Winter Maintenance: Aircraft Hoses

On my trip to OSH this week for the Hall of Fame event I spent some time thinking about an appropriate topic for my first foray in AvBrief. When we left for OSH on Tuesday morning from Atlanta it was 25° Fahrenheit. It was a few degrees warmer in OSH, but not much. So, guess what popped into my head? Winter maintenance! Since our flying hours tend to substantially decrease in the winter months due to shortened daylight hours and adverse weather, I always recommend that aircraft owners take the time to review some longer-term maintenance issues, such as the hoses firewall forward, including the brake lines.

From what I see in the field, most of the aircraft hoses that have been installed are of the impregnated-rubber type, such as the Mil-6000 or even the Aeroquip stainless braided hoses such as the AE601 series. These hoses typically have a shelf life of 8–12 years, and a service life of about the same, even though they are treated as “on-condition” once installed. On-condition means to check them for wear, leakage, brittleness, etc. With age, I’ve seen them become very brittle and stiff. Why risk the airplane over a hose replacement? During cold-weather operations you will typically see much higher operating pressures at start-up, so hoses that may have been fine during the warmer summer months may now start to leak. BTW, for those of you running single-weight oils like Aeroshell 100, make sure you consider using a lighter weight such as Aeroshell 80 or even a multi-viscosity oil for winter operations.

Consider replacing all the oil lines and fuel lines with Teflon hoses, which will end the necessary replacement cycle as they should last forever. Of course, forever doesn’t mean you shouldn’t regularly check them and replace as necessary. It has been my experience so far that the Teflon hoses do take a “set shape” after they are installed and exposed to the heat of the engine compartment but do seem to hold up very well.

For Experimental/Amateur-Built aircraft, it’s easy to make the hoses yourself by procuring the components from places like Aircraft Spruce or even Summit Racing. There are plenty of YouTube videos showing you how to do them. There are also supply places like Brown and Miller Racing Solutions or Aircraft Specialty if you don’t feel comfortable doing them yourself. It should only cost you a few days downtime, perhaps a couple of Saturdays, but it will give you some peace of mind. I know it does for me! Be sure to perform a ground run prior to reinstalling the cowling to check for any leaks.

For those of you with certified aircraft, you are required to use certified hoses that meet FAA specifications to ensure safety and compliance with regulations.