Maximum Permitted Legal Engine Hours

[Thruster87]

Can engines [rotax 503 is 300hrs TBO] be operated on condition or only on manufacturers TBO Legally :;)5: Cheers

 

 

[facthunter]

2-stroke engine hours.

 

A 2-stroke is operated "on condition " all the time. A recommended TBO is probably just what you could use as a guide to what you could expect from the "bottom end" ie the crank department, which has hardened surfaces, rollers and cages, all very carefully fitted and aligned, running with a sparse amount of oil. If there is any misalignment, or sometimes a sideways flutter can occur with the connecting rod(s),which can cause friction with the thrust faces, consequent heating (localised) will burn the oil off the assembly and it will fail, (weld itself ,seize).

 

This can happen with virtually a new motor,as it has nothing to do with wear

 

/ fatigue.

 

The other failure of the bottom end, will happen eventually with increasing time in service, is where the surface of the crank pin (usually ) commences to peel off due to fatigue. This is the case hardened surface that enables the rollers to run without indenting the journal. It is not attached to the metal as a seperate coating, but is obtained by fusing carbon into the surface of the steel to about .5 mm depth & further heat treatment to harden it.

 

At the onset of this condition, little or no, play may be detectible, so without dismantling the crankshaft assembly, no accurate assessment can be made.

 

Once the deterioration starts, it will continue more or less rapidly, play will develop in the bearing, & bits of very hard metal will scratch the bore(s) Or the roller cage may fail & seize or the rod part company with the shaft.

 

Note. Nobody these days dismantles a pressed-up , multi-cylinder crankshaft. The factory supplies complete new assemblies, as cheap as you might expect to service one.

 

The recommended TBO would be based on the situation I have just described & would give a safe margin on the expected time for this to happen.

 

TBO's are established on formulas on actual performance in service, after an initial ( usually low ) introductory figure is struck. Running selected engines over -time in controlled situations, can argue a case for increasing the TBO, so the TBO rises if the case is made. On the other side, failures inside scheduled service times will attract modifications, inspections etc. or reduced Time Between Overhaul. How active this process is in determining what legal TBO applies in your case, I cannot tell, but the maker builds the engine & should have a good idea. A high TBO is a good selling point ,so the maker is not going to give a low one just to sell you a crankshaft when you don't need it.

 

I have expanded this discussion a little to get the concept across, although it is still over simplified. Nev...

 

 

[Guest brentc]

Sorry to throw a spanner in the works, however there is no such thing as 'on condition' in RA-Aus.

 

Coincidentally I heard that this was being looked into at the moment as several aircraft in schools have been grounded due to running over TBO on 2 stroke 582's.

 

This is one of the things that makes RA-Aus different from GA as there is nothing in the technical manual regarding running an engine 'on condition.'

 

The trouble with this is that everyone knows that a 582 will do 1,000 hours on a crank, but the engine manufacturer's TBO is not a recommended figure, it's mandatory.

 

In GA an engine is run on condition after TBO, however it cannot be used any longer in the charter category, only for private flying and flight training and during this time requires compression checks and the like during 100 hourlies.

 

Techman feel free to comment if you can drag yourself away from annual leave.

 

 

[Guest TOSGcentral]

This is an interesting discussion. Here is another view and some background.

 

 

I do not know about BrentC’s statement that TBO is “mandatoryâ€Â. If it is and aircraft are actually being grounded over this – then kiss your ass goodbye to low level schools and expect to pay heaps more for the four strokes and the aircraft that they generally go into.

 

 

Here is some history as perceived on my part:

 

 

The Rotax motors were pressed into service (along with lawnmower engines and anything that was small and ran) in the very early days. There were repeated failures that led directly to the terrible reputation that “ultralights†have subsequently obtained, which was exacerbated by idiot maintenance and engine operation on the part of owners!

 

 

I give the Rotax factory due credit and they poured research and development into more reliable engines. The engines they produce now are great units and with routine maintenance and normal operation a 582 will go 1000 hours – but the manufacturer still puts a TBO of 300 hrs on it!

 

 

Part of the problem was that the engine was small and “we can rebuild that easilyâ€Â. Perhaps so, but a high performance small two stroke needs everything going for it that it can. Unfortunately working on parts of these engines requires specialist tools and also expensive presses to put the crankshaft assembly together again correctly. You can do it at home but chances are it will not last. So the failures continued.

