Civil jet aircraft performance

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Civil jet aircraft performance
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Four forces of flight
Net thrust from the engines
a angle of attack V velocity
Newtons second law
resulting force parallell to the flight path
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Aerodynamic equations

• LLift qSCL N
• DDrag qSCD N
• q dynamic pressure N/m²
• S reference wing area m²
• CL coefficient of lift CL f(a,Re,M)
• CD coefficient of drag CD f(a,Re,M)

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Reference wing area
The area is considered to extend without
interruption through the fuselage and is usually
denoted S.
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Lift versus angle of attack
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(No Transcript)
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The ISA Atmosphere
From lecture 5
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Equations
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Lift equation
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Drag equation
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Drag polar
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High speed drag polar
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A flight consists of

• Taxi
• Take off
• Climb
• Cruise
• Descent
• Approach and landing
• Diversion to alternate airport?

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Cruise

• For an airplane to be in level, unaccelerated
  flight, thrust and drag
• must be equal and opposite, and the lift and
  weight must be equal and
• opposite according to the laws of motion, i.e.
• Lift Weight mg
• Thrust Drag

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Range
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Range
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Breguet range equation
For a preliminary performance analysis is the
range equation usually simplified. If we assume
flight at constant altitude, M, SFC and L/D the
range equation becomes
which is frequently called the Breguet range
equation
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Breguet range equation

• The Breuget range equation is written directly in
  terms of SFC. Clearly maximum range for a
  jetaircraft is not dictated by maximum L/D, but
  rather the maximum value of the product M(L/D) or
  V(L/D).

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Breuget range equation

• From the simplified range equation, maximum range
  is obtained from
• Flight at maximum
• Low SFC
• High altitude, low ?
• Carrying a lot of fuel

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Range
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Endurance

Endurance is the amout of time that an
aircraft can stay
in the air on one given load of fuel
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Endurance