N5547YSocata TB 10

On December 17, 2020, about 1637 eastern standard time, a Socata TB10, N5547Y, was destroyed when it was involved in an accident near Pembroke Pines, Florida. The pilot and two passengers were seriously injured, and one passenger was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot stated that the airplane was within the weight and balance envelope, and he performed a preflight inspection of the airplane using the airplane manufacturer’s checklist with no discrepancies reported. As part of his inspection, fuel samples taken from the three drainage points were free of water and debris. He verified the rear seat occupants were in their seats with their restraints fastened and then assisted the right front seat occupant, who was a minor, by fastening and tightening his restraint; he then closed and secured the airplane door. He started the engine with no issues and gave a safety briefing to the passengers that included the use of seatbelts, exits, and the sterile cockpit rule. He contacted ground control to request his instrument flight rules (IFR) clearance, received the automated terminal information service, and obtained taxi clearance to runway 28L. He taxied to the run-up area for runway 28L.

While in the run-up area, the pilot completed the “Engine Run-Up” checklist; each magneto drop was 75 rpm, which was within limits. The check included application of carburetor heat, and he noted a small decrease in engine rpm, which quickly returned when carburetor heat was turned off. He then advanced the throttle wide open and noted 2,700 rpm with no issue. Once the engine checks were completed, he contacted the control tower and advised he was ready to depart, keeping the engine rpm at 1,200 with the mixture slightly leaned to avoid fouling the spark plugs while waiting for his IFR release. He also set the flaps and trim to the takeoff positions, confirmed the magneto switch was on “both,” the propeller control was full forward, carburetor heat was off, the auxiliary fuel pump was on, and all engine gauges and voltmeter were in the green arc. During an interview, the pilot stated that the fuel selector was not moved at any time from the right tank position it was in when he first boarded the airplane to begin the flight.

According to a partial transcription of communications, the pilot contacted local control at 1626:34 and advised that he was holding short of runway 28L ready to depart. The controller acknowledged and informed him he was waiting for the IFR release. At 1634:34, the controller cleared the flight to takeoff. There was no distress call made by the pilot.

An airframe and powerplant mechanic who also held a commercial pilot certificate was working on an airplane in a hangar with the hangar doors open with his son nearby and was located about 760 ft south-southwest of the approach end of runway 28L. He reported that it was quiet, and the engine of the accident airplane was the only one that he heard. He did not hear the engine run-up but did hear when throttle was applied for takeoff. He reported hearing a “definite hard miss” like the engine was running on three cylinders, which in his opinion “definitely” could have been heard by the pilot, and it was this sound that got him to walk out of the hangar. He kept hearing the abnormal sound as the airplane travelled down the runway, and it surprised him that the pilot elected to continue the takeoff because the engine sounded like it was not making good power. The witness estimated that he heard the airplane for about 25 seconds until it was about halfway down the runway, and during that entire time, the engine was “running bad.”

Another pilot-rated witness who was in the same location as the previous witness reported that he did not hear the engine run-up but did hear the airplane’s engine “popping and banging” from the time of full power application until he lost sight of it. The witness reported that the airplane became airborne when it was abeam the intersection of runway 28L and runway 1R (about 1,542 ft from the threshold of 28L). The popping and backfiring continued as the airplane became airborne, and the flight never climbed above the height of the control tower. The airplane climbed to between 50 and 100 ft above ground level (agl), then descended, and then began to climb again; the climb was not steady. The witness added that the engine problem “never cleared itself” and continued until he lost sight of the airplane.

The pilot stated that once he was cleared to takeoff, he re-checked the takeoff checklist and moved the mixture control to full rich. After lining up on the runway, he added full throttle and guarded the carburetor heat (off), throttle, propeller, and mixture controls as he accelerated with all engine gauges in the green. He “obtained 65 knots within normal takeoff distance.” He rotated then pitched for 73 knots. At 100 ft agl, the airplane would not climb, and the airspeed started to decrease resulting in the stall warning horn sounding. With a significant loss of engine power, he attempted to maintain 70 knots but was unable, and he made small pitch adjustments to stay above 65 knots. He raised the flaps and struggled to keep the airspeed from going below 65 knots while slowly losing altitude.

