loss of rudder control

[Brady Longmore]

Usually the EB flies fine, but lately when I strap on the camera mount from HCS I tend to lose my rudder control once I lift off. I can take the mount off, and the heli seems fine. Put it back on and after lift off the nose slowly starts driffting to the left. I have to put full right rudder just to keep it from doing a 360. Needles are both at 1 3/8 out.

First time it happened I was taking aerial stills just fine. Then I put on the mini dv cam which is heavier than the still cam. After lifting off ( about three feet ) I lost rudder almost completely. The heli did a full 360 before I put it down. Took the mount off right away and the heli seemed to fly fine. But, now it does it even with no camera mounted to the camera mount.

Any ideas where I need to start chasing this problem down?

[MarkWebber]

My guess:

If you have full travel to the tail rotor, check that one of the set screws on the t/r drive shaft isn't slipping. Hold the main gear and try to rotate the t/r. The extra torque of the added weight may be causing slipping or you don't have enough travel on the tail slider.

[cbergen]

Or your headspeed is dropping with the extra payload, resulting in slower tail rotor, resulting in loss of tail control.

I typically set up 2 different models, 1 for payload, 1 without payload. Different headspeeds, pitch setups are needed between the two.

Even with the turbines, we setup different models.

You may also need slightly different needle settings, depending on how much weight, but typically it requires a slightly "richer" setting.

What size tailblades do you have? Too small at slower speeds results in loss as well. Might try going to 110 V-tails if you don't already have them.

[Brady Longmore]

Thanks for the help so far. Now let me throw some more info at ya. I don't think anything is slipping. I tried holding the tail while moving the main gear and it feels solid.

I looked at the pitch hub slider thingy majig and it looks like maybe there isn't enough travel for the right rudder. I took a pic of it and uploaded it to my personal gallery. Not sure how to post it in here. Anyway, there is less than 1/4 inch between the hub and the side of the gear box. this is with the tail blades at 0 or neutral pitch.

Also Chris, you mentioned it could be other things. Let me list how I have it set up and let me know what you think.

First of all I have whatever carbon fiber blades I got from you after my last mishap. I measured them from the bolt hole and they are about 4 1/4 inch long.

I have only one setup on the radio so that could be the problem. Here are my settings.

Pitch Curve

Point L - 0
Point 1 - 17.5
point 2 - 34.0
point 3 - 50.0
point 4 - 66.5
point 5 - 83.5
point 6 - 100.0

The pitch curve is linear. Goes straight from bottom left corner to top right in a straight line on the radio. ( JR XP9303 ) Blade pitch on the pitch guage is set at 0 pitch at midstick and +10 at full.

Throttle curve

Point L - 0.0
Point 1 - 26.0
point 2 - 32.0
point 3 - 38.0
point 4 - 44.0
point 5 - 52.5
point H - 100.00

I can't tell you what my headspeed is though. I don't own a guage.

Anymore help on what might be going on?

[lperagallo]

Brady,

I looked at your picture in the gallery and it looks like you don't have full travel. Do you have your tail control shaft centered so you have the same travel in both directions or does it go further in one direction. If it goes farther in one direction you need to center the tail control arm so when you turn on your gyro and center it in rate mode you get the same travel in both directions. Then adjust your limit pot on the gyro to get full movement both left and right.

If you did have the same travel in both directions, just increase the limit to 140 on the gyro or until you get full throw. I suspect that your weren't centered though.

Once you straighten that out go up in a hover normally in HH. Then when you are stable, go into rate mode and see if the tail drifts in any particular direction. If it does, change the pitch of your tail blades by either extending or shortening the special links on the tail. DO NOT adjust the length of teh tail control arm. Make sure you turn both special links the same amount in or out. Also this is assuming that you tracked the tail blades to start.

It is important that you get someone with a tach so you know your head speed. While your information on the pith curve and throttle curve look "normal", no two set ups are the same. Having a linear pitch curve with -10, 0, +10 is fine as long as mid stick is 0. You also don't have to go to -10 on the bottom if you are doing AP, but you should be at least -5 so you can get it down in wind.

