Prime Chance was in 1987/88. I know of MH-60A, Little Bird and KW being directly involved. I have not heard of Chinook participation, but that doesn't mean it didn't happen (adrake2's the expert on
Prime Chance around here. Last I heard, he was building a "Velcro Hawk" from that op for the S-70 GB. They so-called "Grayhawks" were painted as such to blend in with SH-60s on decks to hide them from curious eyes when going thru the Suez and Staits of Hormuz (sp?).
The photo I'm referring to was taken in the summer of 2003 at McGee-Tyson outside of Knoxville. http://www.airliners.net/open.file/370097/L/
Also in 2003, dninness shot these pix in Concord NH:
http://www.emmasweb.com/images/DCP05503.jpg
http://www.emmasweb.com/images/DCP05504.jpg
http://www.emmasweb.com/images/DCP05505.jpg
http://www.emmasweb.com/images/DCP05506.jpg
http://www.emmasweb.com/images/DCP05508.jpg
http://www.emmasweb.com/images/DCP05509.jpg
There was a lot of speculation as to why that Chinook and Kilo were gray, ranging from it being a one-off test to another situation where they had to hide in plain site again with Navy aircraft (HH-60/CH-46?)
And after seeing the video albymoore posted of the SC ARNG Apaches, I can totally see the value of the scheme. It doesn't make the aircraft invisible (nothing at that range would), but it does mess with your ability to focus in on and judge the range and orientation of the aircraft. The Marines have been using that scheme for nearly 15 years now. I see AF and USMC C-130s here all the time and those grays do the same thing.