N3611YCessna 210C · 1962

On July 21, 2018, at 1155 central daylight time, a Cessna 210C, N3611Y, was substantially damaged during a forced landing to a field near Blum, Texas. The airline transport pilot was uninjured. The airplane was registered to and operated by the pilot under Title 14 Code of Federal Regulations Part 91 as a personal flight that was not operating on a flight plan. Day visual meteorological conditions prevailed at the time of the accident. The flight departed from Granbury Regional Airport (GDJ), Granbury, Texas, and was destined to Hilltop Lakes Airport (0TE4), Hilltop Lakes, Texas.

The pilot stated that she completed a preflight inspection during which she sumped the fuel system. The fuel sump samples did not contain water or contaminant. She said that her first attempt to start the engine was unsuccessful, so she waited about 30 minutes for the starter to cool before attempting another start. Upon the second start attempt, the engine started and "ran normally," and the subsequent engine run-up was "normal".

After takeoff, the airplane departed GDJ traffic pattern and proceeded on course at a cruise-climb airspeed; all "engine indications were "normal". Upon reaching a cruise altitude of 3,500 ft mean sea level, engine power and speed were set to 22 inches of manifold pressure and 2,200 rpm, and the mixture was set to 13 gallons per hour. About 20 minutes after departure, the engine began to run "rough" and because of the hot weather conditions the pilot suspected vapor lock. She switched the fuel selector position from the right to the left fuel tank, but the engine roughness worsened so she switched the selector back to the right fuel tank. She then selected the boost pump to LOW and then HIGH, but those selections had no effect on the engine roughness. The engine began to lose power rapidly. The pilot retarded the throttle control but that did not affect the engine.

About 1,000 ft above ground level, the pilot selected a field for a forced landing. She said that she complied with the aircraft manufacturer's procedure and landed on the field with landing gear retracted because the engine driven hydraulic pump was being powered by a windmilling engine. She selected flaps to 30 degrees and advanced the throttle control to silence the gear warning horn. On short final to the field, she turned the ignition switch OFF. She said that the landing touchdown was "firm," and the airplane slid to a stop very quickly. She estimated that 2 minutes elapsed from the onset of engine roughness to landing.

The National Transportation Safety Board (NTSB) Investigator-in-Charge (IIC) asked the pilot why she did not lower the landing gear for the forced landing; she said the airplane checklist stated that the landing gear was not to be lowered, and that it would take her about 3 minutes to manually pump the landing gear down. She said it would take her about 3 minutes to manually pump the landing gear down during landing gear swing tests that she did during the airplane's maintenance. She said the 3 minutes was without air loads on the airplane because it was a gear swing test with the airplane on jacks. She said that she would rather focus on flying the airplane rather than pumping the landing gear during the approach for the forced landing. She said that the outcome landing with the landing gear partially extended would have been worse than landing with the gear retracted. She said the she did not have enough time to lower the landing gear due to the altitude the airplane was at during the approach to a field. She said there is no way to tell if a field is rough while the airplane is 2 miles away from the field.

When the pilot was asked on separate occasions by the NTSB IIC and the FAA inspector whether she advanced the mixture control to the full rich position when the engine roughness occurred; she said that she did not remember. She said that she did not change the mixture control position after the forced landing. The pilot later stated that the mixture was only slightly leaned because of the low cruise altitude. She said its normal while flying the accident airplane to start leaning as climb power is set, or even during takeoff from high elevation airports. She said that at some point in trying to restart the engine, she thought that she moved the mixture to full rich, but it wasn't much of a move. She said the time available to attempt a restart was very short.

The airplane was equipped with a Continental IO-470-S2, serial number CS-102886-3-A-I, engine that was last overhauled at the time of installation onto the airframe, dated January 15, 1976. At the time of the accident, the time since overhaul of the engine was 474.45 hours.

The pilot held an airframe and powerplant mechanic certificate and performed maintenance on the airplane. The pilot stated she owned the airplane since its new purchase in 1962 and was last flown in 2003. In 2004 she decided to begin flying the airplane. The airplane received its last annual inspection in September 2018. She suspected that the loss of engine power occurred at the time of the accident was due to vapor lock because of two prior occurrences of power losses that occurred on hot days, as follows:

On May 29, 2003 from a flight from Mineral Wells Airport (MLW), Mineral Wells, Texas to Horseshoe Bend Airport (F78), Weatherford, Texas the airplane experienced an engine power loss occurred during landing rollout when the engine was at idle and would not restart. She said the idle speed was adjusted "slightly" and subsequent engine starts and ground runs were normal "once the engine had cooled."

On July 19, 2003, while en route from F78 to Easterwood Field Airport (CLL), College Station, Texas, the engine ran rough and subsequently quit. The engine was restarted after the throttle was retarded rapidly to idle from where it had been set for cruise. The engine ran from there until landing at Marlin Airport (T15), Marlin, Texas and died again on landing rollout. The following day the engine started and ran normally through a full-power ground run. An airframe and power plant mechanic with inspection authorization helped her in draining every sump, checking every vent, and checking every fuel filter that we could access. Nothing out of the ordinary was found.

