Crashed Helicopter Sparks Concern Over Stealth Secrets

Hugh Pickens writes "The crash of a helicopter involved in the raid on Osama bin Laden's Pakistani hideout has prompted intense speculation about whether the aircraft was specially modified to fly stealthily — and whether its remains could offer hostile governments clues to sensitive US military technology. Remnants of the helicopter, including a nearly intact piece of its tail, suggested that the aircraft involved in the raid wasn't the typical Black Hawk flown by special-operations forces. Aviation experts who scrutinized photos of the scene say the tail had unusual features that suggested the helicopter had been extensively modified to fly quietly, while appearing less visible to radar. 'The odds are fair — based on my knowledge of the subject area — the vast majority of the special MH-60s aircraft were purpose-built to make those aircraft as stealthy as they could possibly be,' says aviation expert Jay Miller, adding that the remnants of the aircraft suggested extensive use of nonmetallic composite parts, which reflect less radar energy. Experts also say the tail rotor's design suggested an effort to reduce the 'acoustic signature' (video) of the helicopters to make them fly more quietly."

Comments

Yes it was modifed

[LWATCDR]

Or a new design. That tail rotor is not from any know US or even NATO Helicopter. How much was compromised? Maybe some materials It will depend on if Pakistan gives it back or not. They will probably pass some parts onto China since they are working with them on new aircraft. Or we will sell them some more F16s cheap if they give back to US.

Hardly secret or surprising

[fridaynightsmoke]

The fact that civilian aviation experts were able to look at the pictures and say "gee, that's a so-and-so modification to reduce noise" suggests to me that this is hardly top-secret technology. Also, the fact that special forces have relatively stealthy helicopters is hardly surprising.

What next; controversy about a crashed police car 'revealing' secret tuning and suspension modifications?

The reason it crashed too?

[goombah99]

According the NYtimes the reason it crashed was not mechanical failure but lack of lift. two reasons were given 1) thin air 2) the walls of the compound created a vortex. So apparently just some modestly walls to guide air will reduce the lift enough to crash this thing. I wonder how it is supposed to land between buildings? I wonder if perhaps the noise reduction and stealth features came at a price of reduced performance.

creepy and exciting tech

[smellsofbikes]

The first time I heard about this whole mission, I thought, whoah, American helicopters managed to fly 150 km into Pakistan without being noticed? Pakistan isn't a slouch when it comes to military equipment: they've fought several wars with India, and are used to trying to track some of the finest military hardware in the world. Yet two helicopters flew in, invisibly. It sounds like they were supported by two Chinooks, that came in a bit later, and those *were* seen by the Pakistani air defense, but the first group in weren't seen. A lot of other countries are going to want to figure out how we did this.

There have been a lot of US projects in making low-observable helicopters, from the modified Hughes OH6 Loach used to surreptitiously place wiretaps on lines during Vietnam, that also used increased numbers of blades, and the cancelled RAH-66 Comanche, that was supposed to be quiet and have a vastly reduced radar signature. The ones used Monday are probably Blackhawks modified based on the stuff learned from the Comanche, but they could be completely new aircraft: the descriptions of the amount of personnel and material taken in are at the very edge of what two stock Blackhawks could carry, and adding lots of stealth technology adds a *lot* of weight.

Among other interesting things I've read and observed: the stock Blackhawk is manufactured with sheets of aluminum riveted together along the edges, like most planes. The pictures show rivetless construction, and in one picture it looks like there's a long weld seam that appears to have been done by hand rather than machine, making me think there are a very small number of prototypes of this. I also saw a link somewhere, that I can't find now, to a press release by a company who was adding small servos into the collector linkages that added continuous slight variance to the blade angle, to minimize noise by distributing it across different frequencies, which seems pretty cool. I've even seen a few claims that the whole aircraft was covered in material that could emit low levels of light, to blend it visually against a lighted sky (a technique used back in WWII by putting headlights on the leading edges of aircraft wings so that they could dive-bomb submarines without being seen until it was too late for the sub to dive. This was distinct from the british Leigh lights, that were used in after-dark attacks along with radar.)

I'm betting a whole lot of people are bidding on the wreckage that was recovered -- which is, itself, surprising, at least to me, because it sounds like the commandoes were able to completely destroy the whole main fuselage, leaving just the tail. Under the hurried circumstances that's pretty surprising. (I wouldn't be surprised to find out they actually hooked it to one of the Chinooks and dragged it out along with them.)

Re:Cutting edge

[dcherryholmes]

I'm not expert in this stuff, but I did do some time on submarines and participated in refueling overhauls and decommissions. When the sub is in drydock the screw is kept covered with a tarp at all times, lest somebody just see the shape of it and glean anti-cavitation tech. So it is plausible to me that just seeing the shape of one of the rotors would be significant.

Re:Cutting edge

[Shivetya]

The real achievement wasn't the helicopters, it was flying from their station in Afghanistan without being picked up by Pakistan's military. A lot of that had to do with know where the coverage was and the terrain combined with great flying and planning. Never underestimate the skill of those flying these machines. Flying helicopters in the dark at the levels and speeds they were moving isn't for the feint at heart.

The explosives were most likely done to break up certain shapes and destroy electronics. I doubt the materials themselves used to skin the helicopter are as important as compared to the shape of the various components of the copter.