Diesel engines are making a come back in aviation circles. A few months back we covered the Superior Gemini two-stroke, a three-cylinder, six-opposed piston engine for light sport aircraft. A competitor to Superior in the LSA diesel market is the engine of DeltaHawk. Unlike the Superior engine, DeltaHawk Engines are primarily designed for the general aviation community as a whole, not just the niche market of light sport aircraft (aircraft exclusively for a single pilot to fly for pleasure).
The four-cylinder V arrangement of the DeltaHawk engine is a layout more familiar to the automotive enthusiast but less common in the aviation world where horizontally opposed is the arrangement of choice for minimal frontal area, and therefore less drag. This V4 aluminum diesel engine is two-stroke and has been meticulously engineered to meet the specific needs and priorities of the aviation community. Many onlookers from the automotive world may be shocked at the low horsepower per displacement ratio of many aircraft engines. This de-tuning is an intentional design for longevity, and reliability.
It is important to understand that aircraft engines run at a much more constant rpm usually only varying 1,500 rpm from idle to red line. The consistent low rpm operation of these powerplants means that the cam profiles, magneto ignition (in Avgas motors), and relatively low efficiency per displacement all are designed with reliability in mind.
Aircraft engines are extremely light weight, with aircooled engines being the norm, liquid cooling is a rare sight among light aircraft. In the case of the DeltaHawk an all aluminum construction only yielding weight to steel cylinder liners mandatory to contain the explosive diesel combustion cycle. According to DeltaHawk CEO Diane Doers; “Our number one goal was to end up with a true aviation engine suited to the aviation mission and is as light weight as it could be for the power it produces. That means you can’t start out by over-engineering things 100-percent or you have an engine that weighs a ton, and performs wonderfully except it won’t lift an airplane, or lift itself.”
Weighing in at 315 pounds the DeltaHawk diesel is available in 160 to 200 hp outputs putting it square in the middle of competition with aviation engine giants Lycoming and Continental. As we discussed with the Gemini diesel engine the primary benefit to running a diesel in a light aircraft is fuel availability. In remote parts of the country or world finding 100LL (low lead) Avgas may be difficult. The ability to run diesel or Jet-A makes fueling your engine a much easier and potential cheaper task.
Fuel consumption in aircraft is not measured in miles per gallon, rather in gallons per hour at a specific power setting. A typical power setting of 75-percent draws eight gallons an hour through the DeltaHawk putting it right in line with the equivalent output O-360 Lycoming gas engine.
The orientation of this engine can be selected for weight and balance, or packaging limitations. The V configuration can be inverted into an A thanks to the inverted dry sump oiling system. A type of system that is generally used in aerobatic aircraft to maintain oil pressure at unusual attitudes. While not a dynamic system allowing inverted flight the DeltaHawk can be retro fitted for either engine orientations if the customer desires.
To make sure this air stays dense enough for efficient power the DeltaHawk has redundant forced induction systems. A single turbocharger feeds into a roots style supercharger. Other selling points include titanium connecting rods, a forged crankshaft, and intercooling to keep the air charge cool.
This engine is a clever and desirable alternative to the widely used aircooled alternatives, and is being viewed for uses in applications including blimps, UAVs, and even ground power units. According to Doers, “We are going to be doing a six-cylinder and eight-cylinder to take us on up to the 250 hp, the eight-cylinder goes up to about 420 hp.”
We are going to be doing a six-cylinder and eight-cylinder to take us on up to the 250 hp, the eight-cylinder goes up to about 420 hp. -Doers
In an update from this 2010 video DeltaHawk announced last month that certification and shipping of newly refined engines will begin summer of 2016 according to Dennis Webb of DeltaHawk. The refined engine will be able to run on four fuel choices; Jet-A, JP-8, JP-5, or diesel. Those of us at Diesel Army are excited to see new applications and innovative uses for diesel and anticipate hearing some diesel in the sky.