Accident Details
On December 23, 2015, at approximately 1520 central standard time, a Beech V35B single-engine airplane, registration N4523A, was substantially damaged during a forced landing with the landing gear retracted at Tahlequah Municipal Airport (TQH), Tahlequah, Oklahoma. The private pilot was not injured. The airplane was registered to and operated by Beech V-35 LLC under 14 Code of Federal Regulations Part 91 without a flight plan. Day visual meteorological conditions prevailed. The business flight had departed TQH at 1515, bound for William R Pogue Municipal Airport (OWP) in Sand Springs, Oklahoma.
Pilot's Report
The pilot reported topping off the left fuel tank before the flight and estimating the right tank contained 15-20 gallons. After a normal takeoff from runway 35, he turned to a heading of 283 degrees and climbed toward a planned cruise altitude of 4,500 feet mean sea level, using 25 inches of manifold pressure and 2,500 rpm during cruise climb. About 2.5 miles from the departure airport, while climbing through 2,500 feet msl, the engine experienced a significant loss of power. The pilot did not hear a corresponding decrease in engine noise but noted he was wearing a noise-canceling headset. He immediately turned back toward the airport for a forced landing on runway 17. During the turn, the engine regained power briefly for 1-2 seconds. Concerned about altitude, he kept the landing gear and flaps retracted and pulled the propeller control full aft to reduce drag, though the propeller continued to windmill. The pilot admitted being distracted and forgetting to extend the gear once a safe landing on the runway was assured. The airplane landed wheels-up, sustaining substantial damage to the lower fuselage and several structural bulkheads.
After the landing, an individual approached the pilot and said the airplane sounded as if it were experiencing a propeller overspeed condition or governor failure. The pilot also noted that earlier that day, during before-takeoff procedures, cycling the propeller control did not produce a significant drop in propeller speed, a condition he had observed on the previous flight leg from Seminole Municipal Airport (SRE) to TQH.
Post-Accident Examination
A local aviation mechanic hoisted the airplane and manually extended the landing gear; no anomalies were found in the gear system. The airplane was then recovered to a hangar. On the runway, 12 discernible propeller blade strike marks were observed, the first about 800 feet from the runway 17 threshold, followed by scrape marks consistent with the lower fuselage abrading over about 500 feet. Visual inspection revealed ground impact damage to lower fuselage skins, bulkheads, nose landing gear doors, and exhaust pipes. The left fuel tank was full, the right tank about half full. Fuel samples, blue and consistent with 100 low lead aviation fuel, showed no water or particulate contamination.
Engine and Propeller Inspection
An FAA Airworthiness Inspector, a Hartzell Propeller representative, and a local mechanic conducted an additional examination. The propeller remained attached, spinner undamaged, all three blade tips bent aft with scoring. Blades were secure at the low pitch stop and could not be rotated by hand. When the cylinder was pressurized with shop air, the blades cycled without anomaly; no oil leaks were found. The propeller governor was removed and tested at the manufacturer: the drive shaft turned freely, oil discharged, radiographic imaging showed no anomalies, and an acceptance bench test found no discrepancies preventing normal operation.
The engine remained attached to the firewall. Mechanical continuity from cockpit controls to engine components was confirmed. Compression and suction were noted on all cylinders, upper spark plugs showed normal operation, both magnetos produced spark, and engine-to-magneto timing was within specifications. For an operational test, the governor was reinstalled and a two-blade test propeller fitted. The engine started after priming but lost power after a few seconds. Restarted with the electric fuel boost pump on, it ran normally while the pump remained on; however, a significant fuel leak developed during the second test, and power was lost when the pump was turned off. Further examination found a loose fuel line connection where the airframe fuel supply connected to the mechanical fuel pump inlet. After tightening the connection, the engine started a third time and operated normally with and without the boost pump, running smoothly through its speed range up to 2,700 rpm.
Additional Information
The accident engine, a Continental Motors IO-550-B51, was overhauled on June 22, 2015, and reinstalled on July 10, 2015, at 4,143 hours tachometer time. According to the engine logbook, no leaks were noted after the reinstallation test run. On September 29, 2015, at 4 hours since overhaul, the airplane was taken to D&B Aircraft Engines to address low power shudder and excessive oil consumption; the intake drain insert was reconditioned and unspecified adjustments made. On November 12, 2015, at 9 hours since overhaul, the oil and filter were replaced with no anomalies noted. The tachometer read 4,153.8 at the accident site, indicating 10.8 hours since overhaul.