TULLAHOMA, TN, USA
N4265R
Beech E50
The airplane was being used for sport parachute operations. During the initial climb after takeoff the right engine failed followed by the airplane's slow descending right turn into wooded terrain. The airplane crashed through trees and caught on fire. The fire was extinguished prior to the destruction of the airplane. Subsequent examination of the engine revealed that one crankshaft counterweight had broken its retaining lugs and was liberated inside the engine, resulting in sudden stoppage of the engine. The sudden stoppage prevented the pilot from feathering the propeller. Metallurgical examination of the crankshaft and counterweight revealed damage that was consistent with 'detuning' of the engine counterweights. Counterweight detuning results from excessively rapid throttle movements. Additionally, the engine log indicated that during an oil change 8 days before the accident, wear metal was found in the oil. The airplane continued to be flown with no further maintenance action taken.
HISTORY OF FLIGHT On June 28, 1997, about 1430 central daylight time, a Beech E50, N4265R, collided with trees during an emergency descent, following takeoff, from the Tullahoma Regional Airport, Tullahoma, Tennessee. The airplane was operated by Tennessee Skydiving Center, Inc., under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed. A flight plan was not filed for the sport parachute flight. The airline transport pilot, who held a multi engine land rating, sustained minor injuries, two parachutists were seriously injured, six parachutists had minor injuries and the airplane was substantially damaged. The flight was originating at the time of the accident. According to the operator, the airplane departed runway 18 and appeared to be climbing normally. Near the end of the runway it began to descend and turn right. The operator indicated that the pilot and some of the passengers reported that there was a right engine malfunction. The airplane collided with trees and the ground about one mile from the end of the runway, and about 1/4 mile right of the extended runway centerline. PERSONNEL INFORMATION The pilot held airline transport pilot certificate 128565855, with an airplane multi engine rating. He held commercial privileges with an airplane single engine land rating. His last medical certificate, a Class II, was issued on June 1, 1997, with no limitations or waivers. According to the operator's report of the accident, the pilot had 7,190 total flight hours with 6,180 total flight hours in multi engine airplanes. The report indicated that the pilot had 51.7 total hours in the same make and model airplane, with 34.3 and 7.4 flight hours within the last 90 and 30 days, respectively. His total flight hours within the last 90 and 30 days was reported as 38.3 and 17.4, respectively. Additionally, the pilot held type ratings in the Boeing 737, Beech 300, Beech 1900, and the Saab 340. AIRCRAFT INFORMATION The Certificate of Registration listed the airplane as follows: N4265R, serial number[SN] LH-166, Beech E50, registered to an individual, date of issue March 30, 1992. The Standard Airworthiness Certificate for the airplane listed the make and model as a Beech Aircraft Corp. E50, serial number LH 166, and indicated that the airplane was certificated in the Normal category. The Airworthiness Certificate was issued on March 4, 1993, by a designated airworthiness examiner [copy attached]. Three data tags were found on the airplane. One tag read as follows: "THIS U-8G AIRCRAFT RESURRECTED FROM THE DESERT BY ADS JOEL FREDERICK AME1 JOHN Q. BURRIS AMS1 DANIEL J. HEINO AX1 OSCAR S. COHEN." The second data tag read as follows: AIRCRAFT FIXED WING STOCK NO 01 A L-23 SERIAL NO 58 1339 REG NO L23D MODEL NO 50 00000 B 50 CONTRACT NO A F 33 600 35692 INSPECTED U S. The third data plate was a Beech Aircraft Corporation data plate that listed the following information: SN LH 166, Model L23D, date manufactured 7-1958, engine LYC-O-480-1, Type certificate 5A4, P.C. 8. Federal Aviation Administration Aircraft Specification NO. 5A4, Type Certificate Data Sheet (TCDS) listed the airplane as a Beech Aircraft Corporation E50 (L-23D). The specifications in the TCDS indicated that the airplane was a Model E50, Twin bonanza, (Military L-23D) The design was approved December 1, 1956. Serial numbered airplanes eligible for this designation were LH-96 and up, as a L-23D. The airplane was originally manufactured for the military. The TCDS states that prior to civil certification, L-23D airplanes that have been operated by the military services must be modified by Beech Dwg. 50-001016. An entry in the aircraft log, dated July 1, 1992, indicated that the airplane was inspected to verify conformance with the previously noted Beech drawings. A second entry noted that type certificate compliance was found by inspection, except for the "engine generators." A stamped entry followed, which indicated that a special airworthiness certificate was issued on July 1, 1992. Subsequently, following entries dated March 2, 1993, stating the airplane had been inspected in accordance with an airworthiness inspection, the Standard