One Dead in Apparent Midair Break-Up
The NTSB has released its preliminary report a 17 August 2023 accident in which a Piper PA-28-161, registration N9855S, was destroyed and its two occupants, a pair of Certified Flight Instructors (CFIs), were fatally and seriously injured respectively when the aircraft impacted a building in the vicinity of Ft. Pierce, Florida. The airplane was operated by Aviator College under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 as an instructional flight.
According to the flight instructor seated in the left seat, the purpose of the flight was to conduct a Title 14 CFR Part 141 proficiency check in order for the flight instructor seated in the right seat to begin instructing at the flight school. The flight departed from Treasure Coast International Airport (FPR), Fort Pierce, Florida and proceeded about ten-miles southwest to perform a variety of training maneuvers. The left seat instructor reported that the right seat instructor satisfactorily demonstrated maneuvers including chandelles, lazy eights, and slow flight. Subsequently, the right seat instructor asked him, “Can you show me something new?”
The left seat instructor responded that given he was already an instructor, there were no new maneuvers, but added, “I can show you an EASA [European Union Aviation Safety Agency (EASA)] maneuver.” He described that the maneuver involved a power-off aerodynamic stall and recovery without the use of engine power. The left seat instructor took the flight controls and initiated the demonstration; he pitched up and entered a full aerodynamic stall, with power at idle. After the airplane stalled, he recalled pitching to “Vg” (glide airspeed, 73-knots) to recover from the stall. During the recovery, with power at idle, he stated, “the right wing came off” and there was an “abrupt banking tendency” to the right.
He recalled that he retracted the flaps, and added rudder and aileron application, but his “eyes were getting blurry,” he was starting to see “white,” and the airplane was “losing altitude like crazy.” He also noticed that a lot of wind was entering the cockpit. Subsequently, his next memory was awaking in the hospital. He did not recall observing any other components depart the airplane.
Multiple witnesses located near the accident site reported a similar circumstance in which booms or bangs were heard with variable fast changing low and high power revving engine noises. Subsequently, the witnesses viewed the airplane as it descended in a near vertical spinning descent, with both wings separated from the fuselage and numerous additional pieces of debris falling from the sky. A mobile phone video showed one wing falling to the ground.
The fuselage, with the engine remaining attached to the airframe, impacted an aluminum frame building that housed a Recreational Vehicle (RV). The airplane came to rest after descending through the building and partially into the RV. Both wings and two horizontal stabilator sections separated from the airplane in-flight and were located about 700-800-feet east of the fuselage. Fragments of the cabin door were also located several hundred feet from the fuselage, along with miscellaneous items from within the cabin, such as the tow-bar.
The entirety of the accident aircraft’s flight-control surfaces were located in the debris area. Rudder control continuity was confirmed from the cockpit to the control surface. Aileron control continuity could not be determined from the cockpit to the control surface due to the wings separating in-flight, however, the cable separations displayed frayed ends consistent with overload separation.
Stabilator flight control continuity was confirmed from the cockpit to the aft area of the fuselage. The left stabilator hinge bolt was intact and installed with fuselage structure attached and fractured from the fuselage. The right stabilator hinge bolt was intact and installed in the fuselage with portions of the right stabilator hinge fitting retained.
The main spar center box structure remained installed in the fuselage and was cut from the fuselage for further examination. There was a pronounced symmetrical upward curve of the upper and lower spar caps. The upper spar cap was buckled (s-bend) with an upward buckle about 12-inches from the left side and a downward buckle and fracture of the cap about 21-inches from the right side. The upper and lower left and right wing fittings were fractured with portions retained in the center section. All wing attach bolts remained installed and were observed intact.
There was no noticeable deformation of the right lower wing fitting horizontal leg that was retained in the center section, but the web was bent aft. The right upper wing fitting that was retained in the center section was deformed upward. There was no noticeable deformation of the left lower wing fitting horizontal leg that was retained in the center section, but the web was bent aft. The left upper wing fitting that was retained in the center section was deformed slightly upward.
The right wing sustained relatively minor damage. The right flap, aileron, and landing gear remained installed on the wing. The upper main spar wing fitting was fractured through the second rivet hole outboard of the outboard wing attachment bolts on both the forward and aft legs. The fractured end of the main spar upper fitting was deformed upward. The lower main spar wing fitting was fractured through the outboard wing attach bolt holes and there was slight upward deformation at the fracture location. The angled spar web between the fittings was intact with no obvious deformation. A portion of the wing skin above the upper fitting was peeled up and outboard. There was a cable tear in the inboard root rib forward of the aileron cable hole and in the upper wing skin. The upper-flange of the root-rib had outward crushing damage.
The left wing sustained relatively minor damage. The left flap, aileron, and landing gear remained installed on the wing. The forward and aft attach bolts remained intact and installed with portions of the fuselage structure attached and fractured from the fuselage. The upper main spar wing fitting was fractured about 3⁄4-inch outboard of the outboard wing attach bolt hole coincident with the edge of the main spar upper center section spar cap.
The fractured end of the main spar upper fitting was deformed upward slightly. The lower main spar wing fitting was fractured through the first rivet hole outboard of the outboard wing attachment bolt holes on both the forward and aft legs. There was slight upward deformation at the fracture location. The angled spar web between the fittings was fractured and deformed forward. The upper flange of the root rib had outward crushing damage. The wing and flap aft of the main spar was crushed down and outboard.
Preliminary examination of the wing fracture surfaces, conducted by the National Transportation Safety Board Materials Laboratory, found that by unaided eye and by stereo microscope, all fracture surfaces displayed features that were consistent with overstress separation. There were no indications of fatigue fractures observed.
According to the airplane’s maintenance records, the most recent one-hundred-hour inspector was completed on 29 June 2023. The endorsement noted that Airworthiness Directive AD 20-26-16 Wing Spar Integrity was complied with, and at the time of this inspection, the factored hours were 1,199.1. The endorsement noted that no further AD action was required until the airplane had accumulated five-thousand factored hours.
On 22 March 2021, an eddy current inspection per AD 2020-26-16 was completed and both wings, and forward and aft spars were marked as accepted. At this inspection, the airframe was noted to have a time in service of 15,572.9 hours. The factored service hours for both wings were 15,405.02 hours. The endorsement noted that during the non-destructive testing, no defects were found and new wing spar bolts and nuts were installed.
The airplane was retained for further examination.