X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from willowsprings.uwyo.edu ([129.72.10.31] verified) by logan.com (CommuniGate Pro SMTP 5.4c2) with ESMTPS id 4912880 for flyrotary@lancaironline.net; Sun, 20 Mar 2011 18:44:38 -0400 Received-SPF: none receiver=logan.com; client-ip=129.72.10.31; envelope-from=SBoese@uwyo.edu Received: from ponyexpress-ht2.uwyo.edu (ponyexpress-ht2.uwyo.edu [10.84.60.209]) by willowsprings.uwyo.edu (8.14.4/8.14.4) with ESMTP id p2KMi11k028410 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL) for ; Sun, 20 Mar 2011 16:44:01 -0600 (MDT) (envelope-from SBoese@uwyo.edu) Received: from ponyexpress-mb5.uwyo.edu ([fe80::9813:248c:2d68:a28b]) by ponyexpress-ht2 ([10.84.60.209]) with mapi; Sun, 20 Mar 2011 16:44:01 -0600 From: "Steven W. Boese" To: Rotary motors in aircraft Date: Sun, 20 Mar 2011 16:43:48 -0600 Subject: RE: [FlyRotary] Re: Forced Landing. Thread-Topic: [FlyRotary] Re: Forced Landing. Thread-Index: AcvnSew2q6XtIK3cTxmEr+y/nuS2jAAAapcA Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_E1AA3B1AF41D8049B1E3FBD5E225626008892DF90Dponyexpressmb_" MIME-Version: 1.0 --_000_E1AA3B1AF41D8049B1E3FBD5E225626008892DF90Dponyexpressmb_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Bobby, You are to be commended for getting down safely and for proceeding with cau= tion afterward. I did some exhaust back pressure tests with my engine stand which is a NA 1= 3B. Increasing the exhaust back pressure was accomplished by partially blo= cking the outlet. An increase in back pressure from 23" to 34" of Hg resul= ted in about a 20% decrease in HP. The thing that was interesting is how s= mall the outlet was when the HP decreased by that 20%. I didn't measure it= , but it was less than one square inch. I would expect that blocking off m= ore of that small remaining area would have had a dramatic effect. I can t= est the effect of more completely blocking off the outlet with the engine s= tand if it would be of interest to you. It will take something more substa= ntial than a banana to do the job, though ;>) During an extended below zero cold spell here, I had a friend who had his m= uffler completely fill with ice because of driving to work and back just a = short distance. After the muffler was completely blocked, the engine would= start, run for a second or two, and the die. He had the car towed to the = dealership and warming it up in the heated repair shop fixed the problem. Steve From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Bobby J. Hughes Sent: Sunday, March 20, 2011 5:03 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Forced Landing. It's supercharged. My EGT's never get over 1540F. Most of the time they run= in the 1400's. I am also not 100% convinced the muffler was to blame. But = it seems to fit the symptoms. I can't confirm the muffler was blocked after= landing while trying to taxi. One theory is the exhaust pressure was enoug= h to keep all the little pieces in place until after shutdown. Then towing = the plane shook everything loose. Wonder if I could talk Mark S. into stick= ing a banana in the tail pipe on a full power ground run to duplicate the p= roblem? This is my second HP-2 muffler in about 100 hours of engine time. I= t may have 25 hours of flight time. The first one was inside the cowl and a= ngled down and back. It lost all the mesh and cone material. The angle may = have helped some of the loose material exit the muffler. But it's all specu= lation. Bobby --_000_E1AA3B1AF41D8049B1E3FBD5E225626008892DF90Dponyexpressmb_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Bobby,

 

You are to be commended for getting= down safely and for proceeding with caution afterward.

 

I did some exhaust back pressur= e tests with my engine stand which is a NA 13B.  Increasing the exhaus= t back pressure was accomplished by partially blocking the outlet.  An= increase in back pressure from 23” to 34” of Hg resulted in ab= out a 20% decrease in HP.  The thing that was interesting is how small= the outlet was when the HP decreased by that 20%.  I didn’t mea= sure it, but it was less than one square inch.  I would expect that bl= ocking off more of that small remaining area would have had a dramatic effe= ct.  I can test the effect of more completely blocking off the outlet = with the engine stand if it would be of interest to you.  It will take= something more substantial than a banana to do the job, though  ;>= ) 

 

D= uring an extended below zero cold spell here, I had a friend who had his mu= ffler completely fill with ice because of driving to work and back just a s= hort distance.  After the muffler was completely blocked, the engine w= ould start, run for a second or two, and the die.  He had the car towe= d to the dealership and warming it up in the heated repair shop fixed the p= roblem.

 

Stev= e

 

  &nb= sp;  

 = ;

From: Rotary motors in a= ircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bobby J. H= ughes
Sent: Sunday, March 20, 2011 5:03 PM
To: Rotary m= otors in aircraft
Subject: [FlyRotary] Re: Forced Landing. <= /o:p>

 

It’s supercharged. My EGT’s never get over 15= 40F. Most of the time they run in the 1400’s. I am also not 100% conv= inced the muffler was to blame. But it seems to fit the symptoms. I canR= 17;t confirm the muffler was blocked after landing while trying to taxi. On= e theory is the exhaust pressure was enough to keep all the little pieces i= n place until after shutdown. Then towing the plane shook everything loose.= Wonder if I could talk Mark S. into sticking a banana in the tail pipe on = a full power ground run to duplicate the problem? This is my second HP-2 mu= ffler in about 100 hours of engine time. It may have 25 hours of flight tim= e. The first one was inside the cowl and angled down and back. It lost all = the mesh and cone material. The angle may have helped some of the loose mat= erial exit the muffler. But it’s all speculation. <= /p>

 

= Bobby

 

= --_000_E1AA3B1AF41D8049B1E3FBD5E225626008892DF90Dponyexpressmb_--