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