GAITHERSBURG (AP) – A small plane that crashed into a Maryland electricity transmission tower last month was flying below minimum altitudes while approaching an airport in foggy night-time conditions, according to a preliminary report on the crash.
The pilot and passenger were seriously injured and the Mooney M20J was substantially damaged when it hit a tower supporting high-tension lines on November 27, knocking out power to tens of thousands of area customers.
The plane was left dangling 30 metres (m) above the ground, according to the National Transportation Safety Board’s preliminary report released on Monday. The report includes factual information but not a probable cause. That is typically included in a final report, which could take a year or two to complete, according to the NTSB.
The plane was operating on an instrument flight rules flight plan, which is typically used during reduced visibility, as it returned to the Montgomery County Airpark in Gaithersburg from White Plains, New York, the report states. Visibility in the fog was two kilometres (km).
Air traffic control communications showed that the pilot, identified by state police as Patrick Merkle, 66, of Washington, DC, was advised to expect one approach procedure, but he preferred another, the report stated. An air traffic controller directed Merkle to a spot about 21km from the airport, but the plane made a wrong turn.
As the controller provided numerous course corrections, the pilot made a “series of left and right turns, near course reversals, or continued established headings as the controller repeatedly requested that the pilot turn to a different heading”.
At one point, he told the controller that he had entered the wrong waypoint into his system and was correcting it, the report stated.
Around that time, another airplane asked to be diverted to another airport because of reduced visibility. As Merkle’s plane approached the airport, it was below the minimum altitude at three waypoints, according to the report. At the last of those three waypoints, it was as low as 145m mean sea level, the report said. The airport’s published elevation is 164m mean sea level. When it crashed, the plane was suspended at an elevation of 183m mean sea level, the report stated.
Merkle and the passenger were stranded in the aircraft for more than six hours, until crews secured the plane to the tower, officials said.