New Cuyama, CA, USA
N89671
Cessna 140
The engine lost power while the airplane was in cruise flight and the airplane collided with obstacles and rough terrain during a forced landing. During cruise flight at 5,500 feet, the pilot felt a vibration in the engine. The vibration seemed to go through the entire airframe. The pilot applied carburetor heat for approximately 20 seconds. He removed the carburetor heat because it did not seem to help the situation and the engine began sputtering. He pulled the power back and began descending, attempting to troubleshoot the problem. The condition worsened and the pilot attempted to climb the airplane but there was not enough power available. All of the engine gauges appeared "in the green" and the pilot could not recall the rpm reading. The pilot and passenger began searching for a place to land and crash-landed into a tree in a crevice in the mountain. The temperature/dew point spread at 4,000 and 5,000 feet mean sea level indicated that moderate carburetor icing conditions existed at cruise power, when compared to a carburetor icing chart. According to the pilot operating handbook for the Cessna 140, "The correct way to use carburetor heat is to first use full heat to remove any ice that is forming." Post accident examination of the engine and airframe did not reveal any mechanical malfunctions that would have resulted in a loss of power.
HISTORY OF FLIGHT On May 8, 2005, about 1000 Pacific daylight time, a Cessna 140, N89671, collided with mountainous terrain about 13 miles west-southwest of New Cuyama, California. The airplane sustained substantial damage; the private pilot and one passenger were seriously injured. The pilot was operating the privately registered airplane under the provisions of 14 CFR Part 91. The airplane departed Santa Ynez Airport, Santa Ynez, California, about 0900, and the pilot planned to return to Santa Ynez Airport about 1000. Visual meteorological conditions prevailed for the local area personal flight. The airplane was reported as missing on May 9. An Alert Notice (ALNOT) was issued on May 9 at 1141. On May 9, at 1500, the airplane wreckage and its occupants were located in mountainous terrain, in a ravine. The approximate elevation of the accident site was 3,200 feet mean sea level (msl). Based on reports from emergency responders, the walls of the ravine were lined in steep rock, and a shallow stream flowed down it. The airplane was in this stream; its longitudinal axis perpendicular to the stream's flow. The immediate surrounding terrain was covered in thick brush. The fuselage of the airplane vertically compressed downward. Approximately 10 feet above the stream, there was an impact mark on the steep rock that lined the ravine. The pilot was interviewed by the National Transportation Safety Board investigator on June 27. The pilot stated that he arrived at the airport about 0845 to perform his preflight. He fueled the airplane so that each tank was 3/4 full, which equated to approximately 3 hours of flight time. The purpose of the flight was to look for wildlife because his passenger was a hunter. The pilot planned to take his boss flying at 1000, so the duration of the flight was to be 1 hour. The passenger was a long-time friend of the pilot. On the morning of the accident, the passenger called the pilot and said that he would like to go flying with him. The passenger had flown with the pilot on previous occasions. The pilot and passenger departed Santa Ynez airport at 0900, and flew toward Figueroa Mountain. They also flew over a cabin where the passenger's father was staying. The pilot transitioned to the northeast toward New Cuyama at elevations between 3,500 feet and 5,500 feet msl. When they reversed course to return to Santa Ynez, approximately 25 minutes into the flight, the pilot felt the engine "rock" while established in cruise flight at 5,500 feet msl. The vibration seemed to go through the entire airframe. He applied carburetor heat for approximately 20 seconds. He removed the carburetor heat and the engine began sputtering. He pulled the power back and began descending, attempting to troubleshoot the problem. The condition worsened and the pilot attempted to climb the airplane but there was not enough power available. All of the engine gauges appeared "in the green" and the pilot could not recall the rpm reading. The pilot and passenger began searching for a place to land and crash-landed into a tree in a crevice in the mountain. The airplane impacted the terrain about 0930, and the engine was producing power until impact. The pilot was aware of previous possible encounters with carburetor ice in the airplane. The first occurrence was with the airplane's prior owner when he force-landed the airplane on a beach in Florida. The pilot recalled one situation when he was flying with his father and the engine made a similar "rock" and his father mentioned that carburetor icing may have been the cause. No carburetor heat was applied. On another occasion, the pilot encountered a vibration while coming in to land and applied carburetor heat through the landing. METEOROLOGICAL INFORMATION A Safety Board meteorologist examined the weather for the time frame surrounding the accident. The National Weather Service (NWS) weather depiction chart depicted a small area of instrument flight rules (IFR) to marginal visual flight rules (MVFR) conditions near the coastal sections of southern California, with visual flight rules (VFR) conditions prevailing across southern California, including over the accident site. Observations showed VFR conditions prevailing prior to the accident with a band of low stratiform clouds moving in along the coastal sections. The wind profile indicated low-level winds from the north at less than 10 knots through 5,000 feet. Winds then backed to the northwest and west with height and increased in speed. Winds did not exceed 30 knots through 18,000 feet, and no strong vertical wind shears were noted to support any turbulence. Satellite imagery showed the accident site clear of clouds. The temperature and dew point at 4,000 feet was 50 degrees Fahrenheit (F) (8 degrees Celsius (C)), and 41 degrees F (5 degrees C). The temperature and dew point at 5,000 feet was 46 degrees F (8 degrees C) and 35 degrees F (2 degrees C). A carburetor icing chart published in the Federal Aviation Administration (FAA) Tips on Winter Flying (FAA-P-8740-24) showed at 4,000 and 5,000 feet msl, moderate icing conditions existed at cruise power. TESTS AND RESEARCH The airframe and engine was examined on June 1, 2005, by the Safety Board investigator-in-charge (IIC) and representatives from Teledyne Continental Motors, Cessna Aircraft Company, and the FAA, all parties to the investigation. The Teledyne Continental engine model O-200-A, serial number 1997-30-9-A, was slung from a hoist and examined. The mixture control was in the full rich position at the carburetor and the control arm rotated freely. The locking nut on the mixture cable was not tightened but the mixture cable could not be pulled by hand through the bolt and was secure. The throttle position at the carburetor was mid-range. The carburetor heat housing was crushed. The engine was rotated and thumb compression was obtained on all four cylinders, in firing order. The crankshaft was bent at the propeller flange. The top spark plugs were removed and visually examined in comparison to a Champion Aviation Check-A-Plug chart. The spark plug from cylinder number one was broken into two pieces and the electrode was circular and light gray in color. The electrode for cylinder number 2 was oval and gray in color. The electrode for cylinder for number 3 was circular and gray in color. The electrode for cylinder number 4 was circular and gray in color. Spark plugs from cylinders 1, 3, and 4 were consistent with normal operation when compared to the Champion Check-A-Plug chart. The spark plug from cylinder number 2 had a small amount of lead but was otherwise consistent with normal operation when compared to the Champion chart. The lower plugs were examined using a borescope and no anomalies were noted. The coloration of all the cylinders was consistent with normal wear. The carburetor was removed and examined. The floats were intact and were not crushed. The accelerator pump shaft gasket was intact and the accelerator pump pumped fuel when the pressure was applied. Less than an ounce of fuel was in the carburetor. Sar-gel paste was used for evidence of water. No evidence of water or contaminants was detected in carburetor. The fuel smelled consistent with 100LL. The Champion Aircraft filter (Model CH48109-1) was removed and examined. The filter was marked with "Tach 1275.7, 4-4-05." The filter was free from contaminants and the oil was light brown in color. The propeller was removed and examined. Blade 1 had light chordwise scratching 13 inches from the hub and leading edge gouging. There was leading edge gouging approximately mid-blade. Blade 2 was bent aft 18 inches from the spinner. Leading edge gouging was present approximately 9 inches from the hub. The blade was curled toward the blade face and twisted. The airplane's wings had been removed for recovery. The engine remained attached to the firewall and instrument panel and the fuselage was cut about mid-fuselage during recovery. The tachometer indicated 1,287.49. The occupiable space of the cabin had been reduced more than 40 percent. The magneto switch was in the off position. The throttle position was 1 ½ -inch and the mixture was in the full-rich position. The carburetor heat was in the off position. The primer was in and locked. On June 23, 2005, the magentos were bench-tested and disassembled at Aero Accessories, Van