A6M3 safe loading factor

[drgondog]

My mistake, Bill. Steve said the load limit for the A6M5 Model 52 was "considerably higher than for the A6M3, due to shorter span." He didn't specifically state the limit normal g limit and said he recalled 16 g untimate at filuire, but would have to check the documents to be sure. He hadn't seen the document since about 1977 when the original restoration was completed. The A6M3, according to Shinpachi, was stressed to 7 g with a 1.8 safety factor, making it 12.6 g failure limit.

I wasn't questioning you, or indirectly Steve. My comment to his "shorter span/much stronger airframe" is that it should be true IF the spar and all other structural details of the wing are the same and Gross Weight same or less - and the wing spar is the design failure point. If the First Yield Tensile stress failure is somewhere in the empennage due to a rolling climb, then the clipped wing version would not help.

Since the A6M5 srtucture is essentially the same with shorter span, I infer 8.89 g and 16 g, using the same 1.8 safety factor. Either way, it is stronger than 7 g, which makes semse if nothing changes except to shorten the span.

See above as the Gross Weight is the primary factor to resolve the Lift force calculated as well as the Center of Lift of the distributed area of an elliptical 'like' pressure distribution is how they analyzed it..

In other words the shortened wing span of a clipped wing A6M moves the Center of lift inboard theoretically and for a spar that was designed for same distributed beam load with centroid of the load slightly further outboard (original A6M), the spar should have slightly less stress at the more inboard location of the Center of Lift. Gross weight is bigger factor and the calculated G limit may NOT be inferred as a ratio of the spans.

They do that for some kitplanes, too. I have a friend who built a Harmon Rocket (which I occasionally get to fly) and they removed one rib bay from then RV-4 wing to shorten the span and stay in the aerobatic category while adding a Lycoming AIO-540 instead of an O-360 up front. I have not calculated it, but they call it a +6 / -3 aircraft. Could be stronger actually.

If the spar and surrounding structure plan essentially remains the same but shorter span, one would think the Center of Lift moves inboard, lessening the Bending load distribution - If the Lift forces increase because of Gross Weight increases - then not quite so black and white.

 

[Timppa]

For 2024 and other similar (Clad 24S-T3, etc) the Tensile strength is 64KSI, and for purposes of design is that stress 'point' at which the permanent set is .002 strain from original length.

Yield strength for 2014-T3 is 43 ksi, tensile 63-64 ksi .

Zeros had the Sumitomo ESD, comparable to 7000- series.