turboplanner Posted May 26 Share Posted May 26 56 minutes ago, old man emu said: You can say that Piper and Cessna added a fairly big fudge factor in establishing the CofG envelope. Maybe they put Human Factors above aeronautical demands in their design specification. It's probably true that you would bend an aircraft on the ramp by overloading before you felt the effects out on the runway, IF the aircraft was a certified type, or a commonly built experimental. However, it's the one-off homebuilt that could give a nasty bite it loading was not correct. What sort of crazy numbers did you use, and where did you place the weights? Here's a thought: See how the manufacturer has given the Moments at several station locations for various loading options. Looking at the cargo carrying options, the Moment aft of the crew seats is given at a single station. In physics calculations, of which W&B's are a type, it is assumed that the weight of an object acts through its centre of mass. That's OK for a regularly-shaped object, but what if you were carrying something highly irregular in shape with very scattered localised weights? I think that the answer to that question lies in having faith in the designer's fudge factors. As long as you remain within the weight limitations for a load area, and the total W&B values put you in the envelope, she's sweet to go! Two things: 1. C172 and PA28 are the "utility" type aircraft I mentioned which are designed for training and work around the flying club, so we would not expect any surprises with them. Cross Country aircraft are the ones where designers might slim down the undercarriage and add more fuel capacity, or extend the caib to take six people and have fore and aft cargo compartments. 2. Moments are calculated from the Datum CG to the CG of the Mass.If you have an irrgeular shape object you still have to find its CG and you can do that reasonable accurately by breaking it up into a series of cubes and triangles, arcs etc. It's when you just guess that it can bite you. Link to comment Share on other sites More sharing options...
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