Unfortunately my club have decided to sell my beloved Arrow II. So I now find myself airplane-less.
I am giving some thought to the idea of purchasing something myself. Something that I can afford to fly without having to worry too much about he hourly cost.
That leads my down the road of a permit aircraft.
A Rotax 912 ULS seems to be very common in permit aircraft, and I’d like to try and get an idea of the real world cost of operating it. That’s part of the picture of building a budget to see if this is something that I can afford or not. So I would really appreciate the input from anyone who is an owner of such an engine, on the real world costs of operating it.
Fuel – pretty easy. Seems to be 18-20ltrs / hour at 75% power * fuel cost. I think it can only be E5 (or Ethanol free) but not E10? Avgas I understand to be fine too but then the engine needs 25 hour checks instead of 50 and fuel cost is doubled.
50 Hour check? As a permit aircraft in Ireland I think I’ll be allowed to do this myself (I’m checking this out).
I think it’s basically an oil + oil filter change + an inspection of the engine bay components. So parts I’m guessing are €50-€75, plus my own time.
Is that reasonable?
100 Hour check? Again I believe (subject to checking) that I’ll be allowed to do this myself.
I think it’s basically oil + oil filter change + spark plus (8) to be changed and inspection of engine bay components. So I’m guessing parts €70-€100 plus my own time.
Is that reasonable?
Presumably at some (all?) of these inspections other bits will be seen to be worn and need replacement. What should I be budgeting for that? Is it typical that something else needs to be done every time, or just occasionally?
Annual inspection. Obviously this is a bit harder. While I think I’ll also be allowed to do this subject to the supervision of an inspector, I probably won’t have the skills for this, at least initially. So I might need to ask for help with this. I know that costs on this is an impossible question as lots of it is airframe related rather than engine. But looking at the engine side alone, is this part typically any more expensive than the 100 hour check?
I understand that there is also a 5 yearly hose replacement? Is that correct? What should I be budgeting for this?
I see some mentions online to a gearbox service. How often is this done and what should I be budgeting for this?
What should I be budgeting as the cost for replacing the engine? I understand that they have a TBO of 2000hrs. Do they typically make that? Are they allowed go on condition after that or is it a hard limit? All I can find online is a US price of about $60K (presumably unfitted). Any estimate of what the cost would be in Europe once VAT, Duty etc + fitting is added?
Is there anything else in relation to the engine that I should be budgeting for?
I’ve specifically kept this specifically about the engine rather than an airframe, because that way it can be useful to others in the future as this engine is so widely used in permit aircraft.
Thanks
Colm
I’m pretty sure you must have seen https://www.rotax-owner.com/en/ with its wealth of information on 912 ownership. There and on the Rotax website you will find useful info on how to operate and maintain the engine. Complete maintenance schedules for hours and calendar times available.
I have operated only new or relatively new 912’s so my experience is probably a bit skewed and certainly incomplete as I have not gone through the 5-yr rubber replacement nor the gearbox inspection process.
Fuel – pretty easy. Seems to be 18-20ltrs / hour at 75% power * fuel cost. I think it can only be E5 (or Ethanol free) but not E10? Avgas I understand to be fine too but then the engine needs 25 hour checks instead of 50 and fuel cost is doubled.
Fuel consumption is as you say. Upto 10% Ethanol is allowed. Of course the airframe may be the limiting factor here.. If using Avgas for more than 30% of the time you need an oil change at 50 hrs, not 25, else every 100 hrs. But maybe your local regulations call for a 50 hrs check for engine and airframe?
Regarding oil consumption, it should not exceed 0,06 liters/hr. Mine consumes less than half of this, so 2-3 liters every 100 hours.
50 Hour check? As a permit aircraft in Ireland I think I’ll be allowed to do this myself (I’m checking this out).
I think it’s basically an oil + oil filter change + an inspection of the engine bay components. So parts I’m guessing are €50-€75, plus my own time.
Is that reasonable?
