N9855SPiper PA-28-161 · 2002

On August 17, 2023, about 1202 eastern daylight time, a Piper PA28-161 airplane, N9855S, was destroyed when it was involved in an accident near Fort Pierce, Florida. One flight instructor was fatally injured and the other flight instructor sustained serious injuries. 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 for the flight school. The pilots departed from Treasure Coast International Airport (FPR), Fort Pierce, Florida, and proceeded about 10 miles southwest to perform a variety of training maneuvers.

The left seat instructor administering the evaluation 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 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 control of the airplane and initiated the demonstration; he pitched the airplane up and entered a full aerodynamic stall with the engine power at idle. He recalled that after the airplane stalled, he pitched the airplane to “Vg” (glide airspeed, 73 knots) to recover from the stall. He stated that during the recovery, with power at idle, “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.

National Transportation Safety Board (NTSB) Performance Study

The NTSB Office of Research and Engineering performed an ADS-B data-based airplane performance study to evaluate the maneuvers and approximate airplane loads, airspeeds, and pitch/bank angles sustained during the flight. The ADS-B system broadcasts an airplane’s GPS position and other data to ground stations where it is recorded. The GPS position has an accuracy of approximately 65 ft in both the horizontal and vertical dimensions.

The study found that four steep turns were made in the final few minutes of recorded data. At 1201:30, the airplane entered a climbing left turn while slowing below 50 knots calibrated airspeed. The airplane descended 800 ft while accelerating to over 120 knots while completing a 180° left turn. This maneuver looked like earlier 180° turns; however, the minimum speed was lower than the earlier maneuvers and was below the reported stall speed.

The airplane then flew level and straight for about 30 seconds before entering a climbing left turn while losing airspeed. The airplane reached a minimum airspeed of 47 knots at 1202:36 and began descending at 1202:39. The airplane accelerated as it descended. By 1202:41, the airspeed was calculated to be 90 knots and the corrected altitude was 4,820 ft. Just after 1202:41, the descent rate suddenly increased to over 10,000 ft/min and a second later the track turned to the right, likely due to the in-flight breakup of the airplane. Figure 1 provides an overview of the final few minutes of track data and the 4 steep turns.

Figure 1. ADS-B flight path with four turns of interest notated.

The final two 180° turns observed in the flight track data were of a significantly small radius as compared to previous maneuvers. The turn at 1201:45 had an estimated radius of 280 ft and the airplane accelerated to over 100 knots true airspeed while still in the turn, resulting in a calculated bank angle of at least 70° left wing down.

The final turn started with a radius of 200 ft that tightened as the airplane accelerated. At 1202:41, the airplane’s true airspeed was 99 knots, which for a 200 ft turn would result in a bank angle of at least 75° left wing down.

The pilot reported that the right wing departed the airplane first, which would result in a right rolling moment as the left wing continued to provide lift for an undetermined short period of time. Figure 2 provides an overview of the final recorded turn, subsequent descent into the building, and wreckage disposition.

Figure 2. ADS-B flight path for final turn and the subsequent in-flight break up. Locations of select wreckage are also annotated.

Flight Instructor (Left Seat)

The flight instructor seated in the left seat, who was administering the proficiency check, survived the accident with serious injuries. According to the operator, he was employed as a flight instructor with Aviator College.

Flight Instructor (Right Seat)

The flight instructor seated in the right seat, who was undergoing the proficiency check, was fatally injured. According to an operator Employee Hiring Form, his official start date with the operator as a flight instructor was August 8, 2023 (nine days before the accident).

Airplane Information

According to FAA airworthiness records, the airplane was a Piper PA28-161, serial number 2842151, manufactured in 2002. The airplane was certificated in the normal and utility category.

The Pilot’s Operating Handbook stated that all acrobatic maneuvers, including spins, were prohibited while operating in the normal category. Turns exceeding 60° were prohibited in the normal category. The flight load factor limitations in the normal category were 3.8 g and 4.4 g for the utility category.

The airplane’s weight and balance were calculated based upon an operator-supplied basic empty weight and crew weights contained in FAA-maintained airman medical records. The fuel load and consumption were estimated based upon information submitted by the operator and ADS-B flight track data. The airplane was found to be in the normal category and within maximum weight and balance limitations at the time of the accident.

