| Happy New Year Earnest,
Well I think it is interesting! I was confused at first because your “peak” descent rate (the tallest hump in the red plot) is actually your minimum descent rate. I guess it is plotted inverted?
Vx is the slowest (IAS), and is the Maximum ANGLE of climb. It allows one to climb to altitude within the shortest horizontal distance. Vy is slightly faster, and is the Maximum RATE of climb. It allows one to climb to altitude in the shortest time.
To determine Vx (best angle of climb) it seems like you need to plot Vertical Speed divided by Horizontal Speed and find the maximum of that. I don’t think either of your plots is doing this, so I don’t think you can clean Vx from your plots. Vy is the best rate of climb which is time based, so I think you have that (the peak of the blue plot).
The page reference above does have a method to use rate of climb to determine the best angle Vx. Not sure you can get your rate of climb data to look like a nice hump, but check out that page for more details. Seems to be important to plot on a linear scale starting at 0,0 (speed on the abscissa, ROC on the ordinate).
For best glide, according to the FAA ( https://www.faa.gov/news/safety_briefing/2016/media/SE_Topic_16-01.pdf), this is the most distance forward for each increment of altitude lost. In other words this is the speed which results in the best glide ratio (the largest X/Y). I think your descent rate plot is the speed that gets you the longest time in the air which is not the same thing.
Seems to me you need some calculation of altitude loss and horizontal distance traveled to be able to plot it and look for the peak. The FAA does say that, on most airplanes, the best glide is usually somewhere between Vx and Vy. Also noted by the FAA is that the best glide speed will increase with weight, so you might want to find it at gross weight and know that the best glide speed will be slightly lower than that at lower weights.
I miss the old flyrotary. I'm still using an alternative engine, so you would think that the other discussion groups would have a lot of back and forth, presenting ideas and data; but, there was a certain magic in our old group that was inviting and accepting of exploring stuff that most people seem to lack. Most groups seem to be happily focused on which options they have for seat fabric rather than sussing out some new anomaly they discovered or created in their building/flying endeavors.
I have 9.8 hours left in the fly off period of my Corvair powered 601XL. I posted the message below to the Zenith forum. Nobody seemed to care, even though I found it quite interesting. Nobody seems to have the taste for experimentation over there, I guess.
I've been spending a lot of time trying to nail down the Vx, Vy and
best glide numbers for N167EZ. My methodology has been to have my Dynon
D-100 record data while I fly sawtooth patterns, then analyze the data
with a spreadsheet I created. Saturday was a beautiful data for the
task. Heavy, but high, overcast, with perfectly smooth air once I got
over 2500. I've been doing this a while, so I've gotten much better at
holding my airspeed. Here is the plot of what I got on my outing.
Within the data, I pulled out the center segment of a climb, averaged
the speed and the climb rate. Then I plotted all the segments. The
horizontal bars around each point show how well I maintained the
airspeed, indicating the variance from the average.
The best glide appears to be about 43/44. Would Vx be about 46? I
do get over the trees much better at my home airport if I keep it closer
to 50 than 60. Vy is 59? What is one to make of the severe draggy
bucket at around 64 on the climb?
I think the climb points at 46, 54 and 64 will need to be redone. Awwwh! That means I have to go fly again. Poor me. :-)
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