I think TBR is a way of saying “we want to do all overhauls in-house so we get to keep all the money, instead of spreading it out among 3rd party overhaul shops like Lyco/Conti do”
It is also a way of saying “sorry, this is not tractor technology that can be overhauled by a blacksmith”. I am not a fan of the overhaul mechanism, it means somebody has the authority to declare decades old parts of unknown quality to be as good as new.
A friend of mine worked on the gearbox for the Bugatti Veyron. I forget the exact figures, but the design life in first gear at full power was measured in minutes.
Gearboxes usually are the weakest link as you can see Thielert/Austro/Rotax. This takes a lot of effort to get right but electronic control helps a lot, I am sure the Veyron will not let you fry the the gearbox. For the Veyron specifically I believe the tyres are the weakest link 
it means somebody has the authority to declare decades old parts of unknown quality to be as good as new.
Yes – it’s called “a man with a micrometer”
Nuffink wrong with that
Steel has no life limit unless you bend it too much or let it go rusty. And on an overhaul everything of relevance is NDTd, which is all that Thielert are ever going to do anyway. They don’t do a CAT scan… I got a quote once and it was 1000 quid for a small part.
It seems universally accepted in the USA that overhauling your engine is the best thing of all. If you get an exchange engine (the TBR concept), you are buying an unknown history.
It seems universally accepted in the USA that overhauling your engine is the best thing of all. If you get an exchange engine (the TBR concept), you are buying an unknown history.
My club is about to get two engines overhauled during the next 12 months or so. I’ve been arguing what you say (and it’s also the cheapest option as long as nothing unexpected happens) but our maintenance man says that a factory overhauled exchange engine (the option expected to be the most expensive) gives the best quality. As I don’t have any particular expertise in aircraft maintenance my word doesn’t count for much in that discussion…
OTOH, if you have the club situation with some 100 different pilots, a substantial number of whom fly single figure number of hours per year, you don’t really know how the engine has been treated in flight anyway, so an exchange engine is maybe the best option after all?
Yes – it’s called “a man with a micrometer”
Great joke. Except it doesn’t really work. How do you find out with a micrometer where you are in the S-N curve? Given that alumin(i)um does not have an endurance limit, that’s kind of important to know.
Overhaul shops should use dye penetrant testing to look for surface cracks. But that way, you won’t find subsurface cracks. Some (even some ADs) advocate eddy current testing, but that’s not done during overhaul.
our maintenance man says that a factory overhauled exchange engine (the option expected to be the most expensive) gives the best quality
It is true that for those who forgot about SB569, a factory remanufactured engine is the least bad option.
It is also obviously true for minimum downtime.
It is also possibly true IF Lyco will give you the core value for your existing engine regardless of its condition. I would recommend researching this area, because (a) Lyco have openly stated that they no longer accept engine cores in “any” condition – like they always used to – (because some were not usable) and (b) I have recently heard that they are refusing to offer the normal core value if the crank is subject to SB569 (this could be a rumour and would be outrageous if true).
The problem with exchange engines is that almost everybody plays the same game: they overhaul their engine all the time they can, and hand it back only when it is too trashed (basically when the crankcases are under spec due to repeated skimming). So most exchange engines are in the region of 5000+ hours TT.
I would certainly not say that a factory overhauled exchange engine gives the best quality, as an unconditional statement. Of course your shop makes the most money on it 
Given that alumin(i)um does not have an endurance limit, that’s kind of important to know.
True, but most relevant stressed parts (that can give big and rapid trouble) in an engine are steel. The crack and conrods are magnafluxed which is a better process. But crankshaft breakages are very rare (the 1997-2000 Lyco issues excepted, and actually the ones at real risk were a small batch which was missing a heat threatment ).
The existing overhaul process does seem to work well in the huge U.S. engine population. There is a small % of unexplained failures despite NDT, which could be due to mfg defects or due to undeclared prop strikes under a previous ownership (a rather common thing – look at how many planes for sale have a different TT on the engine versus the prop, and not all of the sellers know why).
tomjnx 23-Feb-15 01:39 #157
Isnt a TBR similar to a throw away engine?
It isn’t black and white IMO, even with a Lycontisaurus quite a few engine parts are thrown away at overhaul. Plus, Conti tends to eat through cylinders like there’s no tomorrow, while Lyco tends to eat its camlobes for breakfast…
So your saying that when your engine gets replaced TBR what your getting back is an overhauled engine whose parts you dont know where replaced?
Are these post TBR exchanged engines cheaper than brand new engines?
So your saying that when your engine gets replaced TBR what your getting back is an overhauled engine whose parts you dont know where replaced?
Are these post TBR exchanged engines cheaper than brand new engines?
Sadly, there is no such thing as a new engine in the Lycontosaurus world. A new engine will have parts within “factory new limits” but they can be 50 years old, been sitting on a shelf for 30 years, etc.. You don’t know what you’re getting.
In a TBR situation (Thielert/Austro/SMA) you could theoretically get an overhauled engine from the factory but most likely you get a new one. The same is true in other areas such as boat engines. I just bought a core from Volvo Penta and while it said that it can be remanufactured, it was new. They just want to reserve the right to recondition existing stuff should they deem this more appropriate (because they run out on new parts).
I think you can buy a totally brand new Lyco. Last time I looked, a few years ago, an IO540-C4D5D was about $65k.
But I don’t think many people buy them.
I am sure you would get a ~100% failure rate on car engines within a year if you ran them at 65% of max rated power the whole time.
This is a myth. Modern car engines are designed and tested to run at full power their entire expected life. The fact that it is practically impossible for a normal person to do it when you have 200+ hp in a car is another thing altogether. For practical purposes, the cooling system is not large enough for indefinite max power, but this does not mean the engine is not up to the task. I had a VW K70 some ages ago. I remember the manual said when on the Autobahn, it could be run at full throttle with no harm done to the engine, but that was only 75 hp.
Honda, Suzuki and Yamaha makes outboard 4 stroke engines. These engines are the same engines that are used in cars. This boat engines are designed to run at 80-90% their entire life (several thousand hours)
Besides, a O360 is a 5.9 liter engine running cruising at 2400 RPM at 135 HP, and this is “75%”. That is 22.9 HP/liter. This is like a modern 1.6 liter engine should run continuous at 36.6 HP, which is more or less exactly what it does, and it does it for thousands of hours including an awful amount of intermittent starts/stop and accelerating at max torque without any other service than changing oil every 20k km (or less).
And just to prove the point entirely. A rotax 912 ULS. 1.4 liter at 100 HP. It can, and do run at 75% power for thousands of hours with no cams or cranks ever breaking. That is 54 HP/liter, the double of a O360.
There is no use running away from the fact that Lycomings and Continentals are low powered, heavy, old and unreliable tech compared with modern car engines, or any modern engine (boat, skidoo, motorcycle …) What it lacks in reliability it more than makes up for in serviceability and price. A Rotax 912 i costs the same as a O360.
Modern car engines are designed and tested to run at full power their entire expected life
I am sure you are right but you need to read that sentence more than once
It’s a bit like a “warranty for the whole life of the product”.
