However, to answer the original questions,
Effects on engines/FCU. Who knows? No testing has ever been done using this stuff as fuel if its not in the Alternative Fuels list in the manual. Starting characteristics (ie hot ones) possible, inability to restart, explosive restart, excessive EGT etc, uneven burn/hotspots in the combustor, I could go on. Additives in IP may rot seals in the FCU/tank/tank liner. Is the stuff clean? Water free? I suspect if youre the sort that uses this stuff youre unlikely to be punctilious enough to run it thru a chammy filter & water check it.
Insurance!!!Sh!t, do you even have to ask??? If IP is not in the Alternative Fuels list approved by the manufacturer and you use it even once there is no question that all warranties will be void, totally, and far more importantly that your C of A will be void too. Ditto your licence. And your employers AOC/Aerial work cert. And as for insurance. Zip. Period.
I take it you use insurance, licences, AOCs, etc wherever you come from CP, or do bits of used wrapping paper do instead?
Economically the cost saving is equivalent to running your Rolls Royce with time-ex chip shop frying oil in the sump instead of best Castrol - & thats not too bright, imho.
Now if its a matter of life and death, or if theres a war on, I suppose thats different, but for commercial work? NEVER
CP, good luck with your career, and save yourself the cost of life insurance cos that wont pay out either if you scribble yourself this way - self inflicted injury you see...