NTSB Factual Report

HISTORY OF FLIGHT

On June 21, 2007, about 1150 eastern daylight time, a Cessna 182C, N8691T, was destroyed when it impacted terrain at Gryder-Teague Airport (NC58), Hiddenite, North Carolina. The certificated private pilot/owner and the certificated flight instructor were fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which departed Taylorsville Airport (4NC3), Taylorsville, North Carolina. The instructional flight was conducted under 14 CFR Part 91.

According to relatives, the flight was intended as training for the pilot/owner. A notation in the pilot's logbook, for a flight 1 day earlier, stated, "Instrument (illegible) Instructor."

There were no witnesses to the accident, and the extent to which a preflight inspection was performed was unknown.

According to a representative from the Air Force Rescue Coordination Center, the airplane's emergency locator transmitter signal was received by a satellite at 1150, and notification from the satellite occurred at 1204.

PILOT INFORMATION

According to Federal Aviation Administration (FAA) records, the pilot/owner, age 75, held a private pilot certificate. His latest FAA third class medical certificate was issued on July 18, 2005. The pilot/owner's logbook indicated that he had accumulated 279 hours of flight time.

The flight instructor, age 70, held an airline transport pilot certificate for airplane multiengine land, a commercial certificate for airplane single-engine land and single-engine sea, and was rated in a number of transport category airplanes. He also held a flight instructor certificate for single-engine and multiengine airplanes, and instrument airplane, and was a retired airline pilot. Accurate flight hours were not available. The instructor's latest FAA second class medical certificate was issued on May 15, 2006.

AIRPLANE INFORMATION

FAA records indicated that the airplane was manufactured in 1960, and powered by a Teledyne Continental Motors (TCM) O-470 engine. The airplane was not equipped with a carburetor temperature gauge.

A review of maintenance records revealed that on May 17, 2007, the airplane underwent an annual inspection at a facility at Statesville Regional Airport. At that time, the tachometer indicated 953.88 hours.

On May 18, 2007, the pilot had the airplane topped off with 41.5 gallons of fuel and then flew it back to Taylorsville. At the end of the flight, the pilot/owner logged a tachometer time of 954.25 hours.

On June 20, 2007, after the instrument training flight, the pilot/owner noted a tachometer time of 955.09 hours.

At the accident site, the tachometer time indicated 955.61 hours.

AIRPORT INFORMATION

Gryder-Teague Airport, which was surrounded by trees in the vicinity of the accident, had one turf runway, runway 27, which was 2,000 feet long and 60 feet wide. Airport elevation was 1,190 feet and there was no control tower.

METEOROLOGICAL INFORMATION

Weather, recorded at an airport 13 nautical miles to the southeast, at 1147, included clear skies, visibility 10 statute miles, and winds from 030 degrees true at 4 knots. The temperature was 27 degrees Centigrade (80 degrees Fahrenheit) and dew point was 7 degrees Centigrade (45 degrees Fahrenheit). Relative humidity was 28 per cent.

WRECKAGE INFORMATION

The main wreckage was located about 80 feet south of runway 27, approximately 200 feet beyond the threshold, in the vicinity of 35 degrees, 55.10 minutes north latitude, 81 degrees, 06.85 minutes west longitude.

An examination of the runway 27 approach area revealed that several small, less than 1-inch-diameter branches were separated from a tree about 150 feet to the east. The estimated height of tree damage was 60 to 70 feet above the runway.

Clear plastic landing light fairing fragments were found on the runway approximately 20 feet beyond the threshold. A ground scar, containing red plastic lens material, commenced about 15 feet south of the runway edge, about 130 feet beyond the threshold. The scar and wreckage path were aligned along a 265-degree magnetic heading.

An impact crater was located along the path, approximately 160 feet beyond the runway threshold, and about 10 feet beyond that, was the propeller hub, with the propeller blades still attached. Two of the three propeller blades had no leading edge damage. A third blade had leading edge damage, and fit exactly into a cut into the ground. A small section of that blade was also found in the cut.

The spinner had aft crush damage, with no rotational scoring or crushing. The bolt holes for joining the propeller hub to the engine attach studs displayed some radial elongation, with no rotational elongation or scoring.

The main wreckage was located about 40 feet beyond the propeller hub. The airplane was resting on its nose, at an approximately 60-degree nose-down angle, with its tailcone supported by a tree. The aft fuselage was angled about 30 degrees toward the left wing. The outboard half of the right wing was crushed aft, with uniformly increasing crush further outboard. The left wing also had leading edge crush, but it was not uniform along the wing.

All flight control surfaces were accounted for at the accident scene. Control cable continuity was confirmed from all flight control surfaces to the cabin area. The flaps were fully retracted, and the manual flap handle was stowed in a position corresponding to the flaps being fully retracted.

Fresh fuel stains were noted on the tops of the wings. The right fuel tank was not breached, and trace amounts of fuel were inside. There was some browning of vegetation below the right wing. The left fuel tank was breached, but still had 2 to 3 inches of fuel in the forward portion of the nose-low tank. The gascolator was destroyed and the fuel line was compromised. The carburetor bowl was less than 1/4 full.

In the cockpit, the mixture and propeller controls were found in the full forward position. The throttle was also in the full forward position, but bent to the left, and the "CARB HEAT PULL HOT" knob was all the way in.

Engine crankshaft and valve train continuity was confirmed, as was compression in all cylinders. Spark plug electrodes were dark gray in color. Both magnetos were tested, with spark achieved on seven of the eight leads. One lead was separated.

