On April 7, 2005, at 0903 Pacific daylight time, a Cessna T210L, N8126L, broke up in flight and impacted terrain near Tranquility, California. The airplane was operated by the private pilot under the provisions of 14 CFR Part 91. The pilot and two passengers were fatally injured; the airplane was destroyed. Instrument meteorological conditions prevailed, and a flight plan had not been filed. The flight originated at Healdsburg Municipal Airport, Healdsburg, California, about 0800, with an intended destination of Scottsdale, Arizona.

The pilot and two passengers were traveling to Scottsdale, on a weekend golf trip, where they were to meet up with other members of their party. The pilot received a weather briefing from Oakland Automated Flight Service at 0554. The airplane departed Healdsburg sometime before 0800. The initial radar track was picked up over the San Pablo Bay in the San Francisco area at 0801:30, at 11,600 feet mean sea level (msl). The track continued on a southeasterly course until over Crows Landing, California, where it made a deviation to the south. After the track passed over the San Luis Reservoir it turned left to regain its original southeasterly course. The track ended at 0902:21 in the vicinity of Tranquility. Radar data revealed that the altitude encoding transponder (mode C) reported a change of altitude of 1,000 feet from 12,400 to 13,400 feet msl between the times of 0848 and 0853. The final track segment depicted the airplane level at 13,400 feet msl and traveling in a southeasterly direction when it turned abruptly to the right. The last radar return was recorded at 0902:14, at a position of 36 degrees 37.22 minutes north latitude by 120 degrees 24.12 minutes west longitude, at an altitude of 12,400 feet msl. No record of radio communication between the pilot and air traffic control (ATC) was located by the Federal Aviation Administration (FAA) for the time period surrounding the accident.


A review of FAA airman records from Oklahoma City, Oklahoma, revealed that the pilot held a private pilot certificate with a single engine land rating that was issued on June 3, 1992. The pilot did not hold an instrument rating. The pilot held a third-class medical certificate that was issued on January 1, 2005. No restrictions or limitations were listed on the medical.

The pilot's flight logbook was recovered from the airplane wreckage. Examination of the logbook revealed that the pilot had accumulated 576.2 hours of single engine flight time. His last recorded flight occurred on March 16, 2005, and consisted of an insurance check ride in a PA-32. The entry made prior to that was dated November 18, 2004, where the pilot recorded a 2.8-hour flight in the accident airplane. The endorsement page of the logbook contained one entry, a flight review signed by a certified flight instructor (CFI) on September 14, 2003.


The airplane was a Cessna T210L, serial number 21060613, single engine, high wing, 6-place airplane. A review of the airplane's logbooks revealed a total airframe time of 3,415.2 hours at the last inspection. An inspection in accordance with the scope and detail of Appendix D of 14 CFR Part 43 (annual/100-hour inspection) was completed on September 24, 2004.

The airplane was powered by a Teledyne Continental TSIO-520-H4 factory remanufactured engine, serial number 217474-R. An examination of the engine logbook revealed that the engine had been installed into the airplane on August 8, 2003. The engine was inspected in accordance with an annual inspection on September 24, 2004, at a total time since maintenance overhaul (TSMO) of 33.6 hours.

The airplane had a factory installed Nav-O-Matic 400A autopilot, which provides altitude hold, heading hold, and VOR tracking. There were no autopilot discrepancies noted in the maintenance records.

The airframe and power plant (A&P) mechanic who performed the annual inspection stated that the airplane's crew oxygen system had not been inspected during the annual and was not in service.

A fuel receipt with the pilot's name on it was obtained from Healdsburg Aviation, Inc. The date and time on the receipt was April 7, 2007, at 06:56:51. The receipt recorded the total amount of fuel purchased was 58.094 gallons.

The airplane's pilot operating handbook states in the limitation section that flight into known icing conditions is prohibited.


1.7.1 Surface Analysis Chart

The southwest section of the National Weather Service (NWS) Surface Analysis Chart for 0800 depicted a high-pressure system with a central pressure of 1027-millibar (mb) over Colorado. To the north, a low-pressure system with a central pressure of 1001-millibars (mb) was located over the Oregon and Nevada border with a cold front extending from the low south to southwestward into Nevada, central and southern California, and into the Pacific Ocean. The accident site was located in the cold air mass behind the position of the surface cold front.

