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Why not set throttles higher than 1/2" during pre-start? PA-
One of the things I have noticed lately is when I set the right throttle to 1/2 to 1" before using the fuel pump, I get NO indication of fuel flow when the pump is turned on and the mixture is moved from idle cutoff to rich. I just run it about 6 seconds, then start. So, I again started the left engine as normal. This time with the the right engine I moved the throttle ahead about 2 inches instead of 1/2" , turned on the fuel pump, ran the mixture from idle cutoff to rich, and I began to see fuel flow. I moved the mixture back to idle cutoff, turned the fuel pump off, moved the throttle back to 1/2", and the engine easily started. It even idled better than before with the cleaned plugs!
The 1/2 " setting seems to be the proper one for idling on both engines once they are started.
My question is, could I even run the throttle wide open while having the pump on and running the mixture from idle cutoff, to rich until fuel flow noted, then back to idle cutoff, then turning off the fuel pump and moving the throttle back to 1/2" ? What exactly is the relationship between the throttle position and the fuel flow meter indication ?
Does the engine get "primed" as when a carbureted engine has some fuel sprayed into the throttle body or directly into cylinders (I think) or in our case is the injection system just pressurized so the injectors will instantly squirt into the cylinders while starting? I'm not sure I really understand how the system works.
Clear Skies,
Gomer
- Gomer Pound
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Re: Why not set throttles higher than 1/2" during pre-start?
Many years ago I was taught, and my start check list reflects - throttles, props, and mixtures full forward on prime with pump. How long to prime depends on experience, (and whether cold or hot start), then throttle back to about a 1/2" if cold, again depending on experience in your particular aircraft.
Best, Don
Don Nelson- ICS member
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Re: Why not set throttles higher than 1/2" during pre-start?
Zach Grant L1011jock- Technical Advisor
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