Nuys, California, with the IIC and a representative from Aero Accessories present. The gear and harnesses were removed on both magnetos to facilitate the test run. Prior to the gears removal, the gears were turned and both produced a clicking sound. The right magneto (SN 940300075) and left magneto (SN 940300077) were secured to the test bench at separate intervals and a testing harness was installed. The minimum gap requirement for the magneto is 5 millimeters. The magneto tested to 10 millimeters utilizing the impulse coupling. The rpm was increased to 1,500 and the same results were obtained. Both magnetos were bench tested and operated successfully. The magnetos were disassembled. The lead to the capacitor was intact and there was no evidence of capacitor malfunction. The e-gap and distributor gear timing was checked using a timing light machine. The magneto was timed in accordance with specifications. The distributor block was removed and both the gear and block were intact. A T150 timing tool was used to check the e-gap timing with the distributor block removed. The magneto was timed within specifications and no internal problems were noted. The impulse coupling was removed. The spring was intact and the impulse coupling paws were measured using a T155 gauge. The paws were within specified minimums. During the post accident examination, investigators noted that the right wing flap attach point weld was fractured. The inboard portion of the right flap and a section of the flap control tube were sent to the Safety Board Materials Laboratory for examination. The examination was completed on August 8, 2005. The metallurgist observed general corrosion on the control attachment fitting, appearing uniform and limited to the surface. The overall deformation of the control attachment fitting was consistent with the overstress fracture at the lower and aft sides of the stub occurring before fracture at the upper side. The full factual report (Report Number 05-090) is contained in the docket information for this accident file. The Trimble TNL 2000 Approach global positioning system (GPS) was sent to Free Flight Systems for download. The last data retrieved by the unit was on May 8, 2005, at 1032. Additional data retrieved included pre-programmed waypoints and user profiles. The full data download is contained in the docket information for the accident file. ADDITIONAL INFORMATION According to the Santa Ynez airport manager, the airplane was refueled with 7 1/2 gallons of 100 Low Lead (LL) the morning of the accident. Blood samples taken from the pilot immediately following the accident at the hospital were discarded and no toxicological testing was performed. According to the pilot operating handbook for the Cessna 140, "The correct way to use carburetor heat is to first use full heat to remove any ice that is forming." The FAA "Tips on Winter Flying" (P-8740-24) summarizes carburetor icing. There are three main types of carburetor ice: impact ice; fuel ice; and throttle ice. "In general, carburetor ice will form in temperatures between 32-50°F when the relative humidity is 50 percent or more. If visible moisture is present, it will form at temperatures between 15-32°F. A carburetor air temperature (CAT) gauge is extremely helpful to keep the temperatures within the carburetor in the proper range. Partial carburetor heat is not recommended if a CAT gauge is not installed. Partial throttle (cruise or letdown) is the most critical time for carburetor ice. It is recommended that carburetor heat be applied before reducing power and that partial power be used during letdown to prevent icing and overcooling the engine." In order to prevent carburetor icing the FAA recommends using carburetor heat during the ground check, using carburetor heat while operating in the icing range, and using heat on approach and descent. The warning signs include a loss of rpm in airplanes equipped with a fixed pitch, and a drop in manifold pressure in airplanes equipped with a constant speed propeller. In order to counteract carburetor icing, the pilot should do the following: apply full carburetor heat immediately. It was noted in the publication that the engine "may run rough initially for a short time while ice melts." The wreckage was released to the owner's representative on August 16, 2005. The Trimble GPS, 4-foot section of the flap control bar, and magnetos were released to Aircraft Recovery Service on August 9, 2005. The remaining flap pieces were released to Aircraft Recovery Service on August 16, 2005. No parts or pieces were retained.
the pilot's failure to properly use carburetor heat during conditions conducive to carburetor icing, which resulted in the loss of engine power. A factor in the accident was the unsuitable landing terrain.
Source: NTSB Aviation Accident Database
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