Single barbed fitting offer a much better leak proofing but will require safety wiring as the retention effect of a single barb will be lower ( in other words, high number of bars = more retention effects = less leak proofing ). Use proper the barbed fittings on the suction side of the pump.Chose ones that are suitable for the tube size selected, to ensure that all the tubes are tight on the fittings.It is extremely risky to use Tygon tubes on these fittings as the walls risk to collapse under vacuum at the fitting opening and create an air leak. Tygon tubes are way too soft for this purpose. In any case it is extremely important to understand that push-to connect fittings are designed to be used with Shore A60 or above tubes ( Shore D40 or above ). If you are not sure of the tube/fitting combination, then use standard barbed fittings instead. Poor quality/ soft tubes with poor diameter tolerance can lead to air leaking from the fitting. It is important to ensure that the push-on fittings are being used with the proper tubes with proper wall stiffness and outer diameter. Their fittings resist corrosion for a lot longer than other brands. Use MIL spec push-to-connect fittings on the pressure side of the fuel: Pisco is a superior brands.There are a few very simple rules to follow to avoid air leaks:
The use of an air trap should help in avoiding these bubbles to reach the engine to a certain extend, but the best cure is prevention. Therefore, if the fuel system components are not leak proof, air bubbles could find their way into the fuel lines. This segment of the fuel system is being put under vacuum. The fuel system upstream of the fuel pump is subject to to the pump suction. This is a factor 37 and you can imagine that the system requirements and sizing will be quite different on each sides of this scale. This is clearly a function of the engine size and type and typically ranges from 80 ml/min for the latest micro turbines to 3000 ml/min for the biggest 1300 N thrust powerplants.
#BEST RC FUEL PUMP FULL#
The most important point that you should understand when planning for the fuel system is the maximum fuel flow your engine will need at full thrust In-flight fuel tank video from Oli Ni on Vimeo.įollowing the guidance given below will allow you to properly design, plan and setup your fuel system and will certainly help you in avoiding a rapid or regular decrease in the powerplant reliability. During this 30 second sequence, one can see that the fuel clunk is out of the liquid for exactly 50% of the time, pickup up air instead of fuel during this period! This video is taken on board an aerobatic plane. Here is a video example illustrating the fact. Although it is heavy and mounted on a semi flexible line to stay in the fuel as much as possible, there will be situations when it will get out of the fuel and suck air! This will happen towards the end of the flight, as the tanks get mostly empty and/ or while performing aerobatics. The main reason why air would get into your fuel line is because the fuel tank clunk is not a perfect system. Air leak is very unlikely if the system is setup properly. The air bubble syndrome comes from two main causes: air pickup or cavitation. Most of the engines available on the market are very intolerant to air bubbles and would flame out without notice if some were to appear in the lines downstream the air trap.
The biggest two issues that we can have on our fuel systems are air pickup and cavitation bubbles.
The first step in the process of building a good jet fuel system is to correctly size the components and set it up according to the plane requirements. You’ll find in this article a summary of all the accumulated data and experience. I have posted several articles on the RCU jets forum and RCJI in the past about this matter and collected a significant number of feedback from users of different systems as well as from my own experience after 25 years flying jet models. Thirdly, a bad fuel system could lead to a destructive on board fire in case of a leak close to the engine tailpipe or of a fuel pump runaway.
Not monitoring the fuel system performance with time will once again lead to a significant degradation of the powerplant reliability. Secondly the fuel system will evolve with time and need some specific on condition servicing. A system could work at the limit in summer conditions with good quality fuel, then generate cavitation in cold OAT, low pressure and/or with lower quality fuel. I have witnessed a countless number of engine shut down due to a too small air trap buffer capacity or cavitation bubble generation. The fuel system is one of the most critical component of our model jets for several reasons.įirstly a badly setup fuel system will directly affect the reliability of the engines.