Half Cuban Eight Model pulls up and executes five-eighths (5/8) inside loop to 45 degrees, hesitates, does one-half (1/2) roll, hesitates, then performs one-eight (1/8) inside loop back to level flight in the opposite direction as entry. Downgrades:
Loop segments not round with the same size and radius.
Model not at 45 degrees before and after half roll.
Changes in heading in loop segments or after half roll.
Half roll not centered in 45 degree line.
No hesitations before or after half roll.
Before we start dissecting the maneuvers, a word from your friendly webmaster about aligning your aircraft. It is vitally important that you do everything in your power to ensure that your plane is set up to perform the next maneuver BEFORE you begin its execution. That includes all of the following:
Wings perfectly LEVEL
Flight path parallel to the runway
Altitude constant
I cannot emphasize strongly enough how important these things are to the Novice class flier. They WILL make the difference between scoring well and scoring badly.
Half Cuban Eight: Model pulls up and executes five-eighths (5/8) inside loop to 45 degrees, hesitates, does one-half (1/2) roll, hesitates, then performs one-eight (1/8) inside loop back to level flight in the opposite direction as entry.
Read that description carefully. Here's how it's supposed to be done.
Up elevator is smoothly added to make the plane fly a constant radius 5/8th inside loop to a 45 degree inverted dive. You will need to add down elevator at the completion of the loop to maintain the 45 degree down line
Fly a straight line in a 45 degree inverted dive.
Execute a one-half roll to upright flight.
Fly a straight line. This line is still on the same 45 degree down line and must be the same length as the line immediately before the roll.
Execute a one-eights (1/8) inside loop to level upright flight. Loop must be of constant radius, and radius must be the same as the 5/8th loop at beginning of maneuver. Exit altitude must be the same as entry altitude.
Now for the downgrades:
Loop segments not round with the same size and radius.
Both loop segments (1/8th and 5/8ths) must be of equal radius and must be ROUND!
Model not at 45 degrees before and after half roll.
Model must dive at 45 degrees. If the dive appears to be 45 degrees to the pilot, it's too shallow! That's because you're looking at it at an oblique angle, not straight on. If it is a true 45 degrees, it will appear more like 55-60 degrees from the pilot's perspective.
Changes in heading in loop segments or after half roll.
Model must remain parallel with the runway throughout the entire maneuver.
Half roll not centered in 45 degree line.
The two straight lines must be of equal length for the roll to be centered.
No hesitations before or after half roll.
If you skip either straight line segment (before or after the roll), deduct TWO points!
Half Reverse Cuban Eight Model pulls up and executes one-eighth (1/8) inside loop to 45 degrees, hesitates, does one-half (1/2) roll, hesitates, then performs five-eights (5/8) inside loop back to level flight in the opposite direction as entry. Downgrades:
Loop segments not round with the same size and radius.
Model not at 45 degrees before and after half roll.
Changes in heading in loop segments or after half roll.
Half roll not centered in 45 degree line.
No hesitations before or after half roll.
Before we start dissecting the maneuvers, a word from your friendly webmaster about aligning your aircraft. It is vitally important that you do everything in your power to ensure that your plane is set up to perform the next maneuver BEFORE you begin its execution. That includes all of the following:
Wings perfectly LEVEL
Flight path parallel to the runway
Altitude constant
I cannot emphasize strongly enough how important these things are to the Novice class flier. They WILL make the difference between scoring well and scoring badly.
Half Reverse Cuban Eight: Model pulls up and executes one-eighth (1/8) inside loop to 45 degrees, hesitates, does one-half (1/2) roll, hesitates, then performs five-eights (5/8) inside loop back to level flight in the opposite direction as entry.
Read that description carefully. Here's how it's supposed to be done.
At the completion of Straight Flight Out, up elevator is smoothly added to make the plane fly a constant radius 1/8th inside loop to a 45 degree climb.
Fly a straight line in a 45 degree climb.
Execute a one-half roll to inverted flight. You will need to add down elevator at the completion of the roll to maintain the 45 degree up line
Fly a straight line (inverted). This line is still on the same 45 degree up line and must be the same length as the line immediately before the roll.
