A and C, your original post suggested (at least to me) that a Cirrus ditching under its parachute in salt water would float, could be pulled from the water, rinsed off and fly again. I think you and I have clearly demonstrated now that that's not the case. Even if the fuselage itself can be reused, lots of components will need to be tested, cleaned, overhauled, replaced or whatever. Not trivial.
As for floating on its fuel tanks after ditching, I do not have the numbers here for a Cirrus but a standard Diamond (no long range tanks) can hold 28 USG of fuel. When empty, that's 106 liters of air providing 106 kg of buoyancy (a little more than that in salt water). The empty weight of our (IFR, so comparatively heavy) DA-40 is 815.3 kilos. So in order for it to float, it needs to pull some serious amount of buoyancy from somewhere. I doubt whether the foam sandwich will provide enough, and I cannot readily think of anything else that's significantly lighter than water in the aircraft that can provide buoyancy. So my gut feel is that as soon as the cockpit fills with water, the aircraft will sink.
Soay, nice pics of that SR22. It clearly shows that a ditched aircraft will sit in the water with a nose-down attitude due to the weight of the engine. In this case, initially some 20 degrees or so, going to about 90 degrees as the cockpit fills up.
Last edited by BackPacker; 30th Oct 2007 at 11:18.