Summary
- Modern engines can withstand severe weather due to robust construction & redundancy in critical systems.
- Rainwater rarely affects engine power output; the combustion process successfully converts it into steam.
- Jet engines are tested rigorously under various conditions, including taking rain, hail, and ice, to ensure flight safety.
The winter season brings several challenges to flight operations. Precipitation in the form of snow, hail, and freezing rain can impact ramp activities. However, modern engineering has allowed contemporary airliners to be robust and operate even under suboptimal conditions.
A key part of this comes from advancements in engine technology, which have allowed powerplants to operate under almost any condition. In this article, we will examine how precipitation affects today's turbofan engines.
Modern jet engines
- High-strength materials
- Engines' ability to withstand extreme temperatures
- Tested to ingest large amounts of water without failing
- Built with redundant ice-suppressing mechanisms
- Redundancy of critical sensors and systems
Aircraft are designed to withstand severe weather regularly while ensuring passenger safety. The sky's most common Jetliners, like the Boeing 737 and Airbus A320, frequently fly through storms and inclement conditions without experiencing engine power loss. While it may seem that the sudden or constant influx of water would decrease an engine's ability to output thrust, this is rarely the case.
Photo: Robin Guess | Shutterstock
As Simple Flying previously analyzed, today's turbofan engines operate using internal combustion. Low-pressure (LP) and high-pressure (HP) compressor blades draw air into the engine and toward the combustion chamber, where the air is mixed with fuel and exits as exhaust to propel the plane forward.
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Much of that air bypasses the central engine core and travels between the engine cowling and the combustion core. The bypassed air remains compressed as it exits, producing over half of the total engine's thrust while cooling the central core.
Extreme influx of water
Commercial aircraft are generally expected to encounter rain and other precipitation while on the ground and in flight. Jetliners consistently fly through thunderstorms, with engines inhaling large quantities of water rapidly while maintaining safe thrust levels.
The deluge of water, however, does not all pass through the engine's central core. The blades of the compressor catch the initial influx of water and spin it towards the outer walls of the engine with centrifugal force. This allows the water to bypass the air system and avoid contact with the combustion chamber in the engine core.
The rain is unlikely to disrupt the combustion process even on jet engines that do not feature bypass systems. The extraordinarily high temperature of the engine's combustion chamber, sometimes reaching 900 °C (1,650 °F), converts the incoming water into steam with little influence on the engine's power output.
Photo: Real_life_photo | Shutterstock
Water has sometimes been intentionally fed into jet engines before the dawn of afterburners. The increased mass being exhausted from the engine increases thrust at low speeds and aids engine cooling.
However, under certain extreme circ*mstances, immense rain and hail can affect aircraft operations, as reported by Aeroengine Safety. As a result, aircraft are always instructed to avoid severe conditions.
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Freezing rain and ice
Freezing rain and snow can be more problematic as they may cause ice to build up at the engine intake. If ice builds up around the engine intakes, chunks of it may break off and hit the engine fan. This could damage the fan blades and lead to a compressor stall. The intakes are heated to prevent ice from forming around them, so there is no risk of dislodged ice hitting the fan.
Hail can also be a concern when flying close to severe thunderstorms. The pellets of ice can damage the exterior of the aircraft in addition to the engine, and pilots are encouraged to avoid thunderstorms by at least twenty miles. An Emirates Boeing 777-300ER encountered severe hail upon departure from Milan Malpensa Airport in 2021. It returned after sustaining severe damage and shattered windshields.
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According to the National Weather Service, in freezing rain, freezing fog, or heavy snow, aircrews can shed any ice build-ups by intermittently running the engines. In the case of a loss of power due to ice or large amounts of water entering the combustion chamber, the pilot could then attempt to relight the engines or engage the automatic igniters safely, according to Aerospace Web.
Photo: KLM
Lightning is even less of a concern. The National Weather Service estimates a commercial jetliner is hit by lightning an average of once a year. Aircraft are engineered explicitly to withstand lightning strikes, and disruptions are infrequent.
While rain alone is unlikely to impact operations heavily, the same cannot be said for ice and thunderstorms. Air traffic control, maintenance teams, and aerospace regulators will carefully monitor engine ice and powerful storm cells to ensure safe flight operations.
Jet engines are comprehensively tested
- Wind-tunnel tests
- Computational Fluid Dynamics (CFD) simulations
- Ground (stationary) tests
- Ramp and taxi tests
- Flight tests
Jet engines are tested thoroughly to withstand severe storms safely. One of the many steps for aircraft certification involves flying in inclement weather, the preparation for which occurs on the ground. Engine manufacturers such as General Electric and Pratt & Whitney have state-of-the-art testing facilities to ensure the engines can handle heavy precipitation before leaving the ground.
Photo: Rolls-Royce
The engines are tested under various conditions, including introducing foreign objects to simulate a bird strike. In the case of General Electric's GEnx engines, giant hoses sprayed three tons of water a minute at the engine to check for any weaknesses before production, followed by one ton of manufactured hail.
Technological advancements in onboard weather radar can help aircrew avoid severe weather cells. The systems can detect large buildups of particles such as hail, rain, and ice crystals such as snowflakes.
Overall, aircraft engine flameouts due to precipitation remain infrequent compared to running out of fuel. A combination of centrifugal force, the speed at which air passes through the chamber, and the engine's heat all work together to prevent precipitation from flooding the engines.
