Loops...

[websitedragon]

Do you guys dive a bit before going in to a loop, or just go at it straight and level?

I'm trying to summon the guts to try it again. Last time I made a complete mess of it, which resulted in an upright heli attacking the ground with full neg pitch :o .

[TachyonDriver]

Having forward airspeed is a good idea - diving may give you a bit more speed, but don't go too low! Also it helps if you have a heli with plenty of power ;)

My Rappy is currently being repaired because I tried a loop :(

[websitedragon]

Yeh, I think I can do it however I'm enjoying having a small repair bill, so makes me a bit more nervous.

The time will come soon though. Flips are going to be my weak point me thinks.

[mnuetzmann]

When you do a basic loop you do not give it negative pitch. Just like a plane you go into it with forward momentum; otherwise it's a flip ;)

To get a nice smooth loop enter the loop with enough forward momentum to get you to the top of the loop gradually giving up on the right stick as you pass the top you begin to pull pitch but do not go negative. If you go negative in pitch you loose the smoothness of the loop and start "pushing" the heli out of position. You are using the natural energy that is already there to perform most of this maneuver. Once you pass the 3/4 point of the loop you are adding pitch back in and by the end of the loop you should be back to your original stick positions.

Mark.

[Gadget01]

If loops make you nervous, this might help-

It might give you better peace of mind if you know how well your heli will handle inverted flight. Make sure your heli is mechanically set up right and you have enough negative pitch in your idle-up curve. Ideally, your pitch curve should be linear and half-stick should be 0 degrees pitch.

Take it up really high and bring it to a level hover. Pull back on the cyclic about half-way (not too hard or you demand a lot more power). As it tilt-angle approaches 90 degrees, pull back the left stick to half (so your blade pitch is neutral) and keep it here until the heli rotates through inverted and back again. Your heli WILL lose some altitude as you complete this move, but it should not "motor" itself to the ground like it would if you keep positive pitch the whole time. Also, this should not demand too much of the power system, so if it's not a hotrod setup, it's not a big deal since it won't bog down and make your control sloppy.

Try it as high as you can still see the orientation at first, then bring it down as you get comfortable. You can then give it negative pitch as it rotates to inverted and then keep it from losing any altitude at all. From there, you can pause here and hold the inverted hover- even for a brief second, then keep going. The next time, go to inverted, then go back forwards to recover.

This is how I eased myself into flying inverted and I was really chicken to try it for the longest time.

[websitedragon]

I'll give that a try :) cheers.

I programmed my DX7 so in idle up mode I had zero pitch at midstick and it went to positive with the stick fully up or fully down. This has helped a lot getting used to flipping between the two stick positions. In fact I think it helped too much: On my first attempt I leaned the heli backwards but applied neg pitch too quickly, before it had turned over - woops.

[aragon]

You should probably be perfecting 90 degree stall turns first...

[vpersiani]

For me loops are stall turn where I keep cyclic in and ease on pitch at the top of the loop.
I did not do that many loops so far, but experienced strange things once: coming out of the loop the heli went piroueting for one or two complete turns and then the gyro came back in...

[hurleybt]

loops scare me... flips are easy :)

[InsomniaZZZ]

I did my first loop last Saturday - Wohoo!

It was the last minute on the last battery for the day, and I decided to go for it. Heli was about 30 meters high, about 40 meters in front of me. I took it back a little, then switched to forward flight (medium fast). I only pulled back elevator (all the way) and kept it there (I think I also stopped breathing and my heart flatlined as well). The loop started nice, but the backside ate up almost all altitude. I didn't move throttle/pitch at all, next time I'll have to do that. Came out of the loop at 2 meters over ground.

Good luck to anyone starting off with loops - it's exhilarating!

[StarmanDXE]

You should probably be perfecting 90 degree stall turns first...Can you explain what this is exactly?



I did my first loop last Saturday - Wohoo!

It was the last minute on the last battery for the day, and I decided to go for it. Heli was about 30 meters high, about 40 meters in front of me. I took it back a little, then switched to forward flight (medium fast). I only pulled back elevator (all the way) and kept it there (I think I also stopped breathing and my heart flatlined as well). The loop started nice, but the backside ate up almost all altitude. I didn't move throttle/pitch at all, next time I'll have to do that. Came out of the loop at 2 meters over ground.

Good luck to anyone starting off with loops - it's exhilarating!30 meters high! I like to keep mine closer to 3... :rolleyes:

[P-38J-Lightning]

Can you explain what this is exactly?

Fly straight and pull STRAIGHT up, then at the top when you stop flip the tail up go down and pull out.

Joel :D

[websitedragon]

Fly straight and pull STRAIGHT up, then at the top when you stop flip the tail up go down and pull out.

