Has anyone tried Auto Rotation with the MX 400 Pro? I have only tried about 3 feet up! Results?

jmacg8r,

I don't have a MX400, but autorotation works by the same principle on all helis that have that feature. - As far as I know, if you would be flying up high on the air and somehow your it looses power, rather than coming down like a rock and smash on the ground, a helicopter with autorotation would spin on its axis slowly and have a smooth touchdown without having a crash. - If your heli has two main gear wheels at the bottom where the main motor is, it has autorotation. If with the heli without power you can move the blades the opossite direction they rotate normally, and you feel they are loose, very loose and your main motor pinion doesn't rotate, it has autorotation.

*Don't do this at home* - But if I am not mistaken and I understand well, if you got up on the sky and turn the TX off, it should come down all by itself smoothly and nicely without a crash..... But don't take my word, don't do this, so if you crash it you won't blame me for telling you this.... hahaha! - Your manual should tell you how autorotation works anyway....and certainly it has to do with your heli loosing power, it is a big nice improvement on expensive helis as a safety measure to prevent crashes from high alttitudes.

Regards...

Should be duable but do to the weight of the blades will be hard. I myself have a mx 400 comming to practice auto's, loops, rolls, inverted without putting my 1000 dollar nitro at risk so i don't know yet. I just started auto's with my nitro and it is hard to say the least. It really takes alot of cordinated cyclic and collective movement. The t-rex's at my field spin about 3-4 revolutions on the blades before the stop (even with the one way bearing). My nitro hawk will spin about 30 times before the blade slows to a stop.

Cambo-- there's something seriously wrong with the TRs if they only spin 3 or 4 revolutions before they stop after shutoff. My MX450 keeps going long after the motor is shut off, even with negative pitch on the blades, and I've sen TRs auto'd, too.

Either way, auto on a mini is an exciting thing, to say the least. My only auto IRL was from about 4 feet up, so it doesn't really count (just set it down, really), but the rotors on mine have a heck of a lot of momentum at 3000 rpm. If you take rapid measures to maintain HS you should be able to do it, but I'd practice with the flare at a good altitude first, and with throttle cut set up to keep the motor spinning a little at least to inhibit a soft start. Don't want to be spinning up slowly in the air.....

Auto's are extremely difficult. In case of engine/motor failure the rotor system is powered by the upward flow of air through the rotor disc. The heli will not do it by itself. If the Tx is turned off it''ll drop like a stone.

For an auto you need some foward airspeed. This will keep the rotor spinning and maintain as much headspeed as possible. Rotor RPM's have to be maintained throughout descent. You'd probably have to use a fairly low collective setting to miantain headspeed. Then a few feet (not sure how much exactly) from the ground you'd flare the heli and pull in more collective. All that stored energy in the rotorhead now translates into lift and will alllow the heli a nice soft landing.

Can you explain a little further on how to auto rotate? I have really only hit the throttle hold switch. Are there specific TX settings that should be in place? Thanks for your help.

The theory is simple-- on loss of power, by establishing a negative pitch angle (heli upright) before your hs decays below controllability, you can use the airflow as the heli descends to maintain headspeed (the air drives the rotors instead of the other way around). The autorotation gear on driven-tail helis disengages the motor drag from the rotors, and the mains rotation continues driving the tail so you have yaw control. If you maintain the energy in the head during descent, you can flare at 3-5 feet above the ground by increasing collective to a strong positive angle, converting the remaining energy into lift to cushion the landing.

In practice, the descent is very rapid, and it takes a good amount of practice to judge the flare and to get the timing right so you don't stall (with no remaining energy) above the ground, or flare too late and just make a hole. You usually practice autos by reducing the motor to idle and flaring far above the ground so you get a feel for it but still have altitude to restart the rotors. It's tricky to get it right. It's even tricky to practice without crashing, for that matter.

Osterizer do you go to actual negative pitch or keep the idle-up in normal mode and pull the collective all the way down to the 0% stick setting?

Oster's right though practicing up in the air is a good way to go. These helis have alot of power for their size. This makes them more forgiving then their full-size counterparts. It also means they can power out of a bad auto (with enough altitude) plus their blades will never reach the critical coning angle.

When doing an Auto you'll want some forward airspeed this helps maintain the headspeed. As far as the collective settings they're going to vary. It's a compromise between maintaining headspeed and arresting descent. And as Oster said the flare is very critical. Flare to high and it falls out of the sky, Flare to low and your heli's subterranean. This is an advanced maneuver so if you could find an experienced local RC heli pilot or use a sim it would help alot.
Good Luck!

The helicopter does NOT spin smoothly to the ground in an auto, nor does it do its own auto if you turn off the transmitter.

You need negative pitch to do an auto with a model. There's a point on every heli that depends on blade weight, airfoil, helicopter weight etc that you need to find, any less negative and you loose head speed, any more and you only fall faster without gaining head speed.