Execute a five-eights (5/8) inside loop to level upright flight. Loop must be of constant radius, and radius must be the same 1/8th loop at beginning of maneuver. Exit altitude must be the same as entry altitude.
Now for the downgrades:
Loop segments not round with the same size and radius.
Both loop segments (1/8th and 5/8ths) must be of equal radius and must be ROUND!
Model not at 45 degrees before and after half roll.
Model must climb at 45 degrees. If the climb appears to be 45 degrees to the pilot, it's too shallow! That's because you're looking at it at an oblique angle, not straight on. If it is a true 45 degrees, it will appear more like 55-60 degrees from the pilot's perspective.
Changes in heading in loop segments or after half roll.
Model must remain parallel with the runway throughout the entire 3-maneuver set.
Half roll not centered in 45 degree line.
The two straight lines must be of equal length for the roll to be centered.
No hesitations before or after half roll.
If you skip either straight line segment (before or after the roll), deduct TWO points!
Now let's take a look at the Stall Turn. Here's the description directly from the Competition Regulations. The ellipsis (...) indicates that the part of the description dealing with rolls, as done in the higher classes, has been omitted.
Stall Turn Model executes one-quarter (1/4) loop to a vertical track, performs a stall turn through 180 degrees, then recovers with another one-quarter (1/4) loop to level flight in the direction. ... The length of the vertical segment is not a judging criteria. Downgrades:
Model not level at start and finish.
Track does not become exactly vertical.
Model not vertical at start and finish of ... stall turn.
Return path not parallel to entry path.
Exit not at same altitude as entry.
Pivot radius greater than 1/2 wingspan.
Pendulum movement after stall.
Loop segments not round with same size and radius.
There is more to this maneuver than meets the eye, so let's take a close look at this it, one section at a time.
Model not level at start and finish. As with every maneuver, the Stall Turn starts and ends with STRAIGHT AND LEVEL FLIGHT! You're probably getting tired of hearing me say those words, but get used to it. They are probably the most important words you'll read on these pages. If your entry is not straight and level, the rest of the maneuver will fall apart rapidly. It's also a downgrade. Get it right!
NOTE:The one-quarter loop begins on the center line! This is vitally important. It is easy for the judges to see where center is, and just as easy to provide downgrades when you miss starting the 1/4 loop there.
Track does not become exactly vertical. First, let's review the definition of TRACK: the trajectory or flight path of the center of gravity of the aircraft over the ground. Notice that it doesn't say anything about the attitude of the aircraft. They will be identical in no-wind conditions, but otherwise will be different to compensate for wind drift. Many new pattern pilots try to make the attitude of the plane vertical. If there is any wind, the plane will drift back in the downwind direction. This will bring immediate downgrades from the zebras -- oops, I mean judges. Sorry, too much football today.
Note that we are flying in three dimensions, so there is also an excellent possibility that the plane will try to drift left or right as well as backward. I don't know about your field, but the wind is seldom down the runway at mine. Left or right drift is corrected with Rudder. You know, the other control over on the left stick with the throttle. Use as much rudder as needed in the opposite direction from the drift to stop the drift. In other words, if the plane is drifting to the left (looking at the top of the plane), apply right rudder. One of my pattern cronies here on the Prairie was having trouble with his Stall Turns last summer and asked me for help. Every time he'd start to drift left, I'd say "Right Rudder!" He'd just keep drifting left, so I repeat my "Right Rudder" suggestion. After several attempts he finally said in exasperation, "I've got right rudder in it!" I told him "Put in some more!" Use whatever type and amount of control input it takes to correct the problem as quickly as you can, because it will only get worse if you don't.
Another possible culprit that causes right or left drift is our old friend and nemesis, wings level. If your wings aren't perfectly level when you start the 1/4 loop, the plane's heading will be off in the direction of the low wing. You've violated the "track being vertical" rule even before your start the maneuver. Remember, the track needs to be vertical, not the attitude.
NOTE: A word here about the loop from your friendly webmeister. Use a nice large radius on your loop. This will allow you and the judges to get a good look at the TOP of your plane during the vertical segment. This is very important in seeing any wind drift as soon as possible -- so you can correct it at soon as possible. It also presents the maneuver to the judge in a much clearer manner, and allows better timing of the stall turn.