Maintenance Information

The airplane’s wing spars were subject to FAA Airworthiness Directive (AD) 2020-26-16, Wing Spar Integrity, which mandated bolt hole eddy current inspection at the 2 outboard holes for attaching the main spar lower cap on each wing.

According to the airplane’s maintenance records, the most recent 100-hour inspection was competed on June 29, 2023. The endorsement noted that FAA AD 2020-26-16 was complied with, and the factored hours were 1,199.1. The endorsement noted that no further action was required until 5,000 factored hours. The airplane had flown 87.4 hours since the last 100-hour inspection. Accounting for this additional flight time, at the time of the accident, the airplane had accumulated 1,286.5 factored hours.

The most recent annual inspection was completed on September 16, 2022. The endorsement noted that FAA AD 2020-26-16 was complied with.

On March 22, 2021, the FAA AD 2020-26-16 eddy current inspection was completed and both wings, and forward and aft spars, were marked as accepted. At this inspection, the airplane was noted to have a total time in service of 15,572.9 hours. The factored service hours for both wings were 15,405.02. The inspection was completed by S.E.A.L. Aviation LLC. The endorsement noted that during the testing no defects were found. According to the maintenance records, new wing spar bolts and nuts were installed on March 22, 2021, in accordance with the AD and Piper Aircraft Service Bulletin 1345.

The Operator

The operator was Aviator College of Aeronautical Science and Technology, based in Fort Pierce, Florida. The flight school held a Part 141 certificate.

According to the operator’s Chief Flight Instructor, they did not have a Safety Management System (SMS) or a Flight Data Monitoring (FDM) program. The operator did have an Aviation Safety Action Program (ASAP).

The operator provided 3 ASAP reports that involved the accident airplane or flight crew; all were found to be related to compliance with air traffic control instructions.

Part 141 Flight Instructor Proficiency Check

According to documentation provided by the operator, several items were to be evaluated by the left seat instructor during the check being conducted. The check was required for the right seat instructor to begin training Aviator College students.

The lesson objective was stated as: ‘Part 141 requires all flight instructors to be qualified to teach each course of training to which they are assigned, and prescribes certain knowledge and proficiency tests to be accomplished prior to being assigned to an approved training course.’

The lesson completion standard was stated as: ‘The instructor must satisfactorily accomplish a one-time proficiency test in each M/M [make and model] of aircraft (Piper PA28-161) before giving any flight instruction in the particular aircraft. The flight instructor shall meet or exceed the Commercial Pilot Airplane ACS [Airman Certification Standards].’

The proficiency check required multiple maneuvers to be completed and the examiner had the discretion to choose a selection of maneuvers within certain categories.

The left seat instructor, who was administering the evaluation, reported that the other instructor had demonstrated chandelles, lazy eights, slow flight, and aerodynamic stalls satisfactorily. The left seat instructor described that at the time of the accident he was demonstrating the “EASA” maneuver, as described in the history of flight section above. This maneuver was not a part of the operator’s formal training program.

The Operator’s Flight Operations Manual, Performance Maneuvers

The operator’s PA28-161, Flight Operations Manual (FOM), provided detailed guidance on the performance of Steep Turns. The manual stated in part:

The steep turn maneuver consists of two consecutive 360° turns in either direction (usually first to the left and then to the right), using a bank angle between 45 to 60° (45° bank angle at the Private Pilot level and 50° at the Commercial Pilot level). This will cause an overbanking tendency during which maximum turning performance is attained and relatively high load factors are imposed.

Review of archived weather radar imagery found no evidence of precipitation or convective weather along the route of flight.

Airplane Information

According to FAA airworthiness records, the airplane was a Piper PA28-161, serial number 2842151, manufactured in 2002. The airplane was certificated in the normal and utility category.

The Pilot’s Operating Handbook stated that all acrobatic maneuvers, including spins, were prohibited while operating in the normal category. Turns exceeding 60° were prohibited in the normal category. The flight load factor limitations in the normal category were 3.8 g and 4.4 g for the utility category.

