N724MTBombardier BD-700-1A10 · 2024

On March 24, 2011, about 1623 eastern daylight time, a Cessna A185F, N724MT, operated by the Maine Department of Inland Fisheries and Wildlife, was substantially damaged when it impacted frozen Clear Lake about 30 nautical miles southwest of Ashland, Maine. The certificated commercial pilot/Maine Game Warden was fatally injured. Instrument meteorological conditions (IMC) prevailed and no flight plan was filed for the public-use flight.

According to the operator, the pilot had taken the airplane he customarily flew to Greenville, Maine (3B1), for routine maintenance. He then picked up the ski-equipped accident airplane and returned to his patrol area. A game warden on the ground at Clear Lake reported overhearing the pilot attempting to call the local dispatch center to report that he was having problems with his radio. The game warden was able to relay the message for the pilot using his radio, and shortly after, the pilot landed on Clear Lake and met with the game warden.

The game warden stated that he and the pilot talked for approximately 30 minutes before receiving a radio call from another game warden whose snowmobile was stuck on nearby Eagle Lake. The pilot then departed Clear Lake to assist the game warden with his snowmobile.

The pilot arrived to assist the warden stranded on Eagle Lake by landing on adjacent Chamberlain Lake, where he picked up the other game warden. They then both flew to where the game warden’s truck was parked, picked up tools, and departed back to where the snowmobile was located. The pilot and game warden freed the snowmobile out of approximately three feet of snow and slush. During the recovery, the pilot's boots had been inundated with an icy slush and following the recovery the pilot was "breathing heavily" from exertion. The pilot and the game warden then talked for approximately 10 minutes prior to the pilot’s departure, and during that time the pilot's breathing returned to normal. The warden reported that almost immediately after the airplane departed, visibility was reduced to less than 1/2-mile due to snow.

Both wardens reported isolated areas of heavy snow moving through the area throughout the day of the accident.

According to preliminary information provided by the operator, the pilot was reported missing about 2000, when he did not return to his home as expected. A subsequent search ensued, and the wreckage was located about 0850 the following day.

The pilot was employed by the Maine Department of Inland Fisheries and Wildlife, Maine Warden Service as Game Warden/Pilot. He held a commercial pilot certificate with ratings for airplane single engine land and sea, and instrument airplane. He held a second class medical certificate, which was issued on June 14, 2010 with the limitation "must wear corrective lenses." On that date, the pilot reported 3,130 total hours of flight experience.

The pilot provided updated personal information to the operator on March 13, 2011. In that report the pilot stated he obtained his commercial pilot certificate and instrument rating in 2004, and reported 3,548 total hours of pilot-in-command flight experience. He also reported 3,146 total hours of flight experience in the Cessna 185, 376 hours of which were accumulated in the 12 months preceding the date of the application. The pilot also reported 10, 70, and 2 hours of instrument flight experience in the Beechcraft BE-19, Cessna 172, and Cessna 185, respectively. The pilot's most recent flight review and instrument proficiency check (IPC) were completed on April 1, 2010.

Review of personal flight logs provided by the operator showed entries for flights completed through September 22, 2010. A log entry dated April 1, 2010 noted a 1.2 hour flight in a Cessna 185, 0.7 hours of which were logged as simulated instrument flight experience. The remark for the log entry noted, "Flight Review Completed, IPC Check Completed." Additionally, 3 takeoffs and landings were logged under their respective columns, and no instrument approaches were logged under its respective column.

Additional flight logs provided by the operator showed that the pilot had accumulated 19 additional flight hours between the time the above referenced report to the operator was made and the date of the accident, all of which were logged in a Cessna 185.

