A pair of NASA research projects to gather data on aircraft noise and test an air traffic management digital data communications tool are flying aboard a Boeing 787 this week as part of the Chicago-based company’s 2020 ecoDemonstrator program.
Results from these flights will help continuing development of technology to enable future aircraft designs and flight operations that will be quieter, more fuel efficient, and result in fewer delays.
“That’s what our productive partnership with Boeing in these ecoDemonstrator series of flights is all about – making future air travel safer and cleaner,” said Robert Pearce, NASA’s associate administrator for aeronautics.
NASA has collaborated with Boeing on its ecoDemonstrator program almost every year since 2014. Past research has involved a number of hardware and software innovations – even non-stick coatings to prevent airflow-disrupting bug residue from building up on a wing.
Boeing began its program to take promising technologies and new ideas in air safety and reducing emissions and noise and try them out in flight in 2012, often partnering with other companies or research organizations such as NASA.
Each year the company selects a different aircraft to be used as the ecoDemonstrator by partnering with an airline or using a Boeing-owned aircraft.
For this year’s program of flights, which are running now through mid-September, Boeing is partnering with Etihad Airways to use one of the airline’s 787-10 Dreamliners, considered one of the most modern and advanced aircraft flying today.
Measuring Noise from Above
NASA has long studied aircraft noise. Its Aircraft Noise Prediction Program (ANOPP) software tool is a respected, ever-evolving, and widely used standard in the aviation community for doing exactly what its name says.
That computer code is based on years of measuring and understanding how components of an aircraft – the wings, landing gear, the main fuselage – contribute to the noise you hear when an airplane flies overhead.
In the same way, noise levels of engines used for propulsion – no matter the type – have been studied, incorporated into ANOPP, and methods and technologies for reducing engine noise have been developed and implemented, for decades.
But what about the whole package – the airframe and propulsion – as they interact with each other? How do you measure those specific interactions in a way that will give you new information you can use in the future to make even quieter airplanes and engines?
The best way is to fly an airliner low over the ground and measure the noise it makes as it passes over an array of microphones placed directly underneath, either side of, and nearby the flight path. And that’s exactly what NASA and Boeing researchers are doing with the 787 ecoDemonstrator.
“This is an opportunity we get very rarely,” said Russell Thomas, an acoustics expert at NASA’s Langley Research Center in Virginia who is leading what is officially called the Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Test.
It’s not possible to put an airplane the size of a 787 in a wind tunnel, or rely solely on complex computer simulations that may not perfectly represent reality. “Only by flying can we obtain the most realistic conditions for obtaining the measurements we need. And this is really the first time we’ve ever been able to attempt the kind of research we’ve planned,” Thomas said.
For this test, 960 microphones are in place on the ground immediately next to and around the main runway at Glasgow Industrial Airport in Montana, where Boeing has a flight test facility.Another 31 microphones are located even farther away from the runway, and still another 214 microphones have been temporarily wired into locations all over the 787 itself.
Thomas believes this is the largest array of sound instrumentation ever deployed for research like this. “This is pushing the boundaries of acoustic flight testing. I don’t think either NASA or Boeing has ever put so many microphones on the ground or on the aircraft,” Thomas said.
Boeing has dedicated four days in August for the airplane to make as many runs over the microphone array as possible during a four- to five-hour window each morning, when the weather is expected to be more ideal than later in the day.
The 787 will fly in a racetrack pattern over the airport, each time passing over the microphones between 600 to 800 feet above the ground. The low altitude improves the quality of the data collected. “It’s a balance between low enough for a good quality signal and not being too low for safety reasons,” Thomas said.
Passes will feature the aircraft flying in different configurations – landing gear down or up, flaps extended or retracted. Varying engine power levels and speeds used for takeoff, various approaches and landing also will be flown.
With a focus on how noise from the airframe and propulsion interact with each other, one of the things researchers will look for is how noise from the 787’s wing-mounted, twin engines is reflected or shielded by the fuselage and wings depending on where the microphones are.
Research results could help inform noise reduction approaches for today’s aircraft, as well as future commercial airliners that may feature designs in which the engines are placed where the wings and aircraft body might help shield the noise – making the airplane sound quieter on the ground.
