Return-Path: Received: from border.rfgonline.com ([65.171.123.242] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP-TLS id 2638091 for flyrotary@lancaironline.net; Wed, 15 Oct 2003 14:31:43 -0400 Received: (qmail 10255 invoked from network); 15 Oct 2003 18:37:21 -0000 Received: from unknown (HELO EXCHANGE.rfgonline.com) (192.168.150.101) by 192.168.150.1 with SMTP; 15 Oct 2003 18:37:21 -0000 X-MimeOLE: Produced By Microsoft Exchange V6.0.6249.0 content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: RE: [FlyRotary] Re: EWP - series pumps and wacky ideas Date: Wed, 15 Oct 2003 14:31:42 -0400 Message-ID: <0B27ED95697C4D4CBC82D79E790FE5678B09FD@exchange.rfgonline.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [FlyRotary] Re: EWP - series pumps and wacky ideas Thread-Index: AcOTO0VdWBcowpuOTCu3VXFaIutaZQAALkXw From: "Robinson, Chad" To: "Rotary motors in aircraft" > > where do you want this to be triggered? > I was thinking that, aside from inrush current, the pump will draw say = 5 > amps when all is well. If there's a blockage somewhere, or the pump is > starting to fail, then the draw might go up, say to 8 or 9 amps. This = might > be a good way to spot a problem early. The other problem that comes up is if you use the pump controller. I = still don't think I plan to install two of them, one for each pump - I = still plan to consider the second pump a "boost / emergency secondary" = device. But what if the pump controller slows the device down? What if = the pump controller does this with pulse width modulation (PWM), = "pulsing" the motor instead of reducing voltage to control its speed = (this is quite common)? All of these things will cause problems with = sensing flow via current. I think the best answer is as others have responded, a real flow meter. By the way, for whoever posted the original comment, there IS a good = reason not to run two pumps at the same time all the time. The = difference, statistically speaking, is that it is possible to have a = simultaneous failure, although the chances for this are slim. But = external events (surging alternator maybe?) could have some impact too, = and having the second pump shut off could conceivably help isolate it = from faults. Taking the surging alternator case, hypothetically, and = assuming a crobwar OV module wasn't installed or is malfunctioning, one = could still disable the alternator and then turn on the second pump even = if the first was damaged. I prefer the isolation this provides, at the = expense of additional pilot workload during an emergency. Regards, Chad