Wednesday, March 12, 2008

Lessons : Rolls

Here I got Flying Lesson From, i'm sure this lesson will help you Guys.....

Lesson objectives:
1. Continue to develop fast forward flight skills.
2. Develop cyclic control to achieve consistent smooth rolls.
3. Develop collective control to achieve consistent, continuous rolls without loosing altitude.
4. Develop skills in positioning maneuvers.

Once you've got loops under your belt, it's time to try rolls! Rolls are another basic maneuver that can take time to work up the nerve to attempt, and perfect.

A roll is quite simple in concept, it's simply entering aileron control and smoothly reducing collective as the heli goes through the inverted section.

Once again, simple in concept, but not quite so simple once you come to try your first one!

Personally, it took me an age to work up the courage to try my first roll, and when I did, they all were terrible, a mix of split s's (ie half roll then diving towards the ground like a Stuka divebomber) which plays havoc on the nerves and doesn't encourage continuing to try! However, try we must and a month later I decided the little Ergo was going to roll or die trying (which is really the attitude you have to take when trying any new maneuver I reckon!) and all of a sudden it happened and I've not looked back since!

I do all my rolls in Idle Up Two which is about -9 through to +10 on the ptich. I also have Idle Up Two set for Heading Hold so that I needn't worry about the rudder as I'm rolling, makes things easier.

Once again, if you're going to roll in Normal gyro mode, be sure to have your REVOlution mixing set correctly other wise as you de-pitch, the tail may wander out of line and you'll corkscrew out.

Sort your throttle curves so that you're achieving approximately 17-1750RPM. Later on, we'll discuss getting a bit of aileron to throttle mixing action going on so that the engine keeps it's revs up through the maneuver and there is no noticable change in note.

As in just about every maneuver you'll ever do, one of the most important aspects of the maneuver is the entry so you have to make sure you enter it straight and level.

One thing that can really have an impact on the success of your roll is the attitude of the heli of entry (ie how far down the nose is pointing). If the nose is really pointing down on entry, there is a good chance the heli will start to dive as you roll, unless you give it a good dose of negative pitch as it goes inverted. Likewise, if the nose is pointing slightly up, there is a good chance the heli will 'stall' and loose a lot of forward speed or even stop in a hover. Getting the right amount of 'nose attitude' is critical to the doing a smooth roll.

Rolls are usually performed downwind and you want to give yourself a fair bit of height when you first try rolls. Even higher than your first loops. Remember, when I first tried rolls they ended up diving towards the ground pretty quick! Fly off up the field into wind climbing out to say 150-200 feet (ie plenty of mistakes high!) as you go. Begin your turn so you start flying back down range past you with the wind.

Straighten the helicopter up into level fast forward flight, you needen't be going flat out, just at a good pace. You're aiming to commence the maneuver as the helicopter passes in front of you.

Executing the maneuver
Remember, the attitude of your helicopter's nose is going to impact upon the amount of negative pitch you need to pull as the helicopter rolls over. For your first rolls, you really don't want the nose anymore than slightly nose down.

Begin the maneuver by doing a gently moving your cyclic to the right. Don't stab it, gently move it across. Make sure that you do not pull in any elevator by mistake cause that will cause the heli to dive (back cyclic) or climb (forward cyclic). A tip that I've used to ensure that I don't pull in any elevator is to completely let go of the cyclic control to let it center, then gently move it across. That way I'm minimising the possibility of adding any unwanted elevator.

Just before the helicopter passes through the 'knife edge' (ie completely on it's side), begin reducing collective. Because the heli didn't have too much of a nose down attitude when you started, you're not going to require much negative. As the helicopter becomes inverted your collective should be just below half way (say about -3 degrees or so) which should prevent the heli from 'falling out' of the maneuver.

When the helicopter passes through the inverted position and is beginning to move into the knife edge position, start moving your collective control back up again so that as the heli returns to the upright position the collective is back at full stick.

Exiting the maneuver
Ideally, the helicopter should exit the maneuver at the same altitude it entered it on. In the real world, there's a good chance it didn't, but hopefully the heli is still alive!

Don't worry though, once you've got past the first one, the rest are easy! Just keep going at them!

Things to watch out for
Entering the roll too fast.
Entering a roll too fast (ie with the nose well down) will mean you have to feed in more negative collective as the helicopter goes inverted, failure to do so will see the heli start to dive (pretty damn fast in some cases!).

Feeding in unwanted elevator.
If while your rolling you add in elevator, the helicopter will begin to dive (back elevator) or climb (up elevator), either way, it won't make the roll look very flash. One way of minimising this is to release the cyclic control just prior to rolling so that the stick center's itself first. Another way is to add a bit of negative (Futaba) or positive (JR) EXPOnential so that even if you do add a little elevator, it won't show up as badly.

Aileron to Throttle mixing.
One thing I use to ensure smooth, seemless rolls is using aileron to throttle mixing. This means that as aileron inputted, throttle is added, when the cyclic control returns to center, the throttle returns to where it was prior to the aileron input. Most transmitters have available mixing functions for this. For transmitters like the 9Z, they have built in functions specifically for this purpose without the need to take up a mix

Points to perfect
The following are a list of aspects that I look for when judging rolls.

Smooth entry (and exit) from (to) fast forward flight
A smooth start to the roll (as opposed to a aileron 'snatch').

Consistent rolling action
The roll should be smooth and consistent all the way through the 360 degree rotation.

Consistent speed
The helicopter should not alter speed during the execution of the maneuver, it shouldn't slow down, nor speed up. This requires careful management of the collective control.

Consistent altitude
The helicopter should not alter altitude during the execution of the maneuver either, again, this requires careful management of the collective control.

Get out and give it a go!

No comments: