Naples

On February 9, 2024, about 1517 eastern standard time, a Bombardier Inc CL-600-2B16, N823KD, was destroyed when it was involved in an accident near Naples, Florida. The two airline transport pilots were fatally injured. The cabin attendant and the two passengers sustained minor injuries, and one person on the ground suffered minor injury. The airplane was operated by Ace Aviation Services (doing business as Hop-A-Jet) as a Title 14 Code of Federal Regulations Part 135 on-demand passenger flight. The airplane was returning to Naples Municipal Airport (APF), Naples, Florida, from Ohio State University Airport (OSU), Columbus, Ohio, where it had flown earlier in the day. The airplane was serviced with 350 gallons of fuel before departure from OSU. Preliminary Automatic Dependent Surveillance – Broadcast (ADS-B) flight track and air traffic control (ATC) data revealed that the flight crew contacted the ATC tower at APF while on a right downwind leg of the approach to the airport and maneuvering for a 5-mile final approach to runway 23. At 1508, the tower controller cleared the flight to land. The airplane was about 6.5 miles north of APF, about 2,000 ft geometric altitude (GEO) and 166 knots groundspeed, as it turned for the base leg of the traffic pattern. A preliminary review of the data recovered from the airplane’s flight data recorder revealed that the first of three Master Warnings was recorded at 1509:33 (L ENGINE OIL PRESSURE), the second immediately following at 1509:34 (R ENGINE OIL PRESSURE), and at 1509:40 (ENGINE). The system alerted pilots with illumination of a “Master Warning” light on the glareshield, a corresponding red message on the crew alerting system page and a triple chime voice advisory (“Engine oil”). Twenty seconds later, at 1510:05, about 1,000 ft msl and 122 kts, on a shallow intercept angle for the final approach course, the crew announced, “…lost both engines… emergency… making an emergency landing” (see figure 1). The tower controller acknowledged the call and cleared the airplane to land. At 1510:12, about 900 ft and 115 knots, the crew replied, “We are cleared to land but we are not going to make the runway… ah… we have lost both engines.” There were no further transmissions from the flight crew and the ADS-B track data ended at 1510:47, directly over Interstate 75 in Naples, Florida. Dashcam video submitted to the National Transportation Safety Board captured the final seconds of the flight. The airplane descended into the camera’s view in a shallow left turn and then leveled its wings before it touched down aligned with traffic travelling the southbound lanes of Interstate 75. The left main landing gear touched down first in the center of the three lanes, and then the right main landing gear touched down in the right lane. The airplane continued through the break-down lane and into the grass shoulder area before impacting a concrete sound barrier. The airplane was obscured by dust, fire, smoke, and debris until the video ended. This information is preliminary and subject to change. After the airplane came to rest, the cabin attendant stated that she identified that the cabin and emergency exits were blocked by fire and coordinated the successful egress of her passengers and herself through the baggage compartment door in the tail section of the airplane.

Shortly after departure, the engine lost total power and the pilot was forced to ditch in open water; the occupants egressed and were subsequently rescued by a recreational vessel. Examination of the engine revealed a fracture hole near the n°2 cylinder, which was likely the result of the n°2 cylinder connecting rod fracturing in fatigue as a result of high heat and high stress associated with failure of the n°2 bearing. The fatigue fracture displayed multiple origins consistent with relatively high cyclic stress, which likely occurred as excessive clearances developed between the bearing and the crankshaft journal. The n°2 connecting rod bearing may have failed due to a material defect in the bearing itself or due to a disruption in the oil lubrication supply to the bearing/journal interface. Either situation can cause similar damage patterns to develop, including excessive heating and subsequent bearing failure.

