Martinez, Eric J., Cpl

Investigation Results: Military investigators attributed the April crash to a relatively rare aerodynamic condition known as vortex ring state, which occurs when a rotor-blade aircraft descends too rapidly while moving forward at slow speed.  It can cause such aircraft to lose lift suddenly; and in the case of the Arizona crash, it caused the Osprey to flip over and plummet to the ground, where it crashed in a fireball, investigators said.  The Marines Corps blamed the crash on ''human factors,'' concluding that the pilots apparently caused the Osprey to enter into vortex ring state by trying to land it too quickly at too steep an angle. The investigators are close to ruling out mechanical failure as the cause of the accident, which killed 19 marines, and have found no indication of recklessness by the pilot, Major John A. Brow, 39, of California.  Marine Corps officials said that while the investigation was not yet complete, the helicopter most likely lost aerodynamic lift in a phenomenon known as ''settling with power.''  Settling with power, also known as vortex ring state, occurs when a helicopter settles into the wash produced by its own rotor system.  In a rapid, nearly vertical descent, the upward flow of air at the inner portion of the rotor blades can exceed the downward flow produced by blade rotation.  At this point the aircraft can sink uncontrollably. In the case of the Osprey, the rotors may have been using such a large proportion of engine power that the aircraft had insufficient power left to slow the rate at which it was sinking in its rotor wash.