Having high-quality, realistic sound data will help improve tools used to predict the noise a future airplane design might make. “We’ll get as close as we can to the real inputs so that the prediction compared to the data can be the most accurate we have been able to do to date,” Thomas said.
Digital Change in Plans
Part of the second NASA project flying on the ecoDemonstrator took place Aug. 14 as the 787 flew from North Charleston, South Carolina to Boeing Field in Seattle, where some final preparations took place before it was flown on to Glasgow, Montana, for the official beginning of the ecoDemonstrator flights.
The experiment is testing the ability of an air traffic management tool to generate an efficient new course for an airplane to follow as it approaches its destination, and then digitally transmit the resulting course change order directly to the cockpit. No new hardware is involved. The demonstration is a test of software being used in a new way and of a new way to use existing digital communication capabilities.
“Taking advantage of digital data communications coupled with advanced decision-making software in a real way to solve complex air traffic control problems – that’s really what we’re bringing to the table with this,” said Richard Coppenbarger, an engineer at NASA’s Ames Research Center in California.
Coppenbarger is the technology lead for this capability, which is called the Tailored Arrival Manager (TAM). It is largely based on a NASA-developed software tool called Auto Resolver. “This is our first foray into the real world with TAM and Auto Resolver, at least in terms of directly reaching a larger aircraft type like the 787,” Coppenbarger said.
As envisioned, here’s how TAM is supposed to work if fully deployed in the future by the Federal Aviation Administration (FAA):
A commercial airliner is nearing the end of its flight and is getting ready for its descent and approach to the airport. But something – perhaps bad weather or congested traffic ahead – is going to require the airplane to alter its course and scheduled arrival time.
The air traffic management tool, which is constantly monitoring the movements of aircraft throughout the National Airspace System, sees this developing situation early and computes a new course for the airplane more efficiently than a human can.
That new course, courtesy of Auto Resolver, provides the most fuel-efficient path for the airplane to fly, ensures the course will maintain FAA-mandated safe separation from all other aircraft, and doesn’t overload with traffic any one particular region of airspace.
The course solution is then automatically sent via digital communications to the Flight Management System (FMS) onboard the aircraft. A chime is sounded, alerting the pilots to the incoming message to their computer.
The pilots then push a button, telling the computer to load the new course, which immediately appears on their cockpit displays as a dotted line, showing them the new flight path. If it looks good to them, they push another button to accept it and the autopilot makes the change.
“But for this ecoDemonstrator test we will be reducing the complexity of what this could be like if actually deployed,” Coppenbarger said.
For example, the AutoResolver will only compute a new flight path that will be the most efficient and not overload any region of airspace with too much traffic. It will not deal with any separation constraints during these initial tests using the Boeing ecoDemonstrator 787.
Also, the pilots will not direct the FMS to fly the solution. Their job will be limited to loading the solution and taking pictures of the resulting displays that show the suggested new flight path. A video camera behind them will record the cockpit scene as well. These images, along with pilot feedback and other data collection, will be used by NASA to continue maturing the TAM automation.
“Basically, we are testing the ability of our system to receive data digitally from the aircraft that TAM can use to generate a solution that then gets sent to the FAA digitally to convert it into a message that they send to the flight deck,” said Arwa Aweiss, the project lead for this experiment who is based at Ames.
The first test on Aug. 14 went according to plan. “Three TAM solutions were digitally delivered to the flight deck as part of the test. As prescribed in the test plan, they were auto-loaded but not flown,” Aweiss said.
“Comments from Boeing indicated that each TAM solution would have been flyable had the pilots chosen to execute them.” Tools with capabilities similar to AutoResolver and TAM complement others that NASA is designing right now or that already have been transferred to the FAA for their further consideration and deployment into the field.
Examples of these tools are known by a plethora of acronyms, including TSAS, FIM, DRAW, ATD-2, EDA and PDRC.
All of the tools are designed to make air traffic management more efficient in order to save fuel, reduce emissions, and increase schedule reliability so passengers can get from airport gate to airport gate as safely and trouble free as possible.