Performance - Introduction — Page 140, Lesson 165

We're starting the Performance section of your Mass and Balance and Performance book, and the very first thing we have is a glossary — the alphabet soup of aviation. I want to walk you through these terms because they're the vocabulary you'll use for the rest of your career, and every single one of them will show up again in the performance chapters. Let's begin with the runway and landing terms. LDA is Landing Distance Available — that's the physical length of runway declared available and suitable for landing. LDR is Landing Distance Required — the distance your aircraft actually needs to land, factoring in approach speed, weight, and conditions. The difference between those two is your safety margin. Then we have RESA, the Runway End Safety Area — that's the area beyond the runway end, designed to stop an aircraft that overruns. And PCN, the Pavement Classification Number — that tells you the load-bearing strength of the pavement, so you know if the runway can support your aircraft's weight. Now the speed and Mach terms. LRC is Long Range Cruise speed — the speed that gives you the best fuel economy over a long distance. MLRC is the Mach Number for Long Range Cruise — same concept, but expressed as a Mach number rather than an indicated airspeed. MRC is Maximum Range Cruise Speed, and MMR is the Mach of Maximum Range. MCRIT is the Critical Mach number — the Mach number at which airflow over the wing first reaches the speed of sound locally, causing drag to rise sharply. MMO is the Maximum Operating Mach number — the absolute limit you must never exceed in normal operations. Let me pause there, because I want to make sure you see the distinction. MRC and MMR are about efficiency — the speed that gives you the most range for your fuel. MMO is a structural and control limit — you cannot go faster than that, period. And MCRIT is the aerodynamic warning that drag is about to increase dramatically. Now the mass terms. MTOM is Maximum Take-off Mass — the heaviest your aircraft can be at the start of the take-off roll. MZFM is Maximum Zero Fuel Mass — the heaviest the aircraft can be with no usable fuel on board, which protects the wing structure from excessive bending loads. MAT stands for Mass-altitude-temperature — that's the combined effect of your weight, the pressure altitude, and the outside air temperature on performance. All three together determine how well your engines and wings will perform on any given day. Let's move to the engine and thrust terms. MCT is Maximum Continuous Thrust — the highest thrust you can maintain indefinitely without damaging the engine. N1 is the speed rotation of the fan — that's the rotational speed of the front fan in a turbofan engine, expressed as a percentage. PMC is Power Management Control — the system that manages engine power automatically. SFC is Specific Fuel Consumption — the amount of fuel burned per unit of thrust per hour, a measure of engine efficiency. Now the fuel and range terms. SAR is Specific Air Range — the distance you can fly per unit of fuel, essentially your fuel efficiency in nautical miles per kilogram of fuel. SR is Specific Range — very similar, the range per unit of fuel. PNR is Point of No Return — the point in your flight where you no longer have enough fuel to return to your departure point, so you must continue to your destination. Let me clarify the difference between SAR and SR, because they're easy to confuse. SAR is specifically about air distance — distance through the air. SR is the broader term for range per unit of fuel. In practice, they're closely related, but the book distinguishes them, and you should too. Now the altimeter settings — these are critical for your instrument flying. QFE is the altimeter subscale setting which causes the altimeter to read zero elevation when on the airfield reference point or runway threshold — so with QFE set, your altimeter reads zero when you're on the ground at that airfield. QNH is the altimeter subscale setting which causes the altimeter to read the elevation of the airfield above mean sea level when placed on the airfield reference point or runway threshold — so with QNH set, your altimeter reads the field's actual elevation above sea level. QNE is the indicated height on the altimeter at the aerodrome datum point with the altimeter subscale set to 1013.2 hPa — that's the standard pressure setting, and it's what you use above the transition altitude. Let me make that crystal clear. QFE gives you height above the airfield — zero on the ground. QNH gives you altitude above mean sea level — the field's elevation when you're on the ground. QNE is the reading you get with the standard 1013.2 hectopascal setting, regardless of the actual pressure. Now the remaining terms. MSL is Mean Sea Level — the reference datum for altitude. OAT is Outside Air Temperature — the actual air temperature outside the aircraft, which affects engine performance and true airspeed. PA is Pressure Altitude — the altitude indicated when the altimeter is set to the standard 1013.2 hPa, which corrects for pressure variations. TAS is True Airspeed — your actual speed through the air, as opposed to indicated airspeed. TAT is Total Air Temperature — the temperature of the air as it's rammed into the aircraft, which includes the heating effect of your speed. N means All engines operating — that's your normal condition. N-1 means One engine inoperative, and N-2 means Two engines inoperative — these are the failure conditions you must plan for. OEI is One Engine Inoperative — the same as N-1, but it's the standard abbreviation you'll see in performance charts. NFP is Net Flight Path — the actual flight path your aircraft will follow, accounting for all the performance margins and safety factors. NM is Nautical Mile — the standard unit of distance in aviation. NOTAM is Notice to Airmen — a formal notice about hazards, changes, or restrictions affecting flight. MEL is Minimum Equipment List — the list of equipment that may be inoperative while still allowing the aircraft to be dispatched. RNP is Required Navigation Performance — the precision standard your navigation system must meet. PFD is Primary Flight Display — the main electronic flight instrument. RTO is Rejected Take-off — the procedure for aborting a take-off after it's begun. RZ is Reference Zero — the reference point from which distances are measured. psi is Pounds per square inch — the unit of pressure. That's the full glossary for this section. These aren't just definitions to memorize — they're the building blocks of every performance calculation you'll do. When we get into the actual performance chapters, you'll see these terms used constantly, and now you'll know exactly what each one means.