WWII

The W.11 Air Horse was a Revolutionary Heavy Lift Helicopter

The Cierva W.11 Air Horse, an innovative helicopter designed during the mid-20th century, known for its unique configuration and impressive lifting capacity, the Air Horse demonstrated advanced engineering and foresight in vertical flight technology.

Development

Development of the W.11 Air Horse was rooted in the innovative vision of the Cierva Autogiro Company during the late 1940s. Recognizing the burgeoning need for heavy-lift helicopters, Dr. George H. W. Cierva, son of the renowned autogyro inventor Juan de la Cierva, spearheaded the initiative to design a rotorcraft that could address both civilian and military demands.

The company, already known for its pioneering work in rotorcraft, decided to embark on this ambitious project to push the boundaries of helicopter design. Dr. Cierva, inspired by the success of his father’s autogyros, aimed to create a helicopter that could carry significant payloads, thus filling a critical gap in the market.

The Air Horse laid the foundations for other heavy-lift helicopters that are commonplace today.

The project, initially designated as the W.11, aimed to leverage the company’s extensive experience in rotary-wing aircraft to develop a heavy-lift helicopter with unparalleled capabilities.



During the conceptual phase, Dr. Cierva and his team faced several technical challenges. They needed to design a helicopter that not only had substantial lifting power but also offered stability and safety. After extensive research and experimentation, they concluded that a tri-rotor configuration would best meet these requirements.

This design, which involved three main rotors arranged in a triangular configuration, promised enhanced stability and lifting power compared to traditional single-rotor designs.

With the tri-rotor concept in place, the engineering team focused on integrating this innovative design into a practical helicopter. They selected three Alvis Leonides radial engines to power the rotors, ensuring that each rotor had its own dedicated power source.

This configuration provided redundancy, a crucial feature for safety, as the helicopter could still operate if one engine failed.



The design process also included significant aerodynamic testing and structural analysis to ensure that the helicopter could handle the stresses associated with heavy lifting. The engineers designed the fuselage to be streamlined, with a spacious cabin to accommodate both passengers and cargo.

The cockpit offered excellent visibility, an essential factor for piloting a heavy-lift aircraft.

The rear doors opened to accommodate large cargo loads.

Throughout the development phase, the Cierva Autogiro Company collaborated with various partners and suppliers to source the necessary materials and components. They conducted rigorous testing on each component, including the engines, rotors, and control systems, to ensure reliability and performance.



The team’s commitment to quality and innovation drove them to overcome numerous technical obstacles, laying the groundwork for a helicopter that could redefine heavy-lift capabilities.

By late 1948, the W.11 was ready for its first flight. The company’s engineers and pilots had worked tirelessly to prepare the helicopter for this critical milestone. On December 7, 1948, Chief Test Pilot Alan Marsh took the Air Horse to the skies for the first time at RAF Northolt.

The successful maiden flight marked a significant achievement in the project, validating the team’s innovative design and engineering efforts.

Despite the technical success of the Air Horse, the project faced external challenges. The post-war economic environment in Britain led to funding constraints, and priorities within the aviation industry began to shift.



Additionally, the complexity of the tri-rotor system posed operational and maintenance challenges, which further complicated the path to mass production. Nonetheless, the development of the Air Horse remains a remarkable example of ingenuity and perseverance in the face of adversity.

Helicopters are complicated machines, let alone something with three rotors.

Design and Engineering

The design and engineering of the W.11 represented a groundbreaking approach in the field of rotorcraft. Dr. George H. W. Cierva and his team embarked on an ambitious project to develop a helicopter that could achieve unparalleled lifting capacity while maintaining stability and safety. The result was an aircraft that deviated significantly from conventional helicopter designs of its time.

At the core of the Air Horse’s design was its unique tri-rotor configuration. Unlike traditional helicopters, which typically feature a single main rotor and a tail rotor, the Air Horse utilized three main rotors arranged in a triangular formation.

This design provided several advantages, including enhanced lift and stability. Each rotor was powered by a separate Alvis Leonides radial engine, a choice that not only provided significant power but also ensured redundancy. If one engine failed, the helicopter could continue to operate using the remaining two engines, thus increasing overall safety.

The engineering team faced considerable challenges in integrating the tri-rotor system into a functional helicopter. The synchronization of the three rotors required precise mechanical linkages and control systems to ensure that they operated in harmony.

Whilst it might have looked unusual the W.11 was a solid design.

The team developed a complex rotor head mechanism that could distribute power evenly and manage the aerodynamic forces generated by the rotors. This system allowed for smooth and controlled flight, even under heavy load conditions.



Aerodynamics played a crucial role in the Air Horse’s design. The engineers designed the helicopter’s fuselage to minimize drag and maximize efficiency. The streamlined body, which resembled a conventional aeroplane’s fuselage, reduced air resistance and contributed to the helicopter’s relatively high maximum speed of approximately 100 mph.

The fuselage housed the crew, passengers, and cargo, with the cockpit positioned at the front to provide excellent visibility for the pilots.

The Air Horse featured a spacious cabin designed to accommodate up to 36 passengers or equivalent cargo. The layout prioritised both comfort and functionality, with seating arrangements that could be adapted for various purposes, including troop transport, medical evacuation, and cargo hauling.

