Engine test cell: Welcome to the 'temple of thrust'
The airline’s new multimillion-dollar “engine test cell” building — located at its Atlanta global headquarters — centers around a gigantic testing room that helps technicians maintain the powerful machines that push airplanes through the air, carrying millions of passengers every year.
Places like these are key to the goal of making airline jet engines work perfectly all the time — every time.
Last week, Delta invited me to visit the new building to see how it’s designed to put today’s engines through their paces, as well as the super-powerful engines of the future.
Inside the 48-foot-high room technicians let me stand a few dozen feet away from a powerful 8-ton Rolls-Royce Trent XWB turbofan jet engine while they fired it up.
‘Like a hurricane of your worst nightmares’
Imagine holding a giant bathroom scale up against the blast while the engine was at take-off thrust. That imaginary scale would register a weight of 85,000 pounds.
So, while we waited for technicians in a nearby control room to crank this behemoth, you could say there was a bit of nervous excitement.
As it stirred to life, the engine hummed … and then coughed out a little puff of atomized jet fuel.
Then, I felt a vibration move through the room, making the hair standup on the back of my neck.
Next, a whirring wall of sound grew into an overwhelming mechanical roar. Talking was useless.
Despite all this, the engine was just idling — creating only about 3,000 pounds of thrust — nowhere close to full power. Safety is always a priority here, and no one is ever allowed in the room during unsafe conditions — especially with an engine blasting at full thrust. It “would probably be like a hurricane of your worst nightmares,” said Mike Moore, Delta’s senior vice president of operations, inventory and logistics.
A Rolls-Royce Trent XWB turbofan jet engine hangs above Delta’s new test cell in Atlanta.
48-foot-high doors and a ‘blast basket’
And let’s not forget the doors. Make no mistake, we’re talking about massive doors here.
Technicians roll the engines into the test cell through a set of double doors made of solid concrete that are 26 feet wide and tower 48 feet above us. Each door weighs more than 300,000 pounds.
So huge are these doors that they’re controlled from a special box that pushes them open and shut with the touch of a few buttons. Why so big? The doors have to be able to hold up to the extreme levels of air pressure that can occur during testing.
Delta had “to build a facility robust enough to be able to take the negative pressures the engine is building on the front — and to be able to take the pressure — the thrust — on the backside of the engine,” said Don Mitacek, Delta’s senior vice president for technical operations.
There are other amazing design features inside this building — like the “exhaust stack.”
Basically, it’s a room that gets rid of engine exhaust. When you’re running huge jet engines all day, you have to send all the exhaust somewhere.
“Exhaust gases reach upwards of 800-900 degrees Celsius (1472-1652 degrees Fahrenheit) inside the engine,” said Dustin Thames, Delta’s principle engineer for engine testing and performance.
The engine pumps that super-hot exhaust into a huge circular tunnel built into the wall — which leads to a special chamber where the gases are released into a giant cylindrical cooling device called a “blast basket.”
The room design serves to calm down “the violence of the air,” Thames said.
Vents in the blast basket disperse the engine exhaust throughout the room — eventually rising though a network of sound-absorbing “bar silencers” before exiting the building through an open roof.
Flooring the engine
Delta and all other airlines are required to keep their fleets safe through regular maintenance checks and the replacement of key parts at specific intervals. A big part of that process includes making sure the engines — and their tens of thousands of parts — are ready to fly thousands of miles over mountains and oceans without breaking down.
“A typical engine when it goes through the rebuild process is in the shop anywhere from 60-90 days,” Moore said. “The engine is completely disassembled. All the parts are inspected and everything’s reassembled and then it has to come to this facility to be tested.”
Obviously, the preventative engine maintenance process can never be perfect. But perfection is the goal. Engines fail on very rare occasions and airline crews are highly trained to deal with those situations.
“The overall safety picture has dramatically improved in the last 10 years. And a lot of this we owe to some of the technology that goes into the equipment — engines being one of them,” said Mark Millam, technical vice president at the Flight Safety Foundation, an independent global nonprofit focused on aviation safety.
Technicians inside the control room put a jet engine through its paces.
What happens, for example, when a twin-engine jet aborts a landing attempt and then loses power in one engine? The other engine has to quickly increase its thrust. Technicians demonstrated that for us inside the test cell control room.
We watched them put the Trent XWB through a so-called “snap acceleration” — the equivalent to flooring it when you’re behind the wheel of a car.
A shiny thrust control handle in the control room is pushed forward to maximum, and in just a few seconds, the engine revs up to high power — more than 85,000 pounds of thrust.
The technicians monitor the engine’s oil pressure, temperature, how fast it’s turning and other factors — on alert in case anything looks out of whack.
“When you run an engine, it’s really like an orchestra. Everyone has got their part to play and everybody’s got to come in at the right time,” Moore said. They’re making sure everything is “working in harmony to produce thrust at the given settings that they’re supposed to produce.”
The testing phase after repair or overhaul adds a layer of safety. “Just the fact that you have one more resource to go to in terms of how you service the engines and get maintenance and repairs performed just makes it that much more viable to use that equipment,” said Millam. “The more you have these high-reliability devices in operations, the better it is for safety for everyone.”
Future of flight
The new test facility is part of Delta TechOps, Delta’s separate maintenance, repair and overhaul division which serves the Delta fleet as well as other airlines. The division also has maintenance contracts with jet engine manufacturers Rolls-Royce and Pratt & Whitney.
It all points toward a future that includes more passengers and more powerful engines, Moore said. “When you look at aviation around the world over the course of the next decade or two decades. It’s nothing but growth, especially around the engine space.”
In fact, the facility is designed to handle engines that are so powerful, they haven’t been developed yet — up to 150,000 pounds of thrust.
“We believe in the near future there will be engines that will require that type of thrust,” Mitacek said, including “engines for supersonic jets.”
During the quest to stay ahead of the curve, Delta says safety remains the priority.
“In this facility, [safety is] just one piece of the puzzle connecting all the work we do to that final engine assembly,” said Mitacek. “And we know when it leaves here, that it’s going to be safe and reliable.”