Model not vertical at start and finish of the ... stall turn. This may seem a little strange, especially since the maneuver must be wind corrected. However, just before the stall turn, the model must be put into a perfectly vertical attitude relative to the ground! I know it sounds difficult, and it does require some timing and practice, but it can be done. The airplane must remain vertical throughout the 180 stall turn, then wind correction is reapplied as necessary.
Return path not parallel to entry path. The track of the airplane on the downward leg following the stall must be parallel with the upward track prior to the stall. Wind correct as required. If the wind is down the runway, down elevator will be required.
Exit not at same altitude as entry. Sounds elementary, but it is often overlooked. Following the 1/4 loop at the end of the downward line, the exit altitude must be the same as the entry altitude.
Pivot radius greater than 1/2 wingspan. When executed perfectly, the airplane should pivot about it's own Center of Gravity. The worst case allowed with downgrade is for the plane to pivot around its wingtip (radius of pivot = 1/2 wingspan). This requires some technique. There are two basic problems usually associated with stall turns. The first is the flop, caused by waiting too long before applying rudder, allowing too much airspeed to bleed off. Problem two is flying through the stall, not pivoting. This is caused by applying rudder too soon!
Here are two things that will help you with your stall turns.
Add a little throttle during the Stall Turn. There are several ways of doing this. One is to use the stick to give a couple of clicks of throttle just before the stall turn. Another is to set the throttle trim to a high idle during the maneuver. This is your webmeister's favorite, and it's particularly simple if you have a computer radio. Simply mix Throttle into Throttle and control it with a switch -- just flip the switch to high idle during the turnaround preceding the stall turn and flip it back to low idle during the next turnaround. That let's you maintain the low idle setting needed for takeoff and landing, but still give the extra boost needed for the stall turn. Both of these methods will cause airflow over the rudder during the stall, increasing it's authority and giving a much cleaner stall.
Practice, Practice, Practice!!! There is no other way to get the timing correct than to practice it until you can do it right every time.
Pendulum movement after stall. This occurs because the rudder stick is released and snapped back to center after the stall. There are two remedies for this condition. Try both and see which one works best for you.
Hold the rudder in until the stall is completed and the airplane is heading down, then release it slowly! This will hold the nose of the plane slightly past vertical after the stall, but at least the tail won't waggle.
Release the rudder during the stall. After the plane starts to pivot, approximately when the nose of the airplane is horizontal, start releasing the rudder. All of the rudder should be released when the nose of the plane reaches vertical. This is your webmeister's favorite, and has been for many years.
Loop segments not round with same size and radius. This should be a no-brainer. Both the 1/4 loop at the beginning and at the end of the stall turn must be the same size. It's harder to do than the say, so get out there and burn some fuel.
Here's the description of the Immelmann Turn directly from the Competition Regulations.
Immelmann Turn The model starts the Immelmann flying straight and level, pulls up into one-half (1/2) loop immediately followed by one-half (1/2) roll and finishes flying straight and level and exactly 180 degrees from the heading at entry. Downgrades:
Model not level at start.
Model deviates left or right during half loop.
Half loop not completed exactly above point of commencement of half loop.
Half roll does not commence immediately after half loop.
Plane deviates from a straight line during roll.
Model does not finish in level flight.
Model heading does not finish exactly opposite the direction of entry.
Half loop not round.
In Novice and Sportsman class, maneuver does not start at center line.
Next we come to the Immelmann Turn. This is a relatively simple maneuver, but there are many opportunities to mess it up. Read the description above, then let's look at the downgrades and see how it's supposed to be done.
Model not level at start. Here we go again - same song, 53rd verse! Straight and level flight is absolutely the single MOST IMPORTANT thing you can do to improve your scores.
Model deviates left or right during half loop. Again, entering the maneuver without having the wings level is one of the primary culprits here. If you do enter with your wings level, any cross wind will require you to make corrections with the RUDDER. Make them as soon as you detect ANY change from the desired heading so that only small corrections are necessary. Use as much rudder as required to correct the problem.
Half loop not completed exactly above point of commencement of half loop. If the loop is not round (see #8 below), the 180 degree point will not be exactly above the 0 degree (entry) point of the loop. It will vary to the left or right of the entry point. This requires varying the amount of elevator applied throughout the maneuver to achieve a round loop. Wind speed will cause the amount of elevator required to vary dramatically. Additionally, if a deviation as described in #2 above is not corrected, the exit of the half loop will be displaced either in toward the pilot or out away from the pilot from the entry point.
