Willows, CA, USA
N4487D
Beech G35
According to witnesses, the airplane was seen approaching the motor sports park from the southwest at approximately 1,200 feet agl and at a "faster than usual" rate of speed. The airplane was in a "sharp, 90-degree bank," as it began to circle the park in a level turn. After circling around to the east, the airplane returned to a wings-level attitude and began to climb. Shortly thereafter, the tail of the airplane began to "shake violently" and separate from the airplane. One witness said he heard a loud noise as "the tail came off, and all of it started falling apart." He said the tail section separated first, then the airplane pitched over, and the left wing broke off. Witnesses saw the airplane enter a downward spiral. As the airplane descended, the engine separated and the passenger was ejected. The airplane then entered an inverted flat spin and impacted the ground 1,000 feet north of park. An examination of the airplane's left wing, and stabilizers revealed structural failures consistent with overload. According to the manufacturer's Flight Strength Diagram or Vn diagram for the G35, abrupt control column deflection at a speed of 113 knots (Va, or maneuvering speed) could produce a 4.4 G structural load (Limit Load factor), while abrupt control column deflection at or above 152 knots (Vno/Vc, or maximum structural cruise speed) could produce a 6.6 G structural load (Ultimate Load limit). Examination of the recorded radar data disclosed that the airplane was traveling at 142 knots at the time of the breakup. Engineering analysis concluded that in a level turn, the bank angle required to achieve Limit Load is 76.8 degrees, and the bank angle required to achieve the Ultimate Load is 81.2 degrees. FAA toxicology testing of the pilot revealed the presence of Diphenhydramine in urine, and Norverapamil, and Verapamil in urine and liver.
HISTORY OF FLIGHT On April 11, 2002, at 1006 Pacific daylight time, a Beech G35, N4487D, owned and operated by the pilot, was destroyed following an in-flight breakup and subsequent impact with terrain approximately 7 miles west of Willows, California. The private pilot and his passenger were fatally injured. Visual meteorological conditions prevailed. No flight plan had been filed for the personal flight being conducted under 14 CFR Part 91. The flight originated at Red Bluff, California, at approximately 0950. The accident occurred near the Thunderhill Motorsports Park. At the time of the accident, the park was open and drivers were road-testing their cars on the track. Several safety officials, who were monitoring the track, witnessed the accident. Two witnesses said that the airplane approached the racetrack from the southwest. Witness #1, who was located in the Turn 5 tower, said the airplane approached the track from the west near turn ten (see attached track diagram) at approximately 1,200 feet above the ground. He watched it for a few seconds before his attention was diverted. When he saw the airplane again, it was south of the track, flying over the water tank. He said that it was traveling "faster than usual," and the airplane was in "sharp, 90-degree bank," as it began to circle the park in a level turn. The airplane continued to circle the track, going towards the east then towards the north. After circling around the east side of the track, the airplane returned to a wings-level attitude and began to climb. As soon as it began to climb, the tail started to shake and pieces of it came off. He said when the tail pieces fell off, the airplane went into a flat, inverted, counter clockwise spin, and it hit the ground. Witness #2, who was located in the Start-Finish tower, first noticed the airplane as it was turning near the water tank. It was approximately 1,200 feet above the ground. The airplane was flying normal, but was "kind of banking, [in] an easy, constant turn." The airplane wasn't going "real fast," or "real slow." As the airplane continued to circle around the east side of the track, it "started to climb a little bit more as he was making a bank." The witness stated that as the airplane was turning to the north, he said the empennage began to shake "violently" and then separate from the airplane. He said he heard a loud noise and "the tail just came off, and all of it started falling apart." He said the tail section separated first, then the airplane pitched over and the left wing broke off. When the airplane began to spiral down, the engine separated and the passenger was seen to fall out. The airplane