The pilot departed on the cross-country flight with the airplane about 730 lbs over its maximum gross weight. While in cruise altitude at 27,000 ft mean sea level (msl), the pilot reported to air traffic control that he observed weather on his radar along his route and ahead of his position. The areas of weather included thunderstorms with cloud tops up to 43,000 ft msl. The controller acknowledged the weather; however, she did not provide specifics to the pilot, including the size and strength of the area of precipitation or cloud tops information, nor did she solicit or disseminate any pilot reports related to the conditions, as required. The airplane entered an area of heavy to extreme precipitation, likely a thunderstorm updraft, while in instrument meteorological conditions. Tracking information indicated that the airplane climbed about 300 ft, then entered a right, descending spiral and broke up in flight at high altitude. The recovered wreckage was found scattered along a path about 2.6 miles in length. Both wings separated, and most of the empennage was not located. The airplane was likely about 148 lbs over the maximum allowable gross weight at the time of the accident. Examination of the wreckage revealed no evidence of a pre accident malfunction or failure that would have prevented normal operation. The pilot, who owned the airplane, did not possess an instrument rating. The pilot-rated passenger in the right seat was instrument-rated but did not meet resency of experience requirements to act as pilot-in-command. Toxicology testing detected a small amount of ethanol in the pilot’s liver but not in muscle. After absorption, ethanol is uniformly distributed throughout all tissues and body fluids; therefore, the finding in one tissue but not another is most consistent with post-mortem production. Hazardous weather avoidance is ultimately the pilot’s responsibility, and, in this case, the airplane was sufficiently equipped to provide a qualified pilot with the information necessary to navigate hazardous weather; however, the controller’s failure to provide the pilot with adequate and timely weather information as required by Federal Aviation Administration Order JO 7110.65X contributed to the pilot’s inability to safely navigate the hazardous weather along his route of flight, resulting in the penetration of a thunderstorm and the resulting loss of airplane control and inflight breakup.

