History of Flight
On July 21, 2018, at 1155 central daylight time, a Cessna 210C, registration N3611Y, was substantially damaged during a forced landing to a field near Blum, Texas. The airline transport pilot was uninjured. The airplane was operated under 14 CFR Part 91 as a personal flight without a flight plan. Day visual meteorological conditions prevailed. The flight departed from Granbury Regional Airport (GDJ), Granbury, Texas, and was destined for Hilltop Lakes Airport (0TE4), Hilltop Lakes, Texas.
The pilot reported that she completed a preflight inspection and sumped the fuel system, finding no water or contaminant. Her first engine start attempt was unsuccessful; after waiting about 30 minutes for the starter to cool, the second attempt resulted in normal engine start and run-up. After takeoff, the airplane departed the traffic pattern and proceeded on course at cruise-climb airspeed with normal engine indications. At a cruise altitude of 3,500 ft mean sea level, power was set to 22 inches manifold pressure and 2,200 rpm, with mixture at 13 gallons per hour.
About 20 minutes after departure, the engine began to run rough. Suspecting vapor lock due to hot weather, the pilot switched the fuel selector from right to left tank, but roughness worsened, so she returned it to the right tank. Selecting the boost pump to LOW then HIGH had no effect. The engine rapidly lost power. Retarding the throttle did not help. At about 1,000 ft above ground level, the pilot selected a field for forced landing. She complied with the aircraft manufacturer's procedure, landing with gear retracted because the engine-driven hydraulic pump was windmilling. She selected flaps to 30 degrees and advanced the throttle to silence the gear warning horn. On short final, she turned the ignition switch OFF. The touchdown was firm, and the airplane slid to a stop. She estimated 2 minutes elapsed from onset of roughness to landing.
The pilot explained she did not lower the landing gear because the checklist stated not to lower it, and manually pumping it down would take about 3 minutes. She said she preferred focusing on flying rather than pumping gear during approach, and landing with partially extended gear would be worse. She noted insufficient time at the altitude during the approach. When asked whether she advanced the mixture to full rich when roughness occurred, she did not remember; she said she did not change mixture after landing. The mixture was slightly leaned due to low cruise altitude. She thought she might have moved mixture to full rich during restart attempts, but available time was very short.
Aircraft Information
The airplane was a 1963 Cessna 210C equipped with a Continental IO-470-S2 engine, serial number CS-102886-3-A-I, last overhauled upon installation on January 15, 1976, with 474.45 hours since overhaul. The pilot held an airframe and powerplant mechanic certificate and performed maintenance on the airplane. She owned it since new in 1962, last flown in 2003, and resumed flying in 2004. The last annual inspection was in September 2018. She suspected the power loss was due to vapor lock, citing two prior occurrences on hot days: on May 29, 2003, a power loss occurred during landing rollout at idle; on July 19, 2003, en route, the engine ran rough and quit, restarted after rapid throttle retard, then died on landing rollout. After the July 2003 event, fuel lines in the engine compartment were replaced, and the electric boost pump system was modified (removing a solenoid valve and replacing two boost pumps with one) to the configuration of Cessna 210D airplanes under a major repair and alteration dated September 2, 2004.
The Owner's Manual stated flaps are hydraulically operated by the same system as landing gear. The landing gear is extended and retracted by hydraulic actuators powered by an engine-driven hydraulic pump. The forced landing procedure advised: "(5) If field is smooth and hard, extend the landing gear within gliding distance of field. (6) If engine is windmilling, extend flaps as necessary within gliding distance of field." The manual did not require manual extension of gear following power loss.
Post-Accident Examination
A post-accident examination by an FAA inspector revealed the airplane resting on a flat, dry dirt field with gear retracted and flaps at 30 degrees. The field had not rained for about six weeks and the surface was hard, similar to some turf airstrips. Master switch, ignition key, boost pump switch, and fuel selector were OFF. Throttle and propeller controls were full forward; mixture was near idle cutoff. Left and right fuel tanks each about half full of 100LL fuel. The fuselage was wrinkled.
After recovery, the engine was test run under NTSB supervision. The fuel supply was plumbed into the left wing tank lines. Top spark plugs were removed and exhibited normal operation. The engine started immediately, warmed up, and operated normally through magneto check and full power. A second test run using the right wing tank lines yielded similar results, with no fuel leaks.
The fuel selector was removed and examined, showing no blockage or mechanical anomalies. The fuel pump, fuel servo, and manifold valve were removed for flow testing at Continental Motors. The fuel pump produced adequate flow and pressure. Bench testing of the fuel servo and manifold valve did not meet factory specifications for new parts; fuel injection systems must be set up and adjusted per engine-airframe combination. The throttle body/metering unit had an internal O-ring leak during bench testing, but no leaks were present during the engine test run.