Dr Hsu, During the early days of Velocity they had a run of Deep Stall fatalities. That’s where the wing stalled first which is almost guaranteed to be a one way trip to the ground. To get to the root of the problem Velocity did exactly what your are talking about by putting a weight on a threaded rod that could be run in and out. They were able to recreate the problem and fix it all at the same time. As Larry pointed out these are not cookie cutter airplanes so the numbers we are seeing don’t really corespondent to what someone else’s should be. Unless we are all using the same datum the numbers don’t matter. What matters is the % chord or the distance from the leading edge at the center section. Bottom line all that work that you put into building your airplane only to discover that if it’s not balanced correctly you might not even be able to control it when it leaves the ground.
Victor Taylor > On Jul 12, 2022, at 03:12, Daniel Branstrom via KRnet <krnet@list.krnet.org> > wrote: > > > There was one plane, I believe it was an experimental, that had some > questions about its flight characteristics at aft CG. It was, IIRC, A 4-place > plane. The designer took a garage door opener screw mechanism, with a trolley > attached and hooked a weight of ~125 pounds to it. The motor for the > mechanism powering the screw was battery powered, and the weight could be > moved fore or aft with a simple switch that regulated the movement and > direction of the screw, hence the direction of the weight. Before taking off, > the W&B was done for different positions of the weight, and the position of > the trolley marked accordingly. > > The plane was flown at different CG locations, and the results reported. > > IIRC, that took place at least 15 years ago. Someone else probably can find > the article about it. > > On 7/11/2022 11:24 PM, Dr. Feng Hsu via KRnet wrote: >> Since CG location is such a critical and sensitive element on aircraft >> safety, why there hasn't anyone in the experimental world tried to resolve >> this issue by design?! >> >> Considering the troublesome CG issue whenever we fly with luggage loading >> concerns, I kept thinking why can't someone design an easy "inflight >> adjustable CG" mechanism, which could manually or even automatically >> adjusting the CG balance with a push of an electric switch? >> >> For example, to add on a CG auto balance subsystem based on sensors attached >> to a slidable or moveable weight? This can't be too complicated of a >> flexible CG mechanism to design and add on to small and CG sensitive >> aircraft, especially for the experimental crow, perhaps? I believe it could >> save lives if done correctly...! >> >> Any thoughts on this? >> >> Dr. Hsu >> >> On Mon, Jul 11, 2022, 10:15 PM Flesner via KRnet <krnet@list.krnet.org> >> wrote: >>> On 7/11/2022 8:34 PM, MS wrote: >>>> but if it's a conventional gear KR, filling up the header and lifting the >>>> tail will tell you how tail heavy the plane is. In my experience with two >>>> of them this lifetime, the KR has a wide CG range that, if exceeded, can >>>> be easily compensated for with extra speed if necessary. Both my KR's >>>> have let me get away with murder, but both KR's were built by engineers >>>> who were precise with their work. Assuming a KR has been built with >>>> finesse, my impression is they are very forgiving. >>> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >>> >>> I'm amazed that someone with your experience takes such a cavalier attitude >>> to weight and balance of an aircraft. Tail light or heavy tells you >>> nothing about the CG location but rather the location of the landing gear >>> in relation to the CG. An aircraft with uncontrollable aft CG might have a >>> light tail if the gear is close to the CG location and a very nose heavy >>> aircraft could have a heavy tail if the gear is mounted well forward. The >>> actual CG must be determined with scales, measurements, and math. An >>> engineer / designer will try to place the main gear on a conventional gear >>> aircraft as close to the CG as possible for the best possible ground >>> handling. In the case of the C140 they went a bit too far and made the >>> airplane extremely tail light and pilots were putting the airplane on the >>> nose with excessive braking. The fix was to modify the gear and place the >>> wheels about 4 inches further forward. Lifting the tail before and after >>> the mod would not give you the location of the CG but only the relative >>> location of the gear to the CG. The CG location never changed only the >>> tail weight. Was the CG location correct? Only scales, measurements, and >>> math can determine that. >>> >>> As far as the KR letting you get away with murder, I'm thinking the design >>> more likely kept you from committing suicide. CG should not be taken >>> lightly............ >>> >>> Larry Flesner >>> >>> >>> >>> -- >>> KRnet mailing list >>> KRnet@list.krnet.org >>> https://list.krnet.org/mailman/listinfo/krnet >> > -- > KRnet mailing list > KRnet@list.krnet.org > https://list.krnet.org/mailman/listinfo/krnet
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