By coordinating rudder deflection with the aileron (rudder moving in the same direction), you prevent the nose from skidding to the left. Adverse yaw is thus prevented; banks and corrections, even rolls, will be smooth and axial, and you will feel more connected to the plane.

When a loop-or any maneuver related to one-is performed in a crosswind, the airplane will drift sideways with the wind during the slower portion of the loop. This drift will generally happen as the plane rounds over the top of the loop. Consequently, a loop that was entered on a parallel flight path with the runway will exit downwind-no longer tracking parallel. If you don’t use the rudder, you will have to do a number of corrections afterwards to reestablish the preferred parallel track taken at the start of the loop.

To correct cross-wing drift, apply rudder in the opposite direction the wind is blowing. For example, if the crosswind will blow the plane to the left, a right-rudder wind correction would prevent it. Ailerons are for keeping the wings level before and during a loop. Don’t try to correct wind drift by creating a new [wing] deviation using aileron; sideways wind drift is a function of yaw, not roll.

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Next, understand that the “propwash,” generated by the turning propeller, spirals around the fuselage and strikes the left side of the vertical tail, thus producing a strong left yaw tendency during hover. Consequently, you’ll need constant right rudder inputs to keep the fuselage vertical. (Note: Building in a couple degrees of right thrust lessens the effect of the propwash while hovering, but it does not eliminate it.)

A great deal of the propwash also strikes the underside of the left stab, causing the plane to pitch forward during hover. Therefore, barring any wind, you can expect to regularly need up-elevator along with right rudder to keep the fuselage vertical while hovering.

There is also considerable left rotational torque while hovering, so you’ll need to hold in large amounts of right aileron to keep the wings stationary. If the plane continues to torque to the left despite holding in full right aileron, you may have to increase the right aileron travel. If you can’t keep the plane from torquing even with full aileron, you’ll have to boost the throttle higher each time the plane starts to torque to further increase the effectiveness of the ailerons.

CONTROL TECHNIQUE

The standard entry into a hover starts by slowing the airplane and then abruptly pulling to vertical, causing the airplane to suddenly stop all forward movement. Be aware that you most likely will need to input some right rudder and aileron to counter the propeller forces while pulling up to vertical. Then immediately start pumping the throttle to maintain the same height as well as control.

A hover will quickly unravel if you are late correcting a deviation, so keep your fingers moving at all times, even when the airplane appears momentarily stable. This will make sure that you’re always ready to respond to deviations the instant they occur.

As a rule, if the tail swings more than five degrees from vertical while hanging on the prop, it will be very hard to stop the deviation due to the pendulum effect. To minimize over-controlling, you must try to limit your rudder and elevator corrections during hover to small brief bumps or jabs.

If a deviation is larger than five degrees and requires a larger correction, any large correction will have to be immediately followed by a quick opposite jab to keep the response from escalating.

Try to limit over-controlling by keeping your inputs tiny and brief, and if you must input a larger bump, immediately input an opposite bump to limit the response.

ADVANCED HOVER TIPS
Since a sustained hover demands immediate corrections, use of too much expo will delay the control response and thus hinder hover success. If you feel that the plane is lagging behind your control inputs, reducing the expo settings will likely improve your ability to hover.

CG Considerations

It has long been said that an aft CG makes an airplane easier to hover. While a tail-heavy condition helps flat spins and tumbling maneuvers, after years of 3D flying and testing, neither an aft nor forward CG has proven to have much impact on hovering flight. In fact, more and more professional 3D pilots set up their planes these days slightly nose-heavy to make them more predictable and less erratic. All things considered, most pilots are best served to go with a “neutral” CG (near the wing’s thickest point or approximately one third of the wing chord) to achieve the best overall performance.

Although it’s rarely possible to achieve a perfectly vertically balanced airplane, i.e., with the tail hanging straight down, getting it as close as possible can make the airplane lock into a much easier hover. If you can, try to position the batteries and other items as high as possible in the fuselage to offset the weight of the landing gear, etc.

On the other hand, if over-controlling seems to be a persistent problem, i.e., the corrections you make typically end up causing more deviations. To solve this, in addition to practicing smaller control inputs, try increasing your expo percentages.

If your airplane exhibits an especially strong tendency to pitch forward while hovering, putting in additional up-elevator trim will certainly help. But the trick that works best is to aim to hover with the fuselage tilted a couple degrees toward the canopy.

Some 3D pilots like to determine the exact power setting that their airplane hovers at and then they flatten the throttle curve a bit around that setting to make the throttle less sensitive. On a similar note, using a lower pitch propeller affords a larger power sweet spot during hover in which the throttle is less sensitive and therefore less prone to over-controlling.

CONCLUSION

To avoid over-controlling, try to limit your rudder and elevator corrections to small, brief bumps or jabs when working to keep the fuselage vertical during hover.

