Josh-D. S. Davis

Xaminmo / Omnimax / Max Omni / Mad Scientist / Midnight Shadow / Radiation Master

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Engine TBO - Combined info - O320-D (similar for others)
Josh 201604 KWP
joshdavis
Go with the Legal requiremends and Lycoming service limits rather than average based recommendations.

Legal Requirements:
A) If you're a commercial operator, and have TBO as a requirement, then follow that unless you get an extension.
B) If you're flying in a country that requires honoring TBO, then follow those laws.
C) In all other circumstances, the TBO is advisory, not a legal requirement.

NOTE: For O320-D, Lycoming SI1009AU recommends a TBO of 2200 hours if you put on 40h/mo or more, or 2000 hrs otherwise, or an overhaul at 12 years.

Lycoming's service limits:
* Per SI1427B, the max allowable oil consumption limits for all lycoming engines are .006 x BHP x 4 / 7.4 = Qt./Hr. For your engine, that's .006 * 160 * 4 /7.4 = 0.5189 quarts per hour.
* Per Lycoming's "Key Maintenance.pdf", a compression reading of 60/80 is the recommended maximum allowable loss.

Proper way to do it:
Monitor the condition of your engine! If you don't, you could have:
* A minor failure turn into a major failure mid flight.
* A major expense of replacing/regrinding otherwise serviceable parts.

How to extend the life:
* Fly it regularly and that keeps the condensation out.
* If you don't fly it, preserve it per factory procedures.

How to monitor:
* Check the compressions every 100 hours and repair any cyls under 60/80.
* Track the oil consumption and be concerned if you hit 1/2 Qt per Hr.
* Change the oil every 25h for screens or 50h for filters.
* Have oil analysis done, and follow Lycoming's "Key Maintenance" recommendations for metal found.
* Track climb performance normalized for a common density altitude, though this probably will show up as compression or oil consumption too.

If any of those change abruptly, or fall out of acceptable range, then it's time for a more detailed inspection, and likely a repair. Repairs might be a single valve, or even a whole cyl kit, etc, but doesn't always need to be the entire top-end, and even less often needs the bottom end (ie entire overhauled).

Refs:
* http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20Maintenance.pdf - Maintenance Recommendations
* http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1009AU.pdf - TBO Periods
* http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1427B.pdf - Break-in & Oil Consumption
* http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key%20General.pdf - General Recommendations
* http://www.lycoming.textron.com/support/publications/service-letters/pdfs/SL180B.pdf - Engine Preservation
* http://www.avweb.com/news/savvyaviator/187037-1.html - Debunking TBO
* http://www.avweb.com/news/savvyaviator/savvy_aviator_48_reliability-centered_maintenance_part_2_195969-1.html - Reliability Stats for Engines vs TBO
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