N36TTBeech B36TC · 1983

On January 22, 2020, at 1211 Pacific standard time, a Beech B36TC Bonanza, N36TT, was substantially damaged when it was involved in an accident near Corona, California. The two pilots and two passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The occupants flew to Corona Municipal Airport (AJO), Corona, California to refuel. After landing on runway 7, the airplane taxied to the self-serve fuel tank. At 1130, the left-seated pilot fueled the airplane with the addition of 78.06 gallons of fuel.

The right-seated pilot paid for the fuel, and they departed about 30 minutes later. A witness observed the occupants board the airplane noting that one passenger was seated in the aft-facing right seat (center row) and the other was in the forward-facing left seat (aft-row). During the engine start, the witness heard the airplane backfire, making a very loud bang followed by a puff of black smoke and an arcing sound consistent with the engine being flooded with fuel during the hot start. Thereafter, witnesses observed the airplane depart.

A review of the mid-airport security camera video revealed that the airplane was midway down the runway (passing by the fuel tanks) at a relatively level pitch attitude and briefly became airborne before touching down on the runway again; the windsock showed an estimated 5-knot tailwind. The airplane became airborne again but remained close to the runway and the wings could be seen rocking back and forth. The airplane flew over about 200 ft of grass. The camera located at the end of the runway captured the airplane in the final 5 seconds it was on the runway, when the speed was about 65 knots and increased to about 70 knots, consistent with a 0.057 G acceleration. The airplane touched down just before it contacted a 6-ft-high chain-link airport perimeter fence. The airplane contacted a berm, became inverted, and travelled over the berm before coming to rest on the east side of the berm. The airplane was consumed by post-impact fire.

According to one witness, when the airplane reached about 1/3 of the way down the runway (between 1,000 and 1,2000 ft), the wheels lifted up and the airplane assumed a very nose-high attitude. Three witnesses stated that the airplane momentarily became airborne and bounced back down on the runway surface several times in a nose-high attitude.

The left-seat pilot’s personal notebook was found in the wreckage and indicated he had flown about 45 hours in the past year. It is estimated that he had acquired 3.7 hours in the accident airplane over the course of three flights, the last of which was in April 2019; it is unknown if he acted as pilot-in-command during any of those flights. He owned and regularly flew a 1978 Piper PA-28-161 Warrior II (equipped with a Lycoming O-320 engine and a lever-type throttle quadrant).

The right-seat pilot owned the airplane and according to the airplane logbooks, had flown over 650 hours in the airplane, of which about 5 hours were in 2019, no hours were in 2018, and 5 hours were in 2017. His personal logbooks were not located.

The Beechcraft B36TC Bonanza is an all-metal, low-wing airplane that can accommodate four to six seats.

The airplane was equipped with a vernier-style push-pull throttle, propeller, and mixture control knobs, which were located on the control console below the control wheel column and subpanel. The control knobs were designed to be repositioned by pushing a button on the face of the knob. With the button extended, fine adjustments could be accomplished by rotating the knob.

The airplane was equipped with traditional brakes on the left and right main landing gear. The brakes on the main landing gear wheels are operated by applying toe pressure to the rudder pedals. The aircraft was manufactured with the optional copilot brake pedals installed. Additionally, the aircraft was equipped with the optional dual control column (T-Type) which meant the airplane had two control yokes (one in front of each front seat).

Weight and Balance

Weight and balance computations were made for the accident takeoff and based on the airplane's empty weight, total moment, and center of gravity that were obtained from the maintenance records. The last weight record was from 1998 (the same time frame the pilot purchased the airplane) and showed an empty weight of 2,662 lbs. The fuel onboard at the time of the accident is unknown. Before departure, the airplane was fueled with 78 gallons (gals), but because it is unknown if that filled the tanks full, the takeoff condition was calculated for a full fuel tank condition (102 gals) and at 85 gals, which was computed from 78 gals added at the fuel tank and 7 gals in the tanks at the time of landing. The occupant weights and seating positions were obtained from witnesses, the coroner, Federal Aviation Administration medical records, and the families.

Calculations of the airplane’s gross weight at 85 gallons of fuel was 3,813 lbs and the center of gravity was 82.6 inches. The gross weight at 102 gallons of fuel was 3,910 lbs and the center of gravity was 83.1 inches. The maximum authorized gross takeoff weight was 3,850 pounds with the center of gravity range at that weight between 80 and 87.7 inches forward and aft, respectively.

Review of the Beech Pilot's Operating Handbook (POH) for the airplane revealed that with the flaps in the retracted position, at the maximum gross takeoff weight, the takeoff distance required at maximum effort was about 1,400 ft (see figure 1). The rotation speed was listed as 70 knots at and 82 knots to clear a 50 ft obstacle.

Figure 1: Performance Calculations

The Beechcraft B36TC Bonanza is an all-metal, low-wing airplane that can accommodate four to six seats.

