In a 3-umpire system, who should the plate umpire appeal check swing attempts to with a runner on second?

In a 3-umpire system, when a check swing occurs with a runner on second base, it is the responsibility of the plate umpire to appeal the check swing to the third base umpire. This is because the third base umpire has a clear line of sight to the batter's swing as they are positioned properly to observe the play unfolding. During a check swing, the focus is on determining whether the batter actually swung at the pitch, and the third base umpire is in the best position to make that judgment call.

Additionally, the first base umpire and field umpire may be occupied with other aspects of the game, such as monitoring the base runners and other plays in their respective areas. Thus, appealing to the third base umpire ensures that the call is made effectively and reduces the risk of confusion among the umpires regarding their responsibilities. This practice reinforces the proper coordination among umpires during a game, ensuring fairness and accuracy in officiating.