Engine fires are extremely hazardous during flight, often posing various safety risks that makes mitigating the chance of such occurrences paramount. Engine fires can often occur from a variety of issues, the most common being a result of over-priming the engine. While engine fires can occur throughout the year if certain issues occur, the most common time for them to happen is during the fall season. While this can be surprising due to the cold conditions that the season brings, it is important that fliers are well aware of why hazards increase during the fall, and how to prevent dangerous fires.
As spring ends and fall rolls in, temperatures will often begin to drop. This will result in cold engine starts being more common, especially when flying during early hours. The gas that is combusted during aviation will often face decreased evaporation during cold conditions, thus making it harder to burn. Additionally, colder temperatures also cause engine oil to thicken, resulting in decreased movement throughout assemblies for facilitating operations. Lastly, the battery will also lose its ability to efficiently produce electrons, causing the starter to crank at a slower pace as there is less energy to take advantage of. With all of these issues coupled together, the aircraft can potentially face over-priming if one is not careful.
Priming refers to the process of spraying gasoline into a piston engine induction system for the means of starting it. During cold-starts, priming is often needed, and a common mistake that some pilots make is to provide too much gasoline to the engine for the means of overcoming the cold. This is what often leads to over-priming. During the priming process, fuel is implemented within the intake manifold in front of the intake valve, the valve chamber where fuel enters the cylinder, and the cylinder itself. For a proper engine start to be carried out, an optimal fuel-to-air ratio must be met, that of which typically follows a 15:1 ratio of air and fuel respectively. With too much fuel, the fuel-to-air ratio will be thrown off, resulting in a mixture that will have trouble igniting. Furthermore, excess fuel can begin entering the manifold or cylinder.
With too much fuel, mixtures will enter a liquified form, splashing around until it is combusted with a spark. This combusted fuel will exit the exhaust system and the intake fuel. The major issue is that if the ignited fuel enters the carburetor or fuel-injector assembly, the extreme heat can cause a burn-through which is very dangerous.
To prevent engine fires as a result of over-priming, one simply needs to ensure that they avoid adding too much fuel to the system. While not the most reliable methods of detection, overpriming will often lead to an increased smell of fuel, or the dripping of fuel if over-priming is extreme. If you happen to accidentally add too much fuel, you may follow special starting procedures to start the engine if over-priming is minimal at most. Otherwise, major over-priming requires fuel to be evaporated, and one may achieve this by opening the throttle to full so that air can enter the engine. To fully ensure that fuel has had proper time to evaporate, one should wait anywhere from 10 to 15 minutes before attempting a start.
While cold-starts can be difficult, it is never worth it to attempt adding an increased amount of fuel to gain more kick. Limitless Purchasing is a streamlined procurement platform for countless aviation components and other part types, offering customers access to over 2 billion new, used, obsolete, and hard-to-find items. Take the time to explore our vast set of offerings at your leisure, and our team is always on standby 24/7x365 to assist you throughout the purchasing process as necessary. If you have any questions or concerns regarding our offered components or services, give our team members a call or email at your earliest convenience, and we would be more than happy to assist you.
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