by Glenn Carter, IMAC Technical Director

The following data is offered to help our members in flying Aerobatics from beginners in the Basic category to Unlimited and 3-Minute Free enthusiasts.  It is our intention to promote better piloting skills along with safety and enjoyment of the sport.

Let's start by listing many of the terms and rules of aerobatics.......

1.     Altitude is controlled by throttle. With any given elevator setting, you will gain or lose altitude with throttle variations.  Experiment with this yourself.  It can be particularly valuable in final approach to landings and go-around.

2.    Air Speed is controlled by elevator (trim) settings.  A nose up attitude will produce a slow air speed; nose down will increase your air speed.  It should be noted that pulling the nose up will not only slow the aircraft, but will cause a more rapid descent!  Keeping the nose down will extend the ground covered (with higher air speed/ground speed) and substantially increase the distance traveled.  This is valuable information in setting up your landing approach or when trying to stretch the glide back to the field.

a. You may trade airspeed for altitude or altitude for airspeed!

3.    Attitude is established with elevator trim and my be called your airspeed control.  It should be (is) always adjusted for various throttle settings whenever changed for slow flight, cruise, or full-bore climbing/diving aerobatics.

4.    Throttle is essential in aerobatics.   Scoring well and positioning maneuvers within the 120° box will require many throttle variations.  Decreasing throttle on down lines and increasing it for up lines will allow you to maintain a nice constant speed throughout the entire sequence.   Horizontal rolls and snap rolls should be done at reduced throttle.  Be sure that all rolls are in the middle of any given line (45, 90, etc.) with an equal distance before and after the roll on that line!  Plan ahead for these by marking your call sheet and practice with the caller frequently until it becomes familiar and automatic.

5.     Torque and "P" factor simply tend to pull the aircraft to the left when abruptly giving full throttle as in takeoffs and go rounds.  Avoid this by advancing the throttle slowly.  Also be aware that these forces will pull left in any climbing maneuver and will become more severe as your airspeed decreases.  You can correct for it with right rudder (eased in gradually) on the way up as you maintain a vertical line.  In inverted climbs, left rudder will be needed for negative P-factor.

a.  If you roll left on a vertical up line, hammer to the right or vice versa.   Your rudder will have much more authority that way and allow a better pivot.   Experiment with your aircraft to see which procedure is best and most reliable.   Biplanes often need a little opposite aileron to keep them from rolling out at the top.  They also require some opposite aileron while holding points on horizontal point rolls.  It is necessary if you wish to hold your points for several seconds or when sustaining knife-edge flight.

6.     Unusual Attitudes are frequently encountered in aerobatic practice.  If you wish to abort a maneuver or get out of an uncomfortable situation, there is but one way to do it.  First level the wings, then apply elevator to level the aircraft and adjust throttle back or ahead to reduce or gain normal air speed.  Come off on the throttle immediately if your vertical descent is excessive!

7.    Angle of bank will drastically reduce lift and increase stall speed:

In level flight your stall speed may be only 20 mph
In a 40° bank, your stall speed increases to 40 mph
In a 60° bank, your stall speed increases to 60 mph and the nose will go down!

In each instance, a slower air speed will cause a spin-in crash!  So, you had better maintain plenty of air speed if you plan to rack-it-over in a steep bank close to the ground.

a.  Remember, no steep turns when low and slow.  Make turns gradual and keep it flying.

8.    Emergency measures.  If rudder or aileron control is lost, simply switch to the remaining control that is operative.   If the elevators jam in a down trim position, roll to inverted and walk it in with throttle and aileron or rudder applied gently.  Flame outs require an immediate reaction to judge the distance back to the runway or at least a turn into the wind.   Use down trim to get more distance out of your glide until touchdown is inevitable; then flare gently to reduce ground speed at touchdown.  The wind can be a real friend in such situations if you use it to your advantage, landing into the wind, no matter what other options are possible aside from brick walls or pit area avoidance.

9.    Looping maneuvers can always be best performed into the wind.  Rolling maneuvers are stretched and look better done downwind.  Spins will stall level and drop for more points into the wind.  Use throttle liberally to reduce downward speeds and increase upward speeds for more consistent and graceful sequences.

10.    All maneuvers start with a score of 10.   Reductions are imposed in relation to the severity and number of errors observed!   Positioning, lines and angles, must be precise: level, -45 to 90°.    Rolls must be centered on lines and entry/exit arcs a consistent radius with established entry/exit altitudes adhered to.

a. Positioning of maneuvers is critical.  Center maneuvers are performed directly in front of the pilot and judges, no more than 500' out or high.  Turn around must be within the 120° boundaries or a reduction in score will occur.  Zero a maneuver that is entirely out of the box.  Rolls should be half complete at the center point and figure eight's should have the crossover point centered.  Minimum altitude is 20'.

11.     Spins. Reduce throttle to a reliable idle.  Maintain level flight by adding up elevator gradually until plane stalls.  Apply full rudder as plane stalls and drops in the spin (some will require aileron as well as rudder).  If done correctly, the plane will drop into a true spin with no pitch up as in a snap roll entry and zeroed maneuver or a spiral dive which also is zeroed.  To recover on heading, neutralize all controls about a half turn before heading is reached.  Continue the downline until flying speed is regained and recover on heading.  Rushing the pull out with up elevator or opposite rudder may cause a secondary spin in the opposite direction and not enough altitude for recovery.

a.  Inverted spins.  From upright entry require the elevator and rudder to be reversed and opposite aileron applied after the aircraft stalls in the normally induced spin configuration (above).

b.  Inverted spins from inverted entry are accomplished by forcing the stall with down elevator (forward stick) and applying opposite rudder and aileron for the duration of the spin.  Inverted spins go in direction of rudder.  Recovery may be upright or inverted as required after extended downline.

c.  Flat spins develop from a normal spin be reversing the aileron input and applying full throttle.  Reduce throttle for recovery.

d.  Inverted spins require right rudder/left aileron and down elevator if you want to go flat as the engine torque also keeps the nose up.  Upright spins can be done in either direction., but will recover more quickly from right turns.  Avoid having your CG too far aft as it can make spin recovery impossible!

