Some good points here, to reinforce some of the commercial/design issues with what component needs to be protected and which are sacrificial in the hot/hung start scenario:
- Starter = $80k
- Engine = $7million
- Combustion Chamber = $250k
(and you have to remove the engine to fix it of course!)
On the subject of longevity due to cooler starts, depending on your engine type. If you have an engine type that is usually removed unscheduled/scheduled for combustor damage as the prime cause (instead of cyc limited, EGT limited, turbine/comprssor deterioration), then a cooler start policy is a good thing.
Basically all of the engines that I deal with - Trent, RB211, PW4000, JT9, CFM, V2500, GE90 etc are not driven off for combustor damage, since the designs/modifications make them so much more robust in the combustor area. In fact the only engine I ever removed for combustor damage was at least 6 years ago.
So any further damage to the combustor will only be exposed in the overhaul shop, on a scheduled visit. And since all our engines are power-by-the-hour then the beancounters don't care about the extra damage.
Regards,
N1 Vibes