The commercial pilot and his wife departed New York in their turboprop airplane on a crosscountry flight to Florida. About 1 hour 40 minutes into the flight and while cruising at flight level (FL) 280, the pilot notified air traffic control (ATC) of an abnormal indication in the airplane and requested a descent to FL180. The responding controller instructed the pilot to descend to FL250 and turn left 30°, and the pilot acknowledged and complied with the instruction; he then again requested a lower altitude. Although the pilot declined emergency handling and did not specify the nature of the problem, the controller independently determined that the flight had encountered a pressurization issue and immediately coordinated with another ATC facility to clear nearby traffic. The controller then issued instructions to the pilot to descend to FL200 and change course; however, the pilot did not comply with the assignments despite acknowledging the instructions multiple times. The pilot's failure to comply with the controller's instructions, his long microphone pauses after concluding a statement over the radio, and his confusion were consistent with cognitive impairment due to hypoxia. Further, the pilot's transmissions to ATC indicated impairment within 2 minutes 30 seconds of reporting the abnormal indication, which is consistent with the Federal Aviation Administration's published time of useful consciousness/effective performance time ranges for the onset of hypoxia. Military airplanes were dispatched about 30 minutes after the pilot's final transmission to ATC to intercept and examine the airplane. The pilots of the military airplanes reported that the airplane appeared to be flying normally at FL250, that both occupants appeared to be asleep or unconscious, and that neither occupant was wearing an oxygen mask. Photographs taken from one of the military airplanes revealed that the airplane's emergency exit door was recessed into the fuselage frame, consistent with a depressurized cabin. The military airplanes escorted the airplane as it continued on a constant course and altitude until it approached Cuban airspace, at which point they discontinued their escort. Radar data indicated that the airplane continued on the same flight track until about 5 hours 48 minutes after takeoff, when it descended to impact in the Caribbean Sea north of Jamaica. The flight's duration was consistent with a departure with full fuel and normal cruise endurance. Some of the wreckage, including fuselage and engine components, was recovered from the ocean floor about 4 months after the accident. Data recovered from nonvolatile memory in the airplane's global air system controller (GASC) indicated that several fault codes associated with the cabin pressurization system were registered during the flight. These faults indicated that the overheat thermal switch (OTSW), which was associated with overheat protection, had activated, which resulted in a shutdown of the engine bleed air supply to the cabin pressurization system. Without a bleed air supply to maintain selected cabin pressure, the cabin altitude would have increased to the altitude of the outside environment over a period of about 4 minutes. The faults recorded by the GASC's nonvolatile memory and associated system alerts/warnings would have been displayed to the pilot, both as discrete system anomaly messages on the crew alerting system (CAS) and as master warning and/or master caution annunciations. A witness report indicated that the pilot was known to routinely monitor cabin altitude while flying in the airplane and in his previous pressurized airplanes. Based on his instrument scanning practices and the airplane's aural warning system, he likely would have observed any CAS message at or near its onset. Thus, the CAS messages and the associated alerts were likely the precipitating event for the pilot's call to ATC requesting a lower altitude. The pilot was likely not familiar with the physiological effects of hypoxia because he had not recently been in an altitude chamber for training, but he should have been familiar with the airplane's pressurization system emergency and oxygen mask donning procedures because he had recently attended a transition course for the accident airplane make and model that covered these procedures. However, the pressurization system training segment of the 5-day transition course comprised only about 90 minutes of about 36 total hours of training, and it is unknown if the pilot would have retained enough information to recognize the significance of the CAS messages as they appeared during the accident flight, much less recall the corresponding emergency procedures from memory. Coupled with the pilot's reported diligence in using checklists, this suggests that he would have attempted a physical review of the emergency procedures outlined in the Pilot's Operating Handbook (POH). A review of the 656-page POH for the airplane found that only one of the four emergency checklist procedures that corresponded to pressurization system-related CAS messages included a step to don an oxygen mask, and it was only a suggestion, not a mandatory step. The combined lack of emergency guidance to immediately don an oxygen mask and the rapid increase in the cabin altitude significantly increased the risk of hypoxia, a condition resistant to self-diagnosis, especially for a person who has not recently experienced its effects in a controlled environment such as an altitude chamber. Additionally, once the pilot reported the problem indication to ATC, he requested a descent to FL180 instead of 10,000 ft as prescribed by the POH. In a second transmission, he accepted FL250 and declined priority handling. These two separate errors were either early signs of cognitive dysfunction due to hypoxia or indications that the pilot did not interpret the CAS messages as a matter related to the pressurization system. Although the cabin bleed-down rate was 4 minutes, the pilot showed evidence of deteriorating cognitive abilities about 2 minutes 30 seconds after he initially reported the problem to ATC. Ultimately, the pilot had less than 4 minutes to detect the pressurization system failure CAS messages, report the problem to ATC, locate the proper procedures in a voluminous POH, and complete each procedure, all while suffering from an insidious and mentally impairing condition that decreased his cognitive performance over time. Following the accident, the airplane manufacturer revised the emergency procedures for newly manufactured airplanes to require flight crews to don their oxygen masks as the first checklist item in each of the relevant emergency checklists. Further, the manufacturer has stated that it plans to issue the same revisions for previous models in 2017. The airplane manufacturer previously documented numerous OTSW replacements that occurred between 2008 and after the date of the accident. Many of these units were removed after the GASC systems in their respective airplanes generated fault codes that showed an overheat of the bleed air system. Each of the OTSWs that were tested at the manufacturer's facility showed results that were consistent with normal operating units. Additionally, the OTSW from the accident airplane passed several of the manufacturer's functional tests despite the presence of internal corrosion from sea water. Further investigation determined that the pressurization system design forced the GASC to unnecessarily discontinue the flow of bleed air into the cabin if the bleed air temperature exceeded an initial threshold and did not subsequently fall below a secondary threshold within 30 seconds. According to the airplane manufacturer, the purpose of this design was to protect the structural integrity of the airplane, the system, and the passengers in case of overheat detection. As a result of this accident and the ensuing investigation, the manufacturer made changes to the programming of the GASC and to the airplane's wiring that are designed to reduce the potential for the GASC to shut off the flow of bleed air into the cabin and to maximize the bleed availability. Contrary to its normal position for flight, the cockpit oxygen switch was found in the "off" position, which prevents oxygen from flowing to the oxygen masks. A witness's description of the pilot's before starting engine procedure during a previous flight showed that he may not have precisely complied with the published procedure for turning on the oxygen switch and testing the oxygen masks. However, as the pilot reportedly was diligent in completing preflight inspections and checklists, the investigation could not determine why the cockpit oxygen switch was turned off. Further, because the oxygen masks were not observed on either occupant, the position of the oxygen switch would not have made a difference in this accident.

The accident airplane was on an instrument landing system (ILS) approach to land, when witnesses reported seeing it spinning in a nose down, near vertical attitude before it collided with the ground. The accident site was about 3 miles from the approach end of the intended runway. A review of radar data disclosed that the private pilot had difficulty maintaining altitude and airspeed while on final approach, with significant excursions above and below the glidepath, as well as large variations in airspeed. Interviews with other pilots in the area just prior to and after the accident revealed that icing conditions existed in clouds near the airport, although first responders to the accident site indicated that there was no ice on the airplane. Post accident inspection of the airplane, its engine and flight navigation systems, discovered no evidence of preimpact anomalies. An analysis of the airplane's navigation system's light bulbs, suggests that the pilot had selected the GPS mode for the initial approach, but had not switched to the proper instrument approach mode to allow the autopilot to lock onto the ILS.