The station models behind the cold front, over central and southern California, indicated broken to overcast sky conditions.

1.7.2 Surface Observations

The area surrounding the accident site was documented utilizing official NWS meteorological aerodrome reports (METARs) and specials (SPECI). The reports are in standard format, provided in plain language. The variation for wind at Fresno is 15 degrees east, and cloud heights are reported above ground level (agl).

Madera Municipal Airport (KMAE), Madera, California

Madera weather observation at 0853, automated, wind from 300 degrees at 8 knots; visibility 10 miles in light rain; ceiling broken at 3,500 feet, broken at 4,100 feet, overcast at 9,500 feet; temperature 12 degrees Celsius (C); dew point 9 degrees C; altimeter 30.02 inHg. Remarks: automated observation system, rain began at 0849; sea level pressure 1016.3-mb; hourly precipitation less than 0.01-inch (trace); temperature 11.7 degrees C; dew point 8.9 degrees C; thunderstorm sensor not operating.

Lemoore Naval Air Station/Reeves Field (KNLC), Lemoore, California

Lemoore Naval Air Station (KNLC) special weather observation at 0845, wind from 330 degrees at 10 knots; visibility 7 miles in light rain; a few clouds at 6,000 feet; ceiling broken at 14,000 feet, overcast at 20,000 feet; temperature 13 degrees C; dew point 7 degrees C; altimeter 30.00 inHg. Remarks: sea level pressure 1016.0-mb.

Lemoore Naval Air Station (KNLC) weather observation at 0855, wind from 330 degrees at 13 knots; visibility 7 miles in light rain; ceiling broken at 5,000 feet, broken at 14,000 feet, overcast at 20,000 feet; temperature 12 degrees C; dew point 9 degrees C; altimeter 30.01 inHg. Remarks: sea level pressure 1016.2-mb; hourly precipitation less than 0.01-inch (trace); temperature 12.2 degrees C; dew point 8.9 degrees C.

Fresno Yosemite International Airport (KFAT), Fresno, California

Fresno weather observation at 0856, wind from 300 degrees true at 10 knots; wind 280 variable 350 degrees; visibility unrestricted at 10 statute miles; scattered clouds at 8,000 feet; ceiling broken at 14,000 feet, overcast at 18,000 feet; temperature 13 degrees C; dew point temperature 7 degrees C; altimeter 30.01 inHg. Remarks: automated observation system, sea level pressure 1015.9-mb; temperature 13.3 degrees C; dew point 7.2 degrees C.

Merced Municipal Airport/Macready Field (KMCE), Merced, California

Merced Municipal Airport special weather observation at 0830, automated, wind from 330 degrees at 8 knots; visibility 3 miles in light rain and mist; a few clouds at 600 feet; ceiling broken at 2,200 feet, overcast at 3,400 feet; temperature 11 degrees C; dew point 9 degrees C; altimeter 30.02 inHg. Remarks: automated observation system, hourly precipitation 0.06-inch; thunderstorm sensor not operating.

Merced Municipal Airport weather observation at 0853, automated, wind from 010 degrees at 6 knots; visibility 4 miles in light rain and mist; a few clouds at 2,400 feet; ceiling broken at 3,000 feet, overcast at 6,000 feet; temperature 11 degrees C; dew point 9 degrees C; altimeter 30.02 inHg. Remarks: automated observation system, sea level pressure 1016.4-mb; hourly precipitation 0.11 inches; temperature 10.6 degrees C; dew point 8.9 degrees C; thunderstorm sensor not operating.

1.7.3 Satellite Information

The GOES-10 (Geostationary Operational Environmental Satellite) infrared image at 0900 (6X magnification), with a standard MB temperature enhancement curve applied to the image to highlight the higher and colder cloud tops associated with deep convection, depicted an area of enhanced cloud cover associated high and cold cloud tops over California (including the accident site). The radiative cloud top temperature over the upset location was determined to be 228.20 degrees Kelvin (K), or -44.95 degrees C, which corresponded to cloud tops near 30,000 feet.