 

 

In my view Rotax responded in two ways: They stopped producing individual components and you have to buy factory assembled main structures. They also jacked up the component prices so while I could get a 582 professionally overhauled for about $2500 a few years ago I now have to contemplate over $4200 for a complete zero hour rebuild and I can get a new engine for only a few hundred dollars more!

 

 

But despite all this the TBO has not changed, and I think it is less to do with any weakness on the engine but more to do with litigation! Why the bloody hell should Rotax have their name besmirched by wankers and repeated failures of perfectly good engines?

 

 

We have made our own bed and in the real world we have to pay the price of laying on it. If Brent C is right and aircraft are being grounded on being over manufacturer’s TBO then I repeat – kiss your ass goodbye because at that value of turn around prices our original low cost aviation out of sight – start by adding $20 per hour plus!

 

 

Do you not feel there may be something just slightly lacking in our airworthiness competency and operation structure? That is not Chris’ fault – he inherited this terrible position he is in. There is no basic training in this area and no sign that any such is planned!

 

 

Just some thoughts.

 

 

Aye

 

 

Tony

 

 

[Thruster87]

So does this mean then that ANY and ALL RAA registered aircraft to be legal under the regs have to be within the manufacturers TBO [Engines] and also that the insurance would be covered. Cheers

 

 

[pylon500]

This may need a bit more research as there are numerous factors involved.

 

Currently Rotax state 300 hour TBO's on 582's.

 

I'm sure this used to be more, but has decreased over the last ten years!

 

Yes, there are stories of 582's going to 1000hrs

 

All of this however (I think) only applies to 'Hire and Reward' aircraft which, remember, are supposed to be maintained by Level 2's.

 

I'm fairly sure that privately owned aircraft, incluing 24-X, 25-X, 55-X and 32-X rego's can be maintained privately, so you could probably maintain your engine 'on condition'.

 

But you may have trouble getting an insurance payout after a crash!

 

If attempting to sell one of these private aircraft into a 'Hire and Reward' situation, you would need to have a complete inspection done, most likely requiring the replacement of the engine.

 

It still pays to maintain good aircraft/engine log-books, even for private operations.

 

Arthur.

 

 

[Thruster87]

Section 3.3.1-2 Issue of Registration Certificate para H item 1 Aircraft of unknown and unproven design,fitted with an engine other then a type approved as fit for the purpose. Will be restricted to the test area for the first 40hrs. So how would a TBO apply here? Say it is a Subaru or BMW engine. Really needs to be sorted out in Black and White as it appears not all agree.

 

 

[Guest brentc]

I too would like to know how a TBO is calculated for a non-aircraft engine. Perhaps TBO's don't apply for such engines. I'd be interested to know.

 

It's interesting how the TBO's are going down for 2-strokes, but they are going up on 4-stroke's. The 912 is up to 1,750 hours now.

 

 

[facthunter]

Engine Hours.

 

My statement using the term "on condition" is not legalistic and has nothing to do with litigation. I suggest that any 2-stroke competent operator would not rely on log times but would have some realistic means of assessing the "condition of the engine", for his own safety. The top end condition may deteriorate over the space of less than 1 hour, that is why nobody could realistically suggest that "time to run" is the main consideration, or the only one ,although it may be the total legal determinant. (Tony's concern).

 

The bottom end life can be better assessed, but may be underestimated. I would suggest that without a pull-through (prop) compression test (carefull of course )Prior to flight and a very good awareness of what the normal revs should be at commencement of take off, a certain amount of crossing your fingers & hoping might be required. In reality, the engine is more likely to die as a result of a failed fuel pump, or a dead battery. Nev

 

 

[lambadaman]

I think you will find that, for any factory built aircraft, the maintainance manual hours MUST be adhered to, unless the local athourity (casa or RAAus) grants an excemption. This would mean that the 300hr TBO on the Rotax two strokes is mandotory, as is the previously mentioned 1750hr TBO for the 912. This time limit apply's to private use also.

 

As for EXPERIMENTAL aircraft, you can go byond this limit, BUT, the engine then also becomes experimental. This may limit the airspace in which you fly (legaly!),

 

When it comes to auto conversions, these too are experimental engines, and as such do not have a TBO. These enginess cannot be fitted to factory built aircraft, for obvious reasons.

