Another Little Glitch Fixed: Sting S-LSA

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

Moderator: drseti

User avatar
drdehave
Posts: 356
Joined: Fri Apr 13, 2012 10:45 am
Location: Davis, CA

Another Little Glitch Fixed: Sting S-LSA

Postby drdehave » Sun Sep 18, 2016 8:27 pm

If you’ve been following this site, you know I love my 2007 Sting S-LSA. Why else would I have etched almost 2,000 hours into her Hobbs meter in just over 6 years (there’s a big celebration coming soon, when I actually hit the big number!)?

One of the most tangible benefits is speed. With the right prop, the Sting can blow by much of the S-LSA competition--and many standard aircraft, too. For example, just yesterday, two Piper PA-28 Cherokees traveling together took off in front of me from Willows, CA. All three of us were headed to Yolo County, CA. Within a few miles I was passing them with a ground speed of 122 knots to their 108 knots! That felt good!

Nevertheless, my year-class of the Sting has revealed some glitches and I call them out when I find them. Eighteen months ago I had to deal with delamination of the main, integral fuel tank. Before that, I reported that earlier Stings lacked the necessary “hard” idle stop on the throttle slide in the cockpit (newer Sting S4 planes have this glitch corrected, with an "adjustable" hard idle stop provided). Today, for the benefit of fellow earlier Sting owners, I want to report on a brake deficiency (and fix) in this airplane.

I’ve long known there was some sort of brake-system issue. I’ve had pads that wore out prematurely and unevenly, shuddering during hard braking (and turning), and the sound of discs and pads “dragging” at one point in wheel revolution during taxiing. Up to now, I attributed these issues to poor “fit and finish” of the brake-system components.

Then, a few weeks ago, we discovered the real culprit: The bracket welded to the axle and to which the brake caliper is bolted is inordinately weak and subject to bending. That’s a bent brake caliper bracket you see there in the picture; it is supposed to be perfectly straight and plumb 90 degrees to the axle.

And here’s the rub. You can’t really determine that it’s bent, when it’s hanging down there on the strut with everything bolted up tight. But remove that integral axle & bracket (releasing all the tension) and this (photo) is what you’ll find. Also, bending is most prevalent on the right side, which is most engaged in keeping the airplane straight against P-factor.

The solution was to straighten the brackets on an anvil and then weld on a 1" x 4" “stiffener.” Then we put everything back just as before. And I can tell you I now have the quietest and smoothest-functioning brakes I have ever had since purchasing this airplane in 2011 and I am no longer afraid to really “stand” on them!

We are currently in the process of memorializing the “fix” we made, via LOA from the manufacturer.
Attachments
20160817_120932 (1328 x 747).jpg
20160817_120932 (1328 x 747).jpg (188.82 KiB) Viewed 632 times
Sting Flight (Flying the Sting LSA)
http://www.youtube.com/user/9162069934/featured

Return to “Ask The Mechanic”

Who is online

Users browsing this forum: No registered users and 1 guest