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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
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