The National Weather Service (NWS) Surface Analysis Chart valid at 1400 depicted a low pressure system off the New England coast with an occluded front extending northeast from the low, curving southward and turning into a cold front. A secondary trough of low pressure was depicted extending northwestward across Maine and Quebec, Canada. A cold core high pressure system was located to the northwest over the Hudson Bay of Canada. The station models surrounding the accident site indicated northerly winds at 5 to 10 knots, scattered to broken clouds, temperatures around or slightly below 0 degrees Celsius (C), with dew point temperatures several degrees lower. The subsequent chart at 1700 depicted similar conditions with northerly wind at 10 knots or less, scattered to broken clouds, with temperatures in the near 0 degrees C.

The northeast section of the NWS Weather Depiction Chart for 1500 depicted an area of IMC over northwest and southwest Maine into Quebec province. Surrounding that area was a larger area of marginal visual meteorological conditions over the western portion of Maine and the accident site, into northern Vermont, New Hampshire, and northeast New York State. Visual meteorological conditions were depicted over the eastern portion of Maine.

The weather reported at Ilco Landing Area Seaplane Base (ME04), located about 16 miles west of the accident site, at 1625, included variable winds at 3 knots, temperature -3 degrees C, dewpoint -4 degrees C, and an altimeter setting of 29.67 inches of mercury (inHg). The station reported that less than 0.01 inches of precipitation had fallen during the previous hour. The station was not equipped with a precipitation discriminator, and could not report visibility, weather, or cloud conditions.

The Geostationary Operational Environmental Satellite number 13 visible image at 1615 depicted a broken area of low cumulus clouds over northern Maine, oriented in an open cellular pattern. The accident site was located near the leading edge of cumulus cloud. The infrared image at the same time depicted a radiative cloud top temperature of 260° Kelvin (K) or -13.16° C, which corresponded to cloud tops near 5,000 feet.

The closest NWS Weather Surveillance Radar-1988, Doppler (WSR-88D) was located at Caribou (KCBW), Maine located approximately 62 miles east-southeast of the accident site. The KCBW WSR-88D base reflectivity image for the 0.5° elevation scan completed at 1617:53 depicted scattered areas of very light intensity echoes from 5 to 24 decibels (dBZ) across the region, with the accident site located under echoes of approximately 20 dBZ. Given the temperature profile, the echoes were likely associated with scattered snow showers or snow squalls. A subsequent scan completed at 1627:32 showed that the radar echo over the accident site remained at 20 to 24 dBZ and had moved southward during that time.

The NWS Area forecast valid for the time of the accident was issued at 1345, and was valid until 0200 on March 25, 2011. The forecast for Maine expected broken clouds at 4,000 feet with tops to 9,000 feet with occasional light snow showers. The outlook from 0200 through 0800 was for VMC to prevail. The NWS also issued advisories current for Maine about the time of the accident, which included AIRMET Sierra update 2 for mountain obscuration, which bounded an area just south of the accident site, and AIRMET Zulu, which encompassed the accident site, for icing conditions below 8,000 feet.

According to the operator, the airplane was equipped with a Garmin GPSMAP 496 handheld global positioning system receiver with an optional satellite-based weather data receiver. The unit had a current subscription that would have enabled the display of numerous NWS weather products including aviation routine weather reports (METARs), SIGMETs, AIRMETs, and Next Generation Radar (NEXRAD) graphic overlays.

The wreckage was located on frozen, snow-covered Clear Lake at 46 degrees, 30.95 minutes north latitude, 69 degrees, 7.97 minutes west longitude. There was an odor of fuel and evidence of fuel staining at the scene, and all major components of the airplane were accounted for.

The initial impact point was identified by an area of broken ice approximately 10 feet long and 6 feet in diameter. The wreckage path was oriented approximately 100 degrees magnetic and was approximately 350 feet in length. The airplane’s right wingtip, right wing strut, right horizontal stabilizer and elevator, engine intake air filter, right main landing gear, along with other debris from the airplane, were found along the path. The main wreckage came to rest oriented approximately 60 degrees magnetic.

