NTSB Factual Report

On December 1, 2012, about 1030 eastern standard time, an experimental amateur-built RV-4, N416DH, was substantially damaged when it impacted terrain during a forced landing following a partial loss of engine power near McConnell Airfield (5NC3), Carthage, North Carolina. The certificated commercial pilot/co-owner of the airplane and the certificated airline transport pilot were seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the flight, which originated from Long Island Airport (NC26), Long Island, North Carolina, and was destined for Rowan County Airport (RUQ), Salisbury, North Carolina. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.

According to the commercial pilot, he had purchased the airplane about two months prior to the accident and had flown it home from Utah. Since then, he had been trying to identify and rectify some "squawks" he had noted with the airplane. One of the issues he had observed was that fuel seemed to be seeping from the right wing fuel tank, and he had been attempting to identify the source of the leak. About one week prior to the accident flight, he re-sealed all of the rivet lines on the fuel tank from the outside. The purpose of the accident flight was to test fly the airplane and determine if the leak had been fixed.

The commercial pilot, was seated in the front seat of the airplane, which was equipped with a fully functional set of flight/engine controls and instrumentation, while the airline transport pilot was seated in the rear seat, which was only equipped with basic flight and engine controls, and did not include flap or brake controls. The pilots planned to fly around the local area, and had anticipated stopping at several airports throughout the day. After performing a preflight inspection, the pilots filled the airplane's fuel tanks and departed from Lake Norman Airpark (14A), Mooresville, North Carolina. They then proceeded uneventfully to NC26, where after a brief stop, they departed on the accident flight.

About 5 minutes after departing, and while flying at an altitude of about 3,000 feet msl, the airplane's engine began losing power over a period of about 15 seconds, and continued to run roughly at a very low power output. The front seat pilot activated the carburetor heat, richened the mixture, activated the fuel boost pump, ensured that the primer was locked in place, and switched the fuel selector from the right to left fuel tank. The rear seat pilot then took control of the airplane and turned towards 5NC3, which was nearby.

Upon arriving over the airport, the rear seat pilot circled overhead in order to lose altitude before turning onto the final approach to the runway and asking the front seat pilot to set the flaps to 30 degrees. Shortly before reaching the runway threshold, the rear seat pilot heard a loud "bang," and realized that the flaps had retracted from the 30- to the 10-degree position. The rear seat pilot then asked the front seat pilot to reposition the flaps back to the 30-degree position; but could not recall if the front seat pilot had done so. Seeing persons and vehicles near the departure end of the runway, the rear seat pilot elected to abort the landing, increased the throttle to the full forward position, and maneuvered the airplane toward a farm field to the south of the runway. While attempting to land, the airplane touched down hard, collapsing the landing gear, before coming to rest in a stand of trees, resulting in substantial damage to the fuselage and both wings.

A Federal Aviation Administration (FAA) inspector performed a cursory examination of the airplane at the accident site, and noted that the wing flaps appeared to be fully extended. The airplane was subsequently recovered from the accident site and examined. Both fuel tanks were breached at the inboard forward attach points where the fuel lines were installed. Both fuel tank caps were in place and their seals were in good condition. Interior inspection of the tanks revealed that they were absent of fuel, water, or contamination. A flop tube was installed in each tank and considerable amount of fuel tank sealant was present on the braided steel cover of each flop tube.

The gascolator was removed opened for inspection, and was completely full of light-blue colored fuel that had a smell consistent with 100LL aviation fuel. About 1/2 teaspoon of solid contaminants was present at the bottom of the gascolator. The contaminants appeared consistent with flaked fuel tank sealant and dirt.

Fuel samples from the fuel pump and gascolator were tested for the presence of water, and none was found.

The cockpit fuel selector valve and fuel lines from the gascolator to the valve and from the valve to the wing roots were tested with compressed air. The valve operated normally and the lines were clear of obstructions. The fuel lines forward of the engine firewall were removed and examined for blockage, with no obstructions noted.

The engine-driven fuel pump was removed from the engine and its input was actuated manually. The pump operated normally and pumped fuel. The pump was subsequently disassembled and examined, and the fuel screen was absent of debris or contamination and the fuel inlet and outlet ports were normal in appearance.

The carburetor fuel inlet screen was examined and was absent of debris. The carburetor could not be tested due to impact damage; however, a visual examination of its components was unremarkable. The carburetor bowl was clean and dry; however, it was broken free from the upper half of the carburetor.

Continuity of the engine's powertrain and valvetrain were confirmed by rotation of the crankshaft at the propeller flange. The crankshaft turned with no binding noted, and suction and compression were observed on all cylinders. Rotation of the crankshaft produced spark at each of the impulse coupler-equipped right magneto's terminal leads, and the left magneto was not tested. The four top spark plugs were removed and all exhibited normal wear and were light gray in color.

According to FAA airworthiness records, the experimental amateur-built airplane was completed and certificated in 1991. The airplane was equipped with a Lycoming O-320-E2A engine. Review of maintenance records revealed that the airplane's most recent condition inspection was completed by the airplane's builder in March 2012.

The weather conditions reported at Moore County Airport (SOP), Pinehurst, North Carolina, located about 8 nautical miles south of the accident site, at 1035, included winds from 220 degrees at 5 knots, 10 statute miles visibility, clear skies below 12,000 feet, a temperature of 15 degrees C, a dew point of 7 degrees C, and an altimeter setting of 30.41 inches of mercury. Consultation of a carburetor icing probability chart published by the FAA showed that the temperature/dewpoint conditions were favorable to the accumulation of "serious icing at glide power."

NTSB Probable Cause

A partial loss of engine power for reasons that could not be determined because postaccident examinations of the engine and fuel system revealed no anomalies that would have precluded normal operation. Contributing to the severity of the accident was the rear-seat pilots' decision to abort the landing with partial engine power and his failure to successfully perform a forced landing to an available airfield.