Experimental

XFV-12 Designed to Take on the British


The story of the XFV-12, marked by misfortune, began in 1972. By this time, the British Harrier had already been operational for three years, having made its first appearance in April 1969.

The British’s clear lead in the military VTOL (Vertical Take-Off and Landing) sector during this period was likely a source of considerable frustration for the United States Military.

American and Soviet pilots were equally astounded the first time they witnessed the British Hawker Siddeley Harrier soar into the skies, seemingly by magic, in the late 1960s.

Despite the British RAF and Royal Navy operating with considerably fewer resources compared to their American and Soviet counterparts, neither of these superpowers had managed to develop a VTOL (Vertical Take-Off and Landing) jet that could rival the Harrier’s capabilities.

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In 1972, the United States allocated a staggering $80.71 billion to defense, equivalent to 6.52 percent of the nation’s total GDP.

Given this immense investment, the notion of trailing behind the British in VTOL technology was untenable, particularly for the U.S. Navy. Concurrently, the Navy was exploring designs for a new class of light aircraft carrier, known as the Sea Control Ship (SCS), which aligned more closely with the modern European carriers.

Commonly known as the Harrier jump jet, the Harrier is a series of jet-powered attack aircraft renowned for their vertical/short takeoff and landing (V/STOL) capabilities.
Commonly known as the Harrier jump jet, the Harrier is a series of jet-powered attack aircraft renowned for their vertical/short takeoff and landing (V/STOL) capabilities.

This pursuit led the U.S. Navy to issue a request for proposals for the construction of VTOL jets that would complement these conceptual carriers, sparking a competition between two major American aerospace companies. On one side was Convair with their Model 200.

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The Model 200 adhered to a fairly traditional VTOL design, featuring a single turbojet engine for horizontal flight and two lift jets for vertical takeoffs and landings.

XFV-12 Development and Design

Initiated by the U.S. Navy’s requirement for a new breed of fighter aircraft capable of vertical takeoff and landing (VTOL) to operate from smaller aircraft carriers, the XFV-12 was conceptualized to fill this niche.

Rockwell International, already a significant player in aerospace engineering, took on the challenge with a vision to integrate supersonic capabilities with VTOL technology, a feat that had not yet been achieved.

The design of the XFV-12 was heavily influenced by the need for a dual-role aircraft that could combine the agility and functionality of VTOL with the high-speed performance of a conventional supersonic fighter.

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The aircraft’s design featured a canard layout, which included a set of small forward wings (canards) near the cockpit and larger main wings towards the rear. This layout was selected to provide the necessary lift and stability for both vertical takeoff and high-speed flight.

XFV-12A mockup at the North American plant, Columbus, Ohio, ca. 1973.

Central to the XFV-12’s design was its innovative thrust augmentation system. This system aimed to redirect the jet engine’s exhaust to flow over the wings and canards, thereby increasing lift for vertical takeoff.

The concept was groundbreaking, as it promised to provide VTOL capabilities without the need for additional lift engines or rotating nozzles, which were typical in other VTOL designs like the Harrier. This not only aimed to reduce the weight and complexity of the aircraft but also hoped to increase the efficiency and performance of the VFV-12.

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However, the implementation of this thrust augmentation system presented significant engineering challenges. Balancing the aerodynamic requirements of supersonic flight with the complex airflow dynamics needed for VTOL operation was a daunting task. The aircraft needed to be lightweight enough for vertical lift yet sturdy and aerodynamic for supersonic speeds.

As the project progressed, it became apparent that integrating these cutting-edge technologies into a functional aircraft was more challenging than initially anticipated.

The XFV-12’s design and development phase was a period of trial and error, with engineers continuously grappling with the complexities of its advanced systems and ambitious performance goals. The challenges faced during this phase laid the groundwork for the eventual outcome of the project and highlighted the difficulties in marrying VTOL and supersonic capabilities in a single airframe.

Testing the XFV-12

As the prototype moved from the drawing board to real-world testing, the complexities and limitations of the aircraft’s innovative features became increasingly evident. One of the primary challenges faced during the testing phase was the inadequacy of the thrust augmentation system, which was central to the XFV-12’s VTOL capabilities.

This system, designed to redirect the jet engine exhaust over the wings to generate additional lift, failed to produce the necessary vertical thrust.

