SO WHAT'S THE DILEMMA?
That’s not necessarily to say that it can’t be overhauled, quite to the contrary. It’s just that, for many aircraft owners and operators, rising TTSNs start to become a very costly affair, especially for twin engine aircraft.
A used King Air 100 with twin Garrett’s could be snapped up for $300-500k, then look at what you might pay to acquire one with healthy TBO’s, most likely circa. $1.2-1.5m. A quick reminder then, that the value of an aircraft is largely based on its explicit resource remaining, especially when conducting public or commercial operations. This is the moment one realises that a $400k bargain is actually the same as a $1.1-1.2m aicraft with good engines and props.
So let’s consider what it might take to give the presumed 'bargain-buy' some healthy TBOs. After an investment of circa. $320-350k (per engine) and at least 4 months turnaround time, a timed out engine could be properly replenished by the manufacturer to an 1,800-2,000hr resource (depending on the model). Excluded in this estimate, is the cost of accommodating service bulletins that may have become due - and these can substantially increase the total cost, perhaps by a further 20%+.
Let’s also consider that Walter GE in the Czech Republic are the only authorised establishment that can perform this resource replenishment. Whilst the cost is understandable when one appreciates what is done to overhaul an engine; understandable doesn't make it affordable for the next generation of applications.
For an overhaul, the manufacturers essentially dismantle the entire engine, check, replace and rebuild to an exacting standard, replacing worn parts out of acceptable tolerance levels as they go - and of course – they really know their engines.
Similarly, propellers are also a lifed resource and must be overhauled according to the manufacturer’s schedule. The Avia V508 3-blade and V510 5-blade propellers are commonly paired with Walter GE M601 variants and many of these blades can be found waiting patiently for someone to give them a new leash of life. Avia recently advised that a rough estimate of the cost of overhauling a 0 TBO prop. was circa. €10k vs. a new prop. costing circa. €30k with a 4 month wait for either option to deliver a 2,000hr resource.