NTSB Factual Report

HISTORY OF FLIGHT

On April 13, 1995, approximately 1700 Pacific daylight time (PDT), a Cessna 182, N182AL, impacted the terrain about five miles northwest of Index, Washington. The commercial pilot, who was the sole occupant of the aircraft, received fatal injuries, and the aircraft was destroyed. The personal pleasure flight, which departed Lake Chelan Municipal Airport, Chelan, Washington, about 40 minutes earlier, was in instrument meteorological conditions at the time of the accident. The pilot was on an IFR flight plan, and the ELT, which was activated by the impact, was later turned off at the scene.

On the day of the accident, approximately 1110 PDT, the pilot of N182AL called the Seattle FAA Flight Service Station and received a standard briefing for an IFR flight from Paine Field to Wenatchee, and return. He said that his intent was to depart Paine Field about 1215, fly IFR to Wenatchee, and then continue on VFR to Lake Chalen Municipal Airport. For the return portion of the flight, he filed IFR out of Wenatchee, with a departure time of 1600. His filed altitude to Wenatchee was 13,000 feet, and for the return he filed for 12,000 feet. Estimate time en route (ETE) to Wenatchee was 45 minutes, with a 55 minute ETE filed for the return.

As part of the weather briefing, the pilot was advised that the forecast for his route included occasional moderate rime or mixed ice in clouds and precipitation between 4,000 and 12,000 feet. He was told that the freezing level on the west side of the Cascade Mountains was forecast for 3,000 feet, and would vary between 6,000 and 8,000 feet on the east side of the mountains. The briefing included the fact that a moist unstable air mass, with cloud tops to 20,000 feet, would be approaching western Washington in the late afternoon. The briefer also stated that the forecast for western Washington, after 1400, included isolated thunderstorms, moderate rain showers, and cumulonimbus tops to 30,000 feet. In addition, the pilot was told that the forecast indicated that the isolated thunderstorms, moderate rain showers, and cumulonimbus to 30,000 feet would be present in the western half of eastern Washington as well. Near the end of the briefing, the pilot was advised that the terminal weather in the Paine Field area was forecast to deteriorate throughout the afternoon.

On the return flight, the pilot contacted Seattle Approach about 1617, reported that he was six and one-half miles west of Wenatchee, and requested to pick up his IFR clearance back to Paine Field. About one minute later he was cleared to climb to 14,000 feet, and cleared direct to Paine Field. About ten minutes later, the pilot requested to clearance deviate 35 degrees south of course in order to avoid a build-up. About 11 minutes later, Seattle Center amended the clearance for N182AL, clearing the pilot to climb to 12,000 feet. He was then advised that 12,000 feet would be his final en route altitude because of other traffic. About one minute later, the pilot of N182AL advised the center that he had altered his course back to "direct Paine". About 12 minutes after his altitude clearance was amended, the pilot reported he was level at 12,000 feet, and four minutes after that call, he asked if there was any chance to climb to 14,000 feet. Center immediately cleared him to 13,000 feet, and advised the pilot that, if he wanted to go about 5 miles south or north of course, he could be cleared to a higher altitude. The pilot responded that he was picking up a trace of rime ice, which he would like to get out of, but would try it at 13,000 feet. Approximately five minutes later, the pilot asked how it looked to get to 14,000 feet, and was advised that he could expect higher in about 30 seconds. Twenty seconds later he was cleared to 14,000 feet, and about two minutes later Seattle Center asked him if he was in the clear yet. He responded that he was not. Then for about 10 minutes, there were no further radio communications between the center and the pilot of N182AL.

Then about 1654, the pilot advised center that he was having a problem. He said that he was picking up carburetor ice, and did not seem able to get rid of it. He also advised center that he could not maintain his altitude. Center immediately cleared the pilot to 10,000 feet. Then about two minutes later, the pilot transmitted that he had an emergency, had virtually no power left, and could not maintain his assigned altitude of 10,000 feet. The controller advised the pilot he was in 10,000 foot terrain, and checked to see if the pilot had tried his carburetor heat. The pilot reported that he was trying the carburetor heat, but that it did not seem to be working right. He also said that his engine was cutting in and out and producing very little power, and that when he kept the carburetor heat on, the little power he did have would go away.