An annual inspection had been completed on the airplane the same day, and on its first flight after the annual inspection, as the airplane was departing from runway 05, at Naples Municipal Airport, witnesses said the engine ceased operating. They also said that the propeller was rotating either slowly or had stopped, and they then observed the airplane enter a steep turn, followed by an abrupt and uncontrolled nose-low descent and subsequent impact with the ground. The airplane came to rest in a nose-low, near vertical position, suspended at its tail section by a fence and some trees along the eastern perimeter of the airport. It had incurred substantial damage and the pilot and two passengers who were onboard the airplane were fatally injured. Postaccident examination of the airframe, flight controls and the engine did not reveal any mechanical failure or malfunction. The flaps were found to have been set to 10 degrees, and the propeller showed little or no evidence of rotation at impact. The FAA Toxicology Laboratory, Oklahoma City, Oklahoma, performed toxicological studies on specimens obtained from the pilot and the results showed that diphenhydramine was found to be present in urine, and 0.139 (ug/ml, ug/g) diphenhydramine was detected in blood. Diphenhydramine, commonly known by the trade name Benadryl, is an over-the-counter antihistamine with sedative side effects, and is commonly used to treat allergy symptoms. Published research (Weiler et. al. Effects of Fexofenadine, Diphenhydramine, and Alcohol on Driving Performance. Annals of Internal Medicine 2000; 132:354-363), has noted the effect of a maximal over the counter dose of diphenhydramine to be worse than the effect of a 0.10% blood alcohol level on certain measures of simulated driving performance. The level of diphenydramine in the blood of the pilot was consistent with recent use of more than a typical maximum single over-the-counter dose of the medication.

On final approach to Walker's Cay Airfield, the aircraft was too low and struck the ground few metres short of runway threshold. Out of control, it rolled to the right when the right wing collided with a tree and was torn off. The aircraft rolled for another 100 metres before coming to rest, bursting into flames. All five occupants were injured and the aircraft was destroyed.

The pilot was executing an ASR approach to runway 32 and 9 seconds after the approach controller advised the pilot that the flight was over the missed approach point, the pilot advised the controller that the airport was in sight and he would be circling to land. The controller acknowledged this and witnesses observed the airplane flying northwesterly west of runway 32 about 150-200 feet above ground level. They then observed the airplane enter a left bank between 60-80 degrees and the airplane pitched nose down and collided with trees then a fence and the ground. There was a small post crash fire which was extinguished by the fire department. Examination of the airframe revealed no evidence of preimpact failure or malfunction of the flight controls. The engine was removed and placed on a test bench and after replacement of several components which were impact damaged, the engine started and operated normally. The passenger was seated in the furthest aft right seat and the lap belt attach point on the right side of this seat failed due to overload.

As the aircraft (N21ST) was en route on a flight from Key West to Naples, FL, the pilot of another aircraft saw a 'fireball' in the vicinity of where N21ST subsequently crashed. When N21ST did not arrive, a search was initiated. The wreckage was found the next day at 1704 est, in the Everglades National Park, near Flamingo, FL. During impact, the main wreckage was buried in 30 feet of mud. The left outboard wing section (from just outboard of the engine nacelle to the wing tip) was found approximately 1 mile from the main wreckage. An exam revealed the wing had failed where the nacelle fuel tank and the aux fuel tank boost pumps were mounted. No exhaust system failure or leakage from the fuel tanks was found in the area of the fire. The greatest fire damage was at a point where the left nacelle fuel tank boost pump was mounted and aft from there to where the rear wing spar had burned thru. The electrical fuel boost pumps were not recovered after the accident. The ignition source for the fire was not determined. All three occupants were killed.

While in cruise flight, the pilot noted that the left engine began losing power and oil pressure. He stated that he then shut down the engine and feathered the propeller. He declared an emergency and descended to land. While on final approach, he lowered the landing gear and selected full flaps to slow the aircraft. He stated the airspeed decayed and the aircraft began to roll and yaw to the left. Subsequently, it contacted the ground in a left wing low attitude, then partially cartwheeled before coming to rest. A post accident examination of the left engine revealed that a turbocharger oil seal had deteriorated & failed, allowing oil to escape through the turbocharger exhaust. There was evidence of the beginning of progressive failure of the turbocharger. Also, there were indications that the left propeller was not fully feathered and that it was windmilling at impact. The pilot believed that he may have moved the left prop control out of the feather position by mistake. Both occupants were slightly injured.