Multi-engine Piston Aeroplane (MEP) — Page 68, Lesson 69

I want to walk you through the data sheet information for the Multi-engine Piston Aeroplane, or MEP, that we'll be using for flight planning. This is a specific aircraft type, designated MEP1, and it's a monoplane — that means it has a single wing structure — with two reciprocating engines. Those are piston engines, like what you'd find in a car but built for aviation. It has twin counter-rotating constant speed propellers, which means the propellers turn in opposite directions to cancel out torque effects, and they automatically adjust blade angle to maintain a set RPM. It also has a retractable undercarriage, so the landing gear folds up in flight to reduce drag. The aircraft is similar to a Piper Seneca, which is a common light twin. Now, let's look at the key mass and fuel limits you need to know for this aircraft. First, the Maximum Take-off Mass, or MTOM, is 4750 pounds. That's the heaviest the aircraft can be at the start of the take-off roll. Next, the Maximum Zero Fuel Mass, or MZFM, is 4470 pounds. This is the mass of the aircraft including the crew and payload, but with no fuel on board — so it's the structural limit for the airframe without the weight of fuel in the wings. The Maximum Landing Mass, or MLM, is 4513 pounds — that's the heaviest you can be when touching down. For fuel, the maximum fuel load is 123 US gallons. The assumed fuel density, unless you're told otherwise, is 6 pounds per US gallon, which corresponds to a specific gravity of 0.72. So the maximum fuel mass is 123 gallons times 6 pounds per gallon, giving you 738 pounds. There's also a note showing an alternative calculation: 123 times 0.72 times 8.3 equals 735 pounds — that's just a different way using specific gravity and the weight of water, but the 738-pound figure is the one you'll use. Now, regarding power settings: there are four percentages given — 75%, 65%, 55%, and 45%. The 75% setting equates to High Speed Cruise, 65% is Economy Cruise, and 45% is Long Range Cruise. You'll notice that 55% has no cruise description — it's just listed as a power setting without a named cruise mode. The data sheets for this MEP1 are used in a similar manner to those for the SEP1, which is the Single-engine Piston Aeroplane you may have seen before. The following paragraphs in the book explain the use of the data sheets. Also, a very important note for your exam: in the Flight Planning exam, you will be issued with a workbook instead of the CAP 697 manual, and that workbook will contain the necessary pages for that particular paper. Let's move into the climb data. The section is called "MEP 1 — Fuel, Time and Distance to Climb Data." There are separate reference lines for time, distance, and fuel to climb, but only one combined scale — so you read all three values from the same chart area. I'll walk you through the first climb example. You're asked to refer to CAP 697 Figure 3.1. The given conditions are: the airfield is at Mean Sea Level, or MSL, and the Outside Air Temperature, or OAT, is +20°C. You're climbing to Flight Level 120, which is 12,000 feet on the standard pressure setting, and the OAT at that level is -10°C. The question asks: what is the fuel, time, and distance covered in the climb? You'd note those as F, T, and D. Then, with a 35-knot tailwind, what is the ground distance covered in the climb? That's a separate calculation because the wind affects your ground distance even though the air distance from the chart stays the same. The second example gives: airfield at 4000 feet, OAT +0°C, climbing to FL140 with OAT -20°C. Again, you find fuel, time, and distance. The table at the bottom shows FL140, 4000 feet, and the word "Difference" — that's a prompt to subtract the values at 4000 feet from the values at FL140 to get the fuel, time, and distance for the climb segment between those two altitudes. Let me show you the diagrams that illustrate these concepts. First, Figure 3.1 shows the relationship when NAM is greater than NGM — that's Nautical Air Miles versus Nautical Ground Miles — and it explains the effect of a tailwind. Figure 3.2 shows the opposite case, when NAM is less than NGM, and it gives the relationship between NAM, NGM, TAS, Ground Speed, and Wind Component. Figure 3.3 shows how to convert NAM to NGM using a navigation computer, and it notes that if TAS or GS are not known — for example in a climb or descent — the conversion can still be done. So to summarize: you have a specific aircraft with defined mass limits, fuel capacity, and power settings. The climb data charts give you fuel, time, and air distance for a climb between two altitudes and temperatures, and then you apply wind to get ground distance. That's the foundation for the climb phase of your flight planning.