Airworthiness Certificate dated March 4, 1993, was issued. The engines installed on the airplane, at the time the airworthiness certificate was issued, as listed in the aircraft log, were Avco Lycoming O-480-1B engines. The TCDS listed the specified engines as 2 (two) Lycoming GSO-480-A1A6 (Military O-480-1) or GSO-480-B1B6 engines. The left engine had two data plates. One data plate contained the following information: Avco Lycoming Aircraft Engine Model O-480-1B, Engine NO. L-1296-33A. The second data plate stated "Rebuilt by Columbia Aircraft Services, Bloomsburg Municipal Airport, Bloomsburg, PA, 6-13-77, Contract No. DAA101-74-D-0049, Ser. No. NSN 2810-00-109-4578, Total Time 3049. The left engine was installed on the airplane at the time the airworthiness certificate was issued. An entry in the left engine log, dated July 1, 1992, stated "Inspected engine and found in compliance with T.C. Data." The entry was signed by an airframe and powerplant mechanic. The right engine also had two data plates. One read as follows: Avco Lycoming Aircraft Engine Model O-480-1B, type Certificate 284, serial number L0773-33A. The second data plate read similarly to the left engine data plate from Columbia Aircraft Services except the date was 12-19-75 and the total time was listed as 3335. Upon disassembly of both engines at the manufacturer's facility in Williamsport, PA, the crankshaft counterweight and counterweight roller configuration was found to conform with an Army commercial engine overhaul contract. Thus the engines were designated O-480-1B. This configuration did not conform with the TCDS or subsequent Lycoming Service Instruction No. 1012F, dated October 31, 1988. The disassembly and examination of the right engine also revealed that the number 6 counterweight had broken free of its associated crankshaft counterweight beam. Each counterweight beam contains two holes for installation of counterweight rollers. The beam was fractured through the counterweight beam lugs. The counterweight was liberated inside the engine and lodged between the crankshaft and the case, precluding crankshaft movement. Close examination of the number 3 counterweight beam lug revealed indentations on the interior circumference of the lug consistent with counterweight roller contact during crankshaft rotation. An entry was found in the right engine logbook dated June 20, 1997, that indicated that at 14,562.4 total airframe hours and 422.4 hours since engine overhaul, the oil and filter were changed by the operator. The entry stated "Wear Metal Found, Serviced w/ 3.5 GAL 15W50." TESTS AND RESEARCH The crankshaft, number 3 counterweight assembly, and the number 6 counterweight assembly were sent to the NTSB Materials Laboratory for examination. The fracture features of the broken number 3 counterweight beam lugs were obliterated by post-separation damage. However, fracture faces on the broken off pieces of the lugs had features indicative of an overstress fracture mechanism. Additionally, there were impact marks at the base of the number 6 counterweight support beam consistent with damage produced by contact with the bottom of the corresponding counterweight. A through-the-wall crack was found in the bushing and a small crack was found in the lug of one of the roller holes in the number 5 counterweight beam. The crack was opened mechanically for scanning electron microscope viewing of the fracture faces, revealing fracture features indicative of either an overstress separation or a separation produced by a very few overstress cycles, on both the bushing and the lug. Roller impact damage was also noted on the interior surface of the busing installed in one of the holes of the number 3 counterweight beam. Textron Lycoming Mandatory Service Bulletin No. 245D, dated April 10, 1987, indicated that damage to the crankshaft counterweight beams and bushings was indicative of detuning of the counterweight system most likely resulting from operation of the engine "at setting beyond the capability of the engine, ...particularly...at low altitude." ADDITIONAL INFORMATION During the examination of the airplane at the accident site, it was noted that the cabin door had been removed. Additionally, a "jump step" had been installed on the airplane, as well as a hand rail, which was installed on the top of the fuselage above the cabin door. According to Raytheon Aircraft Company, there is no Flight Manual Supplement for any Model 50-series airplane approving flight with the cabin door removed. It was also noted that the copy of the airplane operating manual provided by the operator contained a page labeled "BEECHCRAFT QUEEN AIR 65-B80 LANDPLANE AIRPLANE FLIGHT MANUAL SUPPLEMENT for the FLIGHT WITH CABIN DOOR REMOVED." The words "QUEEN AIR 65-B80" were crossed through.
improper operation of the engine that produced internal damage, and improper servicing of the airplane by the owner/pilot mechanic that resulted in the subsequent mechanical failure of the engine crankshaft counterweight. Contributing to the accident was the pilot's inability to feather the propeller.
Source: NTSB Aviation Accident Database
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