N823KD – BOMBARDIER INC CL-600-2B16 – 2024-02-09 NTSB Accident Report

HISTORY OF FLIGHTOn February 9, 2024, about 1511 eastern standard time, a Bombardier CL-600-2B16 airplane, 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 a minor injury. The airplane was operated by Ace Aviation Services (doing business as HopAJet) 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.

ADS-B flight track data and downloaded cockpit voice recorder (CVR) communications revealed that the flight crew contacted the APF air traffic control tower while on a right downwind leg of the approach to the airport and maneuvering for a 5-mile final approach to runway 23. About 1509, the tower controller cleared the flight to land. The airplane was about 6.5 miles north of APF, about 2,000 ft geometric altitude, and 166 kts ground speed, as it turned onto final approach for runway 23.

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), with the second immediately following at 1509:34 (R ENGINE OIL PRESSURE), and the third at 1509:40 (ENGINE). These warnings were annunciated by illumination of a “Master Warning” light on the glareshield, a corresponding red message on the EICAS, and a triplechime voice advisory (“Engine oil”).

Twenty-three seconds later, at 1510:03, about 1,000 ft pressure altitude 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 transmission and cleared the airplane to land. At 1510:12, about 900 ft and 115 kts, the crew replied, “eh we’re clear to land but we’re not gonna make the runway uh we’ve lost both engines.”

Figure 1. ADS-B ground track (blue dots) with annotations of specific events during the approach, including time and the airplane’s geometric altitude and ground speed (source: FAA).

There were no further transmissions from the flight crew, and the ADS-B track data ended at 1510:47, which was the time the airplane touched down on Interstate 75 in Naples, Florida.

Dashcam video from a vehicle driving in a southerly direction on Interstate 75 captured the final seconds of the flight. The airplane descended into the camera’s view while in a shallow left turn and then aligned with traffic travelling in 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 to the right, through the breakdown lane and down a slight embankment, then struck a non-frangible highway sign, causing it to veer further right and impact a concrete sound barrier wall. The airplane was then obscured by dust, fire, smoke, and debris until the video ended.

After the airplane came to rest, the cabin and emergency exits were blocked by fire and the cabin attendant coordinated the successful egress of her passengers and herself through the baggage compartment door in the tail section of the airplane. AIRCRAFT INFORMATIONAccording to FAA and maintenance records, the airplane was manufactured in 2004 and was powered by two GE CF34-3B turbofan engines. It was operated by the previous owner from 2005 to 2020, during which time it was primarily based at Grantley Adams International Airport (BGI), Bridgetown, Barbados.

The airplane was registered to the accident operator on May 21, 2020. It was then transferred to the accident operator’s FAA Part 135 certificate on June 3, 2021. At that time, the airplane and engines had accumulated about 6,939 hours since new (TSN) and 2,653 cycles since new (CSN). When the airplane departed OSU on the day of the accident, it had accumulated about 9,761 hours TSN and 4,444 CSN. During its duration with the accident operator, the airplane was primarily based at Fort Lauderdale Executive Airport (FXE), Fort Lauderdale, Florida, about 4 nautical miles west of the shoreline of the Atlantic Ocean.

The airplane and engines were maintained under the operator’s FAA approved Continued Airworthiness Maintenance Program, which was established in accordance with Bombardier’s CL-604 Time Limits/Maintenance Checks Manual and GE’s service manual (SM) SEI-780. The accident engines were maintained and inspected on an “On-Condition” basis. (“On-Condition” refers to the corrective action required when testing or inspection finds an indication of a potential problem.)

Previous Hung Start Event

On January 15, 2024, (25 days before the accident), pilots reported intermittent hung starts on both engines while preparing for taxi. (A “hung start” is identified by light-off followed by abnormally slow acceleration and rotor speed [rpm] stabilization below idle. Hung starts may result from a variety of conditions, such as starter air pressure too low to accelerate the engine to a self-sustaining speed, premature starter deactivation, a poorly performing or damaged compressor, incorrect scheduling of bleeds or stator vane position, and fuel issues.) As part of the troubleshooting, fuel was drained from the engines and tested for contamination; none was found.

The operator, in consultation with the engine manufacturer, spent several days troubleshooting the engines. Both engine fuel filters were replaced, and visual inspection of the old filters revealed no defects. On the following day (January 16, 2024), both engines started normally, and multiple functional checks were performed with no anomalies noted.

The operator used GE SM SEI-780 72-00-00 (dated February 1, 2022 and titled “Fault Isolation 07 Hung Start or Slow Start”) to troubleshoot the engine. The troubleshooting fault isolation logic flowchart had 27 main logic blocks requiring a “YES” or “NO” response. Main logic block 21 referenced MP 68 to pressure check the VG system. The MP 68 pressure test was one of the last items in the troubleshooting tree.

During the troubleshooting of the hung start events, MP 68 was not performed because the criteria of the flowchart were met to discontinue the testing (that is, the engines started and no anomalies were identified). With the concurrence of the engine manufacturer, the airplane was returned to service and both engines started and operated without issues for 33 flights over the next 25 days until the accident.

Engine Trend Monitoring

The operator participated in an engine trend monitoring program managed by the engine manufacturer. Certain engine parameters (such as N1 and N2 speeds, vibration levels, and oil temperature and pressure) and ambient conditions (such as airspeed and altitude) were collected and recorded for every flight, which the engine manufacturer analyzed to calculate takeoff exhaust gas temperature hot day margin and to monitor shifts in engine performance. For the CF34-3B task-oriented “On-Condition” maintenance program, Service Bulletin (SB) 71-1000 R01 directed the download and calculation of engine performance every 50 flight cycles for early detection of engine deterioration. The engine manufacturer did not issue any notices to the operator regarding trend monitoring data before or after the January 2024 hung starts on the accident engines. AIRPORT INFORMATIONAccording to FAA and maintenance records, the airplane was manufactured in 2004 and was powered by two GE CF34-3B turbofan engines. It was operated by the previous owner from 2005 to 2020, during which time it was primarily based at Grantley Adams International Airport (BGI), Bridgetown, Barbados.

The airplane was registered to the accident operator on May 21, 2020. It was then transferred to the accident operator’s FAA Part 135 certificate on June 3, 2021. At that time, the airplane and engines had accumulated about 6,939 hours since new (TSN) and 2,653 cycles since new (CSN). When the airplane departed OSU on the day of the accident, it had accumulated about 9,761 hours TSN and 4,444 CSN. During its duration with the accident operator, the airplane was primarily based at Fort Lauderdale Executive Airport (FXE), Fort Lauderdale, Florida, about 4 nautical miles west of the shoreline of the Atlantic Ocean.

The airplane and engines were maintained under the operator’s FAA approved Continued Airworthiness Maintenance Program, which was established in accordance with Bombardier’s CL-604 Time Limits/Maintenance Checks Manual and GE’s service manual (SM) SEI-780. The accident engines were maintained and inspected on an “On-Condition” basis. (“On-Condition” refers to the corrective action required when testing or inspection finds an indication of a potential problem.)

Previous Hung Start Event

On January 15, 2024, (25 days before the accident), pilots reported intermittent hung starts on both engines while preparing for taxi. (A “hung start” is identified by light-off followed by abnormally slow acceleration and rotor speed [rpm] stabilization below idle. Hung starts may result from a variety of conditions, such as starter air pressure too low to accelerate the engine to a self-sustaining speed, premature starter deactivation, a poorly performing or damaged compressor, incorrect scheduling of bleeds or stator vane position, and fuel issues.) As part of the troubleshooting, fuel was drained from the engines and tested for contamination; none was found.

The operator, in consultation with the engine manufacturer, spent several days troubleshooting the engines. Both engine fuel filters were replaced, and visual inspection of the old filters revea...