The GOES-10 visible image for 0900 (2X magnification) continued to depict an extensive area of cloud cover over California and the accident site. The cloud features over the upset location showed signs of vertical development consistent with nimbostratus type clouds.

1.7.4 Weather Radar Information

The closest Weather Surveillance Radar-1988, Doppler (WSR-88D) was located at the NWS San Joaquin Valley Office (KHNX) in Hanford, California, approximately 34 miles east of the accident site. The Level II archive data was obtained from the National Climatic Data Center (NCDC) and displayed on a Hewlett-Packard X-Station utilizing the National Transportation Safety Board McIDAS system.

Composite Reflectivity

The KHNX composite reflectivity image completed at 0904 (2X magnification) with the accident airplane's flight track that was obtained from the FAA National Track Analysis Program (NTAP). The image depicts the accident airplane's track across an area of very light intensity echoes in the range of 5 to 15 dBZ and approaching two general north-to-south oriented line of echoes. The upset location occurs on the western edge of the band of the first band.

Base Reflectivity

The KHNX WSR-88D images use 2.4- and 3.4- degree base reflectivity scans for 0859 at 4X magnification. The 2.4- degree elevation scan depicted the conditions under the accident airplane's flight track approaching the western edge of the band of echoes when the upset occurred. The conditions that encompassed the accident airplane's cruising altitude of 13,600 feet indicated that the aircraft was operating in echoes in the range of 5 to 15 dBZ for approximately 16 miles prior to the upset, or from approximately 0854. Echoes in the range of -10 to +10 dBZ, with temperatures below freezing, are typically associated with freezing drizzle, freezing rain, and large super cooled liquid water droplets (SLD) with reflectivities above 20 dBZ.

Radar Summary for Hanford (HNX), 30 nm to the southeast

A cell containing thunderstorms and intense rain showers was recorded at 0935. The cell was 3 nautical miles (nm) in diameter, centered at 175 degrees, 11 nm from HNX. An area of echoes, 5/10 coverage contained rain. The cell was 88 nm from 340 degrees to 164 degrees at 38 nm from HNX automated station.

1.7.5 In-Flight Weather Advisories

The NWS issues in-flight weather advisories designated as Severe Weather Forecast Alerts (AWW's), Convective SIGMET's (WST's), SIGMET's (WS's), Center Weather Advisories (CWA's), and AIRMET's (WA's). In-flight advisories serve to notify en route pilots of the possibility of encountering hazardous flying conditions, which may not have been forecast at the time of the preflight briefing. The NWS issued a series of AIRMETs at 0645, which were current until 1300. The advisories pertinent to the route of flight were as follows:

AIRMET Sierra update 2 was issued for mountain obscuration over portions of California and contained the area surrounding the accident location. The advisory warned of mountains occasionally obscured by clouds, fog, and mist.

AIRMET Tango update 3 was issued for turbulence over portions of Washington, Oregon, California, Nevada, Arizona, Utah, and contained the area surrounding the accident location. The advisory warned of occasional moderate turbulence below 15,000 feet due to strong and gusty southerly to southwesterly low-level winds. The conditions were expected to develop southward and eastward through 1300, spreading into Idaho and western Montana, and the remainder of Utah and Arizona through 1900. The accident site was located within the limits of this advisory.

AIRMET Zulu update 2 was current for portions of northern California, Oregon, Washington, Idaho, Montana, Nevada, coastal waters, and contained the area surrounding the accident location. The advisory warned of occasional moderate rime to mixed icing-in-clouds and in-precipitation between the freezing level and 20,000 feet. The freezing level was identified from 4,000 to 5,000 feet over the western portion of the area to 8,000 to 10,000 feet over the eastern portion. The conditions were expected to continue beyond 1300 through 1900, and spread southeastward. The accident site was located approximately 30 miles south of this advisory.

There were no other severe weather forecast alerts, SIGMETs, or Center Weather Advisories issued for California on April 7, 2005.

1.7.6 Pilot Reports (PIREPs)

The following pilot reports were recorded over central California within 120 miles of the accident site on April 7, 2005. The reports are in chronological order, and are narrative form instead of the standard code.

