Pattern Help

[Earl Haury]

Several have mentioned the lack of help in the form of coaches, competent observers, etc. which could help them improve their flying skills. This is probably more common than not, and makes it difficult for each of us to improve (even the FAI guys). I've found a couple of ways around this that some might find useful. 

The first is score analysis. Simply input raw scores (each maneuver / each judge) into a spreadsheet. Even a 4 round contest with 2 judges / flight will yield 8 scores / maneuver. Average each maneuver's score set and calculate the standard deviation. This provides a feel for how well any given maneuver was flown and a feel for consistency - the lower the std dev the better. This info lets one see what needs improvement the most and, over several contests, note progress.

Of course score analysis doesn't indicate just what the problem is. There have been many good suggestions regarding seeking that input from fellow competitors, interested observers, etc. Another method exists that can provide valuable info.
That method is a datalogger. I've recently been using the latest USB Datalogger to look at in flight parameters. http://www.eagletreesystems.com/Plane/plane.html  This newest version provides a useable graphics display of flight parameters (even more useful if the data are evaluated in a spreadsheet) - your choice as to just what to look at. I typically log altitude, airspeed, and aileron inputs. 

The altitude inputs allow observation of entry / exit altitudes, altitude changes in level flight, diameter (height) of loops, cross over points, altitude loss / gain during spin entry, altitude loss / gain during rolls, etc. All basic stuff that's important to get right for good scores. Speed data provide clues as to where too much / little power is used and whether a prop works well or not. The aileron inputs can be superimposed on the altitude data to determine roll position on vertical lines. While not all pattern parameters lend them selves to analysis with this technology, a good deal can be learned with it.

While recently evaluating engine / prop combinations (very top secret), I noted something that looks useful regarding snaps. During both up and downline snaps the speed signal drops to zero for a period of time roughly equivalent to snap duration. It appears that possibly airflow separation from the wing includes the pitot tube. Upline snaps also show a marked decline in ascent rate during the snap. 

Recent snap discussions have made me curious, so I've decided to do some snap analysis with a G-force sensor connected to the logger. I've ordered the sensor and plan to take a good look at "real" snaps and barrel rolls. What to bet that the G loads spike quickly then drop dramatically during snaps, but increase throughout the barrel rolls? I'll present this work as a K-Factor article when finished, if anyone wants data sooner, a datalogger costs the same as a couple of servos. 

Earl
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