How to test a jet engine

Think of the last long-haul flight you took. You may have caught up with some sleep, enjoyed a drink, or got stuck into the in-flight entertainment. You probably didn’t think once about the engines.

But around you, you may have been travelling through different time zones, over sand, or sea, or snow, or even through a storm. Aeroplanes travel through extreme conditions every day, and as well as being efficient, quiet and reliable, our engines, which power almost half of all widebody (i.e.larger) aircraft, are equipped to handle anything the weather throws at them.

To do this we test them to the extremes, pushing them to the limits physically and digitally at our state-of-the-art test sites around the world. If you’ve ever wondered just how we test our jet engines, read on.

We subject them to freezing conditions

We subject them to freezing conditions

While your only temperature problem in the cabin might be the over-active air conditioning, outside, at 40,000 feet, the mercury can drop to as low as -60 degrees Celsius. In freezing conditions, ice can form on the front of the engine. It’s designed so that at a certain point, the ice safely breaks away before it can cause any damage that might affect the engine’s operation.

We take our engines to the GLACIER facility in Manitoba, Northern Canada, and put them through a range of tests to push our designs to the limit. We also start the engine in freezing temperatures, when the oil in the engine becomes thicker than treacle. The Northern Lights are often visible at the facility, but teams can’t sit back and enjoy the view – during testing they take regular indoor breaks to regulate their body temperature.

We drench them to the core

Planes take off, land and fly through rain and storms every day; it’s part and parcel of flying. Engines are well equipped for this, from April showers to monsoon season. However, in extreme conditions, such as hailstorms creating melting balls of ice, water can get into the engine’s core, which risks putting out the flame that keeps it alight. We design our engines to prevent this happening, and conduct water ingestion tests, where we drench the core of an engine to make sure it can withstand and continue to operate in the most extreme conditions it is likely to meet in service.

We ask them to run, and run, and run…

We put our engines through gruelling endurance marathons, making sure they can handle powering intensive, ultra-long-range routes, day after day. The Trent XWB powers the longest flight in the world, from Newark to Singapore, typically an 18-hour flight which experiences a range of different weather conditions. As the next frontier of aviation is reached and airlines operate ultra-long-haul flights, we continue to test the limits of the Trent XWB. It recently undertook endurance tests in Thailand to monitor how its components behave. We simulated the equivalent of more than 1,000 ultra-long-range flights, back to back. Now that deserves a medal.

We subject them to gale-force winds

Crosswinds can blow fiercely across an aircraft’s direction of travel, making it difficult to take off and land. In addition, the turbulence created by crosswinds can cause fan blades to vibrate, which can be damaging. While pilots are highly trained to manoeuvre an aircraft through strong crosswinds, we need to make sure our engines can manage the impact of this air moving across the front of the engine and continue to operate safely. We take our engines to Stennis, a test site on the John C Stennis Space Centre in Mississippi, USA, and blast simulated crosswinds across it, measuring its ability to withstand the strongest of gusts.

We measure noise to a fraction of a decibel

Aircraft today are perceptibly quieter than 20 years ago, and alongside the wider aviation industry we’re working towards environmental goals that will see us reduce noise by 65% by 2050 relative to 20 years ago. New and improved technology means that engines such as the Trent 1000 and Trent XWB are quieter than ever before. This is better for local residents around airports, and there’s an added bonus for passengers in the cabin, who enjoy near silence on board the newest aircraft.

As you’d expect, there are tough regulations on aircraft noise, so we meticulously measure the sound our engines make. We head to Stennis, where incredibly sensitive microphones are placed around the engine test bed and can detect changes in noise of a fraction of a decibel from the engine operating from low power to maximum power. The engine intake is fitted with what looks like a giant golf ball, to ensure that ground air turbulence doesn’t affect the engine noise.

We put them through the ultimate test

Engines are incredible feats of engineering, able to withstand the world’s harshest conditions. One of the marvels of modern flight is that if one engine needs to be shut down, aircraft can operate using one engine, allowing it to divert to a nearby airport. We continue to design our engines so that they can withstand rare occurrences such as bird strikes, or if an engine’s fan blade were to be released, which is extremely rare, our engines are designed to contain the debris within the fan case, avoiding damage to the aircraft. During flight, this means the pilot can safely shut the engine down, continuing to the nearest airport.

We take them to the skies

We take them to the skies

We conduct many of our tests on the ground, whether that’s in Germany, Manitoba, or among the swamp lands in Mississippi. In these locations, we’re able to simulate conditions in a controlled environment. But we also test our engines during flight, on our flying testbed. Based in Tucson, Arizona, flight test engineers put our engines through their paces on a converted Boeing 747-200. It’s particularly useful for new product development, allowing us to test new technology in the sky and monitor how it behaves.

But as we develop our next generation of engines, we need a next-generation testbed. We’re converting a Boeing 747-400, which spent 20 years in commercial service with Qantas into a second flying testbed for our next generation of civil and business aviation engines.

The new flying testbed will allow us to test our engines at higher altitudes and faster speeds than ever before. It will obtain enormous amounts of data, enabling test pilots and engineers to validate technology informed by our most extensive data set ever.

Looking to the future

We’re pushing our testing to the next level as we work on creating the cleanest, most-efficient forms of power in the world, that are more digitally connected than ever before.

While we’ll continue to test engines physically, we’re harnessing digital technology and gathering incredible levels of data, allowing us to predict how an engine will behave throughout its lifetime by using digital twins. We already successfully simulate tests such as the “fan blade off” test using this kind of technology.

We’re investing heavily; our newest testbed will open in Derby, UK in 2020 and will be the biggest and smartest of its kind in the world. But our ultimate goal will be the same: to create the cleanest, most efficient forms of power, that from take-off to landing you don’t think once about.