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Firebolt Builders/Owners Beware

Jwilsonphoto

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Good Evening Everyone,

This probably could have been lumped under the landing gear threads, but it's too important to be lost in there. I just came from my hangar and a day of trying to trouble shoot and cure my Firebolt's gear problems.

For those of you who aren't familiar with my earlier replies to our member's gear questions, here's a little background. A year or so ago, while doing an annual, I discovered a problem at the longeron hinge points on both main gear legs. The .065 tubes that the gear pivots on were slightly bowed and the collars attached to the longerons were cracking, as were the gussets on the .095 gear legs where the pivot tube passes through the gear itself.

Something that's important to share, is that I'm a 2,000 + hour tailwheel pilot, 1,000+ in the Skybolt/Firebolt, the balance in Cubs, T-6, and a host of conventional gear aircraft. Additionally, I am the only one who has flown this aircraft for it's 278 hours TT, and it's never been dropped in or beat up.

I removed the gear, consulted a number of knowledgeable Skybolt/Firebolt builders, even one of the gentleman who pioneered the cantilevered gear on the design. After careful consideration, I removed both gear, drilled out the pivot tubes, replaced the longeron hinge tubes and welded new, larger gussets on the gear legs where the pivot tubes pass through. Since the gear repair, all done with TIG welding, the airplane has exhibit uncharacteristically twitchy handling, but that is a side issue.

This afternoon, I was inspecting the gear and gear truss, and found serious cracks in several places in the weld clusters of the truss and longerons around the truss. Upon closer analysis, in the 20 hours since my gear repair and beef up of the gear pivot gussets, it appears that I only moved the stresses to another weak spot in the cantilevered gear design. It's also important for everyone to know that this fuselage was built by George Evans, partner and pioneer with Mac McKenzie on improving the original Skybolt design. This gear is not "new and improved", just new and a real problem waiting in the wings I'm afraid. If my Bolt had been a trainer, amateur built to a lesser standard, I could make excuses for the impending gear failure, but none of those factors apply.

I am really at a loss at this point. One course of action I'll research is seeing if it's feasible to replace the Firebolt truss and gear with the current taller Skybolt gear as manufactured by Steen Aero. On the Skybolt , one of the gear attach points is also the attach point for a set of flying wires. I need to figure out if that makes a difference, or if I can keep my independent flying wire attach fitting.

Believe me, I'm not trying to bad mouth the Firebolt, I loved it's tight cowl and trim gear from the moment I first saw it. At this moment, not so much! This is going to be a huge amount of work no matter which way I decide to go.

Sincerely,

Jim WIlson
 

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