PURPOSE: To increase the stability of a helicopter on board a ship by supporting the helicopter on both the sides of a lengthwise center plane when the helicopter is placed on a platform, through a front wheel type drive gear by the stabilizing wheel of an auxiliary stable gear composed of two lateral stabilizers.

CONSTITUTION: An auxiliary gear composed of two lateral stabilizers 13 is provided on the lower part of a hilicopter body 1, and rigid supporters 17 for supporting stabilizing wheels 16 in the lower ends are protruded on both the sides of the body 1 in use positions, in a direction deflecting toward an auxiliary under carriage 2 to the main and lateral under carrige 6 of a front wheel type landing gear, and biased to both the side laterals of the center lengthwise plane PP of a hilicopter. The stabilizing wheels 16 are supported on a platform moving on both the sides of the lengthwise center plane PP, when the helicopter is placed on the platform on board a ship by the front wheel type landing gears 2 and 6, and thus the stability of the helicopter on board the ship can be increased.