You can get maximum life out of your engine if you treat it well before, during and after flight—and if you keep up with recommended maintenance procedures.
All airplanes have an oil temperature gauge, but, depending on the aircraft, two other sources of engine temperature information may be available:
CHT—A cylinder head temperature (CHT) gauge measures just that, the temperature at the cylinder head. CHT is a critical indicator of engine health, especially on high-powered turbocharged engines.
CHT can be adjusted with cowl flaps, if equipped, and by adjusting fuel and airflow. On hot days, you may need to enrich the mixture, open cowl flaps, lower the nose, or even reduce power to keep CHTs within limits. Always consult the POH to learn how to manage high engine temperatures.
EGT—An exhaust gas temperature (EGT) gauge measures the temperature as the exhaust leaves the cylinder. If the engine is turbocharged, the gases will be measured just before entering the turbocharger, by a turbine inlet temperature (TIT) gauge.
Lean the mixture by pulling the mixture control aft, which reduces the amount of fuel mixing with the air entering the engine. The fuel-air mixture thus becomes “leaner” because less fuel mixes with the same amount of air. When leaning the mixture, the EGT gauge shows the temperature climbing until the cylinder being measured reaches its peak temperature (peak EGT), indicating relatively efficient fuel-air combustion. Refer to the POH for correct mixture settings at various power settings.
When the mixture control is moved forward from peak EGT, the mixture is said to be rich of peak (ROP) because more fuel is being added to the fuel-air mixture. Moving the mixture control aft from the peak EGT position removes fuel from the mixture and thus the mixture is lean of peak (LOP). In both cases, actual EGT is lower than peak EGT.
For most airplanes, correct mixture settings are detailed in the POH. As you gain experience with leaning, you’ll find that it saves gallons of fuel and helps the engine run better. Follow the POH mixture settings carefully; this is not the time to experiment on your expensive engine.
Tip: Pilots should lean appropriately anytime they are below 75 percent power, regardless of altitude.
An annual or 100-hour inspection is done to the entire aircraft. The inspection must be signed off in the “aircraft” logbook, which means that the inspection applies to everything on the aircraft. However, it is often helpful to have the inspection signed off by the mechanic in the “engine” logbook as well, so that inspection status is easy to determine. No matter which logbook is used, there are specific requirements for the inspection of the engine. These requirements can be found in the federal aviation regulations (FARs) and in the manufacturer’s maintenance manuals.
Typical items that a mechanic examines include:
Time between overhaul (TBO) is a recommendation by the engine manufacturers to indicate the expected engine overhaul interval. TBO is given in both hours on the engine and calendar time. Many Lycoming engines, for example, have an hourly TBO of 2,000 hours and a calendar TBO of 12 years. If an engine has only 300 hours but 20 years have passed since its last overhaul, it is likely in need of an overhaul.
These intervals are based on extensive engine testing and years of field experience. Remember that your airplane engine operates at much higher power settings for much longer than a typical car engine. Regular service and overhauls are essential to ensure that your engine delivers reliable, safe power every time you fly.
When you and your mechanic decide that it’s time for major engine service, there are three possibilities:
Regular service and overhauls are essential to ensure that your engine delivers reliable, safe power every time you fly.
Airplanes that seldom fly can develop engine problems due to corrosion, and these are frequently good candidates for some cylinder work between TBO intervals. A top overhauled engine carries forward all previous time in the engine logbook—a factory rebuilt or factory remanufactured engine goes back to zero time.
British warbird pilot, Mark Levy, was part of a 21-airplane formation in the annual airshow at Duxford, England, when the P-51 he was flying had a partial engine out. Levy recorded the entire event on a pair of point-of-view video cameras, and he shared the images, as well as his lessons learned, in a candid discussion with AOPA Air Safety Institute Executive Director Richard McSpadden.