damonlee

My main experience with fighting the wind seems to be updrafts and downdrafts...not side to side.

I'll be flying and suddenly the heli will be "pushed down", or it will just ascend.
Other times, when I'm over around 12-15 feet up, I'll lower throttle and will not descend.

I'm not flying in Idle-Up.

I'm not sure if it just the wind or a "rotor wash" thing...

Is anyone here an expert on the physics of the heli as it pertains to rotor wash?

jp473

I experience the same thing you outlined. Have noticed that when I get close to the street or large body of concrete I get uplift without stick input. It’s still pleasant out in Texas and not hot yet. It is noticeably cooler over the grass.

SeaComms

What you are describing there is basically a thermal - the holy grail for glider pilot!

As for up down, when you look at the heli in the air, the blades will be tilted slightly to the right when observed from behind. A level breeze from the left will effectively hit the underneath of the blades and generate more lift, a breeze from the right will hit the top of the blades and generate a downward force.

So it is a rather tricky endeavor to fly in gusty wind with a light heli.

soloboss

Ohhh NUTS. I'm sure you are correct, Seacomms. I figured I was leaving that stuff behind with the move from a featherweight FP heli to a 450 class CP heli. But I had never thought of what you said about currents from the left and right.
That's obviously a large part of the reason for bigger and heavier helicopters.
I need a flying PIG!

damonlee

SeaComms, The blades tilt to the right while hovering? Why to the right?

SeaComms

Ok, some basic single rotor helicopter dynamics - standing from behind and looking down on the heli, the main blades are rotating clockwise, so the body will try to rotate anticlockwise - just a normal reaction.

The tail rotor now comes in to play and will try to rotate the heli clockwise. We dont want it to actually turn, just stay still, so the tail rotor is controlled in pitch or speed (depending on the design) by the gyro to apply just enough force to stop it rotating at all.

Now if you look at the tail rotor, this is not only stopping the heli spinning, but since it is the only thing blowing wind out the sides of the heli, its giving us an unwanted push to the left as well. To counteract this and enable you to hover in one spot, the heli has to be trimmed with a small amount of right cyclic to stop the tail from pushing the whole thing to the left.

Hence when you look at it from behind in a hover it will be leaning to the right to counteract the tail pushing it to the left.

This is also why when you first take off slowly into a hover it will slide left, as the heli at this point is sitting perfectly level and not counteracting the tail pushing you sideways.

A very fine balancing act when you think about it to hover in a stationary position!

BryFlyGuy67

Good explanation!

redlance88

it may also be worth mentioning " ground effect " at this point. you will find that as you get close to the ground in a nice gentle landing the decent rate slows down or even stops , requireing that ya lower the throttle even more to actualy land. its the same efect as the wind has in adding lift to the heli only this time its the down wash from the blades bouncing off the ground and back up into the rotors causeing extra lift. As you get higher, ground effect goes away as the " bounced" air gets dispursed and stops effecting the lift of the helli. Thats why after you get them up a few feet ya need extra power to keep them hovering than when very close to the ground.

always be aware that random wind can have some odd effects on helicopters and tho the b400 probably dosen't generate high enough head speeds ( don't own one yet , so don't take what I am saying as fact for the b400's ) it is possable for some helicopters to create vortexes off blade tips that reduce lift and can cause the choper to decend even with lots of power being applied. again I don't think its a likely situation for the b400s to have to deal with , but its worth learning about how helicopters work out at the edges of the flight envelope.

Evan T.

its also why when you take off into a hover and it raises from the ground its going up until a certain point then it stays level until you put in more throttle input to make it rise even more

H3li

Reminds me of my experiences with my Blade CX2. Yes it is a sweet little Heli (for indoors), taking it outside was a different matter.
As soon as it lifted off it would generally be bounced around by the wind, until it finally flew into something, or the ground! Could only fly it low and for short bursts.

Therefore my larger 450 class Heli purchase HAD to give me the outdoor flying/performance that I had craved!...

I considered the Blade 400, but in the end opted for the 450 Thunder Tiger Mini Titan. This Heli is heavier than a Blade 400, also a little larger also.
In gusting/blowy winds I will admit the Heli does occasionally twitch as it works hard to 'fight' the effects of the wind, but so far, doesnt seem to be affected in the way described here. It has a rock solid hover, and doesnt ride up/down on it's own, through gusts.

Perhaps a slightly larger/heaver battery would help stability on the 400 - potentially more powerful too, plus better performance?
Upgrading to the metal Head/Tail components will add a little extra weight - would be marginal, but could also help stability on the 400?
Would definately help provide a tighter, more responsive heli

Zeeb

My Feedback: (41)

You can say that again!

I've got about 6 hours in a small full scale (Hughes 300) and my instructor compared hovering to "trying to stand on a basketball"...

H3li

Head speed is also a factor, when discussing the Heli's ability to fly "through" gusts/wind.