Joel :DThat would be a 180degree stall turn...

[P-38J-Lightning]

That would be a 180degree stall turn...
Whoops, my bad. I went by the angle of ascent. :o

I take it for a 90 you come in at an angle and then go out at an angle.

Joel :D

[StarmanDXE]

Fly straight and pull STRAIGHT up, then at the top when you stop flip the tail up go down and pull out.

Joel :DThat was my guess. I would have been wrong, too :rolleyes:

So, how do you go in and come out for a 90 deg? Does it matter? :confused:

[tankrust]

I am getting ready to start some forays into inverted flight with my brushless HB CP2. I have been doing FFF figure 8's, stall turns, etc. I only have one question... I am running a G90 heading hold gyro, and when I go inverted, will the gyro make the tail whip around 180 degrees? If it is truly "heading hold", then it seems like the gyro will make the tail turn 180 when the heli goes inverted. Do I need to set up my idle up so the gyro runs in rate mode for inverted flight? Just don't want any surprises on my first attempt.

[websitedragon]

That was my guess. I would have been wrong, too :rolleyes:

So, how do you go in and come out for a 90 deg? Does it matter? :confused:I'm thinking you pull up in to a stall. Give it rudder so it turns 90degrees (and is falling back down sideways) then roll it so its level and power out.
That should be quite a cool move.

[StarmanDXE]

I only have one question... I am running a G90 heading hold gyro, and when I go inverted, will the gyro make the tail whip around 180 degrees?He he. :D No. The gyro can only sense rotation around the main-shaft axis. It will have no idea that you're doing a flip.



I'm thinking you pull up in to a stall. Give it rudder so it turns 90degrees (and is falling back down sideways) then roll it so its level and power out.
That should be quite a cool move.Personally, I think the 180 would be cooler :rolleyes: ;)

[Gino CP]

Hover in idle up. Do a pitch pump (rapid up and down). If tail holds it will hold in a flip. To avoid surprises, you know how to hover in all orientations. You must also know how to fly very high. 12 meters is not enough. Perhaps double or more. When doing a loop, make sure to level off your collective when inverted. Otherwise it will be a very huge loop that exits much lower then when you entered it. Lastly, do the loops and inverted after several flights. This way your field day is not ruined totally in case you don't make it.

[StarmanDXE]

I was doing some pitch pumps on mine the other day, and it wouldn't hold :( Any suggestions? Is it just a matter of turning up the gyro sensitivity?

[P-38J-Lightning]

I was doing some pitch pumps on mine the other day, and it wouldn't hold :( Any suggestions? Is it just a matter of turning up the gyro sensitivity?
Turn it up till it wags, then turn it down.

What tail servo are you running? IIRC it was a 9650 with a 401. Make sure your Delay is set to 0!

Check for slop in the tail etc or if you are using an eccesivaly long servo arm replace it.

Joel :D

[StarmanDXE]

Yes, S9650 and a GY401. Delay should be at zero... :rolleyes:

Also, what do you define as "excessively long" for a tail servo arm? And what does it matter? Do you think it will bow out or something if it needs to move quickly??? :confused:


I'll try that wag method and see if that works. Don't think there's any slop anywhere, but I'll check.

[P-38J-Lightning]

Excessivally long makes it has less steps per movement. Also, the Gyro gain goes lower for the longer the arm is.

Joel :D

[StarmanDXE]

Oh. You're talking about the arm that is screwed onto the gyro itself? Well, I have a disk on there. That's how it came. And why would it matter? It's digital! :eek:

[InsomniaZZZ]

Oh. You're talking about the arm that is screwed onto the gyro itself? Well, I have a disk on there. That's how it came. And why would it matter?

It doesn't matter if it is a physical arm or a disk. What matters is the distance between the center of rotation (typically, the center of the screw that attaches the arm/disk) and the center of the ball link that connects to the rod. This distance is the "lever" or more commonly the "arm".

Servo power is given in torque (http://en.wikipedia.org/wiki/Torque). It is related to the force exercised at a given lever distance like this:

T = r x F

This formula uses the cross product and gives you correct vectors. If you're only interested in the absolute amount of torque / force, you can use regular multiplication:

T = r * F

Hence,

F = T / r

Now imagine the torque is constant (like, for example the output of a servo). If "r" is increased, you divide by a bigger number, hence "F" will decrease on the other side of the equation. If "r" is decreased, then "F" will be increased.

So the shorter the "arm", the more power you will have at your disposal to control the tail rotors.

It's digital! :eek:

Hehe - good one ;-))

[InsomniaZZZ]

..Also, the Gyro gain goes lower for the longer the arm is...