The airplane’s weight and balance were calculated based upon an operator-supplied basic empty weight and crew weights contained in FAA-maintained airman medical records. The fuel load and consumption were estimated based upon information submitted by the operator and ADS-B flight track data. The airplane was found to be in the normal category and within maximum weight and balance limitations at the time of the accident.

Maintenance Information

The airplane’s wing spars were subject to FAA Airworthiness Directive (AD) 2020-26-16, Wing Spar Integrity, which mandated bolt hole eddy current inspection at the 2 outboard holes for attaching the main spar lower cap on each wing.

According to the airplane’s maintenance records, the most recent 100-hour inspection was competed on June 29, 2023. The endorsement noted that FAA AD 2020-26-16 was complied with, and the factored hours were 1,199.1. The endorsement noted that no further action was required until 5,000 factored hours. The airplane had flown 87.4 hours since the last 100-hour inspection. Accounting for this additional flight time, at the time of the accident, the airplane had accumulated 1,286.5 factored hours.

The most recent annual inspection was completed on September 16, 2022. The endorsement noted that FAA AD 2020-26-16 was complied with.

On March 22, 2021, the FAA AD 2020-26-16 eddy current inspection was completed and both wings, and forward and aft spars, were marked as accepted. At this inspection, the airplane was noted to have a total time in service of 15,572.9 hours. The factored service hours for both wings were 15,405.02. The inspection was completed by S.E.A.L. Aviation LLC. The endorsement noted that during the testing no defects were found. According to the maintenance records, new wing spar bolts and nuts were installed on March 22, 2021, in accordance with the AD and Piper Aircraft Service Bulletin 1345.

The Operator

The operator was Aviator College of Aeronautical Science and Technology, based in Fort Pierce, Florida. The flight school held a Part 141 certificate.

According to the operator’s Chief Flight Instructor, they did not have a Safety Management System (SMS) or a Flight Data Monitoring (FDM) program. The operator did have an Aviation Safety Action Program (ASAP).

The operator provided 3 ASAP reports that involved the accident airplane or flight crew; all were found to be related to compliance with air traffic control instructions.

Part 141 Flight Instructor Proficiency Check

According to documentation provided by the operator, several items were to be evaluated by the left seat instructor during the check being conducted. The check was required for the right seat instructor to begin training Aviator College students.

The lesson objective was stated as: ‘Part 141 requires all flight instructors to be qualified to teach each course of training to which they are assigned, and prescribes certain knowledge and proficiency tests to be accomplished prior to being assigned to an approved training course.’

The lesson completion standard was stated as: ‘The instructor must satisfactorily accomplish a one-time proficiency test in each M/M [make and model] of aircraft (Piper PA28-161) before giving any flight instruction in the particular aircraft. The flight instructor shall meet or exceed the Commercial Pilot Airplane ACS [Airman Certification Standards].’

The proficiency check required multiple maneuvers to be completed and the examiner had the discretion to choose a selection of maneuvers within certain categories.

The left seat instructor, who was administering the evaluation, reported that the other instructor had demonstrated chandelles, lazy eights, slow flight, and aerodynamic stalls satisfactorily. The left seat instructor described that at the time of the accident he was demonstrating the “EASA” maneuver, as described in the history of flight section above. This maneuver was not a part of the operator’s formal training program.

The Operator’s Flight Operations Manual, Performance Maneuvers

The operator’s PA28-161, Flight Operations Manual (FOM), provided detailed guidance on the performance of Steep Turns. The manual stated in part:

The steep turn maneuver consists of two consecutive 360° turns in either direction (usually first to the left and then to the right), using a bank angle between 45 to 60° (45° bank angle at the Private Pilot level and 50° at the Commercial Pilot level). This will cause an overbanking tendency during which maximum turning performance is attained and relatively high load factors are imposed.

The wreckage impacted a small aluminum-frame building that housed an RV. The airplane came to rest partially through the building and partially into the RV, with the right side fuselage low. The engine remained attached to the fuselage. Both wings and horizontal stabilator were located about 600 to 700 ft east of the fuselage in the debris area noted in Figure 3, below.

