Bell 407 N108MF accident near Coolbaugh Township, Pennsylvania

Probable cause

The pilot’s decision to continue visual flight rules flight into instrument meteorological conditions due to self-imposed pressure to complete the trip, which resulted in impact with trees and terrain.

NTSB analysis

The surviving passenger reported that, after taking off, the weather "began to get worse," and the helicopter pilot advised the passengers that they would not be able to make it to their destination airport. The weather worsened, and the pilot decided to divert. When the surviving passenger looked out of the window, it was "misty and dusky." Shortly after, the helicopter struck trees and terrain. A witness reported observing the helicopter flying "very low" along the southbound lane of an interstate with all of its lights on just before the accident. He stated that the visibility was low, that the helicopter was under "low fog," and that it was like "pea soup" around the area.

Review of meteorological and GPS information indicated that dark night instrument meteorological conditions (IMC) existed in the accident area. Light rain was present, and low instrument flight rules conditions existed with vertical visibility of 200 feet and variable visibility of 1/2 mile. Before the accident, the helicopter was flying through this area of weather at a low altitude and an airspeed of about 30 knots. Although the pilot could have returned to the departure airport or landed in a suitable area along his route of flight, he chose to enter IMC despite the availability of safer options and was then forced to divert as the weather worsened. Also, once the helicopter had entered the weather, the sun had already set and minimal ground lighting was present in the heavily wooded area surrounding the interstate. Therefore, it is unlikely that a discernable horizon was present, which would have significantly increased the pilot's workload because it would have required him to reference the helicopter's flight instruments to maintain the helicopter's attitude, flightpath, energy state, and altitude.

Fuel was found onboard the helicopter, and no evidence of any preimpact failure or malfunction of the helicopter, drivetrain, or engine was found that would have precluded normal operation. Review of data recorded by the engine control unit revealed no hard faults or engine operational issues before the beginning of the accident sequence. Recorded data further indicated that the engine was running during the impact sequence and continued to operate for an additional 21 minutes following the accident while the helicopter was resting on its right side, which resulted in reduced oil flow and lubrication to the engine and the eventual postimpact failure of the turbine main line bearings and rotatable parts.

Although the pilot held an airline transport pilot certificate that allowed him to fly under IMC in airplanes, he did not possess an instrument helicopter rating. Review of information provided by the helicopter manufacturer revealed no evidence that the pilot had received any inadvertent IMC or instrument flight rules helicopter training when he was at its training center. Examination of the pilot's flight- and duty-time records also revealed that he was scheduled to fly a round trip for the airline he worked for the day after the accident occurred, which likely resulted in self-imposed pressure to complete the trip he was flying on the day of the accident so that he could return home and make his report time for his assigned trip on the following day.

Text from the NTSB. Open the NTSB docket for ERA13FA014 for the full record.