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Exchange, factory replacement, new or Diesel engine for TB20

Our IO540 engine in the TB20 has exceeded TBO and after 2450 hours not unexpectedly started giving signs that it needs to be replaced. It’s been “Making metal” found in the oil filter indicating it’s time to be refurbished.

I’ve no experience of this, but understand options include overhauling the current engine or swapping it out completely for a factory rebuilt one. A brand new engine would be almost twice the price. Would you go for the overhaul or factory rebuilt?

Is it worth considering a Diesel engine, such as the Centurion 4.0? Is this approved and how big a job is involved in a conversion? The low price of Jet A1 is very attractive today but would need a hefty upfront investment. I understand there are higher ongoing maintenance costs too.

Secondly, I read that the IO540 is approved for use with Mogas. Does that require any other components, eg ethanol resistant fuel tanks/pipes etc., and would that introduce other restrictions such as not above FL100. Can the Mogas be freely mixed with AVGAS and UL91? Is different oil typically used with Mogas compared to UL91?

EGBJ, United Kingdom

You will get a good range of answers, but firstly it depends on the aircraft reg.

For an engine you have these options:

  • an “overhaul” (which has a specific legal meaning and also details certain minimum work done)
  • a “repair” (everything that isn’t an “overhaul” is a “repair”)
  • buying a new/remanufactured/whatever engine and doing an exchange

For TB20 owners who forgot about SB569 (yeah, quite a few!!) and also forgot about the $2500 option (see the writeup on my site) the last one is prob99 the only realistic option due to the cost of a crankshaft. But if yours is pre-1997 or so, that won’t apply.

If it was me, N-reg, I would send the engine to the same US engine shop I last used, for an overhaul. But I realise most European pilots will prefer to take a chance on a European shop. In the UK, Nicholson McLaren is the only shop which gets anywhere near passing even the most casual due diligence across multiple customers willing to speak privately

And if you are G-reg you can’t use the most reputable US shops because they are not EASA145. There used to be a way around this (mentioned in the writeup) involving a US DAR doing an Export CofA but I don’t know the latest on this. It may be possible now, on a private aircraft, to drop in an overhauled engine with an 8130-3.

On an N-reg, an overhaul is never mandatory and a repair is always an option, but an overhaul of an engine with 2400hrs will make more sense for the resale value of the aircraft. Most would-be customers will not understand the detail and will just look at the time since overhaul.

There are no diesel options for a TB aircraft.

No IO540 is MOGAS certified. The O540 (Cessna 182 etc) has a MOGAS STC.

The TB20 engine, IO540-C4D5D, is certified for 91UL. It is one of the last Lyco certified before they stopped the programme.

I would not go for a remanufactured (or any exchange, other than brand new) engine unless there was a pressing economic case, because – as in most areas in life – everybody plays the same game. People overhaul their engine over and over, until it is completely shagged, or has had a prop strike and they can’t be sure of subsurface cracks in the crankcase etc. So exchange engines tend to be very high-hour ones; typically 5000hrs plus. If your engine has 2400hrs and has never had an accident then I would definitely overhaul it.

Have you had the metal analysed? If it is aluminium then probably nothing too pricey, and an OH gets you new pistons anyway (they are cheap). If it is steel then maybe cam followers (a common one in Lycos) and maybe a new camshaft.

Last Edited by Peter at 27 Jul 06:04
Administrator
Shoreham EGKA, United Kingdom

On N-register, and probably others, the legal meaning for engine “overhaul” is very different than most people would assume, so if you’re trying to educate yourself I think the legal definition a good place to start. This is FAA advisory circular that provides it: FAA AC 43-11

The important thing to understand is that an overhaul, by the definition of Advisory Circular can be nothing more than disassembly, inspection to determine that everything isn’t yet worn out, and reassembly. It can also be returning every wearing part to within closer tolerances than it was originally built, or anything in between. So you have to understand exactly what you’re buying, “overhauled” is not in itself a sufficient description.

Thanks for the extensive and prompt answers.

It’s G Reg, 1990 and the metal found in the oil filter is magnetic, so probably steel, hence probably the cam followers/camshaft.

We don’t think it’s worth doing a top overhaul at this stage because it might only be a temporary measure and would be more costly in the long run.

The overhaul quote we have from Nicholson specifies a long list of parts that would be replaced – it’s definitely not just a quick inspection.
There’s an option to overhaul the governor too if we want.

Thanks for the definitive answer on Mogas and Diesel. I had seen some chatter about Mogas elsewhere – it does work, especially if you could get hold of non-ethanol product (in Florida they have something called “recreational mogas” which fits the bill). One pilot based in Hiati reports flying an Aztec exclusively using mogas without problems. But without approval, this is a no-go.

From reading Peter’s note on his engine rebuild, am I correct in thinking a dynamic prop rebalance may also be needed after the engine has been replaced?

