Main Double Valve

by Sefa Tak in 912iS Technical Questions 6 years ago

Hello,

I'am a mechanical enginnering student, and we are trying to made a very light aircraft. We are planning to buy a 912 is. However, in fuel system we have a question about double main valve. Figure is taken from the 912 installation manual. Could you explain how does the main valve work?
Thanks a lot.

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Re: Main Double Valve

by Richard Boslaugh » 6 years ago

Richard Boslaugh

9 122 84

Picture the valve as two valves stacked on top of each other with a common control shaft. When the operator selects the upper fuel tank the system is as shown. The additional ports on that valve are for the unused fuel return line shown leaving the fuel pressure regulator, going through the upper valve and back to the upper tank. The diagram shows the lower tank output port being blocked at the lower valve. When the control valve is turned to the lower tank its fuel is routed to the pump assembly and the return line fuel is now routed to the lower tank . It is a FAA regulation that on CERTIFIED aircraft any return fuel must go back to the tank it came from. The check valve in the return line is a safety measure. In the event that the valve had a fault and did not properly route the return fuel the check valve will ensure the fuel gets back to a tank. The 912iS pumps can deliver as much as three time the volume of fuel that the engine consumes, so it has to go somewhere. The resident expert mechanics on the forum will step in and correct any bad statement I have made in this discussion as I am not a serious mechanic or engineering expert.

Thank you said by: Sefa Tak, Bill Hertzel

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Re: Main Double Valve

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.98k

What he Said!
Well Stated Neville!

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Main Double Valve

by Richard Boslaugh » 6 years ago

Richard Boslaugh

9 122 84

Bill, I re-read my post and find it a little confusing. I should have stated in the begining that the upper valve controls the flow of return fuel and the lower valve controls the flow of fuel tank output. Thanks for being easy on me.

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Main Double Valve

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