CEN13FA073

The pilot’s decision to continue the flight into an area of extreme weather, which led to the in-flight encounter with a thunderstorm and structural failure of the wings and tail.

While in cruise flight, the twin-engine airplane encountered a severe thunderstorm that likely contained hail up to 1.25 inches in diameter. After penetrating the thunderstorm, the airplane's structure failed, which was evidenced by the pieces of the airplane being found up to 0.6 mile away from the main wreckage. The horizontal tail, which was found 0.25 mile from the main wreckage, had dents on the upper surface that were consistent with in-flight hail damage. The left horizontal stabilizer had failed in an upward direction, and the right horizontal stabilizer had failed in a downward direction, consistent with an extreme left roll rate. In addition, both left and right outboard wing sections were partially separated from the remainder of the wing. Although there was no record of the pilot having obtained a FAA weather briefing, it was not possible to determine if the pilot used other sources to obtain weather information prior to the flight. Records of in-flight communications indicated that the pilot was advised of adverse weather, including thunderstorms and moderate, heavy, and extreme precipitation about 15 minutes before his last transmission. At that time, the airplane was 40 miles from the storm. In addition, the pilot confirmed during communications that the airplane was equipped with on-board weather radar (which provided real-time weather), and the controller authorized him to deviate course, if necessary.

