History of Flight
On October 30, 2018, about 0924 Pacific daylight time, a Cessna 180D airplane, registration N6414X, was substantially damaged during an accident near Cottonwood, California. The private pilot sustained serious injuries. The flight was conducted under Title 14 Code of Federal Regulations Part 91 for personal purposes.
The pilot was en route to a mechanic’s facility for maintenance. Approximately 4 miles from the destination, at an altitude of about 2,500 ft, the pilot extended the wing flaps about 20° and reduced speed to about 65 mph. When the airplane was about 1.5 miles from the runway threshold, at about 1,500 ft and with a manifold pressure setting of about 17 inches, the pilot advanced the throttle to add power but received no response. The pilot cycled the mixture and magnetos without change, and the airplane descended below the desired glidepath. The pilot did not use carburetor heat during the approach or in an attempt to restore engine response.
Because the airport was situated on a bluff about 300 ft higher than the surrounding flat terrain, the pilot chose to conduct an off-airport landing in a field. During the approach, the pilot observed power lines and attempted to maneuver over them. He glanced at the airspeed indicator and saw 40 mph. The airplane then experienced an aerodynamic stall and “pancaked” onto the ground.
The airplane came to rest upright in a level field about 3,300 ft short of the runway threshold. The engine cowling and forward fuselage were crushed and fractured, and the right-side cabin door separated.
Aircraft Information
The most recent annual inspection was completed in September 2018, with about 25 hours flown since. The Owner’s Manual BEFORE LANDING checklist specified that the fuel selector valve should be set to “BOTH” (ON). The manual’s landing guidance included two mentions of carburetor heat: the LET-DOWN checklist stated “Apply enough carburetor heat to prevent carburetor icing if icing conditions exist,” and the BEFORE LANDING checklist stated “Apply carburetor heat before closing throttle.”
Meteorological Information
Weather observations from Redding Municipal Airport (RDD), about 10 miles north, at 0853 included wind from 340° at 9 knots gusting to 15 knots, 10 miles visibility, clear skies, temperature 15°C, dew point 1°C, and altimeter 30.20 inches of mercury. At 0953, conditions were wind from 340° at 10 knots gusting to 19 knots, 10 miles visibility, clear skies, temperature 17°C, dew point 1°C, and altimeter 30.21 inches of mercury. When plotted on a carburetor icing chart, the temperature and dew point values fell within envelopes labeled “Icing (glide and cruise power)” or “Serious Icing (glide power).”
Wreckage and Impact Information
The left main landing gear was fracture-separated, and the outboard left wing was crumpled. One blade of the two-blade propeller was bent aft; the other was undamaged. No fire occurred. Both fuel caps were secure. The responding fire chief found the fuel selector valve set to the left tank and turned it to the BOTH OFF position. Law enforcement photographs showed the carburetor heat control in the full-forward (off) position. The mechanic who previously worked on the airplane responded and noted no fuel leakage externally or on the ground.
Examination revealed the airplane impacted the ground before reaching the power lines, slid about 75 ft, and came to rest under them. No fuel or oil leaks were evident. The fuel selector valve was tested with low-pressure air and water and functioned per design in all positions.
The engine was relatively undamaged. Parts of the exhaust system were crushed or displaced, and the carburetor airbox was crushed. The forward oil sump pan was pushed in but not breached. Throttle and mixture cables had been cut by the recovery mechanic; their cockpit controls moved freely. The carburetor heat control cable was uncut and continuous, but the control and door were extremely difficult to move. The magnetos and accessories remained attached. Spark plugs exhibited clean, normal electrodes. The crankshaft rotated freely with thumb compression on all cylinders.
Engine testing in a test cell involved reinstalling the carburetor. Magneto timing was 2° advanced from the specified 22°. The engine started and ran at various rpm except the 2,600 rpm redline; maximum full-throttle rpm was about 2,485 after propeller pitch adjustment. All EGT, CHT, and oil pressure values were normal. Fuel flow at full throttle was higher than expected (21.5 gallons per hour at 2,485 rpm). The carburetor was disassembled; internal components were normal except the fuel inlet screen had several hair-like fibrous strands, but their size and quantity were insufficient to reduce fuel flow.
Examination and testing did not reveal any reasons for the power loss reported by the pilot. The inability to reach redline rpm was likely due to an overly rich mixture but was probably unrelated to the loss of engine power at a low power setting.
Probable Cause
No probable cause was determined; the source states that examination and testing did not reveal reasons for the reported power loss.