Overhauls due to calendar time

[Mike A]

Typically an engine has a calendar overhaul limit (12 years I think). What are the big reasons for this and are there components that can be replaced to mitigate this?

[carusoam]

Run often, a Lycoming IO360 will go on for longer than 12 years.

Sitting unused for years, an IO360 won't make it that far...

Oxidized cams are a serious challenge for unused engines...

It is pretty easy to tell what you are buying with a good PPI. It is pretty easy to tell what you have by how you operate and maintain it.

TC engines are susceptible to top overhauls based on hours and style of operation...

Turbos that sit, are challenged by oil flow and early bearing wear...

Seals, hoses and all things plastic/rubber tend to age...

What do you have in mind? Are you asking about you particular engine?

How often do you fly your plane?

This is an opinion piece based on reading MooneySpace...

Best regards,

-a-

[KSMooniac]

The biggest reason is to ensure a steady revenue stream for the engine manufacturer.

 

As carusoam stated, if they're run regularly to keep the corrosion from getting a toehold, then there is no reason they can't run much longer than 12 years.

[Mike A]

Just wondering. I've had people express concern about the age of the reman (1995) in the Cherokee I am selling. It gets used quite often and does not show issues in the oil analysis. Also, the reman in the 231 is from 1998 so it is pertanent to the new bird as well.

[carusoam]

There is a similar question regarding props, as well.

Best regards,

-a-

[KSMooniac]

They're trying to get you to discount the price further... if you can prove regular use and good oil analysis trends then you should be able to to show that it has life left in it.  

[M016576]

They're trying to get you to discount the price further... if you can prove regular use and good oil analysis trends then you should be able to to show that it has life left in it.

Yep... It's a buyers market....

[201er]

Typically an engine has a calendar overhaul limit (12 years I think). What are the big reasons for this and are there components that can be replaced to mitigate this?

Because if you're past 12 years and not a high time engine, then the plane isn't really being flown that regularly.

[Alan Fox]

The calender issue is only a concern for part 135 operators , I have flown behind 40 year old engines and never had a problem.....The corrosion on the cam thing is so overblown its not even funny , understand most buyers are not really buyers , they are shoppers , looking for the perfect plane.......That would be a NEW one......

[320KPH]

A commodity will always sell if the price is right. All buyers end up buying something. There's always a reason the price is cheap and if it's too good to be true, it usually is...

[Alan Fox]

A commodity will always sell if the price is right. All buyers end up buying something. There's always a reason the price is cheap and if it's too good to be true, it usually is...

I disagree , I know people that have been shopping for airplanes for over ten years .....The price issue I totally agree with.....

[PTK]

The biggest reason is to ensure a steady revenue stream for the engine manufacturer.

This is a very simplistic view. There are valid reasons and many factors at play.

The manufacturer arrives at a TBO in both hours and calendar by looking at the entire population of engines in service realizing that there are differences in this polulation in how individual engines are used. They also realize that these engines will not wear out by tbo when properly cared for and flown regularly. They will however rust out if they are not. Time in use by itself will not wear them out by tbo. Abuse and sitting will and often times before prescribed tbo. Variables like cold starts, temp mismanagement, infrequent flying, climate where they live, etc. The manufacturers know that in GA especially, there's great variation. Some engines fly a lot and some sit a lot. They consider these things and arrive at a conservative TBO that will cover, on the average if you will, their entire engine population. They know that some engines will go far beyond their conservative prescribed TBO but most wont. Incidentally there is data to suggest that by blindly following the prescribed tbo you are entering the so called infant mortality zone. This I think if irc is the first 500 hours after oh! A very long time to be there voluntarily if not necessary!

There are very valid reasons for the manufacturer prescribed TBO from their perspective. There may also be valid reasons to not follow it from an individual owner's perspective. We have this freedom.

As a seller of a regularly flown and cared for engine you need to be able to make this valid case to the buyer. That indeed, there are real and measurable benefits to not oh at TBO because the engine has been cared for and flown regularly.

[johnggreen]

Sometimes, someone will take the time and trouble to post a truly knowledgeable and well thought out response.  Carusoam made a very good post, Allsmiles just made the final closing comments.  This thread for all intents and purposes is complete.

 

Jgreen

[RJBrown]

Average hours per year for Mooney is close to 100. Most would never see Hourly TBO if the calendar TBO was enforced.

[FloridaMan]

I'd take a look at this.

 

http://www.avweb.com/news/savvyaviator/savvy_aviator_45_how_risky_is_going_past_tbo_195241-1.html