Loma,. .I did mention ambient conditions as affecting compressor stall. What was not mentioned was Surge bleed valaves and VIGV's!. .. .We have had center engines on B727 surging that when installed in the #1 or #3 positions worked fine.. . <img border="0" title="" alt="[Smile]" src="smile.gif" /> <img border="0" title="" alt="[Smile]" src="smile.gif" />