CHOKING CONDITION REACHED IN PIPELINE???

viinaa

Block: B1       Model: PIPE
  *   WARNING
      CHOKING CONDITION REACHED IN PIPELINE.
      CURRENT LENGTH= 4.921260D+01 FT  TOTAL LENGTH= 4.921260D+01 FT
      PRES= 1.497849D+01 PSIA  TEMP= 5.720000D+02 F
      MACH #= 1.950945D+02
请教各位了，这是怎么回事啊??一直改不好