All I hear is that the diesel fuel cost saving is counterbalanced by higher maintenance costs so, over say 10 years and say 1500hrs, the total cost is about the same.
My A&P worked a lot on all types, and the DA40/42 for an FTO, and this is his view too.
I am ignoring the UK situation where you are supposed to self declare and pay the fuel duty for all usage except training and AOC flights, which obviously makes the diesel cost picture much worse for pilots who refuel in the UK.
Would anyone strongly disagree, with supporting figures?
“About the same” could mean very different things depending on who you are talking to, and one A&P’s opinion means nothing when it comes to total cost. Numbers please 
Avgas is getting harder and harder to get. Running on diesel/jet seems so much more convenient when projecting a bit into the future. Any serious operator would go for diesel, if for no other reasons than it will prevent wasting fuel/time/cost to get fuel.
The data point needed is cost of engine replacement and whether this increases at a rate higher than inflation. The engines are replaced not overhauled. I am not aware that the current engines do not make their time before replacement. The airframe and systems are pretty good and seem to stand up to service. Useful load for an MEP less good. The ECUs need attention once a certain cycle of error messages occur.
Sorry not to offer hard data I just get to fly them.
I have done some calculations for diesel converting a PA28, it is just not profitable for our 300h/annum.
Even if the airplane already had a diesel, it seems unlikely to be profitable (for us), as there is not that much difference between the price of 100LL and Jet-A1 where I live. The ablility to (normally) run the Lycosaurus well beyond TBO, and no gearbox/timing chain issues, just does not make the book.
If one are unable to run past TBO, then diesel seems a bit favorable in terms of cost, BUT – the diesel engine is more complex and harder to work on. No (few) PMA/used parts available, and any mechanical problem with the engine rapidly turns into total loss due to the fact the engine is less “modular” than the old avgas gulpers.
The industry seems to be going that way anyway, but I will not be an “early adopter” of this technology.
G
It’s way too late (by about 10 years) to be an early adopter now!
The “drift” of my original post was that while the fuel might be 1/2 the cost, the other operating costs seem to be increased by a roughly similar amount. I have not yet met a DA40/42 owner who has reported anything different.
Rental rates from FTOs might differ from the above but that is a different thing; the rate may not be fully costed.
From flying 150 hours on DA42 and owning it for little bit more than one year I can share the same conclusion. Services and maintenance for last 450 hours (until engines expiry) are estimated for 30.000€ – no surprises here, everything is as planned. Although it’s not easy to compare SEP and MEP my reference is TB20 (similar payload, similar speed, similar consumption) that I previously owned.
For TB20, for 450 hours and 3 years of flying I would plan 15.000k€ for services and I would probably spend 22.500 l of avgas – roughly 56.000€. Total 71.000€.
For DA42, for 450 hours and 3 years of flying I plan 30.000k€ for services and I will spend 22.500 l of Jet A1 – roughly 20.000€. Total 50.000€.
The difference in my case is that after this 450 hours my TB20 would still have 1000 hours available on engine while DA42 will have 2 engines TBR. The question is if this 21.000€ of difference is sufficient for funding 2 new engines. And the answer is clear no – if let’s say on every cycle of 450 hours I save €21k at engine TBR/TBO I will have some €80k saved which is kind of close to what’s needed. However, on new engines (both Centurion and AE) the cost of maintenance is significantly lower and this calculation looks much better in favor of diesel engines.
It really depends on the price differential between AVGAS and AVTUR. Where I live that differential is about € 1.25, and then Peter’s drift applies.
I am talking Continental Diesels. The Austro is cheaper to operate. No gearbox/clutch issues, and TBO instead of TBR, at 2.000 hrs instead of 1500. You save around 10-15k€ on that TBO vs TBR difference alone.
The post’s title includes ‘long term’. One can expect the maintenance cost to come down for Continental engines. Gearbox/clutch on new engines now 600 hrs for newly bought engines (up from 300). And I still expect Conti to up the TBR. They’d better to stay competitive.
Also, I’d expect private operators to be able to run ‘on-condition’ anytime soon, as they do in the US. It would make sense given the rule changes here in Europe.
The other thing to take into consideration is the reliability of the cost of the Diesels. Their failure rate is low. Basically, there is no or very little unscheduled maintenance, so no bad jokes like early top overhauls. But I need to be honest here, unscheduled maintenance on AVGAS engines is primarily a matter of higher powered, turbo engines as I understand it. So that’s not apples-to-apples.
Peter – are you sure this isnt the experience from a few years back or engines of an earlier vintage?
As we all know with anything new, they have had more than their share of teething problems, but after a long time, these have largely been worked out of the current crop. I am hearing a much better story with anyone who has one of the current crop of aircraft or replaced their engine(s).
are you sure this isnt the experience from a few years back or engines of an earlier vintage?
No, this is based on current info.
If one goes back to the bad old days, one FTO told me, only slightly tongue in cheek, that they could run a TBM700 for what they were paying to run their DA42 (with 3 our of 4 airframes grounded). But that was at the height of the Thielert issues, years ago.
What I hear about the increased operating cost is that it is not caused by things breaking. It is mostly scheduled maintenance that is simply higher.
