N10BX – Beechcraft (Textron Aviation) S35 – 2003-11-25 NTSB Accident Report

HISTORY OF FLIGHT

On November 25, 2003, approximately 0653 Pacific standard time, a Beech S35, N10BX, was destroyed after impacting terrain following an in-flight breakup and uncontrolled descent from cruise flight near Warren, Oregon. The instrument rated commercial pilot and his three passengers received fatal injuries. Visual meteorological conditions prevailed at the accident site, but instrument meteorological conditions were reported over the pilot's route of flight. An instrument flight rules (IFR) flight plan had been filed for the personal cross-country flight being conducted under 14 CFR Part 91. The flight originated from the Arlington Municipal Airport (AWO), Arlington, Washington, at approximately 0535, and was en route to Medford (MFR), Oregon.

Approximately two hours prior to the flight the pilot had received a standard weather briefing from the Seattle Automated Flight Service Station (AFSS). At 0524, (all times are referenced to Pacific standard time) the pilot contacted the AFSS stating that he was on the ground at AWO, had filed an IFR flight plan to MFR, and that he was about ten minutes late. The specialist told the pilot to hold while he proceeded to coordinate the clearance with the Seattle Air Route Traffic Control Center (ARTCC). At 0527 the specialist cleared N10BX to the WATON NDB (non directional beacon), climb and maintain four thousand. The pilot read back the clearance, which the specialist confirmed was correct, and the conversation ended at 0528.

At 0540, radar contact was established with N10BX at an altitude of 1,400 feet mean sea level (msl), and at 0543 radar indicated the airplane was at 3,700 feet msl. At 0635, while at 11,000 feet msl, N10BX requested a higher altitude; ARTCC cleared the pilot to 13,000 feet msl. Radar data indicated that at 0639 N10BX was at 13,000 feet msl, and at an unknown time the pilot reported that he was at 13,000 feet and "clear of rime ice." The pilot subsequently radioed to ARTCC, at an undetermined time, "ah, we just lost our suction gage," the controller responding "...climb and maintain 15 thousand? You requesting a higher altitude? Is that what you said?" The pilot then replied, "Mayday, Mayday, Mayday." There were no further transmissions from N10BX.

Radar data revealed that at 0650:52 N10BX was at 13,100 feet msl beginning a right turn from a southerly heading to a south-southwesterly heading, and seven seconds later at 0650:59 was at 12,900 feet msl beginning a right turn to a southeasterly heading. At 0651:04 N10BX was at 12,800 feet msl starting a right turn from the southeast to south-southeast, and at 0651:11 the flight was still at 12,800 feet msl, but then made a left turn back to a heading of southeast. At 0651:16 the aircraft had ascended to 12,900 feet msl and was making a turn further left to a east-southeasterly heading, reaching 13,100 feet msl at 0651:28. Radar data indicates that at 0651:28 the airplane's heading changed from east-southeast to a heading of northeast, having descended to an altitude of 10,700 feet msl by 0651:52. The airplane then turned back to a heading of east-southeast and descended to an altitude of 10,500 feet msl at 0651:59. N10BX continued on a heading of east until 0652:05, when its altitude was recorded at 6,800 feet msl. It then proceeded on a northwesterly heading until 0652:17, when the last radar hit recorded the aircraft at an altitude of 6,400 feet msl.

The fuselage and engine were located on the east side of Scappoose Bay, approximately 3 nautical miles north-northeast of the Scappoose Industrial Airpark, Scappoose, Oregon, and approximately 1 nautical mile northeast of Warren, Oregon, having impacted a low-lying marsh area. The fuselage came to rest in an inverted position oriented on a magnetic heading of 350 degrees. There was no evidence of fire. Both wings, the tail section, and the left stabilizer of the airplane were located approximately 1 nautical mile northeast of where the fuselage and engine came to rest.

