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Totally agreed Ed,
For your information my EAA chapter had a rep from Lycon, a top Lyc engine builder on the west coast visit. He said that they had been having some trouble with their "hopped up" Lycs. They surveyed avgas locally (from San Jose to LA) and they said they were seeing WIDELY varied formulations. The fuel was OK octane wise but the amounts of TEL (lead) and other fuel additives were all over the map. He said that auto fuel was far more consistent! In fact they will void your warranty if you run LOP because they couldn't predict the results. This evaluation would be consistent with wide variance in TBS. (time before sag) Being totally honest I do not believe we will ever eliminate this totally while running leaded fuels. 100LL has a rather higher lead content than any auto fuel did. The problem is that the plugs tend to have "tracking" rather than fouling. Lead deposits on the insulator cause a lower resistance track or path to form on the surface of the insulator. We saw this a lot on 2 strokes. The thing is the coil IS firing the charge is moving along the path, there is no malfunction of the coil. The tracked charge just doesn't ignite the fuel air charge because the spark doesn't jump the gap. There have been loads of research on ways to stop the problem. There are 2 ways that worked back then, (mid-late 70s), high compression and unleaded fuel. I don't understand the chemistry changes caused by high compression, and it really isn't available to us anyway. Auto fuel provides us with the best alternative. If you run 100LL buy your plugs in bulk and change often.
Bill Jepson
-----Original Message-----
From: Ed Anderson <eanderson@carolina.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, 11 Jun 2007 9:10 am
Subject: [FlyRotary] Re: Spark Plug Cleaning
Actually, that is what I do, Bill. In fact, you probably missed my e mail which showed I could fly (changing plugs ever 25 hours) for over 300 hours before I approached the cost of the coils of the Blaster LS1 system.
But, on the other hand, my experience has been the SAG interval may vary from as little as 12 hours to as many as 30 hours. The fact that SAG tend to happen mostly in high power regimes of flight (like in take off) can cause a bit of consternation in some situations. Having had it happened on both rotors during take off it reduced my ROC to 500 fpm. Not really dangerous - unless you are facing a hill or obstruction- but not really pleasant either.
Also, the SAG can be mistaken for other difficulties - I spent weeks thinking I had an injector problem when I first encountered it.
So while (after 10 years of doing so), I can attest that changing plugs is certainly a viable alternative (given the relative cheapness of auto spark plugs), it would be nice just to be able to eliminate SAG all together.
Just my personal opinion, of course.
Ed
----- Original Message ----- From: <wrjjrs@aol.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, June 11, 2007 10:36 AM
Subject: [FlyRotary] Re: Spark Plug Cleaning
There is all this discussion about other ignitions and other methods to
keep the plugs fresh. Would I be out of line if I just suggested that
we change them more often? You can change a lot of standard plugs for
the price of most ignition upgrades. I would also like to mention that
Kawasaki did a check on various types of plug cleaning. Their
conclusion was that there was no economical way to clean plugs that
worked. They did some chemical cleans that worked, but cost more
overall than new plugs! My guess is that modern eco activism being what
it is in California I probably couldn't buy the stuff anyway.
Bill Jepson
-----Original Message-----
From: Ernest Christley <echristley@nc.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, 11 Jun 2007 6:37 am
Subject: [FlyRotary] Re: Spark Plug Cleaning
Michael LaFleur wrote:
Sure. How much do you spend building an airplane? $400 is what, 1/2% or > so?
You guys and your fancy kit airplanes...
$400 is more like 2% for some of us.
An extra $400 is keeping you from having a reliable ignition system.
$400 or a proper maintenance schedule will net the same reliability.
Put off buying those ANR headsets and rid yourself the risk of SAG >
during climbout or a go-round. We're talking real pucker factor here.
Mike LaFleur
I wouldn't pay $400 for headsets, either; but, that isn't the point.
The point is that $400 IS a lot of money, and that is a separate
question that whether it is justified or not.
Planes get expensive in the same way they get heavy...one pound at a
time...which would be such a profound statement if we were British.
System after expensive system is piled on, justified in each case by an
obscure what-happens-if scenario. Meanwhile, where we started gives us
more performance than the typical 152 most of us did our primary
training in. I believe I've read that the training fleet is one of the
safest components of the GA fleet. IMNSHO, over the lifetime of the
coils, the $400 would be better spend on an extra couple hours of
recurrency training with a good instructor.
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