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Performance Planning

Objectives​

Motivations​

Timings​

45 minutes

Format​

  • Whiteboard

Elements​

Performance Planning Concepts​

  • Atmosphere
    • Density decreases as we ascend (18,000', 1/2 as dense as S.L.)
    • The standard atmosphere: ~2° per 1000'
    • The standard day: 15° C and 29.92" Hg
    • Normally aspirated airplanes lose power as they climb
  • Aerodynamic changes with different air density
    • Production of lift is reduced with higher temperatures and lower pressures
    • Air density is low, a higher speed is needed to create the same lift
    • Turbocharging increases engine power, but not propeller efficiency
    • Indicated airspeed does not change
  • Pilot technique
    • Correct leaning procedures and mixture setting
    • Correct short-field takeoff technique
  • Aircraft performance charts
    • Used to predict aircraft performance for flight planning
    • Based on a new airplane, engine, propeller
    • May use pressure altitude and temperature, or density altitude
  • Types of Altitudes
    • Barometric pressure: Set the Kollsman window on the altimeter
    • Temperature: Ambient temperature as observed
    • Pressure altitude: Height in the ISA where current pressure is found
    • Density altitude: Height in the ISA where the current pressure is found, plus any correction for temperature
  • Types of Airspeeds
    • Indicated airspeed (IAS): Read from altimeter
    • Calibrated airspeed (CAS): Calibrated for position/instrument errors
      • At slow airspeeds this may be several knots off
    • True airspeed (TAS): CAS corrected for altitude and nonstandard temperature
    • Ground speed (GS): Actual speed over the ground
      • TAS adjusted for wind

Performance Charts and Calculations​

  • Computing pressure altitude
    • Current altitude+(29.92−Current altimeter setting)∗1000\text{Current altitude} + (29.92 - \text{Current altimeter setting}) * 1000
    • Example:
      • Field elevation is 720' MSL
      • Current altimeter setting is 29.82" Hg
      • Answer: 720+(29.92−29.82)∗1000=820720 + (29.92 - 29.82) * 1000 = 820
  • Airspeed Calibration Chart (T182 POH pg. 77)
  • Alternate Static Source (T182 POH pg. 78)
  • Stall speed (T182 POH pg. 80)
  • Wind Component Graph (T182 POH pg. 81)
  • Takeoff Distance (T182 POH pg. 82)
    • Sample scenario:
  • Time, Fuel, Distance to Climb - Max Rate (T182 POH pg. 85)
    • Sample scenario: Climb from airport @ 2000' to 8000', temperature aloft 8°C
      • Base values:
        • 9−2=7 minutes9 - 2 = 7 \text{ minutes}
        • 3.6−0.9=2.7 gallons3.6 - 0.9 = 2.7 \text{ gallons}
      • Temperature is 8−−1=9°C8 - -1 = 9\degree \text{C}: 9% increase in time/fuel
        • 2.7∗1.09=2.9 gallons2.7 * 1.09 = 2.9 \text{ gallons}, plus two gallons for taxi+takeoff 4.9 gallons
        • 7∗1.09=7.6 minutes7 * 1.09 = 7.6 \text{ minutes}
  • Cruise Performance - 8000 (T182 POH pg. 90)
    • Sample scenario: Cruising at 2200 @ 23", 8000', temperature 8°C
      • Airspeed:
        • 134 vs 133, conservatively take 133
      • GPH:
        • Base values 12.6 @ -1°, 12.0 gph @ 19°
        • Linearly interpolate:
          • (8−−1)/(19−−1)=9/20=0.45(8 - -1) / (19 - -1) = 9 / 20 = 0.45
          • 12.6+(12−12.6)∗0.45=12.33 GPH12.6 + (12 - 12.6) * 0.45 = 12.33 \text{ GPH}

References​