Is Your Engine Healthy?
Some factors for evaluating your engine’s condition
By Textron Lycoming
As an engine builds operating hours and approaches TBO, which may be either the manufacturer’s recommended operating hours, or a calendar year limit before overhaul, the question arises concerning the decision to either continue flying, or top overhaul, major overhaul, or exchange engines. The following nine points can help make that decision.
The operator and maintenance personnel should know what has been the general history of oil consumption during the life of an engine.
A possible danger signal concerning engine health is a definite increase in oil consumption during the recent 25 to 50 hours of flight time. The oil screens and filter should be carefully observed for signs of metal. Maintenance should also take a good differential compression check at this time. They should also look in the cylinders with a gooseneck light or a borescope to detect any unusual conditions in the combustion chamber.
If you haven’t looked at your air filter lately, it would be a good idea to carefully inspect it for wear and proper fit. This is all the more important when operating in dusty areas, and definitely could be a cause of increased oil consumption.
Engine history and calendar age
If a powerplant has been basically healthy throughout its life, this would be a favorable factor in continuing to operate it as the engine approached high time. Alternately, if it has required frequent repairs, the engine may not achieve its expected normal life. The engine logbook should contain this accumulative record.
Another important aspect of an engine’s history would be its calendar age. Engine flight time and calendar age are equally important. We have observed that engines infrequently flown do tend to age or deteriorate more quickly than those flown on a regular basis. Therefore, Textron Lycoming recommends both an operating hour limit and a calendar year limit between overhauls. Service Instruction 1009 gives these recommendations, but other items in this checklist will help to determine if an overhaul or engine exchange is needed before the engine reaches these recommended limits.
Pilot’s opinion of the engine
The pilot’s opinion of the powerplant based on his experience operating it is another important point in our checklist. He will have an opinion based on whether it has been a dependable powerplant, and whether or not he has confidence in it. If the pilot lacks confidence in an engine as it approaches the manufacturer’s recommended limits, this could be a weighty factor in the decision to continue flying or to overhaul it. He should consult with his maintenance personnel concerning their evaluation of the condition of his powerplant.
The basic question here would be how the engine has been operated the majority of its life. Some engines operating continuously at high power, or in dusty conditions, could have a reduced life. Likewise, if the pilot hasn’t followed the manufacturer’s recommendations on operation it may cause engine problems and reduce the expected life. This becomes a more critical influence on a decision in single engine aircraft, and also for single- or twin-engine planes flown frequently at night or in IFR conditions.
Good maintenance should aid in achieving maximum engine life; alternately, poor maintenance tends to reduce the expected life. We notice among those powerplants coming back to the factory for rebuild or overhaul, that the smaller engines in general have had less care and attention, and in a number of instances have been run until something goes wrong. The higher powered engines have generally had better maintenance and show evidence that the operators do not wait until something goes wrong, but tend to observe the manufacturer’s recommended operating hour or calendar limits to overhaul. The engine logbook should properly reflect the kind of maintenance provided the engine or engines. The technician who regularly cares for an engine will usually have an opinion about it’s health.
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