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Legal max speed verses max structural speed.

Crafting N112DR

Well Known Member
First let me say I’m not endorsing anyone exceed the manufacturers Vne speed. I’m just putting out this question as a thought experiment, after all we are building experimental aircraft. Why not have experimental thoughts to.

What if the RV-12iS was designed for a higher max speed then published (say 150 Knots) then it is current certified max speed of 120 knots. So with that in mind is this max speed being restricted by the FAA LSA rule or is it a hard design max speed?
The reason I ask this is due to the FAA possibility rumors of increasing there max LSA speed to 150 knots and max weight to 3200.
Anyone who built a EAB RV12 flown over 120 knots?

okay now that’s enough experimental thought. Everyone back to reality.
 
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Does the FAA set the never exceed speed or maximum continuous cruise speed? Do not count on those FAA rumors coming true.
 
Never exceed speed

The RV-12 has a 136knot TAS never exceed speed if I remember correctly.
 
Right.. 120kt CAS is the maximum permitted cruising speed in level flight at sea level. Vne is set by Vans (by the engineers / design limits). You could definitely make some speed mods and get your cruise speed higher.. I think maybe what the real question is "what did vans do to slow the plane down [for meeting the LSA requirements] that i can [easily] undo?"

Does the FAA set the never exceed speed or maximum continuous cruise speed? Do not count on those FAA rumors coming true.
 
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All the loads are determined, in part, by the speeds that the airplane is designed for. So while the FAA might establish something like the LSA rules, the designer, while keeping to them, designs the plane for the loads that those limitations impose.

Once the plane's design is frozen, they are very real things and really not a matter of the governmet's whim.

If you want a faster airplane, get a faster airplane.

Dave
 
Right.. 120kt CAS is the maximum permitted cruising speed in level flight at sea level. Vne is set by Vans. You could definitely make some speed mods and get your cruise speed higher.. I think maybe what the real question is "what did vans do to slow the plane down that i can [easily] undo?"

Do the rest of the RV models have thicker skins? If so, would that be a significant factor for + speeds and weights?
 
If you want a faster airplane, get a faster airplane.

Dave

That?s funny... Last week we were flying the RV-12 back from a small airport 15 miles south. C172 departed ahead of us and announced right turnout and destination same as us. We scooted right behind him and turned inside his right-crosswind and set the GPS for home. End of story is we were on the ground and taxiing to the hanger when he was just showing up on downwind. We heard him say he was on downwind and then a pause? ?I need to get a faster airplane?. :D
 
Speed

When it comes to max speeds, trust the engineers. TLAR engineering isn?t a good plan when dealing with potential flutter issues...
 
I've had similar thoughts as the original poster. Not so much as a "How can I work around the LSA requirements" but rather, if the rules changed and I was say in the middle of building a 12iS would I be able to upgrade with say a different power plant and wings or would it require an entirely new build all together..

I love the 12 for the simplicity and its abilities but if I could have 150kts instead of 120kts in the same platform I'd happily accept and make accommodations
 
Flutter would be the issue here. Not static loads due to skin thickness. In fact in level flight the loads would not really change, you are still flying 1g. If the vans folks cleared the airplane to 120 plus an allowable margin, then that's the envelope. Could it do more without coming apart? Good question. I doubt very much that they looked at it nor was there any reason to.

In the immortal words of Clint Eastwood: "do you feel lucky punk?". :p
 
Airplanes are designed to meet many requirements that are influenced by speed.

One of them is flutter, but there are numerous others.

One important one is design considerations for gust loads.
Likely all pilots know that in turbulence, slowing down reduces how rough the ride is. Inversely, the faster you go, the worse the ride is.

Airplanes are designed to tolerate a specific gust load at max structural cruise speed. If you make modifications that change the max. speed capability, but nothing is done to the structure, you would be at risk of structural damage or failure because of gust loading while flying at the higher speed.
 
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