as the high speed compound Huey's and others. It was neat to drive around and see some surprises. The transportation museum there is worth a visit, with great Army aviation pavilion, and a few more aircraft inside, including the crazy single solider VTOL experiments.

How fascinating! The background doesn't look like Virginia. Perhaps Groom Lake, TTR or Edwards North?

It's a strange combination of presumably low observable features (nose, MRH, engine inlets and exhaust...) and high signature elements (pylons, antennas, tail rotor...) I wonder if it is a re-used signature experiment after that work was complete?

Hmm, we used to bounce there. SH-2's back in the 80's, and IIRC we used to pick up their PAR for training flights. Just north of there on the James River was what we called the Ghost Fleet. Dozens of very old ships, most of them supply and support ships, parked at an achorage against the need to take them out of mothballs and use them to move material across the Atlantic. I think that was eventually disposed of a while back; made for an interesting set of targets radar training flights for our new aircrewmen.

Judging from the fence in the background and the terrain, I do not think it’s Groom Lake or TTR or Edwards but could be Libby Army Airfield at Fort Huachuca (Home Inscom training and airborne SiGINt / ELINT) , as we talking about EH-60A.

below is Libby AAF and mountains behind are not as high as Groom or Edwards..


https://cimg6.ibsrv.net/gimg/pprune....a557f8f32.jpeg

cheers

This was a kit specifically developed for EH-60A DFE. It was found impractical enough that a lot of the applique was not used in the first gulf war. The forward hemisphere was considered most important so the parts applied to the tailboom were removed first (also noting vibe issues as we discussed previously). Looks like the aircraft had RAM coatings.

I am a member of a different forum that has some contributors that keep track of these sorts of things. This photo was first found on the net over a decade ago, and was also posted in another forum where more details on the project were shared (purported to be from the test manager who organised for this photo to be taken - I think this is Edwards as there is another photo of another aircraft which shows this aircraft in the background.) and that there were similar projects for other types of helo, the OH-58 kit being the most well known, but there were aspirations for a similar type of kit for Apache).

I implied Ft Eustis / FTD (or whatever they're called now) in my previous post regarding discrete facilities, but apparently this was all done between Edwards and Sikorsky.

This is what they were doing in the 80s.

There's a comment in a book about Neptune Spear saying something along the lines of: "I turned a corner and laughed, said to the guys, it's alright, we'll be fine, the air force has given us decepticons to fly in"

Thanks, very insightful and like the quip with decpticons...guess did not mean a Page Low IV pulled out of retirement or the dead lol if anyone has watched Transformers movie opening. Or perhaps meant the CV-22 Osprey which was also in the opening of the film ..

Not having read the book as yet , be very interesting and will find that one liner...however if ‘Air Force’ term used then maybe it was not army Nightstalkers operating the stealth hawk But it AFSOC all along.

Slightly digressing ...

https://www.thedrive.com/the-war-zon...ng-in-colorado


https://cimg7.ibsrv.net/gimg/pprune....12a7ca2d3.jpeg

NSDQ..

cheers

Yes, that's an interesting set of equipment. That G Chinook has lived a life.

Also, always good to see a Thundercats logo!

I have found the quote, sorry, not in a book but a long esquire article.

https://www.esquire.com/news-politic...in-laden-0313/

You can search for decepticon or its about 1/3rd down the page. Otherwise its a pretty good article. The article's real angle is the lack of support for verterans post service which is real and warranted in my opinion.

The Stealth helicopter was flown in under a Chinook and deliberately destroyed to send Russian and Chinese designers down the wrong research path for decades. ;)

FAKE, shadow near right wheel casting to the right, shadows on boxes behind casting the opposite direction.

I still say it was planted to get Pakistan off the hook for allowing the op to go ahead unhindered.

Tashengurt. I have been suggesting this as a possibility for years. (Including early posts on this forum).

There's zero evidence for that, and it would be an extraordinary - and totally unnecessary - risk during an already high risk operation.

The suggestion really doesn't stand up in any sense at all.

Decade on and we are still none the wiser ...best kept secret since the F-117A,

https://theaviationist.com/2021/05/0...new-rendering/


https://cimg3.ibsrv.net/gimg/pprune....d9e1c82c0.jpeg

Not even a reverse engineered Chinese copy.
I still say it was a red herring to let Pakistan off the hook for allowing the raid to go ahead.

All we know is this tail part was left.
https://images.app.goo.gl/g8r7DyFDqVcgixRZ6

I never got why the rest of the aircraft should be so close to some pretty standard Blackhawk? If it is intended to be stealthy wouldn't the entire airframe need to be designed in some more radical way?

Do you have anything beyond your opinion to back this?

It's a good probability that they've been buried in the desert by now and replaced with something else.

I don't think so. I have a friend who saw two of them in a hangar in Afghanistan in the hours leading up the mission.

China’s take
 

https://www.thedrive.com/the-war-zon...FA8xOWWB3YN4b8


https://cimg9.ibsrv.net/gimg/pprune....da4e148ae.jpeg

Some details of the stealthy Black Hawks from a new programme on Sky History channel.

Title:

https://www.imdb.com/title/tt14574560/

Revealed: The Hunt for Bin Laden

Lead Planner and Captain, US Navy SEAL.

"As the briefs went through the chain of command there was a sensitivity expressed on exposure to radars and discovery of the helicopters as the force was infiltrating. That shifted the conversation to using the Black Hawks that had some of the capabilities to defeat radar."


Command Master Chief, US Navy SEAL Team Six

"Very early on when we got out and saw them fly they were unstable, particularly when they came into hover and I said with all due respect I don't think that we should use these helicopters. The time to try something new is not on the most important raid arguably since WW2."


Lead Planner and Captain, US Navy SEAL.

"Another one of the factors that we had to take into account was that the aircrews flying the Black Hawks had been separate programme and didn't have a lot of time flying overseas."


Admiral McCraven, Commander Joint Special Operations Command

"..... those particular crews had been taken out of the fight for quite a while and really had just been part of research."

Absolutely not.

:}:D

Sounds like some of the lessons from Eagle Claw which I just re-read were weighed and considered as acceptable risk, or forgotten. Two of the six or so major lessons from Eagle Claw were not to use helicopter crews that had not been part of, or well integrated, into the team beforehand, and not be overly complex.... Guess stealth/surprise was deemed more important than some lessons. Salute to the folks that carried it out.

And any hard evidence to demolish Tashengurt's Occam's razor assessment? ( and mine from 2011 incidentally)

More here on the stealth specials - there were two - air quality inside the compound affecting lift available - pilot that managed to do the heavy landing had 6,000 hours on UH-60s

There was a forward refueling area in Pakistan for the return leg and that's where the backup helo for the extraction came from.

From 6:50 here:

The forward refuelling area was visible on google maps for a while - with resident US helis of various types. I think it's safe to assume 160th SOAR and their friends were familiar with it.

https://www.sandboxx.us/news/airpowe...k-helicopters/

https://www.sandboxx.us/wp-content/u...S-1024x541.jpg

cheers

Which Syria raid is that?

In the posted picture, the 2014 "Syria raid" silhouette suggests that the stealth Blackhawk has retractable gear.
Interesting, if true, although that may simply be a bit of artistic license.

I think all the images of the ones used in the OBL raid also had retractable gear - pretty much stealth 101 I’d say.

The only 2014 one I can think of in the public domain was the attempt to rescue James Foley