N107JLRans S-12 AIRAILE · 2005

On April 16, 2011, about 0805 mountain standard time, an experimental amateur-built Rans S-12S airplane, N107JL, was substantially damaged during an attempted precautionary landing at Pinal Airpark (MZJ), Marana, Arizona. The precautionary landing was prompted by an engine over-temperature event. The pilot/owner and his passenger were not injured. The personal cross-country flight was operated under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed.

Prior to the flight, the pilot fueled the airplane so that the onboard fuel quantity was 16 gallons, which was 2 gallons less than the total capacity of 18 gallons. He then conducted a preflight inspection without the aid of a checklist. The pilot did not check the quantity of the engine coolant, or the security of the coolant system cap.

About 0753, the airplane departed the Ultralight Strip Ultralight Flightpark (4AZ8), Marana, for Chapman Airstrip (58AZ), Young, Arizona, located approximately 110 miles to the north of 4AZ8. When the airplane had been in flight for about 14 minutes, and was at an altitude of about 6,000 feet above mean sea level (msl), the passenger detected an odor that she believed to be engine coolant. The pilot checked his engine instrumentation, and observed that the engine coolant and oil temperature gauges registered excessively high values. He reduced the throttle to idle and executed a 180-degree turn, with the intent of conducting a precautionary landing on runway 12 at MZJ.

When the airplane was about 3,500 feet north of the threshold, the pilot determined that the airplane would not be able to reach the runway. When the airplane was just above a dry, fenced-in water catchment basin, the pilot realized that the fence would prevent the airplane from reaching a paved ramp on the airport property. The pilot made a "sharp turn" to the right about "10-20" feet above the ground, and intentionally "allowed the [air]plane to stall" onto the flat earthen floor of the basin. The airplane impacted right wing down, and sustained substantial damage to both wings. The pilot and passenger exited normally after the pilot shut down the engine.

The pilot held an FAA sport pilot certificate, and reported a total flight experience of 308 hours, including about 250 hours in the accident airplane make and model. His most recent flight review was completed in December 2009.

The light-sport airplane was a high-wing pusher configuration, equipped with a Rotax 912S series engine mounted atop the cabin. According to the pilot, he was the third owner of the kit-built airplane. The airplane and engine had accumulated approximately 440 hours total time in service.

The engine design utilized both air and liquid cooling. Liquid coolant was contained primarily within the engine and radiator, but the system incorporated an expansion tank and an overflow reservoir. The translucent reservoir was mounted on the lower fuselage, which enabled ready access and quantity-check capability. The metal expansion tank was mounted on the top forward portion of the engine, and was equipped with a pressure cap to enable system pressurization at normal engine operating temperatures. The expansion tank and cap were not readily visible or accessible to a person standing at the airplane; access to the tank required a ladder or workstand. The airplane was equipped with temperature gauges for the coolant and engine oil. The engine manufacturer's Operator's Manual requires that the coolant level in the expansion tank be verified as a "Daily Check."

Automated weather observations from several airports near the accident location about the time of the accident included calm winds; clear skies; temperature values about 16 degrees C; and dew point values about minus 7 degrees C.

The airport (MZJ) that the pilot selected for his precautionary landing was equipped with a single paved runway (12/30) that measured 6,849 feet by 150 feet. Airport elevation was 1,893 feet. The airport was not equipped with an air traffic control tower. The terrain around the airport was typically flat hard-packed desert floor with some scrub vegetation.

The floor of the water catchment basin was level, hard-packed desert soil, free of vegetation and rocks. The ground scars measured about 40 feet long, and were consistent with the pilot's account of a stall-induced high-descent-rate impact in an approximate nose-level attitude. The right main landing gear was deformed up and aft, the fuselage bottom sustained crush damage, and both wing tips were deformed upwards about 15 degrees. The cockpit/cabin was not compromised. All flight controls remained attached, and control continuity was established for all.

The engine oil tank, mounted atop the fuselage forward of the engine, contained the proper amount of oil. The oil appeared clean and free of debris. The coolant overflow reservoir was approximately half full. The coolant radiator, mounted on the underside of the fuselage, sustained significant crush and tearing damage, and was void of coolant. No coolant stains were observed on the ground beneath the radiator. The pressure cap for the coolant expansion tank was found improperly secured, and no coolant was found in the tank. Coolant stains were found on the engine and airframe downstream of the expansion tank.