The XFV-12 aircraft mounted for tethered hover flights on Langley Impact Dynamics Research Facility.
The XFV-12A aircraft mounted for tethered hover flights on Langley Impact Dynamics Research Facility.

Despite numerous adjustments and modifications, the system could not provide the lift required for vertical takeoff and hovering. This shortcoming was a significant setback, as the VTOL capability was a key requirement from the U.S. Navy and a major selling point of the XFV-12 design.

Additionally, the XFV-12 encountered problems related to its weight. The aircraft became increasingly heavy as development progressed, which further hindered its ability to achieve vertical lift.

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The weight issue was compounded by the complexity of the thrust augmentation system, which added to the overall mass of the aircraft without delivering the expected performance benefits.

Another major challenge was integrating the various advanced systems of the XFV-12 into a cohesive and functional whole. The aircraft was a complex integration of aerodynamics, propulsion, and control systems, each with its own set of technical challenges. Balancing these elements, particularly in an experimental design that sought to combine supersonic speed with VTOL operation, proved to be a daunting task for the engineers.

It was believed that, by the time it was discontinued, the XFV-12 project had consumed up to $1 billion in government funding.

The XFV-12’s testing phase was also marked by difficulties in handling and stability, both in simulated environments and in tethered flight tests.

The aircraft’s unique design and propulsion system required a delicate balance to maintain control, particularly during the critical phases of vertical takeoff and landing. These issues raised concerns about the aircraft’s safety and operational viability.

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The testing and challenges faced by the Rockwell XFV-12 were a stark reminder of the difficulties in pushing the boundaries of aviation technology. The project’s ambitious goals, while groundbreaking on paper, encountered insurmountable obstacles in practice.

The inability of the XFV-12 to meet its key performance objectives, particularly in VTOL operations, along with its weight and stability issues, ultimately led to the cancellation of the program. This phase of the XFV-12’s development highlighted the complex interplay between innovation, practicality, and the harsh realities of aerospace engineering.

Cancellation of XFV-12

As the testing phase progressed, it became increasingly apparent that the XFV-12 was falling short of its ambitious goals, particularly in achieving effective vertical takeoff and landing (VTOL) capabilities.

The aircraft’s thrust augmentation system, pivotal to its VTOL operations, consistently failed to provide the necessary lift. Despite numerous adjustments, the system could not overcome the fundamental issues of insufficient thrust and the aircraft’s excessive weight.

After the testing phase, and in light of escalating costs, the Navy concluded that the XFV-12A did not justify additional investment and subsequently cancelled the project in 1981.
After the testing phase, and in light of escalating costs, the Navy concluded that the XFV-12A did not justify additional investment and subsequently cancelled the project in 1981.

Additionally, the XFV-12’s development was marked by significant financial investment. The escalating costs, coupled with the technical challenges, placed immense pressure on the project. Each unsuccessful test and each unmet milestone further diminished confidence in the aircraft’s potential for success.

The U.S. Navy, which had initially shown great interest in the XFV-12 for its potential to operate from smaller aircraft carriers, began to reevaluate its commitment to the project.

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With the XFV-12 unable to demonstrate its key feature of VTOL and with concerns over its operational safety and viability, the Navy’s support waned. In the face of these technical and financial hurdles, the decision to cancel the project became inevitable.

In 1981, the XFV-12 project was officially terminated. The cancellation marked the end of a bold but ultimately unfeasible attempt to merge supersonic capabilities with VTOL technology in a single fighter aircraft platform. The decision reflected a pragmatic acknowledgment of the XFV-12’s insurmountable technical issues and the shifting priorities and needs of the U.S. Navy.

It is believed that the XFV-12 project consumed as much as $1 billion in government funding before its abrupt termination. When adjusted for inflation, this amount translates to a staggering $3.26 billion spent by the Navy on developing just a single prototype.

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In stark contrast, the Harrier jump jet and its various iterations have been sold in the hundreds over several decades. This success led to a point where even the United States had to embrace the adage, “If you can’t beat them, join them.”

The first American version of the British Aerospace Harrier II was inducted into service with the U.S. Navy and Marine Corps in January 1985.

Fast forward to 2023, and the U.S.-led F-35B Lightning program, which aims to succeed the Harrier, is partially supervised by Lieutenant Commander Stuart Greenfield of the Royal Navy, who is an air engineer. This highlights the influence and legacy of the Harrier, even in contemporary military aviation programs.