Bell Completes Critical Design Review for DARPA SPRINT X-76 Aircraft

This article is based on an official press release from Bell Textron Inc.

Bell Textron Inc. has successfully completed the Critical Design Review (CDR) for the Defense Advanced Research Projects Agency (DARPA) SPeed and Runway INdependent Technologies (SPRINT) program. According to a company press release, this major developmental milestone clears the path for Bell to begin manufacturing its next-generation aircraft demonstrator.

The experimental aircraft has officially received the military designation of X-76. Jointly funded by DARPA and the U.S. Special Operations Command, the SPRINT initiative is designed to pioneer advanced, runway-independent aviation technologies that can eventually be scaled across various military platforms.

By passing the CDR phase, Bell transitions from conceptual engineering to the physical construction of the X-76, marking a significant step forward in high-speed vertical lift capabilities.

Advancing the X-76 Demonstrator

Transitioning to the Build Phase

In July 2025, Bell announced it had been down-selected for Phase 2 of the SPRINT program. Following the successful completion of the Critical Design Review, the company is now authorized to proceed with building the X-76 demonstrator.

“Following the completion of CDR, Bell will now begin building a brand-new X-plane with first-of-its-kind stop/fold technology.”

As stated in the official release, this innovative design approach is intended to blend the vertical takeoff and landing (VTOL) flexibility of a helicopter with the high-speed cruise performance of a fixed-wing aircraft. During Phase 1A and Phase 1B of the program, Bell finalized the conceptual and preliminary design efforts that laid the groundwork for the current build phase.

SPRINT Program Goals and Capabilities

Speed and Runway Independence

The primary objective of the SPRINT program is to develop an aircraft capable of operating without traditional runway infrastructure while maintaining high-speed forward flight. The press release notes that the X-76 is being designed to achieve cruise speeds ranging from 400 to 450 knots at relevant altitudes.

Furthermore, the aircraft must be able to hover in austere environments and operate from unprepared surfaces. These capabilities are highly sought after by the U.S. Special Operations Command to ensure rapid, flexible deployment in contested or remote operational theaters. The technologies validated by the X-76 demonstrator are intended to be scalable to different military-aircraft in the future.

Risk Reduction and Legacy

Testing and Validation

To prepare for the physical development of the X-76, Bell completed a series of rigorous risk reduction activities. The company successfully demonstrated its folding rotor, integrated propulsion, and flight control technologies at Holloman Air Force Base. Additionally, Bell conducted extensive wind tunnel testing at the National Institute for Aviation Research (NIAR) at Wichita State University.

The X-76 adds to Bell’s extensive 90-year history of experimental aircraft development. The company has previously pioneered innovative VTOL configurations for NASA, the U.S. Army, and the U.S. Air Force, including the X-14, X-22, XV-3, and XV-15, building upon the historic legacy of the Bell X-1.

AirPro News analysis

At AirPro News, we view the official designation of the X-76 and the transition to the build phase as a strong indicator of the Department of Defense’s commitment to next-generation vertical lift. We note that the requirement to cruise at 400 to 450 knots significantly exceeds the top speeds of conventional helicopters and current tiltrotor aircraft. Successfully demonstrating stop/fold rotor technology in flight will represent a major leap in aerospace engineering, potentially reshaping how special operations and tactical transport missions are executed in environments where traditional runways are unavailable or compromised.

Frequently Asked Questions

What is the X-76?

The X-76 is the official military designation for the next-generation aircraft demonstrator being built by Bell Textron Inc. for the DARPA SPRINT program.

What does SPRINT stand for?

SPRINT stands for SPeed and Runway INdependent Technologies, a joint aviation development program funded by DARPA and the U.S. Special Operations Command.

How fast will the X-76 fly?

According to the program’s official goals, the X-76 is designed to cruise at speeds between 400 and 450 knots at relevant altitudes.

Sources

• Bell Textron Inc.