RunRyder RC
 13  Topic Subscribe
WATCH
 3 pages [ <<    <     1     ( 2 )     3     NEXT    >> ] 3298 views
Scorpion Power Scorpion Power
HelicopterBeginners Corner › How to do a perfect autorotation?
03-22-2009 05:09 PM  8 years agoPost 21
Santiago P

rrProfessor

South West, Ohio

My Posts: All  Forum  Topic

"Cant wait to try out forward motion autos..."

To add, the ideal angle for your glide slope (or auto slope) on a no wind day is about 45 degrees plus or minus a few. The wind will cut the angle down giving you an apparent stepper slope. This is the descent angle, not the blade angle. As everyone said, listen for the popping-rumbling-humming sound.

On full size helis there is something called a dead man's curve, which pretty much says if you auto too steep or too shallow, you are dead. I also refers to heigh and/or speed minimuns to accomplish an auto.

http://en.wikipedia.org/wiki/Height-velocity_diagram

Bet cha shuttlepilot has some good stories on that. Luckily model helicopter can get away with a few more degrees off, but the same principle applies.

For anyone learning, check out this website:
http://www.copters.com/helo_aero.html#concepts autorotation is the bottom one, but dont just go for desert, read along.
The more you understand the flight principles, the more you understand your small heli.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
03-22-2009 05:37 PM  8 years agoPost 22
Justin Stuart (RIP)

rrMaster

Plano, Texas

My Posts: All  Forum  Topic

On full size helis there is something called a dead man's curve
I thought that "Dead man's curve" in a full-scale heli was something like being less than 50 feet up with no forward airspeed?

But looking at the height-velocity diagram for the Bell 204B you linked to, it seems that you need to be either 600 feet AGL with 0 knots forward airspeed, or 100 feet AGL with 50 knots forward airspeed to be safe.

Is this why full-scale helis never take off straight up (like I always do in my Trex)?

So then what do these parameters translate to for a 50-90 sized heli? 30 feet AGL with 10 knots forward airspeed? How about for a 450 sized heli?

Avant RC
Scorpion Power Systems
Thunder Power RC
Kontronik Drives

PM  EMAIL  GALLERY  Attn:RR  Quote
03-22-2009 06:52 PM  8 years agoPost 23
BarracudaHockey

rrMaster

Jacksonville FL

My Posts: All  Forum  Topic

Full scale helis dont have neg pitch, run a helluva lot lower head speed, you really can't translate the numbers well.

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

PM  EMAIL  GALLERY  Attn:RR  Quote
03-22-2009 07:30 PM  8 years agoPost 24
Santiago P

rrProfessor

South West, Ohio

My Posts: All  Forum  Topic

So then what do these parameters translate to for a 50-90 sized heli? 30 feet AGL with 10 knots forward airspeed? How about for a 450 sized heli?
no no nooo, I am not saying the same speed, rate of descent, blade angle of attack, or other numbers from full scale apply, in fact they are diferent for all helis. The principles and the glide slope angles apply.
BTW 10 to 15 knots forward airspeed is a good number for our models. 450s dont have enough inertia to do "easy" autos, unless you are really, really ridiculously lol good.
Thanks for bringing it up!
Is this why full-scale helis never take off straight up
Yep

off to the field...

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
03-22-2009 07:39 PM  8 years agoPost 25
Justin Stuart (RIP)

rrMaster

Plano, Texas

My Posts: All  Forum  Topic

Full scale helis dont have neg pitch,
To clarify: For a full scale heli autorotation, the pilot lowers the collective down to neutral pitch while keeping the cyclic slightly forward? Then at the last second the pilot flares the heli by pulling back on the cyclic while simultaneously pulling up on the collective? Is this correct?

It seems then that with a RC heli, you wouldn't want to give too much negative pitch--and might even want to just give just slightly less than neutral pitch to impart maximum RPMs to the blades while at the same time slowing the rate of descent as much as possible?

Why then do people advocate negative 4 degrees pitch? Is it because the smaller diameter rotor blades on model helis have less kinetic energy than their full size counterparts, and so more negative pitch is required to get sufficient head speed? If I tried an auto at only 1 degree negative pitch, would my blades stop spinning?

Do smaller helis (or helis with lighter blades) need more negative pitch while larger helis can get away with using less negative pitch and therefore enjoying a slower rate of descent?

