NTSB Factual Report

HISTORY OF FLIGHT

On October 17, 2015, about 0841 central daylight time, an experimental, amateur-built Vans RV-4 single-engine airplane, N999ZF, collided with terrain while maneuvering near Cortland, Nebraska. The private pilot and the pilot-rated passenger were fatally injured, and the airplane was destroyed. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. Day visual meteorological conditions prevailed at the accident site. The personal flight departed Crete Municipal Airport (CEK), Crete, Nebraska, at 0833, and the intended destination was Lincoln Airport (LNK), Lincoln, Nebraska.

According to available air traffic control radar track data, after departing CEK on runway 17, the airplane proceeded southeast and climbed to an altitude of about 2,600 ft mean sea level (msl). At 0836:30, the airplane turned south and descended to 2,400 ft msl. At 0837:44, the airplane turned east and continued to descend. Between 0839:23 and 0841:42, the airplane completed four low-altitude passes centered over a small lake located about 1/3 mile northeast of the intersection of West Ash Road and Southwest 29th Road. The small lake was located adjacent to a residence owned by the pilot's brother. The low-altitude passes and associated course reversals were completed within a 1/2 mile radius of the small lake. According to available topography data, the terrain elevation immediately surrounding the lake was about 1,470 ft msl.

According to radar track data, the airplane's first low pass over the lake was from southeast to northwest at an altitude at or below 100 ft above ground level (agl). The airplane then entered a climbing right turn to about 1,900 ft msl before it descended back toward the lake from north to south at an altitude at or below 100 ft agl. The airplane then completed a 180° turn at 1,600 ft msl before it descended for a low pass from south to north at an altitude at or below 100 ft agl. The airplane then entered a climbing right turn to about 1,800 ft msl before it descended for a fourth and final low pass from northeast to southwest at an altitude at or below 100 ft agl. Following the fourth low pass, the airplane entered a climb on a southwest heading to about 2,000 ft msl before it entered a sharp right turn toward north. The final radar return was recorded at 0841:42 and showed the airplane at 1,700 ft msl and about 472 ft east of the initial ground impact point.

The pilot's brother stated that he witnessed the airplane complete several low-altitude passes over his property immediately before the accident. He stated that following the final low pass, the airplane pitched up into a climbing right turn. He stated that, during the climbing turn, the airplane suddenly pitched nose-down and descended rapidly. The airplane recovered briefly to a wings-level attitude before it quickly rolled wings-left and -right and entered a descending right turn into terrain.

PERSONNEL INFORMATION

--- Pilot ---

According to Federal Aviation Administration (FAA) records, the 68-year-old pilot held a private pilot certificate with a single-engine land airplane rating. His most recent FAA third-class medical certificate was issued on November 1, 2013, with a limitation for corrective lenses. On the application for his current medical certificate, the pilot reported having accumulated 323 total hours of flight experience, of which 35 hours were flown within the previous 6 months.

The pilot's flight history was established using his logbook. The final logbook entry was dated October 14, 2015, at which time he had accumulated 512.5 hours total flight time. All logged flight time had been completed in single-engine airplanes. He had logged 501.9 hours as pilot-in-command, 3.4 hours at night, and 4.3 hours in simulated instrument conditions. He had flown 91.7 hours during the year before the accident, 47.8 hours during the 6 months before the accident, 15.8 hours during the 90 days before the accident, and 5.9 hours during the month before the accident. The pilot had accumulated 148.3 hours in the accident airplane make/model. His last flight review was completed in the accident airplane on July 16, 2014.

--- Pilot-Rated Passenger ---

According to FAA records, the 54-year-old passenger held a private pilot certificate with a single-engine land airplane rating. His most recent FAA third-class medical certificate was issued on February 4, 2013, with a limitation for corrective lenses. The medical certificate expired on February 28, 2015. On the application for his expired medical certificate, the pilot reported having accumulated 222.4 total hours of flight experience, of which 18.5 hours were flown within the previous 6 months. The pilot's flight history was established using his logbook. The final logbook entry was for a flight review on July 18, 2014, at which time he had accumulated 245.8 hours total flight time. The pilot had not logged any flight time during the year before the accident.