While there will always be pilots who try to impress others by throwing the sticks into the corners until altitude forces them to recover, they don’t come close to knowing the satisfaction that comes from learning to hover. It may be challenging, but you can take confidence from knowing that you’re now armed with the knowledge to learn at a rate much faster than most! Good luck.

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After the airplane has made it past the top of the loop, idle the engine to slow the descent and get ready to quickly neutralize the elevator at the instant the plane points straight down. Despite the throttle reduction, airplanes tend to quickly build speed when pointing straight down, so hold the lines before and after the half-roll no longer than a count of “one.” Flying a perfect vertical downline is the mark of a professional-caliber P loop. If you do not have the time to display at least short vertical lines before and after the roll, you’ll have to enter the maneuver higher and/or fly much larger loops to enter the downline higher up. You think of it this way: if you don’t have enough altitude to dive straight at the ground, perform a half roll and pull out, you probably don’t have enough height to perform this version of the P loop. This is what we mean when we talk about “thinking ahead of the airplane!”

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During a sustained knife-edge, altitude is maintained with “top rudder,” the force of the air deflecting off the side of the fuselage and the upward component of the engine thrust. This is why a great deal of airspeed, thrust and rudder (yaw) are typically required to maintain altitude in knife-edge flight.

Before we go any further, we need to do away with the popular but ambiguous reference to “using the rudder like an elevator” during knife-edge flight. Instead, simply remember that the rudder is always applied the opposite direction that the airplane is rolled-regardless of whether the top or the bottom of the plane is facing the pilot. So, if you roll 90 degrees to the right, you’ll input opposite left rudder to maintain altitude.

By definition, the most important aspect of knife-edge flight is establishing a perfect 90-degree bank. You can quickly get a handle on this by rolling to knife-edge without worrying about the rudder for the first few attempts. When you first introduce rudder, it’s again crucial that you first establish a 90-degree bank before inputting rudder, and thus avoid the tendency to over- or undershoot the bank because you’re rushing to input rudder. At first, you may even want to briefly pause at neutral after rolling to knife-edge to make sure the wings are perfectly vertical before you apply rudder. If you become confused or you need to recover, neutralize all the controls, and then roll back to upright.

Maintain altitude during knife-edge by simply remembering to apply the rudder in the opposite direction in which you applied the aileron.

The airplane is trying to roll out of the bank (typical). Plan to hold in a little right aileron next time.

Second attempt: Enter a slight climb, bank right 90 degrees, input opposite left rudder and add a little right aileron.

The plane stays banked 90 degrees, but tucks (turns) toward the landing gear. Plan to pull a little up-elevator next time.

Third attempt: Enter a slight climb, bank right 90 degrees, input opposite left rudder, add a little right aileron and pull a little elevator.

For future attempts, make a more shallow entry, and smoothly blend the inputs together.

BUILDING A SUSTAINED KNIFE-EDGE
Factors such as propwash, gyroscopic precession and P-factor won’t let most airplanes stay on their sides and/or track straight in knife-edge flight with just rudder input. But determining which corrections are needed to hold a straight line is easy as long as you don’t clutter your attempts with too many inputs; instead, build on what the airplane shows you it needs. In knife-edge, the best teacher is the airplane.

For example, enter a slight climb at full throttle. Roll right to knife-edge, neutralize the aileron with the wings perfectly vertical, then smoothly apply full opposite left rudder and hold it. Don’t attempt to correct any deviations at this time. You’ll most likely see the plane roll in the direction in which you’re holding the rudder, i.e., left. Rather than correcting it, record the event in your mind while forming a plan to correct it next time with right aileron.

Assuming that you successfully correct the roll tendency in your next attempt, it isn’t unusual to observe the airplane tucking toward the canopy or the landing gear. Just as you did with the roll tendency, take stock of the direction in which your airplane tucks and which way you’ll need to apply the elevator to correct this during the next attempt. Once you’ve identified the knife-edge requirements for your airplane and have developed some confidence, you can begin to gradually remove the climbing entry and start blending the inputs.

In its final form, a skilled pilot applies just enough up-elevator pressure at the start of the 90º-roll to prevent the plane from dropping, but is otherwise undetectable, while smoothly adding top rudder as the wings approach 90 degrees. Then, based on prior observations, he or she blends in the aileron and elevator inputs required to hold a straight line.

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Brief Bumps are Key!
Your rudder and aileron corrections must be brief. If you’ve watched car racing on TV, you may have noticed the in-car camera shots of a driver bumping or nudging the steering wheel. That’s because race cars are typically driven on the edge of control, and if the driver over-controls just once, he can send the car spinning out of control. To avoid spinning out, race car drivers make several smaller (bump) corrections rather than one larger correction. Similarly, an airplane teeters on the edge of control during most 3D maneuvers, and thus your rudder and aileron corrections must be kept brief to avoid aggravating the wing-rocking phenomena.

Elevator-Flap Mix An effective technique used to reduce wing rock is to activate the elevator/flap mix so both ailerons raise up approximately 20-30% when you hold in full up-elevator .While you’re at it, you might as well program both ailerons to lower 20-30% with down-elevator to complement future inverted 3D maneuvers.

