CEN13FA267

A partial loss of power on both engines during takeoff for reasons that could not be determined because examination of the airframe and a test run of both engines revealed no mechanical anomalies that would have precluded normal operation.

The pilot and the pilot-rated passenger were preparing to depart from an airport where the twin-engine airplane had just undergone refurbishment of the interior. The pilot stated that both engines started normally. They taxied to the runway and used the checklist to perform an engine run-up on both engines. The pilot said the engine run-up was normal. He then lined the airplane up on the runway, applied full power to each engine (red line is 2,700 rpm), and departed. Once airborne, the pilot initiated a right turn. The pilot said that, when the airplane was at an altitude of between about 1,200 and 1,400 feet, he brought the propeller controls back to 2,500 rpm and left the power on both engines at 30 inches of manifold pressure. The mixture controls remained full forward. Almost immediately after reducing the rpm, the pilot heard a "faint" and indistinguishable "pop" from the left engine. Both engines simultaneously went from "full power" to idle, but the manifold pressure remained at 30 inches. The pilot said he made an immediate turn back to the runway and landed gear-up on the grassy area adjacent to the departure runway threshold. A postaccident examination of the airplane revealed only minor damage to the right wing, left horizontal stabilizer, and fuselage. The propeller blades also exhibited slight twisting, which was consistent with them rotating at the time of impact. Several slash marks made by the propellers were observed in the grass where the airplane made the forced landing. The measured distance between these marks was consistent with both engines operating between 1,570 and 1,890 rpm at the time the propellers contacted the ground. Data from the onboard engine monitor, which recorded exhaust gas temperature (EGT), cylinder head temperature (CHT), and turbocharger turbine inlet temperature on each engine, were downloaded and plotted. The data revealed that the left engine lost power several seconds before the right engine. A rise in EGT was observed at this time as well. According to the engine manufacturer, if the mixture control were leaned, it would have decreased the mechanical fuel pumps' fuel flow and might have caused the smooth rise in EGT. However, the CHT continued to climb for several seconds after the decline of EGT on both engines. The data also indicated that the EGT appeared to rise again slightly before the data ended. The pilot reported that he did not move the mixture control at any time during the short flight. Due to the engine monitor's limited parameters (no rpm or fuel flow data), a conclusive cause for the power loss could not be determined. Examination of the airplane's fuel, electrical, and flight control systems revealed no preincident mechanical deficiencies that would have led to a loss of engine power. Both engines were examined then test run on the airframe using the airplane's fuel system. No mechanical deficiencies were identified that would have contributed to a loss of engine power.

