As you enhance your aerobatic skills, you will naturally integrate components of diverse maneuvers within a single pattern. An example of such a technique is the Cobra Roll with a Half-Roll Up and a Positive Snap Down. Whether you are a novice or a seasoned aerobatic aviator, this maneuver is challenging. It not only mixes various flight positions of the aircraft, such as upright and inverted flight, but also demands you to concentrate on tracing a triangular trajectory while executing a half-roll in the initial portion of the sequence and a positive snap roll in the latter phase.
PRIOR TO GETTING STARTED
It is advantageous to adhere to the manufacturer’s recommendations for control surface deflections, exponential settings, and center of gravity for a specific aircraft. To execute this maneuver accurately, two different control surface deflection levels are suggested. At a modest deflection rate, the aircraft should behave moderately. For most aerobatic aircraft, this translates to approximately 12 degrees of deflection on the ailerons and elevators, around 30 degrees on the rudder, all coupled with 20 percent exponential. Then, for the phase during which the snap roll is executed, you should aim for roughly 30 degrees of aileron deflection, 20 degrees of elevator deflection, and approximately 35 degrees of rudder deflection along with 40 percent exponential.
While the deflection amounts and exponential settings may vary depending on the aircraft’s design, center of gravity settings, etc., these serve as initial guidelines that can be altered based on individual requirements.
The use of exponential is crucial for precise aircraft control. Utilizing the appropriate exponential percentage will soften the aircraft’s response near the central stick position, enabling maximum control as the stick is pushed further. It’s important to note that the point at which the response rate changes will vary depending on the exponential percentage employed.
A QUICK LOOK AT THE COBRA ROLL
Position the aircraft parallel to the runway, in inverted level flight against the wind, at an altitude of approximately 150 feet for a standard 60-inch aerobatic model. Adjust the altitude as necessary based on the aircraft’s size. Furthermore, ensure that the entire maneuver is centered in front of you. The highest point of the maneuver, which corresponds to the second radius and the transition from the 45-degree climb to the 45-degree descent, should be directly ahead of you.
As the aircraft nears the runway, increase the throttle slightly above cruising speed and apply further throttle only before initiating a 45-degree climb. At this stage, increase the throttle to between 75 and 100 percent and push to begin the 45-degree ascent. The throttle setting will depend on the aircraft’s power-to-weight ratio, so adjust as required. Once centered in the climb, execute a half-roll. Subsequently, as the aircraft aligns in front of you, push into a 45-degree descent, reducing the throttle to idle. Execute a positive snap roll during this phase, then pull up to complete the maneuver in upright level flight at the original altitude.
Now, let’s dissect this maneuver into five fundamental steps:
STEP 1: Increase throttle to around 60 percent and align the aircraft parallel to the runway with a headwind. Perform a half-roll to enter inverted flight on low rates. Given the inverted orientation, maintain a slight downward elevator input to sustain altitude. At approximately 300 feet away, increase the throttle to 75 percent and initiate a 1/8 loop push to establish a 45-degree climb.
STEPS 2 & 3: Carry out a perfectly centered half-roll on the upward path. While the roll direction is not critical, maintain a consistent roll rate throughout this phase. Additionally, apply elevator input to maintain the 45-degree ascent post-roll. Directly aligned in front of you, smoothly transition through a gradual 90-degree descent from the 45-degree climb.
Gradually decrease throttle during the descent to ensure the aircraft reaches idle by the time the 45-degree descent angle is established.
STEP 4: If utilizing the control settings mentioned earlier, switch to the snap-roll protocol. Perform a positive snap roll at the midpoint of the 45-degree descent. Executing a positive snap roll necessitates up elevator input along with coordinated aileron and rudder movements in the same direction. Once proficient in the snap roll, you can “unload” the maneuver by initially applying elevator, making pitch adjustments, and subsequently incorporating aileron and rudder movements while releasing elevator input.
Irrespective of your chosen method, release control inputs post-snap roll to return to the original setting.
STEP 5: Finalize the maneuver by executing a 1/8 inside loop to transition back to upright level flight at the original altitude, simultaneously increasing throttle to sustain consistent speed. Prepare for another sequence by maintaining throttle at 60 percent. Remember, practice leads to perfection!
If transitioning between rates during the sequence proves challenging, begin by flying the maneuver using the settings that offer ample control deflection for the snap roll. In such cases, increase exponential settings to smoothen the aircraft’s overall responsiveness and execute the maneuver seamlessly.
CONCLUDING REMARKS
This aerial display can be quite complex due to its multiple individual components. To master it successfully, break down each element until it’s perfected, and leverage all the advantages your computer radio provides. Most importantly, seek guidance from experienced aerobatic enthusiasts, and above all, remember to enjoy the experience.
BY JOHN GLEZELLIS
ILLUSTRATION BY SINELAB
