I think the answer to Dr Hsu's question is that a system of moveable weight (whether that's a sliding weight as suggested, or perhaps a liquid ballast of some sort) will come at the expense of useful load, and useful load is at a premium in small recreational aircraft like the KR. Larger aircraft have facilities to move the fuel around in flight to help maintain optimum balance. Such a system could be implemented on a KR too, but at the expense of complexity and useful load. An aircraft with such a system inevitably will be heavier and therefore have less useful load.
The alternative is simply to do the sums as part of flight planning. It's part of every pilot's training, weighs nothing and costs nothing (apart from self-discipline). TK On Tue, 12 Jul 2022 at 16:24, Dr. Feng Hsu via KRnet <krnet@list.krnet.org> 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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