Avant RC
Scorpion Power Systems
Thunder Power RC
Kontronik Drives

PM  EMAIL  GALLERY  Attn:RR  Quote
03-22-2009 07:42 PM  8 years agoPost 26
trunkmunki

rrApprentice

Bangor

My Posts: All  Forum  Topic

You need to be using SOME power to be in "vortex ring state," so if you are autorotating, you can not be in VRS. This is a MUST for VRS to be encountered.

PM  EMAIL  Attn:RR  Quote
03-22-2009 07:48 PM  8 years agoPost 27
Eagle2bravo

rrVeteran

Out flying somewhere

My Posts: All  Forum  Topic

I'm no pro but what I do is, flip throttle hold and just hold collective at or a hair below mid stick depending on how high you are. You say around 80 to 100 ft. you don't need much neg. pitch. Of course this also depends alot on your choice of blades. With the G5's I hold right at mid stick all the way down from around 150 ft. or so. From way high up I find myself feeding in more neg. pitch. Hope this helps.

T-rex 600n super pro , Trex 450 se, Gaui 200, Trex 500, Blade cx, . "If ya plant corn, ya get c

PM  EMAIL  GALLERY  Attn:RR  Quote
03-22-2009 09:13 PM  8 years agoPost 28
BarracudaHockey

rrMaster

Jacksonville FL

My Posts: All  Forum  Topic

Lighter blades need some pitch, they don't have the inertia of the full scale.

Actually full scale blades have some wash out built in at the tips so while the collective is at 0 or flat pitch, there is actually a bit of negative pitch at the tips helping.

He's right, no vortex ring state, and no dirty air in an auto, clean air is coming up through the blades, you arent pushing air down and disturbing it.

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

PM  EMAIL  GALLERY  Attn:RR  Quote
03-22-2009 09:29 PM  8 years agoPost 29
shuttlepilot

rrElite Veteran

Mullins, South​Carolina

My Posts: All  Forum  Topic

Very true on the dirty air... and I actually didn't think about that when I posted. The air is not dirty below when doing an auto, because no power is applied. It just "seems" to work out better when you carry forward speed, or have a little headwind. On the full scale birds.....I was taught to NEVER auto straight down unless there was absolutely no other option. My instructor would always say "you know helis have skids for a reason". There were also specific climb and descent speeds that you tried to hold to just as in a fixed wing bird......I didn't know that either until I started getting my rating in full scale helis......made perfect sense after my first lesson. I do feel that with any power off descent in fixed wing or rotary, the approach profile is one of the most important things to get right. If it's not good through the profile, chances are it will not be the best landing either...

Gas is Great
Camper Fuel is Better!!
QWW Helis

PM  EMAIL  GALLERY  Attn:RR  Quote
03-22-2009 10:03 PM  8 years agoPost 30
trunkmunki

rrApprentice

Bangor

My Posts: All  Forum  Topic

Doesn't just seem to work better with forward speed, it does work better. The inflow is modified and energy entering the rotor system that would otherwise require an excessive rate of descent is introduced through the forward motion. Too slow or too fast of a forward speed create a RAPIDLY increasing rate of descent.

Google FM 1-203 and read the sections on autorotation. Actually, this (the OLD fundamentals of flight, the new one is a bit abridged) is a great, easy to understand, book on helicopter flight technique and principles. Most work just as well with models as with full-scale.

PM  EMAIL  Attn:RR  Quote
03-23-2009 03:04 PM  8 years agoPost 31
Santiago P

rrProfessor

South West, Ohio

My Posts: All  Forum  Topic

You need to be using SOME power to be in "vortex ring state," so if you are autorotating, you can not be in VRS. This is a MUST for VRS to be encountered
Yep, I picked the wrong condition to describe the how the inside of the rotor blade drives the outside during the auto. A vortex ring does exist but much further out than in VRS.
You are right, I'll fix my post.

Santiago

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
03-23-2009 04:04 PM  8 years agoPost 32
Mosquito crash

rrNovice

PR

My Posts: All  Forum  Topic

Chago @ 48 you havent learn much about vortex rings

Alex Santiago
PR atmio@hotmail.com
will be glad to know

PM  EMAIL  Attn:RR  Quote
03-23-2009 04:43 PM  8 years agoPost 33
Santiago P

rrProfessor

South West, Ohio

My Posts: All  Forum  Topic

Chago you havent learn much about vortex rings
Wow, eso duele cuando lo dices asi! (Thats hurts when you put it like that)
Sometimes we forget things that we learned so many years ago, I'll be the first to say "mi culpa."