Half roll does not commence immediately after half loop. Here's an area that separates the men from the boys on the Immelmann Turn. The roll must begin immediately after the end of the half loop. That means absolutely NO straight inverted flight before the roll starts. This will cost you at least one point and often more depending on the length of the straight inverted portion. You must be aligned with the entry flight path and ready to roll when the half loop is completed.
Plane deviates from a straight line during roll. This should be self-explanatory. However, getting your plane to roll axially (around the center line of the fuselage) requires some trimming of the ailerons. Differential throw will be required to optimize axial roll characteristics. That means you need more UP aileron travel than DOWN aileron travel on each side. This can be dialed in if you have a computer radio, but what if you don't? The pushrod must be attached to the servo arm behind (toward the rear of the plane) the center of servo rotation if the aileron servo is mounted on the top of the wing, as on an Ultra Sport, Kaos, or Escape with a single servo. If the servo is on the bottom of the wing (as on high wing plane or with a servo for each aileron mounted on the bottom of each wing panel), the attachment point must be forward of the servo's center of rotation. The amount of offset determines the amount of differential - finding the right amount is a trial and error process.
Model does not finish in level flight. This can happen in several different ways. You will end up diving after the roll if you over-loop (loop more than 180 degrees). Conversely, you climb if you loop less than 180 degrees. Even if your loop is correct, you can still mess things up by not rolling exactly 180 degrees to upright, level flight. Practice, Practice, Practice - with a coach!
Model heading does not finish exactly opposite the direction of entry. This happens primarily when the aircraft won't roll axially. IF the airplane has too little aileron differential (for example, the same amount of up and down travel), the plane to yaw (pivot as if moved by the rudder) in the direction of the roll, creating a barrel roll. Yaw in the direction opposite the roll will occur if too much differential (for example, if only up aileron and no down aileron) is used. Either of these will cause problems on rolls and cost you points.
Half loop not round. See #3 above.
In Novice and Sportsman class, maneuver does not start at center line. I can't stress the importance of this highly enough. Most beginners want to let the plane get well past the center line before starting the half loop. It's easier to see that way, but will cost you a bunch of points. The maneuver must start on center!.
Split S Model performs one-half (1/2) roll in level flight then immediately executes one-half inside loop to level flight in opposite direction as entry. Downgrades:
Half roll not 180 degrees.
Half loop not started immediately after half roll.
Half loop not constant radius.
Changes in heading.
One-half (1/2) roll not in level flight.
Model heading does not finish exactly opposite the direction of entry.
Now for the Split S. This is basically an Immelmann Turn done backwards. Read the description above. Here's how you should perform this maneuver:
Enter from straight and level flight.
Reduce the throttle to idle.
Roll 180 degrees to level inverted flight.
Allow the reduced throttle setting and gravity to start the loop for you. Resist the temptation to add elevator yet.
Gently add up elevator during the first quarter loop. Maximum elevator deflection will be needed when the aircraft is pointing straight down.
Gently reduce up elevator during the last quarter of the loop. If you maintain the elevator used on the first quarter loop, the loop will tighten (decrease in radius) on you and won't be round.
Recover to straight and level flight and increase throttle.
Now let's check out the pitfalls.
Half roll not 180 degrees. Should be self-explanatory. Roll exactly 180 degrees to inverted flight!
Half loop not started immediately after half roll. No straight flight is allowed before beginning the loop -- the loop must start immediately after the completion of the roll.
Half loop not constant radius. Means just what is says -- make it round!
Changes in heading. This can occur during the roll or during the loop. Use rudder as required to maintain heading.
One-half (1/2) roll not in level flight. Roll must start exactly at the completion of the half loop -- not while climbing (over looping) or diving (under looping).
Model does not finish in level flight. Straight and level flight one more time -- same song, 54th verse!
Model heading does not finish exactly opposite the direction of entry. Heading on exit must be 180 degrees from heading on entry.
Half loop not round. See #3 above
Provided by R/C AIRCRAFT MODELING