Modesto (MOD) routine pilot report (UA); Over - 15 miles southeast of Modesto (MOD); Time - 0707; Flight level - 9,000 feet; Type aircraft - Cessna Caravan single engine turboprop (C208); Temperature - minus 1 degree C; Icing - light rime icing.

Stockdale (SCK) routine pilot report (UA); Over - 40 miles east-northeast of Stockton VOR (ECA); Time - 0712; Flight level - 18,000 feet; Type aircraft - Boeing 737 commercial airliner (B737); Turbulence - moderate chop between 18,000 and 15,000 feet.

Stockdale (SCK) routine pilot report (UA); Over - 20 miles northeast of Stockton VOR (ECA); Time - 0741; Flight level - 11,500 feet; Type aircraft - Boeing 737 commercial airliner (B737); Turbulence - light to moderate turbulence during descent between 13,000 and 11,500 feet.

Modesto (MOD) routine pilot report (UA); Over - Modesto (MOD); Time - 0941; Flight level - 8,000 feet; Type aircraft - Piper Malibu single engine turboprop (PA46); Temperature - minus 2 degree C; Wind - from 260 degrees at 21 knots; turbulence - light chop; Icing - negative.

1.7.7 Preflight Weather Briefing

The pilot called the Oakland Automated Flight Service Station (AFSS) between 0544 and 0550, at which time he obtained a preflight weather briefing for the route of flight. The pilot indicated he intended to leave around 0700 local time from Santa Rosa traveling to Scottsdale, and was planning on operating at 13,000 feet. The AFSS briefer provided a synopsis of the current conditions indicating that a front extended along the coast of northern California with scattered precipitation ahead of it. He stated that there was a line of scattered precipitation from Salinas to Merced, California, especially over the central valley. The AFSS briefer indicated that advisories were current for occasional moderate turbulence below 15,000 feet, occasional moderate rime ice in any precipitation below flight level 200, the freezing level was about 6,000 feet, and that some higher terrain may be obscured by clouds. The briefer provided information for several locations along the proposed route of flight, which included a report in the immediate vicinity of the accident site for the Lemoore (KNLC), which indicated broken clouds between 3,000 to 5,000 feet, and overcast conditions between 5,000 and 6,000 feet. The weather over Scottsdale was clear. The AFSS briefer summarized the conditions and indicated that general VFR (visual flight rules) conditions would prevail for the route. The briefing ended with the pilot saying, "Sounds good. Looks like we might be able to make it. Last nights forecast didn't look promising." The briefer said, "Ya, doesn't seem too bad now." The pilot finished by saying, "Things have gotten a little better. Thank you for your help this morning."

The entire Safety Board Weather Study Factual Report is contained in the official docket of this investigation.


The main wreckage was located in a recently harvested and plowed hay field surrounded by flat featureless farm terrain. The Diablo Mountain range was visible 30 miles to the west. The wreckage coordinates were: 36 degrees 38.194 minutes north latitude by 120 degrees 24.016 minutes west longitude. The larger luggage items had been collected by the first responders and placed in a pile next to the main wreckage.

The fuselage laid collapsed longitudinally on its right side, leaving very little occupiable space in the cockpit. The fuel valve handle was observed in the right tank position and the magneto switch was in the both position. The engine was aligned with the airframe firewall and imbedded 3 feet into the earth on its right side. The three-bladed propeller was imbedded into the earth leaving only 1/2 of one of the blades exposed. The inboard 1/2 of the left wing laid across the exposed left side of the cabin and engine compartment area. The vertical stabilizer and rudder were present on the empennage, and the whole fuselage was oriented on a bearing of 095 degrees magnetic. The empennage area forward of the vertical stabilizer was severely distorted, twisted, and crumpled. The right horizontal stabilizer, excluding the elevator section, laid detached from the empennage resting on the left side of the wreckage. The right main landing gear strut was in its wheel well; the left main strut was rotated slightly out of its wheel well, and the nose wheel was retracted under the engine. The left wing spar was connected to a section of the carry-through spar. The carry-through spar was separated vertically 17 inches from the wing attach bolt locations, exposing a fracture surface that was bright metallic gray in color, matte texture, with 45-degree shear lips on the upper and lower sections of the I-beam. The other 2/3 of the carry-through spar was imbedded in the earth at an approximate angle of 30 degrees. Once extracted from the ground, the right side of the carry-through spar was intact with the right wing spar root area attached, exhibiting spar web material distorted aft.

