Helicopter Maintenance Blog*
Posted 3 years 107 days ago ago by Scott Skola
August is the time for reflecting on some real-life maintenance issues. The last couple years I focused on tool FOD. This year the examples highlight maintenance errors on B-nut torqueing, following MM instructions, and the dreaded “unknown.”
Sometimes the simplest of tasks cause the greatest of errors. And unfortunately are usually the easiest to prevent. Read the reports below and make some mental notes so you won’t be caught in the same predicament.
On a better note, I should have made it back to civilization by now and I am currently working to answer all your emails. Thanks again for your support.
In the history corner:
TIPS and TRICKS:
In keeping with the engine compartment, here a few miscellaneous tips.
Anytime you need to remove the 407 external fuel filter assembly from the firewall or the filter housing from its mount, loosen/remove the “inlet” and “outlet” fuel line B-nuts. If you don’t, the fuel line, usually the “outlet” side, will kink at the nearest Adel clamp. And after several episodes the line will become permanently kinked. This type damage has been documented as the cause in several engine flameouts.
Bell requires the use of Stabilant 22 on all engine FADEC cannon plug connections. Take it one step further and use it on all aircraft cannon plug connections. It’s one of the closest “mechanic-in-a-can” you can run across when dealing with electrical issues. I’ve even seen it used with other OEM aircraft products with outstanding success. In other words, the stuff really works!
One item to keep a close eye on, especially in salt-laden environments, is the engine anti-ice solenoid. It is highly susceptible to corrosion and contamination. Spray the outside housing with Corrosion X or similar product regularly and “exercise” the solenoid during each engine rinse or wash drying run. Verify the TOT rises when the valve is turned on and falls when anti-ice system is turned off. And don’t forget some Stabilant 22 on the cannon plug.
If you still have MS screws securing the engine bellmouth seal and the aft edge of the intake cowl screen /shelf to the forward firewall, look into replacing the screws with AN stainless steel bolts. Nothing beats bolts over screws especially in tight and confined areas like the backside of the forward firewall. And it’s usually considered a minor alteration to boot.
When changing a starter/generator sometimes the rubber pad for the ST/GEN duct is glued to the generator itself. If you have limited shop supplies, one option is to swap out the original aft screen housing with the replacement ST/GEN housing. However, the best option is to glue that rubber pad to the duct instead. Just don’t forget to slit the rubber at each duct mount “finger.”
When changing an engine bleed air valve it is highly recommended to replace the three mount bolts as well. They tend to rust and wear out at the bolt internal drive area--which if left to their demise will snap off in the engine scroll at the most inopportune times. And don’t forget to use liberal amounts of anti-seize lube during installation.
Speaking of installations, prior to installing the engine mount pads onto the engine gearbox apply a layer of yellow Masitnox. The steel alloy of the mount pad does not play well with the magnesium alloy of engine gearbox. There are other products that may do, but from an anti-corrosion side, where you need to remove that item in the future, there’s none better than my personal favorite, yellow Mastinox.
And let’s finish off with a few newsletters: Robbie Winter 2019 and Airbus Rotor 114
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.