My best guess is Vans has gone to a lot of trouble to get the plane listed as an E-LSA and lists the numbers to conform with the rules for LSA.
They tested the wing to failure, divided the load by 1.5 (standard safety factor0 and compute Vne from that.
Wayne 120241/143WM
This still makes no sense at all to me. We are making an aircraft that "someone" knows how fast it can be safely flown, but it must be kept a secret from us? Absurd!
Now if they simply do not know or care, that is another matter entirely.
This still makes no sense at all to me. We are making an aircraft that "someone" knows how fast it can be safely flown, but it must be kept a secret from us? Absurd!
Now if they simply do not know or care, that is another matter entirely.
....the speed at which it can be safely flown in calm conditions is Vne, and that number is no secret. You can also fly it faster, probably around 20%-25% until you have used up all the 50% `engineers design margin', and it should still hold together. No real secrets there either....
I suspect the decision to make this info "proprietary" has, at it's root, some concern about legal liability. No way to tell for sure, though.
Be careful folks. The normal aviation 50% safety factor is on structural loads, not airspeed. The loads go up very quickly as the airspeed increases, so you would hit limit load at much, much less than 150% of VNE. And, from a flutter perspective, the margins are even less. I don't have a copy of the LSA requirements, but the older FAR 23 requirements on VNE only required that VNE be no faster than 90% of the speed at which flutter would occur. I.e, if you had a perfect airplane, you might get flutter at 111% of VNE. If you had some slack in the hinges, etc, flutter might occur at a slower speed than that.Don, the speed at which it can be safely flown in calm conditions is Vne, and that number is no secret. You can also fly it faster, probably around 20%-25% until you have used up all the 50% `engineers design margin', and it should still hold together. No real secrets there either.
Actually, that extra 50% only means that failure to support the load is pushed out that far. But permanent deformation damage is permitted in that range. So if you're using it up, you're already damaging the airplane, and you can expect permanent wrinkles and looser joints and so on, at a minimum.
Putting my professional aerospace structural analyst's hat on for just a moment, I've gotta say, "DON'T GO THERE!"
Dave
Be careful folks. The normal aviation 50% safety factor is on structural loads, not airspeed. The loads go up very quickly as the airspeed increases, so you would hit limit load at much, much less than 150% of VNE. And, from a flutter perspective, the margins are even less. I don't have a copy of the LSA requirements, but the older FAR 23 requirements on VNE only required that VNE be no faster than 90% of the speed at which flutter would occur. I.e, if you had a perfect airplane, you might get flutter at 111% of VNE. If you had some slack in the hinges, etc, flutter might occur at a slower speed than that.
Agree totally (structural engineer's hat on). That margin over Vne does not belong to the pilot.
MartySantic;5761Retired from the nuclear power industry. Engineering margin BELONGS to the plant engineer and not the operator. To put it in terms of the RV-12 said:I'm not suggesting that the margins be tampered with. As a mechanical engineer (BS, MS, PhD) I'm simply curious about how they were established. I don't think my curiosity means I should build a different airplane.
Jerre
Vans provides Vne and other speeds (thie following is copied from the RV-12 POH which was referenced from a previous post).
How they determined these limits and what desogn feature imposed the various limits is, to my knowledge, not provided. It could be could be reasonably argued that knowledge of what design aspect defines the limit is not required for safe operation and could lead to unwarranted speculation of how much deference the end user gives to the published limit.
-Dave