cludwig
Active Member
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<div style=": white; border-top-style: none; border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; font-family: 'Times New Roman'; font-size: medium; "><div style="color: black; font-family: arial, helvetica, sans-serif; font-size: 12pt; ">Why are Pitts S1 aircraft quoted as +6/-3G? <div style="color: black; font-family: arial, helvetica, sans-serif; font-size: 12pt; ">
<div style="color: black; font-family: arial, helvetica, sans-serif; font-size: 12pt; ">The wing structure of the Pitts aircraft looks fairly symmetrical to me. Is there a reason that the wings are twice as strong upright as inverted, or did Curtis just say +6/-3G because that was the FAA legal minimum and thus the easiest to prove for certification? The S2C is certified as +6/-5G with a nearly identical planform and load paths (though with thicker material to carry the higher gross weight and bigger wings). The Model 12 is quoted as +6/-4.5G (+9/-7.5G ultimate). Given that the Kimballs quote +6/-4.5G along with ultimate strength, I am guessing that they have engineering analysis to support their numbers. <div style="color: black; font-family: arial, helvetica, sans-serif; font-size: 12pt; ">
When ACA designed their metal wings, they first conducted a pretty cool study. They instrumented one of their aircraft and then had various pilots fly outside aerobatics. Well, those that a Decathlon can accomplish with the aim of ensuring their aircraft could fly intermediate level aerobatics. Not that it is easy to win against an Extra in competition, but that the aircraft could be an effective training platform. What they learned is that +6G is perfectly sufficient for that mission, but that -3G was definitely insufficient for safe outside aerobatics. So as not to start anargument, this is not to say that exceptional pilots cannot constrain themselves to -3G, but that this is not sufficient for the average pilot on a bad day. ACA published this info in an SAE report which I managed to read a copy of. This learning prompted ACA to design the new Super Decathlon to +6/-5G to be better suited to inverted aerobatics instruction and competition.
Armed with that knowledge, and the knowledge that Pitts S1 aircraft do quite well all the way up through Advanced competition without the wings coming off, then the wings are surely capable of carrying much more stress than -3G. Don't get me wrong, I do not have the G tolerance to comfortably pull over 6G or push more than -3G. It is not something I would intentionally do. It just seems very strange that Curtis would have quoted +6/-3G when the design was clearly capably of more G, at least inverted.
Does anyone know what the Pitts S1S wings were actually designed for? I suspect that the various wings (Wolf, Raven, Steen, S1S, S1C, etc) all are slightly different but are at least similar in the regard of inverted strength vs upright strength. What is the limiting factor on inverted strength as compared to upright strength?
I'd like to invite plane designers with intimate Pitts knowledge to chime in including Kevin Kimball and Steve Wolf if you have some historical knowledge about the S1 or if you wish to elaborate on your own designs.
Thanks to all,Chris.
Edited by: cludwig
<div style="color: black; font-family: arial, helvetica, sans-serif; font-size: 12pt; ">The wing structure of the Pitts aircraft looks fairly symmetrical to me. Is there a reason that the wings are twice as strong upright as inverted, or did Curtis just say +6/-3G because that was the FAA legal minimum and thus the easiest to prove for certification? The S2C is certified as +6/-5G with a nearly identical planform and load paths (though with thicker material to carry the higher gross weight and bigger wings). The Model 12 is quoted as +6/-4.5G (+9/-7.5G ultimate). Given that the Kimballs quote +6/-4.5G along with ultimate strength, I am guessing that they have engineering analysis to support their numbers. <div style="color: black; font-family: arial, helvetica, sans-serif; font-size: 12pt; ">
When ACA designed their metal wings, they first conducted a pretty cool study. They instrumented one of their aircraft and then had various pilots fly outside aerobatics. Well, those that a Decathlon can accomplish with the aim of ensuring their aircraft could fly intermediate level aerobatics. Not that it is easy to win against an Extra in competition, but that the aircraft could be an effective training platform. What they learned is that +6G is perfectly sufficient for that mission, but that -3G was definitely insufficient for safe outside aerobatics. So as not to start anargument, this is not to say that exceptional pilots cannot constrain themselves to -3G, but that this is not sufficient for the average pilot on a bad day. ACA published this info in an SAE report which I managed to read a copy of. This learning prompted ACA to design the new Super Decathlon to +6/-5G to be better suited to inverted aerobatics instruction and competition.
Armed with that knowledge, and the knowledge that Pitts S1 aircraft do quite well all the way up through Advanced competition without the wings coming off, then the wings are surely capable of carrying much more stress than -3G. Don't get me wrong, I do not have the G tolerance to comfortably pull over 6G or push more than -3G. It is not something I would intentionally do. It just seems very strange that Curtis would have quoted +6/-3G when the design was clearly capably of more G, at least inverted.
Does anyone know what the Pitts S1S wings were actually designed for? I suspect that the various wings (Wolf, Raven, Steen, S1S, S1C, etc) all are slightly different but are at least similar in the regard of inverted strength vs upright strength. What is the limiting factor on inverted strength as compared to upright strength?
I'd like to invite plane designers with intimate Pitts knowledge to chime in including Kevin Kimball and Steve Wolf if you have some historical knowledge about the S1 or if you wish to elaborate on your own designs.
Thanks to all,Chris.
Edited by: cludwig
