Originally Posted by
PEASACAKE
With all the balancing equipment on the market, and purchased by companies I worked for, there were so many issues with engineers (experienced) being able to carry out a simple track and balance that I had to get back to basics to find out why we were spending so much money on balancing equipment, and the more we spent, the longer it took to balance the machines.
With the old Chadwick 177m from the seventies it was simple, then came the other models and makes of equipment, many many times after days of balancing and adjustments I would rip the balance equipment off the aircraft, put the 177m on it and balance it in an hour or so. Plus nowadays helicopter service intervals are larger than they used to be, and engineers "forget" how to use equipment (including myself)
So after a significant amount of frustration it transpires that engineers are not being trained how to balance anymore, from basic training, type training, continuation training, its never covered. If you do not know what you are balancing, how you are balancing and why you are balancing there is not much chance of carrying out the task efficiently. I have been asked to visit customers who have had balance issues on helicopters, found things had been installed on MRH upside down, wrong way round, inside out, worn out, wrong places, list goes on.
How many times have I seen an engineer installing a balance kit on a helicopter due to customer saying " I have a vibration" without inspecting the helicopter first for wear or damage, it amazed me. Something must be causing the vibration, it was not there a 100 hours ago, what is it, adjusting pitch links, trim tabs and weights is not always the solution. The trim tab tool was always out, adjusting blade tabs, what, why, nothing on the blade has changed.
How many times have I seen an engineer plug the wrong leads into the sensors, mixing vertical with lateral readings, here goes a week of balancing.........
For many years I use to conduct "track and balance" training days for engineers, even experienced engineers, after the 1 day course an engineer could even draw his own basic vertical and lateral balance charts for all types of MRH and tail rotors, its so simple at basic levels. After the course the engineer had a clear understanding of what he was trying to achieve and passed his knowledge on the the younger engineers.
Now asking a pilot to take readings, no not really, unless its built into the helicopter. Its best an engineer takes the readings, relaxed, calm, and under no pressure to say it feels ok when it needs adjusting.
Agreed 100% PEASCAKE.
A lack of understanding of the basic theory is prevalent and many times engineers will be chasing a vibe issue by blindly following the process of adjustments given by the more modern equipment.
I much prefer a basic system that just provides a phase angle, track and Lat/Vert IPS.
It's pretty simple to work out manually after that.
177 is a bit old hat but there are newer digital systems that will provide the same basic information with much more accuracy especially track data. Just recently used Dynavibe on a MD500E and was very impressed with ease of use and data provide. First time I used the gear and first time T&B on a 500.
Work it out manually after that and think laterally (pun intended) what is causing the vibe. Apart from routine smoothing /post maintenance etc, vibes are often an indicator of failure of another component.
I will give a nod to AW139 Heliwise and HUMS though. For routine smoothing works very well to follow the suggested moves.
Training is the key and is glossed over usually in my experience when it comes to T&B. It's not a black art, just needs some thought and gets easier the more you do.
I don't recall ever been trained in T&B basic theory and I consider myself to be lucky to have been professionally trained by a major international operator over 25 years ago.
In hindsight it was the old hands who explained the basic theory OTJ and picking it up from there.