HISTORY OF FLIGHT On May 4, 2013, at 1200 central daylight time, N44GC, a Beech 58 twin-engine airplane, sustained minor damage during a forced landing shortly after takeoff from the Mena Intermountain Municipal Airport (MEZ), Mena, Arkansas. The commercial pilot and the pilot rated passenger were not injured. The airplane was registered to and operated by the pilot rated passenger. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight that was destined for the Bill and Hillary Clinton International Airport (LIT), Little Rock, Arkansas, under the provisions of 14 Code of Federal Regulations Part 91. The pilot stated that the airplane just had the interior refurbished in Mena, Arkansas, and he and the owner were flying the airplane back to their home base in Little Rock. The owner was not current and had hired the pilot to fly the airplane back with him. According to the pilot, he completed a preflight inspection before departure. He used the airplane's checklist to start the engines and both engines started immediately. The pilot taxied about 10-15 minutes to runway 27, where he performed an engine run-up on each engine using the checklist. The run-up was "normal" for each engine. The pilot then lined the airplane up on the runway, applied "full power" to each engine, and departed. Once airborne, he initiated a right turn. The pilot said that when the airplane was about 1,200-1,400 feet, he brought the propeller levers back to 2,500 RPM and left the power on both engines at 30 inches Hg of manifold pressure (MP). Almost immediately after, the pilot heard a "faint" and indistinguishable "pop" from the left engine. Then both engines simultaneously went from "full power" to idle. The pilot was unable to maintain altitude and made an immediate turn back to runway 27. The pilot said the mixture controls were full forward the entire flight. Each fuel tank was 3/4-full and the fuel selector was in the "on" position. The pilot said the MP gauge read 30 inches Hg and the fuel flow on the digital fuel gauge was "positive", about 25 gallons per hour per side. He did not recall looking at any of the other engine gauges because he was concentrating on making a safe landing. The pilot landed the airplane gear-up on the grassy area just short of runway 27. PERSONNEL INFORMATION The pilot held a commercial pilot certificate for airplane single and multi-engine land, and instrument airplane. He also held a certified flight instructor certificate for airplane single and multi-engine land and instrument airplane. His last Federal Aviation Administration (FAA) first class medical certificate was issued on April 4, 2013, with no waivers or limitations. The pilot reported a total of 1,381 flight hours, of which 250 hours were in multi-engine airplanes and 32.6 of those hours were in a Beech 58. He also reported a total of 29 hours in a Beech 55. AIRCRAFT INFORMATION The airplane was a 1974 Beech 58 twin-engine airplane (serial number TH-453). The airplane had several modifications that were installed under specific FAA approved Supplemental Type Certificates (STC). These modifications included Continental Motors, Inc. IO-550-C engines, a 4-bladed Hartzell propeller, TurboGAMIjector fuel injectors and a Merlyn Products Inc. turbo-normalizing system. An FAA approved airplane flight manual supplement was issued as a result of the Merlyn STC. A review of the supplement revealed an operating limitation for manifold pressure, which was not to exceed 30 inches. In addition, a placard had to be installed on the instrument panel. (This placard was found in the accident airplane above the manifold and fuel pressure gauges). A review of the airplane's maintenance logbooks revealed the last 100-hour inspection was completed in April 2013 at an aircraft total time of 7,785.2 hours. The left engine (serial number 684606) underwent a 100-hour inspection on April 11, 2013. At that time the engine had a total time of 973.3 hours and at the time of the accident it had a total of 974.2 hours. The right engine (serial number 684609) underwent a 100-hour inspection on April 11, 2013. At that time the engine had a total time of 973.3 hours and at the time of the accident it had a total of 974.2 hours. WRECKAGE EXAMINATION On May 5, 2013, a Federal Aviation Administration (FAA) inspector performed a visual examination of the airplane. He reported that several propeller blades were damaged and there was some damage to the landing gear doors. No structural damage was noted. The inspector also sumped each fuel tank and the fuel was absent of debris and water. The airplane, both engines, and the area where the airplane made the forced landing were examined May 29-30, 2013, by the National Transportation Safety Board (NTSB) Investigator-in-Charge (IIC). Also present for the examination were representatives from the Federal Aviation Administration (FAA), Continental Motors, Incorporated (CMI), Beechcraft Corporation, Hartzell Industries Inc., and Merlyn Products, Inc. AIRFRAME Examination of the airframe revealed the main entrance step had separated at the fuselage wall. The left elevator counter-balance horn was separated and the left elevator was buckled mid-span. The fuselage belly fairing that houses an air conditioning line was also separated. The fuselage belly skins exhibited evidence of minor buckling to internal structure. The nose landing gear doors were buckled. There was a small dent on the leading edge of the right wing just outboard of the engine. Examination of the fuel system revealed no mechanical anomalies. The fuel selector had distinct detents in all positions and fuel flow was confirmed when the fuel selector was turned on and confirmed to stop flowing when turned to off. The operation of the boost pump (both hi/low) was confirmed when the engines were test run. Mid wing fuel sight gauges were examined. The left wing indicated less than 60 gallons of fuel, and the right wing indicated 55 gallons, which was adequate fuel to sustain flight. Both of the wing fuel tanks sump strainers were removed and were absent of debris. RIGHT ENGINE The 4-bladed Hartzell propeller was still installed on the engine and all four propeller blades were bent aft mid-span with some indications of twisting. There was leading edge to trailing edge scoring at the tips and span-wise scoring along the length of the bent section of the blades. Two blades exhibited leading edge gouging near the tip of blades. The propeller was removed from the engine and a 2-bladed constant speed/counter-weighted-fully feathering McCauley propeller was installed. The top cowl had already been removed prior to the team's arrival, but the bottom cowl was still installed. The bottom cowl was removed. A crankshaft-propeller flange run-out was conducted and also checked for end-play. The test revealed no measurable results. The top spark plugs were removed and appeared dark in color. The No.1 plug was black and carbon-fouled. The gaps also appeared very close. The top plugs were placed on a test bench and all produced normal spark. After the propeller was installed, a thumb compression check via manual rotation of the propeller was conducted. Compression was established on each cylinder. LEFT ENGINE The 4-bladed Hartzell propeller was still installed on the engine and all four propeller blades were bent aft mid-span with some indications of twisting. There was leading edge to trailing edge scoring at the tips and span-wise scoring along the length of the bent section of the blades. The propeller was removed from the engine and a 2-bladed constant speed/counter-weighted-fully feathering McCauley propeller was installed. The top cowl had already been removed prior to the team's arrival, but the bottom cowl was still installed. The bottom cowl was removed. A crankshaft-propeller flange run-