Guest osprey5 Posted August 31, 2007 Share Posted August 31, 2007 Just a general question on whether other jab users turn off the main fuel valve. We don't and there's no point doing it now with the fear that others out of habit get caught out. However while reading something about the carburetor I noticed they said that the main needle valve isn't a fuel stop and any minute particles could prevent it from closing properly. I guess the result being you empty the fuel tank. Should we be closing this or isn't it that serious a problem. Link to comment Share on other sites More sharing options...
facthunter Posted August 31, 2007 Share Posted August 31, 2007 Fuel cock. osprey 5, There's a good argument for having a standard way of doing things, as surely if you don't, someone will make an assumption, will not check it and come undone. Most engine failures on take-off are as a result of incorrect tank selection, and the design of the actual selector sometimes doesn't help. The fuel available when the selector is off seems to be just enough to get you in the air, and it all goes quiet. The approved operating handbook. ( POH ) should be the decider. You can argue that any reasonable pilot should check it, but some don't. The Citabria POH says to leave the fuel turned ON ,so some makers trust the carburetter float valve to seal ,and the motor has been running on the assumption that it has the capacity to do that. If you turn the fuel OFF and it is non-standard procedure, a placard prominently placed, would be good airmanship, I feel. Nev.... Link to comment Share on other sites More sharing options...
rick-p Posted August 31, 2007 Share Posted August 31, 2007 one problem with all that gents is that when you need to turn off your fuel because of an emergency you can't because the tap or cock or whatever has either ceased up or the o rings are shot through non use and out of shape. food for thought.;) rick-p Link to comment Share on other sites More sharing options...
Guest osprey5 Posted September 1, 2007 Share Posted September 1, 2007 Thanks for the feedback. Good point rick-p about the valve failing through lack of use. I might start opening and shutting it during a pre-flight but I'll have to leave it on after shutting down as we don't normally touch it in our syndicate jab and I'd hate one of the other guys to have an engine out due to a change in our operating procedures. Mike. Link to comment Share on other sites More sharing options...
Guest J430 Posted September 1, 2007 Share Posted September 1, 2007 You have to ask yourself, which is the lessor of two eveils......spilled fuel or blood! We leave ours on except when changing the filter! And then its straight back on. BTW, any of you who can get airbourne on the remaining fuel after the valve is closed (cold start assumed) are needing a big clip under the ear! YOU DO NOT HAVE your oil temp up on that much fuel. Not a good thing! Most Jabs need about 10 min to warm up, and I am in a warmer spot than most! J Link to comment Share on other sites More sharing options...
Guest Decca Posted September 2, 2007 Share Posted September 2, 2007 Not unrelated to aero engines, but always left fuel cocks on small engines until I went to start our 13HP (Honda) GenSet one day & almost tore my hand off at the wrist pulling the start cord because the fuel leaking through the needle valve to the cylinder created a massive hydraulic lock. Not nice. Decca. Link to comment Share on other sites More sharing options...
blueline Posted September 2, 2007 Share Posted September 2, 2007 My vote is with Facthunter on this one as well - why set someone up for disaster! I can live with fuel spilt on the hangar floor but............ Link to comment Share on other sites More sharing options...
Guest JRMobile Posted September 2, 2007 Share Posted September 2, 2007 After every flight we top the tank up and shut the fuel valve off, start the engine and taxi back to the hanger, by the time we reach the hanger just running out of fuel (no way could we do our checks and get airborn!!!). The thinking behind this is that the full tank does not allow condensation, fuel in the bowl is fresh at every start ie no gums or residues if the jab has not been used for a time and we are not trusting the main needle valve as a tap for the 85 lts. Part of our preflight is " fuel valve on, main switch on, fuel pump on" etc Link to comment Share on other sites More sharing options...
facthunter Posted September 3, 2007 Share Posted September 3, 2007 Fuel starvation. My sources are GA aviation records. and believe me, aircraft DO manage to get airborne, with the fuel tap turned OFF. Whilst the Jab may run out of fuel with the tap off and SEALING, I would not as a principle accept that it will always do that, and thereby protect me. There has to be a guarantee that it is fully ON , however that is achieved, every time. I can also see that where you have 2 carbs. you have double the chance of one leaking. As a general rule, STICK BY THE BOOK, but if the book is observably wrong, get it changed. You don't want half of the people doing it one way and the other half doing it another, otherwise you just set people up....Nev... Link to comment Share on other sites More sharing options...
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