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NASA\u2019s X-59 quiet supersonic research aircraft successfully completed a critical series of tests in which the airplane was put through its paces for cruising high above the California desert \u2013 all without ever leaving the ground.<\/p>\n
\u201cThe idea behind these tests is to command the airplane\u2019s subsystems and flight computer to function as if it is flying,\u201d said Yohan Lin, the X-59\u2019s lead avionics engineer at NASA\u2019s Armstrong Flight Research Center in Edwards, California.<\/p>\n
The goal of ground-based simulation testing was to make sure the hardware and software that will allow the X-59 to fly safely are properly working together and able to handle any unexpected problems.<\/p>\n
Any new aircraft is a combination of systems, and identifying the little adjustments required to optimize performance is an important step in a disciplined approach toward flight.<\/p>\n
\u201cWe thought we might find a few things during the tests that would prompt us to go back and tweak them to work better, especially with some of the software, and that\u2019s what we wound up experiencing. So, these tests were very helpful,\u201d Lin said.<\/p>\n
Completing the tests marks another milestone off the checklist of things to do before the X-59 makes its first flight this year, continuing NASA\u2019s Quesst mission to help enable commercial supersonic air travel over land.<\/p>\n
During the testing, engineers from NASA and contractor Lockheed Martin turned on most of the X-59\u2019s systems, leaving the engine off. For example, if the pilot moved the control stick a certain way, the flight computer moved the aircraft\u2019s rudder or other control surfaces, just as it would in flight.<\/p>\n
At the same time, the airplane was electronically connected to a ground computer that sends simulated signals \u2013 which the X-59 interpreted as real \u2013 such as changes in altitude, speed, temperature, or the health of various systems.<\/p>\n
Sitting in the cockpit, the pilot \u201cflew\u201d the aircraft to see how the airplane would respond.<\/p>\n
\u201cThese were simple maneuvers, nothing too crazy,\u201d Lin said. \u201cWe would then inject failures into the airplane to see how it would respond. Would the system compensate for the failure? Was the pilot able to recover?\u201d<\/p>\n
Unlike in typical astronaut training simulations, where flight crews do not know what scenarios they might encounter, the X-59 pilots mostly knew what the aircraft would experience during every test and even helped plan them to better focus on the aircraft systems\u2019 response.<\/p>\n
In aircraft development, this work is known as \u201ciron bird\u201d testing, named for a simple metal frame on which representations of the aircraft\u2019s subsystems are installed, connected, and checked out.<\/p>\n
Building such a testbed is a common practice for development programs in which many aircraft will be manufactured. But since the X-59 is a one-of-a-kind airplane, officials decided it was better and less expensive to use the aircraft itself.<\/p>\n
As a result, engineers dubbed this series of exercises \u201caluminum bird\u201d testing, since that\u2019s the metal the X-59 is mostly made of.<\/p>\n
So, instead of testing an \u201ciron bird\u201d with copies of an aircraft\u2019s systems on a non-descript frame, the \u201caluminum bird\u201d used the actual aircraft and its systems, which in turn meant the test results gave everyone higher confidence in the design,<\/p>\n
\u201cIt\u2019s a perfect example of the old tried and true adage in aviation that says \u2018Test what you fly. Fly what you test,\u2019\u201d Lin said.<\/p>\n
With aluminum bird testing in the rearview mirror, the next milestone on the X-59\u2019s path to first flight is take the airplane out on the taxiways at the airport adjacent to Lockheed Martin\u2019s Skunk Works facility in Palmdale, California, where the X-59 was built. First flight would follow those taxi tests.<\/p>\n
Already in the X-59\u2019s logbook since the fully assembled and painted airplane made its public debut in January 2024:<\/p>\n
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