X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [206.46.252.46] (HELO vms046pub.verizon.net) by logan.com (CommuniGate Pro SMTP 5.0c2) with ESMTP id 712866 for flyrotary@lancaironline.net; Tue, 06 Sep 2005 12:10:40 -0400 Received: from verizon.net ([71.99.144.103]) by vms046.mailsrvcs.net (Sun Java System Messaging Server 6.2 HotFix 0.04 (built Dec 24 2004)) with ESMTPA id <0IME008F8KXSO4B2@vms046.mailsrvcs.net> for flyrotary@lancaironline.net; Tue, 06 Sep 2005 11:10:41 -0500 (CDT) Date: Tue, 06 Sep 2005 12:10:34 -0400 From: Finn Lassen Subject: Re: [FlyRotary] Re: Another great flying day = another day of troubleshooting In-reply-to: To: Rotary motors in aircraft Message-id: <431DBF7A.70200@verizon.net> MIME-version: 1.0 Content-type: multipart/alternative; boundary=------------010608030100080801010202 X-Accept-Language: en-us, en References: User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax; PROMO) This is a multi-part message in MIME format. --------------010608030100080801010202 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Thank you Ed, ... and David. I really got it! Finn David Staten wrote: > To lengthen the life of the filament.. prevent oxidation. > > Dave > > Finn Lassen wrote: > >> Hmm... and here I thought that vacumn was a better insulator than air ... >> Why is the air pumped out of lightbulbs? >> >> Finn >> >> rijakits wrote: >> >>> Not exactly the same, but running the direstion: >>> During WW II the first fighters didn't run pressurized ignition >>> harnesses. >>> Tales from Gruman state that a couple of test pilots encountered a >>> sudden "Ignition failure" once they reached around 36 K feet. >>> It took (supposedly:)) a coulpe of deadstick landings until one >>> pilot tried to restart the engine on the way down. The others didn't >>> bother - engine is dead because the ignition is dead, why try re-start!! >>> Anyway the man was surprised that the engine started just fine and >>> ran well too. So back up to altitude and on with the test. >>> Wouldn't you know at around 36 K "engine out again, damn!" >>> >>> Finally they caught the problem: The air seems to be a good isolator >>> - once the air got rather thin at altitude, the spark just went >>> right through the wires and grounded. After building a pressurized >>> harness for the whole ignition system - no more problems with "dead >>> ignition" - harnesses. >>> >>> Thomas J. >>> >>> ----- Original Message ----- >>> From: Ed Anderson >>> To: Rotary motors in aircraft >>> Sent: Monday, September 05, 2005 12:06 PM >>> Subject: [FlyRotary] Re: Another great flying day = another day >>> of troubleshooting >>> >>> Well, actually it is absolute pressure that the spark plug is >>> reacting to. In this example, the absolute pressure in the >>> intake is 1.234" HG higher at 10,000 with your 26 " boost than >>> at sea level with your 36" of boost.. This would contribute to >>> an increased pressure in the combustion chamber when it is >>> compressed over the sea level compression pressure. Therefore, >>> the spark plug is facing a tougher task at 10,000 than at Sea >>> level (in this example). >>> >>> Ed >>> >>> ----- Original Message ----- >>> From: David Leonard >>> To: Rotary motors in aircraft >>> >>> Sent: Monday, September 05, 2005 12:57 PM >>> Subject: [FlyRotary] Re: Another great flying day = another >>> day of troubleshooting >>> >>> Actually, Dave you had a higher pressure ratio >>> (manifold to ambient) at 10,000 feet with 26" boost >>> than at sea level with 36". At sea level the >>> pressure ratio would be 36/29.92 = 1.20. At 10,000 >>> ft ambient pressure = 20.57 " hg , so the pressure >>> ratio would be 26/20.57 = 1.26. Not much greater, >>> but it was higher by approx.1.23" Hg. (1.20 -1.26 = >>> .06 *20.57 = 1.234" Hg). >>> >>> Ed A >>> >>> Right. But what does the plug know about the ambient >>> pressure? I thought that it was just the absolute density >>> of the charge that was contributing to SAG. >>> >>> -- >>> Dave Leonard >>> Turbo Rotary RV-6 N4VY >>> http://members.aol.com/_ht_a/rotaryroster/index.html >>> http://members.aol.com/_ht_a/vp4skydoc/index.html >>> >-- > >Homepage: http://www.flyrotary.com/ > >Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ > > > --------------010608030100080801010202 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Thank you Ed, ... and David.

I really got it!

Finn

David Staten wrote:
To lengthen the life of the filament.. prevent oxidation.
 
Dave

Finn Lassen wrote:
Hmm... and here I thought that vacumn was a better insulator than air ...
Why is the air pumped out of lightbulbs?

Finn

rijakits wrote:
Not exactly the same, but running the direstion:
During WW II the first fighters didn't run pressurized ignition harnesses.
Tales from Gruman state that a couple of test pilots encountered a sudden "Ignition failure" once they reached around 36 K feet.
It took (supposedly:)) a coulpe of deadstick landings until one pilot tried to restart the engine on the way down. The others didn't bother - engine is dead because the ignition is dead, why try re-start!!
Anyway the man was surprised that the engine started just fine and ran well too. So back up to altitude and on with the test.
Wouldn't you know at around 36 K "engine out again, damn!"
 
Finally they caught the problem: The air seems to be a good isolator - once the air got rather thin at altitude, the spark just went right through the wires and grounded. After building a pressurized harness for the whole ignition system - no more problems with "dead ignition" - harnesses.
 
Thomas J.
----- Original Message -----
Sent: Monday, September 05, 2005 12:06 PM
Subject: [FlyRotary] Re: Another great flying day = another day of troubleshooting

Well, actually it is absolute pressure that the spark plug is reacting to.  In this example, the absolute pressure in the intake is 1.234" HG higher at 10,000 with your 26 " boost than at sea level with your 36" of boost..  This would contribute to an increased pressure in the combustion chamber when it is compressed over the sea level compression pressure.  Therefore, the spark plug is facing a tougher task at 10,000 than at Sea level (in this example).
 
Ed
----- Original Message -----
Sent: Monday, September 05, 2005 12:57 PM
Subject: [FlyRotary] Re: Another great flying day = another day of troubleshooting

 Actually, Dave you had a higher pressure ratio (manifold to ambient) at 10,000 feet with 26" boost than at sea level with 36".  At sea level the pressure ratio would be 36/29.92 = 1.20.  At 10,000 ft ambient pressure = 20.57 " hg , so the pressure ratio would  be 26/20.57 = 1.26.  Not much greater, but it was higher by approx.1.23" Hg. (1.20 -1.26 = .06 *20.57 = 1.234" Hg).

Ed A

Right.  But what does the plug know about the ambient pressure?  I thought that it was just the absolute density of the charge that was contributing to SAG.

--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html 
--

Homepage:  http://www.flyrotary.com/

Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/
--------------010608030100080801010202--