The National Transportation Safety Board (NTSB) has cited corrosion in both engines as the probable cause in the crash of a Bombardier Challenger 604 on a Florida freeway in 2024.
The pilot and copilot were killed in the fire following the crash. The cabin attendant and the two passengers on board escaped through the baggage compartment door with minor injuries. A motorist was also slightly injured when the aircraft came down on a heavily traveled interstate during rush hour.
The 21-page NTSB report said corrosion was found in the GE CF34-3B engines’ variable geometry (VG) system. The VG system controls airflow through the high-pressure compressor (HPC) by adjusting the position of the inlet guide vanes and the first five stages of stator vanes. Lack of airflow can cause a compressor stall and loss of engine power.
As part of the accident investigation, the engines were recovered and shipped to GE for disassembly and examination under federal oversight. The examination found corrosion in both engines that obstructed airflow to the HPC, with the most significant corrosion found in the VG stage 5 area. Extensive corrosion was also found in the HPC case VG stage 5 stator vane spindle bores, along with reduced angle swing range of the VG stage 5 stator, resulting in the VG position being more open when commanded fully closed and more closed when commanded fully opened, along with slower than normal VG system response when tested with pressurized air, and VG stage 5 stator vanes unable to fully travel as specified by maintenance practice manuals.
The engine compressor cases were made of stainless steel, and corrosion was found in the HPC vane bores in each of the accident engines and along the compressor case inner diameter. Chemical analysis of the corrosion and debris collected from the compressor case and VG system hardware revealed corroded steel and elements commonly found in seawater.
At the time of the accident, the aircraft was operated by Ace Aviation Services, doing business as Hop-A-Jet.
According to FAA and maintenance records, the aircraft was acquired by the accident operator in 2020 and based at Fort Lauderdale Executive Airport (KFXE) in Florida, approximately 4 nm west of the Atlantic Ocean.
The previous owner took delivery of the airplane from the factory in 2004, and it was primarily based at Grantley Adams International Airport (KBGI) in Bridgetown, Barbados.
Previous Engine Issues
The NTSB report noted that on January 14, 2024, the jet experienced an abnormal engine start, which is known as a “hung start,” where the engine lights off but fails to accelerate to self-sustaining idle speed. It can be caused by insufficient power to the starter or starter air pressure that is 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, or fuel issues.
Maintenance personnel attempted to troubleshoot the issue by draining fuel from the engines and testing it for contamination, but none was found. The operator then consulted with the engine manufacturer. Both engine fuel filters were replaced, and visual inspection of the old filters revealed no defects. On the following day both engines started normally, and multiple functional checks were performed with no anomalies noted.
The NTSB also cited inadequate fault isolation guidance from the engine manufacturer, which prevented the identification of corrosion buildup in VG system components during troubleshooting of hung start events of both engines about one month before the accident.
Crash Details
The morning of the accident the jet launched from Naples Municipal Airport (KAPF) in Florida, destined for Ohio State University Airport (KOSU) in Columbus. The accident happened when the aircraft was returning to Florida at the end of the day. Before departure from KOSU, the aircraft was serviced with 350 gallons of fuel.
The report includes ADS-B flight tracking data and a transcript of cockpit voice recorder (CVR) communications. The flight appeared to be normal until the aircraft was maneuvering for a 5-mile final approach to Runway 23.
At 3:09 p.m. ET, the tower controller cleared the flight to land. The airplane was about 6.5 miles north of the airport at an altitude of 2,000 feet with a ground speed of 166 knots.
According to the airplane’s flight data recorder, approximately 33 seconds later the first of three master warnings were recorded, indicating a problem with oil pressure in the left engine, then the right engine. The system gave the pilots an 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 of “engine oil.”
At 3:10 p.m., when the aircraft was at approximately 1,000 feet msl and on a shallow intercept angle for final approach with a ground speed of 122 knots, the crew declared an emergency and notified ATC that it had lost both engines. ATC acknowledged the call, clearing the jet to land.
The crew replied it was not going to be able to make the runway. There were no more transmissions.
The jet came down on Interstate 75 in Naples, Florida. The highway runs north-south, putting it perpendicular to the assigned runway at KAPF.
The accident happened during a Friday afternoon rush hour, so the interstate was crowded with cars. Dashcam video provided to the NTSB shows the jet in a shallow left turn then leveling its wings before touching down in the southbound lanes.
The left landing gear touched down first in the center of the three lanes, and the right main gear touched down in the right lane. The jet rolled through the breakdown lane and the grass shoulder area then collided with a concrete sound barrier. The aircraft caught fire, sending up a large cloud of black smoke.
The cabin attendant told investigators that she recognized there was a malfunction when she saw red writing on the screens in the cockpit and overheard one of the pilots say, “we’re in an emergency,” followed by “we just lost both engines.”
The pilots told the cabin attendant to brace for impact. The cabin attendant briefed the passengers to assume the brace position and announced, “brace, brace, brace.”
After the aircraft came to a stop, the cabin filled with smoke and she could see “neon flames.” The cabin attendant said there was fire outside the over-wing exit, and she realized that the only viable exit was the baggage door. One of the passengers was already there, she said, possibly attempting to open the door. The cabin attendant instructed him to get out of her way, and she began moving objects out of the baggage compartment.
After struggling with the door, she successfully opened it. She got out of the airplane, and the passengers followed her out. The cabin attendant told investigators her training did not include operation of the baggage door, but she knew how to open it because she had helped pilots load baggage.
