A wheel assembly for a model airplane includes a motor, a drive gear unit, a linkage, and a wheel unit. The drive gear unit includes a driven gear meshing with a driving gear connected fixedly to a spindle of the motor, and an output gear driven indirectly by the driven gear. The linkage includes a swing rod connected fixedly to the output gear, and a link connected pivotally to the swing rod. The wheel unit has a pivot end connected pivotally to an airplane body, a wheel-mounting end mounted with at least one wheel, and an intermediate portion connected pivotally to the link. The motor is operable to activate the drive gear unit so as to rotate the wheel unit between a generally horizontal idle position, and an upright landing position.