I write this not as an absolute answer, but in the hopes of provoking morally and financially sound thinking when we approach maintenance on our aircraft. Over the years I have seen many aircraft engines fail due to poor or omitted maintenance and the use of aftermarket parts. Such failures have caused at a minimum a loss of the engine, or a totaled aircraft and (too many times) people’s livelihood and/or their lives. Many aircraft are governed by rules and regulations from aviation authorities as certified aircraft and parts are more controlled, but many aircraft like Experimentals have a much more lax options for maintenance and parts. It’s in this area that I would like to provoke possibly life and property saving thought. Let’s state this right up front. You can be sued even for doing everything right and it will be expensive just to defend yourself, so why deviate down another path for a few dollars and add mounds of other liability to an already serious issue you could face.

Let’s take a look at this scenario. You have performed recent maintenance on your aircraft and thought you were doing a good job by replacing some older parts with newer ones. A friend said you could buy new rubber carb intake flanges from another company and save money over what Rotax rubber carb flanges cost. Sounded like a good idea. So you believe you’re doing good and getting rid of old hard rubber carb intake flanges. The new rubber flanges look the same, but didn’t come with new clamps - so you use the old ones which don’t have the 8mm spacer to keep from over tightening the clamp. The clamps are metal, so how could they go bad? You re-use the old clamps because you never read all the Service Bulletins or read the entire maintenance manual on the proper clamps so... Why not use the old clamps?  After all, new ones cost more money. You saved a total of $100 so it must have been worth it. The change out is now complete and you test fly your aircraft and everything seems fine. The next day you take a friend flying (a married father of three). Everything is good for a while but then suddenly the engine rpms fall off and the engine quits. You have to make an off-field landing over poor terrain. Things don’t go well. You’re injured and in the hospital and your friend is dead. If you don’t think these things happen, think again.

The investigation shows that one of the carbs fell out of its aftermarket rubber intake flange and that caused the engine to quit. Now the wife of your friend is going to file suit (friend or not), but you feel safe because you did things right - or did you? Legally under your local rules and regulations the use of that part may have been technically legal. That won’t stop the civil suit with you and the aftermarket company named. The wife’s lawyer will pull in four to six highly recognized and respected Rotax mechanics and/or parts specialists and ask them about Rotax parts, aftermarket parts and PROPER care and knowledge of your engine.  You won’t stand a chance. You have now spent $20+K trying to defend yourself for using an aftermarket part that really didn’t fit correctly (but your friend said it did). You didn’t know about the wrong rubber flange clamp, you didn’t read the Service Bulletin on aftermarket parts and you didn’t read that section on the carb intake flanges in the maintenance manuals. If you manage to get out from under this with only spending $20K for the lawyer - consider yourself extremely lucky. Because a judge or jury will most likely find you at least some percentage liable for using the wrong part and not knowing your engine and the dangers you imposed by that lack of knowledge and poor unacceptable “best maintenance practices” as recommended by the rest of the Rotax community.  This isn’t going to cost that friend or the guy on the forum that said the aftermarket flange was okay a single penny. Now look back at that $100 you saved. Was all this worth $100?  So what would you do if you could do it all over again and prevent this from happening?

I use this particular theoretical example because I just encountered a similar situation and thankfully, before any issues arose, replaced the flanges with proper Rotax parts. Aftermarket rubber flanges have caused numerous issues in the past that were not caught in time. This time a maintenance shop helping a friend used an aftermarket rubber carb intake flange and old clamps. I saw the plane a couple hours later. I was looking it over and the rubber carb flanges looked different and the owner was told by the shop that it had installed new ones. He just assumed they were Rotax parts. I put my finger against the carb and it fell out of its socket. I replaced these two rubber carb flanges with genuine Rotax parts.

( the real deal - Genuine ROTAX parts )

We tested the aftermarket flanges and they did not allow the carbs to securely snap in place nearly as well as the Rotax rubber intake flange does. The flanges were very soft when hot under the cowl whereas the Rotax part was not softened by the heat. The use of the old clamps without the 8mm spacer allowed the shop to over tighten the rubber socket, which in time likely would have caused the rubber to split and crack prematurely (another Rotax service bulletin not complied with - overlooked or ignored).

So in this case, my friend had to pay for rubber carb sockets twice and maintenance twice. Did he really save anything? If you had an incident like the fictitious one above - would the $100 saving be worth the risk of spending $20K to a million dollars in liability? Would it have been worth the cost of your plane if that was all that happened, would it be worth your injury or the death of a friend - or spouse?

Many times we mean well and try to do the right thing, but when money comes into play we may try shortcuts. Sometimes in life a failed shortcut is nothing more than that and we can try again without any real consequences, but sometimes we set ourselves up for severe unintended consequences even when we have good intentions. Flying and being hundreds or thousands of feet off the ground is not the place to put you or your friends in harm’s way for a few dollars. Flying is not an inexpensive sport and we as responsible owners are morally bound to ‘do the right thing’ and protect ourselves, our friends and our family from a poor choice - one which may end up costing us tens of thousands of dollars in liability and personal injury. Over the many years I have seen hundreds of thousands of dollars wasted by poor maintenance, omitted maintenance - or “bargain” aftermarket parts.  WHY? What did it save in the long run and what was the cost in the end...

There are aftermarket substitutes for other Rotax parts out there, but think long and hard before you start trotting down that path. There can be unforeseen, unpredictable and unintended consequences.

My spouse and friends are worth far more than a hundred or thousand dollars, how about yours?