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ROTORwrench…Tips, Tricks, and Info - April 2018

Posted 6 years 46 days ago ago by Scott Skola

This past February brought a change to a long time helicopter manufacturer. Bell Helicopters is now simply called Bell and they have a new logo:

Not sure if I like the new look or name. But then again I’m a little on the old-school side of things. 

There were also a number of notable accidents in the past months. The tour industry took several hits and an EC135 went in the water in Australia. While they all appear to be operations sided, it never hurts to regroup and ensure we are minding our Ps and Qs on the maintenance side. And here is one example that drives it home: http://aerossurance.com/helicopters/lax-maintenance-honolulu-b206/

It’s that time again… The Lama-Nator!


ATA 56 
Tail Rotor
Airbus (Sud Aviation)
SA315B Lama
SA316 Alouette III

At the end of the Artouste rear bearing tip, I promised to speak of backwards tail rotor blades. 

Rather distressing, that the tail rotor blades could be installed backwards on the tail rotor head spindle/housing. The manufacturer tried to Murphy-proof it, as there is one of four attach bolts that is close tolerance and a corresponding hole in the tail rotor blade cuff that matches and makes it difficult to install the blades in any other orientation.

Notice I said “difficult” and not “impossible.” You have to force the blade on backwards on the spindle, possibly dead-blowing it at the tip, which is fortunately flat, or draw the blade up with the nuts. 

The problem is more in getting an incorrectly installed blade removed, there is only one place to tap on it, and this area at the airfoil root end, consists of two plastic end caps that will shatter if you aren’t careful. Or, you can get the blade started and pry it away from the spindle/housing and trash not just the Teflon gasket, but likely the spindle or blade root attach surfaces. 

Backwards means installed facing the wrong direction of rotation. Don’t worry, you can’t fly it like that, all the excitement occurs during run-up. Just FYI, for things to get to this point, the installer had to not research text nor graphics, and not notice that the blades were installed backwards, nor did they notice that when the main rotor blades were rotated, the tail rotor rotated backwards, trailing edge first. 

Upon first run-up, on the first few revolutions, the blades knife into the air, flap to the inboard and strike the tailboom, damaging the blades and possibly the tailboom. 

In another instance, the installer put the Lama tail rotor blades on the spindle/housing backwards, thought they were just facing the wrong way, and spun them around on the pitch change bearings so the blades faced correctly. But then he noticed that the pitch horn was not aligned with the pitch change spider arms for hooking up the pitch change rods. So he moved the spider to correspond with the pitch horns and installed the pc links and proceeded to attempt a run-up for balance. 

With the pitch change occurring from the trailing edge side (Fig 2) instead of the lead edge side (Fig 1), the tail rotor controls (pedals) were backwards, so that left was right and right was left. Also the geometry is disturbed and neutral pedals is not flat pitch. As RPM increased the helicopter started to yaw and the pilot corrected, but since everything was backwards, he only unwittingly aggravated the problem and the aircraft spun around on the tarmac. Luckily they were just far enough from a building structure.

Again, FYI, the installer obviously did not research text nor graphics to determine if his assembly was correct before run-up. He caught that the blades were facing the wrong way, but instead of removing them and re-installing correctly, he thought he installed them correctly but “somehow” the pitch horn was not aligned with the pitch change spider, so he moved the spider. 

TIP: if you are not going to read the manual, at least look at the pictures.

Newsletters from Airbus and Leonardo/Agusta-Westland 


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.