How Jet Engines Handle Rain and Hail While Flying

Any nervous flyer, or even sometimes newbie flyers, might think that rain can cause an engine to flame out or stop working during flight. Of course, we all know jet engines are designed to suck in air, but not rain, right? Well, actually, jet engines are designed to be able not just to ingest air, but even heavy rain and hail. Hence, rain, in fact, will not affect the jet engines during mid-flight. So, there is nothing for you to worry about when an aircraft operates during a heavy downpour. In fact, pilots are more concerned about visibility rather than the engines flaming out.

Jet engines are designed to handle a wide range of environmental conditions, including rain. The fundamental operation of a jet engine involves air compression by fan blades, fuel mixing in the combustion chamber, ignition, and exhaust gas expulsion for thrust. A key aspect of jet engines is their ability to manage significant water ingestion. Most of the water that enters a jet engine is spun out by the fan blades and flows through the bypass duct, which is the space between the engine core and the cowling.

The bypass air, which does not enter the combustion chamber, contributes additional thrust and cools the engine core. Consequently, only a minor fraction of the water reaches the combustion chamber, where it is rapidly vaporized due to the high temperatures.

High Temperatures and Pressure in Combustion Chambers

The combustion chamber of a jet engine can reach temperatures up to 900 °C (1,650 °F), far exceeding the boiling point of water. Therefore, any water entering the combustion chamber is instantly turned into steam, which has a negligible impact on the combustion process. Additionally, the high pressure within the combustion chamber prevents water from condensing or freezing on engine components.

Jet engines must adhere to stringent standards and regulations regarding water ingestion. These standards are established through extensive testing and simulation, including exposure to artificial rain and ice during the certification process. Jet engines are required to demonstrate safe and reliable operation under such conditions.

Jet engines are equipped with features to prevent or minimize the effects of water ingestion. These include heated intakes, anti-icing systems, water separators, and drain valves. These features help prevent ice formation, water accumulation, and corrosion within the engine, ensuring its continued efficient operation.

The Rarity of Flameouts and Precipitation Impact

The biggest danger posed by precipitation, such as rain, snow, ice, or fog, is the potential for an engine flameout. A flameout occurs when engine power is lost not due to mechanical failure but due to the absence of fuel, air, or a heat source. Flameouts are rare, occurring only about once in every 100,000 non-military flights.

Precipitation is an unlikely cause of flameouts. Most storms produce light rain or snow with minimal impact on engine function. Clouds, composed of small ice crystals, also have no significant effect. Only very intense storms might affect engine behavior, but aircraft typically avoid such storms due to turbulence rather than engine performance concerns. In strong storms, the main consequence for jet engines is a reduction in combustion efficiency due to altered fuel-air ratios caused by water vapor presence.

Last but not least, jet engines are thoroughly tested before being installed on planes. Engineers and engine manufacturers don’t just expose the engines to heavy amounts of rain or precipitation; they also test them with hail. They fire bird carcasses into the engines to simulate a bird strike. Hence, there is nothing for you to worry about when it rains. Engines are very well-designed to ingest a heavy amount of rain during flight.