CYLINDER ASSEMBLY

TCM cylinder assembly design consists of a cast aluminum alloy head and a steel barrel. Both components are designed with cooling fins to dissipate heat as air flows around them. Cylinder heads have been improved over the years to keep pace with engine improvements greatly increasing cylinder service life. The cylinder barrels have been made from aircraft quality steel forgings for the past several decades. Initially, the finished machined barrels were only heat treated as there was no requirement for a case hardened bore surface in the early days of low compression, naturally aspirated engines. However, with the advent of turbocharging, higher compression ratios with the associated higher operating temperatures, not forgetting the requirement for extended TBOs Teledyne was compelled to introduce nitrided cylinder bores.

Cylinder assemblies and their related components are subjected to a severe operating environment. Although many operational factors can contribute to the deterioration of a cylinder's durability, the loads resulting from combustion pressure and operating temperatures are the largest. The number of engine starts, or thermal cycles is also a contributing factor. Corrosion of the cylinder head and rusting of the cylinder barrel can destroy the durability of a cylinder rapidly.

Over the typical range of operating temperatures, the steel cylinder barrel is not much affected. However, the cast aluminum cylinder head strength can be compromised if operated at maximum temperature for unusually long periods of time. Clearly, for good durability of cylinder assemblies, it is necessary to minimize operation at maximum temperatures, otherwise cracking may occur. High temperature, which increases cylinder loads, is the biggest enemy your cylinder assembly can have. We have observed over the years that inter-cylinder baffles and the perimeter baffles are much neglected accessories. These items are commonly found to be worn, missing, bent and cracked which may result in one or more cylinders operating at unusually high temperatures. Just remember, keeping a cool head is the key to extended cylinder life.

The horizontally opposed engine of today is considerably different from its predecessors. One of the important differences is the cooling requirements of the modern air cooled engine. As greater performance demands, mainly more horsepower, higher efficiency and greater reliability, were placed on the horizontally opposed engines, the requirement for cooling could no longer be met by velocity cooling. Cowlings were placed around the engines and baffles were installed between the cylinders so air could be directed around the entire area of the cylinders. Thus pressure cooling was born and the results were superior for uniform engine cooling.

The baffling installed on the engine of today is the result of considerable study. Special wrap around baffles now guide the cooling air completely around the cylinder heads and barrels. On a pressure aircooled system it is important to understand that to control the airflow from the propeller and ram air there has to be a pressure differential inside the cowling. Peripheral baffles with rubber seals are installed on the engine to provide this pressure differential. On most installations this pressure differential is around 4 to 6 inches of water pressure.

Heat related problems have become more prevalent with the fleet of aircraft getting older and more power upgrades being made. Therefore, it is very important to make sure the baffles are maintained properly.

Engine accessories consist of components such as magnetos, alternator, starter, fuel pump, etc. These accessories are cooled with airflow the same as the engine. This is accomplished by direct ram air flow into the nacelle area by air scoops and hoses routed directly to the accessory.

It is very important to make sure the air ducts are routed and secured properly. Proper cooling of the accessories is required to prevent failure and to get good service life.