Torrington, WY, USA
N4911K
RYAN NAVION A
The pilot reported that he leaned the mixture while en route, but could not find the peak performance. He set the mixture control to what he thought it was appropriate for 5,000 to 6,000 feet altitude. As he entered the landing pattern at his destination, he lowered the landing gear and prepared for landing. As he reduced the throttle position, the engine lost all power, and the descent rate increased. The pilot determined that the airplane would not glide to a runway and maneuvered to an open area. The airplane touched down hard, and the landing gear collapsed. The airplane sustained substantial damage to the firewall and fuselage. Postaccident examination of the airframe and engine revealed no mechanical malfunctions or failures that would have precluded normal operation. The carburetor was removed and connected to a test cell. The unit was found out of limits at the low end of its operating range. Thus, with the fuel mixture leaned and a subsequent reduction in the power for landing, a temporary disruption of the fuel flow caused the engine to sputter and lose power.
On July 24, 2011, about 1840 mountain daylight time, a Ryan Navion A, N4911K, made an off airport forced landing following a loss of engine power at Torrington, Wyoming. The pilot/owner was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The private pilot and three passengers sustained minor injuries; the airplane sustained substantial damage to the firewall and fuselage from impact forces. The cross-country personal flight departed North Platte, Nebraska, about 1635, with a planned destination of Torrington. Visual meteorological conditions prevailed, and no flight plan had been filed.The pilot stated that about 30 to 45 minutes from Torrington he tried to lean the mixture, but could not find peak. He continued to lean the mixture looking for engine roughness, but become concerned that he would hit cut off, and stop the engine. He set the mixture control to where he thought it was appropriate for 5,000 to 6,000 feet, which was about 1/2 inch extended from full rich. The pilot reported that he descended the airplane over the airport, and flew upwind along the runway to check the wind sock and for obstructions. At the end of runway 010 about 1,000 feet above ground level (agl), he made a left turn to the downwind leg with the landing gear and flaps down. After he leveled the airplane, he started to reduce the throttle, and the engine lost power. The pilot lowered the airplane's nose, and thought that the airplane could glide to runway 20. The airspeed got lower so he lowered the nose some more, but realized that the airplane would not make the other runway. As the airplane rapidly descended, he maintained a wings level attitude, and flew straight ahead toward open terrain. Just before impact, he flared the airplane, and it touched down hard onto its main wheels followed by the nose wheel. The propeller contacted the ground, and both main landing gear collapsed. The airplane skidded about 80 feet before it stopped, and everyone exited the airplane. The airframe and engine were examined at Beegle's Aircraft in Greeley, Colorado, on August 24, 2011. The carburetor was examined at Front Range Fuel Systems in Loveland, Colorado, on August 26, 2011. Detailed reports of the exams are part of the public docket for this accident. Airframe Exam The wings had been removed during recovery. The fuselage did not have any signs of oil along its sides. The bottom of the nose cowl sustained inward crush damage at the air filter, which was packed with dirt and grass. No preimpact mechanical malfunction or failure was found with the airframe that would have precluded normal operation. Engine Exam Postaccident examination of the engine was conducted with the engine while in place on the airframe. At the conclusion of the examination, no mechanical malfunctions or failures were found that would have precluded normal operation. Carburetor Exam The carburetor was a Bendix P55C, part number 380223-8, serial number 723670. As the testing technician removed fittings from the carburetor to set it up on the test bench, fluid dripped out of all fittings. The carburetor was connected to the test cell. The unit was out of limits at the low end of the test flows. The technician stated that if the pilot had the airplane leaned and pulled the throttle back, there could be a temporary disruption of the fuel flow. This could cause the engine to sputter and lose power.
The carburetor’s failure to meet its operating limits at the low range, which resulted in a loss of engine power when the pilot reduced power for landing.
Source: NTSB Aviation Accident Database
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