407 track and balance (cross posted from the rotor heads forum)

[helofixer]

RADS versus Microvib or some other system?
We use the RADS for 407 M/R track and balance and I want to throw it in the river. Tail rotors are not a problem. Rotor smoothing after major hub work makes me want to kick the dog. Anyone have any sucess with using a different system other than RADS on Bell 407's? We are looking for any input. If its not tracker problems, or garbage solutions that do not make the vibration levels better, its interference from the Air Conditioner, the Garmin GPS, the Transponder, etc etc. Looking for your input.

Besides the 407's we also have 206L3, L4, B3, and do work on R22,R44, Enstrom 480B. Looking for a system that could handle all these helicopters.

[chopdoc]

Smoothing a 407 rotor head is really not that hard with the RADs. Been doing it for years. If you understand the basics of track and balance and the a few truths about the RADs (like it will lie to you, which is where understanding M/R track and balance comes in) then its actually easy.

Track first, always. Ground track & balance the best possible before flying. Never ever do what Bell tells you and zero everything out. If your vibration is a vertical then its a blade, a lateral is hub weights.

Tell the pilot to NOT hold the aircraft dead steady in a hover when tracking, let it drift a little. Every control input messes with the readings. Just dont crash :)

If everything is sweet all the way to 130KTS, and 130 and let down is a bit high, live with it. You can not expect new performance from older elastomerics. Get the best most acceptable ride where the aircraft will be flying the most. I seen hover, climbout, cruise be all below .2 and mostly .1 or less and letdown be a .4. to get the .4 in let down lowered screws up everything else. Gotta live with it.

Learn to use "view perdictables" and write down the current IPS and clock angle. Dont know how often people went right through the clock and then complained "it got worse". Also if its a vertical, turn off the balance section and recompute the best possible solution. It will surprise you.

Make an old track and balance chart and plot your moves so you know whats going on. This works for ALL tracking or balancing with the RADs. Especially with the fanshaft on the 407.

[arelvin]

I just want to include that if I do need to write i na paper all the balance history and sometime plot in the MM balance chart then I suggest to use the vibrex 2000 or Acces 2020 you can buy those 2 for the price of a RAD.

I do preffere the Acces because you can have vertical and lateral vibration at the same time, it save flight time.

[deHav8]

I have to wonder if the hub assembly on the 407 isn't a lot more sensitive to elastomer issues and bearing wear relative to others. Don't have experience with other rotors other than 206 so I don't know, but from what I've heard, the design of the 407 head makes it more of a challenge to track and balance. Anyone else with some perspective on this?

[deHav8]

The Honeywell ZTE is a pc based system that is supposed to replace the rads (similar set-up to the VXP). Uses the same script files from Bell. Also has a certain degree of inter-operability with Chadwick components i.e. Fastrack, etc. Anyone have any experience with it? Would be interesting to know about it's capability in comparison to the RADs.

With the RADs, you can do things like adjust three pitch links and two or three tabs at once, and thus be done in 3 - 5 flights instead of 7 -9. Try doing that with other balancers.

[Saint Jack]

Chopdoc has got it essentially right, if you're having difficulty getting a smooth helicopter then look for other causes - sloppy flight controls are top of this list. Also as Chopdoc said "....it (RADS) will lie to you" so don't put aside your common sense during the smoothing procedure. Finally, don't fall into the very common trap of terminating the smoothing procedure when you reach the 'acceptable' figure - keep going and get it as low as possible.

[deHav8]

That's great if you have the time, but if you have a limited window due to crew availability, etc. then compromise is needed.

[Saint Jack]

deHav8: Point taken, however I can't help feeling that if you're having limited resources (crew availability) and means (time) to do this important work why are you doing it at all? Stand your ground, compromise is NOT needed, if possible explain to them how important this procedure is. If you're working for a company that doesn't or won't appreciate the customer appeal of a truly smooth helicopter or the fact that this leads to greatly reduced wear and tear on the airframe and components (i.e. cost of operation), then - with great respect - it may be time to look for a more enlightened employer.