It even affects a solid hover in NO wind. For example, when your Lipo is low you 'hear' the head speed drop, also control becomes more sluggish.
Might be worth looking into a different motor pinion, that drives the main gear? Or upgrade to a more powerful motor!

cobra525

My Feedback: (5)

Standing on a basketball I like that. I guess nose in hovering would be standing on the basketball with rollerblades then. Anyways Head speed is the key. The Blade 400 actually flys great in wind for the micro electric it is. Im not so sure any other heli would do much better. It has amazed me at times. Of course if the wind is 12 or 15 mph I would be flying a nitro heli instead. If any heli is being dominated by the wind or blows upward drasticly while flying, you certainly need to increase the head speed. You could also have to much pitch or both. Not decsending right away is not really a bad thing, however I beleive its always good to have a setup involving some negative pitch. At least 2 or 3 degrees at the bottom of the collective. There could be situations where you need the heli to loose altitude now. In spite of setup however, its always good to be one step ahead of your heli specially on windy days. Constantly working the collective as well as the cyclic will help react quicker to updrafts and things like that.

Crusader23

My Feedback: (1)

You mentioned nitros and I'm curious to know if they fly better because they're heavier or larger? If the B400 had a nitro version, would it fly any better than the electric version?

cobra525

My Feedback: (5)

The bigger heavier nitro heli would yes be able to withstand higher winds (to a point). A bigger rotor disk manipulating more air always wins. A nitro motor also provides excellent power and in my opinion transitions smoother. If you can hover a squirly electric (with the exception of the blade cx) a bigger nitro heli would be a walk in the park for most people I think..

Wolfpackin

Forced Down by the Wind

I keep hearing about heli's being lifted up by wind or problems that arise if you have no negative pitch and get caught in an updraft.
I'm experiencing exactly the opposite on windy days, or even slightly breezy conditions.

I run what I think is a high enough headspeed, 100-90-80-90-100.
My pitch is good -10/0/+10
My B400 is mostly stock except for HS65's on cyclic, and I'm using stock wood blades.

It seems that whenever I get hit by a small breeze my heli gets pushed downward.
Sometimes a moderate breeze, I'll guess between 5-7 mph will push me all the way to the ground from 15-20 ft up.
I know that my collective management needs improvement and I'm still a little slow to respond.
But it seems that at times I'm giving close to 100% throttle and pitch and still can't keep the skids from touching the ground.

What's going on here?
Is there anything else that could contribute to not being able to fight that push downward as far as setup?

My only guess is that I'm not reacting fast enough or with enough collective to recover.
I'm sure my altitude (7,500FASL) doesn't help either when trying to get some aggressive lift.

Any thoughts???

rotarydoc

Hey Wolf,

No thoughts on what to do about it, but I am in the same boat!

Your description sounds very familiar, for sure.

I am on the other end of the headspeed scale, I have a very high pitch curve, and pretty low headspeed, for a slower cyclic response, and I still get the same thing. I have also had the skids bounce off of the ground a few times due to this phenomenon.

It doesn't seem to take alot of wind to do it, either. Just like a random downdraft is pushing it straight to the ground sometimes...

Also running stock wooden blades, and JR DS285 servos.

Maybe someone can explain. I guess I can attribute it to Seacomms suggestion of being in a "thermal" for now....

Glenn

cobra525

My Feedback: (5)

That sounds pretty scary and not very enjoyable. Several things come to mind from what your saying. Uneven mountainy terrain, or large buildings nearby can make wind do weird stuff. It could be a Setup thing or mechanical problem too. Sounds like you are running out of Positive pitch but have plenty of Netagive. Please keep in mind I have no idea how advanced we are, so I dont want to indirectly insult anyone by explaining something you may already know or sound like I know everything. Just honestly trying to help.

From the Pitch range and throttle curve you are running it sounds like you are flying some mean 3d aerobatics. As far as setup, I would first get better blades than those. attempt to adjust my blade grip pitch links just one turn at a time towards pos pitch. That should help make drops less severe for sure. If not flying 3D I would setup a pitch curve with a bit more positive than negative thru the collective range.

One could expect things like that and more from too low a head speed though. But Its is fun and relaxing to flutter them along like that. it makes the rotor sound cool too.

If I were concerned mechanicly, I would pitch guage the blades to make sure both blades have the excact same pitch and creating even lift. if they are not even, one blade can create dirty air for the other thus loosing some lift. A slightly bent feathering shaft can cause one blade to fly higher than another, or maybe one blade is too loose on the grip itself and the other is not. If your drive gears and system isnt turning 100 percent freely and smooth, your head speed will drop quicker than it should when only a little power or collective is taken away also causing a similar thing. Tail belt too tight, bad bearing on the motor or a shaft, main shaft slightly bent

Wolfpackin

rotarydoc,

I'm glad I'm not alone.

cobra,

Thanks for the input.


