LB: Many new, certified and quality stamped cylinders need to be set up properly by the few remaining competent experts before fitment. Bushings made of cheese. Spark plug suppressors made of unicorn farts...
BAL: Can you explain what is set up before fitment?
What I know is that there are an increasing number of valve guide problems with Continental cylinders, whether they’re on ‘new’ or overhauled engines. An increasing number of frustrated owners take their ‘new’ or overhauled engine to experts who have a process using Prussian Blue to get the correct print on the valve stem tip. Those experts are increasingly frustrated at the ‘quality’ of what they are seeing.
If you are drawing a distinction between before and after fitment and I got that wrong, well done! It proves nothing I say is true and there is no problem with quality control.
LB: I can tell, on the first flight after maintenance, whether timing advance has been fiddled with and set correctly. Some engineers don’t like it when you say: “As a consequence of a change in CHTs and and in-air mag check, I can tell that you’ve advanced the timing on right magneto too far.”
BAL: Is within tolerance too far? If my memory serves me correctly there is a tolerance of magneto to engine timing and also a tolerance of the internal magneto timing and considering there are two units - the total variation can be rather large, but certainly not defiantly "too far". In my honest opinion I believe you can not tell what you stated above, but that there is a change in indication most likely cause by a timing adjustment.
Is within tolerance too far? Errrm, I’ll make a wild guess and say within tolerance is not too far.
“In my honest opinion I believe you can not tell what you stated above, but that there is a change in indication most likely cause by timing adjustment”. It just goes to show that you have zero experience as a pilot flying behind these engines.
Out of maintenance the CHTs were 15C higher on climb-out than normal. That put CHTs above that magic number Lycoming got about right in the information I quoted earlier. A temperature I’d never been before. Mag check shows all plugs working but big differences between mags.
The timing of one of the mags had been advanced too far (and out of tolerance - 25 degrees instead of 22). The engineer probably used a mechanical protractor rather than the accurate equipment used by the Timing Fairy to confirm the problem.
For your education, the reason advancing the timing increases CHT is because in reduces thetaPPP - i.e. brings the peak pressure point closer to top dead centre. A bit like leaning the mixture to 25C ROP.
LB: Blocked injectors usually happen just after maintenance. Engineers don’t like it when you say: “The injector on 4 is blocked as a consequence of contamination introduced during your maintenance.
BAL: I have known far more injectors to become blocked between servicing than just after maintenance, probably a ratio of 10 or 20 to 1!
Now if the nozzle has become blocked due to maintenance, it would be because the nozzle has been removed - just a random guess unless you have filter less aircraft and flow divider. Simply request at your expense to have the stainless fuel supply lines removed and cleaned when nozzles are removed if it is a common event for you.
Yours is very small sample.
I’m talking about the experience across thousands of aircraft. Yours is a very small sample.
“Now if the nozzle has become blocked due to maintenance, it would be because the nozzle has been removed - just a random guess...”. Brilliant guess.
“Simply request at your expense to have the stainless fuel supply lines removed and cleaned when nozzles are removed...”. Spoken like a true engineer! Your fiddling (for which I’m paying) introduces the crud that causes the defect, and your solution is to ‘up-sell’ more fiddling.
I think I’ve mentioned this in other threads. I would offer various engineers many thousands of dollars
not to inflict a range of counter-productive maintenance on my aircraft, if I weren’t committing what’s probably a crime under the civil aviation law. Bleeding money to reduce risk is better than bleeding money to buy risk.
Just as a matter of interest, have you ever seen any engine or engine component that’s ‘new’ or out of overhaul that’s had a defect? Just once? Or are you observing perfection?
Have you ever made a mistake during maintenance that wasn’t picked up and ended up causing an in-air problem. Just once? Or have you achieved perfection?
I’ve made a number of mistakes during maintenance that weren’t picked up and ended up causing an in-air problem. When you’ve worked at it for a long time and you’re not perfect, it’s bound to happen occasionally. That’s why I know what really goes on inside maintenance hangars. But it’s also why I don’t rain down legal hellfire and brimstone every time one of these mistakes is made on my aircraft. I could do it, but I empathise with the people who’ve made the mistakes.