gentlemen, where do I start...... we have sold about 500 of these fuel flow sensors over the years because they use to be supplied with the skydat instrument range when they were freely available. There are a number of really critical issues which you have identified. Firstly it is clearly written in the instructions not to blow through the device to hear the wheel spinning, even worse is using compressed air and if you pull unit apart is very difficult to get back together again without it failing because it is assembled in a controlled manner with special bearings which are almost impossible to see without magnification. So please be warned on all of these issues. I can see also that you are over tightening the hose clamps because of the distortion in the visible end of the fuel flow meter. Small hoses like this are not ideal candidates for traditional hose clamps and this is one of the reasons why the guts are falling out of your hoses. Hose clamps on small hoses do not have equal clamping pressure all the way around and this is what is causing some of the problem. You should be using this type of hose clamp on small diameter hoses and this is standard practice with a number of manufacturers like Mercedes, BMW etc. I don't know if these are deemed to be suitable for aviation but I have installed some on an old X-Air which has been flying for about 10 years without any issue although he did replace the fuel line at five years and fitted new clamps. Please do your own investigation on the suitability of these for factory built aircraft ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ the hose clamp shown below is used on a number of our factory built aircraft and if you look closely you can see that when crimped they support the complete diameter of the hose and this is what is required for small diameter hose because you lose a lot of crimping pressure under a standard hose clamp. These units must be connected with a special tool which can be purchased off eBay for around $15 and the claims themselves are not cheap at around three dollars each, they can be reused a couple of times without any problems but they will be damaged if you try to close the clamps with pointy nose pliers or side cutters. Hopefully a few others will jump in the conversation with a bit more experience and knowledge about hose clamp in small diameter tube but I can see from the distortion in a photograph of your fuel flow meter that there is a problem and you need to be careful because these units will crack and they need also to be away from heat source which means they are normally covered in fireproof sleeving unless in a really good airflow position. that's my $0.16 worth ! and my total knowledge of hose clamps
I don't believe this is a big cost if you take it over the life of the hose which I think is 5 years. I am a firm believer of doing it by the book. After all people like Rotax have a lot more experience than me with their engines. I have only had 2 of their engines, how many have they had experience with? Cheers Scotty
I was aware of the caveat against blowing through the fuel sensor, but it wasn't reliable anyway, so if my action had caused it to be less so.. no matter. The accuracy seemed to vary between 60%-80% of actual fuel consumption, depending on flow rate. An estimate based on engine run time was more accurate. Since blowing it through, I notice that it now reads a fuel flow rate when taxiing. Something that has hitherto read zero. It will be interesting to re-calibrate its readings against actual consumption again and see if it has become useful. I am using the clamps provided by the aircraft manufacturer and as it is a certified aircraft, I cannot change them to another type. I agree that they were previously clamped too tight. My issue, and rectified when I replaced the two hose sections. All other fuel lines were checked at the same time, both for over-tighening of clamps as well as clamp placement.