Elevator Summary
Point the airplane into the wind, cut the power, and smoothly pull full up-elevator. When the plane stalls, add a few clicks of throttle to keep the fuselage level and hold in some right rudder to correct for propwash and P-factor. Correct deviations with brief bumps of rudder and use coordinated aileron and rudder inputs to correct larger wing deviations. Keep your fingers moving, and if the wings start to rock uncontrollably, exit the maneuver by relaxing the elevator and adding power.

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Rather than rehashing an ideal 4-point roll scenario, my intention is to crawl-walk-run pilots through the stages of practice that are required to perform outstanding 4-point rolls. You’ll also learn how to enhance your practice effectiveness by focusing your attention on controlling the airplane.

4-POINT ROLL BASICS

By definition, the main objective during a 4-point roll is to precisely stop the roll every 90 degrees. However, things happen too fast to perform accurate points when trying to react to the wings. Therefore, proficient pilots concentrate on timing their aileron control inputs to consistently hit the points. In other words, your first objective when learning the 4-point roll is to find an even tempo or drumbeat to input the aileron (in-out) that results in hesitations at each 90-degree point of the roll. Keep in mind that developing the correct timing becomes much easier when you pull up into a 20- or 30-degree climb before initiating the roll so that you are not distracted by altitude. A high-throttle setting is also preferable during point rolls to minimize the amount of drop when the airplane is paused on its side and inverted.

After reflecting on the results of your first attempt, go into the next with the appropriate speeding up or slowing down of your aileron inputs. For example, if you overshoot the points, you’ll need to apply your aileron inputs at a slightly faster tempo next time, and vice versa.

At this stage, neither a faster or slower tempo is more ideal. The correct tempo is whatever it needs to be for you to complete the fourth point with the wings level. You should also make sure you clearly define each point by pausing at neutral for a “count” before rolling to the next point.

HORIZONTAL 4-POINT ROLL

Once you possess the correct input timing of the basic 4-point roll, the next step is to “push” forward-elevator during the inverted second point to keep the plane level. To avoid barreling the roll at this point, make sure that you neutralize the aileron at the inverted second point with the wings level before adding the push. It’s very easy for a pilot to get so far ahead of himself thinking about the push, that he neglects to establish a good second point with the wings level. This ultimately results in a botched maneuver.

The addition of the push when inverted means you can start to shallow the entry as your confidence increases. The eventual goal is to pull just enough up-elevator at the start to keep the plane from dropping through the first part of the roll, but is otherwise undetectable.

UPRIGHT 4-POINT SLOW ROLL

When you have mastered the horizontal 4-point roll, start slowing down your tempo and use less aileron to slow the roll rate. You can add “top rudder” during the knife-edge points to keep the roll level. Forget the talk about using the rudder as an elevator when the airplane is on its side. Instead, simply commit to memory that the rudder is always applied in the “opposite” direction of the roll (aileron input) during the first point, regardless of whether the top or bottom of the airplane is facing you. The rudder is then applied in the “same” direction as the roll during the third point. Thus, if you’re rolling right, opposite left rudder is smoothly applied to maintain altitude during the first knife-edge. Don’t forget to smoothly push forward elevator when inverted, and smoothly apply right rudder (same direction as the roll) during the final knife-edge.

Keep in mind: the slower the roll rate, the slower the rudder and elevator inputs need to be applied and taken out. This is where maximum stick tension and paying attention to your control inputs really helps. The rudder inputs should be just enough to maintain level flight. Visible yaw is not the object; rather, the object is to locate and repeat the control inputs that consistently produce the best results.

It’s wise to enter your first several attempts from a climbing start to buy yourself more time to think. Remember, the most important aspect of the point roll is maintaining accurate points. At this stage, it’s very easy to botch the points when thinking about the rudder. Understand that refinements, such as rudder, only help to perfect an otherwise decent horizontal 4-point roll. If adding rudder causes you to botch your point rolls, rather than concentrating on improving the rudder, you need to refocus on the basics that lead up to adding rudder for “perfect 10″ attempts.

Another common mistake is neglecting to pull a slight amount of up-elevator at the start of the roll to prevent the airplane from dropping, instead of trying to keep it level with a large rudder input. Not only can neglecting the elevator at the start cause the airplane to descend, but also applying large rudder inputs well before reaching knife-edge can initiate a slight turn. Remember to input a small amount of up-elevator at the start of the roll to prevent it from dropping. The rudder should not be input until the wings are banked at least 30 to 45 degrees.

CONCLUSION

Most of the challenges that advancing aerobatic pilots experience are not due to their ability to master the finer points or the amount of stick time they have, but are caused instead by rushing or overlooking the fundamentals that got them to that point. Oftentimes, fliers who emphasize precise points and timely elevator inputs will have more success than those who may have more experience, but are constantly correcting the consequences of emphasizing rudder while neglecting the basics.

BY DAVID SCOTT

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