The Mooney that crashed into power lines on November 27 during a night instrument approach to Montgomery County Airpark (KGAI) in Gaithersburg, Maryland, had a properly functioning altimeter, according to an NTSB preliminary report. Both the pilot and passenger survived after the airplane hung suspended 100 feet above the ground in high-voltage electric lines for nearly eight hours before they were rescued. The accident knocked out power for more than seven hours for an estimated 80,000 residents of the Washington, D.C. suburb. Weather at the time was reported as a 200-foot-ceiling and 1.25 miles visibility in fog, with a convective sigmet issued for the area.
The instrument-rated pilot of the 1977 Mooney M20J called 911 after hitting and becoming entangled in the wires and supporting tower structure, telling the operator, “I got a little lower than I should have” and would later describe conditions to a local media outlet as “pea soup” and expressed concerns about his altimeter’s accuracy. However, post-crash testing under the supervision of the NTSB found the altimeter was “well within the test allowable error at all ranges.”
An analysis of the aircraft’s ADS-B data by the NTSB paints a picture of an approach that was repeatedly off-course, off-altitude, and continually being issued corrective course instructions by ATC. “The controller provided numerous heading changes and direct clearances to waypoints on the RNAV (GPS) RWY 14 approach procedure; however, the pilot made a series of left and right turns, near course reversals, or continued on established headings as the controller repeatedly requested that the pilot turn to a different heading,” said the NTSB.
A recording of the exchanges between ATC and the pilot with a map and data overlay is available on YouTube.
Concurrent to the Mooney’s approach, another aircraft inbound to KGAI “announced that visibility was below minima and requested diversion to another airport,” according to the NTSB.