12.    Axial Rolls.  Adjust your aileron travel to produce the most desirable roll rates (usually about 2 seconds for 360°).  Apply full aileron, and just before the aircraft gets too inverted apply a touch of down elevator and release it just after it goes beyond the inverted to keep the nose up and the roll level.  Do this for single rolls until you find out how much down is required.  Then do three consecutive rolls, timing the application of down and the release of aileron to finish with the wings level.

a.  Point Rolls. First try the 2 point, releasing the aileron control as the plane gets to inverted and maintain inverted flight for several seconds with a little down elevator before rolling back to upright.

13.    Slow Rolls.  Apply about 1/4 aileron (or set your dual rate) to produce about a 4 second roll.  The rudder becomes the pitch control in the first quarter of the roll as you pass through 90° (wings vertical), at which time you apply a touch of top rudder.  Then, as you go inverted, a touch of down elevator.  Then another touch of top rudder as you pass through 90° again on the third quarter of the roll.  When you are in a right 90° bank, left rudder is effective top rudder or up elevator.  When in a left 90° bank, right rudder is effectively up elevator.  Whenever the aircraft is in a sustained (wings vertical) bank, the rudder acts as the pitch control like the elevators normally do.   Use a small hand held model to help visualize this.

14.    Knife edge is merely sustained flight in the wings vertical position and should be understood before entering multiple point rolls.  As with the above described slow roll, the rudder become the pitch control.  After rolling to 90°, apply just enough rudder to maintain level flight.   Visualize now how the elevators will be steering the aircraft on the yaw axis as the rudder normally would.

a.  Most aircraft will require some opposite aileron be held for the duration of any sustained knife edge flight.

15.    Point rolls are accomplished by hesitating at 90°, inverted (180 and 270° for a 4 point, and every 45° for an 8 point roll.  Simply refer to the control inputs described for slow rolls and knife edge flight and apply them here.  All of the data apply with just the hesitations added.   (How about a 3 point or reversing 2, 4, or 8 point?)

a.  An easy way to remember which rudder control comes first is:  "Rolls get opposite/down/same rudder input".  That is in relation to direction of roll.   When rolling right, give left rudder first (down elevator), then right rudder and vice versa.

16.    Barrel Rolls are corkscrew rolls aimed 30° around a point on the horizon like a barrel.  Use a small amount of up elevator, aileron and/or rudder to steer toward an imaginary circumference of a circle ahead of the aircraft.  The wings should be vertical on either side and inverted at the top.  Don't allow the nose to go to the side over 30° or it will look like a bad loop.

17.    Hammerhead turns.  Pull up to vertical, make sure your wings are level before the pull, and continue the up line.   A tad of right rudder may be required to maintain a good vertical line.  A tad of right rudder may be required to maintain a good vertical line.  As the aircraft reaches zero air speed, apply full left rudder and reduce power to idle.  Most models require a power reduction on the up line also.  Some opposite (right) aileron may be needed at the top to prevent rolling out and to keep the wing pivot vertical.  A good one will pivot within two wing spans at the top.

a.  Note: Aircraft does not stall!  Some power is maintained for the rudder to effectively pivot the aircraft as its upward progress stops.  Hang on to a little rudder briefly on the down line to avoid waggle.

b.  If a roll or snap is to be done on the up line, do them to the right or opposite the pivot direction for greater authority of the rudder in performing the pivot.   Always pivot into crosswinds.

18.    Snap/flick rolls are likened to a horizontal spin requiring the same control inputs.  Reduce power in level flight and simultaneously apply full up elevator and rudder (adding aileron will speed up the snap).   Neutralize all input within ± 1 second to stop with wings level.  Hold inputs a little longer for 1 1/2 or 2 snaps.  Proper timing is the key factor in ending them with wings level.

a.   Consecutive snaps.  First yaw the aircraft with rudder, then apply somewhat less elevator and release briefly between snaps.

b. Outside snaps are accomplished with the application of down elevator and rudder (± opposite aileron).  They can be done on any  plane of flight, but are normally performed from inverted attitudes.  It is wise to practice snaps at the top of a loop to begin with.

19.    Humpty bumps are vertical maneuvers with a half loop at the top.  The half loop may be a "pull" (positive G) shown in Aresti notation with a sold line or a "push" (negative G) half loop shown with a dashed line ----.   All sequences will show what is required and judges must be aware of the variations possible.

a.  Multiple, quarter, half, three-quarter,  and hesitation rolls or snap rolls may be added to the up and /or down lines with exits upright or inverted.   consequently, the maneuver must have a precise description which defines it, not just "a humpty bump."

20.    Practice makes perfect.  We all know this to be true.  We advise you to fly at least "two mistakes high" while learning to fly aerobatics.  There is nothing as useless as the sky above you or a runway behind you.  So, don't be like the guy that all at once ran out of "Altitude, air speed, and ideas!".  It could ruin your day.

a.  Consult a proficient aerobatic pilot or instructor before you attempt some of these maneuvers.  Also, don't increase your control movement or move your CG back too far, either can be disastrous.

b.  Select an aircraft suitable for aerobatics.  Build it strong and light.   "Build it to fly, not to with stand a crash!".  It can't be done.   Join with the members of the International Miniature Aerobatic Club and enjoy flying that emulates full scale aerobatics.

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