A state police helicopter pilot's decision to make a rapid descent in an attempt to see better in fog was the chief cause of the medevac crash that killed four people last year near Andrews Air Force Base, the National Transportation Safety Board concluded.

The board said Steven Bunker of Waldorf, who was killed in the Sept. 28, 2008, crash, failed to stop the descent at the proper altitude. The NTSB found no mechanical problems and determined that the helicopter's navigational instruments were working properly.

The helicopter crashed in District Heights in Prince George's County while transporting two victims of a car crash. Bunker, paramedic Mickey Lippy, emergency medical technician Tonya Mallard and patient Ashley J. Younger were killed. The other auto crash victim survived.

Bunker was trying to make an emergency landing at Andrews. The NTSB ruled that he had made an "inadequate assessment" of conditions before takeoff.

While pilot error was identified as the primary cause, the NTSB also criticized state police for poor risk management. The board also faulted the performance of Federal Aviation Administration air traffic controllers.

According to the NTSB, Bunker failed to follow proper instrument approach procedures and instead "became preoccupied with looking for the ground." Because the helicopter did not have a flight recorder, the board said it could not determine why the pilot did not make a safe landing using navigational instruments.

The crash spurred a national debate about whether medical helicopters are overused. It was one of 26 fatal medevac crashes in six years, many of them involving the transport of patients whose injuries were not considered life-threatening.

Since the crash, Maryland has revised its triage guidelines, and emergency workers are now required to talk to doctors before ordering a flight for anything but obvious medical emergencies.

The Maryland Institute for Emergency Medical Services Systems, which manages the state's trauma network, convened a panel to review medevac use, and they determined that the state could fly fewer missions without compromising patient safety.