The pilot stated that following the engine power loss on July 19, 2003, all the fuel lines in the engine compartment were replaced. She said that the airplane electric boost pump was modified after both losses of engine power due to a sticking solenoid valve in the fuel/vapor return line between the engine driven fuel pump and fuel selector. The removal of the solenoid valve and replacement of two electrically-driven fuel boost pumps with one fuel boost pump was completed through a major repair and alteration dated September 2, 2004, to modify the fuel boost pump system to the configuration installed in Cessna 210D airplanes.

The 1963 Cessna 210C Owner's Manual stated that flaps are operated hydraulically by the same system that operated the landing gear. The airplane retractable tricycle landing gear is extended and retracted by hydraulic actuators, powered by an engine-driven hydraulic pump.

The Owner's Manual Forced Landing (Complete Engine Failure) procedure stated, in part, "(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 Owner's Manual does not require manual extension of the landing gear following engine power loss.

The airplane was equipped with a Continental IO-470-S2, serial number CS-102886-3-A-I, engine that was last overhauled at the time of installation onto the airframe, dated January 15, 1976. At the time of the accident, the time since overhaul of the engine was 474.45 hours.

The pilot held an airframe and powerplant mechanic certificate and performed maintenance on the airplane. The pilot stated she owned the airplane since its new purchase in 1962 and was last flown in 2003. In 2004 she decided to begin flying the airplane. The airplane received its last annual inspection in September 2018. She suspected that the loss of engine power occurred at the time of the accident was due to vapor lock because of two prior occurrences of power losses that occurred on hot days, as follows:

On May 29, 2003 from a flight from Mineral Wells Airport (MLW), Mineral Wells, Texas to Horseshoe Bend Airport (F78), Weatherford, Texas the airplane experienced an engine power loss occurred during landing rollout when the engine was at idle and would not restart. She said the idle speed was adjusted "slightly" and subsequent engine starts and ground runs were normal "once the engine had cooled."

On July 19, 2003, while en route from F78 to Easterwood Field Airport (CLL), College Station, Texas, the engine ran rough and subsequently quit. The engine was restarted after the throttle was retarded rapidly to idle from where it had been set for cruise. The engine ran from there until landing at Marlin Airport (T15), Marlin, Texas and died again on landing rollout. The following day the engine started and ran normally through a full-power ground run. An airframe and power plant mechanic with inspection authorization helped her in draining every sump, checking every vent, and checking every fuel filter that we could access. Nothing out of the ordinary was found.

The pilot stated that following the engine power loss on July 19, 2003, all the fuel lines in the engine compartment were replaced. She said that the airplane electric boost pump was modified after both losses of engine power due to a sticking solenoid valve in the fuel/vapor return line between the engine driven fuel pump and fuel selector. The removal of the solenoid valve and replacement of two electrically-driven fuel boost pumps with one fuel boost pump was completed through a major repair and alteration dated September 2, 2004, to modify the fuel boost pump system to the configuration installed in Cessna 210D airplanes.

The 1963 Cessna 210C Owner's Manual stated that flaps are operated hydraulically by the same system that operated the landing gear. The airplane retractable tricycle landing gear is extended and retracted by hydraulic actuators, powered by an engine-driven hydraulic pump.

The Owner's Manual Forced Landing (Complete Engine Failure) procedure stated, in part, "(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 Owner's Manual does not require manual extension of the landing gear following engine power loss.

A post-accident examination of the accident site by a Federal Aviation Administration inspector revealed that the airplane was resting on a flat and dry dirt field with the landing gear retracted and the flaps extended to the full flap, 30-degree position. The FAA inspector stated that it had not rained for about six weeks and the surface was hard and its surface was in a condition as some turf airstrips. The master switch, ignition key switch, boost pump switch, and the fuel selector were in the OFF positions. The throttle and propeller controls were in the full forward positions. The mixture control was near the idle cutoff position. The left and right fuel tanks were each about ½ full of liquid consistent with 100 low lead aviation fuel. The fuselage was wrinkled.

Following the recovery of the airplane to a salvage facility, the engine with the airframe were secured to a trailer and the propeller replaced in preparation for and engine test run under the supervision of a NTSB Air Safety Investigator. The fuel supply to the engine was plumbed into the left wing tank fuel lines. The top spark plugs were removed and exhibited features consistent with normal operation. The plugs were then reinstalled. The engine was primed using the electric boost pump and started immediately and allowed to warm up. The propeller was cycled at an engine speed of 1,000 rpm. A magneto check was performed at an engine speed of 1,800 rpm and the corresponding reduction in speed was approximately 125 rpm. There were no anomalies when engine power was increased to full power. The external fuel supply was then plumbed into the right wing fuel tank lines and a second test run was performed with similar results. Both test runs were about 5-6 minutes in duration. There were no fuel system leaks noted during the test runs.

The fuel selector was removed, and its examination revealed no blockage and no mechanical anomalies that would have precluded normal operation.

The fuel pump, fuel servo, and manifold valve were removed for subsequent flow testing at Continental Motors under the supervision of an NTSB Air Safety Investigator. Testing of the fuel pump revealed that the pump produced adequate fuel flow and pressure for an IO-470 engine. Bench testing of the fuel servo and the manifold valve yielded results that did not meet factory specifications for a new part; fuel injection systems must be set up and adjusted to each individual engine and airframe combination. The throttle body/metering unit had a leak during benched testing. The leak during bench testing emanated from an internal O-ring. There were no leaks from the throttle body/metering unit during the engine test run.