What is the Purpose of an Oil Breather?

Oil breathers are a necessary accessory for aircraft, commonly applied to a reciprocating internal combustion engine to prevent pressure from building within the crankcase. Contributed through heat generated by an engine rising to a temperature hot enough to vaporize oil, oil breathers are constructed to vent any hot air created within the system. Following the rising nature of hot air, oil breathers are affixed to the top of an engine for this reason. Accompanied by breather ventilation tubes, these components are often redirected to the bottom of your vehicle's engine cowling for optimal ventilation of excess heat. Within this blog, we will discuss the primary necessities of oil breathers, their necessary parts, and conditions to be wary of.

A part of the crankcase ventilation system, oil breathers contribute to the overall ventilation system assisting an engine. Before the 1960s, to dispose of these unwanted gases, aircraft directly released evaporated fuel through seals on the crankcase. To mitigate this issue, the 1960s concluded with the development of the road draught tube. The first crankcase ventilation system to be combined with a reciprocating engine, this system consists of a one-way tube alongside an intake manifold vacuum, providing an easy solution for ventilation of various gases. These gases, also referred to as “blow-by,” are then rerouted from the engine, through the oil breathers, and out to mingle with the atmosphere outside the aircraft.

Common in older model aircraft following the 1960s, aircraft constructed with air/oil separators during this generation were often predisposed to leakage during unfavorable weather conditions. Conditions that may be a cause for concern include prolonged exposure to condensation and/or frost. If left exposed to these elements, your aircraft is more likely to produce leakage from the cowling, breather tube, or both locations. Indicating that maintenance is imminent, to reduce the likelihood of part malfunction, one must regularly inspect oil breather tubes for potential blockages. Later affecting the engine and the oil breather if not properly maintained, evaporated oil that has left to cool outside a crankcase can collect and run down aircraft parts. Messy and inconvenient, though a small amount of oil around a breather tube is normal, dripping or pooling oil from any component is not. Luckily not as recurrent as compared to an oil leak, pilots must also be wary of the direction an oil breather is facing when preparing for flight. If left to face the direction of oncoming wind, breather tubes become flooded with wind, risking the pressurization of the crankcase by ram-air.

With the development of modern aircraft came the positive crankcase ventilation system (PCV). A successor to the prior road draught tube, a positive crankcase ventilation system sends gases created within the crankcase back to the combustion chamber. Helping to repeat the aforementioned cycle over again, this recycled air from the crankcase also serves to reduce emissions contributing to air pollution, making it a convenient tool for modern aircraft.

At Limitless Purchasing, to keep your vehicle up and running, we have all the necessary parts to fit your specific aircraft applications. As a dependable distributor of oil breathers, breather tubes, air separators, oil separators, crankcases, and their applicable parts, we invite you to browse our inventory for numerous aircraft components and their related aparatusses. Due to our quality control and export compliance, we operate with AS9120B, ISO 9001:2015, and FAA AC 00-56B certification and accreditation. If you would like to request a quote for your comparisons, you can submit an RFQ form as provided on our website. Upon receipt, a dedicated account manager will quickly review and respond with a personalized solution to your needs in just 15 minutes or less, 24/7x365.


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