Harrier Roll, The

Model Airplane News, Jul 2005 by Somenzini, Quique

Freestyle aerobatic technique

3D AEROBATICS WAS BORN ON THE DAY THE HARRIER MANEUVER WAS PERFECTED. At the time, I called it the "cobra," but it soon became more popularly known as the "harrier." The harrier roll grew out of that basic maneuver, and it is one of the most spectacular 3D moves you can add to your flight routine. Like all demanding maneuvers, it requires a lot of practice to nail down. In this article, I'll take you through the finer points of the maneuver.

WHAT IS A HARRIER ROLL?

It is important to understand that the harrier roll is a 3D maneuver that requires the airplane to be in a nose-up attitude, i.e., more than 35 degrees, while it maintains a constant altitude during the entire maneuver. If the nose is not that high, you are simply doing precision rolls.

The harrier is 3D flying at its best because it requires a true mix of lift and propeller thrust to keep the airplane in the air at well below the model's stall speed. While flying at a very low forward speed, the nose must be held up; a lot of elevator throw is needed to keep the airplane in the harrier attitude. Now, simply do an aileron roll at the same time, and you turn the harrier into a harrier roll.

Basically, all a pilot needs to do is to keep the model's nose high-between 35 and 60 degrees-while the airplane rolls continuously. This is easy to explain but difficult to do.

HOW IT'S DONE

As always in aerobatics, perfecting a maneuver takes a combination of pilot skill, proper technique, airplane setup and airplane design. Of course, a lot of practice is also required.

Technique. To keep the airplane in the nose-high attitude during the roll requires a graceful mix of risk and finesse. You have to use all four control functions-rudder, elevator, throttle and aileronwith great coordination.

If you roll to the left, the airplane will be able to roll faster at a slower airspeed because of engine torque. Start at an altitude that's comfortable for you but not too high. You'll want to keep the airplane close enough to see what's happening. Throttle back to reduce the airspeed, select your high-rate mode, and pull upelevator slowly to lift the nose (but not so much that the aircraft starts to climb). Maintain your entry altitude. Keep pulling until you reach a nose-high attitude of 30 to 35 degrees. By now, the airplane has stalled, but by adding power, you can prevent it from losing altitude. You have just entered the 3D aerobatic world!

If the airspeed is correct, even with high rates (with aileron travel at around 40 degrees), you should have a constant roll rate of about 1 to 1.5 seconds per roll. Use full left aileron, and maintain the nose-high position until you've completed the first roll. When you see the airplane start its roll, add right rudder, but don't go to neutral elevator until the airplane reaches the first knife-edge position. Full right rudder now maintains the nose-high attitude. As you go from knife-edge to inverted, decrease right rudder and push in some down-elevator to keep the nose up. Now, from inverted to the second knife-edge, proportionally reduce down-elevator while transitioning from neutral rudder to left rudder. You should have neutral elevator and full left rudder when you enter the knife-edge position. Continue from knife-edge to upright, and keep doing the same thing: reduce rudder deflection and increase up-elevator until the airplane reaches a fully upright position again.

So, remember: use elevator inputs to maintain a nose-high attitude in the upright and inverted positions, and use rudder inputs in knife-edge positions. How much elevator and rudder travel you'll need will vary and will depend on the airplane's position. You should have neutral elevator during knife-edge and neutral rudder when upright and inverted. Positions between knife-edge and inverted/inverted require a mix of the two inputs. For example, while in the 45-degree position between inverted and knife-edge, elevator and rudder are both deflected by about the same amount. As you approach the knife-edge, rudder deflection must be increased and elevator decreased.

The technique for flying consecutive rolls is the same; it requires repetition. Once you get the coordination and rhythm down, you will be able to make as many rolls you want. To exit the harrier roll, add full power and reduce elevator to transition into normal forward flight.

Power management. During the maneuver, you'll see that the airplane will slow down because of the added drag generated by the aileron, rudder and elevator deflections. Increase power to maintain altitude and the slow forward motion. I suggest that as soon as you start to roll, you add three or four clicks of power, and keep an eye on the airspeed. If you see that the model is losing airspeed, or you feel that you can't keep its nose up-even with full control-surface deflections-add power. Another symptom of insufficient power is that the aileron roll rate will be too slow. With proper throttle management, your airplane will feel light.