X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 10 Sep 2010 15:18:12 -0400 Message-ID: X-Original-Return-Path: Received: from web57503.mail.re1.yahoo.com ([66.196.100.70] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with SMTP id 4461909 for lml@lancaironline.net; Fri, 10 Sep 2010 07:45:46 -0400 Received-SPF: none receiver=logan.com; client-ip=66.196.100.70; envelope-from=casey.gary@yahoo.com Received: (qmail 89494 invoked by uid 60001); 10 Sep 2010 11:45:10 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=UBMZ8ECuR1alfuCJT4TEipkaX9pSFnH3Euq/34vcujzO0rBMXdOnO/eG5dQ51zPZkXmMg02pncJntE3qJ/LWNEa18j1RmphKWxRGrpdzYnuk1dJsInNIHf/g/UmDfLRvlAZUK9RRUVnnItYsR5N5y9PRslIOwA1RBF4vEvmTzDg=; X-Original-Message-ID: <57777.89177.qm@web57503.mail.re1.yahoo.com> X-YMail-OSG: FnZULC4VM1lqVv_lsL5hhIdIBXIUqXCUmuNC3OhYdkaN2aU KY760D5jJZe8B01XKM42GiCKI9sNz1Wp0_NwVg89xCfW5irQYYhoIHbIKuz2 p.gYQ8AMdu3qJzB1p9g13uvAw2PckCz02SvPBcBoZS_CxVRL7RVC3LtHouYP PqUrSS68Z9RcxjXUELEmejAV0qEi7H9j8SSyDRXIk_7bm9kBKhBX1KnXPdCO lOqQI.Yd5HsdjyKenSA0Z4g-- Received: from [97.122.180.44] by web57503.mail.re1.yahoo.com via HTTP; Fri, 10 Sep 2010 04:45:09 PDT X-Mailer: YahooMailRC/470 YahooMailWebService/0.8.105.279950 References: X-Original-Date: Fri, 10 Sep 2010 04:45:09 -0700 (PDT) From: Gary Casey Subject: Re: Engine failure ATC Transcript Super Legacy Twin Turbo TSIO 580 X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1548766200-1284119109=:89177" --0-1548766200-1284119109=:89177 Content-Type: text/plain; charset=us-ascii The questions below are certainly correct. Another post said that the two turbos were plumbed to be independent from each other, each with its own wastegate. Then how was the fuel metered? One could use a separate fuel control servo on each turbo, but I doubt that it was done that way. I suspect a single servo fed both turbos, measuring the total air. That's the difference between the Continental proprietary system and the Lycoming system built by Precision Airmotive(was Bendix). The Bendix system measures air flow and the Continental system measures throttle position and engine speed, with altitude compensated versions being compensated for manifold pressure. Regardless, having one bank pressurized to a different pressure than the other makes accurate fuel metering difficult or impossible. If indeed one bank lost boost it would be very unlikely that the engine could be made to run on more than 3 cylinders at a time (and I also suspect that the report of "3,4,6" was incorrect - it mostly likely was 2,4,6 or 1,3,5. Or it would not be unlikely that the temp probes were mixed up and never detected. When I changed any part of the design I used the rigor of conventional Failure Modes and Effects Analysis (FMEA) to evaluate all possible failure modes. That would have driven me (I hope) to provide an intake manifold interconnect between engine banks. I like single turbos, partly for that reason. Gary Casey ES, not P, not even T notwithstanding Charlies' comments I don't understand exactly what happened to 3,4,6. The video says Mark tried moving the mixture both directions with no success. I'm not understanding why that didn't help...unless half the cylinders have reduced pressure and other half have higher pressure so there is not optimal mixture. Also why 3,4,6 and not 2,4,6. Was this a Lycoming? also, also, why did the plugs foul so quickly? on a Continental the turbo outputs are merged so that if you lose, e.g. one hose, you would lose pressure on all cylinders. at least then all cylinders face the same mixture situation. --0-1548766200-1284119109=:89177 Content-Type: text/html; charset=us-ascii
The questions below are certainly correct.  Another post said that the two turbos were plumbed to be independent from each other, each with its own wastegate.  Then how was the fuel metered?  One could use a separate fuel control servo on each turbo, but I doubt that it was done that way.  I suspect a single servo fed both turbos, measuring the total air.  That's the difference between the Continental proprietary system and the Lycoming system built by Precision Airmotive(was Bendix).  The Bendix system measures air flow and the Continental system measures throttle position and engine speed, with altitude compensated versions being compensated for manifold pressure.  Regardless, having one bank pressurized to a different pressure than the other makes accurate fuel metering difficult or impossible.  If indeed one bank lost boost it would be very unlikely that the engine could be made to run on more than 3 cylinders at a time (and I also suspect that the report of "3,4,6" was incorrect - it mostly likely was 2,4,6 or 1,3,5.  Or it would not be  unlikely that the temp probes were mixed up and never detected.

When I changed any part of the design I used the rigor of conventional Failure Modes and Effects Analysis (FMEA) to evaluate all possible failure modes.  That would have driven me (I hope) to provide an intake manifold interconnect between engine banks.  I like single turbos, partly for that reason.

Gary Casey
ES, not P, not even T


notwithstanding Charlies' comments I don't understand exactly what happened to 3,4,6.   The video says Mark tried moving the mixture both directions with no success.   I'm not understanding why that didn't help...unless half the cylinders have reduced pressure and other half have higher pressure so there is not optimal mixture.   Also why 3,4,6 and not 2,4,6.   Was this a Lycoming?  also, also, why did the plugs foul so quickly?

on a Continental the turbo outputs are merged so that if you lose, e.g. one hose, you would lose pressure on all cylinders.   at least then all cylinders face the same mixture situation.

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