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HelicopterBeginners Corner › How to do a perfect autorotation?
03-21-2009 05:48 PM  8 years agoPost 1
Ragz

rrApprentice

India

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So how do you pros do autos? Flick the switch and pull full negative until its 3 feet from the ground? Whats the right way of doing autos. Today I was able to auto from say 50-80 feet. However, it seemed that I was flaring a bit too soon... All the landings were very soft, but the decents werent pretty...Inputs would really help me learn the right method in the early stages of the learning curve.

thanks

Anurag

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03-21-2009 06:14 PM  8 years agoPost 2
trunkmunki

rrApprentice

Bangor

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I am in no way a pro, but depending on the collective pitch range you are running in your hold-mode, you do not need (or want) full negative pitch. You will end up with excessive head speed and rate of descent. If your touchdown was okay, you must not be doing anything too wrong, what specifically was wrong with the descents? The only things I could see having wrong with the gravity-driven part is rate or not enough (or even too much) forward speed. The rate part is going to be due to too-high or too-low of a head speed, or too fast or too slow forward speed. If you have any energy left for cushion at the bottom, your head speed is not too low. You should have to do some kind of decellerative flare at the bottom before you pull any collective, if you don't I am guessing you don't have enough forward speed.

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03-21-2009 07:38 PM  8 years agoPost 3
BEAR

rrApprentice

Peterborough

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Any time you can take off and fly again after an auto is ok by me kin hell i,ve had to get the bus to go and pick my heli up some times but if its in 1 bit the hell thats a bonus

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03-21-2009 07:59 PM  8 years agoPost 4
BarracudaHockey

rrMaster

Jacksonville FL

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Actually, even if you run -11 you'll just drop like a rock without any benefit in head speed.

Andy
AMA 77227
http://www.jaxrc.com

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03-21-2009 09:40 PM  8 years agoPost 5
rexxigpilot

rrProfessor

Florida

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Yes. Without any wind, a straight downward descent will have your heli flying in a vortex ring - a circular flowing ring around the blade that is downward on the inside. This will make the heli drop like a rock and oscillate about the center of descent. A controlled descent usually takes a slight bit of forward, backward or sideways motion.

One way of learning autos is the reduced throttle hold method. Start by setting the t-hold at just under hover throttle. Practice autos while slowly lowering the t-hold throttle each time until it is at idle setting. This will give the beginner a bit of confidence that he won't stall the blades 10 feet high on that first auto.

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03-21-2009 11:02 PM  8 years agoPost 6
gftazz

rrVeteran

upstate N.Y. in the​Adirondacks

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I learned in stages. After learning to hover I would flick the switch while at around head height and let the heli float down and then add the pitch to control the descent and touchdown. The I would get it up high and I purpously set my Throttle hold low pitch to around -4 or -5 when the stick was all the way down then I would flip the switch way up high tail in at first and pull the throttle all the way down and watch the descent and played with raising the nose of the heli till I heard an nice VRRRRRRRRRRRRRRRRRRRRRRRR type sound without too fast but a controled nice descent then I would add in pitch to slow down heli and flare slightly at around 10-15 feet height then flip out of hold while in normal mode and fly back up and practice till one day the notor quit from the plug or running out of fuel as we didn't use header tanks back then and I was forced to connect the low and high portions I had been practicing and it was a non event my first full auto.

Start to add in some pitch at around 10 feet up and add it in easily sometimes I will pump the stick like a pop to stop or put the brakes on quicker then I will either slowly add in pitch till it settles and float it till it lands from no more lift. Sometimes I will pump the stick to keep it up as long as possiable at the bottom till you have to land from no lift.

As you get better then change the low pitch in throttle hold to the straight line like in the other modes 11-11 12-12 etc and use what you need for whatever speed in coming down you want to acheive.

Oh No Someone Please Stop Me Before I Go Broke With This Heli Thing!!

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03-21-2009 11:10 PM  8 years agoPost 7
FlaG8r

rrElite Veteran

Florida

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my only tip would be when you start practicing them from above say 10 feet, and using some forward speed...do a quarter piro to bring the tail back around facing you. It can be a chore to flare properly and not ding the tail while keeping the heli parallel to you at first.

