An Army investigation cites pilot and air traffic control errors and "dark spots" in radar coverage for a nighttime helicopter collision that killed four soldiers from a Washington state base last year.

The results of an initial investigation by an aviation unit at Joint Base Lewis-McChord were released Monday. It found one pilot of a Kiowa helicopter should have seen and avoided the other.

It cited air traffic control's failure to relay information and dark spots in radio and radar coverage.

All four on board the helicopters died when they crashed over a rural county south of Puget Sound. The Army base near Tacoma, Wash., is one of the country's largest.

The News Tribune reports (http://is.gd/aemj8o ) that a separate Army unit is also investigation the December crash.


Information from: The News Tribune, http://www.thenewstribune.com