History of Flight
On May 27, 2011, at about 1515 eastern daylight time, a Beechcraft C90, registration N291CC, was substantially damaged during an encounter with severe turbulence at an altitude of 20,000 feet, approximately 10 miles north of Woodward Airport (CDN) in Camden, South Carolina. The airline transport pilot and four passengers were not injured. Instrument meteorological conditions prevailed, and the airplane was operating on an instrument flight rules flight plan from Charleston International Airport (CHS), Charleston, South Carolina, to Newark-Heath Airport (VTA), Newark, Ohio. The personal flight was conducted under 14 Code of Federal Regulations Part 91.
The pilot reported obtaining weather information via the internet prior to the flight, which included advisories for convective activity and scattered thunderstorms along the intended northwest route. Takeoff and climb to cruise altitude were normal, with intermittent light turbulence.
About 100 miles northwest of CHS, the pilot observed weather ahead on the onboard radar and requested a course deviation from air traffic control. A 30-degree deviation was granted due to a commercial airliner climbing nearby. The pilot found that an additional 30- to 45-degree deviation was needed and attempted to contact the controller three times without response, then turned further west. The airplane then encountered moderate to severe turbulence lasting about 2 minutes, with an altitude deviation of approximately 300 feet.
After the encounter, the airplane performed normally with no observed anomalies, and the pilot continued to the destination. A postflight visual inspection revealed no damage, and the airplane was flown back to CHS the following day. A subsequent closer inspection revealed wing spar damage at the fuselage attach point and wrinkling of the wing skin.
Air traffic control voice communications indicated the pilot established contact with Jacksonville Center at 1449, reporting climbing through 7,000 feet and experiencing light chop. The controller cleared the airplane to 15,000 feet. At 1450, the controller noted scattered areas of moderate to extreme precipitation along the route; the pilot responded that it looked good and believed they could get through. At 1454, the pilot was cleared to flight level 200.
At 1507, the pilot requested a 45-degree left deviation to avoid weather; the controller cleared up to 30 degrees left. Multiple radio calls about weather deviations occurred. At 1511, the pilot reported being "beat up pretty good" and requested further deviation. The controller suggested a heading of 350 degrees to exit weather. The pilot reported moderate to severe turbulence about 3 minutes prior, with light to moderate at that time. By 1514, the airplane was exiting extreme precipitation. The controller asked about damage or injuries; the pilot replied all was okay. At 1515, the pilot reported being in the clear. The controller advised making a precautionary landing if structural damage was suspected.
Personnel Information
The pilot held an airline transport pilot certificate with ratings for airplane single engine land and sea, multiengine land, and a flight instructor certificate with ratings for airplane single- and multiengine land and instrument airplane. He reported 14,500 total flight hours, with 2,200 hours in the accident airplane make and model. His most recent flight review was in February 2011.
Aircraft Information
According to FAA records, the airplane was manufactured in 1977 and powered by two Pratt & Whitney PT-6 turboprop engines. The most recent continuous airworthiness program inspection was on April 27, 2011, at which time the airframe had 10,423 total hours. The airplane was equipped with weather radar, a multifunction display with NEXRAD weather information from a commercial satellite service, and a stormscope lightning detection system.
Meteorological Information
An NTSB Weather Study indicated that the 1515 weather observation at CDN included winds from 320 degrees at 9 knots gusting to 39 knots, one-half mile visibility in rain and thunderstorms, broken clouds at 300 feet, overcast at 3,600 feet, temperature 23°C, dew point 20°C, and altimeter 29.87 inHg. Distant lightning was noted east and west of the airport. A SIGMET was active for severe thunderstorms moving from 220 degrees at 20 knots with cloud tops above flight level 450. A Severe Thunderstorm Watch was issued for the area, forecasting severe thunderstorms with hail up to 1.5 inches, extreme turbulence, and surface wind gusts to 60 knots.
Radar imagery with track overlay showed the airplane heading northwest and entering moderate precipitation by 1510. Areas of intense to extreme precipitation were to the northwest through southwest, with cloud tops at 36,000 feet and lightning. At 1511, the airplane turned left about 30 degrees and entered intense precipitation. By 1512, it was in the middle of intense precipitation, then turned left another 30 degrees. By 1513, it cleared intense precipitation and turned right about 45 degrees back toward the destination. Radar and NEXRAD showed areas with less precipitation to the northeast, south, and southeast.