EGBJ, United Kingdom

Due to the position of the Lycoming camshaft they are prone to wear if not used regularly, and this will eventually show with metal in the oil filter. Most people with the number of hours you have plus the camshaft wear opt for an overhaul at this stage. Nicholson McLaren have a very good reputation for the overhaul option but you will still wince at the cost. It’s usual to have the starter motor, generator, prop governor, magnetos etc. replaced at overhaul. I don’t see a need to have the propellor touched unless you think it was out of balance. Although the engine may have good compressions the valve lift a new camshaft will have will give you more power. Don’t forget to do a proper engine run-in after overhaul as specified by Lycoming or the overhauler!

As far as Mogas is concerned, if I remember correctly there was a circular around at one time saying it should not be used above 6000ft and with a temperature of > 24C. You should consider the cost saving with respect to safety, engine longevity, tank construction, pipe-runs etc, and all the other aspects of owning an aircraft e.g. hangarage, parking, maintenance, insurance, availability.

jxk
EGHI, United Kingdom

the Lycoming camshaft they are prone to wear if not used regularly

I believe it’s more a factor of time than use. The oil drips quickly and then corrosion is a function of time and climate. After every flight, your crankcase will be full with humid air because water is a by-product of combustion and leaks through the piston rings into the crankcase. I keep reading that “fly your engine for 60 minutes to burn the water in the crankcase” but I think that is nonsense because you keep adding water while the engine is flying. Open the oil filler immediately after a flight and you can see the amount of water vapor. I have built my own crankcase dehydrifier for this purpose. In addition I hope that there is value in Camguard but there is not much substance to its claims.

Although the engine may have good compressions the valve lift a new camshaft will have will give you more power.

If that was the case, the engine would have been south of the airworthiness line for years. You need a significant reduction in valve travel to experience any degradation in performance.

If you have metal particles in the engine oil system, everything fed from that needs to be opened and cleaned. That includes the governor, and the prop. You don’t need to “overhaul” these two; a “repair” is sufficient. There are some mandatory replacement parts if these things are opened at all, but they don’t cost much. I have seen a 2B Hartzell prop opened up and sorted for a few hundred quid.

If you don’t do this, the metal will just end up in the “new” engine!

Mogas does work in an IO540 with 8.5:1 pistons, especially if you use avgas in one wing and use that for takeoff, and it is well known that this is fairly widely done, especially in the 3rd World (anywhere south of the Alps ), but it isn’t legal Also the loss of operating ceiling would make a TB20 pretty pointless.

I keep reading that “fly your engine for 60 minutes to burn the water in the crankcase” but I think that is nonsense because you keep adding water while the engine is flying. Open the oil filler immediately after a flight and you can see the amount of water vapor

I don’t find that. I used to get a lot of brown watery sludge when I used Exxon Elite but that stuff is well known for that.

The reason for never flying for less than about 1hr is that the entire oil system is brought up to a temp where the water boils off. Sure it is true that water vapour will find its way back in after you land, but that is just the way these engines are made (open breathers).

According to one AAIB report (4x fatal IOW PA28 one, discussed here several times, and a damning example of UK GA “maintenance”) a 40% loss of valve lift was found to reduce power by 10%. This is less than most would expect, but 10% is going to impact (no pun intended) the climb performance substantially (much more than 10%) because the climb rate is the excess power only.

Last Edited by Peter at 27 Jul 14:50
Administrator
Shoreham EGKA, United Kingdom

Overhaul exchange is like roulette sometimes you get a good engine and sometimes you get a bunch of scrap, my advice would be that if your engine has been reliable over the years and not taken any knocks you need to hang on to it.

There are only two places in the UK I would consider sending an an engine for overhaul, Eisenburg engineering or Nicolson, my personal preference would be Nicolson…………they have done countless engines for my customers and myself without any drama. It has to be added that when one of my low time engines had to come apart for a shock load inspection and the new Lycoming parts they had fitted were not up to scratch it was them who gave Lycoming the hard time to get the issues resolved…… I just let them sort the problems.

It is when things go wrong that you find out what good after sales service is and I can’t fault Nicolson on this issue.

Overhaul exchange is like roulette sometimes you get a good engine and sometimes you get a bunch of scrap, my advice would be that if your engine has been reliable over the years and not taken any knocks you need to hang on to it.

I may have said this before but when I looked for an exchange engine in 2008 (SB569) to minimise downtime, all the engines I found had upwards of 5000hrs on them. Plus of course unknown history in terms of shock loading (potential subsurface cracks which in aluminium cannot be detected with dye penetration methods). This was in the USA.

The engine itself is a fairly rare variant (IO540-C4D5D) and very few exchange engines exist to start with.

I tried to buy one of the 14 Socata (rusted up) engines, to send to the USA for a rebuild, but (a) they wanted too much for it and (b) they insisted on getting it overhauled before selling it but I didn’t want the engine done by some anonymous French shop which could perhaps be fairly well relied on for “pragmatism”

Administrator
Shoreham EGKA, United Kingdom
9 Posts
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