In this report is clearified the relation between the lift coefficient and the dihedral angle of the main-wing and the vertical tail plane for a airplane given a shape of the fuselage and a plane form of the main-wing, to be able to turn steadily at a small bank angle and with all control surfaces fixed. Here we considered the balancing of the moments of air forces about the vertical axis and longitudinal axis. In this consideration for simplicity the air forces are assumed two-dimensional. From this relation the suitable values of the dihedral angle and the vertical tail plane area and position of the airplane to be designed, will be evaluated rather simply, by refering to these values of many excellent airplanes already in practical service.
As commuter air-transport vehicles to be used over both land- and water-surfaces, hybrid-airship has been noticed recently. The best one seems to be a hybrid between airship and helicopter. It relieves the serious defects before hybridization, significantly. The development of “Helistat” is now substantially stopped, mainly because of catastrophic vibration problem. Presented here is named “Heliship” which is a combination of a tandem-roter helicopter (at center) and two airship (both sides). Failure of one engine is less severe than the Helistat. Insufficient roll-control power at hover would be overcome through appropriate operating procedure.