The rear section of the fuselage included large doors, allowing for easy loading and unloading of bulky items.

Structurally, the Air Horse was designed to handle the stresses associated with heavy lifting. The helicopter’s airframe incorporated robust materials and construction techniques to ensure durability and reliability.

Thanks to the cockpit being located above the fuselage the pilot had a good view out.

The rotor blades, crafted from advanced composites and metals, offered a balance of strength and flexibility, essential for managing the aerodynamic forces during flight. The landing gear, built to withstand the weight of the fully loaded helicopter, featured shock absorbers to cushion landings and reduce impact forces.

The engineering team also paid close attention to the helicopter’s control systems. The tri-rotor configuration necessitated a sophisticated set of controls to manage the pitch, roll, and yaw of the aircraft.

The pilot could adjust the angle of each rotor blade individually, allowing for precise manoeuvring. The team incorporated a set of redundant control linkages to ensure that the helicopter remained responsive even if one system failed.

The powerplant selection was another critical aspect of the design. The Alvis Leonides radial engines, each generating 520 horsepower, provided the necessary power to lift the helicopter’s substantial weight. The engines were mounted in such a way that they could be easily accessed for maintenance and repairs, a crucial consideration for operational efficiency.

The exhaust system was designed to minimize heat and noise, improving the comfort for both the crew and passengers.

Fuel efficiency and range were also key considerations. The Air Horse was equipped with large fuel tanks that allowed for extended flight times, making it suitable for long-range missions.

The engineers optimised the fuel system to ensure a steady and reliable supply of fuel to the engines, even during demanding flight conditions.

Throughout the design and engineering process, the Cierva team conducted extensive testing and evaluation. Wind tunnel tests, structural stress tests, and flight simulations were all part of the rigorous development process.

These tests provided valuable data that the engineers used to refine and improve the helicopter’s performance and reliability

Operational History

The operational history of the W.11 Air Horse began on December 7, 1948, when it first took to the skies at RAF Northolt with Chief Test Pilot Alan Marsh at the controls. This maiden flight marked a significant milestone for the Cierva Autogiro Company, demonstrating the feasibility and stability of the innovative tri-rotor design.

The helicopter’s initial performance impressed both engineers and aviation experts, confirming that the Air Horse could indeed meet its design goals for heavy lifting.

Following the successful maiden flight, the Cierva team embarked on an extensive series of test flights to further evaluate and refine the Air Horse’s capabilities. These tests involved rigorous assessments of the helicopter’s handling, stability, and lifting power.

Pilots and engineers conducted various manoeuvres, both with and without payloads, to understand how the helicopter performed under different conditions. The W.11 demonstrated exceptional stability and control, even when operating near its maximum takeoff weight of 17,000 pounds.

There are no tri-rotor helicopters in active service. Models such as the CH-47 are so effective there is no need.

This period of testing also revealed the helicopter’s ability to achieve a maximum speed of approximately 100 mph and reach a service ceiling of 10,000 feet.

As testing progressed, the Air Horse attracted significant interest from both military and civilian sectors. The British military saw potential in the helicopter for troop transport, logistical support, and medical evacuation roles.

Civilian interest focused on its capabilities for cargo transport, especially in remote and hard-to-reach areas where conventional fixed-wing aircraft faced limitations. The helicopter’s ability to carry up to 36 passengers or equivalent cargo made it an attractive option for various heavy-lift applications.

Despite its promising performance, the Air Horse faced considerable challenges. The post-World War II economic climate in Britain led to funding constraints that affected many aerospace projects, including the Air Horse.

Additionally, the complexity of the tri-rotor system presented operational and maintenance difficulties that had to be addressed. The need for specialized training for pilots and maintenance crews added to the operational costs, further complicating the path to widespread adoption.

Crash

Tragically, on June 13, 1950, during a test flight at the Cierva facility in Eastleigh, the Air Horse encountered a catastrophic failure that resulted in a crash. This accident led to the loss of three crew members, including Dr. Cierva himself.

The unfortunate accident sealed the fate of the W.11.

The crash investigation revealed that a failure in one of the rotors caused the helicopter to lose control. This incident cast a shadow over the Air Horse project and raised concerns about the safety and reliability of the tri-rotor configuration.

The accident had a profound impact on the future of the Air Horse. The British Ministry of Supply, which had been evaluating the helicopter for potential military use, decided to halt further development and testing.

The tragic loss of Dr. Cierva, a leading figure in the project, dealt a significant blow to the Cierva Autogiro Company. The combination of technical challenges, economic constraints, and the accident ultimately led to the cancellation of the Air Horse program.

Despite the project’s premature end, the W.11 Air Horse left a lasting legacy in the field of rotorcraft design. The lessons learned from the development and testing of the tri-rotor configuration provided valuable insights that influenced subsequent helicopter designs.

The Air Horse demonstrated the potential advantages of multi-rotor systems for heavy lifting and highlighted the importance of rigorous testing and safety protocols in aviation innovation.

The W.11 Air Horse remains a remarkable example of mid-20th-century engineering ambition. Its operational history, though brief, showcased the innovative spirit of its designers and their willingness to push the boundaries of helicopter technology.

The Air Horse’s contributions to the understanding of rotorcraft dynamics and heavy-lift capabilities continue to be recognized in the annals of aviation history.