Life is tough, it's tougher if you're stupid

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03-22-2009 01:15 AM  8 years agoPost 8
ZAC ATTACK

rrKey Veteran

Hamilton Ontario,​CANADA

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It takes a while to learn Autos but I recommend a beginer learn Autos before advancing to 3D!If you can Auto your heli,you can save lots of $$$ in crash prevention.

MAAC#77677 Medicated daily for your protection

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03-22-2009 01:44 AM  8 years agoPost 9
rotormonkey

rrKey Veteran

Ottawa, ON - Canada

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I suppose it depends on who you ask. There's a guy at our field that gives a bunch of negative, brings the nose down, and watches it drop like a rock, then levels out, and flares at the bottom. Most guys keep it pretty level the whole way down with just a little negative.

Keeping the helis speed up gives you more headspeed when you flare at the bottom it seems - when he does it he's got LOADS of headspeed and can actually just float the heli all the way down the runway and back to his feet. Requires good timing and collective management though. I can't do it like that.

I'm one of the guys that just keeps it level and floats it down. imho, it's a lot easier that way. I've tried his way a couple times, but it comes in like a rocket every time and I find I have a hard time getting the flare right without burning off all my headspeed.

Some guys flare at about 10 feet up, and come straight down from there. Some guys flare at about a foot. Others just slide it in on the skids with forward movement.

The only way to learn is by doing it. As you do it you'll get a feel for how the heli will react as you bleed off headspeed. The more you get the feel, the more comfortable doing it you'll be. The more comfortable you are, the more you can experiment. As you experiment you'll gradually learn how to get it nice and smooth, and drive it in just the way you want it.

Good luck

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03-22-2009 03:58 AM  8 years agoPost 10
TheWoodCrafter

rrKey Veteran

Costa Mesa, Ca.

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I'm just learning autos too.
So set the pitch curve in throttle hold to -6 at the bottom and that is enough negative?
That will build enough head speed for a good flare and not let the machine drop like a rock?

Is it possible to cork screw down using cyclic if it looks like you are going to over shoot where you want to land?

Sorry to steal the thread.

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03-22-2009 04:15 AM  8 years agoPost 11
Justin Stuart (RIP)

rrMaster

Plano, Texas

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So then is it better to practice autos from 10 feet up, or 30 feet up?

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03-22-2009 04:18 AM  8 years agoPost 12
TheWoodCrafter

rrKey Veteran

Costa Mesa, Ca.

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Good question jrock.
I've been practicing from about 100 feet up.

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03-22-2009 05:16 AM  8 years agoPost 13
shuttlepilot

rrElite Veteran

Mullins, South​Carolina

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I started practicing them from the "ground up" when I was flying a shuttle 30.....years ago. I read it in some mag back then. I would take it up a couple of feet and hit hold, then increase it a little more the next time. The only problem with this method is that you need to have some wind to point it in to or you will get in the vortex and the heli could drop quite hard. After about 10 feet up, you need to have some forward speed. It doesn't take a great deal of negative pitch to do a decent auto. You can actually do one pretty good with -3 degrees, but I have mine at about -9 at full down collective, but I don't drop my stick all the way down when performing one.....only use what I need to keep the headspeed up. Start my flare as it comes under 10 feet to stop forward speed and then collective I guss at about 3 feet and let it settle, maybe slide a little.
One thing to remember is don't hold aft cyclic on touchdown. I cut off one boom and dinged a couple of others while practicing. Must remember that the blades are still coming down even if the boom isn't.

I also did and do a lot of "powered" descents, or fast descents with quick stops at the bottom. This just gets you used to the heli coming down fast and teaches how to flare to stop forward motion without doing the actual landing.

I did a lot of this without doing an actual "full auto"...I just couldn't build the nerve. Then one day..flame out!! I was probably 75 feet or so up and all of the sudden silence. All of the stuff that I had practiced just came into play automatically and the auto went off just as it was supposed to. I actually added a bit too much collective at the end and the heli balooned a little, but I still had enough land softly. After that, I had confidence to do them on purpose...lol
Sorry so long, just wanted to cover the bases I went through.