The pilot advised Seattle Center that he was still in instrument meteorological conditions, and could not maintain altitude without stalling the aircraft. As the aircraft continued to descend, the controller attempted to give the pilot terrain height/location information, and asked the pilot if he wanted to try to make it to Skykomish Airport, which was about six miles left of the aircraft's course. The pilot responded that he would keep going west-bound. About 1700 PDT the controller gave the pilot his approximate position in relation to the town of Gold Bar, advised him of the location of Sky Harbor Airport, and asked him if he could see the ground yet. The pilot responded that he could not see the ground yet, as he was still "...solid IMC." Fifty seconds later, the controller attempted to contact the pilot, but there was no response. About two minutes after the last attempted contact, an ELT transmission was reported by another aircraft in the area.

WRECKAGE AND IMPACT INFORMATION

The aircraft impacted steep snow-covered terrain about 100 feet below the top of a rocky ridge. The impact site, which was located on a slope of more than 70 degrees, was about one mile southeast of Prospect Peak. The impact altitude was approximately 4,900 feet above sea level (MSL). The left wing of the aircraft was located about 50 feet up a tree estimated to be 100 feet tall. The remainder of the aircraft, which impacted large snow- covered boulders about 50 feet beyond the tree and slid back down the slope, was sitting at the base of the tree in which the wing was located. The heading from the tree to the boulders was approximately 235 degrees. The wing in the tree, and the remainder of the aircraft at its base constituted the entire wreckage.

The left wing, which was intact except for the outboard half of the aileron, had one massive circular indentation centered about two feet outboard of the wing root. This indentation, which extended aft of the front spar, was approximately 18 inches in diameter. Both the lower and upper wing skins in the area of the indentation were pushed aft and up at about a 40 degree angle. Except for numerous small ripples of the skin, and another small leading edge indentation just outboard of the fuel tank, the rest of the wing retained its general form.

The right wing, which was still attached to the fuselage by the spar attach points and the lift strut, showed only minor damage, except at its tip. The engine had been pushed back into the firewall, and the forward portion of the fuselage, back to and including the instrument panel, showed extensive crushing, tearing and bending. The carburetor remained attached to the intake manifold, but the induction air box had been torn from the bottom of the carburetor. The carburetor heat control cable remained attached to the selector activation lever on the induction air box. The aft cabin area, fuselage and empennage retained their general form, and except for a tear in the fuselage just aft of the baggage compartment, showed only minor damage.

The propeller hub was still connected to the crankshaft, and one blade still remained in the hub. Both blades showed some degree of longitudinal twisting, and the blade that separated from the hub showed S-curving. Neither blade showed any leading-edge indentations.

After the aircraft was recovered, the investigator-in-charge (IIC) subjected the engine to a full teardown inspection. Technical assistance was provided during this teardown by representatives of Cessna Aircraft Company and Teledyne Continental Motors. During the teardown, all six cylinders were removed, and the crankcase halves were separated so that an inspection of all internal components could be completed. Although the impact had pushed the crankshaft back into the crankcase, and caused heavy damage to the number six cylinder, there was no indication of pre-impact mechanical failure or malfunction. There were no unusual particulates in the oil, and the spark plugs exhibited normal erosion and gapping. One magneto produced a spark when turned by hand, but the other did not. This same magneto did not spark when run up to normal operating rpm, so it was subjected to an FAA supervised teardown inspection at Slick Aircraft Products, the manufacturer of the magneto. The teardown inspection determined that the inability of the magneto to produce a spark was probably the result of the corrosion that accumulated in the magneto points during the five months that the wreckage remained at the accident site. In addition, the IIC supervised a teardown inspection and flow check of the carburetor at Precision Airmotive Corporation. That inspection revealed no mechanical problems or out-of-limit flow rates.

ADDITIONAL DATA AND INFORMATION

Because of the deep unstable snow on the extremely steep terrain, the aircraft was not removed from the accident site until June 22, 1995.

A toxicological analysis was completed by the FAA Toxicology and Accident Research Laboratory, and the results were negative for carboxyhemoglobin and cyanide in the blood, and ethanol and screened drugs in the urine.

An autopsy was performed by Dr. Daniel Selove, an associate Snohomish County medical examiner, and the cause of death was attributed to traumatic injuries sustained during the impact.

The aircraft was released to Barrus & Stiger, Inc., on July 18, 1995, and the two retained magnetos and the carburetor were released to the same entity on December 20, 1995.

NTSB Probable Cause

the pilot's continued flight into known adverse weather, and his improper use of carburetor heat. Factors include: weather conditions conducive to carburetor icing and airframe icing, airframe ice, and mountainous/hilly terrain in the area of the forced descent.