The vertical stabilizer was attached to the empennage and the rudder was fastened securely to its hinge points but missing its balance weight. Numerous black scuffmarks were identified on both sides of the vertical stabilizer. Control cables were attached to the rudder bell crank and traced to the cockpit rudder pedals. Aileron control yolk chains and elevator control cables were observed attached to the cockpit control column.

The left wing leading edge was split in half spanwise, with the upper and lower sections of sheet metal wrapped aft along the upper and lower surface of the wing, respectively. The outboard 6 feet 3 inches of the wing was not present. The edge of the leading edge sheet metal exhibited saw like marks. Aileron control cables were exposed at the outer end of the sawed leading edge where a cable pulley and guide was located. The cables were still attached to the cabin area of the airframe. The outboard 1/3 of the wing was not present. The flap was present in the retracted position. The flap exhibited a 10-inch compressive buckle 24 inches outboard of the wing root area. The aileron bell crank Robertson STOL (Short Take Off and Landing) kit push-pull tube was loose in the wing. The push-pull tube exhibited a lock nut and fractured screw rod on the outboard end and an unscrewed threaded end on the inboard tube end. The flap bell crank contained an undistorted threaded eyebolt and lock nut with undistorted threads and oil-like residue on the threads. The tube exhibited circular spiral score marks on its surface at a location that corresponded with a wing rib. Examination of the wing spar revealed 45-degree buckling of the spar web at numerous locations from the lower inboard to the upper outboard.

The entire right wing was located about 863 yards southeast of the main wreckage on a bearing of 110 degrees magnetic. The coordinates of the wing were: 36 degrees 37.849 minutes north latitude by 120 degrees 23.714 minutes west longitude. The wing was detached at the wing root. The center section of the wing and 1/2 of the flap aft of the spar was folded up over the upper surface of the wing. The upper spar cap of the inboard section of wing was sheared from the spar webbing and had an upward deformation of approximately 20 degrees. Six and 1/2 feet inboard from the wing tip, the wing had a single buckled area along the chord line. The leading edge at this buckle location exhibited tearing and indentation. The aileron was not present. The wing exhibited two leading edge downward buckle locations at 1 foot and 3 feet outboard of the root. The aileron control cables were present in the wing and attached to the aileron bell crank. The cable ends that exited the wing root area were broomstrawed. Examination of the wing spar exhibited 45-degree buckling of the spar web at numerous locations from the lower inboard surface to the upper outboard surface.

The right horizontal stabilizer, excluding the elevator, was present at the main wreckage. The horizontal stabilizer had an overall curved downward set as viewed from a horizontal plane of reference. The leading edge exhibited some tucking and 1/4 circular indentation on the upper surface of the leading edge, about 2/3 down the span was identified. The outboard 1/3 of the stabilizer was pulled from the chordwise rivet line. A diagonal crush zone was observed in the left aft corner of the stabilizer. The elevator trim cables were present with the stabilizer and exhibited broomstrawed ends. The right elevator was located 1,619 yards southeast from the main wreckage. The right elevator balance weight was located 891 yards south of the main wreckage. The elevator was separated into four pieces. The main elevator surface was sheared down the middle in a chordwise direction. The balance weight was separated at the hinge and the trim tab had traveled off its piano wire hinge. The inboard section of elevator exhibited a crush zone similar to the crushed area of the horizontal stabilizer. The trim tab had split lengthwise exposing the foam core and displaying a white powdery surface on the interior aluminum structure. The entire piano wire for the hinge of the trim tab was present on the inboard section of the elevator.

The left horizontal stabilizer was found 1,506 yards southeast of the main wreckage. The stabilizer surface exhibited a distinct downward set as referenced to the horizontal plane. The leading edge exhibited some downward tucking and the 30-degree diagonal fold in the inboard aft corner was observed. The elevator control surface was found 1.2 miles southeast and the elevator balance weight was found 541 yards south of the main wreckage. The elevator, excluding the balance weight tip, was separated in half approximately at the middle hinge.