 

There is a list (I think!) of approved engines in the RAAus system. These engines can be used over built up areas. If the engine in your aircraft is not on this list, it would be wise to check out it's limitations.

 

There is, I think, a difference between RAAus experimental and GA experimental, when it comes to engine use over built up area's. Perhaps someone on this forum can elaborate.

 

What some schools do with their two stroke engines is replace them at TBO with a new engine, and sell off the old one for use in experimental (or kit built) aircraft.

 

Thats all for now!

 

Gerry....

 

 

[barandbrew]

I was advised by Rotax that if the aircraft was not used for hire then my 912 could be run on condition not TBO and they were aware of 912's with 4000 hrs!!. This seems to contradict the general thought on this thread??

 

 

[Guest brentc]

Just to clarify, I think you'll find that when they refer to 4,000 they are referring to the crank-case / crank shaft. At 4,000 the top end would have had a couple of overhauls. But in essence, yes, you could run it to 4,000 and they say a Jabiru will go to 4,500 in a similar fashion.

 

 

[lambadaman]

I just had a QUICK look at the RAAus website and for a factory built aircraft you MUST follow the manufactures maintenance manual. The only excemption to this I could find was for modifications, which must be approved by a CAR 35 Engineer. If the aircraft is Owner Operated, it still has to be maintained in accordance with the manufactures manuals. If that aircraft is then to go into comercial use (training,private hire), it, and it's log books, have to be inspected by a Level 2 Maintenance Atuthority Holder and he has to be satiafied that the aircraft is properly maintained and airworthy.

 

So as far as I can see, the short answer to the original question is No, the engine must be overhauled at the manufacturs recomended TBO. It does not look like there is any option to operate 'on condition' in the RAAus system! You then revert to CASA itself to make a ruling on your request (at approx. $130 per hour).

 

The above does not apply to Experimental Aircraft, however you probably loose the 'Approved' status of the engine if you go beyond the manufactures recomendations.

 

If anyone can enlighten us further, please do.

 

Maybe Chris can clarify!!

 

Thats all for now.

 

Gerry.

 

 

[Guest J430]

I do not speek from first hand experience however one of my local flyers with a 2 stroke Rotax rebuilds his engine at the (I assume) 300 hour mark, and yes its costly, however, he has found that the compression drops away quite quickly in these engines and 300 hrs is probably there for a reason.

 

I do think it is best to follow the TBO, you can save all the overhaul costs you like but they are no good to you when you are 6 feet under.

 

RAA flying is cost effective as it is, but do not try to cheapen it beyond what has been found to be safe. Its just not worth it.

 

Think about everyone else, not just your hip pocket. Work out your real costs per hour including TBO allowance and put the money in a jar each week when you come home from flying (hide the jar from the Mrs:laugh: ).

 

Then you will not have the stress come TBO time.

 

J:)

 

 

[Guest TOSGcentral]

Thank you for your views J430. May I give a counter opinion please?

 

Of my previous two R582's the last one was 'retired' at 750 hrs for a full rebuilt - because it happened to be expedient at the time. The person that did the rebuild is a renowned Rotax specialist, who has been there and done that and made two or three trips to Austria for factory courses on these engines (and other Rotax products). His comment was that there was a good 250 hrs left in the engine, no noticeable wear, and I was premature with the rebuild!

 

The previous engine to this went virtually a full 1000 hrs with no problems before again being voluntarily retired for rebuild.

 

Now, I have done about 10,000 flights with these engines and the only mechanical hassle I had that caused a major failure was with a 582 I had bought off a CFI/PE/L2 with no log books but an assurance that it had only done 400 hrs. It put myself and student in a paddock (with no drama other than the student giving up flying) on early climb out.

 

I was a tad irrate about this and under some forcible questioning the creature did admit the engine had done about 850 hrs!

 

If your mate is running out of compression before 300 hrs then I suggest you may pass a message that he may care to look at his maintenance and specifically the fuel/oil mix quality that he is using!

 

I am not really amused about the situation at all! We (the small schools) have been on understood 'on condition' maintenance for many years and AUF/RAAus have not been either interested nor concerned.

 

If they are now so concerned (and as has been reported started grounding schools) then the situation is shameful and at least some warning could have been given and a discussion period prior to them abruptly moving the goal posts.

 

Tony.

 

 

[Guest J430]

Tony,

 

I said I assume he does them at 300 hors, but I am not sure, maybe its 600 or 700. I will ask next time I see him. Chances are you actually know who it is and I think you would agree he is the last person to abuse his machine.

