I mentioned in the last post that after getting the wheel pants on Betty, the airplane was ALMOST ready to fly. The reason it wasn’t fully ready was during the wheel pant installation I removed the cowl. When I removed the cowl, I found this floating around inside the bottom cowl.
When I initially found it, I couldn’t figure out where it was from. So I set it aside, and knew that I was going to have to figure out where it was from. After thinking about it on and off for a few days, the type of aluminum and shape reminded me of the oil cooler attach flanges. Sure enough, the forward upper oil cooler flange had cracked through.
It certainly didn’t do all of that in the last flight. So this problem serves as a reminder to spend more time and be more thorough inspecting. With the forward flange cracked, the oil cooler found a new “home.” The new place the oil cooler wanted to be was about 1/8″ off the top forward mounting location. This said to us that there was some slight misalignment in the mounting bracketry for the oil cooler. This placed the flanges under pre-load. The flanges are very soft aluminum and when under pre-load are prone to cracking.
After consulting with Greg, Pacific Oil Coolers, and a few other folks, the plan for the fix was to eliminate the pre-load and also to add cross tube supports between then flanges of the oil cooler. These cross tubes make each pair of flanges a unit and will prevent the flanges from “working” under vibration and engine operation. To eliminate the pre-load we added a spacer in the mounting brackets that took up the 1/8″ gap. The spacer is made out of baffle seal material (silicone) and has some give. Hopefully this will also provide some vibration isolation.
With Oshkosh coming up quickly, I decided to buy a new oil cooler to expedite Betty’s return to the air. Then I would send in the broken one and have Pacific Oil Coolers repair the flange. This way I have a spare, and if the fix proves successful, I can either use the repaired oil cooler on my next airplane, or sell it. Then again, having spare parts is always nice too… I have to note that Wayne at Pacific Oil Cooler really treated me well for all of this. After all, the problem was my fault, but they went out of their way. Terrific customer service.
The oil cooler installation will be a watch item over now. It will require more frequent inspection to verify that we have appropriately fixed the misalignment and that the flanges are no longer prone to cracking.