Single-engine Piston Aeroplane (SEP) — Page 45, Lesson 61

I want to walk you through the Single-engine Piston Aeroplane, or SEP, section. This is a more complex aircraft than the basic Warrior you might have seen before. Let's start with the introduction. The SEP is a monoplane — that means it has a single wing — with a reciprocating engine, which is the technical term for a piston engine. What makes it more advanced is that it has a constant speed propeller. With a constant speed propeller, the propeller rpm — revolutions per minute — is controlled by you, the pilot, using an rpm lever, which is also called a pitch lever. So you can set the propeller speed independently of the engine power. Now, the fuel/air mixture can be set to either "rich" — meaning more fuel — or "lean" — meaning less fuel. The total amount of fuel/air mixture going into the engine is adjusted by varying the manifold pressure. Manifold pressure is simply the pressure of the fuel/air mixture in the intake manifold after the throttle. The higher the manifold pressure, the more mixture is being burnt, and therefore the more power the engine produces. The SEP manifold pressure is measured in inches of mercury, written as "inHg". For example, you might see "25.0 inHg". As the aircraft climbs, the air gets thinner, so you have to manually advance the throttle lever — push it forward — to maintain a desired manifold pressure. Sometimes an engine device can add more fuel/air mixture automatically without you moving the throttle lever, but eventually, during the climb, you'll reach an altitude where manifold pressure can no longer be maintained. At that point, the throttle lever will be at "maximum forward" position, and manifold pressure will start to reduce. This altitude is called "full throttle height", and the power is said to be at "full throttle". The SEP also has a retractable undercarriage — the landing gear can be pulled up into the fuselage to reduce drag. The tables we use assume the undercarriage is in the appropriate position for each stage of flight: "down or extended" for landing and take-off, and "up or retracted" for climb, cruise, and descent. There is no requirement to consider abnormal cases in these tables. Let me give you the key details for this aircraft. The Maximum Take-off Mass, or MTOM, is 3650 pounds. The Maximum Landing Mass, or MLM, is also 3650 pounds. The maximum fuel load is 74 US gallons, and the fuel density is 6 pounds per US gallon, unless you are advised otherwise. Now, for the actual graphs and tables, you would normally refer to CAP 697. However, in the EASA Flight Planning exam, you will be issued with a workbook instead of the CAP 697, which contains the necessary pages for that particular paper. Each graph and table type within CAP 697 has an example explaining how to use it, so the method is not repeated in these notes. Let's look at the first specific data set: SEP - Time, Fuel and Distance to Climb Data, which is CAP 697 Figure 2.1. This graph gives you the time, fuel, and distance — in Nautical Air Miles, or NAM — to climb to any height, given as pressure altitude and outside air temperature, from Mean Sea Level, or MSL. If your departure airport is at sea level, you can read the climb data from the graph in one pass. But if the airport is not at sea level, you have to extract the data for the top of climb — the TOC, or initial cruising level — then extract the data for the airport, and subtract the airport data from your cruising level data to get the correct figures for the climb segment.