NTSB Final Report: Forkston, PA

Analysis

The pilot departed from his home airport about 13 minutes after sunset under visual flight rules and in visual meteorological conditions. He was not instrument-rated in helicopters, and the helicopter he owned was not approved for flight in instrument conditions. About 1 hour into the flight, the pilot likely encountered snow showers and instrument meteorological conditions that were forecast and moving through the area. Radar data showed that, after entering the area of weather, the pilot began a right, descending turn and the helicopter crashed in a rural, wooded area. The helicopter was destroyed by impact forces and a postimpact fire.

Postaccident examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. There was no evidence that the pilot obtained a weather briefing or reviewed the weather prior to or during the flight.

The dark night conditions under the likely overcast skies, the obscuration of the snow showers, and the lack of terrestrial illumination due to being over a remote and wooded area were all conducive to the formation of spatial disorientation. The pilot’s lack of an instrument rating in helicopters, and the helicopter’s lack of equipage for flight instrument meteorological conditions, would also have increased the likelihood of the pilot becoming spatially disoriented. The descending right turn exhibited by the helicopter in the final moments of the flight were consistent with the pilot experiencing spatial disorientation and a subsequent loss of control.

Probable Cause and Findings

Findings

History of Flight

On April 22, 2021, about 2104 eastern daylight time, a Robinson Helicopter R44, N4055N, was destroyed when it was involved in an accident near Forkston, Pennsylvania. The pilot was fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to radar track data from the Federal Aviation Administration, the pilot took off from Allentown Queen City Municipal Airport (XLL), Allentown, Pennsylvania about 2010. He contacted Allentown approach control at 2011 and requested VFR flight-following to Bradford County Airport (N27), Towanda, Pennsylvania. After departure, the helicopter proceeded to the northwest, climbing to a cruise altitude between 3,000 and 4,000 ft above mean sea level (msl), remaining closer to 3,000 ft msl for most of the flight. At 2028, Allentown approach directed the pilot to contact Wilkes-Barre (AVP) approach. The pilot checked in with AVP approach and was issued the local altimeter setting. Shortly after passing Kasson Brook, Pennsylvania, the helicopter made a slight right turn, then entered a right, descending spiral until radar contact was lost about 2104 (see figure 1). The last recorded radar location was near the accident site location. No distress calls were received from the pilot prior to the accident.

Pilot Information

Aircraft and Owner/Operator Information

The helicopter was not approved for flight in instrument meteorological conditions.

The National Weather Service (NWS) Surface Analysis Chart centered over the eastern United States for 2000 depicted a trough located from northcentral Pennsylvania to southwestern Pennsylvania. There were no low- or high-pressure systems located near the accident site. The accident site was located east of the surface trough. Troughs can act as lifting mechanisms to help produce clouds and precipitation if sufficient moisture is present.

Greater Binghamton, New York Airport (BGM) was located 44 miles north of the accident site at an elevation of 1,636 ft. The 2053 observation included wind from 310° at 5 knots, 1 ½ statute miles visibility, with light snow, a broken ceiling at 4,300 ft, and overcast skies at 5,500 ft. The 2121 observation included wind from 300° at 8 knots, 1 ½ statute miles visibility, with light snow and mist, a broken ceiling at 2,900 ft, broken skies at 3,800 ft, and overcast skies at 5,000 ft.

A review of recorded Doppler radar data revealed a band of precipitation (snow showers) moving across the area of the accident site at the accident time. The NWS office in Binghamton issued an area forecast at 1953 for the area that included lake effect snow showers moving across the region. AIRMETs active at the time included mountain obscuration, moderate turbulence, and moderate icing.

The accident pilot did not request weather information from Leidos Flight Service or ForeFlight. There is no record of the pilot receiving or retrieving any other weather information before or during the accident flight.

Wreckage and Impact Information

The helicopter collided with trees and terrain in a remote, wooded area. The wreckage was recovered to a storage facility where an examination was conducted by a National Transportation Safety Board (NTSB) air safety investigator.

The aluminum and fiberglass structure of the fuselage and cabin were consumed by a postaccident fire. The forward end of the tailcone and empennage were mostly consumed by fire. The horizontal and vertical firewalls were deformed from impact and heat distress. The cyclic, collective, and antitorque pedals were fractured, deformed, and thermally damaged and were no longer attached to the structure.