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
03-24-2009 07:09 PM  8 years agoPost 34
JetFire

rrKey Veteran

The Golden STATE

My Posts: All  Forum  Topic

These are all good tips. I'm just starting to get a hang of aerobatic autos and they are by no means perfect but good enough to get it on the ground safely. Through my learning curve, I've observed that keeping your heli leveled with combination of some forward speed and a bit of negative is all you really need for your basic auto. The 'popping or tapping' sound of the blades is the sweetspot your trying to listen for. As 'Barracuda' said, you dont benefit from full negative. Going beyond the sound discribed.. is really not necessary. I've found that you can utilize aggressive pitch ranges to position and or direct your heli for an autoing manuever. For instance, I use almost full negative pitch during an inverted auto several hundred feet up.. literally dropping like a rock, before I nose up for a flip about 10 feet high leveling the heli and setting it down. My point is.. you don't need to drop like a rock unless you plan on using the momentum for something else.


Trex700N Pro
DX8-2.4
Spartan/BL9088

-The ONLY way you fail is when you quit.-

PM  EMAIL  GALLERY  Attn:RR  Quote
03-24-2009 08:30 PM  8 years agoPost 35
Flying Brian

rrElite Veteran

St. Clairsville,​Ohio

My Posts: All  Forum  Topic

All great ideas for me!!

I did 3 batterys worth of autos this afternoon, with my 450 Mini Titan. Most say not to, but mine are working nicley from 10 foot mark.

I hope to get higher and higher as time goes on......

Again, thanks for the ideas

"I just don't Listen" "

PM  EMAIL  GALLERY  Attn:RR  Quote
03-25-2009 01:20 PM  8 years agoPost 36
Flying Brian

rrElite Veteran

St. Clairsville,​Ohio

My Posts: All  Forum  Topic

So if I understand this correctly, I can get forward momentum, and go into an auto, with the same effect of turning towards, and into the wind, and proceedoing from there?

"I just don't Listen" "

PM  EMAIL  GALLERY  Attn:RR  Quote
03-25-2009 01:37 PM  8 years agoPost 37
Santiago P

rrProfessor

South West, Ohio

My Posts: All  Forum  Topic

Yes
For example, if you watch all autos done in FAI competition, they start in fwd motion, one involve a full S-turn before touch down, carrying some fwd motion all the way til the last 15ft of altitude, then you bleed that off in the flair on you way to touch down.

Santiago

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
03-25-2009 10:00 PM  8 years agoPost 38
helibro

rrVeteran

hamilton, ohio

My Posts: All  Forum  Topic

thanks, i was woundering the same thing, lots of help.

hey! were is the reset button!

PM  EMAIL  Attn:RR  Quote
03-25-2009 10:38 PM  8 years agoPost 39
canbarelyhover

rrVeteran

Sunnyvale, CA

My Posts: All  Forum  Topic

good stuff

i'm learning a lot from this thread. for example, i just started doing autos but i don't hear the sound people are describing until i start the flare. i'm guessing i have the nose too far down and not enough neg collective.

Citizen #830

PM  EMAIL  GALLERY  Attn:RR  Quote
03-25-2009 10:59 PM  8 years agoPost 40
A. Bundy

rrElite Veteran

Aurora,IL. 30W/SW of​Chicago

My Posts: All  Forum  Topic

For Op- Around neg 3 to 4 is a sweet spot with good blade speed and controllable drop rate.Always dead into the wind for newbie autos.You are looking for a nice gentle 45 degree descent right to your landing area.When just about to the ground,a gentle pull on the aft cyclic begins a flair that will bleed off your fwd speed.Gently add in collective until it settles from there.It's all feel.

http://www.youtube.com/watch?v=NsNM...re=channel_page

Oh,yeah you will crash sooner or later but it's worth it.Autos are awesome and will save your bacon someday.

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 3 pages [ <<    <     1     ( 2 )     3     NEXT    >> ] 3298 views
Scorpion Power Scorpion Power
HelicopterBeginners Corner › How to do a perfect autorotation?
 Print TOPIC  Make Suggestion 

 13  Topic Subscribe

Friday, November 24 - 4:32 pm - Copyright © 2000-2017 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online