Accident Summary
On August 14, 2016, about 1420 central daylight time, a Bellanca 7ECA, registration N50437, collided with swampy terrain and nosed over during takeoff at Surfside Airport (MN24), Lino Lakes, Minnesota. The two pilots aboard were not injured. The airplane was substantially damaged. The airplane was registered to and operated by Wild River Flying Club, Saint Croix Falls, Wisconsin, under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was originating at the time of the accident and was destined for Osceola (OEO), Wisconsin.
Pilot and Instructor Reports
According to the pilot's accident report, he was attempting a short-field takeoff. The takeoff roll and acceleration seemed normal. As they approached the "point of no return," it felt like the airplane was lifting off, and he decided not to abort. The airplane lifted off before reaching the runway's end. The pilot reported that it felt like the wheels brushed against bushes past the departure end, slowing the airplane. Unable to climb, the airplane landed in a marshy area and nosed over.
The instructor reported that he was giving recurrency training. After takeoffs and landings on Runway 04 at Osceola, they proceeded to MN24. During departure from MN24, when the control stick was moved forward, the tail did not rise as expected. At the decision point, the pilot continued the takeoff. The instructor noted that the plane "wanted to fly" and started bouncing on the grass. Just before reaching brush, the plane was pulled up briskly to clear it. The right main or tail wheel contacted brushes, destroying acceleration, and the airplane traveled through reeds and cattails before the wheels touched firm ground and the airplane slowly nosed over.
Examination of Propeller and Engine
The instructor submitted an email stating that propeller examination showed no visible signs of rotation at impact. Dirt on the propeller was longitudinal (hub to tip) with no tip curling. No vegetation smears were found despite traveling over 200 feet through reeds and cattails.
According to the FAA inspector, the firewall was buckled at lower left and right engine mounting points. One propeller blade appeared buried in soft ground; the other was unmarred and straight. Flight control continuity was verified. The spinner showed no noticeable damage. Propeller blades were mostly undamaged with no obvious bending. Chaffing on one blade was horizontal, consistent with retrieval. Top spark plugs were in good condition. The engine turned through several rotations with no unusual noises or resistance. Magneto impulse couplings worked during rotation. All four cylinders had adequate compression. Fuel samples from the right wing, firewall sump, and fuselage sump appeared clean aviation fuel. Wing root fuel gauges read just above ¼ tank, confirmed by stick measurements. Throttle and mixture had full travel continuity. Carburetor heat was found off and movable about halfway toward on; maintenance personnel stated travel was limited by impact damage to the carburetor airbox.
Carburetor Ice and Ducting Theories
The instructor theorized that the rubber tube connecting the air scoop to the engine air intake could have folded, partially cutting off airflow. The FAA inspector discussed this with a mechanic, who stated the duct is clamped on the carburetor but not on the air filter; if not properly seated, it could distort and disrupt airflow, but this would be immediately apparent with the engine running. Maintenance records showed the lower cowling was last removed during the annual inspection on April 1, 2016, about 45 hours prior. Two oil changes occurred afterward, but the cowling was not removed during the latest. The inspector observed no deformation in the ducting at the accident site.
The instructor also theorized carburetor ice may have developed. The FAA inspector agreed it could be a possible contributing factor. The METAR at 1445 CDT from Anoka County-Blaine Airport (KANE), 4 miles west, reported calm wind, 10 miles visibility, 4,900 feet broken ceiling, temperature 25°C, dew point 15°C, altimeter 30.06 inHg. Carburetor Icing Probability Charts indicated moderate icing at cruise power and serious icing at descent or glide power.
Performance Study
A performance study calculated that MN24's elevation is 890 feet msl. Pressure altitude was 790 feet. Using the Bellanca 7ECA takeoff performance chart, the ground run was approximately 546 feet, and distance to clear a 50-foot obstacle was about 1,192 feet at a rate of climb of 595 feet per minute. MN24's runway 02-20 is 1,900 feet long.
Instructor's Medical Certificate
The FAA inspector noted the instructor's third-class medical certificate was dated July 3, 2014, and expired on July 31, 2016, as per Federal Aviation Regulations Part 67.23(d), given the instructor's age over 40.