Whenever you change the arm, you need to redial the gain. It should be set so that the tail mechanics move from end to end when you use your rudder fully left/right (I'd try this with the main motor disconnected and on a workbench). You should hear that same slight binding in your servo in each direction - then turn the gain down a hair, so that the binding is gone on each side.

For a GY401, you should try to have a gain at or slightly above 100% (like 110% or 120%). You have to physically move the ball link on your arm/disk and re-adjust gain after each surgery. As PJL says: if your gain is at 150%, move the ball link closer to the center screw. If you gain is at 40%, move it away from the center servo screw.

[StarmanDXE]

Hey, I'm a mechanical engineering student. I think I've got a pretty firm grasp on the whole "torque" thing :p But, I did have to think about it for a second to understand why a shorter arm would be better :rolleyes: So, thanks :)

But, in all honesty, I don't think that the force from the pitch of the tail rotors is anywhere near the 4.5 kg that the S9650 can push at 1 cm! :eek:

[InsomniaZZZ]

Hey StarmanDXE

Sorry, I didn't mean to lecture you. I must have read something into your response that made me go into explanation mode. I hope some other readers will have learned something (as I did a lot when I started reading these forums).

I think the point of having such high-torque servos is that they easily overcome any friction - be it internal to the servo, or part of the tail mechanism - and move that darn thing as fast as possible to the ordered location. I agree that the tail pitch forces cannot possibly be at these values (considering that the lever at the tail rotors itself is just the ball-link distance from the center of the arm - about 10mm on a 400 class heli?).

Who can elaborate on this?

[StarmanDXE]

Oh, no, it's cool. You definitely got me thinking ;) And I'm sure it will help someone out. Also, good point about how that should make it faster.

Yeah, I think I'm just going to try turning up the sensitivity and see if that does the trick :)

[clicky]

Oh, please do continue in your "explanatory" mode :)

Anyway let me try something else:

Shorter the arm is quicker the servo must be. Isn't that true? Now where is the optimum? Is it defined by position of gain as you have explained?

[StarmanDXE]

Shorter the arm is quicker the servo must be. Isn't that true?Ooo, good point. Geeze :rolleyes:

[Kai_Shiden]

Whenever you change the arm, you need to redial the gain. It should be set so that the tail mechanics move from end to end when you use your rudder fully left/right (I'd try this with the main motor disconnected and on a workbench). You should hear that same slight binding in your servo in each direction - then turn the gain down a hair, so that the binding is gone on each side.

For a GY401, you should try to have a gain at or slightly above 100% (like 110% or 120%). You have to physically move the ball link on your arm/disk and re-adjust gain after each surgery. As PJL says: if your gain is at 150%, move the ball link closer to the center screw. If you gain is at 40%, move it away from the center servo screw.Yikes, while you are correct that servo arm length affects max gyro gain.... You're way off base about the binding... the GY401 has a travel adjust dial on it, you use that to make sure that the servo doesn't overtravel and bind.

The tail needs speed, not torque to respond to fast response demands, that's why a 0.6sec/60deg transit is preferrable to 1.0sec/60deg transit. The only torque that is needed is dependent upon the friction and geometry of the tail for a given heli (in an ideal world, the tail blades would be properly weighted so that they would react neutrally to input angle, but really the blades pitch rotation axis typically is leading the center of lift, so some torque is needed, just not nearly as much as many people think.

You can split up the tail system into electronic gain (gyro settings), and mechanical gain. Increasing the servo arm length increases mechanical gain, so a corresponding drop in electronic gain will be required (electronic + mechanical = output). I personally run quite long servo arms on the tails of my helis because it improves response speed (but at the same time, I also run servos that are rated for over 2x the torque needed), what I lose is resolution, but pick up response speed and more linear tail action (if you're running past 100% travel adjustment on a GY401 with a short servo arm, you're actually just wasting time at the ends because of the arc the servo arm travels in towards the ends)

-Kai

[InsomniaZZZ]

Yikes, while you are correct that servo arm length affects max gyro gain.... You're way off base about the binding... the GY401 has a travel adjust dial on it, you use that to make sure that the servo doesn't overtravel and bind.

You are absolutely correct - I should have used the proper term: "Limit" is what is written on the GY401 and it's the right, tiny potentiometer on the unit (next to "Delay"). I was thinking "Limit", but calling it "Gain" in my post... "Gain" is what is set through the 2nd plug in the receiver. Sorry for any confusion.

[turnbui]

Fascinating reading, the last 3 to 4 replies of this thread. Please continue with this type of answer - I'm being sucked into this incredible world. Thanks guys.
Now how about someone putting together a sticky explaining the right way to do some basic 3D manoevers please. My Heli cost me all I can spare, ie. I can't afford coaching at $6x per hour even though it'd save me tons of money in repairs.
Any takers for the sticky??