The pilot further stated he knew the best place to land was a park, and he initiated a slight left bank and leveled the wings. Seconds later, while about 20 ft agl, the airplane collided with a tree and then impacted the ground and a fence. Immediately after the airplane impacted the ground, it became engulfed in flames. He exited the left side of the airplane by kicking and punching out the side window. Once outside of airplane, he noticed the passengers in the right front and left rear seats (both minors) struggling to release their seatbelts. He entered the aircraft and assisted both out of their seatbelts and out of the airplane. A few seconds later, he noted the adult passenger who had been in the right rear seat had already exited the aircraft by unknown means on the right side of the aircraft.

According to ADS-B data, the first target associated with the flight was located just past the departure end of runway 28L. The flight continued in a west-southwesterly direction about 0.6 nautical mile past the departure end of the runway where the last target was near the resting position of the wreckage.

Multiple pilots who had flown the airplane in the days leading up to the accident reported no issues with the airframe or engine. One pilot who flew the airplane 4 days before the accident reported magneto drops of about 75 rpm from each magneto during the engine check before takeoff and a maximum rpm of 2,700 during the takeoff roll. Another pilot who flew the airplane 3 days before the accident reported magneto drops within 25 rpm of each other, which was “satisfactory” and within the limits specified by the Pilot’s Operating Handbook.

The airplane was not equipped with an engine monitor or a carburetor temperature gauge. A portable ADS-B transceiver and a tablet computer were recovered from the wreckage. The portable ADS-B transceiver did not have data recording functionality. The tablet was accessed, and the ForeFlight application was running in the background. Validated recorded data for the accident flight from ForeFlight totaled about 1 minute 26 seconds, beginning at 1635:11 when the flight was near the displaced threshold for runway 28L, and ending at 1636:37, when the flight was near the final resting position. The downloaded data indicated that takeoff was initiated using the displaced threshold, and the airplane was about 1,520 ft from the runway 28L threshold when it attained 59 knots groundspeed or 64 knots indicated airspeed based on the headwind component. That location was on the runway 28L centerline and right of the runway 1R centerline.

According to the airplane’s maintenance records, the left and right front seat restraints were replaced with Anjou Aeronautique 3491423-12-070 16 G restraints at the airplane’s last annual inspection to comply with Airworthiness Directive (AD) 2003-26-06. The rear seat restraints, which were Pacific Scientific part numbers 0108168-11 and 0107119-55, were not changed as they were not affected by the AD.

According to the Pilot’s Operating Handbook, at design maximum gross weight, the environmental conditions that existed at the time of the accident, and the pilot-reported flight configuration of takeoff flaps, the takeoff roll and distance to clear a 50-foot obstacle were about 1,135 ft and 1,765 ft, respectively. Based on the pilot-reported weight and balance calculations, the airplane was about 12 pounds under design gross weight at the start of the flight. A note in the performance section of the Pilot’s Operating Handbook specified that the distances were to be reduced by 10% for each 10 knots of headwind.

After an uneventful flight on December 14, 2020, the airplane was fueled per the club policy, and 8.51 gallons of 100 low lead fuel were added. The airplane had not been operated between the conclusion of the flight on December 14, 2020, and the accident flight.

According to the manager of the fuel facility that supplied the fuel for the airplane, there was no water contamination of their fuel found either by visual inspection of a sample or from a water sensor installed in the tank. Additionally, there were no reports of any fuel related issues from any of the aircraft fueled from the same source.

The wind, temperature, dew point, and altimeter reported at HWO at 1640 about 3 minutes after the accident were 340° at 10 knots, 75°F, 70°F, and 30.06 inches of mercury, respectively. According to Special Airworthiness Information Bulletin (SAIB) CE-09-35, Carburetor Ice Prevention, these conditions correlated to about 80% humidity and were conducive to serious carburetor ice at glide power. The wind direction and velocity correlated to a 5-knot headwind component for takeoff on runway 28L.

SAIB CE-09-35 stated that carburetor ice can be detected in aircraft equipped with a constant speed propeller by a drop in manifold pressure and usually by a roughness in engine operation.

