PA-42 Cheyenne III/IIIA
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 80; Flight Crew Total 8300; Flight Crew Type 10
Confusion; Troubleshooting
Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Flight Crew Diverted; Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Aircraft
Prior to this event; I experienced an in-flight engine failure on the right engine shortly after takeoff from ZZZ. I declared an emergency and diverted to ZZZ1. A safe; single engine landing was completed. Upon inspection by Local Maintenance X; the Main Pressure Fuel line had broke causing the failure. A new fuel line was ordered and installed by Maintenance. After a successful Leak Check and Ground Run; Maintenance signed-off the aircraft for flight. Two days later; I flew the aircraft on a Test Flight with no passengers to ensure it had no further issues. I leveled off at 6;000 FT and approximately five minutes after level off; the right engine failed again. I declared an emergency and completed a safe; single engine landing at the ZZZ1 airport.It was discovered that the same Main Pressure Fuel line had broke; causing the engine failure. On the following day; a new [fuel] line was ordered and a thorough inspection by Maintenance was completed to discover the problem. No issue was discovered and the Mechanic believed the fuel line we ordered was defective. After the new line was installed we completed another Ground Leak Check and Engine Run. Everything checked out 'okay' and Maintenance once again signed the plane off for flight. The next day; I completed an additional Ground Run Check at a 'Climb' power setting on the right engine for approximately 10-15 minutes continuous to ensure there was no issue with the right engine before takeoff. Everything checked out 'okay' and the engine ran normally. I departed ZZZ1 (no passengers) with no issues and climbed to my cruising altitude.After about 15-minutes cruising at FL240; the right engine flamed out approximately 30 miles north/northeast of the ZZZ2 airport. I completed the engine securing procedures; declared an emergency; and diverted direct to the ZZZ2 airport for an emergency landing. All procedures and checklists were complied with along with the engine securing and Single Engine Landing Emergency Checklists. ARFF was standing by and a safe; single engine landing was completed. I was able to taxi to the FBO on my own power. Upon inspection by the Local Maintenance facility; the Main Fuel Pressure line broke causing the inflight engine failure. The aircraft is remaining in ZZZ2 at the FBO until a determination of the cause of the fuel line continuing to break shortly after takeoff and a successful repair is made.
Reporter stated that currently the Piper PA-42-720 aircraft is still grounded at a Repair facility at ZZZ2 airport where he diverted into when the third flame-out occurred. No fire occurred on any of the three incidences; but pooling of fuel in the cowling was noted. The PT6A is a reverse flow turbine engine with the turbine section forward at the prop area and the engine compressor section at the firewall area. That design; he believes; was the reason no fire erupted when the stainless steel fuel lines broke approximately 1/4' of an inch just below the 'B' nut connection to the Fuel Control Unit (FCU). All three lines broke at the same location at the aft end of the engine; aft side of the Accessory Gearbox (AGB). That same Main High Pressure Fuel line is about 10' inches long and runs from the FCU to another 'B' nut connection at the Fuel Flow (F/F) Transducer; then on to the fuel manifold and engine fuel nozzles. In-flight; when the three flame-outs occurred; the engine acted as if the Condition Lever had been shut-off.Reporter stated a Vibration Analysis was brought in to run tests on the PT6A-41 engine. But as soon as they ran the engine with another fuel line; the Starter-Generator failed; later determined to be from stressed bearings at the mounting pad.  Engine mounts were replaced. More vibration tests; results still negative. The Compressor and Turbine section # 3 and # 4 bearings are suspect for cause of the vibration that most likely contributed to the fuel lines breaking. The aircraft's history noted that the engine had sustained a lightning strike just prior to the flight where his first engine flame-out occurred. The Vibration Analysis had concerns that residual magnetism in the compressor shaft or internal damage at the AGB from the lightning strike may be the issue. He does not know if bonding straps are maintained on the engine to fuselage structure.    Reporter stated he flew King Air's with essentially the same PT6A engines. The PW PT6A's have a long history of being extremely reliable. He has not heard of any similar inflight engine flamouts from other pilots caused by a broken fuel line. The PT6A-41 engines are maintained under a maintenance contract with a company that has STCs approved by the FAA allowing extended time between overhauls.
[Report narrative contained no additional information.]
Captain reports he had three separate and sequential incidences of Number 2 Engine flaming out in cruise that required single engine approaches in the same Piper PA-42 aircraft. All three inflight engine failures were due to the Main Fuel High Pressure stainless steel line breaking near the Fuel Control Unit (FCU) on the same PT 6A-41 engine.