[clicky]

Not that it matters to this thread, but I did my first loop today! :)

Also, how is it called when loop is not really a loop (when someone panics and moves throttle stick much, much more to negative pitch a the top of the loop)?
(I did that too as well... LOL :) )

[StarmanDXE]

That's a flip :p

So, how was it? I'm still too nervous :rolleyes:

[clicky]

That's a flip :p

So, how was it? I'm still too nervous :rolleyes:

Hm... After first try (read: a flip) I had to land. I found out that my thumbs were shaking! Not only thumbs, hands too. And legs! LOL

Then I wanted to make a pause taking a quick walk but plan failed and I stayed on the field and got into the air in next 3-4 minutes. Did it two more times and had to land again (similar reasons).

I am normally flying 5 minutes + pause + 5 (or whatever battery allows) in normal mode or 5 minutes in Idle up + pause + whatever battery allows in normal mode. That time it was 2 mins in idle up, pause, 1.5 minutes in idle up, pause 3 minutes of which 2 in idle up + 1 minute in normal. After that I didn't push battery anymore and got another. LOL

Coffee I had 30 minutes before getting to the field didn't help at all! I was shaking like...

Huh... It felt great! :D

BTW I found out that I am ready when I started pushing it further - flying faster and further away and higher. But nothing really happened until 3rd battery - when I flipped a switch to Idle Up. Buzz the heli made - made me do it! Heli become more responsive (I had trouble keeping the altitude due to adrenalin surge) and I just couldn't refrain myself trying for it! O: )

[heliboy88]

What i did the first time i tried loops was i first got some forward speed, then gave a little more throttle(collective) before pulling the elevator stick, and when the heli got vertical(pulled the collective to mid stick during vertical), i simply push back the elevator stick and put the heli back into basic tail in hover. Then after a few tries and i felt comfortable with it, i just did the same as the above, but this time, i didn't back the elevator stick and just let the heli continued to go inverted(i gave some neg. pitch here), and continued until the loop was done(of course don't forget the collective stick during the transition from inverted to vertical and right side up). And at that time i really started to shake like others said, but i didn't stop(maybe that's stupid) and looped the heli 2 more times before landing. And that was the last and 5th pack of my happy day :) .
Btw, i did that after my first crash(just main blades damaged) of the heli at my 3rd pack of the day. I was more willing to try the stunt after the crash maybe just cus the heli was not 'brand new' already. :D

[Art Newland]

I've managed my first loops over the last few days. I'm flying a fairly low powered Logo 10 (about 400 watts). I'm sure it would be a lot easier with more power. The first one I tried, I first got some altitude, I tried to do it big and round like with a fixed wing. Looked great at the start to inverted, so I went to neutral collective so it wouldn't pull the heli down too fast, pulled more cyclic and it came right around, but fell quite a ways as I added collective back in. It took a few minutes for the heart rate to settle back to normal, but I had completed it successfully. I have a lot better looking loop if I just run into it with a lot of forward speed and just pull back about 3/4 stick on the cyclic and let it whip around in a fairly tight fashion. Blades make a lot of cool noises. :D I'm trying some rolls now, not having much luck however, at least I'm getting it back under control after a boched try.

[clicky]

Now I have a problem keeping it leveled - not banked to a side - before going into a loop. Couple of times I went into for a loop in font of me (to he right) ended up behind me O: ) as helicopter was slightly banked to the right (to myself). LOL

[StarmanDXE]

Geeze. I've gotta try a loop sometime soon and just get over the fear :p

What do you guys think is the easiest "3D" maneuver? This?

[InsomniaZZZ]

I did many loops yesterday, first with the Trex450, then with the Trex600. There is quite a difference between the two: the 450 loops faster and is more likely to end up banked. The 600 is more docile, reacts more like "it should". Pitch curves, expo etc. are set up very similar between the two models. I guess the heavier mass of the 600 forgives my insecure and jerky inputs. Of course, either one does some serious pumping sound coming out of the loop; finally I let the motors do some heavy lifting... (I love that sound!)

While we're on topic of flying at the field: Why is it that I never read about not flying directly towards the sun? Is it so common sense that nobody ever mentions it? :confused: Anyway - if you're a beginner like me: do NOT fly towards the sun. Have it behind you, have it sideways behind you. In terms of visibility, the sun ALWAYS wins over any aircraft! :cool:

[StarmanDXE]

Why is it that I never read about not flying directly towards the sun? Is it so common sense that nobody ever mentions it? I think you hit the nail on the head :cool: ;)

[Art Newland]

If you mistakenly fly into the sun, close one eye, then open it after you pass the sun. You'll be blinded in the one eye for a bit but still able to track your aircraft with the other.

[StarmanDXE]

Huh. Good idea!