History of Flight
On March 19, 2011, at approximately 1605 mountain daylight time, a Cessna T310R, registration N4914A, collided with terrain while executing a missed approach at Bert Mooney Airport (BTM) in Butte, Montana. The commercial pilot, operating under Title 14 CFR Part 91, sustained fatal injuries. The airplane was substantially damaged and subsequently consumed by a post-crash fire. The cross-country personal flight had departed Great Falls International Airport (GTF) at about 1520, with a planned destination of Butte. Instrument meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan was filed.
A witness approximately 3.5 miles northwest of the arrival end of runway 15, at an elevation of about 5,600 feet msl, reported that snow began falling around 1540. About 1600, he observed unusually heavy snow blowing horizontally from west to east, creating eddy effects around his house. He then heard an unusually loud airplane engine sound, though he could not see the aircraft and did not hear an impact or explosion. Another witness, located at Montana Tech about 4 miles northwest of the runway, reported similar weather conditions and aircraft sounds. By the time he left his office two hours later, vehicles were encrusted with 1.5 to 2 inches of snow and ice.
Federal Aviation Administration (FAA) radar and voice communication data showed the pilot was receiving radar vectors from Salt Lake Air Route Traffic Control Center (ARTCC). The controller was managing multiple aircraft, including the accident airplane and a SkyWest Airlines Canadair Regional Jet (Flight 4658) also destined for BTM. Radar data indicated N4914A about 90 miles northeast of BTM at 1530:00, maintaining 13,300 feet on a track of 205 degrees true. At 1549:04, the pilot reported 13,000 feet. The controller provided BTM weather (recorded at 1538): wind 290° at 9 knots gusting to 16, visibility 1/3 mile, snow, fog, few clouds at 800 feet, broken 1,400 feet, overcast 2,200 feet. The pilot acknowledged the change. At 1551:01, the controller cleared the pilot for the ILS Y RWY 15 approach, directing him to fly direct to MAGIC intersection at or above 12,000 feet. The pilot read back the instructions and began a descent.
The controller then coordinated with SkyWest Flight 4658, which was holding. At 1558:24, N4914A reached MAGIC at 11,150 feet. Radar services were terminated, and the pilot was cleared to switch to advisory frequency. The target crossed MAGIC and began a right turn (consistent with holding pattern entry). The last radar return at 1559:00 showed 11,200 feet on a track of about 330 degrees. Shortly after, SkyWest cancelled its approach and diverted to Bozeman.
At 1604:24, the pilot of N4914A reported performing the missed approach. The controller provided altimeter setting, instructed climb to 15,000 feet, and asked intentions. After a pause, the pilot requested diversion to Helena. The controller instructed to report leaving 12,000 feet, but no response. A "Mayday Mayday" call was heard. The controller attempted contact for 35 minutes without success. A Pilatus PC-12 on an air medical mission also cancelled its approach into BTM after receiving a 1653 automated weather report.
Personnel Information
FAA records showed the pilot held a commercial pilot certificate with ratings for airplane single-engine land, multiengine land, and instrument airplane. He held a third-class FAA medical certificate issued March 2010, requiring corrective lenses for near and distant vision. No personal flight records were found, presumed consumed in the fire. His 2010 medical application reported 1,750 total flight hours, with 30 hours in the preceding 6 months. He received his private pilot certificate in 1982 and instrument rating in 1988. According to his multiengine rating application (April 2003), he had 170 hours of instrument experience, 89 in a training device. An insurance application from July 2010 reported 1,745 total hours, 52 in multiengine airplanes. BTM was his home airport.
Aircraft Information
The six-seat, low-wing, retractable-gear Cessna T310R was manufactured in 1978. It was powered by two fuel-injected, turbocharged Continental TSIO-520 engines with McCauley three-blade constant-speed propellers. Total flight time could not be determined due to damage. Maintenance records showed the most recent annual inspection was completed December 11, 2009, at 4,259.0 airframe hours. Both engines had 1,809.4 hours since overhaul in January 1994. Eleven maintenance events occurred after that inspection, the last on December 9, 2010. No subsequent annual inspection was found. The last transponder/static system test was February 12, 2008; FAA regulations require such tests every 24 months.
The airplane was equipped with a NAV-O-MATIC 400B two-axis autopilot with HSI, Cessna "Known Icing Conditions" deice system (electric windshield, pneumatic boots, heated pitot/static ports, propeller deice), and supplemental oxygen. It also had an L-3 Stormscope WX-1000, Garmin 530AW with WAAS GPS/nav/com, and Garmin GDL-49 XM satellite data link. The pilot purchased the airplane in July 2010; the prior owner (also a mechanic) continued to fly and share maintenance costs, stating the pilot often performed maintenance under supervision.
Meteorological Information
BTM had an automated surface observation system. Weather deteriorated from VFR in the morning to IFR and then low IFR (LIFR) during the flight. A special report at 1518 (2 minutes before departure) showed wind 290° at 15 gusting 23 knots, 9 miles visibility, scattered 2,400 feet, overcast 7,000 feet. Two minutes later: visibility 2 miles in light snow, temperature 2°C, dew point -3°C. Multiple special reports indicated rapid decrease in visibility and ceilings with gusting winds. The final special report before the accident (1553) showed wind 300° at 8 knots, 1/4 mile visibility, snow, freezing fog, broken 400 and 900 feet, overcast 1,400 feet, temperature -1°C, dew point -2°C.
