Approved Lean of Peak Operations - Does Not Invalidate RAM Warranties

Simply put, RAM is not opposed to you properly operating your engines LOP in accordance with FAA approved operating procedures.

RAM has never denied warranty for RAM overhauled engines that have been operated in accordance with Lean of Peak (“LOP”) operating instructions from the Type Certificate or a Supplemental Type Certificate holder, or that have been otherwise approved in writing by the FAA. Please understand that operating LOP is not suitable for all airplanes, engines, or pilots, and may not be appropriate under certain operating conditions. It is not a universal “fix all” to cutting operating/fuel costs. Improper LOP operations can result in engine damage that may be difficult to detect and expensive to repair.

To have any chance of being successful at LOP operations you must, at a minimum, have: (i) balanced fuel injectors; (ii) well-maintained intake, fuel and ignition systems; (iii) accurate six-point engine instrumentation; and (iv) LOP operations training. Continuous monitoring of power and mixture settings, exhaust gas temperatures and cylinder head temperatures is required. Remember, LOP operations are even more demanding at high altitudes with big bore turbocharged engines.

For our Twin Cessna customers, RAM has maintained a long standing position on mixture management at cruise power, which has always been to operate the engine(s) at rich-of-peak (ROP) as opposed to operating at either Peak, or Lean-of-peak (LOP). A rule of thumb for CMI 520 Series engines has been: at 75% power set mixtures 100° rich-of-peak; at 65% power set mixtures 75° rich-of-peak; at 55% power set mixtures 50° rich-of-peak for all cruise operations. Such mixtures will increase the life of the exhaust system, turbocharger, engine valves and rings, reference Cessna Model 340A POH, Section 4, Normal Procedures (amplified procedures), page 4-21, issued 1, Nov. 1977, Revision 1 - 1, April 1978.

The bottom line is it’s your airplane and how you operate it is your choice and responsibility.