The carburetor was found partially separated from the engine, and displayed impact damage. The throttle lever and the throttle positions were consistent with "full open," and the mixture control lever was in the "full rich" position. The throttle and mixture levers moved freely from stop to stop by hand. The carburetor was disassembled, during which, the gasket was damaged when it stuck to the two mating surfaces. There was no debris within the carburetor, and the about 1/2 inch of blue liquid, consistent in appearance and odor with 100LL fuel, was found in the carburetor bowl.

The engine was subsequently forwarded to the manufacturer's facilities in Mobile, Alabama, for further testing, and on November 6, 2007, an engine test run was performed under FAA oversight. According to the Operational Test Report, the carburetor, which had previously been disassembled for examination at the accident site, was reassembled and reinstalled on the engine prior to the test. The engine was then moved to a test cell, and experienced a "normal" start on the first attempt. The engine was then advanced in rpm steps, and allowed to stabilize for 5 minutes at each step. Maximum rpm attained during full throttle was 2,400. Throughout the test, the engine exhibited "hesitation."

The original carburetor was subsequently replaced with a serviceable unit, and during the test run, attained 2,680 rpm, "without any hesitation, stumbling or interruption in power."

The report also noted that there was a "damaged and incomplete gasket installed" with the original carburetor, which would have precluded normal operation and rated horsepower.

MEDICAL AND TOXICOLOGICAL INFORMATION

Local authorities released the pilots' remains without performing autopsies, which precluded FAA comprehensive toxicological testing. Local authorities did provide single-source blood samples from each pilot to the North Carolina Medical Examiner's Office, which were only tested for, and were negative for, ethanol.

The Medical Examiner also determined that the probable cause of death for both pilots was "multiple trauma."

ADDITIONAL INFORMATION

According an article on the Cessna Flyer Association website titled "The Cessna 182":

"The 182 aircraft in general are prone to carburetor icing, so the carb heat must be fully operational and turned on in advance of the need to actually use it."

According to an article on the Cessna Pilots Association website titled "1956 through 1986 Cessna 182 Fixed Gear Skylane Buyers Guide Excerpt":

"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."

FAA Advisory Circular 20-113, "Pilot Precautions and Procedures to be Taken in Preventing Aircraft Reciprocating Engine Induction System and Fuel System Icing Problems" includes several carburetor icing considerations:

"Throttle Ice - Throttle ice is usually formed at or near a partially closed throttle, typical of an off-idle or cruise power setting. This occurs when water vapor in the air condenses and freezes because of the cooling restriction caused by the carburetor venturi and the throttle butterfly valve. The rate of ice accretion within and immediately downstream from the carburetor venturi and throttle butterfly valve is a function of the amount of entrained moisture in the air. If this icing condition is allowed to continue, the ice may build up until it effectively throttles the engine. Visible moisture in the air is not necessary for this type icing, sometimes making it difficult for the pilot to believe unless he is fully aware of this icing effect. The effect of throttle icing is a progressive decline in the power delivered by the engine. With a fixed pitch propeller this is evidenced by a loss in engine RPM and a loss of altitude or airspeed unless the throttle is slowly advanced. With a constant speed propeller, there will normally be no change in RPM but the same decrease in airplane performance will occur. A decrease in manifold pressure or exhaust gas temperature will occur before any noticeable decrease in engine and airplane performance. If these indications are not noted by the pilot and no corrective action is taken, the decline in engine power will probably continue progressively until it becomes necessary to retrim to maintain altitude; and engine roughness will occur probably followed by backfiring. Beyond this stage, insufficient power may be available to maintain flight; and complete stoppage may occur, especially if the throttle is moved abruptly.

Fuel Vaporization Ice - This icing condition usually occurs in conjunction with throttle icing. It is most prevalent with conventional float type carburetors, and to a lesser degree with pressure carburetors when the air/fuel mixture reaches a freezing temperature as a result of the cooling of the mixture during the expansion process that takes place between the carburetor and engine manifold. This does not present a problem on systems which inject fuel at a location beyond which the passages are kept warm by engine heat. Thus the injection of fuel directly into each cylinder, or air heated by a supercharger, generally precludes such icing. Vaporization icing may occur at temperatures from 32 degrees F. to as high as 100 degrees F. with a relative humidity of 50 percent or above. Relative humidity relates the actual water vapor present to that which could be present. Therefore, temperature largely determines the maximum amount of water vapor air can hold. Since aviation weather reports normally include air temperature and dewpoint temperature, it is possible to relate the temperature - dewpoint spread to relative humidity. As the spread becomes less, relative humidity increases and becomes 100% when temperature and dewpoint are the same. In general, when the temperature-dewpoint spread reaches 20° F. or less, you have a relative humidity of 50 percent or higher and are in potential icing conditions.

The pilot should remember that induction system icing is possible, particularly with float type carburetors, with temperatures as high as 100 degrees F and the humidity as low as 50 percent. It is more likely, however, with temperatures below 70 degrees F and the relative humidity above 80 percent. The likelihood of icing increases as the temperature decreases (down to 32 degrees F) and as the relative humidity increases."

Multiple examples of carburetor icing probability charts exist. When ambient temperatures were plotted on a chart found in FAA Advisory Circular FAA - P - 8740-24 "Tips on Winter Flying," the results indicated no probability of carburetor icing. However, when ambient temperatures were plotted on other available charts, many of which were based on a 1970 "Fuels and Lubricants of the National Research Council of Canada," study, the results did indicate a probability of carburetor icing at glide and cruise power. The charts also graphically indicated that under certain conditions, carburetor icing could occur in as low as 20 per cent relative humidity.

NTSB Probable Cause

Carburetor icing, which resulted in a loss of engine power. Also causal, was the pilots' failure to maintain airspeed during the forced landing, which resulted in an inadvertent stall.