Hi Feng - Take a look at this:
https://www.youtube.com/watch?v=KCCy-ojQMcE&ab_channel=AbsolutelyDefinite [https://i.ytimg.com/vi/KCCy-ojQMcE/maxresdefault.jpg]<https://www.youtube.com/watch?v=KCCy-ojQMcE&ab_channel=AbsolutelyDefinite> Sudden shift in heavy cargo apparent cause of deadly 747 crash (June 3, 2013) - YouTube<https://www.youtube.com/watch?v=KCCy-ojQMcE&ab_channel=AbsolutelyDefinite> New details on deadly 747 crash. Report: sudden shift in heavy cargo apparent cause. Monday, June 3, 2013. www.youtube.com As a former B744F driver this sort of weight-shift scenario is petrifying. To boot, a colleague of mine died in the UK due to cargo weight shift in a turboprop freighter. The point being that shifting dead weight around in an aeroplane is indeed a 'shifty' practice! Could one design an 'easy in-flight adjustable' electromechanical system to be failsafe? How would the risk analysis pan out? Likelihood of failure - probable. Consequence of failure - fatal/catastrophic? As I recall, design gross on a KR2 is about 900lb - the KR2S a bit more (980lb?). How many aircraft fly to the design limits? How does a ding-a-ling like me establish a useful neutral point then workable static margin to maintain positive static stability throughout the flight envelope? The defined limits of such a system would vary between each (homebuilt) aeroplane. Adding weight to provide balance reduces useful load. Better to shuffle fuel between tanks to maintain efficient balance. Airliners do this - but they have computers and sensors to enable it. Maybe it would be easier to swing the wings back and forth? I doubt it. I like your thinking - but the complexity of the issue is not to be underestimated. I'm sure a clever fellow such as yourself could come up with a unique working model - such is the beauty of experimental aviation. It would probably take the likes of me the remainder of my useful life in research and tinkering ... I think I'll just take the extra 5 minutes before each flight to do a quick weight & balance. If I fly the aircraft regularly then I'll probably be able to come up with a template which would reduce the W&B exercise to 1 or 2 minutes. Cheers Kiwi ________________________________ From: KRnet <krnet-boun...@list.krnet.org> on behalf of Dr. Feng Hsu via KRnet <krnet@list.krnet.org> Sent: Tuesday, 12 July 2022 18:24 To: KRnet <krnet@list.krnet.org> Cc: Dr. Feng Hsu <fenghs...@gmail.com> Subject: Re: KRnet> WB got some real numbers 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<mailto: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<mailto:KRnet@list.krnet.org> https://list.krnet.org/mailman/listinfo/krnet
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