The right wing was separated from the wing root but remained attached to the fuselage by control cables. The outboard two-thirds of the wing exhibited significant crush damage and was bent upward and aft about the mid-point of the wing's span. The aileron and flap remained attached. Measurement of the flap actuator showed a position that correlated to a flap position between 10 and 20 degrees. The left wing remained attached to the cabin roof, and exhibited relatively little structural distortion and impact-related damage relative to the right wing. The aileron and flap remained attached to the wing. The left horizontal stabilizer and elevator remained attached. The right horizontal stabilizer and elevator were largely separated from the airplane. Flight control continuity was traced through overload separations from the cockpit area to each flight control surface. Measurement of the stabilator trim actuator correlated to between 5 and 6 degrees of stabilator deflection in the leading edge down or nose-up pitch direction.

The cockpit and cabin exhibited extensive impact damage. The altimeter kollsman window was set to 29.67 inHg. The rotating beacon, navigation lights, and pitot heat switches were all in the "ON" position.

The vacuum pump was removed from the engine and examination of the drive coupling revealed that it had sheared. The parting line of the injection-molded plastic coupling exhibited permanent torsional deformation. The fracture face of the flex coupling was examined, and a portion of the fracture surface displayed a flat region with crack arrest features and curved ratchet marks along the circumference of the flat region. The remainder of the fracture displayed elongated fibrils, which showed signs of directional elongation consistent with torsional loading. Disassembly of the pump showed that two of the six veins exhibited small areas of damage on the rubbing face toward the forward end of the veins. The rotor showed no damage while the housing showed five faint slap marks consistent in size and shape with the veins. The shaft assembly rotated smoothly, but with a smooth resistance to rotation. Internal examination of the vacuum driven attitude and directional gyros recovered revealed no definitive signatures of their rotational state at impact.

The airplane was equipped with a three-blade, constant speed propeller, which was separated from the engine by a fracture of the crankshaft aft of the forward face of the engine case. The propeller came to rest approximately 20 feet forward of the main wreckage. Two blades exhibited s-bending and significant leading edge gouging. The third blade was bent aft outboard about one-third of its span.

The engine was separated from the airframe and crankshaft continuity was confirmed from the forward fracture of the crankshaft to the rear accessories and valvetrain. Borescope inspection of each cylinder revealed no abnormal combustion deposits, and each of the spark plugs exhibited normal wear and was light gray in color. The induction air filter and all of the fuel system screens were clean and absent of debris. Timing of the magnetos was confirmed and rotation of each magneto drive produced spark at each terminal lead.

A handheld global positioning system receiver (GPS) was recovered from the wreckage and retained for examination at the NTSB Vehicle Recorders Laboratory.

An autopsy was performed on the pilot by the Office of the Chief Medical Examiner, Augusta, Maine. The cause of death was listed as "blunt injuries."

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological on the pilot. The toxicology screening was negative for the presence carbon monoxide, cyanide, ethanol, or drugs.

Handheld GPS Receiver Data

The Garmin GPSMAP 496 battery-powered portable GPS receiver recovered from the wreckage was examined in the NTSB Vehicle Recorders Laboratory. Exterior examination revealed that the unit had sustained major damage from impact forces. An internal inspection was performed. The liquid crystal display (LCD) and keypad were damaged beyond repair, and the underlying radio frequency shield was bent. Due to damage to the unit, full repair was not practicable. The main printed circuit board was removed from the accident unit and placed into a surrogate GPSMAP 496 case, LCD, and soft-key subassembly. Power was applied to the accident unit main printed circuit board after making all practicable repairs and recorded waypoint, route, and track log data was successfully downloaded from the unit via the universal serial bus port.

A review of the track log data revealed a series of flights consistent with the statements provided by the two game wardens that had interacted with the pilot before the accident, including the flight from Clear Lake to Chamberlain Lake, and the accident flight.