Both left and right ailerons were separated in half along the chord line. The ailerons were constructed with a weighted outboard leading edge section and an inboard unweighted section embodied in the same single control surface. The right and left unweighted sections of the aileron were found 1.25 and 1.37 miles, respectively, southeast of the main wreckage and the weighted right aileron section was found 1,175 yards away in the same direction.

Baggage recovered from the main wreckage area and the debris field contained 3 sets of golf clubs, 3 pieces of travel luggage, 3 briefcase-type of luggage, 13 wine corks wrapped in foil caps, and miscellaneous other personal affects. The combined weight of these items totaled 173.75 pounds. The weight of the wine cargo was estimated by multiplying 13 by 2.6 pounds (weight of an average full bottle of wine), which resulted in an additional 33 pounds.


The Fresno County Coroner completed the autopsy of the pilot. The FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, performed toxicological analysis from samples obtained during the autopsy. The report contained the following positive results: tetrahydrocannabinol carboxylic acid detected in urine (>0.5432 ug/ml), tetrahydrocannabinol carboxylic acid detected in kidney tissue (>0.3921 ug/ml), tetrahydrocannabinol detected in kidney tissue (>0.0225 ug/ml), sildenafil present in urine, sildenafil present in kidney tissue, desmethylsildenafil present in urine, desmethylsidenafil present in kidney tissue, naproxen present in urine, and naproxen present in liver tissue.


The wreckage was collected and transported to a recovery yard operated by Plain Parts, Pleasant Grove, California. On April 11 and 12, 2005, the wreckage was examined by technical experts from Cessna Aircraft and Teledyne Continental Motors under the supervision of the Safety Board Investigator-in-Charge.

1.16.1 Engine Examination

The engine was a Teledyne Continental TSIO-520-H, serial number 217474-R. Rocker covers 1, 2, 3, and 5 were breached. The top spark plugs were removed and observed to have a light to dark gray color and no mechanical damage, which corresponds to normal wear according to the Champion Aviation Check-A-Plug chart (AV-27). The crankshaft could not be rotated but all six pistons were observed in symmetrical positions. Both the magnetos were broken off their mounting pads to the right. The left magneto produced spark on one post and the right magneto produced spark on five posts when rotated by hand. The propeller governor was set towards the high rpm stop. The throttle, mixture, and propeller governor cables were traced to the cockpit control quadrant.

The propeller was a McCauley D3AF32C88-MR, three bladed with controllable pitch. The propeller blades were loose in the hub. Investigators numbered the blades 1, 2, 3, for ease of identification. The number 1 blade was bent aft 10 degrees at the root; the number 2 blade was bent forward 45 degrees at midspan; and the number 3 blade was bent aft 80 degrees at the root. All blades exhibited light leading edge polishing with no leading edge gouges or ding marks. The metal spinner was split and folded to one side of the propeller dome, taking on the form of the hub. The spinner had minor circumferal folds in the counterclockwise direction when viewed head on.

1.16.2 Vacuum and Gyroscope (gyro) Systems

The engine driven vacuum pump was removed from the engine mounting pad and disassembled. The vacuum pump drive coupling was in tact and the rotor was fractured into five separate wedges. No surface scoring was observed on the interior of the vacuum pump housing.

The turn and bank gyro, directional gyro, and attitude gyro were removed from their instrument casings and disassembled. Circumferal scoring was observed on all the gyro rotors and circumferal scoring was identified on the interior surface of all the gyro housings.

1.16.3 Wing Carry Through Spar

The Safety Board Materials Laboratory examined the wing carry-through spar. No material or structural defects were identified and the fractures were overload separations. The entire Material Laboratory Factual Report can be located in the official docket of this investigation.

1.16.4 Weight and Balance

A weight and balance calculation was performed using the weight and balance data that the airplane mechanic had retained in his records, the measured weights of the baggage recovered from the accident site, the weights and locations of the victims as reported by the Fresno County Coroner, and a full 88-gallon fuel load. The estimated gross weight of the airplane at takeoff was 3,813.9 pounds, which is 13.9 pounds outside the allowable maximum gross weight as specified by Cessna. At takeoff the estimated moment was 162.9 pound-inches, which puts it with in the center of gravity position limits. The weight and balance calculation indicates that as fuel was burned and the gross weight of the airplane got below 3,800 pounds, the airplane's center of gravity would remain in acceptable limits throughout the entire flight.