The recovery of the wreckage was delayed due to the varying tides inherent to the region, with high tide estimated at 1 1/2 feet of water at the accident site. Recovery efforts commenced on November 26, 2003, and concluded on December 3, 2004. The wreckage was transported to a secured storage facility in Independence, Oregon, to await further examination by representatives of the National Transportation Safety Board and the Federal Aviation Administration.

PERSONNEL INFORMATION

A review of Federal Aviation Administration (FAA) records revealed that the pilot was an instrument-rated commercial pilot in airplane single and multiengine land aircraft. FAA records also revealed the pilot held an aircraft airframe and powerplant certificate. The pilot possessed a second class medical certificate, dated March 19, 2002, without limitations. On the application for the medical certificate, the pilot reported his total pilot time as 2,867 hours, with 4 hours flight time in the last 6 months.

According to the pilot's flight log, the last entry was on August 30, 2003. A .5 hour local flight with one instrument approach was entered, but no actual or simulated instrument flight time was logged. The pilot's last recorded flight that included actual instrument flight time was on August 23, 2003, which was a 3.6 hour cross-country flight that included a segment of 1.2 hours of actual instrument flight time. At this time the pilot's total flight time was recorded to be 2,235.4 hours in single-engine aircraft, and 1028.1 hour in multiengine airplanes. The pilot's most recent biennial flight review was conducted on December 31, 2002.

AIRCRAFT INFORMATION

N10BX, (S/N D-7876), a model S35, was manufactured by the Beech Aircraft Corporation in 1965. The airplane was equipped with a Teledyne Continental IO-520 fuel injected engine rated at 285 horsepower, and a McCauley 2-blade, all metal, constant-speed propeller.

According to aircraft maintenance records, the pilot, a certificated airframe and powerplant mechanic, conducted the most recent annual inspection, which was performed on June 12, 2003, at a tachometer time of 3,365 hours and a total airframe time of 7,552.5 hours. The most recent inspection of the aircraft's transponder, altimeter, pressure altitude reporting system, and alternate static system was checked satisfactorily on October 30, 2002. A serviceable vacuum pump, (S/N 22C-219) was installed on November 21, 2001.

METEOROLOGICAL INFORMATION

At 0347 the pilot contacted the AFSS stating that he would be departing at 0500 from the AWO, IFR to MFR at 10,000 feet. The pilot then gave the briefer his call sign and requested a standard weather briefing. The briefing specialist advised the pilot of an advisory for mountains to be obscured, an Airmet for occasional moderate turbulence below 15,000 feet, icing, occasional moderate rime or mixed in clouds and precipitation, with a freezing level to 16,000 feet. The specialist advised the pilot of a frontal system off shore pushing clouds and precipitation into most of the pacific northwest, and that radar indicated precipitation "...all the way down to about Salem. The specialist then informed the pilot that the weather at MFR was wind calm, visibility 3 statute miles, "bouncing around" between 3/4 and 3 statute miles, with the RVR (runway visual range) for runway 14 4,500 feet, variable to 6,000 feet with mist. The ceiling was 7,000 overcast with the temperature and dew point both minus 1 degree. The specialist went on to say that along the route of flight there was widespread rain down to Salem with multiple layers of clouds. The briefer continued by advising the pilot that the area forecast for western Washington was broken clouds at 2,000 feet, overcast clouds at 4,000 feet, with tops at 20,000 feet and visibilities 3 to 5 miles in rain or mist, and snow or mist above 2,000, and southerly gust up to 25 knots. The briefer said the western Oregon forecast was not much different. The pilot then queried the specialist about the freezing level around the Seattle/Arlington area of between a 1,000 and 2,500 feet, with the briefer responding 2,500 to 3,500 feet. The briefer advised the pilot that the forecast for MFR was wind calm, visibility 1 statute mile in mist, with scattered clouds at 200 feet, overcast clouds at 6,000 feet, with an occasional visibility of 1/2 mile and freezing fog. The pilot then said he would be getting in there [MFR] at about 0730. The specialist responded that the forecast was good until 0800, and after that not much different. The briefing was concluded at 0355.

