BLOGmaster1234Helicopter Maintenance Blog*
Posted 3 years 68 days ago ago by Scott Skola
Last year for my August blog topic I discussed tool FOD. And the same for this August. However, this time I found some examples that drive the point home. Of all the things we can do as mechanics, when working on aircraft, is to ensure we, as a group, return all our tools back to their respective toolboxes.
As you read this blog, I will be diligently replying to your emails sent over the past couple months. I really do appreciate the input.
For this month we’re back to the 407.
TIPS and TRICKS:
Since we left off at the tailboom mount junction, I normally continue my daily inspection up to the oil cooler deck area. A couple areas of note.
The oil cooler and blower assembly is similar to the 206 series. The blower has been redesigned and cooler is bigger. However, the 407 does suffer from a higher instance of cracks in this area with the forward deck skin and the underlying support angles leading the list.
There have been several reasons behind these cracks, but even after a few different modifications the blower deck still cracks. Originally, there was a flywheel (Fig. 1, Item 5) mounted on the forward short shaft (T/R D/S) at the aft engine compartment firewall. Some people pointed to the flywheel as the culprit. However, after the flywheel was removed by Bell and “incorporated” into the rotorbrake disc in front of the engine, the cracks still persisted.
Another area that was susceptible to cracks was the aft firewall itself. In some case, it appeared to crack overnight. One of the latest modifications adds support rods to the cooler assembly that seems to have reduced the number of cracks.
And just like the T/R D/S fairings, the Aft Fairing assembly (doghouse) can wear at the Dzus mount holes and drop onto the aft fuselage skin, chafing the panel. The issue here is the skin panel is carbon fiber and has critical repair limits. A definite important area to watch.
One final tip. The oil cooler fins tend to clog over time from the engine exhaust--more so than a 206. Personally, I believe it’s from the rotorwash driving more exhaust residue over the cooler versus the tailboom. As easy way to mitigate any rise in engine oil temperatures is to flush the cooler with an engine compressor soap on a regular basis or as part of a scheduled engine wash.
A couple maintenance related accident reports:
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.