The horizontal stabilator had separated into two pieces that were found near each other in the debris field. Fragments of cockpit door were also located in this debris area along with miscellaneous items from the cockpit such as the tow bar and a pilot headset. The left and right wing both separated at the wing attachment area at the fuselage. Both ailerons were located with their respective wings. Figure 3 provides an overview of the ADS-B flight track and wreckage distribution.

Figure 3: Overview of the final 30 seconds of ADS-B flight track data and wreckage distribution.

Flight control continuity was observed within each fragmented portion of wreckage for each flight control surface. The flap selector handle in the cockpit was found in the flaps retracted position, as were the right and left flap control rods. The main spar center section box structure remained installed in the fuselage and was cut from the fuselage for further examination. The carry-through spar revealed deformation consistent with positive loading. When placed upright on a flat floor the carry-through spar section was observed to be bent upward about 5 inches on each side.

Figure 4 provides an overview of the main spar center box structure after it had been separated from the fuselage by the investigation team.

Figure 4: View of the main spar center box structure, with excerpt from Piper Maintenance Manual (lower right) showing the spar section highlighted in yellow.

There was a pronounced symmetrical upward curve of the upper and lower spar caps. The lower spar cap was intact and with the center wing box on the ground the right and left sides rested about 5 inches above the floor. The upper spar cap was buckled (s-bend) upward about 12 inches from the left side and a downward buckle and fracture of the cap about 21 inches from the right side.

National Transportation Safety Board Materials Laboratory Factual Report

The NTSB Materials Laboratory performed a metallurgical and forensic scanning electron microscopy (SEM) examination of the main spar center box structure and wing fracture areas.

Examination found that the right main spar lower cap was fractured at the outboard attachment holes for attaching the wing spar to the center wing box. The upper and lower caps showed upward deformation adjacent to the fracture and rough, matte-gray fracture features consistent with ductile overstress fracture. No evidence of any preexisting cracks or defects were observed associated with the fracture surfaces as determined by optical microscopy and subsequent SEM examinations of the fracture surfaces on the lower cap.

The left wing main spar lower cap was fractured outboard of the main spar attachment bolt holes for attaching the wing to the fuselage, and the fracture intersected the inboard two rivet holes attaching the wing lower skin and spar doublers to the lower cap. The upper cap was also fractured at a similar location just outboard of the attachment location. The lower cap was bent downward adjacent to the fracture, and the inboard end of the wing’s lower skin and spar web doublers were also deformed downward. The upper cap had rough matte gray features consistent with ductile overstress fracture. The fracture surface of the lower cap had mostly rough matte gray features, but the lower edge of the fracture had a smoother shiny appearance, features consistent with ductile overstress fracture with smearing at the compression side of a fracture with local bending. The overall deformation pattern on the left wing was consistent with a downward bending load associated with the left wing’s fracture following the upward load associated with the center wing box deformation.

Further examination found that fatigue cracks that initiated in areas of fretting damage were observed in both the right and left wing main spar lower caps. The fretting damage was located on the lower surfaces of the wing spar lower caps on the outboard side of the outboard attachment holes. Although fatigue cracks were present, they were not yet large enough to impact the strength of the spar under the accident loading conditions since none of the fractures initiated at or intersected any fatigue cracks.

The FAA Airplane Flying Handbook, Steep Turns

The FAA Airplane Flying Handbook provided guidance on the execution of several performance maneuvers, including steep turns. The handbook stated in part:

Steep Turns

Steep turns consist of single to multiple 360° and 720° turns, in either or both directions, using a bank angle between 45° and 60°. The objective of the steep turn is to develop a pilot’s skill in flight control smoothness and coordination, an awareness of the airplane’s orientation to outside references, division of attention between flight control applications, and the constant need to scan for hazards and other traffic in the area.

The chapter further outlined information regarding steep turns and the effect on load factor and design standards and limitations for general aviation airplanes.