Gas is Great
Camper Fuel is Better!!
QWW Helis

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03-22-2009 05:22 AM  8 years agoPost 14
Santiago P

rrProfessor

South West, Ohio

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My advice it to learn a bit about the aerodynamics involved in an auto. When you do, it gives you a better picture of how to ride the collective on the way down.

There are three parts to an auto, the decent, the flair, and the touch down. BTW, always do then into the wind, and always keep a bit of forward speed while you do them. Never go straight down!

Let me try to explain it simply (I suck at simple)

When you auto the rotor is being driven by the air that is going across it. The term is sometimes called windmilling. When you have the "right" angle on the blades, the outer part of the rotor is making lift and inside part is driving the rotor.

(The pic is from http://www.copters.com/helo_aero.html#concepts)

At the same time, the drag component of the blades is also pointed upwards in relation to the helicopter creating lift. When these forces balanced out the helicopter has a steady state decent meaning it falls at a steady speed. It also means that the rotor is keeping a steady RPM!

Here is a cool thing, when the heli is on that condition, it makes a very distinct sound, too much negative and the heli falls like a rock, too little and the rotor will slow down, just right and you will listen a steady rumble caused by the windmilling.

Down to the last 10 to 15 feet, now is time to convert your forward speed into MORE lift. Start pulling back on the cyclic while holding the same amount of negative pitch you had all along. If you do it right the flair WILL stop the helis decent almost completely, and your rotor will even speed up a bit more.

So now you are 2 feet off the ground basically hovering with no engine, and probably still leaning back from the flair. The rest is to smoothly push forward to level the heli and apply the rest of your collective to settle down on the ground. If you are swinging 700mm heavy blades you could drink a cup of coffee while it settles down. If you are swinging very light 500mm blades, you will feed the collective quickly as the same time that you level off.

Autos in heavy wind are easier as the wind gives you more lift.

I teach autos by first doing then in normal mode with the engine idling. That way you can practice the decent and flair, which are the two most important parts of the auto, if something happens, you just advanced the throttle SLOWLY and bail out.
Good Luck

Santiago

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03-22-2009 05:43 AM  8 years agoPost 15
TheWoodCrafter

rrKey Veteran

Costa Mesa, Ca.

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Thanks guys, that is really helpful.
I didn't know forward movement was that important.

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03-22-2009 06:00 AM  8 years agoPost 16
shuttlepilot

rrElite Veteran

Mullins, South​Carolina

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Yes forward motion, or always working into the wind keeps the rotordisk in "clean air" You can experience "dirty air" when you try to do a descent straight down from a higher than hover altitude. Comparable to an airplane experiencing wind shear resulting in a loss of lift. Of course you can put a much more technical wording to this....but same result....

Gas is Great
Camper Fuel is Better!!
QWW Helis

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03-22-2009 07:26 AM  8 years agoPost 17
Ragz

rrApprentice

India

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This is great info. I didnt realize the importance of head wind and/or forward motion up until now. Yesterday's autos (my first ones) we performed with a vertical climb out and straight down...vertically... they turned out pretty nice and soft...now I realize there was plenty of head wind. My only issue with them was the balooning...so its basically the timing of the collective input thats important. Cant wait to try out forward motion autos...

Anurag

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03-22-2009 02:08 PM  8 years agoPost 18
BarracudaHockey

rrMaster

Jacksonville FL

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Ideal pitch is somewhere between -3 and -5 for most machines. When you hear it you'll know you're there because it makes a distinct sound, just like an autogyro when the blades have enough RPM to take off.

It has to do with the weight of the heli, and the blades (chord, airfoil, weight)

Andy
AMA 77227
http://www.jaxrc.com

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03-22-2009 04:14 PM  8 years agoPost 19
Justin Stuart (RIP)

rrMaster

Plano, Texas

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I'm curous about this "sound" you guys are referring to. Anyone have a good video they can post (or link to) which will illustrate this?

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03-22-2009 04:25 PM  8 years agoPost 20
shuttlepilot

rrElite Veteran

Mullins, South​Carolina

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Like barracuda said. You'll know it when you hear it. It's a popping sound. I bet someone on here will have a vid of one out there somewhere.

When I was training in full scale helis, it was one of the sounds that you would be listening for when making a descent at the right angle and speed.

Gas is Great
Camper Fuel is Better!!
QWW Helis

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