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ROTORwrench…Tips, Tricks, and Info - March 2018

Posted 6 years 36 days ago ago by Scott Skola

Helicopter Maintenance Blog* 
March 2018

After years of speculation, a new study released during Heli-Expo has confirmed there will be a shortage of helicopter mechanics over the next 18 years. I don’t know if that means “experienced” mechanics or just a head count, but with stated numbers of over 40,000 mechanics, now might be a time to brush off your resume.

I can remember when I first started hanging around helicopters there was talk of a shortage. But I guess with increases in helicopter numbers, Baby Boomer retirements, and a slow movement to the plank-wing side again the shortage has finally materialized.

Could be a prime opportunity to advance for those mechanics who have 5+ years of experience. Good luck!


We’re back to the 407 for this month’s tip. 

Three… Two… One…

ATA 05 
Maintenance Checks

Picking up where we left off at the vertical fin, we’ll look at the T/R G/B fairing and T/R D/S covers.

The hardware securing the T/R G/B fairing has a tendency to loosen. It’s always a good practice to check this hardware during the daily. Ensure the correct washers are used as these will maintain a larger contact area than regular AN washers. Due to the composite construction of the fairing, any loose hardware will expedite enlargement of the fairing mount holes by chafing.

The fairing is also not very conducive to visually checking the T/R G/B oil level. Throw in a “smokey” oil level sight-glass and it can be a challenge. The oil level can only be seen through the aft cooling screen on the upper fairing. And depending on exterior paint color, ambient light, and other factors, the cooling screen itself can limit how much light enters or obscure your vision via a “screen door effect.” 

Two tricks. If your hands are small enough and you use a small flashlight, you can slide the light down through the upper fairing access door and apply the light directly on the sight-glass. Or, simply modify the screen using a Uni-bit drill and enlarge one of the center screen holes out the next row of holes (Fig 1 Red). You’ll be surprised how a single ½” hole enlightens your view.

Just like with the anti-collision light, the aft position light (tail light) has more than its share of problems. Most issues can be isolated to the OEM connector which can also be replaced with a Whelen connecter should the need arise. A good practice prior to installing the upper fairing is to function check the tail light as it always seems once you have the fairings completely installed the light doesn’t work.

Also, apply a little preventative maintenance juice every now and then to the tail light mount and hardware. It makes for a long night when a neglected light mount needs to have its bulb changed. 

One final tip on the fairing. Without fail, maintain the chafe tape at the interface surfaces between the fairings and the tailboom. The fairings will win every time over the tailboom skin.

Moving forward, the T/R D/S covers are pretty straight forward except they too have an appetite for eating tailbooms. The Camlock studs/grommets installed in the covers will chafe their mount areas enlarging the hole. This in turn allows the cover to drop and contact the tailboom skin. 

The Maintenance Manual calls for a constant .020” gap between the lower cover edge and the tailboom skin. Since nothing wears uniformly, one corner of a cover can drop unnoticed and chafe the skin. To combat this possibility, some operators fabricate and install metal “J” straps (Fig 2 Red) on the forward and aft Camlock receptacle clips (Fig 2, #5) for each cover.

The “J” strap is located in such a manner to maintain the required .020” gap plus provides a secure shelf for the cover to sit on. It’s not 100% Murphy proof as it is still possible to install the cover with the edge outside the “J” strap. But it is a step in the right direction.  

Received an email last month inquiring if all STCs require an FAA Form 337 to be completed. The quick answer is no. 

From the maintenance side, when looking at aircraft alterations the first step is to determine whether the task fits the definition of a major or minor alteration. If the alteration called out by the STC is considered a major then a Form 337 and approved data is required. However, if the STC alteration is considered a minor then a simple logbook entry and acceptable data is required.

Some of the confusion exists in how an STC is labeled and defined. An STC like a TC, PMA, or TSOA is a manufacture/design approval process and is required when an alteration is considered a major change to the type certificate (TC). A major change to TC and a major alteration to an aircraft are not the same thing.

A major alteration is defined in Part 1.1 and exemplified in Part 43 Appendix A. Neither FAR contains any reference that a part’s design approval determines a major alteration or that all STCs are considered major alterations.  

Additional confusion is created when the part manufacturer elects to, or is required to, use the STC process for an alteration that would not be considered a major alteration per the Part 1 or 43. There are a number of reasons for this, but in order for a person to sell a part to the public for use on a TC’d aircraft that part must be FAA approved. And an STC is one method to approve that part.

An easier way to think of it, the STC is the part design process and the major/minor alteration process is the part installation process. Both connected but under separate requirements: Part 21 for the design and Part 43 for the installation.

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.