Re: 777 engine RPM

Date:         16 Sep 97 02:37:11 
From:         "Michael F. Lechnar" <>
Organization: nams
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Karl Swartz wrote:
> The speed of sound varies with temperature and barometric pressure,
> but at average conditions at sea level it's about 760 mph.  The fan
> of a PW4000-series engine for a 777 has a diameter of 112 inches.
> ( Some simple math says that if
> the tips of the blades on a fan of that size are moving at 760 mph,
> the fan is turning at 2,280.9 rpm.
> Given how much less than 30,000 rpm that is, I'd say you ought to
> win a keg of beer from whomever your bet was with!

Pretty good calculating!!!  The value of 100% N1 for the various engines
on the 777 varies between 2300 and 3300 RPM.

Mike Lechnar
Aircraft Performance Engineer
"If I was speaking for Boeing, I wouldn't be doing it here."