Originally Posted by
Lead Balloon
It’s all folklore.
Plenty of folklore has been produced by piston aero engine manufacturers and others.
The manufacturers design and build and warranty the engines and have liability issues for what they make and say.
If they recommend you sing the star spangled banner on shutdown, I personally would think it is at least worth learning the first line or two or maybe knowing how to hum the tune.
Originally Posted by
Lead Balloon
There are ways to find out if there’s ‘lead build up’ and fouled plugs due to the method of operation.
Fouling due to long taxi at idle is due to an overly-rich mixture. If it’s overly-rich at 1,000 RPM, it’s still overly-rich at 1,800 RPM. That is, unless you lean the mixture…
I am not sure that is quite accurate. I am not an engineer and may be wrong however I understood that the idle mixture setting is set on the carb (for FI on the throttle body or fuel control unit) independently (to a large extent) from the manual (cockpit) mixture control. I think mixture can vary with RPM (at least between idle and non idle). Over rich at idle does not imply over rich at 1800RPM. Similarly I think the rev recommendation and mixture adjustment more about controlling temperatures in the combustion chamber and how temperature impacts lead deposition. Again I am not an engineer though.
Originally Posted by
Lead Balloon
Aggressive leaning during ground ops and stop the fan as soon as you no longer need it. I remember one fouled plug in 35 years of flying pistons.
I was going to say how my memory is heading the same way too as I age but didn't want to take too cheap a shot - FWIW I can't remember exactly how many plug fouling incidents I have had over a similar time period so my memory is probably way worse than yours
I have no doubt that you have only had one plug fouling incident in 35 years and that your technique works. In fact leaning on taxi is actually what Lycoming recommend so no argument from me.
I guess where we differ is when the manufacturer recommends a shutdown technique on a particular engine, I don't readily dismiss it. Lycoming have bulletins and service instructions for their engines (as @roundsounds posted). I would not be quick to think they should be ignored.
my 2c