Cruise Performance

Introduction:

Understanding the Drag Curve:

  • As seen in Figure 5-6, at some given airspeed, total drag is at its minimum amount
  • In figuring the maximum range of aircraft, the thrust required to overcome drag is at a minimum if drag is at a minimum
  • The minimum power and maximum endurance occur at a different point

Maximum Range:

  • Best range airspeed is an airspeed that should allow an aircraft to fly the farthest distance

Maximum Endurance:

  • Best endurance airspeed is an airspeed that allows for an aircraft to remain flying for the most amount of time
  • As seen in Figure 5-6, at some given airspeed, total drag is at its minimum amount
  • In figuring the maximum range of aircraft, the thrust required to overcome drag is at a minimum if drag is at a minimum
  • The minimum power and maximum endurance occur at a different point

Applying Maneuvering Speed to Cruise:

  • Maneuvering speed, or Va, is an airspeed below which full deflection of the control surfaces should not cause damage
  • If approaching bumpy weather, slowing to Va before penetrating turbulence should be considered

Wind Impacts on Cruise Flight:

  • Wind direction and intensity at various cruise altitudes are an important consideration to determine cruise performance
  • Winds aloft are the most direct means to plan for winds at cruise altitudes along the route of flight
  • Headwinds increase flight time and therefore fuel burn, reducing range, while tailwinds do just the opposite

Icing Impacts on Cruise Flight:

  • When encountering icing, additional power may be necessary to overcome the increase in drag
  • Airspeed may bleed off quickly (one example saw 50 knots in under 1 minute)
  • See also: Stall and Climb Performance

Conclusion:

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References: