Aerobatic contest data statistical analyses and reports
The aerobatStats directory contains R code for
- an R package that queries International Aerobatic Club (IAC) aerobatic contest data published electronically as IACCDB and produces R data frames for analysis.
- measurements of goodness of fit to normal of judge grade distributions
The jgdfit directory contains development of a paper reporting
goodness of fit measurements from IAC contest data.
The power directory contains R code for a simulation study
using rounded data of the kind found in judge grades,
to measure the power of various goodness of fit to normal tests.
Aerobatics, as practiced by CIVA and the IAC, is a judged sport. In aerobatics, pilots fly figures made up of a basic flight path overlaid with rolls, in which the airplane moves about it's fuselage while it's center continues on the flight path.
The basic flight paths of the figures are made up of straight lines and loops. Straight lines may be horizontal, vertical, or along a forty-five degree line. Loops are segments of a circle of constant radius. They occur in transitions between lines. Their segments may form anything from one-eighth of a circle to an entire circle in one-eighth increments.
Rolls superimposed on the flight paths are subdivided into those in which the air maintains laminar flow over the surface of the airplane and those in which the flow is turbulent over part of the wing. The former are generally referred to as "aileron-rolls" or simply "rolls." The latter are referred to as "snap-rolls" or "flick-rolls", and "spins".
Aileron rolls and snap rolls may occur on any line, and at the top of full loops. Spins are always performed on a vertical line moving down. Rolls can occur in one-eighth increments up to two full rolls, and may be broken-up with pauses, called "points", in increments of one-eighth, one-quarter, and one-half of a full roll.
The sport maintains a catalog of flight paths and rolls named the "Aresti catalog" after its developer, Spanish aviator Colonel José Luis Aresti Aguirre. The Aresti catalog systematically assigns difficulty, a "K-factor" to each figure.
A "flight program" consists of each of the competing pilots flying a sequence of figures in front of the judges. The sequences of figures are predetermined for the flight program by any one of several methods. Judges receive the sequences that each pilot will fly in order to evaluate the sequence actually flown against the sequence commited to fly by the pilot.
The judges give each figure a grade from zero to ten in half point increments. They start from a perfect score of ten, and systematically deduct for flaws in the direction of the flight path, radius of loops, and degrees of roll. Thus, a flight program produces a three-dimensional matrix of grades consisting of Pilot X Judge X Figure. Each pilot receives one grade from each judge for each figure.
Aerobatic Competition Grades (illustration)
To complicate the grading slightly, a zero grade can take multiple forms. One form is that incremental flaws resulted in deductions that summed to ten or more. This is known as a "soft zero". A second form is that the figure flown did not match the figure that was supposed to be flown. It might have been missing a roll element or not have been flown along the prescribed flight path. This is known as a "hard zero". CIVA uses a form known as a "presentation zero" that a judge may use to indicate suspicion of a hard zero. A "conference zero" indicates that the judge changed their grade to a hard zero in review following the performance of the pilot.
A judge may also give a grade of "average". A grade of average indicates that the judge was either distracted or unsure of the figure that was prescribed to be flown and therefore unable to evaluate the figure performed against the figure prescribed. It is preferred that the judge give an average under these conditions, rather than make-up a grade. The effect of averages is a reduction in the number of judges evaluating the figure.