Helicopter Maintenance Blog*
Posted 2 years 246 days ago ago by Scott Skola
Well, everyone should have got a reply to their email. If I missed yours, drop me another mail.
In the GOM, looks like one major operator will emerge from its CH 11 proceedings in August, and another one is in the middle of theirs. I wish all concerned the best of luck.
Heard the 2020 HeliExpo will be a month early: January 28-30. For those who plan to attend you may want to check out the latest info.
And it looks like the days of a viable single engine SPIFR helicopter are finally back. Leonardo and Bell recently completed FAA certification on the 119 and 407, respectively. While it was mainly driven by the new Navy trainer aircraft requirements, I can’t help but think other operations will also benefit like EMS.
In the history corner:
And away we go…
TIPS and TRICKS:
Finally leaving the engine compartment, we’ll next move up to the M/R hub and blades. And we will start right off with what most mechanics hate to deal with: M/R track and balance with the infamous RADS.
In all honesty, it’s not really that bad. And hopefully with a few tips you get here you’ll come away feeling like a Master RADS-ter!
But first some preliminary tips on 407 M/R track and balance. Stay away from factory zeroing all PC links and weights; even when replacing a complete M/R hub assembly. Unless you are replacing all four M/R blades, retaining the existing hub weights and PC link lengths can cut down on the time it takes to smooth out the M/R.
So when replacing a hub assembly, transfer all hub weights from the old hub to the new hub in their respective positions. Just be sure all your blade and PC link color coding is correct per the MM and intact before disassembly.
Even if replacing a blade or two, keep the PC links at their previous lengths and if you want you can measure and replicate the trim tab positions from old to new blade. However, tab moves tend to be blade specific. But who knows? However, if a replacement blade tends to go rogue during the process then zeroing the links and tabs may be required.
If you’re dealing with a flying M/R hub and blade assembly that has come up with a rough ride, don’t arbitrarily throw the RADS on and re-track and balance. Take some time and inspect the M/R components to include the main transmission pylon system.
There are a number of elastomeric components that when they separate/fail can de-tune the M/R ride. For example, a separated pylon corner mount can be a hidden gremlin and cause a number of issues. Plus a bad corner mount can also make it difficult to track out.
A couple prelim tips on the RADS itself. First, check all the RADS cables for damage. Better to find it now than later in the process. Unfortunately, this doesn’t guarantee a cable or accelerometer doesn’t go south during the track and balance process.
Next, install the RADS per the MM. Ensure your cable runs at the swashplate allow for full flight control movement, but are not too loose as to catch on something during aircraft ground runs and flights.
On the M/R blades, apply some flat black paint to the lower surface of the leading edge strip covering about four feet from the blade tip. This will help the RADS tracker “see” the blades better in the daylight. A little Naphtha will take it off once you’re done.
With everything installed and connected per the MM, power up the RADS. For all intents and purposes, RADS is just a very basic computer with very basic software. Think Windows 3.1 or DOS 6. So after multiples of runs it has a tendency to get full.
To fix this, delete any previous balance data if possible. Also, performing a hard reboot of the CADU prior to use can usually speed things up. And just as an FYI: a soft reboot can be used during balancing if things lock up or run slowly.
Tune in next month when we turn and burn and start the M/R ground (Initial) track and balance.
Here’s a couple Leonardo newsletters to make your day last longer: Winter 2019 and Spring 2019
SUBMITTING MAINTENANCE TIPS/TRICKS/QUESTIONS/INFO:
Have an old tip or trick you’d like to share with your fellow mechanics? Or maybe a question that you can’t seem to find an answer to? Or just some info to pass on? Send an email to: [email protected]
About the author:
After 32 years maintaining helicopters in various capacities, Scott concluded a full time career with a major operator in 2014. When not pursuing future writing projects, he can still be seen around the flight line tinkering on aircraft for beer money.
*To keep the hounds at bay, the information contained in this blog is for discussion purposes only.