Civil Aviation

The Northrop Alpha was the First to have Retractable Undercarriage

The Northrop Alpha, an iconic aircraft from the early 1930s, exemplifies the innovation and ambition of its era. Conceived by Jack Northrop, this aircraft was a significant milestone in the development of all-metal monoplanes, setting new standards in speed, efficiency, and design.


Origins and Development

The Northrop Alpha emerged from a period of dynamic innovation in the late 1920s, a time when the aviation industry was experiencing rapid advancements in technology and design. Jack Northrop, a pioneering aeronautical engineer with a vision for the future of aviation, founded the Northrop Corporation in 1929.

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He aimed to create an aircraft that would not only meet but exceed the burgeoning demands for speed, efficiency, and reliability in both mail and passenger transport.

An Alpha undergoing testing.
An Alpha undergoing testing.

Northrop’s prior experience was crucial in shaping his vision for the Alpha. At Lockheed, he significantly contributed to the Lockheed Vega’s design, an aircraft renowned for performance and durability.

The Vega’s success showcased the potential of monoplane designs. Northrop aimed to push these concepts further, using advanced materials and construction techniques.

He envisioned an aircraft that would surpass the limitations of the biplanes still dominating the skies. He focused on creating a monoplane to reduce drag and improve aerodynamic efficiency.

This vision led to the cantilevered wing concept, eliminating external bracing wires and struts. By removing these features, Northrop achieved a smoother, more aerodynamic profile, reducing drag and enhancing speed.

The Alpha’s structural design was groundbreaking. Northrop used all-metal construction, primarily aluminium, which balanced weight and strength perfectly.

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This choice marked a significant shift from the wood-and-fabric methods of the time. Aluminium ensured the Alpha could withstand frequent, long-distance flights, offering greater durability and longevity.

There only surviving examples are now museum pieces. Photo credit - user:350z33
The only surviving examples are now museum pieces. Photo credit – user:350z33

Monocoque Fuselage

One of the most innovative aspects of the Alpha’s design was its monocoque fuselage. This construction method involved creating a single shell that supported the structural load, as opposed to relying on an internal framework.

The monocoque design reduced the overall weight of the aircraft while increasing its strength and structural integrity. It also contributed to the Alpha’s streamlined appearance, which was both aesthetically pleasing and functionally superior in reducing aerodynamic drag.

The powerplant chosen for the Alpha was the Pratt & Whitney R-1340 Wasp engine, a radial engine capable of delivering 450 horsepower. This engine selection was critical, as it provided the necessary power to achieve the performance goals Northrop had set.

The P&W R-1340 Wasp. Photo credit - Sanjay Acharya CC BY-SA 3.0.
The P&W R-1340 Wasp. Photo credit – Sanjay Acharya CC BY-SA 3.0.

The combination of the lightweight, all-metal construction and the powerful Wasp engine enabled the Alpha to reach speeds that were unprecedented for its time.

The development process of the Northrop Alpha involved rigorous testing and refinement. Northrop and his team conducted extensive wind tunnel tests to optimise the aerodynamic properties of the aircraft.

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They meticulously worked on every detail, from the wing shape to the fuselage contours, ensuring that the final design would meet their ambitious performance targets.

In early 1930, the Northrop Alpha made its debut flight. This milestone marked not only the successful culmination of Northrop’s vision and efforts but also a significant leap forward in aviation technology.

The Alpha’s first flight demonstrated its impressive capabilities, validating the innovative design choices that had been made throughout its development.

Operational Use

The Northrop Alpha excelled in performance and operational use, establishing itself as a versatile and reliable aircraft during the early 1930s. Its design innovations translated into impressive performance metrics, making it a preferred choice for both mail and passenger transport.

The Alpha’s top speed of approximately 160 miles per hour represented a significant improvement over contemporary aircraft, enabling it to outpace many of its rivals.

This high-speed capability was crucial for improving the efficiency of mail delivery and passenger services, reducing travel times across long distances. At a cruising speed of 125 miles per hour, the Alpha maintained a balance between speed and fuel efficiency, making it suitable for a range of operational needs.

Note the small windows for passengers.
Note the small windows for passengers.