The SAIB further stated that pilots should be aware that carburetor icing doesn’t just occur in freezing conditions, it can occur at temperatures well above freezing temperatures when there is visible moisture or high humidity. Icing can occur in the carburetor at temperatures above freezing because vaporization of fuel, combined with the expansion of air as it flows through the carburetor, (Venturi Effect) causes sudden cooling, sometimes by a significant amount within a fraction of a second.

Multiple pilots who had flown the airplane in the days leading up to the accident reported no issues with the airframe or engine. One pilot who flew the airplane 4 days before the accident reported magneto drops of about 75 rpm from each magneto during the engine check before takeoff and a maximum rpm of 2,700 during the takeoff roll. Another pilot who flew the airplane 3 days before the accident reported magneto drops within 25 rpm of each other, which was “satisfactory” and within the limits specified by the Pilot’s Operating Handbook.

The airplane was not equipped with an engine monitor or a carburetor temperature gauge. A portable ADS-B transceiver and a tablet computer were recovered from the wreckage. The portable ADS-B transceiver did not have data recording functionality. The tablet was accessed, and the ForeFlight application was running in the background. Validated recorded data for the accident flight from ForeFlight totaled about 1 minute 26 seconds, beginning at 1635:11 when the flight was near the displaced threshold for runway 28L, and ending at 1636:37, when the flight was near the final resting position. The downloaded data indicated that takeoff was initiated using the displaced threshold, and the airplane was about 1,520 ft from the runway 28L threshold when it attained 59 knots groundspeed or 64 knots indicated airspeed based on the headwind component. That location was on the runway 28L centerline and right of the runway 1R centerline.

According to the airplane’s maintenance records, the left and right front seat restraints were replaced with Anjou Aeronautique 3491423-12-070 16 G restraints at the airplane’s last annual inspection to comply with Airworthiness Directive (AD) 2003-26-06. The rear seat restraints, which were Pacific Scientific part numbers 0108168-11 and 0107119-55, were not changed as they were not affected by the AD.

According to the Pilot’s Operating Handbook, at design maximum gross weight, the environmental conditions that existed at the time of the accident, and the pilot-reported flight configuration of takeoff flaps, the takeoff roll and distance to clear a 50-foot obstacle were about 1,135 ft and 1,765 ft, respectively. Based on the pilot-reported weight and balance calculations, the airplane was about 12 pounds under design gross weight at the start of the flight. A note in the performance section of the Pilot’s Operating Handbook specified that the distances were to be reduced by 10% for each 10 knots of headwind.

After an uneventful flight on December 14, 2020, the airplane was fueled per the club policy, and 8.51 gallons of 100 low lead fuel were added. The airplane had not been operated between the conclusion of the flight on December 14, 2020, and the accident flight.

According to the manager of the fuel facility that supplied the fuel for the airplane, there was no water contamination of their fuel found either by visual inspection of a sample or from a water sensor installed in the tank. Additionally, there were no reports of any fuel related issues from any of the aircraft fueled from the same source.

Examination of the accident site revealed the outer section of the left wing with attached aileron was located in the first or primary impacted tree; the tree trunk was fractured about 8 ft above ground level. The main wreckage consisting of the fuselage with attached right wing and empennage came to rest upright near the base of a large tree adjacent to a road. The fuselage came to rest heading about 180° opposite the direction of flight about 3,900 ft west-southwest from the departure end of the runway 28L. The cockpit and cabin portions of the fuselage were nearly consumed by a postcrash fire.

Examination of the flight controls for roll, pitch, and yaw revealed no evidence of preimpact failure or malfunction. The flaps were in the retracted position based on the position of the flap motor.

Fuel consistent with 100 low lead was noted in the right fuel tank with no evidence of water or contaminants; the amount was not quantified. The left fuel tank was ruptured with no fuel remaining. Examination of the right fuel vent system revealed it was free of obstructions from the end of the vent tube at the bottom of the wing into the fuel tank. The right fuel supply system was continuous from the tank to the fuel selector valve to the auxiliary fuel pump; the line between the auxiliary fuel pump and the engine-driven fuel pump was heat damaged. Examination of the left fuel vent system revealed the vent line was burned and exhibited internal contamination that was consistent with organic material. The left fuel supply line was damaged between the fuel tank and the selector valve.