As for MX400's and lighter electrics, they auto like a brick.

[link=http://www.youtube.com/watch?v=6eG8EOTBn1k&NR=1]Here's a nice little tutorial on Auto's[/link]

[link=http://youtube.com/watch?v=hspdy_dTQ4A]Here's a vid of a good pilot doing Auto's.[/link]

[link=http://youtube.com/watch?v=T2MfyjHJ6Ko]...and here are some Trex Auto's[/link]

jmacg8r,

I can't explain in details how autorotation works, because I don't have a heli with autorotation, neither I've ever seen one doing what's suposed to do, but from as far as I know, it is a system that minimizes the damage caused to a helicopter with autorotation, in the event that it falls down. - Even the real size helicopters as far as I know if not all, most of them have autorotation safety mechanism.

Don't do as I said turn the TX off to try, as someone else explained to you already, that will make the heli fall down as a rock. I have no idea how you test it, and all I know is that it protects a heli with autorotation from getting destroyed if it falls from a high alttitude. Seems like you have to manuveur a bit before it lands for autorotation to work, but I think it's alot easier to land it under that circumstance compared to a heli without autorotation.... in other words your forced landing will be alot smoother than with a heli without autorotation.

It has to do with negative pitch at the time of landing, those the heli tries not to fall down as hard as the normal way without autorotation.... like saying "I don't want to fall..." so by changing the blades to a negative pitch, it tries to land as smooth as possible, but you have to control that yourself a bit before landing.

Look at Heliko's post, go to those links and learn how it works. ;-)

Regards

Ha, yep. With a mini the only way to tell a successful auto from a crash is that the pilot isn't swearing (usually) and not a lot of stuff breaks (usually, unless the pilot is swearing). I expect that it's a pretty puckerful maneuver even in a full-sized helicopter.

By the way, I have watched people do this, but I don't do it myself IRL. Practice on the sim is enough for me, just in case. The only time I've had to auto was from about four feet up, and that just needed the flare, not the autorotative descent-- and the descent is what takes skill.

If anyone's curious, the way it works is that with some negative pitch on the blades (as BH pointed out above, finding how much is difficult), the inner (slow moving) part of the blade stays stalled, the middle portion is driven by the upward flow and keeps the blades moving, and the outer, fastest moving part actually keeps flying and generates lift for control during the descent. Pitch and headspeed control the size and location of these zones on the blade. You might guess from that the reason that it's difficult-- that's a very fine balance to maintain, and you only have a few seconds to establish it between when you're up there and when you're down here.

Autorotation is a lifesaver skill in a full scale heli, BUT 1) you have to clutch out the dead power plant, and 2) you do it when your power plant is dead.

Speaking purely of small electrics, not the nitros, if your power plant is dead, you have lost power, ie: no battery (the electric motor just uses the electrical power to convert it to mechanical power. No power means no electronics or electrical, that would be servo's and receiver.

When you autorotate a fullscale bird, you still have to fly it. Even if you have a direct driven tail rotor, which would imply some yaw controll, how do you control roll, pitch, and yaw, with no electronics?

Am I missing something, or just old and feeble?

not at all-- but motors die, gears strip and (in my case) dumb-a// pilots ignore the flashing I'm-getting-ready-to-cut light on the ESC! (in which case you still have juice for the controls)

Its also beneficial for tail rotor emergencies like a shreded belt in my case, remember throttle hold, no torque to the blades means no need for a tail rotor.

Osterizer,

Thanks, but i gues it's a moot point for me unless the main rotor drive train breaks without taking the rotor head with it, I fly,,,, I try to fly an Axe CP, They AR like a frizbee made of lead...... no way to release the main motor.

Mr. BaracudaHockey,
Are you sure that you would call it AR if you lost yaw control with the tail? Sounds like a pirroette (sp?) landing to me. Hope your bird made it out alive.

See ya!

Quite the opposite. The tail rotor exists to counteract the torque of the main rotor. No power to the blades means no torque. As long as you are moving into the wind the tail will follow behind and the autorotation proceeds normally.

I think (well, I try to...) In a full scale bird, at least, If you can get (or retain) forward momentum, the gyro-copter effect comes into play, with with horizontal air flow contributing to the main rotor's rotation and generating some lift (lift is a GOOD thing), makes sense that tail only serves as rudder control in this state. Same would seem to be true for model helis.

