Bell OH-58 cyclic issues

[Radam559]

So I am looking for some information or advice on what could be going on here...


I am having a problem with not having enough left cyclic when I am leveling out from a right turn. I am an ag pilot so I am flying somewhat aggressively, but not overly so especially with this issue. Basically I have no trouble turning to the left... helicopter will come right back up when I use right cyclic, but when I make turns to the right the helicopter is very sluggish to right itself and if I am not careful when I initially bank, I will hit the left stop trying to bring it back to level. I have noticed that even a slight right bank to correct my alignment coming into a pass will cause the same sluggish feeling like the helicopter doesn't want to level its wings out... This is happening when I am loaded down and when I am empty so I don't think its a heavy issue or a "liquid not being equal in both tanks" issue. Weather I maintain airspeed throughout the turn doesn't seem to make much difference as the situation still occurs. When in cruise flight I do sense that the cyclic is sitting a little farther left than it should be, even to compensate for any translating tendency there may be. The mechs say the rigging is all good but don't seem to interested in helping me solve the issue, almost as though its not an issue...and maybe its not, maybe its me, but my chief pilot and our other pilot say the same thing about the aircraft and I thought I would come in the forums and see if anyone out there may have an idea of what might be going on...


Thanks for any help

[Saint Jack]

Radam559: First, it is strongly suggested that ANY helicopter-related questions be posted on the 'Rotorheads' forum - you'll get a much better response.
Has this problem always existed or is it recent? If it occurred recently what maintenance was carried out on the helicopter immediately prior? Did the helicopter suffer some kind of flying incident/accident just prior?
Check to ensure the cyclic stick is properly inserted and secured in the fitting at the base (under your seat). If this is correct then carry out a FULL cyclic rigging procedure and start by inserting the rigging pin up through the lower fuselage into the hole in the cyclic pivot (the uniball), remember that it's easy to miss the hole (no jokes please, I've heard them all!) so release the cyclic friction and try to move the stick - if it can't move then then pin is inserted correctly.
Work your way up to the two vertical control tubes connecting to the swashplate fixed ring - notice the slight difference in the required lengths.
If the helicopter hovers with the cyclic stick to one side then use the adjustable rod ends of these control tubes to make corrections.
Let us know the outcome.

[pitch horn]

In addition to doing a "Neutral" rigging check a "Range of Movement" rigging check should also be carried out. It's all in the M.M. Chapter 67 (Flight Controls).

[AAKEE]

Do you have any other OH-58 to compare with ?


If you dont find any problems in the rigging, perhaps time to consider the aerodynamic situation for a rotor turning i that direction ?


(mabe known, but as repetition:)
The gyroscopic precession makes the input needed to be 90 degrees before the desired action. To roll to the right, input with increased lift will be 12 a'clock in clean air. To roll to the left input with increased lift will be 6 a'clock. The air flow through the rotor is down, reducing the effective angle of attach on the blade in the 6 a'clock position.


I did'nt fly the OH-58, so I dont know how it normally reacts. If I remember right, you can sometimes feel the difference in left vs right roll command in Bell 206.


For more about the phenomenon, read about Bo105 and this issue.

[wrench1]

559,

1) What model is your OH-58?
2) What do you mean by "sluggish"? e.g., when move cyclic left there's a delay before aircraft moves, or excessive back pressure on cyclic, or the roll rate is slower/faster left vs right, or etc....
3) Off topic: Do you have to hold T/R pedal when flying to center the bubble?

W1

[Gomer Pylot]

What is the lateral CG? It should be easy enough to compute from the last weighing data. It shouldn't be more than a tenth of an inch or so from zero, two at the most. You should also compute the lateral CG for empty and full, and probably somewhere in between. If you're staying within the lateral CG limits, then you need to have maintenance look at rigging. Hopefully you have a competent A&P available.

[Radam559]

Thanks for the reply's guys...








Its an OH-58 A+ and when I am referring to it being "sluggish" I mean the roll rate just seems slow... there is no delay in the reaction when I apply cyclic it just rolls slow. I would say that there is minimal if any T/R pedal that needs to be consistently held during cruise flight, but then again I am flying aggressively while coming in and out of the field over power lines or other obstacles so there is some pedal work with regards to the power changes that are being made. typically when I am in my spray pass at about 60 I would say that I have a lot of right pedal in to keep the ball centered... I find that when I am making my turns (either direction) I am always needing right pedal to keep the ball centered, left turns are requiring a more right pedal. I am still somewhat new to the Ag industry so I know I am not the smoothest pilot out there, so there could be something to that, but I do try and stay in trim as much as I possibly can. I have heard one pilot from a different operation saying that with the saddle tanks (like we use) there can be a tendency for the fluid to shift to one side that can cause cyclic issue, but as I said before, it seems to want to do it weather I am fully loaded or even empty, so i don't know. I'll have to do a little work and check into the lateral CG... The mech did tinker with the swashplate today so well see if that makes any difference either good or bad.

[wrench1]

559,

1) Is the left roll rate issue comparatively the same in hover vs 60 mph spray run vs normal level cruise >75 mph? Or just during 60 spray run?
2) Is the backpressure on cyclic the same for left and right inputs?
3) Is the cyclic force gradient/mag brake system still in stalled?
4) Has the T/R rigging been checked recently?

