15.4. Influence of aircraft configuration onto its aerodynamic characteristics
The wing setting relatively to fuselage essentially influences onto the aerodynamic, weight, operational and economic characteristics of the aircraft.
Let's consider main virtues and shortages by everyone from the schemes of mutual arrangement of a wing and fuselage.
The aircraft made by the low-wing configuration has the following advantages: it allows to receive the improved take-off and landing characteristics due to more effective influence of ground proximity, and, also, capability of increasing of high-lift devices area due to ventral wing part; the design of glider and service of aggregates installed on the wing become simpler.
Imperfections
of this configuration are the following:
decreases due to interference of wing and fuselage,
increases, the lift-to-drag ratio decreases, the falling of foreign
objects is possible at takeoff and landing at engines installation on
the wing.
Advantages
of high-wing configuration: lift-to-drag ratio is higher on
than for low-wing configuration with other conditions being equal due
to decreasing of aerodynamic interference; the characteristics of
longitudinal stability at high angles of attack are better in
comparison with the characteristics of the low-wing configuration; in
case of engines installation on the wing, the probability of outside
objects falling from runway surface essentially decreases, that
allows more successfully use high-wing aircraft on unpaved runways.
The
disadvantages of the configuration are worsening of lateral stability
characteristics at high angles of attack, when vertical tail falls
into the wake jet from the wing, that demands necessity of vertical
tail area increasing on
in comparison with vertical tail area of low-wing configuration.
Weight of
high-wing construction is more, than low wing one. In particular,
weight of a heavy high-wing-airplane with main landing gears fixed on
the fuselage, exceeds the weight of low-wing airplane on
.
The operating economy of passenger high-wing aircraft is a little bit lower, than of low-wing one because of losses in weight.
The midwing airplane, from a point of view of an aerodynamic interference, has the greatest advantages. However, this scheme is not applied to the aircraft of mean seating capacity because the wing should pass through the passenger compartment, forming ledges or cavities on the compartment floor. The midwing configuration is used on some wide-fuselage aircraft (airbuses), which wing passes not through the passenger compartment, but in space between the upper and lower decks.
Now majority of passenger aircraft has the low-wing configuration. For cargo and cargo-passenger aircraft the high-wing configuration is more preferable in many cases.