Task F: Performance and Limitations

Here's a look at the specific knowledge areas covered in this task:

 

PA.I.F.K1 Elements related to performance and limitations by explaining the use of charts, tables, and data to determine performance

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What you need to know: You must understand how to use the charts, tables, and data provided by the manufacturer to predict your airplane's performance. The Pilot's Operating Handbook (POH) or Airplane Flight Manual (AFM) is the primary source for this information.

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What these charts contain: The performance section (usually Section 5) of the POH/AFM includes charts, tables, and graphs that provide information on:

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Takeoff and climb performance: This includes takeoff distance over an obstacle, climb rate, and climb angle.

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Cruise performance: This details fuel consumption, true airspeed, and range at various altitudes and power settings.

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Landing performance: This includes landing distance over an obstacle.

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Stall speeds: These are provided for different aircraft configurations (like flaps up or down).

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How they are used: You use these charts to determine things like the runway length needed for takeoff and landing, the amount of fuel required for a trip, and the time it will take to reach your destination. This often involves using methods like direct reading and interpolation to find values that fall between those listed on the charts.

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Important Note: It's critical to remember that the performance data in the POH/AFM is typically gathered during test flights conducted in a brand new aircraft, flown by highly skilled test pilots, under normal operating conditions and using average piloting skills. This means your actual performance may differ from the published numbers, especially in an older airplane or under adverse conditions. You should not plan on getting the exact performance stated in the charts.

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PA.I.F.K2 Factors affecting performance, including:

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An airplane's performance is influenced by many factors. You need to understand how each of these impacts your flight planning and execution.

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a. Atmospheric conditions: The condition of the air is a major factor.

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Temperature and Air Pressure: These determine the density of the air, which is often expressed as density altitude. High temperatures and low air pressure result in less dense air, leading to reduced performance. This means higher takeoff and landing speeds and distances, and a reduced climb rate.

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Wind: Wind significantly affects takeoff, landing, and en route performance. A headwind improves takeoff and landing performance (shorter distances) but decreases groundspeed in cruise. A tailwind degrades takeoff and landing performance (longer distances) but increases groundspeed in cruise. Crosswinds require specific techniques and can also affect takeoff and landing performance.

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Other Weather: Phenomena like windshear, turbulence, and microbursts can severely impact performance, especially during critical phases of flight like takeoff and landing. Formation of carburetor ice or airframe ice can also reduce performance.

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b. Pilot technique: The pilot's skill and how they operate the aircraft directly affect performance. As mentioned, performance charts are based on test pilots. Your ability to fly the airplane efficiently, use controls properly, manage systems, and make sound decisions contributes to achieving the best possible performance under given conditions. This involves good airmanship and situational awareness.

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c. Airplane configuration: How the airplane is configured impacts its performance. This includes the position of the landing gear (up or down), flaps (extended to various settings), and propeller pitch. Systems like anti-icing or deicing can also affect aerodynamics and add weight, reducing performance. Operating within published V-speeds, such as VFE (max flap extended speed) or VFO (max flap operating speed), is part of managing configuration limitations.

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d. Airport environment: The physical characteristics of the airport and surrounding area affect performance.

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Runway/Landing Surface: The length, width, and slope of the runway are critical. The surface condition (paved, grass, soft field, rough water for seaplanes) also affects takeoff and landing distances.

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Obstacles: Obstacles in the takeoff or approach path must be considered when determining required runway length and climb/descent performance.

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Airport Elevation: Higher elevation airports have lower air pressure, leading to reduced aircraft performance similar to high temperatures.

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e. Loading (e.g., center of gravity (CG)): The distribution of weight within the aircraft determines the location of the Center of Gravity (CG). The CG must remain within specific forward and aft limits during all phases of flight. An airplane loaded with the CG too far aft can be unstable, while a forward CG limit can reduce elevator authority and make landing more difficult. CG location affects pitch stability and elevator effectiveness, which in turn affects the ability to achieve desired performance speeds and attitudes.

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f. Weight and balance: The total weight of the aircraft is one of the most significant factors affecting performance. Operating the aircraft over its maximum allowable weight is prohibited and severely degrades performance in almost every aspect. An overloaded aircraft will have:

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Higher takeoff and landing speeds.

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Longer takeoff and landing runs.

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Reduced rate and angle of climb.

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Lower maximum altitude.

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Shorter range and reduced cruising speed.

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Reduced maneuverability.

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Higher stalling speed. You must understand how to compute weight and balance and ensure the aircraft remains within limits throughout the flight.

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PA.I.F.K3 Aerodynamics

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What you need to know: You must understand the fundamental principles of how air interacts with the airplane's surfaces to produce the forces necessary for flight.

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The Four Forces of Flight: The primary forces acting on an airplane are Lift, Weight, Thrust, and Drag. These forces are in a state of equilibrium during unaccelerated flight.

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Lift: The aerodynamic force that opposes weight and is produced by the dynamic effect of air acting on the airfoil. Lift is generated by the difference in air pressure above and below the wing, often explained by Bernoulli's Principle (faster air = lower pressure) and Newton's Third Law (action/reaction - wing pushing air down results in lift up).

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Weight: The force of gravity acting on the airplane, passengers, and cargo, assumed to be concentrated at the Center of Gravity (CG).

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Thrust: The forward force produced by the engine and propeller or rotor, which opposes or overcomes the force of drag.

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Drag: The aerodynamic force that opposes the airplane's motion through the air. It consists of Parasite Drag (resistance from non-lifting parts like fuselage, landing gear) and Induced Drag (drag created as a byproduct of lift). Drag increases with speed (parasite drag) and also increases significantly at low speeds when a high Angle of Attack (AOA) is required to maintain lift.

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Angle of Attack (AOA): The angle between the wing's chord line and the relative wind. Understanding AOA is crucial because lift is directly related to AOA (up to the critical AOA).

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Stalls: A stall occurs when the wing exceeds its critical Angle of Attack, regardless of airspeed, and the airflow separates from the upper surface, resulting in a rapid decrease in lift. Your knowledge should include the aerodynamics associated with stalls in different airplane configurations and how factors like speed, load factor, weight, CG, attitude, and yaw effects influence stalls. You should know how to recognize the indications of an impending stall and a full stall using sight, sound, or feel.

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P-Factor: Also known as asymmetric thrust, this is a left-turning tendency caused by the descending propeller blade on the right side of the airplane creating more thrust than the ascending blade on the left, especially at high angles of attack and high power settings.

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Load Factor: The ratio of the total load supported by the airplane's wing to the actual weight of the airplane. Load factor increases in maneuvers like turns and during turbulence, increasing the stall speed.

To pass the practical test for this task, you'll need to demonstrate your understanding through both oral questioning and practical application. You might be asked to:

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Explain how atmospheric conditions or weight affect takeoff distance.

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Calculate performance data (like takeoff distance or fuel burn) using charts from a sample POH/AFM, possibly requiring interpolation.

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Explain the effect of extending flaps or lowering the landing gear on performance.

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Discuss the four forces of flight and how they change during different flight conditions.

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Explain why an airplane stalls and factors that influence stall speed.

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Compute weight and balance and determine if the aircraft's loading is within limits.

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Identify and mitigate risks associated with using performance data or operating near airplane limitations.

Being able to apply this knowledge to real-world scenarios is key, as the evaluator may use scenarios during the oral portion of the test. Remember that the ACS is a testing document, so supplementing your study with reference materials like the Airplane Flying Handbook (FAA-H-8083-3) and the POH/AFM for your specific aircraft is highly recommended.

 

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