But, at some point, it becomes necessary to transistion to vertical flight. Brain says (I always talk to my brain, keeps me company, oh, where was I?) " in vertical flight without main power, ie: AR, whilst the airframe is descending (like a happy rock), it is advisable to clutch out failed power plant and apply somewhat negative pitch (positive pitch works also, but you need to let the main rotor stop rotating in it's powered direction and let it begin to rotate in the opposite direction because of induced atiflow,, would take even more time than reading my posts, all the while vertical speed is increasing and whatever altitude is left is rapidly decreasing), so, where was I,,, where am I?) Main power takes a break, mild heart attack, throw the clutch disengage, drop the collective, rootor keeps spinning, off we go, into a wild descent... At this point, upward airflow through the main rotor is forcing the rotor to keep moving. The kinetics ot the airframe (and horrified pilot) want to oppose the spining main rotor (or, you might want to think of it as resistance of the rotor to the airframe want to sipn the airframe and rotor as upward airflow influences the main rotor. bird spins like a top as it falls, somewhat slower, to the awaiting mother earth. Pilot recovers from subsequent mild heart failure and stomps on rudder pedal in an effort to overcome runaway yaw induced by the above (that's supposed to be one of the skills of AR)."

I would think something similar occurs in a model heli.

Again, My AR experience with the axe is that it ar's like a brick

Yall have fun!

In the spirit of discussion, not banging on ya, I beg to dissagree.

The tail rotor ( or the jet exhaust on the turbine powered tail-rotor-less designs) exists to affect yaw control part of 'pitch, roll, and yaw', the rudder function. This is accomplished in a helicopter by compensation for main rotor drive torque (usually by inducing a controlled force (derived from airflow generated by the tail rotor or a turbine exhaust) in opposition to torque of the main drive).

Thinking of the tail rotor force as merely a means of counteracting main rotor torque is a good way to simplify the understanding of heli flight physics. But, you need to see the yaw control part to tie in all aspects of controlled flight ( I, myself, seem to exhibit a penchant for un-controlled flight)

You, Oster, Helico, and the others have far more experience in these birds (and I don't abuse a 400 yet, I just play with Axes), so I bow to your knowledge. I'm just asking questions and posing unwanted opinions.

Best wishes to all for happy flights from an old geezer.

It was a simplification but alas with a bit of forward speed, and no power being applied to the main shaft, the tail rotor becomes unneeded (a fact that some designs disengage the tail and it stops during autos) yes you loose yaw control but you dont have the drag of a driven tail rotor slowing down the main's during an auto.

Splat, BH is right. The primary function of the tail is anti-torque. In fact many full size helis only use the tail rotor to yaw in one direction. Yawing in the other direction is accomplished by the torque of the main rotor with the tail rotor at zero pitch. The MD520N NOTAR you spoke of gets much of it's "anti-torque" from the rotorwash passing over the outside of that large tail boom. This is called the Coanda effect. So the sliding vent in this case acts more like a rudder, but understand the series of McDonnell Douglas 500 helis are more of an exception than a rule. They're basically a fighter jet without wings. They can loop and roll without problems. I've also heard of them referred to as the "Porsche of helicopters".

The rotor doesn't need to spin in the opposite direction for an auto. This may help explain that. Instead of thinking of the rotor head as individual blades think of it as a rotor disc. Then think of the disc as a wing on an airplane. After all it works the same way. This is why forward airspeed is important in real heli autos. Also in real heli autos RPM managment is critical as you can still overspeed the rotor. On RC helis I imagine just get all the headspeed you can.

Autos are basically a controlled fall. You start by dropping the collective. This allows the flow of air coming up through the disc to keep it spinning. The low collective setting has no lift, so it has no load therefore no reason to stop turning. Like a pinwheel in the wind. Keeping RPM's up is critical because the RPM's in your rotorhead are the only power/stored energy you have to arrest your fall. A certain amount of forward airspeed is also necessary because it not only allows more wind through the disc, but dramatically speeds RPM's at the flare. Increasing the collective at point of flare allows the RPM's in the disc to produce lift. Ideally this allows the heli to settle to the ground gently.

This is over simplified quite a bit, but I hope it's enough to get the idea.

I was refering to when you spin the head by hand. Not as it spools down.

Ahhh, ok.

Hi Guys,
Been out of the loop for a couple of days. As I said earlier, I bow to your knowledge and experience. Seems we are all saying the same thing about the physics, just coming from different angles. whether you say Yaw Control, or Torque Compensation, you are still talking about the same forces acting upon the same object (in mho). I'm tyring to wrap my brain around your view and I think I get it.
If I was gonna continue to argue my position, I would ask if you thought alierons (sp?) on a fixed wing were just there to counteract propeller torque. BUT, if you think about it for a minute, in a way, you could..... (An open mind is not always a good thing,,, every time I open mine, things start falling out...)

It has been a great brain exercize. I enjoyed it and picked up some new ideas and ways of looking at things. If I have offended or riled anybody, I, most humblly, appologize.

Good wishes to all.

The ailerons dont really counteract the engine torque as the wing moving through the air would, just as a helicopter in forward flight doesn't need a tail rotor to maintain heading. Take the airflow away though and torque rolls are fun and in that case you do need aileron opposite the torque to maintain a stable hover.