Tail Rotor Balancing

[crop duster]

Just bought an Acess 2020 balancing unit to do props and rotor-tail rotors. How many of you have had anything to do with balancing the main or tail rotors? What I'm looking for is:
1. How many runs does it normally take?
2. How big a differnce did it make?
3. Does your company own a balancer or do you pay someone to do it?
4. If your paying, what does it usually cost to have it done?
5. How often do you do it?
We have been paying someone $350 USD to do our props since 1991. We usually balance every 300-400 hours on our crop dusters. When we had the B47 we just guessed the best we could. There is no one in the area doing helicopters. I'm anxious (but scared to death) to do the first tail rotor. The manual sounds very complicated. Sure would appreciate some insight.
Thanks,
barryb

[HeliEng]

crop duster,

Here goes (these are for tail rotor not for props):

1. You would usually expect to be close after about 3 runs. This depends on the condition of the bearings in the hub.

2. This is a bit subjective really. It will extend the life of your tail rotor components or prevent premature failure, but it is always very hard to prove.

3. We have our own balancing equipment

4. See Q.3

5. Every 100 hours or Annual Inspection.

A Bell 47 tail rotor is not a complicated thing to balance. I am not familar with the equipment that you have, but follow the procedure step by step, and it does work quite effectively.

Please PM me if you need any further advice!

Good Luck!!! :ok::ok::ok:

[quichemech]

With regard to item 2, it's not very subjective, it makes a grear difference to the wear and tear on a tail rotor system, the same as it does on a main rotor system.

Quite simply, the lower the vibraton level the longer things like bearings will last. Try to bring levels as low as possible, it all makes a difference.

[HeliEng]

Quichemech

Now try proving that to a pilot!! As you know full well, it makes no discernible difference from the cockpit so as I stated it extends the life of the components and prevents premature failure.


(Now awaiting onslaught from defensive pilots!!!)

[Arm out the window]

Not being defensive at all, HeliEng, but you can feel some tail rotor or drive shaft vibes through the pedals, particularly when something's on the way out.

[NickLappos]

Some TR balance points from my perspective:

1) Most balance gear is easy to use, and you just have to follow the directions.

2) Most issues with attempts to balance where the balance never gets close (you chase it all around) are due to bad gear or badly mounted accelerometers. The manufacturer is usually very helpful via phone.

3) Any balancing is better than none.

4) Balancing is probably not especially important for blade components and bearings, but is very important for shaft, gearbox and supporting structures because the imbalance forces are 'felt" especially by them. This means mount bolts, skin near the TR and TGB seals and bearings, lads.

5) Even if the pilot can't feel it, it could be bad for the helo. Some helos have cockpits that are insensitive to TR 1/rev

6) Balance only affects 1/rev vibrations, and does nothing for higher frequencies.

[bellsux]

I think the point that helieng is trying to make is that you can always fine tune it below the minimum acceptable (T/R normally 0.2ips) with extra runs but do you do it at the cost of fuel/cycles/manhours opposed to extra life on the components. The AS350 has a TRDS balance limit of 0.8 ips as a minimum limit but it is quite easy to get it down to 0.2 ips or better.

You are right about being able to feel vibrations through your pedals but you wouldn't be able to tell the difference between 0.3 ips and 0.1 ips.

Back to the original question, the 2020 is a good piece of kit and it will talk you through the setup and balancing process but if I were you I would have someone show you through it the first time and also explain why the equipment is telling you to add weights at those points. Also no matter what equipment you use you will need a very accurate set of scales, the digital ones with an accuracy of 1/10th of a gram are the best. Ask your local crack dealer who sells them in your neighborhood.

[crop duster]

Thanks guys. The unit I bought http://www.acessystems.com/2020.htm is very user friendly if you understand where to go in the menu. What scares me is the the polar charts and all the stuff that goes with interpreting the info after doing the data runs. The manufacturer is sending a tech guy down this week to work with me so hopefully I'll have a better handle on it.

Helieng and Bellsux, I may contact you from time to time once I get started on my first tail rotor.

barryb

[mickinst]

For some really thorough explanations on the subject, have a look at www.rwas.com.au.
Best of luck

[chuckolamofola]

Some other points to consider if things don't go well after the first run:

1. Ensure the accelerometer is pointing in the correct direction.
2. Ensure the accelerometer is connected to the proper input channel of the system being used.
3. Ensure you have properly identified the blade ID.

The above issues are the traps most people experience most often with most portable systems.

Most likely, a gram scale in one gram increments will work well for a B47 as you aren't adding wieght at the blade tips.
Best of luck

[Pan Pan Splash]

Most important tips I can give you:

1. Do exactly as the equipment tells you, not what you think should be right.

2. Make sure you add/subtract weight from the correct positions.

3. Take your time, slow and methodical is the key.

4. Make sure your setup of the equipment and also the running speed of the rotors is correct and consistent. If you are going to be a few % over the running speed on run 1, then be a few % over on all the runs.

And finally, don't get hung up on number of runs, I've made a career out of helo vibration and I can assure you, some aircraft will balance in a couple of runs, others can take longer. Its the end result that counts. As long as what you do is methodical and progressive then stick at it.

The 2020 will easily give you vibes of sub- 0.2 i.p.s.

If you are using one ACES downloadable scriptfiles, then make sure its the exact one for your helicopter type and model.

Again, you can always pm me if you run into trouble.

PPS