The mechanical innovations lead to aerodynamic advantages.
Description:
Telescopic Wing:
The telescopic wing is an alternative to sophisticated high lift devices (e.g. slotted fowler flaps). In operation, it is treated like a "span flap" rather a conventional "chord flap". It is used at only low speeds and has a maximum speed limit just as a convention flap.
Swept Tail:
The swept tail is a result of connecting the horizontal stabilizer to the back of the fuselage using the straightest, most direct, structure. This is done rather than extending the fuselage horizontally and attaching the tail on top of it.
The vertical tail volume (area times moment arm) is generous, although visually deceiving. The height of the rudder is typical of "T" tail configurations so that the roll couple is reasonable.
Inboard Engines:
Since the engines are mounted inboard and the propellers are driven by belts, there are no engine nacelles. The only disturbance to the airflow is the small bump on the trailing edge of the wing required to house the belt pulley.
Advantages:
Telescopic Wing
High lift at low speeds without the drag penalty of flaps.
Increased aspect ratio at low speeds which improves efficiency - unlike conventional flaps.
The retracted configuration has much higher stiffness and resistance to bending and twist (i.e. flutter resistant) than a conventional wing.
The retractable wing is lighter than a conventional wing with the same stall speed, and maximum speed, and strength requirements
Swept Tail
The straight line from the fuselage to the tail provides the most rigid structure possible, to combat high speed flutter.
The tail design is structurally most efficient by attaching directly to the strongest part of the aircraft.
The sweep of the tail provides generous ground clearance for high angle of attack takeoffs and landings.
The lower part of the rudder contributes to yaw control force which lowers the vertical rudder volume (area times moment) minimizing roll resulting from rudder application ("roll coupling").
The aft swept rudder hinge line provides beneficial pitch up moment from rudder application to counteract the usual pitch down tendency.
Inboard Engines
There are no engine nacelles to detract from maximum lift by disrupting the airflow across the wing.
There are no engine nacelles to create drag.
The airflow through the propellers is not disturbed by large engine nacelles.
