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Interesting Engines: The Napier Nomad

October 29, 2012 by Matt

Napier Nomad 1 Aero Engine Motor

The Napier Nomad is unquestionably an incredibly complex piece of engineering. Whether it qualifies as brilliant or completely overwrought is more arguable.

Fresh off the success of the Sabre, most notably the powerplant for the V1 buzz bomb killer Hawker Tempest, Napier embarked on another ambitious engine development program, one that eventually led to the Nomad. First tested in 1949, the Nomad was Napier’s attempt to leverage their piston engine mastery and introduce a fuel-efficient alternative to the then-new jet engine technology.

Napier Nomad 1 Diesel 2-Stroke Aero Engine Motor Schematic Diagram Operation Drawing

At least with respect to the company’s goals of creating an economical engine, the Nomad succeeded. To this day, it remains one of the most efficient piston engines ever made when examined from the standpoint of specific fuel consumption, or fuel consumed per unit of power produced. That said, such economy came at a price: An almost Rube Goldberg-like level of complexity. At its core, the Nomad was a 41-liter, valveless, 2-stroke, horizontally-opposed 12-cylinder diesel engine. Around this, Napier added an array of combustion chambers, valves, couplings, clutches, turbines and compressors designed to capture every last bit of exhaust energy in service of turning the twin contra-rotating propellers bolted to the nose of the engine.

Napier Nomad 1 Diesel 2-Stroke Aero Engine Motor Schematic Diagram Operation Drawing

When it worked, it worked: Mounted in the nose of an Avro Shackleton testbed aircraft, the Nomad produced 3,000 hp with exceptionally low fuel consumption for its day. It’s a tribute to Napier’s expertise and persistence that they managed to get all its parts working harmoniously for 1,000 hours of testing.

Unfortunately, the Nomad, like other incredibly sophisticated piston engines of the day, was simply overtaken by progress—new jet engine technology promised much higher speeds with an exponentially lower level of engine complexity, and as for fuel consumption, it was farther down on most customers’ lists of priorities; the lean days of the early ’70s were still over 20 years away. The Nomad found no takers, and fell into obscurity.

Editor’s note: This post is part of an ongoing series examining unique and significant powerplants. Read the other installments here:

Filed under: Interesting Engines, Technical


  1. Papabrewsky says:

    Truly a bizarre engine; 12 cylinder, two-stroke diesel. I would love to hear this thing run. I wonder how many were built?

    BTW, Great post! I remember reading about an unusual ‘5-cycle’ engine developed by Mercedes Benz, which was like a combination of 4 & 2 stroke design. Whatever happened to that one?

  2. percy says:

    brilliant ,could be revived today as the need for fuel efficient engines is increasing ,with todays alloys and technological advances this engine would be incredibly versitile

  3. Percy Eggbowelman says:

    If the Napier Nomad engine is redeveloped with up to date materials and technoligy it could be be a brillant power plant for medium size airliners and cargo air craft , If a reworked Mustang P51 was fitted with this engine and further developed it would an ideal war plane against enemy insurgents .

  4. Austen Weitmann says:

    what a great piece of engineering. I bet if it was revived and manufactured with modern technology it would be a real masterpiece.

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