The airplane was equipped with a vernier-style push-pull throttle, propeller, and mixture control knobs, which were located on the control console below the control wheel column and subpanel. The control knobs were designed to be repositioned by pushing a button on the face of the knob. With the button extended, fine adjustments could be accomplished by rotating the knob.

The airplane was equipped with traditional brakes on the left and right main landing gear. The brakes on the main landing gear wheels are operated by applying toe pressure to the rudder pedals. The aircraft was manufactured with the optional copilot brake pedals installed. Additionally, the aircraft was equipped with the optional dual control column (T-Type) which meant the airplane had two control yokes (one in front of each front seat).

Weight and Balance

Weight and balance computations were made for the accident takeoff and based on the airplane's empty weight, total moment, and center of gravity that were obtained from the maintenance records. The last weight record was from 1998 (the same time frame the pilot purchased the airplane) and showed an empty weight of 2,662 lbs. The fuel onboard at the time of the accident is unknown. Before departure, the airplane was fueled with 78 gallons (gals), but because it is unknown if that filled the tanks full, the takeoff condition was calculated for a full fuel tank condition (102 gals) and at 85 gals, which was computed from 78 gals added at the fuel tank and 7 gals in the tanks at the time of landing. The occupant weights and seating positions were obtained from witnesses, the coroner, Federal Aviation Administration medical records, and the families.

Calculations of the airplane’s gross weight at 85 gallons of fuel was 3,813 lbs and the center of gravity was 82.6 inches. The gross weight at 102 gallons of fuel was 3,910 lbs and the center of gravity was 83.1 inches. The maximum authorized gross takeoff weight was 3,850 pounds with the center of gravity range at that weight between 80 and 87.7 inches forward and aft, respectively.

Review of the Beech Pilot's Operating Handbook (POH) for the airplane revealed that with the flaps in the retracted position, at the maximum gross takeoff weight, the takeoff distance required at maximum effort was about 1,400 ft (see figure 1). The rotation speed was listed as 70 knots at and 82 knots to clear a 50 ft obstacle.

Figure 1: Performance Calculations

The accident site was in soft dirt about 360 ft from the departure end of the runway. The terrain was flat and populated by scattered mature large bushes. The main wreckage, consisting of the engine and remains of the fuselage, came to rest inverted near tall brush and burned the terrain in the surrounding 5 to 10 ft. The wreckage was consumed by post-impact fire and a majority of the fuselage, wings, and skin panels were destroyed.

The first identified points of contact were disrupted dirt and grass on the flat terrain on the far west end of the debris field. The markings started as two nearly parallel indentations in the vegetation about 105 inches apart. The indentations continued east a few ft toward the 6-ft fence. Four fence posts were folded over in the direction of the debris field and the stretched fence was still connected to adjacent upright post and laying on top of the berm. A center indentation appeared after the fence posts equally between the right and left indentation. The craters were consistent in size and orientation to that of the landing gear wheels (see figure 3). The indentations were continuous about 20 ft up the berm, which was higher than the surrounding terrain.

Figure 3: Ground Disturbances Leading to Debris Field

Postaccident examination of the engine revealed no evidence of a catastrophic failure. Investigators removed all cylinders' rocker box covers and noted a light oil film on the rocker arms and valve assemblies. The cylinders' combustion chambers were examined through the upper spark plug holes using a lighted borescope followed by the removal of three cylinders. The combustion chambers remained mechanically undamaged and evidence of rock and dirt ingestion in the cylinders appeared to be a result of the intake manifold being broken during the impact sequence. Investigators achieved manual rotation of the crankshaft by rotation of the propeller. Thumb compression was established in all cylinders. The magnetos were removed, and the shafts were rotated by a powered drill, during which spark was observed at each post. The turbocharger shaft moved freely upon rotation of the turbine and compressor wheel.

The throttle, mixture, and propeller knobs were all found full forward, but it could not be determined if this was the setting at the time of impact because the engine was displaced from the mounts and the cables could have been pulled forward. The throttle and mixture arms were attached to the throttle body with their respective cable attach fittings secured; the cables were thermally consumed. The auxiliary fuel pump switch was caged in the “off” position. The flaps lever was in the 0° position; the landing gear lever was in the extended position.

Control continuity was established onsite. The control cables were continuous to melted bellcranks and portions of the airframe. The airplane was equipped with a dual control yoke, but only the left yoke remained; the right yoke was consumed by fire. The elevator trim tabs were found in the full down position (full nose-up trim) and the actuators measured about 2 inches, which corresponded to 27° tab down, which was the maximum travel limit according to the Federal Aviation Administration type certificate data sheet (see figure 4). The elevator trim tab control cables were located under the floor assembly and routed along the belly of the aircraft to the tail. The cables were located on top of the wreckage following the post-impact fire, but the cables could change position during the impact sequence.

The airplane’s pilot's operating handbook stated that, for takeoff, the elevator trim should be set at 3° nose-up.

Figure 4: Left Stabilizer and Elevator

The landing gear were in the down position and the flaps appeared to be in the up position.