Positioning of the camera under the bottom of the helicopter allows achievement of a wide panorama. If the camera on the controlled gimbal is installed under the bottom of the helicopter, the undercarriage must be both increased and retractable so as not to disturb the camera. The undercarriage "OpenButtom" is produced out of the aluminum profile and substitutes the common undercarriage. The mass of the ordinary undercarriage, attributed to the 50-90 class, amounts to 100-150 g. The mass of this particular undercarriage is 390 g, including the servo. Availability of the standard servo (modification - 180 degrees) is quite sufficient for controlling the undercarriage, but fastening with the help of the extra bearing from outside is necessary so that the body of the servo would endure the possible jerks at the moment of landing.
Aleksey Zaitsevsky, 2009, http://www.myresearch.company