7 Flight Mystery and Aerodynamic Principles
521
engine stalls and the aircraft cannot take off normally, the aircraft needs to
slow down. Obviously the greater the lift-off speed, the longer the distance
required for the deceleration, the safety requires the actual runway length to
be about twice the takeoff length, so the takeoff speed has a decisive relationship to the length of the runway. Actually, for the sake of safety and to
reduce the cost of airport runways, it is reasonable to reduce the takeoff and
landing speed of large airliner as much as possible. If the wing area is not
reduced, then it will cruise at a high speed in the area of takeoff and landing.
At this time, the frictional drag of the wing is too large, and the aircraft
cannot achieve economic cruising.
The design of high-efficiency lifting devices for large airliner remains a
challenging issue worldwide. Large airliner requires complex multi-element
high-lift systems to meet aircraft takeoff and landing performance requirements. In today’s competitive civil aircraft market, the design trend of large
airliner requires more efficient lifting devices to maximize the lift coefficient
and lift-to-drag ratio at a given angle of attack and flap deflection angle. The
design of the lifting device belongs to a multi-objective, multi-technology
integrated design problem. The overall technical requirements of the aircraft
must be met, including aircraft performance, safety, reliability, maintainability, noise, etc. In terms of aerodynamics, the aircraft needs to meet the
requirements for takeoff, short landing distance, and climb gradient; In terms
of structure, it requires less components, lightweight, simple connection and
sufficient strength and rigidity; in terms of maneuverability, it requires easy to
maintain, reliable, low cost, and meet the requirements of damage tolerance.
Research on the lifting device has been carried out long ago in foreign
countries. First of all, in the high-lift design, there are quite a lot of theoretical and experimental research, which provides a direct theoretical basis and
data support for the design of the lifting device. The aerodynamicist A.M.O.
Smith of Douglas Corporation in the U.S. published the paper “High Lift
Aerodynamics” to reveal the high-lift mechanism of multi-element wing (as
shown in Fig. 7.100 and Fig. 7.101) in 1975.
From the aerodynamic point of view, A.M.O. Smith et al. carried out a
lot of basic research on the mechanism of high lift and the flow of multielement wing flow, and carried out in-depth excavation of the nature of
the flow to maximize the lift. For two-dimensional multi-element airfoil,
various flow phenomena that may occur include boundary layer transition,
shock/boundary layer interference, wake/boundary layer blending, boundary
layer separation, laminar separation bubble, separated concave angular flow,
the streamline is greatly curved, etc.
521
engine stalls and the aircraft cannot take off normally, the aircraft needs to
slow down. Obviously the greater the lift-off speed, the longer the distance
required for the deceleration, the safety requires the actual runway length to
be about twice the takeoff length, so the takeoff speed has a decisive relationship to the length of the runway. Actually, for the sake of safety and to
reduce the cost of airport runways, it is reasonable to reduce the takeoff and
landing speed of large airliner as much as possible. If the wing area is not
reduced, then it will cruise at a high speed in the area of takeoff and landing.
At this time, the frictional drag of the wing is too large, and the aircraft
cannot achieve economic cruising.
The design of high-efficiency lifting devices for large airliner remains a
challenging issue worldwide. Large airliner requires complex multi-element
high-lift systems to meet aircraft takeoff and landing performance requirements. In today’s competitive civil aircraft market, the design trend of large
airliner requires more efficient lifting devices to maximize the lift coefficient
and lift-to-drag ratio at a given angle of attack and flap deflection angle. The
design of the lifting device belongs to a multi-objective, multi-technology
integrated design problem. The overall technical requirements of the aircraft
must be met, including aircraft performance, safety, reliability, maintainability, noise, etc. In terms of aerodynamics, the aircraft needs to meet the
requirements for takeoff, short landing distance, and climb gradient; In terms
of structure, it requires less components, lightweight, simple connection and
sufficient strength and rigidity; in terms of maneuverability, it requires easy to
maintain, reliable, low cost, and meet the requirements of damage tolerance.
Research on the lifting device has been carried out long ago in foreign
countries. First of all, in the high-lift design, there are quite a lot of theoretical and experimental research, which provides a direct theoretical basis and
data support for the design of the lifting device. The aerodynamicist A.M.O.
Smith of Douglas Corporation in the U.S. published the paper “High Lift
Aerodynamics” to reveal the high-lift mechanism of multi-element wing (as
shown in Fig. 7.100 and Fig. 7.101) in 1975.
From the aerodynamic point of view, A.M.O. Smith et al. carried out a
lot of basic research on the mechanism of high lift and the flow of multielement wing flow, and carried out in-depth excavation of the nature of
the flow to maximize the lift. For two-dimensional multi-element airfoil,
various flow phenomena that may occur include boundary layer transition,
shock/boundary layer interference, wake/boundary layer blending, boundary
layer separation, laminar separation bubble, separated concave angular flow,
the streamline is greatly curved, etc.