X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [199.185.220.223] (HELO priv-edtnes27.telusplanet.net) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 871259 for flyrotary@lancaironline.net; Sun, 11 Dec 2005 04:28:36 -0500 Received-SPF: pass receiver=logan.com; client-ip=199.185.220.223; envelope-from=haywire@telus.net Received: from Endurance ([154.20.245.217]) by priv-edtnes27.telusplanet.net (InterMail vM.6.01.04.04 201-2131-118-104-20050224) with SMTP id <20051211092751.CWCY21541.priv-edtnes27.telusplanet.net@Endurance> for ; Sun, 11 Dec 2005 02:27:51 -0700 From: "Todd Bartrim" To: "'Rotary motors in aircraft'" Subject: Prop stall? Date: Sun, 11 Dec 2005 01:27:16 -0800 Message-ID: <063101c5fe35$1479b710$0101a8c0@Endurance> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0632_01C5FDF2.06567710" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook CWS, Build 9.0.2416 (9.0.2910.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0632_01C5FDF2.06567710 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Hi Ed; This talk of stalled props brings up another question. Last week when I was doing circuits, on one of the touch & goes, moments after I'd applied power, the engine suddenly revved up momentarily much the same way as when you hit a patch of ice while driving a vehicle with a heavy foot. This happened very fast so I wasn't able to check the RPM (sure wish I had a datalogger), but both my buddy & I heard/felt it. My first thought was the PSRU had slipped, but it had no accompanying mechanical noise (like broken gears) then second thought was prop stall. I held it on the ground a little longer without reducing power, but as we pulled through 90mph with no further indication of a problem ( I still had several thousand feet of runway ahead of me) I let her lift off and then went on to complete another dozen circuits with no further incidents. But afterwards we discussed it further and I recalled Dave's broken PSRU shaft, but if I recall his was a clean break without any sort of preceding slip. This just leaves a prop stall as the likely culprit, but I wouldn't expect that a prop would stall when at approx. 50mph. At the time my electronic prop governor was on auto and had been performing well and in any case the electric IVO prop is too slow to have gone full fine momentarily so I can almost discount this as being related. Any thoughts on whether this could have simply been a momentarily stalled prop? Todd Interestingly enough before I had the prop shortened, I was a Tracy Crooks and was doing a run up to get some exhaust sound readings. It was a cool morning and the engine was turning around 5800-6000. Tracy and I (as well as the sound meter) could hear the prop blade stalling and unstalling (apparently as the blade rotate different orientation with respect to the cowl and effect the airflow enough to cause it to stall and that point and then recover). You could hear a distinct "wop! wop! Wop!" sound as the prop stalled and unstalled. ------=_NextPart_000_0632_01C5FDF2.06567710 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Hi=20 Ed;

This talk of stalled props brings up another = question. Last=20 week when I was doing circuits, on one of the touch & goes, moments = after=20 I'd applied power, the engine suddenly revved up momentarily much the = same way=20 as when you hit a patch of ice while driving a vehicle with a heavy = foot. This=20 happened very fast so I wasn't able to check the RPM (sure wish I had a=20 datalogger), but both my buddy & I heard/felt it. My first thought = was the=20 PSRU had slipped, but it had no accompanying mechanical noise (like = broken=20 gears) then second thought was prop stall. I held it on the ground a = little=20 longer without reducing power, but as we pulled through 90mph with no = further=20 indication of a problem ( I still had several thousand feet of runway = ahead of=20 me) I let her lift off and then went on to complete another dozen = circuits with=20 no further incidents. But afterwards we discussed it further and I = recalled=20 Dave's broken PSRU shaft, but if I recall his was a clean break without = any sort=20 of preceding slip. This just leaves a prop stall as the likely culprit, = but I=20 wouldn't expect that a prop would stall when at approx. 50mph. At the = time my=20 electronic prop governor was on auto and had been performing well and in = any=20 case the electric IVO prop is too slow to have gone full fine = momentarily so I=20 can almost discount this as being related.

Any thoughts on whether this could have simply = been a=20 momentarily stalled prop?

Todd

Interestingly enough before I had the prop = shortened, I=20 was a Tracy Crooks and was doing a run up to get some exhaust sound=20 readings. It was a cool morning and the engine was turning = around=20 5800-6000. Tracy and I (as well as the sound meter) could hear = the prop=20 blade stalling and unstalling (apparently as the blade rotate = different=20 orientation with respect to the cowl and effect the airflow enough to = cause it=20 to stall and that point and then recover). You could hear a = distinct=20 "wop! wop! Wop!" sound as the prop stalled and unstalled.=20

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