X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 871377 for flyrotary@lancaironline.net; Sun, 11 Dec 2005 10:26:30 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.102; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id jBBFPffU000587 for ; Sun, 11 Dec 2005 10:25:41 -0500 (EST) Message-ID: <002201c5fe67$2a40bee0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Prop stall? Date: Sun, 11 Dec 2005 10:25:48 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01C5FE3D.41232690" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_001F_01C5FE3D.41232690 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Todd, My understanding is when the prop stalls it is not loaded as = heavily as when "unstalled". If that is the case, then it would seem a = stalled prop would cause a higher rpm at the same throttle setting than = in the "unstalled" state. Ed ----- Original Message -----=20 From: Todd Bartrim=20 To: Rotary motors in aircraft=20 Sent: Sunday, December 11, 2005 4:27 AM Subject: [FlyRotary] Prop stall? 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 =20 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_001F_01C5FE3D.41232690 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Todd,  My = understanding is=20 when the prop stalls it  is not loaded as heavily as when=20 "unstalled".  If that is the case, then it would seem a stalled = prop would=20 cause a higher rpm at the same throttle setting than in the "unstalled"=20 state.
 
Ed
----- Original Message -----
From:=20 Todd = Bartrim=20
Sent: Sunday, December 11, 2005 = 4:27=20 AM
Subject: [FlyRotary] Prop = stall?

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