Download An Introduction to Basic Principles of Atmospheric Flight Mechanics

Lecture – 7
An Introduction to Basic Principles of
Atmospheric Flight Mechanics
Dr. Radhakant Padhi
Asst. Professor
Dept. of Aerospace Engineering
Indian Institute of Science - Bangalore
Aircraft Designs
Dr. Radhakant Padhi
Asst. Professor
Dept. of Aerospace Engineering
Indian Institute of Science - Bangalore
First to Fly
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Wright Brothers
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Commercial Aircrafts
z
z
z
z
z
z
High Lift/Drag ratio
High fuel efficiency
High reliability & safety
requirements
Good handling quality
and passenger comfort
All weather operational
capability
Speed and agility
(maneuverability) are
not critical
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Geometry of Conventional Aircrafts
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Tailless Aircraft
z
On the tailless aircraft the pitch controls and roll controls
must both be on the wing. There can be separate
elevators and ailerons or they can be combined into one
set of controls known as Elevons and still usually has a
vertical Fin with a rudder
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Canard Aircraft
z
z
z
Horizontal stabilizer and elevators are in front.
Advantage: Better control characteristics (including
elimination of the non-minimum phase behavior)
Drawback: Disturbed flow pattern over the body, good
aerodynamic modeling is difficult.
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Force Balance in Flying Vehicles
Dr. Radhakant Padhi
Asst. Professor
Dept. of Aerospace Engineering
Indian Institute of Science - Bangalore
Basic Force Balance
z
Weight
z
Lift
z
Drag
z
Thrust
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Lift
z
Lift is generated by differential pressure
on upper and lower side of the wing
Lift
Lift
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Lift
⎛1
2⎞
L = q S CL = ⎜ ρV ⎟ S CL
⎝2
⎠
ρ(h) = atmospheric density (a function of height)
V = relative velocity of air
S = wetted surface area
CL = coefficient of lift
⎛1
2⎞
q = ⎜ ρV ⎟ : Dynamic Pressure
⎝2
⎠
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Dynamic pressure
Total pressure of any fluid
= static pressure + dynamic pressure
1
2
= ρ gh + ρV
2
Dynamic pressure of a fluid represents its kinetic energy
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Atmospheric density
ρ = ρ0e
⎡ g ( h − h0 ) ⎤
−⎢ 0
⎥
⎣ RT
⎦
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Angle of attack
AOA
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Coeff. of Lift vs Angle of attack
Stall
Region
⎛1
2⎞
L = ⎜ ρ V ⎟ S CL
⎝2
⎠
Lift coefficient
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Drag
⎛1
2⎞
D = ⎜ ρV ⎟ S CD
⎝2
⎠
CD = Coefficient of drag
= profile drag + induced drag
= CD0 + K CL2
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Mach Number M = V / C
V = velocity of object relative to medium
C = velocity of sound in the medium
= velocity of sound in air = 340 m/s at 250 C
M<1
M=1
0.8 < M < 1.2
1.2 < M < 5
M>5
Subsonic
Sonic
Transonic
Supersonic
Hypersonic
γP
C = γ RT =
ρ
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Drag vs Mach number
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Drag
z
Skin friction drag
z
Pressure drag
z
Induced drag
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Skin friction drag
z
It is caused by the interaction of the air particles against
the surface of the aircraft. For the airplane, skin fiction
drag can be reduced, by keeping an aircraft's surface
highly polished and clean.
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Form or Pressure drag
z
z
Pressure drag is
caused by the
separation of air that is
flowing over the aircraft
or airfoil.
Note: New generation
cars are designed to
reduces pressure drag,
which leads to better
mileage
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Induced drag
z
Induced drag is the
drag created by the
vortices at the tip of
an aircraft's wing.
z
Induced drag is more
while maneuvering
due to more flow
separation over the
entire body.
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Thrust
z
z
Thrust is produced by engines, which
counteracts the drag and hence the
airplane moves in forward direction.
Types of engines
• Propeller
• Turboprop
• Turbofan
• Turbojet
• Ramjet
• Scramjet
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Propeller engine
Spitfire: Used by England in second world war.
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Turboprop engine
Used by ATR flights
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Turbofan engine
Airbus A380 – Largest Passenger Aircraft
Engine Used: Either Rolls Royas or GE
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Turbofan engine with afterburner
LCA - Light Combat Aircraft
Kaveri: An indigenous engine under development
at GTRE (Gas Turbine Research Est.) under DRDO
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Ramjet Engines
Brahmos: A supersonic cruise missile developed jointly by
India and Russia.
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Scramjet
X-43 is an experimental vehicle of NASA which
used scramjet propulsion to reach up to MACH 9
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Moment Balance in Flying Vehicles
Dr. Radhakant Padhi
Asst. Professor
Dept. of Aerospace Engineering
Indian Institute of Science - Bangalore
Basic Force Balance
z
Weight
z
Lift
z
Drag
z
Thrust
z
Side force
Side force
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Basic Moment Balance
z
Rolling
z
Pitching
z
Yawing
Y
X
Z
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Ailerons
Roll
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Aileron
Roll
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Elevator
Pitch
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Elevator
Pitch
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Rudder
Yaw
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Rudder
Yaw
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Sensors
z
z
z
z
z
z
Altimeter: Height above sea level
Air Data System: Airspeed, Angle of
Attack, Mach No., Air Temperature etc.
Magnetometer: Heading
Accelerometers: Translational motion
of the aircraft in the three axes
Gyroscopes: Rotational motion of the
aircraft in the three axes
GPS: Accurate position, ground speed
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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Actuators
ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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ADVANCED CONTROL SYSTEM DESIGN
Dr. Radhakant Padhi, AE Dept., IISc-Bangalore
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