At 0553, the Automated Surface Observing System (ASOS) at the Scappoose Industrial Airpark (SPB), Scappoose, Oregon, located 3 nautical miles southwest of the accident site, reported wind 180 degrees at 4 knots, visibility 10 statute miles, light rain showers, overcast clouds at 1,300 feet, temperature 5 degrees C, dew point minus 2 degrees C, and an altimeter setting of 29.69 inches of Mercury.

At 0653, the SPB ASOS reported wind 130 degrees at 5 knots, visibility 6 statute miles, moderate rain showers, scattered clouds at 1,600 feet, broken clouds at 3,200 feet, overcast clouds at 5,000 feet, temperature 4 degrees C, dew point minus 2 degrees C, and an altimeter setting of 29.68 inches of Mercury.

At 0553, the ASOS at the Pearson-Field Airport (VUO), Vancouver, Washington, located 17 nautical miles southeast of the accident site, reported wind 190 degrees at 11 knots, gust to 20 knots, visibility 10 statute miles, light rain showers, broken clouds at 1,800 feet, broken clouds at 2,900 feet, temperature 6 degrees C, dew point 3 degrees C, and an altimeter setting of 29.70 inches of Mercury.

At 0653, the VUO ASOS reported wind 220 degrees at 9 knots, visibility 10 statute miles, light rain showers, broken clouds at 1,600 feet, overcast clouds at 2,100 feet, temperature 6 degrees C, dew point 3 degrees C, and an altimeter setting of 29.69 inches of Mercury.

WRECKAGE AND IMPACT INFORMATION

The primary wreckage site, consisting of the main cabin area, cockpit, and engine, was located in a wet, low-lying marsh area approximately 2 nautical miles west of the Columbia River. The accident site coordinates were obtained with a hand held global positioning system (GPS) unit. The coordinates were 45 degrees 49.131 minutes north latitude, 112 degrees 50.336 minutes west longitude. According to GPS data, the elevation at the accident site was 14 feet above sea level. Four components of the aircraft were located at the following locations relative to the main wreckage site: the tail section and tailcone was located 3,830 feet from the main wreckage area on a magnetic heading of 041 degrees; the right wing was located 4,483 feet from the main wreckage area on a magnetic heading of 045 degrees; the left wing was located 4,166 feet from the main wreckage on a magnetic heading of 036 degrees; the left stabilizer was located 4,574 feet from the main wreckage on a magnetic heading of 038 degrees. (See Attachment #1, distribution area map.)

The left stabilizer was separated from the fuselage. The ruddervator was found fractured into four pieces, three of which remained attached to the stabilizer by the ruddervator trim cable and the outboard ruddervator hinge. The ruddervator counterweight was not located. Approximately five inches of the FS 256.9 bulkhead remained attached to the front spar. The separated piece of bulkhead was torn below the lower attach bolts, flush with the inboard end of the spar, and extended upward above the upper spar cap. All fasteners were intact in the fastener holes. The front spar was found with the upper cap twisted forward and the lower cap bent in an aft direction. These signatures are consistent with the wing separating in an upward or positive direction. (See Attachment #2, Raython report) The stabilizer exhibited a 45-degree buckle in the upper skin panel from the front spar outboard to the trailing edge. The rear spar separated at the bottom of the outboard attachment bolt holes. The upper and lower spar caps exhibited bending in an upward direction where the spar separated. The ruddervator trim tab cable was captured in a tear in one of the lightening holes at the root of the stabilizer. The left cuff remained attached to the fuselage. The upper flange on the cuff was bent in an upward direction. These signatures are consistent with the stabilizer separating in an upward and aft direction.

