SALINA, Pa.—Federal investigators say pilot error caused the crash of a plane into a western Pennsylvania home almost two years ago that killed both men aboard and narrowly missing a man sleeping on his couch with his dog.

The National Transportation Safety Board said Edward Sobota, 65, of Unity was completing a "multi-engine instrument proficiency check-ride" with a certified flight examiner when the twin-engine plane crashed in Bell Township in August 2010, the Pittsburgh Tribune-Review reported Saturday (http://bit.ly/I325Rd ).

"The pilot's loss of control of the airplane during low-airspeed airwork and his failure to promptly recover the airplane from the aerodynamic stall, which resulted in a spin," caused the crash, the report. The safety board suggested that Sobota's lack of recent flight experience with an airplane of that make and model were contributing factors, the paper said.

Sobota and Theodore Kokolis, 66, of Moon Township were killed in the crash of the BE58 about 30 miles northeast of Pittsburgh. No one on the ground was hurt. Homeowner Steve Yanko, asleep in the family room when the plane came through the roof, escaped through a door on the ground floor and was uninjured. Officials said the family dog, Asia, also got out safely.

Authorities said the plane had been properly inspected in March 2010 and had an unblemished maintenance history

The report said Sobota had owned the same plane two decades earlier and had repurchased it four days before the crash, and had also done three full-stop landings two days before the accident. But investigators said that since Subota had owned the plane, the engines had been modified with vortex generators that decreased the airplane's suggested minimum-control airspeed from 81 knots to 74 knots.

"Based on the airplane's decreasing airspeed and nearly level altitude, the pilot was likely performing either imminent stall or simulated loss of engine power airwork before the airplane aerodynamically stalled, and then entered a spin," the report said. "Because the plane was equipped with only a throw-over control yoke system, the (flight examiner) had limited ability to assist in the recovery of the airplane."

Investigators said it was impossible to determine which low-speed maneuver Sobota was performing, but radar data suggested a routine test in which a power reduction takes place in one engine. Officials theorize that during the demonstration the airplane unexpectedly lost directional control "earlier than expected because the actual flight speed modifications were unknown and the air speed indicator was improperly marked."

As a result of the crash, the agency has ordered aircraft with the same flight speed indicators to be inspected and updated, when necessary.

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Information from: Pittsburgh Tribune-Review, http://pghtrib.com