Performance - Introduction — Page 136, Lesson 159

We're starting the Performance section of your ATPL studies, and this opening is a glossary of the exact terms you'll be using for the rest of your career. I want to walk you through them in order, because each one is a building block. Let's begin with the Missed Approach. This is when an aircraft is caused to abort a landing after it has already started its landing approach. The aircraft then has to follow a set missed approach procedure to leave the airspace surrounding the terminal. So it's not just "going around" — it's a defined procedure to exit the terminal area safely. Next is Net Height. This is the true height attained at any point in the take-off flight path, but it's calculated using net climb performance. Net height is what you use to determine the net flight path that must clear all obstacles by the statutory minimum, to comply with the Operating Regulations. So it's the height you can guarantee you'll have, not the best-case height. That brings us to Net Performance. This is the gross performance diminished to allow for various contingencies that cannot be accounted for operationally — for example, variations in piloting technique, or temporary below-average performance. The key point here is that it is improbable that the net performance will not be achieved in operation, provided the aeroplane is flown in accordance with the recommended techniques. So net performance is your safety margin built into the numbers. Now, Outside Air Temperature — this is simply the free air static, or ambient, temperature. That's the temperature of the air around you, not heated by the aircraft. Pitch Setting is the propeller blade setting determined by the blade angle, measured in a manner and at a radius declared by the manufacturer and specified in the appropriate Engine Manual. So it's a specific, manufacturer-defined measurement of the blade angle. And Pitch itself is the motion of the aeroplane about its lateral axis. That's the nose-up or nose-down rotation. Pitot Tube is a small tube whose open end collects Total Pressure. That's the pressure you need for your airspeed indication. Pressure Altitude is the altitude of an aircraft above the pressure level of 1013.25 hPa. You achieve this by setting the altimeter subscale to 1013 hPa and reading the altitude indicated. So it's your altitude above the standard pressure datum. Reference Landing Speed is the speed of the aeroplane, in a specified landing configuration, at the point where it descends through the landing screen height, in the determination of the landing distance for manual landings. So it's a defined speed for a defined configuration at a defined point. Rejected Take-off, or RTO, is a situation or event in which it is decided, for safety reasons, to abandon the take-off of an aircraft. Roll is the motion of the aeroplane about its longitudinal axis — that's the wing-tip up or down rotation. Rotation Speed is the speed at which, during the take-off, rotation is initiated with the intention of becoming airborne. That's when you pull back on the controls to lift the nose. Runway is a defined rectangular area on a land aerodrome, prepared for the landing and take-off run of aircraft along its length. Runway Strip is an area of specified dimensions enclosing a runway, intended to reduce the risk of damage to an aircraft running off the runway, and to protect aircraft flying over it when taking off or landing. Runway Threshold is the beginning of that portion of the runway usable for landing. Now, Screen is an imaginary barrier, located at the end of the Take-off Distance Available, or TODA, or the beginning of the Landing Distance Available, or LDA. The screen is of no operational significance, but the test pilots use the height of the screen when assessing the performance of the aeroplane. So it's a reference point for certification, not for your flying. Finally, Service Ceiling is the pressure altitude at which the rate of climb is reduced to a specified minimum value — approximately 300 ft/min. Now, I want to connect a few of these. The Screen and the Reference Landing Speed work together — the screen height is where you measure that speed. And Net Height and Net Performance work together — the net height is what you get when you apply net performance to the climb. These are the terms you'll see again and again in the performance calculations ahead.