Helicopter Maintenance Blog*
Posted 4 years 261 days ago ago by Scott Skola
Well, I guess we all survived another year. Thanks again for your readership.
Looks like the offshore rotorcraft industry hasn’t fared any better though. While the financials of most major players are continuing their slide, there’s new company acquisitions on one side and rumors of sell-offs on the other side.
The latest being Bristow’s acquisition of Columbia Helicopters. Should make 2019 an interesting year. My best to all affected.
And finally, in support of the light-hearted side of the blog, a new monthly mechanic’s comic with our beloved pilots as the guest foil—well at least most of the time. Look for it below.
In the history corner:
Now back to the 407…
TIPS and TRICKS:
Since we still are messing with the T/R drivetrain, here are a couple more tips on the T/R D/Ss.
On a regular basis, the oil cooler blower splines require lubrication. In order to comply with this lubrication, the forward and aft short shafts must be removed to allow access to both sets of splines on the blower assembly.
And as we learned last month, the orientation and indexing of the T/R D/Ss is crucial to maintaining the balance of the oil cooler blower. So when possible, it’s to our advantage to keep shaft disassembly to a minimum.
The trick here is to loosen the two bolts (Fig. blue) at the shaft/adapter end, which in turn creates a “hinge,” then remove the two bolts (Fig. green) at the opposite shaft end. By repositioning the unsecured end, the shaft assembly can then be slid off the splines with minimal disassembly. Note: in some installations, you may have to loosen (blue side) the disc-pack to adapter mount bolts instead of the shaft to disc-pack mount bolts to gain additional clearance.
But first, a couple more tips on indexing (Fig. red) the shafts. If there are existing indexes good for you. However, if the indexes are difficult to discern, or there are multiple marks at the same location, it’s to your benefit to remove those old marks and re-index.
Per the book, all shafts and adapters should be at 90 degrees to one another. Starting with the forward short shaft mount flange in the vertical position, index the 12 o’clock position on each shaft end, adapter, and spline from the engine to the #1 T/R D/S using an indelible marker. Sometimes indexing the drive spline can be fickle due to old grease and accessibility. A good cleaning of the index area and the use of paint marker pens can facilitate this task.
FYI, if performing this maintenance outdoors, the T/R could start to windmill depending on what shaft you have disconnected and the prevailing wind speeds. You may want to loosely secure the M/R and T/R blades. However, ensure you can still rotate the driveshafts through 360 degrees to facilitate shaft bolt removal/loosening.
While it should be intuitive on how to proceed further, here are some additional tips. And don’t forget to capture the disc-pack bevel washers (Fig. yellow) when you remove any bolts.
Forward Short Shaft Assembly: Loosen the aft two bolts at shaft/disc-pack/adapter attachment until the nuts are flush with the threads. Remove the forward two bolts at the shaft/disc-pack attachment (engine side). Slide the shaft assembly aft on the splines and drop the forward shaft end toward the engine pan. Once the shaft is clear of the engine, slide the assembly forward and off the blower splines.
Aft Short Shaft Assembly: Loosen the forward two bolts at shaft/disc-pack/adapter attachment until the nuts are flush with the threads. Remove the aft two bolts at the shaft/disc-pack attachment (#1 T/R D/S side). Slide the shaft assembly forward on the splines and move the aft shaft end away from the #1 T/R D/S. Once the shaft is clear, slide the assembly aft and off the blower splines.
To reinstall, just line up your index marks and slide the shaft assembly back on the splines and install/tighten the mount hardware as needed.
Couple more Airbus and Leonardo newsletters:
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.