Your throttle curve looks OK, but without a tach, you have no idea if you have a constant headspeed. Since you checked for a slipping tail drive train and it was OK, I would concentrate on getting the tail linkage set up correctly and make sure you have good headspeed. If that fails, then you need to check the gain setting on the gyro and make sure it is set high enough. I usually raise the gain until the tail wags then back off 3 to 5 points.

After a crash that takes out teh tail boom, you need to set up the linkages all over again because you may not have the replacements in exactly the same place they were before. Did you have to take off the servo wheel on the tail servo? If so did you put it back on in the same spot? Again verify all your set up again.

Hope this helps,
Lou

[Brady Longmore]

Lou, thanks for taking the time for such a detailed response. I have a few questions, but since I'm working I don't have alot of time. I do have one question. With the pitch slider hub centered on the shaft, should the pitch of the tail blades be at zero?

And for AP purposes what's a good headspeed? 1500? I might be able to hook up with someone who has a tach.

[cbergen]

With the pitch slider hub centered on the shaft, should the pitch of the tail blades be at zero?


NO!! With the pitch slider centered you need however much pitch is necessary to maintain a hover without the tail drifting one way or another in NON HH mode.

This is why you ONLY adjust the links from the pitch slider to the blade grips when testing your mechanical setup.

http://www.helifreak.com/viewtopic.php?t=19351

Your headspeed should be between 1450-1650, wherever the helicopter and engine are happiest and smoothest.

[Brady Longmore]

Or your headspeed is dropping with the extra payload, resulting in slower tail rotor, resulting in loss of tail control.

I kind of wonder if this could possibly be what's happening as well. Or a combo of problems. There is a definate change in the engine sound as I come off the ground. Almost a bogging noise. I don't lose rudder right away, but after a few seconds of hover.

I have onboard video with sound from the first time it happened. I will post it when I get a chance. Pretty heavy works schedule right now. Maybe some of you guys listening to the engine when it happens will be able to determine what's going on.

Just printed off those tail set up instructions to read while riding the government bus home from the desert. Thanks. If I still have questions or problems I will follow up. Gotta get home and get some sleep for now.

Just to be clear though....

with the radio and reciever all turned on, should the hub be centered with the stick in the neutral position? It's probably in the instructions I just printed off but I thought I'd ask while I'm on here anyway

[rkeith2]

Chris has a valid point with making sure you have it set up for "payload".

I increased my headspeed and listened for that sweet spot sound as it lifted off and maintained the right loading for the additional weight.

Prior to learning this I found a similar problem as yours where the load was slowing enough to overwork the clutch and slow the tail. I also found early on I had the choke lever not tight enough and would creep at times causing a lean condition which mimicked power loss.

hope this helps as well

[Brady Longmore]

Any examples of a "payload" throttle curve? Just to give me an idea. I know it will vary from heli to heli.

Possible big revelation. while messing with it this morning before I go to bed I just found that the tail servo had just about come unplugged! I suppose this could be a major factor. Except isn't it an either or situation? Either the servo is plugged in or it isn't right? If it's moving than it's moving. Or could a loose connection have been causing weak performance rather than just a complete loss?

I still think I have engine / headspeed / payload issues though, regardless of the tail servo.

[Brady Longmore]

Ok I uploaded the onboard video from the first time it happened. Maybe to some of you pros it will be more evident of what's going on here.

Here's a link to where I posted it.

http://s26.photobucket.com/albums/c147/hunyadi/?action=view&current=0d3f4511.flv

What do you think out there?

[cbergen]

Tuning is FUBAR, and headspeed is not where it should be.

Start with flying the heli without the mount, reading what your headspeed is. Make 100% sure your tuning is correct for all modes. Try some high power climbouts to see how your high needle is set.

You can try masking the poor tuning by only adjusting the headspeed, but all you'll end up with is a burned out motor if you're lucky, a crashed heli if your not.

Any possibility of spending some time with Gary?

[Brady Longmore]

yeah, maybe another trip down to SLC is what's in need if I'm that messed up. I've been trying to figure stuff out on my own these days to force myself off the crutch of always asking Gary. I've learned a bunch on my own that way, but I don't want to ruin my engine and stuff.

Can someone post their payload throttle curves still? I'm just curious.