Re: 777 engine RPM

Date:         16 Sep 97 02:37:11 
From:         Steve Lacker <look@the.sig>
Organization: Applied Research Laboratories - The University of Texas at Austin
References:   1
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Steven Hargreaves wrote:
> Anyone have knowledge of the approx rotational speed of 777 engines
> (inner core and fans) at take-off and cruise?  I'll split the beer I
> win if the fans do <30,000 rpm.

WAY less than 30k!! I wouldn't want to be in the same county with a
60-inch diameter fan (or anything!) spinning 30K RPM unless it was
inside a lead-lined concrete scatter pit.

I don't have any "typical" numbers handy, but I can give order of
magnitudes here. The core shafts (HP turbine, compressor) of many
engines (JT8d class) turn in the mid-10,000's (ie 15k rpm). But that
isn't the *fan*. The fan (and attached LP turbine) turn much slower-
typically 5k-8k for smallish lower bypass fans like a JT8d and MUCH
slower for the big high-bypass fans like a JT9d, PW400, Trent, GE90,
etc. Even a PW2000 or CFM-56 probably runs well under 5000 rpm fan

Stephen Lacker
Applied Research Laboratories, The University of Texas at Austin
PO Box 8029, Austin TX 78713-8029