From the Super Mario Wiki
In this form, the Yoshi can fly around the level until he reaches the Yoshi Block or until his time as a helicopter runs out. As with other transformations, the latter will send him back to the position where touched the Morph Bubble. The Yoshi Helicopter can be controlled with the D-pad. Touching an enemy while in this form will make the Yoshi fall a short distance, unable to be controlled, which can cause the player to lose time and a life if he falls into an abyss. The form returns in Yoshi's Island DS, and is set to return in Yoshi's New Island.
In volume 14 of the Super Mario-Kun, Yoshi eats a Morph Bubble and turns into the Yoshi Helicopter. He carries Mario and Luigi; Mario then makes the Yoshi Helicopter eat a Watermelon. This causes the Yoshi Helicopter to spit seeds at Kamek, the Toadies, and even Baby Mario who was getting carried by the Toadies in the process. Unlike in the games, the Yoshi Helicopter runs on a timer and ends whenever, causing Mario, Luigi, and Yoshi to fall to the ground.
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