[away3d] MAX3DS object problem

[eaccount]

jeep = Max3DS.load("images/jeep1.3ds", {texturePath:"images/",
name:"jeep", loadersize:100});
            jeep.rotationX = -68;
            jeep.rotationZ = 180;
            jeep.addOnSuccess(initJeep);
            view.scene.addChild(jeep);
jeep.addOnMouseDown(jeepdown)

or
jeep.handle.addOnMouseDown(jeepdown)

public function jeepdown(e:MouseEvent3D)
{
      trace("mousedown");
}

can not Listener the MouseDown event,
 jeepdown(e:mouseevent3D)  not work? why?