PaulRomano
Member
Steve--you are more than welcome to spend some time with me in Colorado. I can go over in detail the various ways we look at things, and how you can do some basic calculations for your aircraft. I have one set of the waterjet cut LE fixtures, Vince has the other set in his facility in Indiana. Fly in to KLMO after Phase I, or I can pick you up at DIA. I can talk about most things, only a few will be off limits. None of what I do is special.I had not really intended to extend the RV-4 envelope in terms of Vne (or tickle the dragon) beyond what Vans had specified. My intention was to test/demonstrate my tapered wing as capable of replacing the original wing and meeting the original Vans parameters in terms of Vne (gross weight and hence range parameters increased). On paper, or by the numbers, my wing is slightly more flutter resistant than the original wing I replaced. Vans publishes a Vne of 210 MPH and the standard of testing in regards to Vne is (as I understand it, again I am without credentials) 110%. That is how the testing parameters of 231 MPH IAS was arrived at. This was theoretically doing nothing with the wing that Vans had not already demonstrated on the original wing, assuming they too tested to 110% the published Vne. But - at what altitude?
Every "store bought" non pressurized piston powered plane out of Wichita or Vero Beach (or any manufacturer selling certified planes in the US) has a red line at the clockwise end of the ASI. This is an IAS limit, that's why its painted on the ASI. Then Vans publishes a letter or bulletin (as stated above I think it was in regards to turbo charging RV's) about the risks of high True Airspeeds that can be achieved at altitude, especially if you can keep your ponies strong up there. So now there is some question (and corresponding discussion here on VAF at the time) of just what the airspeed limits are of the RV series. According to the "consensus opinion" and seemingly best answers I could find, the Vne on certificated airplanes is an IAS limit (hence being marked on the ASI) and valid up to the altitudes at which the aircraft is intended to be operated. Is this up to its technical service ceiling or only up to its intended/predicted use. ??? Dunno So Van's article about the hazards of high TAS causes me to wonder what is safe to do with my RV-4. I called them (a decade or so ago, near the time they published the "notice/bulletin") and asked them to what altitude the published Vne applies. They were "strongly resistant" to providing an answer to the question. So from that point on I flew my original wing with a self imposed TAS limit of 210 MPH.
Upon completion of the new wing I'm doing Phase 1 flight testing, in an assigned test area, with parachute and test pilot. The perfect opportunity to determine/demonstrate an altitude to which the 210 MPH Vne applies. So I/we somewhat arbitrarily chose 10,000' This is an altitude to which the RV surely was intended to operate, well below the requirement for oxygen, and only moderately above the terrain in a large portion of the northwest. Vans declined to tell me an altitude to which it applied, so I decided 10,000 was a reasonable number to "demonstrate" for myself and then utilize as a limit. Above 10,000 I would continue to use a conversion table so as to not exceed the TAS demonstrated at 10,000' I did not consider this to be "high adventure", "irresponsible" or "tickling the dragon".
Above it was stated that Vans has since clarified that the Vne is a TAS limit. This, if accurate, strikes me as a very unexpected answer to the question I posed to them of "to what altitude". I'd never have expected them to reply "Sea Level". This makes the standard practice (and likely FAA requirement for certified aircraft) of placing a red line on the ASI pretty much irrelevant or nonsensical since there is almost nowhere you can fly at sea level without getting your airplane really dirty. I suspect Vans has stated that the Vne is actually a TAS limit out of an "abundance of caution" and did not intend it as such "back in the beginning".
So am I "tickling the dragon"? (NOT a rhetorical question) How many RV's have descended through 10,000' or even 12,000' or higher during the first 4 decades (prior to the announcement that the Vne was a TAS limit) with the pilot dutifully controlling pitch and power to keep the needle just below that red mark? If Van's truly believes and intends that the published Vne is a TAS limit then, yes, doing at 10,000' what is approved at Sea Level is pushing boundaries, by a lot - but has probably been demonstrated by hapless pilots for 40+ years.
Vince, your comments on pushing/expanding the limits are appreciated and well received. I have to now wonder if I am doing so or not. Comments invited!! Perhaps there is a "Van's guy" visiting here that can elaborate on this from an "insider opinion". If you're out there but not willing to comment publicly I welcome your PM input.
Follow Steve and Bob's guidance, they are the best.
Just beware, my niece calls me Uncle Gruncle.