I'm running this same question on Helifreak and I'm beginning to think that my problem is a result of wierd Rocky Mtn. downdrafts and my lack of a quick and aggressive enough reaction to the downward push. And of course the fact that I'm at 7,500FASL where there is less lift.

I take a lot of time with my setup and as stated above I'm running about 90% throttle in a hover.
My tracking is good and everything turns freely.

I've tried a little more positive pitch to +11 but a flyer more experienced than I said that the motor was bogging so I lowered it to +10.

I flew this morning and only once did I get forced down. This time I just jammed the stick all the way up. There was a slight delay but after that the heli recovered and shot straight up.

I think time will tell if it's me or something else.
I'll probably try some 335 Pro's to combat the lack of lift up here.

Thanks again, guys.

rotarydoc

Hey Wolf,

Nope, you are not alone. Now that you mention downdrafts, you gave me an idea.

One of the places I fly that I notice this phenomenon most, is an industrial park parking lot. It is very large, and open, but it has buildings on 3 sides...

I am wondering now if I am getting a nice big downdraft coming off the roof of one of those surrounding buildings pushing the heli down.

I have a couple of other places I fly, I'll have to start taking notice of where it happens...maybe it's just my choice of flying areas!

Something more to ponder, I suppose!

Good luck up there in the thin air!

Glenn

J-MICHAEL

Ray

Yes my friend you are NOT alone...! Try here in Central Cali by the coastal winds at 1600 ft elevation on the side of the mountain here as the winds come sneaking over the top of the mountain from the coast and trying to slam my Trex to the dirt ! One thing that helped for me is taking off my 325mm blades and putting my 315mm CF blades on... Don't ask me why, but it works for my set-up along with running a high head speed in idle up. I imagine it might make the heli more responsive to counter my sometimes slow reactions. You think it would be opposite as you are losing lift, but for me I use what works. I'am sure your elevation is a big factor...

Sometimes my palms are dripping wet as it does surprise you when it happens, and it's not fun to experience...

Saw your flying field you found by your house in Colorado, as I was pokin around the forum a bit ago...Very nice you lucky dog ! I can't wait to go back home to Washington in a few months, as there is a better selection of flying sites there. Seems the forum has been slow compared to what it used to be. I guess everyone gets busy like I was I guess...I'am glad to be back in the game, as I missed my heli's for the few months that I didn't fly, but thought about them everyday !

Check out the terrain I have to fly in


http://www.youtube.com/watch?v=EebO5JwaL3c


http://www.youtube.com/watch?v=S_j_F4mvbKs

Downdrafts ?! All over the place here ! It's a bummer, but much better for me currently... A glider would be killer here as there are thermals everywhere, you watch the turkey vultures, and there literally flap free all over the place gliding all over the place.

See ya around,


Jeff

Wolfpackin

One of the guys that flys in the same place as me had a glider up for over 40 minutes last week. I guess there are some decent thermals there.

Thermals, downdrafts or I'm really slow...one of those things.

Thanks guys.

Jeff,

Great to have you back.
I saw your videos, very nice.
I'm getting there.

vince.b

My Feedback: (1)

when fling in the wind you want a higher head speed... ie idle up.

blade400

also another major cause of having the heli just suddenly drop straight down with wind or no wind is called power settling or settling with power also known as the vortex ring state as for the up motion of the heli i would say that is a thermal ... most of these 3d heli's can get out of the situation with a little effort but the correct way to lower the vortex ring is to simply fly forward out of it and reduce the pitch slightly.... i too experience this with my blade400 all the way up to my raptor 50 and 90 ..
here is a link that will explain this a lil more..

[link=http://en.wikipedia.org/wiki/Settling_with_power]vortex ring state[/link]

Roadtorque

Well not really fact but the idea is the same. In-ground effect happens when you are within one rotor diameter of the ground. The wind doesnt bounce off the ground back up to the blades causing extra lift, what happens is the air hits the ground and is directed out and away from the helicopter parallel the ground, this reduces the vorticies size at the blade tips allowing a greater surface area of the blade/disc to produce lift. When you are further than one rotor diameter from the ground you are in an out of ground effect hover. The air in this situation gets directed straight down. The air around the tips of the blades goes down, out, up and re-introduced into the rotor sysetm. This is nothing more than a very large vorticie. The larger vorticie takes up more surface area of the disc/rotor therefore less area to produce lift requireing more pitch/power/collective in the blades to get more lift.

As blade400 said votex ring state is a factor with helicopters but is not due to thermals. This state should only happen when you have slow/no forward airspeed and a tail wind. What happens here is the dirty air/vorticies from the tailrotor get pushed into the mainrotor causeing a loss of lift and the disc begins to settle in its own downwash. You do recover from this by lowering pitch and gaining forward airspeed (Requires altitude to do this) if you dont recover/have enough altitude you will hit the ground. This sounds like what is happening to you all. If hitting the ground when you have a head wind this can happen from low forward airspeed and high descent rate which again is vortex ring state. Same recovery here