Re: Noises on some new planes (like ATR and A320)

Date:         13 Dec 96 04:26:03 
From: ( 0 Falke_Charlie phone dist )
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> Hi, I recently posted a message mostly about the A320 in and
> asked if anyone knew what the loud dentist's drill type noises on the A320

  What you're hearing is an electrically driven hydraulic pump.
"Dentist drill" is the most apt description I've heard of this sound. :-)
If you need hydraulics, but the APU or engines aren't running, but you
do have ground electrical power, you can run an electric pump.
  It is typical for airliners to have these, but they won't
necessarily be running at any given time if the other pumps are

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