Robinson R66 N646AG accident near Noxen, Pennsylvania

Probable cause

The pilot's decision to continue VFR flight into night instrument meteorological conditions, which resulted in spatial disorientation and a loss of control.

NTSB analysis

The flight departed under visual flight rules (VFR) and then obtained VFR flight following before proceeding in a southeasterly direction. About 28 minutes after takeoff, while flying about 3,000 feet mean sea level over a sparsely populated and heavily wooded area with few ground reference lights, the flight likely encountered light rain. The pilot flew south of a wind turbine, initiated an approximate 180-degree left turn with 300 feet altitude loss, then began following a dirt road associated with the wind turbines. After completion of the turn he advised the controller, "...we're inadvertent IMC [instrument meteorological conditions], reversing..." and asked for a heading to the nearest airport. The controller asked the pilot if he wanted a vector to the nearest airport and also if the flight was in IMC, but there was no reply. The controller provided a heading for a vector to a nearby airport but the pilot did not respond. The flight continued in the same orientation following the course reversal, flying past another wind turbine before turning right; the controller again advised the pilot of the direction to the nearest airport. The pilot immediately responded that he was, "...having trouble maintaining control here." The controller informed the pilot that the nearest airport was heading 068 degrees and 8 miles away, and the recorded radar data indicates the pilot flew a north-northeasterly heading with changes in altitude noted. The comments from the pilot followed by the maneuvering (changes in altitude and heading) were consistent with the known effects of spatial disorientation. Radio and radar contact were lost; the helicopter descended on an east-northeasterly heading into trees and terrain in a heavily wooded area away from any nearby wind turbines.

Postaccident examination of the helicopter revealed extensive impact damage, although there was no evidence of a preimpact failure with the flight controls, drive line, or structure. The engine was found to operate normally and data downloaded from the engine monitoring unit indicates no evidence of preimpact failure or malfunction.

While there was no record of an official preflight weather briefing before departure, a text message from the non-instrument rated pilot to his brother approximately 1 hour before departure stating, "...Waiting out weather to fly back to [Ocean City, MD] tonight" indicates that to some extent he was aware of the weather. Had the pilot obtained an official preflight weather briefing for the intended VFR flight, the briefing specialist likely would have advised him against VFR flight due to IMC (ceiling less than 1,000 feet and visibility less than 3 miles) and mountain obscuration that were forecast to exist in the accident area.

Although the left seat occupant was a student pilot, it is unlikely the pilot-in-command was giving him instruction during the accident flight. While operation of a helicopter with decreased ceiling and visibility can be safely performed, the environmental conditions in the accident site area consisting of a sparsely populated heavily wooded area with few ground reference lights and no illumination from the moon were indicators that VFR flight should not have continued.

Text from the NTSB. Open the NTSB docket for ERA13FA336 for the full record.