NTSB Factual Report

On August 14, 2016, about 1420 central daylight time, a Bellanca 7ECA, 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 at the time of the accident, and no flight plan had been filed. The flight was originating at the time of the accident, and was destined for Osceola (OEO), Wisconsin.

According to the pilot's accident report and a written statement submitted to the Federal Aviation Administration (FAA), he was attempting a short-field takeoff. He said 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 made the decision not to abort [the takeoff]. The airplane lifted off prior to reaching the end of the runway. The pilot said it felt like the wheels brushed against the bushes past the departure end of the runway and the airplane slowed. Unable to climb, the airplane landed in a marshy area and nosed over.

According to the instructor's accident report and a written statement submitted FAA, he was giving the pilot recurrency training in the Bellanca 7ECA. Since light winds were out of the northwest, they made takeoffs and landings on OEO's runway 04, a grass runway, before proceeding to MN24, During the departure from MN24, when the control stick was moved forward, the tail didn't come up as far as he had expected. At a distance when a decision had to be made to abort or take off, the pilot decided to continue the takeoff. The instructor said the plane "wanted to fly because, as is normal for a tail wheel in a certain pitch attitude, it will start to bounce a bit, which [sic] was exacerbated by the grassy ground. At the last minute before the brush was reached, the plane was pulled up briskly to clear it." The right main or tail wheel contacted some brushes which destroyed some acceleration, but they were unable to maintain what little altitude they had. The airplane then traveled through some reeds and cattails before the wheels touched firm ground and the airplane slowly nosed over.

The instructor also submitted an e-mail in which he said an examination of the propeller showed no visible signs of rotation at the time of crash. "Any and all dirt on the propeller was longitudinal (hub to tip) and there was no cue tipping of the ends of the propeller. There was also no vegetation [smears] anywhere on the propeller even though the aircraft traveled more than 200 feet through reeds and cattails."

According to the report submitted by the Federal Aviation Administration (FAA) inspector who examined the accident site, the firewall was buckled at the lower left and lower right engine mounting points. The inspector wrote, "One of the blades appeared to be buried in the soft ground and the other appeared to be unmarred and straight. Continuity was verified for all of the flight controls.

"The spinner . . . did not appear to have any noticeable damage. The propeller blades appeared to be mostly undamaged and there was no obvious bending of the blades. The only chaffing on the propeller was on one of the blades, but was horizontal or in line with the longitudinal axis of the propeller. This chaffing appears to be consistent with propeller being pulled out of the ground during the retrieval process. The top spark plugs , , , appeared to be in good condition. The engine was turned through several rotations with no unusual noises or resistance. The magneto impulse couplings appeared to be working during the rotation which would indicate continuity through the engine. All 4 cylinders appeared to have adequate compression. Fuel samples were taken from the right wing, firewall fuel sump and the fuselage sump drain. All of the samples had the appearance and odor of clean aviation fuel. Both wing root fuel gauges showed readings of just above ¼ tank. A stick was used on both tanks to check the level and it appeared to be consistent with the gauge readings . . . The throttle and mixture [had] continuity through full travel. The carbuerator heat was found in the "off" and was able to be moved about ½ way toward "on." Maintenance personnel stated the travel of the carbuerator heat appeared to be limited by the impact damage to the carburetor airbox." After the airplane was recovered, it was discovered that the firewall was buckled in two locations.

In an e-mail submitted by the instructor, he theorized that the rubber tube that connects the air scoop on the cowling to the engine air intake could have folded to partially cut off air flow to the engine. The FAA inspector discussed this scenario with an airport mechanic. According to the mechanic, the duct is clamped on the carburetor but there is no clamp on the air filter. Once the duct is properly installed, it would be almost impossible for it to come off or kink. However, if the duct is not properly installed or seated on the flange, it will distort and disrupt airflow. This would affect the engine performance, but that would become immediately apparent with the engine running.

According to the airplane maintenance records, the last time the lower cowling was removed and re-installed was during the annual inspection on April 1, 2016, about 45 hours prior to the accident. There had been two oil changes prior. According to the mechanic who did the latest oil change, the lower cowling was not removed; rather, a quick drain was utilized to drain the oil. The inspector said when he examined the airplane at the accident site, he observed no deformation in the ducting.

The instructor also theorized that carburetor ice may have developed prior to the takeoff. The FAA inspector agreed that carburetor ice may have been "a possible contributing factor." The following METAR (aviation routine weather report), recorded at 1445 CDT at Anoka County-Blaine (Janes Field) Airport (KANE) in Minneapolis, Minnesota, located 4 miles west of Surfside Airport, was obtained:

Wind, calm; visibility, 10 miles; ceiling, 4,900 feet broken; temperature, 25° C.; dew point, 15°C.; altimeter setting, 30.06 inches of mercury.

The Carburetor Icing Probability Charts were consulted. In the first chart, Dew Point Depression = Temperature (25°C.,77°F.) – Dew Point (15°C., 59°F.), or 10°C. (18°F.) The dew point depression and temperature lines intersected within the "moderate icing-cruise power/serious icing-descent power envelope." Using the second chart, the temperature and dew point lines intersected in the "serious icing at glide power" envelope.

A performance study was also made. M24 is at an elevation of 890 feet msl (above mean sea level). Pressure altitude (PA) = altimeter setting – standard pressure, or PA = 30.02 – 29.92 = 0 .10 (100 feet). Subtracting, 890 - 100 = 790 feet PA. Consulting the Bellanca 7ECA "Takeoff Performance Chart" and interpolating, the airplane's ground run was computed to be approximately 546 feet, and the distance to clear a 50-foot obstacle was approximately 1,192 feet at a rate-of-climb of 595 feet per minute. M24's runway 02-20 is 1,900 feet long.

The inspector noted that the instructor's third class medical certificate was dated July 3, 2014. Since the instructor's age was over 40 years, the certificate was valid for 24 calendar months and expired on July 31, 2016 (Federal Aviation Regulations Part 67.23(d).

NTSB Probable Cause

A partial loss of engine power due to the formation of carburetor ice, which resulted in reduced climb capability and impact with vegetation and terrain during takeoff.