ORIGINAL: Ed
Is there any way of telling if an engine is going lean while the plane is flying ? Does it change sound, and slow down, like it's possably over heating ?
ed
Yes, it changes sound.
Yes, it can slow down (partly because of overheating caused by the lean condition and partly because of the lean condition itself)
Yes, it will overheat.
The truly best way to find out is not a simple answer.
Measure the cylinder head temps in flight - for this you will need something like the Venom Temperature gauge or Eagle tree setup. Ideally measure it at the base of the spark plug (they have a thermocoupe available for this) (Also ideally measure the Exhaust Gas temps but few ever go that far).
Take out the spark plug and have a look at it.
[link]http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp[/link]
[link]http://www.strappe.com/plugs.html[/link]
[link]http://www.theultralightplace.com/sparkplugs.htm[/link]
[link]http://www.bcchapel.org/pages/0003/pg11.htm[/link]