[deHav8]

Yes, more enlightened indeed. That gave me a chuckle - if you only knew who I work for haha. We as an organization specialize in minimums if you know what I mean. Good jobs are very hard to find; good employers almost impossible.

[wrench1]

Helo.

A few more bits:

Lot of great tips here, and yes, RADS can be a bear at times. But it works with a little tweak or two. As for microvib and the others I’m not a big fan. I had high hopes for micro as a couple of the vib engineers from chadwick started it after Honeywell bought chad. I also own an aces 2020 that I use for plank wing prop work only. All good tools but don’t care for the interfaces.

If Honeywell has come out with a truly portable system, as mentioned by dehav, that uses the same software as vxp, then that would be the ticket. But if it is another plug/play with onboard hums then I’ll stick to vxp, RADS and an old chadwick 177.

Not sure what you mean by “major hub work” but I’ll add a few more tips to the list here. And maybe a few duplicates.

If “major work” is actually a hub assy replacement then don’t zero links, plus put weight/blades back on same color hub arms. If you’re changing individual hub parts in a field environment then there are too many variables to explain in this post. Anytime you install hub be sure to retq after first ground run. Then retq it after first flight. MAX tq and use a tq multiplier. Hub shift can ruin a day.

Before start, power up Rads, clear memory and other acft files if possible. I believe Rads, aces, micro all run under basic dos or windows 3.1. It doesn’t have a lot of volatile memory.

As stated track first. If daytime, make sure blade bottom leading edges have fresh coat of black paint or whatever, but black. I’ve never had great success using system at night on ground. If needed, turn off weight and tabs on RADS. Use a bit of pitch on ground to load the M/R during grd track.

When finished turn on weight /tabs and completed ground work with same bit of pitch. As stated monitor clock/ips and plot on chart if need. RADS does not “learn” weight sensitivities. Also, it does not correct the clock after first run. These two issues are root cause of most troubles (plus the fact rads shoots for 0.0 ips on every run). Example, Rads calls for 10g weight that sends move line through zero. You cut it in half and it works. Cut all wt moves in half thereafter, but continue to monitor. No different than old 177. On the clock correction not much to do except follow Rads moves on a paper chart that you corrected.

BUT you need to follow the first 3 Rads solutions--exactly--to see how it is “reading” that aircraft on that specific day/time/weather BEFORE you start reading between the Rads lines (with experience you can wean off this requirement). In general, Rads will compute solutions based on how the requested track/bal moves react on system. If you short a weight move or don't adj a p/c link, and don't modify rads and re-compute, then you have just created a problem. In some cases an unrecoverable problem after additional runs and have to start over. If rads calls for a 1/8th flat or .0001g then common sense should prevail.

If readings are erratic and not following common sense start swapping velometers/cables.

As for your “…interference from the Air Conditioner, the Garmin GPS, the Transponder, etc etc”. You have problems as these should never affect rads, especially the gps. Without any details I can’t tell you where to look, but this is not an internal rads issue.

If still have issues, check the standard items that could be worn, loose, separated. Bell books give you a list. On 407 sep xsmn corner mounts can be a hidden gremlin. Check plot of M/R readings to see if you have a blade moving out from the group. You can play musical blades on the hub to try and make it work. Check blade P/Ns, TT and match them up. If you have the -117 (I think) TB mod’d blades then you have a product balance option in track/balance.

RADS is not magic, but it will get the job done. Though it is a bit overkill on 206, Robbies, etc. And as stated rads is the only one, save for vxp and the like, that can make multiple moves at once and finish up in 3-5 flights. I unfortunately had the pleasure of learning rads partly on 412s with the 100 series(?) blades, in which I too wanted to throw it in the river. Good luck.

W1

[Helohammer]

Chadwick vxp is very good for the blower shaft and tail rotor on the 407 (can be done in three runs apparently), but their main rotor app is next to useless - it cannot learn or adapt after a run.

Will be interesting to see if the honeywell zing is as good as the RADs.

[Steve Boyer]

Looking for the coefficients for the main rotor pitch link. Working on a manual test file and having trouble locating them.