Joined by propulsion manager Ian McDonald, I went along to the Heathrow hangar to watch our engineers change the Rolls Royce Trent 500 engine on an Airbus A340-600.
Our Heathrow hangar sits on the south side of the airfield away from the hustle and bustle of the terminals. Here our engineers carry out the heavier maintenance work, checks and repairs on our aircraft. This includes routine but highly specialised work such as engine changes.
Being replaced that day was engine number one (engines are numbered left to right facing the front) on G-VBUG, otherwise known as Lady Bird. From start to finish, the entire process can take up to 24 hours, and was a truly eye-opening experience. Here are ten things I learned watching the process:
Jet engines are both simple and incredibly complex. The basic principle of the engine is ‘suck, squeeze, bang, blow’. Air is pulled into the engine by the giant fans at the front and then compressed before fuel is added and ignited. Finally , it exits at high speed propelling the aircraft forward. It may sound straightforward, but it is anything but easy to achieve.
The engine is lifted by a single point hoist. This clever bit of kit is quite unusual and not available for many aircraft types. It saves our hangar team several hours each time they have to change an engine which helps our operations stay on time. When suspended from the hangar ceiling it looked like a giant multi-coloured mobile. Something that wouldn’t look out of place at Tate Modern. Powered by a ceiling crane that covers the whole hangar, you can see the wing flex upwards as the hoist takes the weight of the engine (at 00:29 in the video). Using the hoist requires some very skilful crane work to position and move the engine safely.
Aircraft engines have a wet and a dry side. This makes perfect sense. An engine has feeds for fuel, oil, air and electrics. Going into the ‘wet’ side are all the fuel and oil feeds and piping. The other ‘dry’ half contains all the air, electrical and flight monitoring equipment.
Design by engineering can be every bit as pleasing as design by – well, designers. There is so much design elegance to be found in an aircraft engine, yet none of it is built with aesthetics in mind. The sweeping curve of the huge main fan blades are a good example, as is the giant engine casing cast from a solid piece of titanium. There’s loads of interesting textures and shapes to be found. It may sometimes look chaotic, but it’s all exceptionally ordered and functional.
Engine bolts. I was looking forward to seeing the actual bolts that secured the engine to the wing spar. Many hours after the job was started, after everything else had been disconnected, I was surprised when the bolts were finally prised free. I mean, they’re very nice bolts. I just thought they’d either be bigger or there would be more of them.
This is nothing like working on a car. It owes more to surgery than mechanics. A combination of meticulous planning and an immaculate, brightly lit working environment ensured our highly trained team operated at the top of their game. I don’t think there was any doubt when it was time to start the engine for tests that it would all work as it should. It did. The aircraft flew to New York that afternoon.
There’s something called an ‘integrated drive generator’ (IDG) in the heart of the engine, which is connected to the gearbox and converts the shaft power of the engine into constant frequency electrical power. The four IDGs on an A340 provide more than enough power to meet all the aircraft’s electrical power requirements in flight. This is an expensive component, and therefore we remove it from the off-coming engine and then install it on to the on-going engine. There is very little access to remove the generator, so it takes a lot of skill to ensure that both the generator and the engine aren’t damaged.
Working in the hangar is quite physical. There was a lot of climbing, lifting and stretching to get to hard to reach places. Those engine bolts took a fair bit of moving too.
Everything is top quality. This is to be expected on an aircraft engine, especially given the cost. Every single wire, bolt, clamp or washer is made from the very best materials and is exquisitely designed. The harder you look, the more you see it.
Our engineers are brilliant. This won’t come as a surprise to anyone who works at Virgin Atlantic, but it was great to witness their professionalism, teamwork, problem-solving skills and dedication first-hand. Three separate shifts worked on this engine change, and at least two of the engineers I spoke to came through our apprenticeship scheme.
Top facts about Rolls-Royce aero engines:
- Like all Rolls-Royce gas turbine engines the Trent is named after a British river. Other Rolls-Royce jet engine names include Avon, Derwent and Conway. It’s said they were named this way because, like a river, the engines deliver a steady flow of power.
- The front fan diameter of the Trent XWB (the engine we will see arrive with the A350 in 2019) at just under 10ft is wider than the fuselage of Concorde
- The High-pressure turbine blades in the heart of the engine each generate around 900 horsepower, equivalent to an F1 car
- The force on a fan blade at take-off is equivalent to almost 1000 tonnes, same as a freight train hanging from each blade
- Engines are checked visually after every flight to make sure there isn’t any damage that could have been caused by foreign object ingestion or bird strike etc. Also, we are checking for any leaks, fuel or oil. More detailed inspections are carried out on the engines when the Aircraft is on an A-Check in the hangar (roughly every 1000 flight hours).
- The main piece of equipment that is used on the Trent 500 that you will have seen in the video is the single point lifter. This is a large piece of kit with arms that can reach under the cowlings and remove the engine from the pylon without having to attach lots of heavy lifting equipment to the engine itself. The single point lifter can be operated by just one person on the crane
- The dry weight of the Trent 500 for our A340 aircraft is 5 tonnes