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ROTORwrench…Tips, Tricks, and Info - May 2018

Posted 4 years 88 days ago ago by Scott Skola

Helicopter Maintenance Blog* 
May 2018

The latest on the Bell 525 is a 2019 delivery date. However, with the offshore industry saturated with existing aircraft, a Bell spokesman stated it plans for a “soft” service debut. It will be interesting how the old school pilots will take to the fly-by-wire controls in every day operations. Definitely something to keep an eye on.

In other news, the final report for the EC225 accident in Norway two years ago is due out this month. If you recall, the M/R assembly separated from the aircraft in-flight when the main transmission case/epicyclic failed. 

This report may be the most anticipated in recent industry history. Whether it will bring back the EC to its previous leading status still remains to be seen.

I’m also starting to prep for this year’s Alaska trip. If you have any questions or info you like to send in be sure I receive it by end of May.

And now we return to our regularly scheduled program on the Bell 407…

ATA 05 
Maintenance Checks

The 407 tailboom had its share of growing pains--just like its older siblings the 206B and 206L. Cracks at the horizontal stabilizer opening and T/R D/S fairing mount clips were the big issues, but have since been mitigated for the most part through the use of liquid shimming techniques and the introduction of different full chord-wise fairing clips. However, these are still areas to monitor daily.

One important item to keep in mind, once the horizontal stab has been liquid shimmed and installed, the stabilizer and its associated upper and lower support plates are now considered an assembly. If you replace one support plate it will need to be reshimmed. And the same goes for the leading edge slats to the stabilizer.

Another area to watch is the inner surfaces of the vertical finlets (winglets). They are of honeycomb construction with very thin skin material. So thin that if you bump the skin with a wash brush the resulting dent is usually out of limits. If operating in an area that requires daily washing, it is recommended to wash the horizontal stab assembly by hand with a rag.

Also keep in mind, if ever complying with a pre-buy on a 407, damage to the finlets should be checked for limits and any repair or replacement of the finlet be negotiated in the sale price as the cost is not cheap.

We’ll finish this month’s tips at the tailboom mount ring. Just as the 206 series, the 407 tailboom mount rings cracked too. There were several upgrades to the ring shim pads and mount hardware to include stronger bolts and higher torques. So it’s important you know the current modification level of your aircraft when installing or replacing the tailboom.

And for those who work on land-bound 407s: if you ever remove the tailboom access panel to find a rubberized bladder mounted to an aft fuselage bulkhead that also seals around the T/R control tube and wonder what it is… it’s part of the emergency float system. Sometimes it’s easier to leave it in when removing the floats for installation of standard landing gear. Its purpose is to seal the tailboom which then becomes the aft float assembly.


A couple FAA SAIBs:



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.