Its range of 560 miles allowed the Northrop Alpha to cover considerable distances without requiring frequent refuelling stops. This extended range was particularly advantageous for mail routes, where reliability and consistency in delivery times were paramount.

The aircraft’s ability to sustain long flights with fewer interruptions greatly enhanced operational efficiency and service quality.

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Transcontinental and Western Air

Transcontinental and Western Air (TWA), a major airline of the era, recognised the potential of the Northrop Alpha and incorporated it into their fleet. TWA used the Alpha primarily for mail and passenger transport, capitalising on its speed and reliability.

The aircraft played a pivotal role in enhancing TWA’s transcontinental services, providing a competitive edge in the burgeoning aviation market. The Alpha’s operational success with TWA underscored its suitability for commercial use, proving that it could meet the rigorous demands of scheduled airline services.

Pilots appreciated the Alpha’s responsive handling and robust construction. The cantilevered wing design, free from external bracing, contributed to the aircraft’s smooth and stable flight characteristics.

Pilots found the Alpha easy to manoeuvre, with its aerodynamic design providing a high degree of control and responsiveness. The enclosed cockpit offered improved visibility and protection, enhancing safety and operational efficiency.

A TWA Alpha.
A TWA Alpha.

These features made the Alpha a favourite among pilots, who valued both its performance and the improved flying experience it provided.

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The Northrop Alpha also played a role in pioneering air routes and demonstrating the viability of all-metal monoplanes for commercial aviation.

Its successful operation on various routes helped establish the reliability and efficiency of such aircraft, encouraging further development and adoption within the industry.

The Alpha’s performance in operational use provided valuable data and insights that informed future aircraft designs, contributing to the evolution of aviation technology.

In addition to its commercial success, the Alpha’s design and performance influenced military aviation. The aircraft’s capabilities showcased the potential for all-metal monoplanes in military applications, where speed, durability, and reliability were equally critical.

The innovations embodied in the Alpha provided a blueprint for future military aircraft, highlighting the advantages of advanced aerodynamics and materials.


The initial version, the Northrop Alpha 1, was primarily designed for mail transport. It featured an enclosed cockpit for the pilot and a streamlined fuselage to reduce drag and enhance speed. This model established the Alpha’s reputation for speed and efficiency, setting the stage for subsequent variants.

Northrop then introduced the Alpha 2, which retained the core features of the Alpha 1 but included modifications to improve passenger comfort.

Passenger Use

The Alpha 2 offered an enclosed cabin with seating for up to six passengers, making it suitable for commercial passenger services. These modifications addressed the growing demand for reliable and comfortable air travel, allowing airlines to offer enhanced services.

The Alpha 3 variant saw further refinements in aerodynamics and performance. It incorporated minor design tweaks to the wing structure and fuselage, aiming to optimise airflow and reduce drag even further.

There were several variants of the Alpha, showing the quickly evolving technology.
There were several variants of the Alpha, showing the quickly evolving technology.

These changes enhanced the aircraft’s speed and efficiency, maintaining its competitive edge in the aviation market.

The Alpha 4 emerged as a specialised variant designed for long-distance mail routes. This model featured additional fuel capacity, extending the aircraft’s range to accommodate longer flights without frequent refuelling stops.

The Alpha 4 also included structural reinforcements to handle the increased weight and stress associated with extended flights.

Northrop developed the Alpha 5 as an experimental variant to test new technologies and materials. This model incorporated advanced construction techniques, including the use of new alloys and composite materials.

The Alpha 5 served as a testbed for innovations that would later influence future aircraft designs, demonstrating Northrop’s commitment to continuous improvement and technological advancement.

The Alpha 6 variant focused on improving payload capacity. This version featured modifications to the fuselage and landing gear to support heavier loads, making it suitable for transporting larger quantities of mail and cargo.

The Alpha 6’s enhanced payload capabilities addressed the needs of commercial operators seeking to maximise efficiency and profitability.

Final Evolution

The Alpha 7 represented the final evolution of the series, combining all the advancements and lessons learned from the previous variants. It offered superior performance, range, and payload capacity, making it the most versatile and capable version of the Alpha.

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The Alpha 7’s design incorporated the latest aerodynamic improvements, structural enhancements, and technological innovations, solidifying its place as a leading aircraft of its time.