The fuel tank bladders and shells were completely consumed by postaccident fire. Both filler caps were secure on their filler necks. Both finger strainers were clean and unobstructed. The fuel lines and hoses were damaged by postaccident fire. The fuel valve was found in the ON position.

The main rotor hub remained attached to the driveshaft. Both main rotor blades were cut by recovery personnel. Both blades exhibited impact damage to the leading edges and multiple fractures were observed throughout the length of the blades. The tail rotor blades sustained impact and thermal damage.

Most of the flight control tubes in the cabin and airframe areas were consumed by postaccident fire. All connections to the main rotor controls were accounted for, and all but three of the rod ends for the tail rotor controls were accounted for. The visible disconnects at the rod ends displayed either overload or thermal damage. The hydraulic servos moved smoothly by hand.

The accessory case was removed, and the crankshaft gear dowel pin was sheared, consistent with sudden stoppage of the accessory gears at impact. The crankshaft gear bolt was removed and was unbroken. The bolt head was damaged, consistent with contact with the oil pump drive. The first 3/16 inch of the bolt threads were damaged.

The crankshaft gear, crankshaft gear bolt, and safety washer were sent to the NTSB Materials Laboratory for examination. By design, the crankshaft gear contained a hole in its pilot flange that interfaced with an alignment dowel that was press-fit into a counterbored recess on the aft end of the crankshaft. The alignment dowel had fractured, and the separated piece of the dowel was captured in the pilot flange hole. All components (except the tip of the bolt) had dark-tinted surfaces, including the dowel fragment’s fracture surface, consistent with exposure to elevated temperatures. The tip of the bolt had a shiny appearance and stripped threads, consistent with damage during extraction of the bolt. All surfaces were examined for indications of burnishing, rubbing, or wear, but none were found. The dowel’s fracture surface had a flat, featureless appearance, with no apparent crack arrest marks. Shear lips were observed along the radially inward and outward edges of the fracture surface. The chamfer around the pilot flange hole exhibited deformation and metal transfer at the leading edge (the edge that leads during rotating of the crankshaft/gear assembly). The features were consistent with an overstress fracture of the dowel in shear and bending.Postaccident examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.

Additional Information

VFR into IMC

In April 2003, the Federal Aviation Administration (FAA) published Advisory Circular 61-134, General Aviation Controlled Flight into Terrain Awareness. The circular stated in part:

According to autopsy report from the Office of the Coroner, Wyoming County, Pennsylvania, the cause of death of the pilot was blunt force trauma due to helicopter crash and the manner of death was accident. The examination to identify any natural disease was limited by extensive trauma.

Toxicology testing performed by the FAA Forensic Sciences Laboratory detected ethanol in the pilot’s liver tissue at 0.048 grams per hectogram (gm/hg) and n-butanol in the pilot’s liver tissue; no other tested for drugs were detected in his muscle tissue.

Ethanol is a social drug commonly consumed by drinking beer, wine, or liquor. It acts as a central nervous system depressant; it impairs judgment, psychomotor functioning, and vigilance. Ethanol is water soluble, and after absorption it quickly and uniformly distributes throughout the body’s tissues and fluids. The distribution pattern parallels water content and blood supply of the tissue. Ethanol can be produced after death by microbial activity, sometimes in conjunction with other alcohols such as butanol. Extensive trauma increases the spread of bacteria and raises the risk of ethanol production after death.

Preventing Similar Accidents

Reduced Visual References Require Vigilance

Preflight weather briefings are critical to safe flight. In-flight, weather information can also help pilots make decisions, as can in-cockpit weather equipment that can supplement official information. In- cockpit equipment requires an understanding of the features and limitations.

We often see pilots who decide to turn back after they have already encountered weather; that is too late. Pilot's shouldn't allow a situation to become dangerous before deciding to act. Additionally, air traffic controllers are there to help; be honest with them about your situation and ask for help.

Even when flying at night, visual weather conditions can also be challenging. Remote areas with limited ground lighting provide limited visual reference cues for pilots, which can be disorienting or render rising terrain visually imperceptible. Topographic references can help pilots become more familiar with the terrain. The use of instruments, if pilots are proficient, can also help pilots navigate these challenging areas.

See http://www.ntsb.gov/safety/safety-alerts/documents/SA_020.pdf for additional resources.

The NTSB presents this information to prevent recurrence of similar accidents. Note that this should not be considered guidance from the regulator, nor does this supersede existing FAA Regulations (FARs).

Administrative Information