Re: Engine noise question

Date:         08 Dec 96 04:12:39 
From:         falke@pweh.com ( 0 Falke_Charlie phone dist )
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> > When I flew on a United A320, I noticed this same buzz, louder than
> > inside a DC-10 and quite annoying.  Since United's A320s have IAE
> > V2500 engines, and CFM56s on both 737s and DC-8s don't exhibit this
> > same buzz, I'm assuming this is a function of the V2500's design.

Karl, Martin,
   Fan buzz is very sensitive to the speed of the fan and where you
sit in the cabin.  It's at a maximum about 30 degrees ahead of the
engines.  It doesn't necessarily increase with power.  The PW4084 and
PW4094 both buzz at around 81% to 83% N1, much less so at higher or
lower settings.  This is right about where it is at first power
reduction after takeoff.  It's actually loudest around the second
doors on either side, which is where they sit the engine specialists
in the instrumented airplanes.  (I'm told this is entirely
coincidental :-). It quiets down after you've climbed a bit.  Some
people find it annoying.  (I think it sounds cool, but I'm an
engineer)
  I had a back to back comparison of IAE vs CFM in A320's, riding in one
of each on succesive days (flight test, then Air Inter) and I found
the CFM engine noisier.  I have heard quite loud buzz in CFM powered
737's as well.  It will be interesting to see if the CFM56-7's in the
737 advanced models will buzz louder with the -7's  wide chord blades.

--
Charlie Falke                Pratt & Whitney Aircraft
System Test Team Leader      400 Main St. M.S. 121-05
203-565-9063 x1261 fax       East Hartford, Ct 06108