Emmett, ID, USA
N6399B
CESSNA 182A
The pilot reported that he fueled the tanks to their full capacity with a mixture of 100LL and automobile gas prior to departing. During the return flight, as the pilot descended to the destination airport, the engine lost power and the pilot force-landed the airplane in a field. A postaccident examination revealed fuel in the right wing, but the fuel line from the left wing to the fuel selector had separated during the accident, allowing the remaining fuel in the left tank to drain out. Examination of the engine revealed no preimpact mechanical anomalies. The airplane was operating in conditions conducive to serious icing at glide power at the time of the accident. The pilot did not apply carburetor heat until after the engine power was lost. An airplane user's group reported that the specific make/model airplane is susceptible to developing carburetor ice and the use of automobile gas also increases the likelihood of carburetor ice.
HISTORY OF FLIGHT On August 2, 2011, about 1040 mountain daylight time (MDT), a Cessna 182A, N6399B, experienced a loss of engine power during cruise flight and the pilot force-landed the airplane in a field in Emmett, Idaho. The private pilot sustained serious injuries and the airplane was substantially damaged. The pilot was operating the airplane under Title 14 Code of Federal Aviation Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed. The pilot departed Fish Lake USFS Airport, Fish Lake, Idaho, about 0900, and was destined for Emmett Municipal Airport. The pilot stated that he was returning from a camping trip. He departed on July 29, with the airplane's fuel tanks filled to capacity using a mixture of 100 low lead and auto gas. The pilot fueled the airplane using a personal supply of fuel. He estimated approximately 4 hours of flight time had accrued on the airplane since he had refueled. Approximately 10 miles from Emmett, the engine lost power. He attempted repositioning the fuel selector from "Both" to "Right" and then "Left", but power was not restored. Prior to the loss of engine power, carburetor heat had not been applied, but was positioned "On" following the power loss. The pilot landed the airplane in a field, and during the landing roll, the nosewheel dug into the soft earth, and the airplane spun and came to rest right wing low. The FAA inspector that responded to the accident site reported seeing fuel in the right wing after opening the fuel cap. He was unable to access the left tank. When recovery personnel arrived to retrieve the airplane the following day, they found no fuel. Later examination revealed a separation of the left tank fuel line to the fuel selector. According to the pilot operating handbook for the airplane, the fuel capacity of the airplane is 65 gallons, with 3 unusable in straight-and-level flight. Usable fuel for all flight conditions is 55 gallons. The pilot indicated that the airplane averaged a fuel burn of 12 gallons per hour, which would have provided approximately 4.6 hours of usable fuel in all flight conditions. TESTS AND RESEARCH Wreckage Examination The wreckage of N6399B, a Cessna 182A, was examined on August 29, 2011, at Buckeye Aviation, Caldwell, Idaho. Representatives from the NTSB, FAA, and Continental Motors were present. Personnel from Buckeye Aviation, the recovery company, indicated that during the recovery, the gascolator was 3/4-full of fuel. The drain on the carburetor was opened and an estimated 1/2-cup of fuel drained out. The carburetor heat control was found in the "On" position. The Continental Motors O-470-416B engine was examined. Continuity from the throttle, propeller, mixture, and carburetor heat cockpit controls to the engine was confirmed. The top spark plugs were removed from the engine and according to the Champion Check-A-Plug chart, the electrodes showed normal wear and deposits. The valve covers were removed. The engine was rotated through the upper left accessory drive. Cylinder compression and valve continuity was established. The magnetos sparked during rotation. The right side exhaust stack sustained impact damage. The propeller was removed. There was no damage to the flange. The cylinders were borescoped and the combustion chambers had a heavy layer of deposits. The valves were undamaged. The carburetor and the induction air box were removed and examined. No residual fuel remained in the carburetor and the floats were intact. The screen was clear. The air box filter was oil soaked and sustained crush damage but there was no evidence of blockage. The tachometer read 2582.1 hours. The oil filter indicated that it was last changed on October 27, 2010 at a total time of 2573.1 hours. The airplane was not equipped with a carburetor air temperature gauge. The fuel selector handle and control rod was separated from the selector. The left port was open to the engine. The right port was