Competition Aerobatics - Basic maneuvers and this year's Primary Known

Time to start discussing what we fly in competition and how we fly it.  Part one: the basic maneuvers.  Here's this year's Primary Known routine, which covers three of the four basic competition maneuvers and a combination maneuver, as well as the aerobatic steep turn.

The diagram above (an Aresti depiction) shows six maneuvers, numbered in the order flown.  Maneuvers always start and end in level flight (true for all aerobatic categories), and start at the dot and end at the line.  While the maneuvers are flown in order, typically depicted top to bottom, the aircraft may in actuality hold altitude throughout.

There are only four basic aerobatic maneuvers which alone and combined form almost all competition maneuvers:  the roll, the loop, the hammerhead, and the spin.  There are just a few other maneuvers that don't neatly use or combine these four.  One example is the aerobatic steep turn, which is included in this Primary Known routine.  Straight lines can go horizontal, vertical or on 45 degree uplines or downlines.

Each of the six Primary Known maneuvers include challenges:

1.  The 45 degree upline.  Really a combination of 1/8th loop figures with a straight line section. This is used to slow the aircraft to near the stall speed, and is tougher to fly properly than it looks.  The radius of the pull up to the 45 line and the pitch back to level flight should be the same, which means a harder, faster pull to the 45 and a slower pitch to level to get the same apparent radius of the partial loops at beginning and end.  The pull into the 45 upline can easily hit 3 g's and the push back to level may be near 0 g or slightly negative.  During the climb the climb angle is judged not by track but by the zero-lift line through the wings, but the horizontal flight in and out is judged by flight line compared to the horizon, so that the slow flight at the end requires just enough nose-high pitch to hold altitude.  During the climb the deceleration changes the p-factor and thus the rudder input to hold heading increases constantly.  And you can't see anything over the nose so this is mostly flown looking out to the side.

2.  The spin. This is a one turn power-off spin, entered from level flight.  After the spin rotation ends the aircraft should continue to pitch down to a vertical line before the initiation of the quarter-loop recovery to level flight.  Problems: when power is reduced to idle in the level flight leading to the spin entry, the rudder input changes dramatically to hold heading (as the p-factor goes away); the pitch changes to hold a horizontal flight path up to the point of the stall (no climbing or sinking into the entry);the stall, drop of the nose into the spin and rotation should all start simultaneously, without the nose jerking up at the moment of the stall; the rotation should stop at one turn exactly, with no continuing yaw, followed by the nose pitching down to vertical; the recovery, while not hard, requires a pretty good 3 to 4 g sort of pull to hold the speed in check.  There's a lot here going on pretty fast.

3.  The half Cuban eight.  This is a combination of two basic maneuvers - the loop and slow roll (known to judges as an aileron roll to differentiate it from snap rolls).  5/8ths of a loop (which should appear round from the ground) is stopped momentarily at the inverted 45 downline, then a half-slow roll upright is followed by a little straight flight on the 45 downline before pulling to level flight.  The half roll should appear to be placed in the middle of the 45 degree downline, which is a trick as the speed is increasing throughout - it takes longer to draw the inverted portion of the line before the roll than the upright portion after the roll before the 1/8th loop pull to level.

4.  The loop.  This is supposed to appear round to a ground observer, which means the pilot has to adjust the rate of looping to compensate for speed changes in the aircraft and the effect that any wind might have to distort the loop.  Oh yeah, it is supposed to stay on heading also, with no rolling tendencies anywhere.  Not all that easy to do well!

5.  The aerobatic steep turn.  This is a roll to more than 60 degrees of bank (we usually shoot for about 70 degrees), then a stable, level steep turn, followed by a roll back to level.  No turn should happen during the rolling and no rolling should happen during the turn.  Tougher than it looks to coordinate properly and keep level.  We usually cheat with just a little "top" rudder to help hold altitude without having to pull more than 3 g's or so.

6.  The slow roll (judges call this an aileron roll).  This is a once-around roll where the aircraft is supposed to hold a constant pitch attitude and heading while rolling, which means lots of rudder and elevator input changes through the roll to keep the nose in line.  Again, much tougher to fly well than it looks at first blush.

Primary routines do not include hammerheads.  I've tossed an Aresti diagram here without explaining symbols as such, so some future blogging will include an explanation of these things, but I wanted to throw the easiest routine up here for starters and discuss why even the basics are challenging and interesting.  The diagram above is largely self-explanatory, but we'll cover more details later.

There's much more to discuss, but enough for now.  We'll break down Aresti figures and scoring methods and some judging standards in a later blog entry.

Happy looping - Don