120 SR, Blade 450, Align 450 and Phoenix.

**Vikki** · 28-01-2012 12:48 AM

I've noticed things about the above helis and how they fly in Phoenix that has me a little worried and I wonder what the proper behaviours are.

Take the 120 SR. Very touchy on the throttle when trying to hover. The slightest movement on the stick has it dropping to the ground or darting up. However, in forward flight this goes away (translational left I'm guessing). In forward flight if you centre the stick the heli comes to a hover(ish). But, the 450's don't level out, they keep their angle until you move the stick briefly in the opposite direction to come to hover. Why the difference?

The 120 SR seems to do banked turns and come out of them really easy. Centre the right stick and the 120 levels out automatically. With the 450's youseem to need to correct the bank when coming out to level up. Is this making sense?

So, which is right? Try it on Phoenix and see if you get the same results.

It's confusing me on how these things are supposed to work.

Oh, another one. 450's, give a touch of sideways drift and off they go until you correct. The 120 will correct as soon as you centre the stick.

Which is correct?

Best regards.

Vikki.

**Rich23** · 28-01-2012 08:10 AM

hey

The 120SR is fixed pitch so it almost auto hovers. imagine a marble in a bowl it will always nearly go back to the centre whenever you move the bowl. The blade and align are both CP so you have to constantly correct. Imagine the same marble but now turn the bowl upside down and put the marble on the flat bit. Now move the bowl and the marble will go any where. This is the way it was explained to me and when you act it out it makes sense.

Hope this helps explain

**AcidDrink** · 28-01-2012 08:27 AM

What you described is a difference between CP helicopter without self righting tendencies (450) and 45 degrees flybar fixed pitch trainer heli which will try to return to level when you let go of the sticks.

Bottom line is you have to correct CP heli constantly.

**Vikki** · 28-01-2012 11:45 AM

So that's why Blizzard is so easy to fly in the sim and the others aren't, thus the sim is accurate. Wow, big difference to get used to. Think I'll concentrate on CP helis in the sim before I end up with bad habits.

Thanks guys

Vikki.

**Delarado** · 28-01-2012 12:11 PM

Your 120SR and your MCPX will show you the exact same differences you are experiencing in the sim.

With the 120SR the flybar makes it want to naturally return to a level position, due to the angle of the gyroscopic effect of the flybar versus the angle of the action of gravity. The flybar will always want to be at 90 degrees to gravity, and this is translated into the helicopter (I believe!) so it will self right.

As the MCPX has no flybar it wont do this.

Anything CP With a flybar will still do this self righting but not to as much of an extent as the 120SR as they are CP and generally have a 90 degree flybar not a 45 degree one.

**Vikki** · 28-01-2012 12:30 PM

Sorry, refined my thoughts now. So, even though the stick has been centred and the cyclic has returned to level the heli still maintains its, let's say, nose down forward flight. Why doesn't gravity pull the heli body level and the rotor with it?

Just to add something I've noticed with the mCP X, if you push the stick forward a little (in sim) the nose tips down and it moves forward. Keep holding the stick forward a little and it will nosedive into the ground even if adding more throttle. Push and release the stick and you get forward motion then a stop. Talking very small stick movements here. It's almost as if you are progressively increasing forward stick movement rather than holding it forward a tiny bit. Just tried it on the sim but I'm sure Larry didn't behave like that in the field. Kind of makes it tough doing anything other than hover him in the sim.

it's like it's a hybrid of FP and CP.

These are things I've noticed and remembered over a period of time and am now putting down in words.

Just had another look with the Align 450 Sport. It likes stick forward to tip nose down and release to continue to fly forward until you counter it with backward stick. It doesn't level and stop like the mCP X does. I'm now thinking that that has something to do with the little guy being flybarless and fitted with a 3-axis gyro. Sport, continue holding stick in slightly forward position and, like the mCP X, it will nosedive. Makes sense since the body tips more and more forward and the rotor gains an acuter angle. Hmmm, so with the body tipped forward you need zero cyclic to keep the rotor at the right angle to maintain forward flight. But why doesn't the weight of the helicopter drag it all level with the ground again?

Jeepers but this hobby is weird. Maybe I'm over-thinking it but that's the way my brain works, question everything

Vikki.

**Vikki** · 28-01-2012 12:34 PM

Delarado! Yes! I remember the blurb on the adverts for 120 SR saying something about the 45 degree flybar adding to the stability. I'd forgotten that. So 90 degree doesn't act so aggressively on the rotor?

I'm starting to get to grips with it all now.

Vikki.

**Sharpedge** · 28-01-2012 12:45 PM

Vikki,

You are getting into the realms of aerodynamics now, when you move the cyclic (elevator) forward it tips the disc forward which in turn imparts forward flight. As you rightly say it also causes the heli to lose altitude, to counter act this you apply collective via the left stick. This changes the angle of the blades to create lift. When you bring the cyclic back to centre the disc stops tipping therefore the heli will not tip any further forward. As the angle on blades has been changed to create lift in forward motion they are in effect pulling the heli forward. With the centre of gravity directly under the disk the heli should not fall back to horizontal. If the heli is not balanced correctly it will continue to tip forward if nose heavy or back if tail heavy.

**anti** · 28-01-2012 12:54 PM

I believe the MCPX works on a "heading hold" gyro, meaning that if you push the nose forward, the gyro holds that nose forward until you tell it to do something else.

http://www.rchelicopterfun.com/heading-hold-gyro.html

**Vikki** · 28-01-2012 01:35 PM

Thanks guys.

Anti, might be worth looking at this. mCP X fbl system. Interestingly, at around 0:51 seconds something seems to make a crack sound and a servo arm jumps. Oh dear!

http://m.youtube.com/index?desktop_u...?v=5OOMw9XxisU

An interesting experiment

Best regards.

Vikki.

**Delarado** · 28-01-2012 01:44 PM

Short response as I'm in the car - but vikki; with the mcpx to fly forward you'd nose forward a bit with the cyclic and then let that stick centre.

The help will tip forward creating forward flight and will more or less retain the tip angle youve given it until you tip it back, creating constant forward flight.

The rotors do have a slight gyroscopic effect making the help return to level but it happens very slowly as the blades have very little mass and the gyro is designed to counter this effect as mentioned.

The mcpx in Phoenix is wrong. I've modified mine and it flys more like an actual mcpx now but still not the same.

I'll give you settings later but I think the main one was 50% vortex lift loss and changing to passive flybarles from active

One you get to grips with forward flight with larry you'll See the inaccuracies of Phoenix in that regard.