1.18.1 Radar Data

Radar data was obtained from the Fresno ASR-11, Paso Robles ARSR-4, Mill Valley ARSR-4, and Vandenberg ARSR-4 radar facilities. Radar data contained a target track identified with a 1200 code on a southeasterly aircraft track at 0902, that coincided with the general location of the aircraft wreckage. The track made a steady course to the southeast at a recorded altitude of 13,500 feet. The last radar return that is in line with the southeasterly course occurred at 0901:54, 13,400 feet msl. The next three radar returns occurred between 0901:59 and 0902:14, and depicted the track in a right- hand turn and a descent to 12,400 feet msl, which is the last identified altitude. This change in altitude corresponds to a 3,000- to 4,000-feet-per-minute rate of descent. Numerous primary targets were identified in the same vicinity from 0902:14 to 0903:08. No altitudes were recorded for these primary targets. Primary radar data is data that the radar receives as reflected energy from an object but no identifying transponder information is associated with the target.

1.18.2 Flight into Instrument Meteorological Conditions (IMC)

The Airplane Flying Handbook (FAA-H-8083-3A) states the following:

"A VFR pilot is in IMC conditions anytime he or she is unable to maintain airplane attitude control by reference to the natural horizon, regardless of the circumstances or the prevailing weather conditions. Additionally, the VFR pilot is, in effect, in IMC anytime he or she is inadvertently, or intentionally for an indeterminate period of time, unable to navigate or establish geographical position by visual reference to landmarks on the surface. These situations must be accepted by the pilot involved as a genuine emergency, requiring appropriate action.

The pilot must understand that unless he or she is trained, qualified, and current in the control of an airplane solely by reference to flight instruments, he or she will be unable to do so for any length of time. Many hours of VFR flying using the attitude indicator as a reference for airplane control may lull a pilot into a false sense of security based on an overestimation of his or her personal ability to control the airplane solely by instrument reference. In VFR conditions, even though the pilot thinks he or she is controlling the airplane by instrument reference, the pilot also receives an overview of the natural horizon and may subconsciously rely on it more than the cockpit attitude indicator. If the natural horizon were to suddenly disappear, the untrained instrument pilot would be subject to vertigo, spatial disorientation, and inevitable control loss."

1.18.3 Icing

The Airplane Flying Handbook (FAA-H-8083.3A) states the following about ice accumulation on an airplane.

"Degradation of all flight characteristics and large performance losses can be expected with ice accumulations. Pilots should not rely upon the stall warning devices for adequate stall warning with ice accumulations.

Ice will accumulate unevenly on the airplane. It will add weight and drag (primarily drag), and decrease thrust and lift. Even wing shape affects ice accumulation; thin airfoil sections are more prone to ice accumulation than thick, highly-cambered sections. For this reason certain surfaces, such as the horizontal stabilizer, are more prone to icing than the wing. With ice accumulations, landing approaches should be made with a minimum wing flap setting (flap extension increases the angle of attack of the horizontal stabilizer) and with an added margin of airspeed. Sudden and large configuration and airspeed changes should be avoided.

Unless otherwise recommended in the AFM/POH, the autopilot should not be used in icing conditions. Continuous use of the autopilot will mask trim and handling changes that will occur with ice accumulation. Without this control feedback, the pilot may not be aware of ice accumulation building to hazardous levels. The autopilot will suddenly disconnect when it reaches design limits and the pilot may find the airplane has assumed unsatisfactory handling characteristics."

1.18.4 Use of Supplemental Oxygen

Federal Aviation Regulation (FAR) 91.211 requires the flight crew use supplemental oxygen when the airplane is flying for greater than 30 minutes at cabin pressures between 12,500 and 14,000 feet msl. The radar track reveals that the airplane climbed above 12,500 feet during the last portion of the flight and was above 12,500 feet for approximately 5 minutes.

1.18.5 Wreckage Release

The wreckage was released on July 7, 2005.

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