then entered an inverted flat spin and impacted the ground 1,000 feet north of the race track. PERSONNEL INFORMATION The pilot held a private pilot certificate with an airplane single-engine land rating, dated July 30, 1973; a mechanic's certificate with airframe and powerplant ratings, dated June 7, 1991, and a third-class airman medical certificate, dated December 5, 2001, with the limitation, "Not valid for any class after December 31, 2002." According to the pilot's flight logbook, he had accumulated a total of 1,617.0 flight hours. Categories of flight time were not given. His last flight review was dated January 11, 2002. As of the last logbook entry, dated April 6, 2002, he had accumulated 16.0, 8.5, and 2.9 hrs in the previous 90, 60, and 30 days, respectively. The pilot was a retired aeronautical engineer. AIRCRAFT INFORMATION N4487D, a model G35 (S/N D-4612) was manufactured by the Beech Aircraft Corporation in April 1956. It was equipped with a Continental E225-8 engine, (s/n 36328-D-70-8-R), rated at 225 horsepower, equipped with a Hartzell (m/n HC-A2MV204A1 two-blade, all metal, constant speed propeller. According to the maintenance records, the pilot did all the routine maintenance and 100-hour inspections on the airplane. On November 1, 2000, both ruddervators were removed for repair. The left ruddervator was reskined, and both ruddervators were repainted and balanced checked. The most recent 100-hour/annual inspection was completed on June 12, 2000, at an airframe total time of 6,058.0 hours. According to aircraft records, on January 1,1988, Beech Kit 35-4016-3 was installed on the empennage in accordance with Beechcraft Mandatory Service Bulletin No. 2188. The kit included stabilizer reinforcement components and instructions on inspecting the empennage and aft fuselage. On June 6, 2000, the airplane was complied with AD 94-20-04 inspection, which listed ruddervader balance requirements and the inspection of the aft fuselage. At the time of the accident, airframe total time was 6,119.4 hours, and engine total time was 1,658.6 hours. METEOROLOGICAL INFORMATION Weather recorded at 0948 at Chico Municipal Airport, located approximately 26 nautical miles northeast of the accident site, was: wind, calm; visibility, 40 statute miles; sky condition, broken at 9,500 feet and 25,000 feet; temperature, 18 degrees C; altimeter setting, 30.15. WRECKAGE AND IMPACT INFORMATION The wreckage was confined to an area of approximately 1,000 square feet. The left wing, engine cowling, left ruddervator, and left main landing gear door were located in the southeastern quadrant. The right ruddervator was located in the southwestern quadrant. The engine and attached propeller, and the right and left ruddervator balance weights were located in the northwestern quadrant of the debris field. The terrain was a soft, irrigated, and cultivated field with low vegetation. The inverted fuselage and attached right wing impacted the ground on a magnetic heading of 360 degrees. The left wing was located approximately 490 feet at 162 degrees from the fuselage. The engine and attached propeller were located approximately 410 feet at 286 degrees from the fuselage. The engine was embedded in the ground approximately 3 feet deep. The distance between the engine and the left wing was approximately 800 feet. The associated ground scar and crush lines on the fuselage were consistent with the airplane being in a flat, inverted, counter clockwise spin, as stated by witness #1. The upper portion of the cabin was crushed downward to the right and aft. The engine and propeller, engine cowling, and nose cowling were missing. The nose landing gear doors were closed. The attached right wing was buckled downward at a position approximately 7 feet inboard of the wing tip. The right main landing gear doors were closed. The right wing's aileron and flap were still attached. The aft portion of the fuselage was crushed downward. The left and right ruddervators and tail cone were missing. Inboard sections of the forward and aft spars, for the left and right ruddervators, remained attached to the fuselage. There was an 8-inch tear in the fuselage skin, beginning at and extending from a fuselage pass through hole in front of the forward spar attachment point for the left stabilizer at fuselage station (F.S.) 256. The left ruddervator trim cables, each attached to half of the elevator tab horn, were extending through the tear. There was an 1-inch tear in the fuselage skin, beginning at and extending from a fuselage pass through