Three items stand out:
A) “…I will hit the left stop trying to bring it back to level.”
B) “…cyclic is sitting a little farther left than it should be…”
C) “…at about 60 I would say that I have a lot of right pedal in to keep the ball centered…”

A&B could be related but…in my opinion…you should not be hitting the stop with the maneuvering you describe. There are a list of possible causes for A&B, but it’s C that strikes me as odd. I would think if you needed to hold pedal it would be LEFT pedal at that speed/power. Unless the T/R is out of rig and/or there is an exterior aerodynamic force exceeding the torque effect of the M/R.

W1

[aa777888]

Maybe it has something to do with a lightly loaded rotor disk, you know, with less than 1G on it when making the turn?

[coochief]

Radam559,
I'm glad to hear you are cropdusting in an OH-58A+ as that is what I do as well. Curious where you spray at and what crops?

It could be that the pitch links are not set quite right and that will take a wrench with some savvy to correct that, don't start changing them on your own.

Anyways, I'll try to condense this if possible: I see you said that you fly "aggressive" and that is great but trying to make quick turn around times and get acres and be smooth takes time and practice, any body can tear up/torture the machine and make time but being kind on the equip and making time is what works in the long haul. I say this respectfully and maybe your just expecting a little too much out of the machine, it is not a 500. I know Boss man wants acres though too...

So with that being said, I think you are starting to bank like an airplane using the ailerons to tilt the helo to the right a little too much during the turn then all the sudden you are trying to remove that slant/bank . There are different ways to do turns and some depend on your terrain and obstacles. But what I've discovered purely on my own over the years that helps with tight turns is this technique with the collective. Think: "Raise Right, Lower Left" Therefore give the collective just a little nice gradual bump or lower it while in a turn. About half way threw a right hand turn give just a little raise without increasing or using any pedal and the nose will come right around and you wont have this big banking effect that your are trying to overcome. Vice versa with left handers to, and you approach the end of field and climb out and erode airspeed and begin a turn lower the collective just a little more and the nose will come on around even easier then very steadily pull that power back in. This will not come naturally over night and its hard to do when your loaded, I do banking turns also and do skip pass if needed as well. I use a Dynanav and it allows a free form pattern which is handy, a lightbar system does not allow that I don't believe. Goodluck!!

http://C:\Users\Admin\Pictures\Helo Spraying 15'\Resized Helo Spraying 15'\DSC_0211 (1024x663).jpg

[Gomer Pylot]

If you're not keeping the aircraft in trim during the turns, that can account for much of your issues. This airframe weathervanes strongly, and does not like being out of trim. It doesn't fly sideways happily. If you fly aggressively, you need to be aggressive with maintaining trim. Keep the ball in the center, always.

[nigelh]

when i did my spraying training in the States i was trained to use collective for a big slug of the rotation and not cyclic . I think its easier on the machine and you are not chasing the pedals . Twas a long time ago mind you !!

[Radam559]

Thanks for the feedback Coochief, I love hearing about how and what people are doing with regards to ag flying.


I will start by just saying that when I say "aggressive" flying, it is not quite what you probably think :). I am new to ag flying and still learning, but it is definitely more "aggressive" than any type of flying I have done before, but far from anything hard on the machine (except I am pulling a lot of torque getting off the truck occasionally, but try to be as gentle as possible and get it down a soon as I can) and I am very careful (or try to be) with everything I do. I try to be as smooth as possible and not just yank on the controls like crazy. I am definitely not of the mind set that I need to be doing things quickly or anything like that at this point in my ag flying career. That is one great thing about the company I work for and my chief pilot...absolutely no pressure and letting me take my time getting up to speed.


I would agree that I might be trying to bank it a little too much like an airplane, but I have been trying to do less of that (due to the concern with cyclic) and I have actually started trying to use more of the technique you are referring too. It has started happening almost naturally. I do try and use as little pedal as possible and try to use more of the natural torque of the aircraft to bring me around in the turns, while trying to stay in trim. I still feel a little awkward pulling up out of the field and bleeding off my airspeed , but I know it will only get more comfortable with time and practice. The last few jobs I have had, have had some wires so I am giving them a fairly wide berth and make more of a modified airplane ag turn to make sure I am safe coming in and out of that end. I am sure as time goes by I will become for comfortable with getting in and out of the field bordered by the wires, but I just don't want to rush myself and have a bad day.


Yes I have realized very quick that this airframe does like to weathervane and at times take a lot of pedal work to keep me facing the right way lol...


We use Tracmap and its pretty nice. I can set it up to fly just about any type of spray pattern and its super easy if I want to fly skip passes I can just bump the line to where I want it. Light bar and the coverage map make it nice to know how my swaths and coverage are coming out.


I spray basically everything and anything, lots of veggie row crops, cotton, corn, nuts, citrus...we kind of do it all depending on the time of year. Its still all new to me though, but its my dream job and I am having a blast...just want to be safe and make sure I am doing things properly.

[agpilot69]

Just wondering if anyone else has had any issues with left cyclic and side mounted spray tanks ?? 40 + years Ag helicopter experience.
Rigging, Crosstube plugging, plumbing,
Thanks

[GipsyMagpie]

already discussed? (http://www.pprune.org/rotorheads/567396-bell-oh-58-cyclic-issues.html#post9110135)

[agpilot69]

would like to hear from others spraying with side tanks on OH-58
Lateral cyclic issues ?

[agpilot69]

lightbar system allows you to do skip pass. i use it alot