Tuesday, November 23, 2010

The Harrier

Hey Everyone! I recently got a suggestion from a friend of mine saying that I should go through each 3D maneuver, and explain a good set up and some simple tips to follow while learning to do that maneuver. After reading that suggestion I remembered that that was the original reason why I started the blog. So here goes.

The Harrier is pretty much the basis of most 3D maneuvers. This maneuver is probably the one you should learn first, for it is simpler than most of the others. Although I learned to hover before I learned to harrier, I think I should have done it in reverse order, because I never was proficient with anything but hovering until I learned to harrier. So if I had learned to harrier, I would have progressed into 3D a lot quicker and with less hassle than I did.

First off, if you are a new 3D pilot, be sure that you are using your beater airplane that has generous wing area, such as a 3D Hobby Shop Extra SHP. This plane is their "3D Trainer" and I highly recommend this airframe for any new 3D pilot. I own one too and love it!

Second, make sure you have adequate throws. If you are using the SHP, about 40-45 degrees on all surfaces for high rates is optimal.

Next is CG. Refer to my "Finding the right CG for 3D" article for tips on that.

Okay, now for what we've all been waiting for. If you are using a small electric like the SHP, there is a visibilty limit on how high you can go, but start as high as you can so that you still know where the plane is pointed. Then, since you are up high, pull the power back to about 1/4 throttle and let the plane slow. As it slows, don't let the nose drop, feed in up elevator. Now if the plane starts to descend, add power gently. Don't bang it wide open or you will over power it and end up climbing or doing a loop... and then it can get ugly... or worse!

Once you kind of get the idea for how your plane reacts at low speed, bring it down a little, but not too low. About 30ft should be okay. Do the same and try and hold your altitude with your throttle.

Now I'm going to give you a quick run down on the physics of wing rock. Wing Rock is the phenomenon that occurs during low speed high alpha maneuvers (like the harrier or elevator) when the wings rock from side to side. The reason for this is because each wing is not created equal, no matter how hard they try. One wing at these slow speeds will always stall first, so it drops. As it drops, it not only rotates on the "z" axis (aileron roll axis), but also yaws on the "x" axis (rudder). So the plane isn't just dropping a wing, it is also yawing in the direction of  the stalled wing.

So back to the wing rock topic, once the wing stalls and drops, it picks up speed, which turns into lift, and the wing regains flight. But as it regains its lift, the other wing has lost the airflow needed to keep it from stalling, and down it goes.

At first glance, your reaction would be to correct with just aileron. The truth is, although this will correct the rotation around the "z" axis, it will not correct the yawing action on the "x" axis. Correcting with aileron will make for a not-so-fun game of trying to correct aileron, and then randomly correcting heading with rudder. To make this easier, when the left wing drops, add both right aileron and right rudder; this will fix both problems.

Now, since the atmosphere we are flying in is not a controlled environment, and added in with factors like torque and drag, this system is not something to follow exactly. This should  be in the back of your mind when you are flying, and also should be used when needed. Since we face other factors like torque and drag, you will also need to correct your heading further than just moving both sticks in the same direction. So get to know your airplane, and don't bring it too low until you are familiar with it.

Now we get a little more complex with the harrier. Once you have mastered slowing the airplane to a harrier, going in a straight line, and then throttling up to pull out, you are going to want to do a harrier for more than just the length of the runway, so eventually you need to turn.

There is a system to the harrier turn, and it can be followed quite closely, but again, it's not fool proof.

Say you are going along in your harrier at about half throttle and you decide to turn. When first learning this, throttle up slightly and climb, then pull full up, give right or left rudder, and counteract the rudder with enough opposite aileron to keep the wings level. Upon entering your turn, gently reduce the power, and add down elevator if needed. The down elevator should not be held too long however, and will only be used to keep the nose from ballooning upward. When you've just about completed your turn, you will need to feed back in up elevator and throttle. You will probably need to apply some opposite rudder to stop the turn from spinning past your desired stopping point, and you will need to level the wings as needed.

I hope this has helped someone out there! Let me know how it works! Below is a video my my SHP. I do a lot of harriers with this plane because they are fun, easy, and it's a lot of fun to hear the rudder scraping on the ground!

3DHS Extra 300 SHP Huckin' with Doc Austin from Thomas Kitt on Vimeo.

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