hole in front of the forward spar attachment point for the right stabilizer at F.S. 256. A portion of the fractured right ruddervator trim cable extended through the tear. The upper left portion of the wing's forward spar carry-through structure was fractured and bent downward. The lower left portion of the wing's forward spar carry-through structure was fractured, buckled, and compressed inward. The forward attachment fitting for the left wing was missing. A 2-foot-wide section of fuselage skin, surrounding the lower portion of the left wing root area, was separated from the fuselage. This section of skin was curled and crushed inward across the bottom of the fuselage. Paint and rubber transfer marks and scratches across the bottom of the fuselage, the underside of the right wing, and right wing flap were consistent with paint transfer marks and scratches on the underside of the separated left wing and the left main landing gear tire. The left wing was buckled upward at a position approximately 7 feet inboard of the wing tip. The aileron and flap were still attached. Both forward and aft attachment fittings were still attached. The left stabilizer was located with approximately 3 feet of the outboard portion of the ruddervator still attached. The left ruddervator balance weight, trim tab, and inboard portion of the ruddervator with pitch control horn were separated from the left stabilizer. Paint transfer marks and scratches located on the inboard lower portion of the left stabilizer were consistent with paint transfer marks and scratches located on the left side of the aft fuselage. The left ruddervator pitch control horn was located with the attached inboard section of the ruddervator. The right stabilizer was located with the ruddervator still attached. The trim tab was crushed forward, buckling and compressing the right ruddervator at the trim tab cable attachment point. The right ruddervator balance weight and pitch control horn were both separated from the ruddervator. The right ruddervator pitch control horn was located with a section of the ruddervator push-pull tube still attached to the rod end. An odor of fuel was present at the main impact site and also at the location of the left wing. Oil splatter surrounded the engine's impact site. There was no fire. An examination of the engine and other airplane systems revealed no anomalies. MEDICAL AND PATHOLOGICAL INFORMATION On April 15, 2002, autopsies were performed on the pilot and passenger in Chico, California, by authorization of the Glenn County Coroner's office, Willows. The Federal Aviation Administration (FAA) Civil Aeromedical Institute (CAMI) performed toxicological screenings on the pilot. According to CAMI's report (#200200095001), carbon monoxide was not detected in blood, and ethanol was not detected in urine. Cyanide screening was not performed. Diphenhydramine, Norverapamil, and Verapamil were detected in the urine, and Norverapamil, and Verapamil were detected in the liver. Glucose was detected in vitreous (98 mg/dl) and urine (4700 mg/dl), and 10.8 percent hemoglobin was detected in blood. The report stated that the "abnormally high postmortem vitreous glucose levels" and the "elevated postmortem levels of glucose in the urine could have been caused by diabetes mellitus or several other medical conditions, which may or may not have been a factor in the accident." According to FAA medical records, on December 5, 1994, CAMI determined that the pilot did not meet the medical standards prescribed in Title 14 CFR Part 67 due to hypertension. On January 20, 1995, CAMI determined that the pilot did not meet medical standards due to his uncontrolled diabetes mellitus. On March 10,1997, the pilot was denied a medical certificate due to his history of diabetes, but was granted authorization for a special issuance of a third-class medical under 14 CFR Part 67.401. On May 20,1999, he was again denied a medical certificate due to diabetes mellitus. On June 16,1999, the pilot was asked to surrender his third-class medical certificate. A new third-class medical certificate was issued on January 13, 2000, stating, "Not valid for any class after December 31, 2000." Thereafter, the pilot received successive special issuance third-class medical certificates for 2001 and 2002. The NTSB's Medical Officer reviewed those records maintained by the FAA Aeromedical Certification Division, the pilot's personal physician, and other documents. In a letter dated November 1, 2001, to the manager of the FAA Aeromedical Certification Division, the