What was found
NR 2 ENG HAD MULTIPLE COMPRESSOR STALLS, AUTO IGNITION CAME ON. COMPRESSOR STALL OCCURRED AT TOP OF DESCENT. *S/D* ENGINE DISASSEMBLY INVESTIGATION FOUND THE CAUSE WAS A FAILED HPC STAGE 3 LEVER ARM. THE MANUFACTURER WILL PUBLISH SERVICE BULLETIN 72-0334 IN JANUARY 1999 TO REPLACE THE VSV LEVER ARMS WITH AN IMPROVED DESIGN. UA WILL PROTOTYPE THE MODIFICATION WITH THE MANUFACTURER'S ASSISTANCE AND SUBSEQUENTLY MODIFY ALL ENGINES.