3 liters of oil, an oil filter and a copper ring for the sump bolt will indeed set you back some €75. As to doing things yourself, you will see that almost all at the above mentioned rotax owner group do that. But it is highly recommended to do a course first. There are some peculiarities that really need training, and some tools. In particular synchronisation of the carburettors (mechanically and pneumatically) every 100 hrs. It’s not more than 30 minutes, but you have to know how to do it. It’s actually handier to have two persons present, one in the cockpit..
100 Hour check? Again I believe (subject to checking) that I’ll be allowed to do this myself.
I think it’s basically oil + oil filter change + spark plus (8) to be changed and inspection of engine bay components. So I’m guessing parts €70-€100 plus my own time.
Is that reasonable?
The spark plug type has been changed a few years ago and is now more expensive, some € 30 each. However, they only need to be changed every 400 hrs.
Presumably at some (all?) of these inspections other bits will be seen to be worn and need replacement. What should I be budgeting for that? Is it typical that something else needs to be done every time, or just occasionally?
Very little for me so far, but it could increase over the years.
Annual inspection. Obviously this is a bit harder. While I think I’ll also be allowed to do this subject to the supervision of an inspector, I probably won’t have the skills for this, at least initially. So I might need to ask for help with this. I know that costs on this is an impossible question as lots of it is airframe related rather than engine. But looking at the engine side alone, is this part typically any more expensive than the 100 hour check?
Annual is basically the same as a 100 hr service. There is this requirement to do a complete disassembly of the carbs at annual/200hrs which is a bit of a tedious job, especially getting the engine to run smoothly afterwards, could easily be 3-5 hrs. There is some debate on the owners forum whether to do this or not. Other than that job, the tasks should not be more than say 3 hours by someone who is experienced. Note that every 2 years you need to exchange the cooling fluid.
I understand that there is also a 5 yearly hose replacement? Is that correct? What should I be budgeting for this?
It’s all rubber parts, not just the hoses, so also the rubber parts in the carbs. Again, haven’t been through it yet. I suppose the materials alone could be between € 500 and € 1000, and it would likely take a full day of work, if not more. Again, on the forum you will see quite some debate whether to do this of not. I certainly will.
I see some mentions online to a gearbox service. How often is this done and what should I be budgeting for this?
Every 1000 hours if using Mogas, and 600 hours if using Avgas I believe. Don’t know what it entails. The inspection itself needs to be done by a certified Rotax shop. Talking about gearboxes, every 100 hours you need to do a torque friction test. Work is minimal, but you need a tool.
What should I be budgeting as the cost for replacing the engine? I understand that they have a TBO of 2000hrs. Do they typically make that? Are they allowed go on condition after that or is it a hard limit? All I can find online is a US price of about $60K (presumably unfitted). Any estimate of what the cost would be in Europe once VAT, Duty etc + fitting is added?
I don’t know the price of the engine. Looks like I don’t need to know either because when it’s time to consider replacement my own body prob40 would be reaching TBR or hopefully TBO. The common knowledge is that the core engine is as reliable and durable as it gets. As long as you do the proper maintenance and replacement of all components the engine itself will run forever. Can’t find the report right now, but core engine failure is extremely rare. Many reports of engine running for 4000 hrs and counting.
dublinpilot wrote:
Is there anything else in relation to the engine that I should be budgeting for?
I haven’t experienced anything so far. The only slight snag is that I am beginning to get some false reading on some of the sensors, which seem to be a wiring/connectors issue more than the sensors themselves. Wiggling them a bit usually helps. I have not had this on the Thielerts. Don’t know whether this is Rotax typical or also is a common thing on LycoContiSauri.
Should you consider a C/S prop my experience with a hydraulically operated governor is better than an electronic/mechanical one. More stable RPM’s
Hope this helps. Something may pop up in my mind later. Surely others with more experience will chime in here!
Sorry for your loss Colm 
1) do you think owning is the right solution for you ? Do you want to dedicate the time to enjoy your purchase both for flying and taking care of it ?
2) what is your mission ? Do you think a 2 seater won’t be a bummer for you sometimes ?