 

An engine running in a school like yours do is always going to fair better than a once a fortnight flyer, or worse once a month.

 

But, I do believe, the manufacturer would not say 300 hours for just spare parts sales, before too long they would have no customers at all.

 

I have 450 on a 3300 Jab so far and no serious issues, yet some have rebuilt at this age or earlier.........it could be the rate at which they are flown!

 

Next time I am over there, maybe tomorrow I will drop in and say gooday!

 

J;)

 

 

[Captain]

An engine running in a school like yours do is always going to fair better than a once a fortnight flyer, or worse once a month.

J;)

J

 

Will you please go into this a little further, with particular reference to a J.

 

I would have thought that only running the engine 2 weekly or monthly might have been a bit of an issue in tropical areas or by the sea, where bore corrosion between uses might have been a bit of an problem with a chance to reduce life, but I would have also thought (hoped) that life would not be effected if the aircraft was hangared out here in the dry bits if use was reasonable but maybe fortnightly or so.

 

I sometimes only use my motorcycles fortnightly and it has never been an issue there ..... I don't think ... or at least they still go quick enough thru the Snowy to give me the rush I want.

 

What are your further thoughts and do you have any examples of what has been a problem and what can be done about it ... apart from flying more often.

 

Sorry to question your post but this is an issue for many of us, I reckon.

 

Regards Geoff

 

 

[Yenn]

You are quoting hours to TBO but what is an Overhaul. Does a tear down of the top end, new rings honed bores etc. qualify as an overhaul on a 2 stroke. Does a top overhaul qualify as a 4 stroke overhaul, bearing in mind in both cases that there is no doubt about the condition of the bottom end.

 

 

[Captain]

Ian

 

As an matter of irrelevant interest (well I think it is interesting anyway, so apologies to those that don't) ...... I used to race a Rotax twin in a 250 Superkart.

 

The photo below is a similar kart (but fitted with a Honda RS250 GP engine) raced presently by my mate Sam Zavaglia going into the corkscrew at Laguna Seca and the other pic is the latest incarnation of that engine type made by BRC ................ anyway back to the subject at hand ........... to be safe(ish) those engines needed new pistons every 250 racing kms and new rods + a bearing kit every 2nd set of pistons.

 

But those engines were 250's making 90 hp, revving to 13,500 and pushing thru a 6 speed gearbox to 240 kph.

 

Regards Geoff

 

 

 

 

[Guest brentc]

Yenn, the figure quoted of 300 hours is for TBO, (Time Between Overhaul) which for the 582 it 300 hours due to the crank shaft. Usually a manufacturer will specify a top-end and bottom-end overhaul, which they do for Jabiru engines by quoting 1,000 for the top end. (I personally can't remember what the bottom end is right now).

 

 

[Guest Andys@coffs]

JWill you please go into this a little further, with particular reference to a J.

 

I would have thought that only running the engine 2 weekly or monthly might have been a bit of an issue in tropical areas or by the sea, where bore corrosion between uses might have been a bit of an problem with a chance to reduce life, but I would have also thought (hoped) that life would not be effected if the aircraft was hangared out here in the dry bits if use was reasonable but maybe fortnightly or so.

The previous owner of my J230 used Shell W100 oil and as i understand flew most weeks at least once. With the realities of work for me I felt that I couldnt guarentee once per week and as such, under jabiru's guidance changed the oil to W100plus which was designed to address the issues you raise.

 

Regards

 

Andy

 

Details around what it is and does can be found here http://www.shell.com/home/Framework?siteId=aviation-en&FC2=/aviation-en/html/iwgen/productservice/aeroshelllubricants/pistonengineoils/zzz_lhn.html&FC3=/aviation-en/html/iwgen/productservice/aeroshelllubricants/pistonengineoils/aeroshelloilw100plus_10081015.html

 

(Have a look at the length of the URL when you click on it.....what "brain surgeon" came up with that URL!!)

 

The benefits of W100plus:-

 

Summary of benefits:

 

</IMG>

 

Superior Rust and corrosion protection giving that extra protection to engine parts that may be susceptible to extreme rusting when an aircraft is not in use (for prolonged periods of non-use please use AeroShell Fluid 2F).

