NASA Chase Aircraft Ensures X-59’s Safety in Flight  – NASA

As NASA’s X-59 quiet supersonic research plane continues a series of flight tests over California’s high desert in 2026, its pilot will fly with a buddy who will keep a close eye on his safety.

This colleague will be another test pilot in another chase plane. His job as pursuit pilot: keep a close eye on things as he follows the X-59 through the sky, providing an extra pair of eyes to ensure flight tests are as safe as possible.

Having a fighter pilot to ensure operations run smoothly is an essential task when an experimental aircraft exercises its capabilities for the first time. The pursuit pilot also assumes duties such as monitoring local weather and supplementing communications between the X-59 and air traffic control.

“All of this helps reduce the test pilot’s workload so they can focus on the actual test mission,” said Jim “Clue” Less, a NASA research pilot since 2010 and a 21-year veteran U.S. Air Force pilot.

Less served as a pursuit pilot in a NASA F/A-18 research aircraft when NASA test pilot Nils Larson made the first flight of the X-59 on October 28. In the future, Less and Larson will take turns flying as an X-59 test pilot or pursuit pilot.

So how far does a chase plane fly to the X-59?

“We fly as close as we need to,” Less said. “But no closer than necessary.”

The distance depends on where the chase plane needs to be to best ensure the success of the test flight. However, fighter pilots never get so close that safety is compromised.

Jim “hint” LESS

NASA test pilot

For example, during the first flight of the X-59, the pursuit aircraft moved within a wingspan of the experimental aircraft. At this proximity, the speed and altitude indicators inside the two planes could be compared, allowing the X-59 team to calibrate their instruments.

Typically, the pursuit aircraft will remain approximately 500 and 1,000 feet away, approximately 5 to 10 times the length of the X-59 itself, while the two aircraft cruise together.

“Of course the chase pilot can get closer if I need to look at something on the plane,” Less said. “We would get as close as we need to, but for the most part the goal is to stay apart.”

The up-close and personal view of the chase aircraft also provides the ability to capture photos and videos of the test aircraft.

For the initial flight of the

“We really have the best views,” Less said. “The test team’s top priority is always a safe flight and landing. But if we get great photos in the process, that’s an added bonus.”

Chase planes can also carry sensors that collect data during flight that would be impossible to obtain from the ground. In a future phase of the X-59’s flights, the pursuit aircraft will carry a probe to measure the X-59’s supersonic shock waves and help validate that the aircraft produces a quieter sonic “thud” rather than a loud sonic boom to people on the ground.

The instrumentation was successfully tested using a pair of NASA F-15 research aircraft earlier this year.

As part of NASA’s Quesst mission, the data could help pave the way for faster-than-sound commercial air travel over land.

Chase aircraft have been a staple of civil and military flight testing for decades, with NASA and its predecessor, the National Advisory Committee for Aeronautics, employing aircraft of all types for this work.

Today, at NASA’s Armstrong Flight Research Center in Edwards, California, two different types of research aircraft are available to serve as chases for X-59 flights: NASA-operated F/A-18 Hornets and F-15 Eagles.

Although both types qualify as fighter aircraft for the X-59, each has characteristics that make them suitable for certain tasks.

The F/A-18 is a bit more agile for flying at lower speeds. One of NASA’s F/A-18s has a two-seat cockpit, and the optical quality and field of view of its canopy make it the plane of choice for Armstrong’s flight photographers.

At the same time, the F-15 is more capable of keeping pace with the X-59 during supersonic test flights and carries instrumentation that will measure the X-59’s shock waves.

“The choice of which chase aircraft we use for a given test flight of the X-59 could go either way depending on other mission needs and whether scheduled maintenance requires the aircraft to be grounded for a period of time,” Less said.