3) Yes the running costs are much lower.To me the maintenance cost of a UL is closer to a car’s one than a certified GA one. Fuel is not an issue.
But the main savings come from hangaring if you have that option of a grass strip. Some in France are ridiculously cheap. And you wouldn’t park your plane outside.
dublinpilot wrote:
Unfortunately my club have decided to sell my beloved Arrow II.
Sorry to hear that!
Fuel – pretty easy. Seems to be 18-20ltrs / hour at 75% power * fuel cost. I think it can only be E5 (or Ethanol free) but not E10? Avgas I understand to be fine too but then the engine needs 25 hour checks instead of 50 and fuel cost is doubled.
A 50 hr inspection is need only if you run on 100LL more than 30% of the time, otherwise the inspection interval is 100 hrs. With unleaded AVGAS the inspection interval is also 100 hrs. (Of course the airframe may require 50 hr inspections.) There are no 25 hour inspections, except a single one for new engines.
We have been running Rotax 912 engines on club ULMs for some time now and several thousand hours.
@aart about sums it up well.
I would add we run on unleaded 95 which is E10 with no problem.
We use 10 – 13 litres an hour
Oil is motorcycle oil and not aviation oil. This is stressed in the POH
All hose and electric connections need to be checked for tightness (visual and perhaps finger check) before flight or at least before each flight of the day.
There is a strange way to check oil in that you take the cap off the reservoir and turn the prop until you hear a glug glug glug. Only then you check the level.
Our expenses other than gearbox check and new hoses have been the need for a couple of new magnetos (these are the same as used on the Ducatti motorcycles and therefore are not hugely expensive even by French.aviation standards)
The other thing we have had 2 of is the exhaust. About the price of a Renault Clio exhaust.
We have had one engine overhauled at a bit over 2300 hours and at a cost of around €13000. It turned out it wasn’t really necessary but it is a training aircraft. We were quoted an all in cost for a brand new engine including installation of.€30,000. That was before inflation took a hold and pre Covid.
We recently had a prop strike on a plastic taxi way marker at low speed. Duc prop was damaged and gearbox checked (advantage of a gearbox no need to strip the engine).
Don’t know the exact cost of inspection and new prop but it didn’t cause the club president or treasurer to break into a sweat.
gallois wrote:
We use 10 – 13 litres an hour
That is with a fuel-injected engine, I guess?
The overhaul prices seem a bit high – Loravia overhauls for 5K and sells overhauled engines for 10-12K – https://loravia.com/shop/en/index.php?route=information/information&information_id=8 , new 912ULS is about 20K – for example 265KNOK with tax at Edge Perfomance.
The gearbox inspection is around 300EUR.
My typical fuel consumption is no more than 15l @4800 – its actually quite pointless to go over that in Savannah for those last 10-15kmh ..
Airborne_Again wrote:
That is with a fuel-injected engine, I guess?
Rotax 912A @4800 RPM I saw consistently 15L/hr on my ferry trip from Sweden.
Colm asked for the consumption of the 912ULS, same engine as my 912S at 75%. I don’t think this gets below 18 ltr/hr at 75%
As to the figure quoted above by @gallois could that be for the 80 HP 912 UL?
The 912iS is quite a bit more fuel efficient, 20-25%?
Anyway, in money terms we are talking peanuts anyway for fuel..
PS. No carbs on the 912iS. So somewhat easier maintenance and less possibilities of snags. Supposedly also smoother, although the carbed engine are already quite smooth. Not sure if it brings issues in terms of true or false ECU failure warnings. Any experience?
….I love the Rotax engine like starting when warm….unlike a hot start on a heavy bore continental, which is like managing a U-boat in an emergency dive :-)…but being honest I prefer the grumbling and final roaring of the heavy bores than the honda motorcycle sound of the Rotax, that feeling lasts till I take the fuel hose out for 300 Liters of AVGAS. The comforting thinking on my side is however no replacement for displacement and at the end the more powerful Rotax engines will be as costly to operate as an IO520 :-),…enjoy it while you can.
