Larry Flesner wrote: >> I would suggest some distance from the main gear contact point (the axle) out ahead of any point of the aircraft. That makes all numbers positive. <<
I'm not sure there's any real reduction in error possibiliy here, and the main problem I see is that you're trying to measure with accuracy to a point that you can't hang a tape measure on. As long as you pick the farthest forward "hard" point that's not going to change (like the front face of the prop hub), you can then mount an aluminum angle or other straightedge to it, rotate it to positioin it logitudinally aligned with what you're measuring to, hang your tape measure end on it, and stretch the tape until you nail the distance. Result, one simple directly measured number gets written down.
Assigning a point out in space in front of the prop hub seems like introducing a lot more errors. How do you measure to a point in space in front of your leading edge? For example, every measurement you make is going to have to come from somewhere else, and then have some number added to it (say 30" in front of the firewall). Now you have to add 30" to every number that you measure from somewhere else, so you end up measuring to SOMEWHERE every time, AND adding 30" to it for every measurement. THAT sounds like LOTs of opportunity for error.
I realize this is all about keeping negative numbers out of the equation, but there is absolutely nothing forward of the prop hub flange that factors into the wieght and balance equation....and even if you want to change prop or spinner, you can very easily measure the distance to the centroid of the prop and you'll have ONE negative number to deal with....even I can do that! And if you're using a spreadsheet anyway, the negative stuff is a non-issue.
This is all very fresh in my mind, as I redid my weight and balance last week, to what I'd like to think was excruciating accuracy. Since I had the wheels off to change tires anyway, I noticed one caliper leaking, so had to replace the pads (might as well do both sides) and repack the bearings. And while I'm down to just the spindles....might as well recheck alignment, which I also did. Good news is that alignment is something like .18 degrees toe out....close enough for KR work, I believe. All of this stuff took about a week of mornings to get done, but I feel a lot better about been through the plane concurrent with the annual condition inspection. And FYI, I've been flying N891JF 1.2" forward of the forward CG "limit", with no ill effects, other than I can "only" do 155 mph true airspeed at 10,500!
I had a long conversation with Jim Faughn about KRs this morning, and he's doing fine, despite all the hurricanes that are apparently out to get him! Same old Jim....easy to talk to, full of good stories. He says we may see him at a Gathering in the next year or two....
Mark Langford [email protected] http://www.n56ml.com Huntsville, AL _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected]