 

Improved anti-wear characteristics particularly at engine start-up and eliminates the need for supplemental additives required by certain Lycoming engines. AeroShell Oil W100 Plus already contains the Lycoming additive LW 16702 in the correct proportions and meets Lycoming requirements as well as the US Federal Aviation Authority Airworthiness directive 80-04-03.

 

Promotes Engine Cleanness. The non-ash forming, polymeric additive was developed to eliminate the harmful combustion chamber and spark plug deposits that form during normal operation. High Viscosity Index Base Oils used in AeroShell W oils maintain their viscosity and protect engine components more effectively under the high shear stresses that an engine places on lubricants. Provides Compatibility with other approved aircraft piston engine oils. Mixing with other products, however will result in some loss of the superior performance features of AeroShell Oil W100 Plus.

 

 

[Guest J430]

The W100Plus or the 15W-50 have both got the anit corrossion stuff however, I still think its best to fly them.

 

The Jabiru engine has a Chrome Moly cylinder, and if condesation forms in the bores, it will rust. Read that as WILL rust. I have seen them first hand, however my cylinders seem to be 100% and yes I use the Shell Plus series oils, and it gets flown at least once a week.

 

The Motorcycle engine may have a S/S sleeve or a cats iron sleeve and may have cylinders that are not horizontal. Aero engines with horizontal cylinders have condensation form and settle on the lower wall of the cylinder. Lycoming have nitrided cylinders and I am not sure what else they do but they seem to be less prone to this problem. having said that the Commanche in my hangar has suffered from this problem, albeit over a very long time.

 

As for folk further out west, do you ever get dew in the morning? If the answer is yes......you too can have condensation just not as much as we coat dwellers.

 

I plug the exhaust and air inlet to keep the airflow through the engine to a minimum, you cant stop it completely but it may help keep the volume of moisture entering to a bare minimum.

 

Hope this helps

 

J:)

 

 

[Guest Baphomet]

Of course, there is another solution, consider buying a different engine. The Hirth range has mount compatible engines for 503 and 582 replacements with factory TBO's of 1000 hrs and a 3 year guarantee on the crank. The Simonini (Italy) Victor 2 and 2+ have 1200 hrs TBO and oh, 30 more horses. Time to send Rotax a message. They've been gouging the market for years.

 

 

[sain]

Some of the hirth engines look pretty interesting too, and they weigh in one hell of a lot lighter than the similairly powered jabiru engines (42kg as opposed to 60kg). Pity they are 2-strokes.

 

 

[facthunter]

Cyl. corrosion

 

The 912 (4-stroke) rotax's don't get cylinder corrosion ever, because the cylinders are Aluminium with Nikasil surface treatment, as are the Hirth 2-strokes .The Rotax 2-strokes are all cast iron liners, cast into the aluminium block at manufacture, ( ensuring that the iron is in the annealled (soft) state ) The 2-strokes do not suffer from corrosion very often as even at 50 to 1 there is generally an oily coating left on the cylinder. However the cast iron liner is pretty old technology, and although it can be rebored, there is no guarantee long-term that the bond between the liner and the aluminium structure of the block ,will be uniformly maintained, and heat transfer will be uneven, tending to cause seizure of the pistons. (Bad idea). The OIL ADDITIVES for the 4-stroke engines are targetted at the cam follower pitting problems, that cause rapid cam follower & cam lobe wear, mainly in Lycoming engines when condensation occurs within the enclosed crankcase in little used aircraft. There is very little oil left on the bores of a Jabiru motor to protect it from rusting, after the pretty efficient oil ring has wiped it off, so those additives won't help much. ( The're no disadvantage either ).

 

The material in the jabiru cylinder is (as has been stated before) 4130 steel , a good strong alloy with some nickel in it . It will rust, as you notice it does on the outside. Moisture needs to be present in the cylinder for this to happen. The BEST way to reduce the chance of this happening is to always shut the engine down HOT. DO NOT PARK YOUR AIRCRAFT AND LET IT COOL DOWN, THEN LATER IN THE DAY,START IT UP TO TAXI 200 YARDS TO THE HANGER. The moisture is from the product of combustion. You will see it coming out of the exhaust pipe of the car in front of you, in the morning. Well over 1 liter of water is produced for every liter of fuel. More than enough to damage your cylinders if you don't use your plane VERY frequently. Rust in the cylinders can pug up the rings & wipe the whole side out of the piston. Very unsafe & costly. Cheers Nev...