Four pilot reports were transmitted: two indicated icing (light to moderate rime ice over Helena and light rime at 11,000 feet east of Billings). Forecasts for the area west of the Continental Divide predicted overcast at 8,000 feet with tops to 25,000 feet and scattered light rain/snow showers. The southwestern mountain region expected broken at 10,000 feet, overcast at 15,000 feet with tops to 25,000 feet, occasional light rain/snow, and isolated thunderstorms. AIRMETs covered mountain obscuration and icing conditions. The BTM terminal area forecast issued at 1140 predicted VFR from 1500-2100 with wind 250° at 11 gusting 18 knots, visibility >6 miles in light snow, broken 6,000 feet. At 1545, the forecast was amended to IFR: visibility 1/2 mile in moderate snow and fog, scattered 800 feet, broken 1,400 feet, overcast 2,200 feet. The National Weather Service Current Icing Product analysis for 1600 at 10,000 feet indicated >50% probability of icing over southwestern Montana, reaching 70% near the Wyoming/Idaho border.
The pilot filed an IFR flight plan and received a weather briefing via DUATS about 25 minutes before departure, selecting a low-altitude briefing. He filed a route from GTF to HLN to EVVERS at 13,000 feet, with 3 hours of fuel and no alternate airport. He subscribed to Sirius XM Satellite Weather 'Aviator' service, providing NEXRAD, graphical/text METAR, wind, and temperature/dew point data to the Garmin 530AW. Baron Services compiled the data; no outages were reported.
Aids to Navigation
The ILS Y Runway 15 approach used a glide slope and final approach course of 151° magnetic, with initial approach fix MAGIC at the intersection of the glide slope and CPN VOR 027° radial. Charted holding minimum altitude at MAGIC was 10,000 feet. The missed approach procedure specified climb to 7,300 feet, then a climbing right turn to 9,100 feet via CPN 113° radial. Wreckage was located along CPN 086 radial. Published landing minimums required 4 miles visibility and a decision height of 6,711 feet msl (1,188 feet agl). FAA regulations prohibit scheduled air carriers from proceeding past the final approach fix unless weather meets minimums; Part 91 operations have no such limitation.
Airport Information
Bert Mooney Airport had two runways: 15/33 (9,001 x 150 feet) and 11/29 (5,100 x 75 feet). No control tower; approach/departure services provided by Salt Lake ARTCC. Airport elevation was 5,550 feet, surrounded by mountainous terrain with elevations between 6,000 and 10,000 feet.
Wreckage and Impact Information
The wreckage was on a south-facing slope of rolling hills about 5.5 miles northwest of the airport, at approximately 5,700 feet elevation. Terrain consisted of grassland with rocky outcroppings, saplings, and pine trees (6-20 feet tall). The airplane came to rest nose-down on rocks, heading about 180° magnetic. Both engines remained near their wing mounts, in a 60° nose-down attitude. The cabin was crushed to about 5 feet in length and consumed by fire. Both wings had accordion crush damage perpendicular to the leading edge. Remaining wing skins, aft cabin, and tailcone were fire-consumed. The vertical stabilizer/rudder and horizontal stabilizer/elevator were found downhill. The primary debris field extended 60 feet downhill, containing upper cabin skin, flight instruments, and fragmented parts. A 40-foot power transmission pole about 25 feet east was undamaged; transmission cables traversed the debris field diagonally. One sapling next to the fuselage sustained thermal damage. All sections were accounted for. Fragmentation and position were consistent with a wings-level, 50° nose-down impact.
Medical and Pathological Information
A postmortem examination by the State of Montana Forensic Science Division determined the cause of death as blunt force injuries. Toxicological tests by the FAA Civil Aeromedical Medical Institute were negative for all screened drug substances and ingested alcohol.
Tests and Research
The airframe was examined at the site and later recovered. Most autopilot, navigation, deicing, and oxygen system components were fragmented or consumed by fire; their operational status could not be determined. The engine tachometer indicated left engine 2,550 rpm and right engine 2,425 rpm. The turn and slip indicator had a left turn indication of about 6° per second. Flight control push-pull tubes and cables had multiple breaches. Flap position determined from chain link settings at the flap motor indicated 15° flaps. Two vacuum pumps were found: one intact with fractured vanes and rotor, the other only case and mounting pad; both inner cavities showed no distress. No evidence of in-flight fire or bird strike was observed.
The right engine was partially attached to its wing mount, nose-down against rocks. Crush damage separated the forward crankcase, number six cylinder head/piston, and crankshaft forward of the number five connecting rod journal. Number five cylinder was separated but remained attached via piston rod. Multiple rocker covers were separated. Borescope examination of cylinders showed no foreign object damage; pistons and combustion chambers had light grey deposits. Exhaust valve heads had symmetrical coloration. Propeller governor, alternator, propeller hub, fuel control, magnetos, throttle body, and induction manifold were fragmented. The engine data plate area was damaged, but the left engine was similarly damaged and could not be rotated due to impact damage. Both propellers exhibited rotational damage signs consistent with power at impact.