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Cessna 172S Induction Overboard Drain Line

Asked by: 826 views Aircraft Systems, Commercial Pilot, Flight Instructor, General Aviation, Private Pilot, Student Pilot

Hi everyone,

I was going through the C172S fuel systems, and as most of you might have noticed, the line running down the firewall called 'induction overboard drain line' which from the text book explains as follow :-

"~prevent any fuel from the fuel/air control unit from settling in the induction system when the pilot over primes the engine, an overboard drain line redirects fuel from the induction elbow back towards the firewall,"

"~this arrangement is made so as to avoid a potential fire with the close proximity of the exhaust stack."


I would like to know how fuel comes out of the fuel/air control unit, drops down through the drain line, and lastly, how fire could result if this was not installed on Cessna 172S.

The book explanation itself is insufficient to understand in detail.



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