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Aircraft Technology, Integration and Operations

Leveraging past vertical-lift technology for today’s aircraft

By Erasmo Piñero Jr.|December 2024

The V/STOL Aircraft Systems Technical Committee is working to advance research on vertical or short takeoff and landing aircraft.

Many of today’s programs and initiatives to develop vertical takeoff and landing aircraft are looking at technologies that were tested during the 1960s, the heyday of VTOL research in the United States and Europe. Among them is the Speed and Runway Independent Technologies, or SPRINT, a joint DARPA/U.S. Special Operations Command program to build a VTOL X-plane. In May, Aurora Flight Sciences of Virginia and Bell Textron Inc. of Texas were downselected for Phase 1B of SPRINT to complete preliminary design of their concepts. With the SPRINT plane, DARPA wants to demonstrate technologies for runway independence applicable to the next generation of air mobility platforms.

Bell validated its preliminary design for SPRINT with a risk-reduction test conducted at Holloman Air Force Base in New Mexico in late 2023. In a sled test on the Holloman High Speed Test Track, Bell demonstrated a folding rotor as part of a multimode propulsion system. Folding rotor technology was researched in the 1960s and early 1970s. For its SPRINT concept, Bell is leveraging its previously developed high-speed VTOL, or HSVTOL, technology, “which blends the hover capability of a helicopter with the speed (400+ knots), range and survivability of jet aircraft,” according to a press release.

Aurora in May unveiled its SPRINT concept: a three-fan-in-wing HSVTOL. The wing fans are     covered by semicircular upper doors that would open and close for different flight regimes, as was done in the Ryan XV-5 Vertifan experimental VTOL that first flew in 1964. The concept revolves around a blended-wing-body fuselage with a forward fan covered by a door that slides aft and symmetrical louvers embedded in the wing that vector fan thrust for control in vertical flight. The XV-5 also had lateral louvers under its wing fans for control, and its lift fans were tip-driven by diverted engine exhaust gases. Aurora has not revealed how the lift fans on the wings will be powered. Like Bell, Aurora’s goal is to design a VTOL that can reach a cruising speed of 450 knots, with the objective of scaling up the demonstrator to a larger transport aircraft.

In the commercial electric VTOL world, California air taxi developer Joby Aviation in May concluded a preproduction flight test program that began four years ago. The company has since transitioned to initial aircraft production and test flights with a production-conforming prototype for type certification purposes. The preproduction flight test phase comprised 1,500 flights, including about 100 flights with a pilot onboard, and a total distance of 28,700 nautical miles (53,152 kilometers).

V/STOL research in academia also made significant contributions to powered lift. Over the past two years, the Eagle Flight Research Center at Embry-Riddle Aeronautical University in Florida has flown a 36-kilogram uncrewed distributed electric propulsion quad-helicopter, supported by FAA funding. As of August, the helicopter had completed a series of tests, demonstrating stable hover and maneuvering flight after a rotor failure. This is one key safety aspect that will receive lots of attention from federal agencies and the V/STOL community in the coming years, as eVTOLs proliferate. 

2024 Year in Review

Aerospace Design and Structures

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Structures small to large take shape

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NASA survivability test paves way for launching astronauts from U.S. soil

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U.S. Defense Department researchers improve survivability in the air and in space

Aerospace Outreach

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A nod to tragic and triumphant events

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A year of seeing the unseen

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Recreational space travel and Martian exploration highlight year

Aerospace Sciences

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Measuring, simulating, predicting and controlling fluid motion

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Shortened processes, software updates advance meshing, visualization

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Understanding and controlling fluid behavior in flight-relevant environments

Aircraft Technology, Integration and Operations

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Air transportation encounters inflationary headwinds on its recovery from pandemic

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Busy year for advancing emergent flight vehicle technology

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Leveraging past vertical-lift technology for today’s aircraft

Engineering and Technology Management

Solar Impulse 2

A year that caught public’s notice

Atmospheric picture of space

A century ago, aviation became an industry

British F-35Bs

Vertical flight continues to grow

Information Systems

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A drone on Mars hints at space computing things to come

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Aerospace community continues to harness potential of human-machine teaming

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New focus on safety in software

Integration

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NASA flies to Mars; Webb nears launch

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Marching toward the 2030 vision of CFD

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Progress toward the 2030 vision of CFD

Program Committees

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Hypersonics changing the world

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Unmanned integration efforts gain speed

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Mars, Jupiter and the human factor

Propulsion and Energy

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Progress made toward hydrogen-powered aircraft and biofuels

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Rotating detonation designs make progress on multiple continents

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Studies yield hopeful results for saving fuel, meeting performance goals

Space and Missiles

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Space systems have busy year: human spaceflight, Mars missions and on-orbit servicing

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Experiments to use space resources make great strides

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Companies report a number of firsts for missile tests

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Leveraging past vertical-lift technology for today’s aircraft