Hank Posted September 4 Report Posted September 4 3 hours ago, Niko182 said: VNE on the RV10 is 200 KTAS. Not like the Mooneys that have a KIAS VNE speed. Wow! That would be tough to keep up with, if it's not clearly visible on the panel.
Paul Thomas Posted September 4 Report Posted September 4 1 hour ago, Hank said: Wow! That would be tough to keep up with, if it's not clearly visible on the panel. For all RV, Vne is based on true airspeed (TAS) based. It's a lot easier to display now that EFIS are so popular. I suspect that for most airframes, Vne was based on a TAS but backed down to an indicated speed to make it easier for pilots. Van's had to write articles in the RVator, the newsletters that used to be source of information for builder/pilots to let people know Vne is a TAS limitation. Even once online forums became available, like Van's Air Force, it still shocked many 15-20 years ago that Vne was based on TAS. I suspect a great number of pilot did not understand that limitation and just used the Vne on the airspeed indicator (that you could purchase through Van).
AndreiC Posted September 5 Report Posted September 5 This is *very* confusing, why Vne would be given in TAS. Perhaps someone with serious aeronautical knowledge can explain? I thought the amount of lift (for example) on the wings would be the same at the same IAS, not same TAS. Wouldn’t then stress on the airframe also be a function of IAS?
Vance Harral Posted September 5 Report Posted September 5 1 hour ago, AndreiC said: why Vne would be given in TAS Because one of the concerns with Vne is flutter, and the onset of flutter is a function of both indicated and true airspeed, not just indicated. A decent article is available at https://www.kitplanes.com/wind-tunnel-36/ 2
Niko182 Posted September 5 Report Posted September 5 I guess that would mean the VNE, true airspeed wise for an acclaim should be around 300 KTAS and a 252 should be around 310 KTAS at 25000ft and 28000ft.
Crawfish Posted September 5 Report Posted September 5 This is why Jets have both a VMO (Velocity max operating) typically some sort of structure limitation. And MMO (Max mach operating) typically not a stress limitation but aerodynamic whether it be to keep the plane subsonic, or flutter or some limitation of all of the above. not sure why we don’t post both on small GA planes but I’d venture to guess that indicates those restrictions don’t come into play until above VNE speed at max operating altitude?
Hank Posted September 5 Report Posted September 5 2 hours ago, Crawfish said: not sure why we don’t post both on small GA planes but I’d venture to guess that indicates those restrictions don’t come into play until above VNE speed at max operating altitude? I would certainly expect all manufacturers to apply a safety factor to the Vne listed in the book and marked on the panel! The thought that exceeding Vne by 1 or 2 knots would break my plane is ridiculous. No, I've never reached Vne, but have gone higher into the yellow than I really wanted to a couple of times . . . On the other hand, Vne should be a number that I can see, not one that I have to calculate based on altitude and altimeter setting! Same goes for all limiting airspeeds--Vs0, Vs1, Vg, Vfe, etc.
1980Mooney Posted September 6 Report Posted September 6 (edited) On 9/4/2025 at 9:13 PM, AndreiC said: This is *very* confusing, why Vne would be given in TAS. Perhaps someone with serious aeronautical knowledge can explain? I thought the amount of lift (for example) on the wings would be the same at the same IAS, not same TAS. Wouldn’t then stress on the airframe also be a function of IAS? On 9/4/2025 at 10:49 PM, Vance Harral said: Because one of the concerns with Vne is flutter, and the onset of flutter is a function of both indicated and true airspeed, not just indicated. A decent article is available at https://www.kitplanes.com/wind-tunnel-36/ The main point of the article is "The variation of flutter speed with true airspeed is more complex.". Forces from air molecules hitting our planes are well understood per the Ideal Gas Law - as altitude increases, pressure decreases, and air molecules decrease proportionately. And the forces from those air molecules hitting our planes decrease proportionally. That is why KIAS makes sense. But flutter is a function of the dynamic damping and harmonics of both the plane structure and the air. At higher altitude the dampening of the air is less and has a less predictable effect because of the harmonics of the air interacting with the structure. So determining the critical flutter speed is not easily predicable without actual flight testing with all these dynamic forces in action. On 9/4/2025 at 11:57 PM, Niko182 said: I guess that would mean the VNE, true airspeed wise for an acclaim should be around 300 KTAS and a 252 should be around 310 KTAS at 25000ft and 28000ft. Yes - exactly! It means that the Vans RV-10 has a much, much weaker wing and tail structure than the proven Mooney. Remember that Vans only started saying this when they woke up to the fact as more and more reports of RV break-ups. With N174BK everyone initially tried to dismiss it as a bird strike that caused it to break-up. NTSB found no evidence of a strike. The Mooney has stronger "chops" that are demonstrated every day. When leaving the teen's in my Missile modified J, I routinely hit over 200 KTAS. If you are interested in safety and are flying your family, then buy a Mooney. If not, then buy a homebuilt or experimental. Let's face it, they are generally lighter and may have better performance because something is left out (structure or safety margin) vs a certified. Aviation is a compromise. You can't get something for nothing. Edited September 7 by 1980Mooney 2 3
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