(Adds detail, concerns about the pilots)

By John Crawley

WASHINGTON, Nov 18 (Reuters) - Federal investigators on Tuesday blamed crew error for the plane crash in Minnesota last year that killed U.S. Sen. Paul Wellstone, his wife, daughter and the other five people aboard.

The National Transportation Safety Board said the two-member crew of the Beech King Air A100 badly mishandled the landing approach to tiny Eveleth airport and did not follow proper procedures to correct problems before a stall caused the Oct. 25, 2002, crash.

Wellstone, 58, a Minnesota Democrat who was campaigning for re-election, was en route with his party to a funeral in northern Minnesota when the twin-engine turboprop crashed into a swamp 2 miles (3.2 km) from the airport.

The crash and fire obliterated the aircraft and eliminated much of the useful physical evidence. The plane operated by Aviation Charter Inc. of Eden Prairie, Minnesota, was not equipped with cockpit data or voice recorders. Those devices were not required on planes of that size.

While many questions remain unanswered, investigators believe they have pieced together an accurate account of the crash based on radar data, simulator tests, interviews and air traffic control communications.

Investigators dismissed early speculation that weather was a major factor. But they said overcast skies may have hampered the crew's ability to see the airport. Also, evidence recovered at the scene showed no mechanical problems with the plane.

The safety board concluded in its finding of probable cause that Capt. Richard Conry and co-pilot Michael Guess failed to maintain the appropriate course and approach configuration during the later stages of the flight.

Investigators said the crew allowed air speed to fall well below acceptable limits, which led to an engine stall and the crash. The safety board said the crew should have abandoned its approach and tried another landing attempt.

While it was not determined why the crew mishandled the aircraft, investigators found that both pilots had problems in the cockpit before. "There was a general history of below-average capability and concerns about performance," said safety board chairman Ellen Engleman.

For instance, senior investigators said they were told that co-pilots on previous flights had to override errors made by Conry or explain mistakes he had made.

The safety board also said Aviation Charter did not provide crews with adequate guidance on how to recover from stalls and was not doing a good job of keeping pilots current on its operating procedures.

Investigators also said Federal Aviation Administration oversight of the company was insufficient.

Aviation Charter had no comment on the findings, while the FAA said it would review criticism of its oversight.