Originally Posted by
condor17
Was a 737-300 . I went onto 733s in '88 . From the incident when both flames put out by V heavy rain . A new procedure came in for flying in V heavy rain , eng. fan speed had to be at 55% N1 ...
When at low spd , 250-210 kts , speedbrakes out , gear down , 55% N1 ... She would not descend
Unofficial work around , was to close the throttle on one eng , 't other at 55% .. bit of sideslip . after a minute or so spool up the idle one then idle the 55%er .
Fairly quickly a new profile fan hub design was rolled out , and the centre of hub pointed rubber ' wiggler ' disappeared . With a much more rounded hub resulting with no flame out problems .
rgds condor
They also changed the shape of the 'splitter' between the core and fan streams - I don't know details (I wasn't involved - learned this from a co-worker who was involved) but the combination of spinner and splitter shape changes caused a much higher percentage of any rain/hail bypassing the core and going out the fan duct.
Lots and lots of testing went into that...