Yes, that’s how spark plugs should look. Usually there are more lead deposits though. Peter’s plugs don’t look good to me.
If you only do high power flights, then you probably never fly above FL080. Not much power left in a NA aircraft at FL150+.
Hmmm, my spark plugs never looked anything like that.
I only do high power flights
That’s probably why. I fly peak EGT all the time in cruise and in descent.
Peter wrote:
Did you also haveglazed cylinders
oily plugs
oily/sooty exhaust pipe
anything in oil analysis
oil on the belly
Glazed cylinders: don’t know
Oily plugs: very much so, and for a long time – even when the engine was using only around 0.1qt/hr. The engines on the twincom are canted inwards, so there is a tendency for the lower plugs on the inboard cylinders to foul. Fitting fine wire plugs masks the problem 100%.
Oily/sooty exhaust: not really
Anything in oil analysis: absolutely nothing
Oil on the belly: loads
I am pretty convinced that in my case the predominant mechanism was oil being blown out of the breather.
Once there is blow-by, I am not sure that high power running makes any difference, and can imagine that it just makes things worse as there are some higher temperatures and pressures. I would be interested to learn if others have any info on this.
Cheshunt wrote:
Now a do a oil consumption log!
Years ago the UK CAA used to insist on this for engines run beyond TBO “on condition”. I ran an engine to about 2600hrs and got into the habit of logging oil levels and decided it was a useful thing to do.
Alan_South wrote:
Once there is blow-by, I am not sure that high power running makes any difference, and can imagine that it just makes things worse as there are some higher temperatures and pressures. I would be interested to learn if others have any info on this.
The piston ring groves in the piston are wider than the rings so that under pressure, the gases expand behind the ring and press the ring onto the sleeve. This is called “dynamic compression” and decides about blow-by and actual compression. What we measure is “static compression” which is kind of meaningless but we’re not going to change our 1940s habits, are we?
The higher the ICP, the better the dynamic compression which corresponds to high power flight producing less blow-by than low power power flight.
Peter wrote:
Hmmm, my spark plugs never looked anything like that.I only do high power flights
That’s probably why. I fly peak EGT all the time in cruise and in descent.
So do I
Prior to the oil consumption going catastrophic, I’d been planning on a top overhaul in January 2016. I’d definitely sensed that the engine was telling me something, but had hoped to avoid work in the summer months. Apart from anything else, many engine guys were on holiday.
Luckily, I had the extremely good fortune to be able to borrow a friend’s twincom for a trip that I’d planned – and this one was turbocharged. His SOP was to run at considerably higher power and burn about 15litres/hr more (across the two engines) than I would normally do. In my few days with that aircraft, I really got the sense that the engines were “cleaner” than mine and were certainly allowing very high oil levels to be maintained without breathing out oil.
As a result of all this, I just wonder if my chosen approach of NA engines run at relatively low power has the downside of gumming and glazing? I’m not too worried as the fuel savings more than make up for it.
I guess the difference in my operating experience is that my engine has always run perfectly (except the icing incidents 
) and continues to run perfectly now. It is just using more oil.
But I have had multiple occassions with very oily plugs, which then went away, so I remain hopeful that this might go away too. I will more or less know tomorrow.
My operating pattern has been largely low level flights, a short full power climb and cruise at 65% power (and I am sure the engine remains clean with this flight profile) with the occassional high altitude flight. It is probably no coincidence that the present issue started after I did the Swedish trip (up to FL210) immediately followed by the Slovenia/Croatia/Greece/Corsica trip (also up to FL210).
Another thing is that if you could “bung up” an engine with just a few high altitude flights, we should be hearing more about this. Maybe not from Europe (where this sort of activity in NA aircraft is going to be very low) but from the USA. Even allowing for the fact that most pilots won’t discuss negative-anything about their aircraft (this is a major factor which frustrates most “research” in GA) I am sure we would hear more about this effect if it was triggered so easily.
Time to trade it in on a TBM Peter. You know you want to. 
Peter wrote:
I guess the difference in my operating experience is that my engine has always run perfectly
To be clear, the engine that has just been top overhauled was also running perfectly – but using too much oil. I did my MEP/IR checkride on a hot day this summer and was getting the right SE climb performance at full power on that engine.
time to trade it in on a TBM Peter. You know you want to
You are setting up a syndicate at EGKA?
At $800k for a reasonable TBM700A, you get a pretty significant mission capability upgrade over N147KA…
The challenge would be to stay current on it. My 150hrs/year TT would be about 35hrs/year on the TBM.
To be clear, the engine that has just been top overhauled was also running perfectly – but using too much oil.
OK; it was you saying earlier that you felt the engine was not happy that I thought you had some other indications.
Peter wrote:
My 150hrs/year TT would be about 35hrs/year on the TBM.
You could extend your touring range to more than just the usual suspects. The world starts to get interesting once you cross EU borders… Going to Mykonos for a party weekend would be possible as well. Oshkosh every year a piece of cake.
Note that the TBM can have a 200h service interval so you’re wasting a lot of money if you don’t fly it 200h a year.
