Reply #2: Secret US 'Jedi' ghost-copters kept out of bin Laden raid

[jakeXT]

Downed Stealth Hawk was actually second-rate kit
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The phrase "invisible to radar" doesn't mean much when used by a non-aerospace journalist describing a screenwriter's book. It will signify that the secret super-copters - if they really exist in a distinct sense - have more and better low-observable radar tech than the downed Stealth Hawk. However, even multi-hundred-million-dollar stealth fighters aren't actually invisible to radar and the job of concealing a helicopter is hugely more difficult than hiding a jet. The Ghost Hawk might, like the Stealth Hawk, have special blades, and shields over particular radar traps such as rotor hubs. It might perhaps make use of special radar-absorbent coatings, not particularly in evidence on the Abottabad wreck. But like any other helicopter the Ghost Hawk's primary means of avoiding detection by radar will be flying extremely low, below the horizon of ground radar stations.
Not blowing hot air, well, not that much

"Zero electromagnetic radiation" could mean that Pfarrer believes the Ghost Hawk doesn't emit heat, which would be useful if true for evading detection by infrared-search-and-track (IRST) networks or the seeker heads of shoulder fired anti-aircraft missiles. However total suppression of heat signature in an aircraft which must be powered by turboshaft engines is impossible. It might be, however, that the Ghost Hawk uses specially designed exhausts - and perhaps dumps some heat into its fuel, like a stealth fighter - to cut its thermal signature significantly below that of a normal chopper.

However the "zero electromagnetic radiation" comment is at least as likely to refer to various other cunning stealth technologies developed for the latest US fighters and bombers, allowing them to communicate and use radar without giving their presence away. In order to achieve this, radars and communications aboard such aircraft as the F-22 Raptor and B-2 Spirit make use of various fiendishly cunning frequency-hopping techniques. Without this sort of tech, achieving a stealthy design isn't very useful as an enemy with electronic-warfare receivers will still be able to pick up your transmissions even if he can't see you on radar or IRST.

It is in this lesser-known field of stealth technology that the US advantage is thought to be greatest: other nations can build an aircraft with a stealthy shape - this is comparatively simple, and has much more effect than coatings, materials and infrared suppression - but nobody can make silent radars and radios like the secret boffins of the USA. Special-ops choppers need radar as well as comms, as it is used to avoid crashing into the ground when flying low-level at night or in poor visibility: this is admitted in the case of the publicly avowed MH-60K special ops Blackhawk. An undetectable ground-following radar would be an obvious piece of kit for the US spec-ops command to request.

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http://www.theregister.co.uk/2011/11/08/jedi_ghost_seal_copters/