Before attempting to start a radial engine that has been shut down for more than 30 minutes,

The correct approach before attempting to start a radial engine that has been shut down for more than 30 minutes is to turn the propeller by hand three to four revolutions in the normal direction of rotation to check for liquid lock. This practice is crucial because, over time, fuel can accumulate in the cylinders if the engine has been sitting idle. If liquid fuel is present, it can create a condition known as liquid lock where the piston cannot compress the liquid during the start cycle, potentially causing severe engine damage.

By rotating the propeller in the normal direction, you're not only enabling the engine to clear any fuel that may have pooled in the cylinders, but you're also ensuring that the engine's internal parts are moving freely, helping to prevent any potential damage caused by stagnant fuel. This preventive step contributes to a safer and more reliable starting procedure.

In contrast, turning the propeller in the opposite direction of normal rotation is not a standard procedure and does not address the risks associated with liquid lock effectively. Activating the ignition switch before engaging the starter can lead to risk if there is a fuel issue, as the engine could start unexpectedly. Checking fuel levels is important, but it does not directly address the potential issue of liquid lock that can occur after a period