closed. The left fuel tank fuel line was separated from the selector. The gascolator was removed and had sustained impact damage. No fuel was present. Mud had entered the top portion of the gascolator but it was not present on the fuel inlet side of the filter screen. The fuel caps were examined. The right cap was replaced in 2007 with a new metal fixture. The left cap (venting cap) was not. The gaskets surrounding the left fuel cap were dry. The gasket covering the vent was pliable and minor corrosion was present underneath. The left fuel tank vent was clear. The bladder fuel tanks were not breached. The fuel tank filter for the left tank was clear. The right filter was not found. Global Positioning System (GPS) Device The pilot owned and was operating a Garmin GPSMAP 196. The Garmin GPSMAP 196 is a portable GPS unit capable of storing date, route of flight, and flight time information for up to 50 individual flights in the form of a flight log. A detailed tracklog – including latitude, longitude, date, time, GPS altitude, and groundspeed information – is stored within the unit whenever the receiver has a lock on the GPS navigation signal. All recorded data is stored in non-volatile memory. The unit contains hardware and software permitting the download of recorded waypoint, route, and tracklog information to a PC via a built-in serial port. The device was sent to the NTSB Vehicle Recorder Division for examination. The unit was powered and startup was consistent with normal operation. GPS data was downloaded using normal methods and Garmin's Mapsource software. Four flights were recorded from the pilot's original departure from Emmett to Fish Lake, the flights to and from Idaho County, and the final flight from Fish Lake to Emmett. Data from the accident flight showed that the airplane's altitude climbed to approximately 10,000 feet at 15:58:03, and then showed a gradual descent. The groundspeed ranged from approximately 110 to 120, then at 16:38:15, at 3,770 feet, the groundspeed decreased to 100 knots, and the final groundspeed and altitude recorded at 16:39:48 were 62 knots and 2,874 feet, respectively. The total duration of flight time since the last refueling, based on the powered operation of the GPS device, was 4 hours, 9 minutes, and 22 seconds. ADDITIONAL INFORMATION Cessna Pilots Association Information According to the Cessna Pilots Association publication "1956 through 1986 Cessna 182 Fixed Gear Skylane Buyers Guide Excerpt", it states in part, "The Cessna 182 Skylane is prone to developing carburetor ice. The reason for this is because the design of the induction system has the carburetor positioned well below the engine in the cowling and away from the warm air around the engine. Because of this tendency towards carburetor ice many Cessna 182 Skylanes were delivered with a carburetor temperature gauge. The Cessna Pilots Association has strongly recommended to its members that they utilize carburetor heat in such a manner as to keep the carburetor temperature indication out of the yellow zone of the gauge. This may only require the use of partial carburetor heat, a practice that in standardized flight training is considered a poor procedure, being taught that carburetor heat should be all or nothing. The carburetor icing characteristics of the Cessna 182 Skylane make partial carburetor heat an acceptable practice for this aircraft." Additionally, it states, "1956 through 1976 model year Cessna 182 Skylanes can receive STC approval to operate on auto gas. The makeup of auto gas coupled with the Cessna 182 Skylane's induction system produce a couple of interesting operating characteristics. First of all because auto fuel vaporizes more readily than aviation gas it is possible to develop carburetor ice at higher outside air temperatures on auto gas than on aviation gasoline. The amount of ice that is produced remains the same but pilots will notice carburetor icing occurring at higher air temperatures on auto gas than they are used to experiencing with aviation fuel. Another characteristic on auto fuel is that when the engine is shut down, remaining auto fuel in the induction system will condense in the intake tubes, run back down to the carburetor and drain out on the ground." Carburetor Icing Information The carburetor icing probability chart from Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin (SAIB): CE-09-35 Carburetor Icing Prevention, June 30, 2009, shows a probability of serious icing at glide power at the temperature and dew point reported at the time of the accident. Notice to Airman (NOTAM) According to a notice to airman (NOTAM) for Emmett, at the time the pilot intended to land, the airport runway was closed.
A total loss of engine power due to carburetor icing because the pilot did not use carburetor heat.
Source: NTSB Aviation Accident Database
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