AIRCRAFT INFORMATION

The airplane, serial number 2407, was a single-engine, low-wing, fixed conventional landing gear, monoplane of conventional aluminum construction, configured to seat two occupants in a tandem seating arrangement. The airplane was powered by a 160-horsepower, 4-cylinder Lycoming IO-320-D1C reciprocating engine, serial number L-5910-55A. The engine provided thrust through a fixed-pitch, two-blade, Sensenich 70CM7S16-0-79 propeller, serial number 31698K. The airplane had a useful load of 628 pounds, a maximum allowable takeoff weight of 1,600 pounds, and a total fuel capacity of 32 gallons. A previous owner assembled the airplane from a kit. The FAA issued the airplane a special airworthiness certificate with an experimental classification and associated operating limitations on October 22, 1996. The pilot was the registered owner of the airplane, and FAA records indicated that he purchased the airplane in November 2013.

The airplane's recording tachometer was destroyed during the postimpact fire, which precluded a determination of the airplane's total service time at the time of the accident. According to the maintenance logbooks, the last condition inspection was completed on November 15, 2014, at 590.5 total airframe hours. At the time of the condition inspection, the engine had also accumulated 590.5 hours since new. The final logbook entry, dated October 8, 2015, was for an engine oil change at 674.5 total airframe/engine hours. A postaccident review of the maintenance records found no history of unresolved airworthiness issues.

METEOROLOGICAL INFORMATION

At 0854, the LNK automated surface observing system located about 25 miles north of the accident site reported: wind 120° at 9 knots, a clear sky, 10 miles surface visibility, temperature 8°C, dew point -1°C, and an altimeter setting of 30.49 inches of mercury

WRECKAGE AND IMPACT INFORMATION

The accident site was in a harvested soybean field. The wreckage debris path was oriented on a 265° magnetic heading and measured about 92 ft long. The initial impact crater contained the propeller and the right main landing gear. The impact crater also exhibited a well-defined propeller slash mark in the terrain. The estimated angle between the propeller slash mark and the surrounding terrain was about 30°. The two-blade propeller exhibited chordwise scratches near both blade tips. One propeller blade exhibited significant S-shape bending along its span. A large area of burnt ground and vegetation surrounded the main wreckage, which consisted of the fuselage, empennage, both wings, and the engine. A majority of the fuselage, including the cockpit and cabin, had been consumed during the postimpact fire. Flight control continuity could not be established due to impact and fire damage; however, all observed separations were consistent with overstress or damage caused by prolonged exposure to fire.

The engine remained partially attached to the firewall. Internal engine and valve train continuity were confirmed as the engine crankshaft was rotated. Compression and suction were noted on all cylinders in conjunction with crankshaft rotation. The internal oil pump discharged oil in conjunction with crankshaft rotation. The mechanical fuel pump exhibited fire damage and did not function. Neither magneto provided a spark when rotated by hand; however, both magnetos exhibited damage consistent with impact and prolonged exposure to fire. The upper spark plugs were removed and exhibited features consistent with normal engine operation. The fuel metering assembly had separated from the engine and exhibited impact related damage. The postaccident examination revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal engine operation.

MEDICAL AND PATHOLOGICAL INFORMATION

The Douglas County Coroner's Office, located in Omaha, Nebraska, performed autopsies on the pilot and pilot-rated passenger at the request of the Gage County Attorney. The cause of death for both individuals was attributed to multiple blunt-force injuries sustained during the accident.

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology tests on specimens obtained during each autopsy. The pilot's toxicology results were negative for ethanol. Ibuprofen was detected in the urine. Ibuprofen, sold under multiple brand names, is a nonsteroidal anti-inflammatory analgesic drug that is not considered impairing.

The pilot-rated passenger's toxicology results were negative for carbon monoxide and ethanol. Oxymetazoline was detected in urine but not in blood. Oxymetazoline, sold under multiple brand names, is an over-the-counter topical decongestant that is not considered impairing.

NTSB Probable Cause

The pilot's decision to intentionally maneuver at a low altitude and his failure to maintain adequate airspeed during the climbing right turn, which resulted in the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall.