West Palm Beach, FL, USA
N63RP
BOMBARDIER INC BD-700-2A12
Post-event inspection of a GE Aviation Passport 20-19BB1A turbofan engine found light thermal distress on the outside of the engine core compartment near the top of the engine from the 10:00 to 11:00 o’clock position, aft looking forward, and localized discoloration on the inside of the core cowls in the general location of fuel nozzle No. 16 location consistent with an undercowl engine fire. This corroborates the pilot’s report of an in-flight engine fire during takeoff climb. The fuel nozzle No. 16 location appeared shiny, lacked the sooting that neighboring fuel nozzle pigtail-to-fuel manifold b-nut connections exhibited; therefore, it was considered a possible fuel leak location. The engine was removed and sent to GE for evaluation; a fuel system leak check was performed but the source/location of the fuel leak could not be identified. The fuel pressure and nitrogen check pressure used during the leak tests were well below the fuel pressure the engine experienced during the event and was determined to be insufficient to replicate the leak. A torque check of all the fuel manifold b-nut connections found four locations, all located on the left fuel manifold, which had very low torque values, less than 200 inch-pounds, when compared to the other b-nut connection locations and the required installation torque of 285 inch-pounds nominal. One of the four low torque locations was fuel nozzle No. 16 that was identified as a possible leak source during the initial examination. Detailed analysis of the fuel nozzle No. 16 pigtail-to-fuel manifold b-nut connection revealed evidence of galling and intermediate contact marks consistent with and indicative of misalignment and relative movement within the connection; none of the other low torque b-nut connection locations exhibited this type of surface distress. Since the post-event fuel system leak checks performed by GE could not induce a fuel leak, the exact location/source of the fuel leak could not be determined by testing and observations. However, the combination of low torque, misalignment between fuel nozzle No. 16 pigtail-to-fuel manifold b-nut connection, and sealing surface distress created the conditions by which there was insufficient sealing allowing fuel to leak during high engine power and high fuel pressures. No other fuel nozzle locations had this combination of factors that would have allowed a fuel leak.
On April 3, 2022, at 09:06 eastern standard time, a Bombardier Global 7500 Business Jet, registration number N63RP, powered by two General Electric (GE) Aviation Passport 20-19BB1A turbofan engines and operated by Wing Aviation Charter Services LLC, experienced a left (No. 1) engine fire during takeoff climb from the Palm Beach International Airport (PBI), West Palm Beach, Florida. After the left engine fire warning was annunciated, the pilots reduced power and leveled off at 4,000 feet above ground level (AGL) at which time the fire warning annunciation ceased. The pilots notified air traffic control (ATC) that the fire warning was intermittent, and they were going to proceed with the planned flight. A subsequent climb with the engines at high power resulted in the left engine fire warning to annunciate again. The pilots performed an in-flight turn back to PBI and made an uneventful landing with no injuries reported to the three crew members and 15 passengers on board. The incident flight was a 14 Code of Federal Regulations (CFR) Part 135 non-scheduled domestic passenger flight from PBI to Teterboro airport (TEB), Teterboro, New Jersey. Post-event engine inspection found light thermal distress on the outside of the engine core compartment near the top of the engine from the 10:00 to 11:00 o’clock position, aft looking forward, in the vicinity of the fuel manifolds and the fuel nozzles. Localized discoloration was observed on the inside of the core cowls consistent with the general location of fuel nozzle No. 16 and a thermally distressed engine air duct sleeve (Photo 1). At fuel nozzle No. 16, the fuel nozzle-to-fuel manifold b-nut connection appeared shiny and lacked the sooting that neighboring fuel nozzle-to-fuel manifold b-nut connections exhibited. Photo 1: Possible Fuel and Thermal Impingement locations Photo courtesy of GE (modified by NTSB) The engine has 18 fuel nozzles and fuel is provided to the fuel nozzles by two fuel manifolds mounted on the outside of the combustion case (Figure 1). Figure 1: Fuel Nozzle and Fuel Manifold Diagram Figure courtesy of GE (modified by NTSB) The engine was shipped to the GE Peebles Test Operations facility in Peebles, Ohio, to perform a series of leak checks, torque checks, and alignment checks. A nitrogen check, using soapy liquid at all the fuel manifold b-nut connections was conducted and no leaks were found. A torque check of all the fuel nozzle-to-fuel manifold b-nut connections found that four had very low torque values, less than 200 inch-pounds, when compared to the other b-nut connection locations and the required installation torque of 285 inch-pounds nominal. One of the four low torque locations was fuel nozzle No. 16. All the other fuel manifold b-nut connection torque values were within the expected ranged. After completing the on-engine checks, the fuel manifolds and fuel nozzles were removed and shipped to the GE failure analysis laboratory in Cincinnati, Ohio for additional component evaluation. Detailed examination of the fuel nozzle No. 16 location revealed: 1) galling on the outer diameter of the fuel manifold ferrule sealing surface consistent with the b-nut running onto the tube outer diameter (Photo 2), 2) signs of galling and grooving on the fuel manifold female ferrule inner conical sealing surface that mates with the fuel nozzle male bullnose sealing surface, and 3) elliptical and intermittent contact marks around the fuel nozzle male bullnose conical surface consistent with misalignment contact with the fuel manifold female ferrule; the wear mark was not in the same plane around the entire surface (Photo 3). According to GE, this observed female ferrule sealing surface damage is indicative of misalignment and relative movement within the connection due to high load and low cycle contact and not vibratory wear. Visual examination found no other fuel manifold b-nut connections or fuel nozzle male bullnoses exhibiting similar ferrule sealing surface damage. Photo 2: Fuel Manifold Ferrule Damage at Fuel Nozzle No. 16 Location Photo courtesy of GE (modified by NTSB) Photo 3: Elliptical Contact Pattern on the Fuel Nozzle Male Bullnose Sealing Surface Photo courtesy of GE (modified by NTSB) Several days prior to this event, on March 31, 2022, a Bombardier Global 7500 Business Jet, registration number 9H-VIG, operated by Vistajet, experienced a right (No. 2) engine fire during the takeoff climb from the King Khalid International Airport, Riyadh, Kingdom of Saudi Arabia (OERK). After the right engine fire warning annunciated, the pilots disengaged the autothrottles and retarded the right engine throttle to idle. When the right engine throttle was deduced, the fire warning annunciation ceased. With the fire warning annunciation out, the pilots incrementally increased the right throttle and the fire warning annunciated again. The pilots shutdown the right engine, performed an in-flight air turn back to OERK, and made an uneventful landing with no injuries reported. Post-landing inspection of the right engine by GE on-wing support in the Kingdom of Saudi Arabia revealed indications of an undercowl fire and potential fuel leak locations; NTSB investigation ENG22LA049. The Kingdom of Saudi Arabian Aviation Investigation Bureau (AIB) informed the NTSB of the event on April 14, 2022, and the investigation was ultimately delegated to the NTSB. Due to the similarities with an on-going NTSB investigation (ENG22LA020), a joint Powerplant Group Chair Factual Report was created to document the findings for these two events. During the investigation into the Palm Beach and Riyadh fuel manifold leak events, two additional engines were found to have fuel manifold b-nut connection leaks; those were discovered during inspections performed by Bombardier in response to the Palm Beach and Riyadh events. The two fuel manifold leak engines found by Bombardier did not show any evidence of an undercowl fire. GE performed similar leak, torque, and alignment checks on all those engines along with visual examination of the fuel nozzle and fuel manifold sealing surfaces to determine if there were common causes/anomalies for all the observed fuel manifold leaks. Additionally, GE conducted a series of acceptance test procedure engine runs, developmental engine runs, and component static rig tests to: 1) better understand the effects of fuel nozzle-to-fuel manifold pigtail misalignment, 2) gather assembly and operational loads/stresses on the fuel manifolds under a variety of installation sequence scenarios, 3) validate and develop fuel manifold and fuel nozzle installation best practices and procedures, 4) gather operational data on torque (clamp) relaxation on the fuel manifold b-nut connections, and 5) develop methods to minimize the amount of relaxation experienced in operation. Based on all the data gathered from the event engines, the test engines, and component rig tests, several cumulative factors were found to have contributed to the fuel manifold leaks. Fuel manifold pigtail and fuel nozzle dimensional variation, combined with a given assembly sequence, can create potential misalignment between fuel manifold female ferrule and fuel nozzle male bullnose sealing surfaces, resulting in high resistance in the threads, low effective clamping force, and a false (high) torque reading. This low effective clamped connection can relax/loosen during engine operation as the manifold geometry normalizes and the connection shifts. All the leaking fuel manifold b-nut connections were found on those connections with lower than expected torque values. Since no fuel leaks occurred during the developmental engine tests, and leaks could be induced and stopped with slight variations in torque during the component rig tests, GE concluded that multiple factors can be present to create a leak and they are false (low) torques due to misalignment, higher than anticipated assembly loads due to dimensional variation, and poor/distressed sealing surface condition. Several corrective actions were taken by GE and the Federal Aviation Administration to address and mitigate the risk of GE Passport 20-19BB1A engines fuel manifold leaks. GE issued service bulletins to borescope the engine compartment for signs of an undercowl fuel leak or fire damage (72-00-0141-00A-930A-D-001), and to retorque the fuel manifold b-nut connections as well as the fuel manifold-to-fuel manifold b-nut connection (72-00-0142-00A-930A-D-001); the Federal Aviation Administration followed up with Airworthiness Directive AD 2022-13-12 requiring a visual inspection of the core compartment, a retorque of the core compartment coupling nuts, a ground power assurance check, and a follow-up borescope inspection to ensure that there were no leaks before the airplane was returned to service. GE reviewed the fuel manifold and fuel nozzle installation and assembly procedures and made several changes to provide more specific guidance. The changes focused on eliminating possible ambiguities in the written procedures and to minimize any misalignments or unintended installation loads based on the results from the static rig and engine tests. In addition, feedback from the assembly mechanics were included to improve the overall effectiveness of the proposed installation and assembly changes. GE issued a “change in design” to finalize and clarify the optimum fuel nozzle and fuel manifold installation and assembly procedure using the best practices developed during testing.
An in-flight engine fire resulted from a fuel leak from fuel nozzle No. 16 pigtail-to-fuel manifold b-nut connection that contacted hot engine parts and ignited. Contributing to the manifold fuel leak was the misalignment between fuel manifold female ferrule and fuel nozzle male bullnose sealing surfaces coupled with distress of the ferrule sealing surface.
Source: NTSB Aviation Accident Database
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