The final flight track recorded by the GPS began at 1613, as the airplane departed from Chamberlain Lake, turned to the northeast, and climbed to about 1,500 feet GPS altitude. Extrapolation of the airplane's established track showed that the airplane was heading toward Eagle Lake, Maine, where the pilot and airplane were based. About 1619, the airplane's track turned about 20 degrees left of its previously established track, toward Clear Lake. A survey of the terrain elevation directly below the airplane's track for this portion of the flight showed that it varied from around 980 feet to nearly 1,350 feet, while the airplane's GPS altitude remained around 1,500 feet.

At 1622:13, the airplane began slowing from the previously established approximate groundspeed of 120 knots, to about 110 knots 30 seconds later. At 1622:30, the airplane's established track turned about 40 degrees left, when it was about 1/2-mile south of Clear Lake. At 1622:49, the airplane crossed the southern bank of Clear Lake, at a GPS altitude of 1,480 feet. The final three GPS positions were recorded between 1622:55 and 1622:59. During that time the GPS altitude decreased from 1,481 feet, to 1,423 feet, and finally to 1,297 feet, with a calculated descent rate between the three points of 1,740 feet per minute and 3,780 feet per minute. During that time period the track also turned from generally northwest to east, at an average turn rate of 11 degrees per second.

The initial impact point was about 230 feet southeast of the final GPS position, at an elevation of 1,197 feet, along a heading consistent with the ground track established between the final two GPS positions.

Automated Flight Following Data

The accident airplane was equipped with an automated flight following system, which reported the airplane's position via a one-way satellite message transmission every 10 minutes. Review of the data provided from the system revealed that the airplane's position was recorded once during the accident flight at 1615:36, about 7 minutes prior to, and 13.5 nautical miles southwest of the accident site.

Operator Policy Document

The operator published Aviation Policy #30 with a stated purpose of creating a uniform policy to govern the use of their aircraft. Under the policy, pilots were charged with the duty to, "accept and conduct only those flights that can be made in a safe and efficient manner." The document further stated that administrative flights will be made in accordance with Title 14 Code of Federal Regulations (CFR) Parts 91 and 61, while all other flights were to be considered public use. When operating under instrument flight rules, each pilot was to ensure that they had the recent flight experience requirements set forth by 14 CFR Part 61.57.

Restrictions to Visibility in Snow

According to the FAA publication, "General Aviation Pilot’s Guide - Preflight Planning, Weather Self-Briefings, and Weather Decision Making" (revised December 2009), certain weather conditions are particularly difficult to accurately perceive with the eye. One such phenomenon, called "flat light", can create hazardous operating circumstances. According to the guide, "Flat light is a condition in which all available light is highly diffused, and information normally available from directional light sources is lost. The result is that there are no shadows, which means that the eye can no longer judge distance, depth features, or textures on the surface with any precision. Flat light is especially dangerous because it can occur with high reported visibility. It is common in areas below an overcast, and on reflective surfaces such as snow or water. It can also occur when blowing snow or sand create flat light conditions accompanied by “white-out,” which is reduced visibility in all directions due to small particles of snow, ice or sand that diffuse the light."

The American Meteorological Society, Glossary of Meteorology defined whiteout as, "An atmospheric optical phenomenon of the polar regions in which the observer appears to be engulfed in a uniformly white glow. Neither shadows, horizon, nor clouds are discernible; sense of depth and orientation is lost; only very dark, nearby objects can be seen. Whiteout occurs over an unbroken snow cover and beneath a uniformly overcast sky, when with the aid of the snowblink effect, the light from the sky is about equal to that from the snow surface. Blowing snow may be an additional cause."

Transport Canada's Aeronautical Information Manual (section 2.12.7, revised October 2011) further described some of the causes and dangers of whiteout. Diffused light reflected in all directions by a white surface result in terrain that is virtually devoid of visual cues so that the eye can no longer discern the surface or terrain features. Several types of whiteout are described, including precipitation whiteout. Precipitation whiteout results from, "…small wind-driven snow crystals falling from low clouds above which the sun is shining. Light reflection complicated by spectral reflection from the snow flakes and obscuration of land marks by falling snow can reduce visibility and depth perception to nil in such conditions."