The right stabilizer remained attached to the fuselage and tail cone. The differential mechanism assembly was found fractured in several pieces but remained attached to the empennage. The ruddervator counterweight was not located. The leading edge of the stabilizer was found bent in an upward direction at an angle of approximately 45-degrees from the chord line. The bend originated at the front spar and terminated at the middle ruddervator hinge. The ruddervator was found torn into three pieces. The ruddervator and trim tab remained attached to the stabilizer. There was a dent in the leading edge of the stabilizer near the tip. The stabilizer exhibited compression wrinkling on the upper and lower skin panels. The trim tab cable was captured in a tear in the upper aft corner of a lightening hole on the inboard rib of the stabilizer. There was a tear in the fuselage skin in the same area.

The right wing exhibited several wrinkles in the upper skin panels and remained attached to approximately 36 inches of main spar carry-through structure. The separated end of the main spar carry-through upper cap exhibited compression bending in an upward direction. The lower cap exhibited tension overload signatures. These signatures are consistent with the wing separating in an upward or positive direction. (See Attachment #2, Raytheon report) The upper and lower main spar wing bolts remained attached to the wing. The aileron and flap remained attached to the wing and in good condition. The flap actuator remained attached to the wing, but had separated from the flap. The exposed portion of the flap actuator shaft measured 1.25 inches, which equates to 0 degrees of flap extension. The landing gear actuator gear box remained attached to the carry-through structure. The right main landing gear remained attached to the wing and was undamaged. Examination of the landing gear actuator gear box indicated that the right main landing gear was in the retracted position. The fuel cap remained attached to the fuel tank. When the fuel cap was removed, the smell of fuel was present. The fuel system was breached at the supply lines between the fuselage and wing. The aft spar separated 7 inches outboard of the wing bolts and this section remained attached to the fuselage. Both ends of the aileron bellcrank separated from the bellcrank, and the bellcrank remained attached to the wing. The aileron pushrod separated at the bellcrank. Flight control cable marks were observed on the upper surface of the lightening hole in the inboard rib.

The left wing and approximately seven inches of carry-through structure separated from the fuselage. The wing attach bolts remained intact and attached to the wing. The upper carry-through cap exhibited compression bending. The lower cap exhibited tension overload signatures. These signatures are consistent with separation in an upward or positive direction. (See Attachment #2, Raytheon report) The left main landing gear remained attached to the wing and was found in the retracted position. The aileron remained attached to the wing and was found in good condition. Both ends of the aileron bellcrank were found separated. The aileron pushrod was found separated at the bellcrank. The flap was not attached to the wing and could not be located. The leading edge of the wing near the fuselage was found crushed aft. The aft spar separated approximately 11 inches outboard of the wing root. The pitot tube remained attached to the wing and was found packed with dirt. The fuel cap was removed and the smell of fuel was present.

MEDICAL AND PATHOLOGICAL INFORMATION

On November 26, 2004, an autopsy was performed on the pilot by the Oregon State Medical Examiner’s Office, Portland, Oregon. The pilot's cause of death was reported "multiple blunt force traumatic injuries".

The FAA's Civil Aeromedical Institute (CAMI) in Oklahoma City, Oklahoma, performed toxicology tests on the pilot. According to CAMI's report (#200300345001), the tests yielded negative findings for carbon monoxide, cyanide, ethanol, and drugs.

TESTS AND RESEARCH

On January 6, 2004, an examination of the aircraft's engine was conducted under the supervision of the NTSB investigator-in-charge (IIC). The valve covers were removed and the valve train was visually inspected. All valves, springs, retainers, rocker arms, shafts, and pushrods were intact. The piston domes were inspected through the spark plug holes and all appeared intact. All six cylinders had chrome bores and were filled with mud and water. Both magnetos had been broken off and destroyed. The alternator and fuel pump were removed. The crankshaft could only be rotated through an arc of approximately 5 degrees. When the crankshaft was rotated, mechanical continuity was observed throughout the engine to the accessory section. The metering unit fuel inlet screen was removed and found to be filled with mud and water. The oil filter was removed, cut open and inspected. It contained clean oil and no contaminants were noted on the filter media. The bottom spark plugs were removed and visually examined. The RHB-32E spark plugs exhibited rusty electrodes that had moderate electrode erosion and nominal gapping.