Examination of the cockpit and cabin revealed the fuel selector was positioned to the left fuel tank. The fuel selector sustained heat damage but was internally free of obstructions. Small particles consistent with metallic shavings were noted in the valve filer bowl. Both front seats and the rear bench seat remained attached to the structure. A buckle assembly found in the right rear portion of the cabin and a buckle assembly with attached connector link found in the left rear portion of the cabin were retained. The buckle assembly for the right front seat position was not located.

Examination of the buckle assembly with attached connector link was performed by the NTSB Materials Laboratory. The buckle assembly had darkened due to fire exposure and was coated with melted aluminum from the burned aircraft structure. Melted aluminum fused the components of the buckle together, and the buckle could not be mechanically manipulated without possible destruction of the internal components. Consequently, the angle at which the link connector became disengaged from the buckle and the force required to open the buckle could not be reliably measured and compared to specifications. X-ray examination revealed the connector link appeared to align normally with the internal clips, and the amount of rotation of the link connected within the buckle also appeared normal and would not be expected to interfere with unlatching. The components of the belt buckle appeared to all be present and assembled correctly with no obvious visual damage. Consequently, there appeared to be nothing mechanically wrong with the buckle or connector link that would have precluded normal unlatching and operation.

Examination of the engine, which separated from the airframe, revealed the crankshaft was fractured aft of the crankshaft flange; the separated section of crankshaft flange remained connected to the propeller flange. The engine exterior was discolored and sooty consistent with exposure to the postimpact fire. During rotation of the crankshaft using a tool inserted in the vacuum pump drive pad, crankshaft, camshaft, and valve train continuity were confirmed. Compression and suction were observed from all cylinders. Borescope inspection of the cylinders revealed no anomalies. The engine-driven fuel pump was impact fractured, and the pumping section separated from the engine. The pump’s rubber diaphragm was fire destroyed but the internal valves appeared normal. The pump’s actuator rod was observed to move normally up and down during crankshaft rotation.

The carburetor remained attached to the engine and exhibited exterior discoloration and soot consistent with exposure to the postimpact fire. The carburetor’s two right side attaching nuts were secure and required normal force to remove, and the two left side nuts were finger loose. The mounting gasket exhibited gray coloration on the side where the nuts were secure and pink coloration on the side where the nuts were finger loose. No liquid drained from the carburetor when it was inverted. The throttle and mixture control cables remained attached to their respective control arms; both control cables were fractured consistent with impact. The throttle control was in the full throttle position, and the mixture control was midrange. The carburetor fuel inlet screen was unobstructed.

Heat damage to the carburetor precluded operational testing. Disassembly inspection revealed extensive heat damage to each float pontoon. Very small specks of material were noted in the carburetor bowl including gasket material that flaked off during disassembly, but there were no obstructions of the main discharge fuel delivery path.

The air induction and exhaust systems were free of obstructions; tan to light gray exhaust deposits were observed in the exhaust tubing. Examination of the lubrication system revealed an unquantified amount of oil in the engine. The oil suction screen and the oil filter media were absent of debris.

Examination of the ignition system revealed the single-drive dual magneto remained securely attached to the engine. Magneto to engine timing could not be determined. The magneto was removed and produced spark from all eight ignition towers during hand rotation. The ignition harness was impact and fire damaged.

Examination of the single drive dual magneto revealed both point gaps were less than the minimum specified; the exact amount could not be determined as a measuring tool was not available. Both capacitors passed all tests consisting of the internal leakage, series resistance, and capacity tests. The capacitors were then placed in a test bench cap for operational testing at room temperature and fired strong at all gaps. The magneto was then subjected to testing after being heated to an exterior temperature of about 171°F, which revealed no evidence of preimpact failure or malfunction.

Examination and operational testing of all spark plugs was conducted without cleaning or any other manipulation performed. All were gapped within specification, passed the resistance test, and passed operational testing at 80 psi producing a bright blue spark consistent with normal operation.

The propeller governor remained attached to the engine, and no damage was noted. The propeller governor control cable was separated about 6 inches from the governor control arm. The arm remained attached to the governor and was observed in a full increase rpm position. The governor oil screen was absent of debris.

Examination of the separated propeller revealed one blade was uniform in shape with no observable bends, leading edge gouging, or chordwise scratches. The other blade was bent rearward with no evidence of leading-edge gouging or chordwise scratches.