As discussed in previous chapters, when banking an airplane for a level turn, the total lift divides into vertical and horizontal components of lift. In order to maintain altitude at a constant airspeed, the pilot increases the angle of attack (AOA) to ensure that the vertical component of lift is sufficient to maintain altitude. The pilot adds power as needed to maintain airspeed. For a steep turn, as in any level turn, the horizontal component of lift provides the necessary force to turn the airplane. Regardless of the airspeed or airplane, for a given bank angle in a level altitude turn, the same load factor will always be produced. The load factor is the vector addition of gravity and centrifugal force. When the bank becomes steep as in a level altitude 45° banked turn, the resulting load factor is 1.41. In a level altitude 60° banked turn, the resulting load factor is 2.0. To put this in perspective, with a load factor of 2.0, the effective weight of the aircraft (and its occupants) doubles. Pilots may have difficulty with orientation and movement when first experiencing these forces. Pilots should also understand that load factors increase dramatically during a level turn beyond 60° of bank. Note that the design of a standard category general aviation airplane accommodates a load factor up to 3.8. A level turn using 75° of bank exceeds that limit.

Because of higher load factors, steep turns should be performed at an airspeed that does not exceed the airplane’s design maneuvering speed (VA) or operating maneuvering speed (VO). Maximum turning performance for a given speed is accomplished when an airplane has a high angle of bank. Each airplane’s level turning performance is limited by structural and aerodynamic design, as well as available power. The airplane’s limiting load factor determines the maximum bank angle that can be maintained in level flight without exceeding the airplane’s structural limitations or stalling. As the load factor increases, so does the stalling speed. For example, if an airplane stalls in level flight at 50 knots, it will stall at 60 knots in a 45° steep turn while maintaining altitude. It will stall at 70 knots if the bank is increased to 60°. Stalling speed increases at the square root of the load factor. As the bank angle increases in level flight, the margin between stalling speed and maneuvering speed decreases. At speeds at or below VA or VO, the airplane will stall before exceeding the design load limit.

In addition to the increased load factors, the airplane will exhibit what is called “overbanking tendency” as previously discussed in Chapter 3, Basic Flight Maneuvers. In most flight maneuvers, bank angles are shallow enough that the airplane exhibits positive or neutral stability about the longitudinal axis. However, as bank angles steepen, the airplane will continue rolling in the direction of the bank unless deliberate and opposite aileron pressure is held. Pilots should also be mindful of the various left-turning tendencies, such as P-factor, which require effective rudder/aileron coordination. While performing a steep turn, a significant component of yaw is experienced as motion away from and toward the earth's surface, which may seem confusing when first experienced.

Flight Data Monitoring

The NTSB has outstanding recommendations for Part 135 operators to implement SMS and FDM programs. In 2019-2020, the NTSB published a fact sheet as part of the Most Wanted List of Transportation Safety Improvements titled, Improve the Safety of Part 135 Aircraft Flight Operations. Although the safety improvement was directed to Part 135 operators, many of the benefits are applicable to Part 141 flight schools. The safety improvement was reiterated in the NTSB Safety Issues webpage. The fact sheet stated in part:

What can be done?

We know that SMS, FDM, and CFIT programs can improve safety and prevent crashes. We currently have 21 open safety recommendations addressing the safety gap in Part 135 operations. Operators must be proactive about safety; they should not wait for regulations or an accident to move them to action. Some operators have already incorporated SMS, FDM, and CFIT programs and are seeing tremendous safety returns.

To increase use of SMS, FDM, and CFIT programs in Part 135 aircraft, the following actions should be taken:

Operators/Industry

· Implement an SMS and FDM, appropriately scaled to the size of your operation, to detect and correct unsafe deviations from company procedures before an accident occurs.

· An SMS is an effective way to establish and reinforce a positive safety culture and identify deviations from standard operating procedures so that they can be corrected.

· Collect data through an FDM over the entirety of the operation; this is the only means an operator has to consistently and proactively monitor its line operations. FDM should be a nonpunitive system.

· Use analysis tools provided by associations and the FAA’s InfoShare to identify safety trends.

· Incorporate a CFIT-avoidance training program that addresses current TAWS technologies relevant to your operational environment.

According to the autopsy report issued by the Florida Medical Examiner Department – District 19, the cause of death for the right seat instructor was blunt impact injuries of the head, torso, and extremities, and the manner of death was an accident.

Toxicology testing performed by the FAA’s Forensic Sciences Laboratory was negative for ethanol and positive for acetaminophen and salicylic acid in both blood and urine samples for the right seat instructor. The left seat instructor was not drug tested following the accident.