Definitions and Calculations — Page 63, Lesson 83

Let’s start with the single-engine piston/propeller aircraft, which CAP 696 calls the SEP1. The documentation procedure for the SEP1 is basically the same as the calculations we’ve already covered in these notes — the load manifest and the centre of gravity envelope are the two key documents, and they’re specific to that particular type of aircraft. So you don’t invent a generic manifest; each aircraft type has its own. There are worked examples in the question section starting at page 77 of this book. Now the light twin piston/propeller aircraft, the MEP1. Again, the procedure in CAP 696 is similar to what we’ve done, and again the load manifest and CG envelope are type-specific. CAP 696, MEP1 page 2 has a sample load-sheet calculation, and page 1 has the specific mass and balance requirements for that aircraft. You should study those pages, then attempt the self-assessment questions. Examples for the MEP1 start at page 81 here. Then we come to the medium range twin jet, the MRJT1. This one is more complex — it has a more involved loading and trim sheet, which we’ll deal with shortly. CAP 696, MRJT1 pages 2 through 5 contain the type-specific information, and you should study those in detail. I’ll give you notes on particular items. Now here’s the key conceptual point, and it’s about body stations. Look at MRJT1 Figures 4.1 and 4.2. In principle, you could locate every component and part of the airframe by physically measuring its distance from the CG datum. But that’s difficult and impractical on anything other than a very small aircraft. So instead, aircraft are divided about their three axes by a system — and that system is what we’re about to unpack.