Performance - Introduction — Page 136, Lesson 157

We're starting the Performance section of your ATPL syllabus, and I want to walk you through the definitions that open this chapter. These aren't just vocabulary words — they're the precise, legally-binding terms you'll use in every performance calculation and every operational decision. Let's go through them in order. First, an Instrument. This is a device using an internal mechanism to show visually or aurally the attitude, altitude, or operation of an aircraft or aircraft part. It includes electronic devices for automatically controlling an aircraft in flight. So when we say "instrument," we mean anything from your attitude indicator to your autopilot system — anything that displays information or automatically controls the aircraft. Next, Landing Distance Available. This is the distance from the point on the surface of the aerodrome above which the aeroplane can commence its landing, having regard to the obstructions in its approach path, to the nearest point in the direction of landing at which the surface of the aerodrome is incapable of bearing the weight of the aeroplane under normal operating conditions, or at which there is an obstacle capable of affecting the safety of the aeroplane. In short, it's the length of runway from one threshold to another — the usable distance you have to land on, accounting for obstacles in your approach path. Now, two speeds related to your landing gear. Landing Gear Extended Speed is the maximum speed at which an aircraft can be safely flown with the landing gear extended. Landing Gear Operating Speed is the maximum speed at which the landing gear can be safely extended or retracted. Notice the difference — one is for flying with the gear down, the other is for the actual act of moving the gear. Landing Minimum Control Speed is the minimum speed with a wing engine inoperative where it is possible to decrease thrust to idle or increase thrust to maximum take-off without encountering dangerous flight characteristics. This is about maintaining control during a critical engine failure on landing. A Large Aeroplane is an aeroplane of more than 5700 kg maximum certificated take-off weight. The category 'Large Aeroplane' does not include the commuter aeroplane category. So this is a regulatory classification based on weight. Lift is that force acting on an aerofoil which is at right angles to the direction of the airflow. That's the fundamental aerodynamic force that keeps you airborne. Load Factor is the ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertia forces, or ground or water reactions. So it's how many times the aircraft's weight is being experienced in a given condition. Mach Number is the ratio of true airspeed to the Local Speed of Sound, or LSS. This is critical at high altitudes and high speeds. Manoeuvre Ceiling is the pressure altitude that provides a 0.3 g margin to both the high speed buffet and the low speed buffet. This is the altitude where you have that safety margin against buffet on both ends of the speed envelope. Maximum Brake Energy Speed is the maximum speed on the ground from which an aeroplane can safely stop within the energy capabilities of the brakes. This is about the brakes' ability to absorb energy without overheating. Maximum Continuous Power and Maximum Continuous Thrust are both the power or thrust identified in the performance data for use during periods of unrestricted duration. So this is the maximum you can use indefinitely without damaging the engines. Maximum Structural Take-off Mass is the maximum permissible total mass of an aeroplane at the start of the take-off run. Maximum Structural Landing Mass is the maximum permissible total mass of an aeroplane on landing, under normal circumstances. These are structural limits you must never exceed. Minimum Control Speed is the minimum speed at which the aeroplane is directionally controllable with the critical engine inoperative and the remaining engines at take-off thrust. This is a key safety speed for engine failure scenarios. Finally, Minimum Unstick Speed is the minimum speed demonstrated for each combination of weight, thrust, and configuration at which a safe take-off has been demonstrated. This is the speed at which you can safely rotate and become airborne. These definitions form the foundation of your performance calculations. Each one has operational significance — they determine your limits, your margins, and your decision-making. Take them in, because we'll build on every one of them as we go deeper into performance.