Air Conditioning — Page 140, Lesson 164

Right, let's get you started on the Performance section of your ATPL studies. This first page is essentially the glossary for the whole subject, so we're going to build your vocabulary from the ground up. I'll give you the exact professional term, then explain what it actually means in the real world of flying. Let's start with the aircraft systems you'll see referenced constantly. ACARS stands for Aircraft Communications Addressing and Reporting System. Think of it as a digital text-messaging system for the aircraft, automatically sending and receiving data like position reports, weather, and maintenance messages with the ground. ACS is simply the Air Conditioning System, which controls the cabin temperature and pressurisation. FMC is the Flight Management Computer, and the wider FMS is the Flight Management System — the computer suite that handles navigation and flight planning. FCOM is the Flight Crew Operating Manual, the official handbook for the flight deck, and AFM is the Aeroplane Flight Manual, the certification document that defines the aircraft's approved performance and limitations. Now, the regulatory and organisational bodies. ICAO is the International Civil Aviation Organization, the UN body that sets global standards. EASA is the European Aviation Safety Agency, which regulates aviation in Europe. FAA is the Federal Aviation Administration, the American equivalent. JAA was the Joint Aviation Authority, and its standards were called JAR, the Joint Aviation Requirements — these are the historical European rules that EASA largely replaced. In the UK, you have the CAA, the Civil Aviation Authority, which enforces the ANO, the Air Navigation Order, the primary law for aviation. CAP is a Civil Aviation Publication, which is an official document published by the CAA. Let's move on to the documents and masses. AOM is the Airline Operation Manual, which is the specific airline's own procedures. C of A is the Certificate of Airworthiness, the document that proves the aircraft is fit to fly. C of G is the Centre of Gravity, the point where the aircraft balances, and C of P is the Centre of Pressure, the point where the aerodynamic lift force acts. AUW is the All-up Weight, which is simply the total weight of the aircraft at any moment. DOM is the Dry Operating Mass — that's the aircraft's weight including crew, catering, and standard equipment, but excluding fuel and payload. Now for the performance-specific terms, which are the heart of this section. BRP is the Brake Release Point, the exact position on the runway where you release the brakes and begin the takeoff roll. ASD is the Accelerate-stop Distance, the distance required to accelerate to a critical speed and then stop safely. ASDA is the Accelerate-stop Distance Available, which is the runway length actually available for that manoeuvre, and ASDR is the Accelerate-stop Distance Required, which is the distance the aircraft needs. Similarly, EMD is the Emergency Distance, with EMDA being the Emergency Distance Available and EMDR the Emergency Distance Required. These are all about runway length calculations for safety. Let's cover the speeds and atmospheric terms. IAS is Indicated Airspeed, what the airspeed indicator shows. CAS is Calibrated Airspeed, which is IAS corrected for instrument and position errors. EAS is Equivalent Airspeed, which is CAS corrected for compressibility effects at high speed. G/S is Ground Speed, your actual speed over the ground. TAS isn't listed here, but you'll meet it soon. IAT is Indicated Air Temperature, the temperature read directly from the probe. FL is Flight Level, which is altitude based on a standard pressure setting. AGL is Above Ground Level, and AMSL is Above Mean Sea Level — two different ways of measuring height. ISA is the International Standard Atmosphere, the standard model of temperature and pressure used for performance calculations. hPa is Hectopascal, the unit of atmospheric pressure. IFR is Instrument Flight Rules, and ILS is the Instrument Landing System for precision approaches. Finally, the aerodynamic and economic terms. CL is the Lift Coefficient, and CD is the Drag Coefficient — these are dimensionless numbers that describe how much lift and drag a wing generates. CI is the Cost Index, a number that balances time against fuel cost for the FMS. ECON is the Economic speed, which is the speed for minimum direct operating cost. DOC is the Direct Operating Cost, the cost of actually flying the aircraft. FF is Fuel Flow, the hourly fuel consumption. EGT is Exhaust Gas Temperature, a critical engine temperature limit. ETOPS is Extended range with twin aeroplane operations, the rules that allow twin-engine aircraft to fly long distances over oceans. ACN is the Aircraft Classification Number, and LCN is the Load Classification Number — these two work together to tell you whether a pavement can support a particular aircraft's weight. And the units: kg is Kilograms, km is Kilometres, and kt is knots, which is nautical miles per hour. That's the full vocabulary list. Every one of these terms will come back in detail as we work through the performance chapters, so you've just built the foundation. Let's move on to the first real content.