HISTORY OF FLIGHT On November 26, 2012, about 2124 central standard time, a Cessna 421C airplane, N67SR, was substantially damaged during an in-flight encounter with weather, in-flight separation of airframe components, and subsequent impact with the ground near Wells, Texas. The private pilot, who was the sole occupant, was fatally injured. The airplane sustained impact and fire damage to all major airframe components. The aircraft was registered to H-S Air LP and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a business flight. Instrument meteorological conditions prevailed for the flight, which operated on an instrument flight rules (IFR) flight plan. The flight originated from the West Houston Airport (IWS), Houston, Texas, about 2040 and was bound for the Richard Lloyd Jones Jr. Airport (RVS), Tulsa, Oklahoma. Witnesses near the accident site reported hearing an explosion and then seeing a fireball descending through the clouds to the ground. Radar track data for the last portion of the flight depicted the airplane on a 7720 transponder code. The track showed the airplane initially on a heading of about 20 degrees at 23,000 feet. The track continued in this direction until 2120:03.73 when the airplane began a right turn. The right turn continued for about 30 seconds during which time the altitude remained constant and the heading changed to about 90 degrees. After 2120:45.86, the track showed an erratic steep descent that continued to the end of the data. The final data location was received at 2122:15.53 at an altitude of 2,800 feet. The accident location was 0.86 miles and 94 degrees from the last recorded radar position. PERSONNEL INFORMATION The pilot held a private pilot certificate with airplane single-engine land, airplane multiengine land, and instrument airplane ratings. He was issued a third-class airman medical certificate, with a restriction for corrective lenses, on May 8, 2012. According to Federal Aviation Administration (FAA) records, the pilot reported having 2,500 hours total flight experience with 75 hours in the six months preceding his most recent medical examination. The pilot's flight logbook was not recovered during the investigation. AIRCRAFT INFORMATION The airplane was a Cessna model 421C, bearing serial number 421C-0257. It was a twin-engine propeller driven monoplane with a retractable tricycle landing gear. Different seating arrangements could be employed with the capability of seating 8 occupants including the 2 flight crew seats. The exact seating configuration of the accident airplane could not be determined due to the extensive impact and fire damage. The airplane was constructed mainly of aluminum alloy materials and had a cantilever main wing arrangement and a pressurized fuselage. Two Continental GTSIO-520-L engines, serial numbers 825011-R and 292480-R, were mounted on each wing and were each capable of producing 375 horsepower. Maintenance records for the airplane showed that it had accumulated 6736.2 hours total time in service as of its most recent annual inspection dated October 13, 2012. The left and right engines had accumulated 1,039.1 hours, and 1215.1 hours respectively since overhaul as of the date of the annual inspection. METEOROLOGICAL INFORMATION No record of the pilot having obtained a Flight Service Station (FSS), or Direct User Access Terminal System (DUATS), weather briefing was found for the accident flight. However, no determination could be made as to whether the pilot obtained weather information from other sources prior to the flight. An Area Forecast (FA) that included Texas was issued at 2045. The portion of the FA directed toward the southeastern quarter of the northeastern portion of Texas forecasted for times until 0100 the next day: ceiling broken at 3,000 feet msl with cloud tops to 8,000 feet msl and broken cirrus, isolated thunderstorms and light rain with cumulonimbus tops to 38,000 feet. No thunderstorms were forecast for other portions of northeastern Texas. No Airmen's Meteorological Information (AIRMET) advisories were issued for the accident location at the most recent AIRMET issuance times prior to the accident. The accident site was, however, close to an active AIRMET for IFR conditions issued at 2045. The Aviation Weather Center in Kansas City, Missouri, issued several Convective Significant Meteorological Information (SIGMET) advisories at 1955 and 2055 that were valid until 2155 and 2255 respectively. These SIGMETs were active for a line of thunderstorms in eastern Texas. The boundaries of the SIGMETs were all near to the accident site. The most recent SIGMET (5C) boundary depicted a 35 mile wide line of thunderstorms that stretched from 30 miles south-southeast of the BELCHER Very High Frequency Omni-Directional Radio Range Tactical Air Navigation Aid (VORTAC), near Shreveport, Louisiana, to 40 miles east of the CENTEX VORTAC near Austin, Texas. The thunderstorm had cloud tops to 45,000 feet and was moving eastward at 20 knots. The accident site was within the boundaries described in the SIGMET. The National Weather Service (NWS) Surface Analysis Chart for 2100 depicted a low-pressure center at the northwestern Louisiana border with Texas. Associated with the low-pressure center was a cold front that stretched southwestward through the accident region to Mexico, a warm front that stretched southeastward to the Mississippi Gulf coast, and a stationary front that stretched east-northeast. Station models depicted the wind as northerly behind the cold front in northeast Texas with magnitudes ranging from approximately 10 to 20 knots. Ahead of the cold front the wind was generally southerly with magnitudes near 5 knots. Most station models across eastern Texas depicted clear skies. Temperatures near to and immediately ahead of the cold front were near 70° Fahrenheit (F) with dew point depressions as low as 2°F. A regional Next-Generation Radar (NEXRAD) mosaic obtained from the National Climatic Data Center (NCDC) for 2120 CST identified a broken line of high (>50 dBZ) values of reflectivity that stretched from central east Texas to northwestern Louisiana. A part of this line was coincident with the accident location. WSR-88D Level-II base reflectivity weather radar data from Shreveport, Louisiana was obtained. Three-dimensional presentations of base reflectivity isosurfaces from the volume scan initiated at 2116:35 indicated that the accident aircraft penetrated the highest values of reflectivity (> 50 dBZ) during the final portion of its flight and just before its rapid descent. The eastern portion of the 50 dBZ isosurface that rose to a higher altitude was consistent with a convective updraft that may have contained hail. An algorithm utilized by the program GR2Alanlyst (a Nexrad Level II analysis application) to estimate hail stone diameter indicated the potential for 1.25 inch hail in that portion of the storm, and GR2Analyst identified the probability of severe hail (POSH) as high as 84.6 percent. COMMUNICATIONS Summaries and transcripts of communications between the airplane and various controlling facilities were obtained from the FAA. At 2033, the pilot contacted the Houston Intercontinental Airport (IAH) Terminal Radar Approach Control (TRACON), Satellite Clearance Delivery position using his airplane's radio and was issued an IFR clearance from IWS to RVS. The airplane subsequently departed IWS at 2040. The pilot maintained communications with the IAH TRACON until 0257 when he was handed off to the Houston Air Route Traffic Control Center (ARTCC). At 2057, the pilot checked in with the Houston ARTCC. After establishing communications, the controller cleared the pilot to climb and maintain 23,000 feet. The pilot inquired regarding reports of the cloud tops for the weather he was approaching. The controller advised the pilot that other aircraft were deviating a