# NTSB SEA08LA084: Raytheon B36TC, N234MT, Mammoth, CA, March 3, 2008 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: March 2, 2008, 16:20 local (Mar 3, 2008, 00:20 UTC) - Place: Mammoth, CA - Coordinates: 37.625556, -118.840835 - Nearby events: https://openairdocs.org/map.md?lat=37.6256&lon=-118.8408&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-climb to cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor - Status: Completed, report December 24, 2008 - Report: Approved by Office Director - Parties: Federal Aviation Administration - NTSB case key (mKey): 67609 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA08LA084 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/67609/pdf - Page: https://openairdocs.org/ntsb/SEA08LA084 ## Probable cause A loss of engine power for undetermined reasons. Contributing to the accident was dense snow covering the level terrain. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Power plant](https://openairdocs.org/ntsb-findings/01057100): Aircraft › Aircraft power plant · Not specified (probable cause); cases with it: [Raytheon B36TC, 1 case](https://openairdocs.org/ntsb-findings/01057100/cases.md?model=7150008), [All aircraft, 198 cases](https://openairdocs.org/ntsb-findings/01057100/cases.md) - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Raytheon B36TC, 1 case](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=7150008), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) - [Terrain: snowy/icy terrain](https://openairdocs.org/ntsb-findings/03021030): Environmental issues › Physical environment · Contributed to outcome (probable cause); cases with it: [Raytheon B36TC, 1 case](https://openairdocs.org/ntsb-findings/03021030/cases.md?model=7150008), [All aircraft, 77 cases](https://openairdocs.org/ntsb-findings/03021030/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-climb to cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Raytheon B36TC, 1 case](https://openairdocs.org/ntsb-events/341/sequence.md?model=7150008), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Raytheon B36TC, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=7150008), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-flare/touchdown: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Raytheon B36TC, 5 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=7150008), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis About three minutes after takeoff, the airplane's engine experienced a complete loss in power, but the propeller kept turning. Since the pilot could not get the engine restarted, he configured the airplane for a normal landing, and touched down in what appeared to him to be level snow-covered terrain. Upon touchdown, the airplane sank through about three feet of dense snow, which resulted in a rapid deceleration. Both the airplane's belly and the inboard portion of its wings suffered crushing damage. Inspection of the airplane's fuel storage and delivery systems, and the teardown inspection of the components of the turbocharger system did not reveal any evidence of an anomaly that would have kept the engine from producing full rated horsepower. The engine was successfully test run at various power settings up to a maximum of 2,400 rpm and 30 inches of manifold pressure. ## Factual narrative On March 2, 2008, about 1620 Pacific standard time, a Beechcraft B36TC, N234MT, collided with snow that was covering level terrain about three miles south of Mammoth Yosemite Airport, Mammoth Lakes, California. The private pilot received minor injuries, his passenger received serious injuries, and the airplane, which was owned and operated by the pilot, sustained substantial damage. The 14 Code of Federal Regulations (CFR) Part 91 personal cross-country flight, which departed Mammoth Yosemite Airport about five minutes prior to the accident, had a planned destination of Van Nuys, California. The pilot had not filed a flight plan. According to the pilot, three or four minutes after takeoff, the engine experienced a "major loss in power." He therefore turned back toward the airport and began to take action to try to restore full power. During this process he switched fuel tanks, checked the magnetos, activated the fuel boost pump to the prime position, and switched to alternate induction air. Ultimately, although the propeller kept turning, the engine lost all power, and the pilot began to look for what he thought would be a safe place to land. He elected to execute a forced landing on level snow-covered terrain in what appeared to be an open field. He then configured the airplane for a normal landing, and touched down in about three feet of dense snow with the landing gear extended. Upon touchdown, the landing gear broke through the surface of the snow, and as the airplane sank into the snow it decelerate rapidly. The accident sequence resulted in crushing damage to the airplane's belly and to the inboard portion of both wings. During the investigation it was determined that at the time of takeoff, the airplane contained about 65 gallons of aviation fuel, which was evenly distributed between the right and left fuel systems. The wreckage was recovered to the facilities of Air Transport, of Phoenix, Arizona, where an FAA-directed inspection of the airframe and engine was performed. That inspection did not reveal any anomalies in the airframe, its air induction system, or its fuel delivery system. After a visual inspection, the engine was successfully run at various power settings up to 2,400 rpm and 30 inches of manifold pressure. As part of the investigation the turbocharger turbine/compressor assembly, pressure relief valve, variable absolute pressure controller, and exhaust bypass valve assembly were sent to Kelly Aerospace Power Systems, where an FAA-monitored teardown inspection was performed. That inspection did not reveal any evidence of anomalies or malfunctions that would have prevented these components from operating in accordance with field serviceable standards. ## Aircraft - Registration: [N234MT](https://openairdocs.org/deregistered/N234MT-2009-10-01), registration cancelled 2009-10-01, S/N EA-656, built 2000 (OpenAirDocs) - Reported make and model: RAYTHEON AIRCRAFT COMPANY B36TC - Registry model: [Raytheon B36TC](https://openairdocs.org/model/raytheon-b36tc) (registry code 7150008) (OpenAirDocs) - Registry engine: [Continental TSIO-520 series](https://openairdocs.org/engine/continental-tsio-520-series) (registry code 17040, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: EA-656 - Airframe hours: 873 - Engines: CONT MOTOR TSIO-520-UB 300 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Michael S. Thesman - Registered owner: Thesman One Investments LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 9, 2007 - Departed: KMMH, Mammoth, CA - Destination: KVNY, Van Nuys, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 48; injuries: minor; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, without waivers/limitations; last flight review March 14, 2007; seat: left; flight hours: 884 total, 724 in this make and model, 37 in the last 90 days ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 39 °F ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20080302012079A](https://openairdocs.org/incident/20080302012079A), Mar 2, 2008: Beech B36TC, Mammoth Lakes, CA, Substantial damage. (-23) A normal preflight was performed; however, the pilot reported the start "took a little longer than normal." The pilot stated that during run-up… From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.