personal physician stated that the pilot's "diabetes is adequately controlled." On November 19, 2001, a letter to the pilot, from the manager of the FAA Aeromedical Certification Division stated "you are ineligible for third-class medical certification. However, I have determined that you may be granted authorization for special issuance of third-class airman medical certification." On November 30, 2001, in the pilot's medical records, the physician identified that the pilot took several different daily medications, which included Avapro, Covera, Glucotrol XL, Lopid, and hydrochlorothiazide. The physician also stated that "The pilots blood pressure has been in a slightly higher range. Today it was taken twice in the office at 153/99 and 166/97." On February 14, 2002, the pilot's physician noted; "Blood pressure 154/80." TESTS AND RESEARCH The airplane's weight and balance documents were not located. The pilot, passenger, and cargo weights were determined, but the total fuel on board at the time of the accident was not determined. According to the Raytheon Aircraft Company, the basic empty weight for this airplane is approximately 1,942 pounds. A manufacturer's representative from Raytheon Aircraft Company, provided two weight and balance calculations, one with full fuel and a second with zero fuel. In the first (full fuel) calculation, the center of gravity was computed to be 81.3 inches aft of datum, which is forward of the approved center of gravity range of 81.7 to 85.5 inches aft of datum. In the second (zero fuel) calculation, the center of gravity was computed to be 81.2 inches aft of datum, which is within the approved center of gravity range of 77.5 to 85.7 inches aft of datum. During a follow-up on-site interview, witness #1 was asked to identify the altitude of the airplane while it was in the vicinity of the water tank. Calculations, based on the angle of elevation of his outstretched arm corresponded to an angle of approximately 13 degrees. A 13-degree angle of elevation would correspond to an airplane altitude of approximately 850 feet msl (550 feet agl). During a follow-up on-site interview, witness #2 was asked to identify the altitude of the airplane when it was in the vicinity of Ring Road. Calculations, based on the angle of elevation of his outstretched arm corresponded to an angle of approximately 21 degrees. A 21-degree angle of elevation would correspond to an airplane altitude of approximately 1,000 feet msl (700 feet agl). According to Oakland Air Route Traffic Control Center (ARTCC), the recorded radar data provided the following: the 17:00:51.7 UTC radar contact, in the vicinity of the water tank, was at an altitude of 2,500 feet msl (2,200 feet agl). The altitude of the 17:01:03.7 UTC radar only contact, south-southeast of the Turn 5 tower and in the vicinity of Ring Road, was calculated by averaging the change of altitude between the third to last and the last radar contacts. The radar only contact was at an altitude of approximately 2,200 feet msl, (1,900 feet agl). The last recorded radar contact, at 17:01:15.8 UTC and northeast of the Turn 5 tower, was at 1,900 feet msl (1,600 feet agl). A Raytheon Aircraft Company performance engineer, using a National Track and Analysis Program (NTAP), provided the following airplane performance data. - The airplane's calculated velocity was approximately 143 knots. - The airplane's descent rate was approaching 1,500 feet per minute (FPM). - The airplane's left roll angle was approximately 29 degrees. - The airplane's heading was passing 335 degrees (magnetic). A representative from Raytheon Aircraft Company used a Trajectory Analysis program that evaluates in-flight separations to calculate initial breakup conditions including altitude, position, heading, true airspeed, and flight path angle. The components used for this analysis included the engine, passenger, left wing, left stabilizer, and left ruddervator. To reproduce N4487D's debris field, it was determined that the in-flight separation occurred at a point approximately 800 feet east and 500 feet south of the engine's impact point. The altitude, at the time of the in-flight separation of the engine, was approximately 700 feet msl (450 feet agl). The in-flight separation occurred when the airplane's mass was in a 5-degree des
the pilot's entry into an abrupt maneuver at an excessive airspeed beyond Va, which resulted in exceeding the aircraft's design stress limits.
Source: NTSB Aviation Accident Database
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