An examination of the vacuum pump regulator revealed that the internal spring was intact and held the diaphragm firmly against the regulator body. The regulator filter sock was functional. Teflon tape was observed on one threaded fitting and was installed properly. While the regulator body and cap were damaged, no pre-accident abnormalities were found which would have prevented normal operations of the vacuum pump regulator.

VACUUM PUMP

Maintenance records indicated the vacuum pump was installed by Dodson Aviation, Ottawa, Kansas on November 21, 2001. From the time of the pump's installation until the time of the accident, the airplane had flown a total of 222.5 hours. The pump was a "DRY AIR PUMP" manufactured by "AIRBORNE", model number 212CW, serial number 22C219. Documentation revealed the pump had been overhauled by Aero Accessories Inc., of Gibsonville, North Carolina on April 22, 1992.

The vacuum pump was separated from the accessory section and the pump's drive coupling was not located. The front flange was removed and the pump's rotor and rotor vanes were observed to be shattered. The inside of the pump exhibited a copious amount of a muddy substance. Neither the rotor, rotor vanes, or any of its shattered parts were removed or disturbed. The pump's front flange was secured back into place to preserve the rotor and rotor vanes for further examination.

The vacuum pump was subsequently sent to the NTSB Materials Laboratory in Washington, D.C., for examination. An NTSB mechanical engineer reported the vacuum pump received for examination was supplied with the two assembly bolts removed, and was in the two major pieces. The front flange of the pump revealed four fracture surfaces on the forward face of this flange and a fracture on the rear portion of the coupling, which was still attached to the coupling driven end. The fracture faces revealed a rough grainy surface consistent with overload.

Examination of the shaft assembly revealed that it rotated easily within the front flange and that one of the three pins on the shaft assembly was missing its rubber sleeve. The components within the front flange portion of the pump revealed no indications of wear or contamination on the packing seal, the washer seal, the bearing or the bearing surface of the shaft assembly.

The rear portion of the coupling revealed the fracture face consisted of a shallow cone centered on the coupling center with circumferential lines at the outer edge. These signatures were consistent with an overstress fracture at the coupling's designed shear point. The outer edge of the coupling fracture also displayed areas of multiple radial lines initiating at the outer surface.

Examination of the coupling piece's exterior surface revealed two mold parting lines on the outermost edge that were aligned with the longitudinal axis of the coupling. The parting lines on opposite sides of the centerline were both dislocated in the direction of rotation, consistent with excessive resistance of the pump during the fracture process.

The rear portion of the pump consisted of the back flange, the attached housing, and broken pieces of the rotor and vanes. The vane slots in the rotor were inclined in the direction of rotation.

The six vanes, identified as V1 through V6, were removed from the housing and measured in their length. The length of each vane was as follows:

V1 0.589 inch

V2 0.570 inch

V3 0.591 inch

V4 0.571 inch

V5 0.575 inch

V6 0.582 inch

Refer to the NTSB Materials Laboratory Factual Report for a detailed examination of the pump's vanes, housing chamber, and pump rotor.

On January 18, 2005, under the supervision of an FAA airworthiness inspector, the vacuum pump was examined at the facilities of Aero Accessories, Inc., Gibsonville, North Carolina. In addition to the FAA representative, also present for the examination were representatives of Aero Accessories, Parker Hannifan and Raytheon Aircraft. As a result of this examination it was reported by Aero Accessories personnel that it appears that sometime in the recent past the pump's rotor, vanes, and coupling were replaced by an unknown party with parts from an unknown source. After the examination had been concluded the pump was shipped back to the IIC

ADDITIONAL INFORMATION

The airplane wreckage was released to the owner's representative on March 18, 2004.