PPRuNe Forums - View Single Post - To Prime Or Not To Prime? That is the question!
Old 4th Nov 2003, 00:15
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IO540
 
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This thread has really shown the bizzare ways of engine starting... I bet a lot of them are unnecessary!

A question worth asking is whether priming is EVER needed. The engine ought to start eventually if cranked for long enough. I have certainly seen this "procedure" with fuel injected engines; it tends to start after a lot of cranking but no more cranking than the "textbook hot start procedure" normally requires.

Re a choke - if this (being simply a mixture enrichment) worked then the process of squirting liquid fuel into parts of the engine (which is what "priming" is) would not be required. (BTW I am NOT saying that squirting liquid fuel into parts of the engine IS required ) I don't think that a choke would help because the carb (or a fuel injection system) in an aircraft engine is already set up for a relatively (relatively to a car engine) rich cut, about 150F rich of peak with all 3 levers fully forward. Once an aircraft engine starts, there is normally no problem running it, so I don't think a "permanent" richer mixture would help.
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