X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.2.7) with ESMTP id 3111945 for flyrotary@lancaironline.net; Wed, 03 Sep 2008 00:51:27 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.40; envelope-from=alventures@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao106.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20080903045051.GGNE8615.fed1rmmtao106.cox.net@fed1rmimpo03.cox.net> for ; Wed, 3 Sep 2008 00:50:51 -0400 Received: from BigAl ([72.192.137.74]) by fed1rmimpo03.cox.net with bizsmtp id A4qq1a00G1cVYgg044qqg3; Wed, 03 Sep 2008 00:50:50 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: N4VY finally in paint - turbo failure Date: Tue, 2 Sep 2008 21:50:53 -0800 Message-ID: <000001c90d89$073c4200$6401a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C90D45.F9190200" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3350 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C90D45.F9190200 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable You go, Dave!! Lookin' good. (Hum-m-m; navy blue - what a = surprise:-)). No definite proof, but I am quite sure that it was due to excessive = exhaust gas temps eventually melting away part of the inconel turbine blade and making the turbine unbalanced. I mostly flew around at peak EGT but now = I will be more careful about keeping the EGT less than 1600. =20 =20 The melting point of inconel is up around 2500F. Could the exhaust gas = into the turbine ever get that high? Peak EGT I see 2" from the port is = about 1725F. Do you measure the T.I.T.? =20 Another thought - it may be that at that temp the stress in the blades = could cause a bit of visco-elastic creep over time which could put things out = of balance. (In a previous life I did a fair amount of finite element, visco-elastic stress analysis of high temperature metals.) =20 Al ------=_NextPart_000_0001_01C90D45.F9190200 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

You go, Dave!!  Lookin’ good.  (Hum-m-m; navy blue = – what a surpriseJ).


No definite proof, but I am quite sure that it was due to excessive = exhaust gas temps eventually melting away part of the inconel turbine blade and = making the turbine unbalanced. I mostly flew around at peak EGT but now I will be = more careful about keeping the EGT less than 1600. 

 

The melting point of inconel is = up around 2500F.  Could the exhaust gas into the turbine ever get that high?  Peak EGT I see 2” from the port is about 1725F.  = Do you measure the T.I.T.?

 

Another thought – it may be = that at that temp the stress in the blades could cause a bit of visco-elastic = creep over time which could put things out of balance.  (In a previous = life I did a fair amount of finite element, visco-elastic stress analysis of = high temperature metals.)

 

Al

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