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Engine TBO


Chris SS
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I have searched all over and cannot seem to find the relevant laws.....

 

Please would someone list the maintenance requirements for a VH-registered aircraft operated under part 91.

 

1. What are the mandatory periodic inspections? (I assume 1 year or 100 hrs, whichever first?)

 

2. Are periodic oil changes mandatory or simply advised?

 

3. Is there a calendar life on a Lycoming O-320 or only a TBO? If there is a calendar limit, would the overhaul requirement be as extensive as as a motor that has reached TBO with calendar life remaining?

 

4. Prop calendar limits?

 

5. Airframe X-ray and fabric cover?

 

 

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1. What are the mandatory periodic inspections? (I assume 1 year or 100 hrs, whichever first?)

2. Are periodic oil changes mandatory or simply advised?

 

3. Is there a calendar life on a Lycoming O-320 or only a TBO? If there is a calendar limit, would the overhaul requirement be as extensive as as a motor that has reached TBO with calendar life remaining?

 

4. Prop calendar limits?

 

5. Airframe X-ray and fabric cover?

1. Per Dafydd's suggestion LBS/CofA will specify maintenance schedule.

2.Engine manufacturer will set out minimum maintenance levels for your engine. You will find a combination of recommended and mandatory items depending upon the engine type and operating conditions. In my opinion it makes no sense to 'stretch out' time between oil changes. Regular oil changes are far cheaper than the potential damage to the internals of your engine by running old/dirty oil.

 

3.Engines all tend to have a calendar limit and hrs limit for calculating TBO, however provisions are in place to operate engines 'on condition' beyond TBO limits for private/air work purposes. As for overhaul costs, I suspect main variation is based on condition of components far more than simple calendar time.

 

4.For propeller TBO the prop manufacturer data needs to be consulted. AD/PROP/1 may also give you more info on this one.

 

5.Regarding AF inspections you need to take into account the current manufacturers maintenance schedule. For example Cessna now have the SIDS inspections, designed to ensure ongoing Airworthiness of their older aircraft. Although fabric is not my specialty, I understand that fabric is inspected and tested routinely and replaced 'on condition'. Modern fabrics have brought about a new issue in that the underlying structure may now develop defects well before the fabric starts to deteriorate. Inspection of the underlying structure needs to be considered in addition the the state of the fabric.

 

Hope this all helps...

 

 

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As you can see from my previous post the role of 'maintenance controller' (which is the responsibility of the aircraft owner) requires a significant amount of research and organisation to do well. In my experience it is one of the least understood aspects of aircraft ownership that I encounter as a LAME/L2.

 

I don't say this to try and belittle owners and I think that anyone who has dealt with me will know that I am happy to offer 'free education' as a part of their maintenance visit. My desire is simply to raise people's awareness of the significant responsibility that comes with aircraft ownership. I also highlight in a friendly manner common errors that I find on their MR's which would cause problems in the event of a CASA ramp check.

 

 

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Thank you for your replies.

 

The info on the logbook statement was a great help - a step in the right direction.

 

I have done a fair bit of research over the weekend and still don't have 100% clarity.

 

The logbook statement says that the aircraft should be maintained in accordance with Casa Schedule 5. Schedule 5 gives a detailed description of the planned inspections, but not calendar times or limitations.

 

I have established that the engine in question has a remarkably high 2400hr TBO and only has a few hundred hours on it. It was overhauled 11 years ago. It has been regularly maintained and used and 25hr oil changes done. I have heard the 'on condition' rule but cannot find any reference to it... Please help. I

 

I am considering buying the aeroplane. Maintenance history looks good, blow-bys all good and I am sure that the motor will be ok 'on condition', but I would like to understand the calendar life/on condition rule.

 

 

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AD/ENG/4 specifies engine on condition criteria, which will apply once calendar time is reached.

 

Also worth noting that in CASA's view even when maintaining to Sched 5, manufacturers time limits are still expected to be allowed for. For example many Cessna owners had argued that SID's inspections were not required as their aircraft was being maintained per Sched 5, but CASA issued an AWB earlier this year which clearly said that the extra manufacturers maintenance requirements could not be ignored.

 

All this is a long way of saying you will find various time limits for maintenance and parts replacement requnrelenting within the manufacturers maintenance schedule.

 

 

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Guest Maj Millard

On conditions requirements include but are not limited to ; suitable compression figures within manufacturers range, good oil pressure, only normal trace metal in oil filter cut, no major oil leaks. Then you need a LAME willing to sign the engine out. (IE: put his arse on the line) There could also be some additional operational limitations with a TX engine as to where the aircraft may or may not fly, and the requirement for additional oil and filter changes.......I have previously done pre- purchase inspections on otherwise perfect aircraft with a 10 airframe, but recommended against the sale because of a TX engine.....At most you would probabily be looking at 200 hours of operation in the on- condition state, before looking at a rebuild or new engine.......Maj....

 

 

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So the way I now understand it (very simplified) is that the engine needs to be overhauled at TBO or calendar life for commercial ops, but for private ops can continue to operate provided a LAME signs that the motor is OK?

 

 

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As others say AD/Eng-4 gives what must be complied with. Ad's from CASA also must be complied with, but you can run on condition, way past TBO legally for private flying. I have just bought Mike Busch's book, "Manifesto" It makes interesting reading and he has run his C310 twin engines way over the TBO hours. Have a look at www.savvyaviator.com. He pushes the view that too much maintenance is counter productive and can even prove it.

 

 

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Two things to watch out for in an "on condition" engine, especially if it's over the recommended calendar time:

 

(1) Corrosion inside the front end of the crankshaft, where fixed-pitch propellers are used. The only way to check this is to remove the welsh plug from the centre of the propeller flange, and take a good look inside. Got your LAME to do that and to replace the plug with a new one afterwards.

 

(2) With small Lycomings - look for oil getting into the starter motor. If the starter is covered with black oil, the centre crankcase joint on the engine is starting to "work". That's a sure sign it's time to overhaul.

 

 

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