Changing market conditions for light aircraft have led to the clear need for a range of engines that burn the same fuel as jet aircraft. Most light aircraft have old technology engines that must currently use leaded gasoline, Avgas, an increasingly expensive and outmoded minority fuel, unattractive for oil companies to produce in the long run. A piston engine using jet fuel typically reduces light aircraft operating cost by around 30% in most countries, except the US where leaded gasoline is presently positioned at a similar price point to jet fuel.

Aircraft engines must score well in a number of key areas to achieve sustained success:

  • Power to weight ratio
  • Simplicity of installation and maintenance
  • Flight cycle fuel consumption

New engines that have fallen short in these areas have been unsuccessful.

Current light aircraft aviation fuel, Avgas, is a low lead based fuel, which is coming under increasing environmental and regulatory pressure, even in markets where the price differential is small.

In addition there are key emerging markets, such as India and China, where there is no existing infrastructure for Avgas, and it is unlikely to be developed against increasing environmental concerns over a lead based fuel, especially if a viable diesel or Jet-A1 solution exists, for which there is already the required infrastructure.

The new WAM engine concept allows the use of both diesel and jet fuels. This new technology brings numerous benefits while weighing no more than traditional Avgas burning engines. WAM engines are specifically designed to run on jet fuel and use new (to aircraft) diesel technology that avoids the technical compromises inherent in more conservative approaches. The result is an engine that exhibits excellent power to weight characteristics, and is ideally suited to the requirements of a large range of light aircraft.

The WAM engines are capable of running on road diesel as well as bio diesels, and the company is currently working with partners to assess the impact of wider use of bio diesel in light aviation.

WAM technology offers simple installation and maintenance with no reliance on electronics, delivering significant reduction in time, and hence costs, for both these operations. WAM engines also exhibit strong flight cycle fuel consumption characteristics. Compared with existing conventional engines, the WAM equivalents offer demonstrated aircraft range improvements of approximately 30%.

WAM engine technology and associated tooling and production methods are designed for low parts cost, combined with medium volume production, up to several thousand units per annum. This has been achieved by applying modern automotive design and production techniques aimed at meeting very specific aircraft engine customer and regulatory requirements.

The first engine to be produced was the WAM 120 for the kit builder market, producing 120hp. The WAM 100 LSA, three cylinder engine producing 100hp was manufactured for the emerging LSA market. A further refinement of this three cylinder design is the WAM-125BB, initially producing 125HP for approximately the same weight.

Using the same core design features and applying these to the four cylinder model, the WAM-167BB range of engines are now running successfully on the test dyno, with initial power outputs from 167hp with potential for up to 200hp

Technological Advantages

The inverted inline direct drive CITEC design has allowed an excellent power to weight ratio, while maintaining simplicity giving key benefits in cost and reliability.

The inline drive, achieved by the low revving power band, avoids the weight and complications of a reduction gearbox found on many other designs.

The inverted design allows for a compact installation, with the thrust line ideally suited to many types, previously designed for a more traditional flat four design.

The mechanical fuel pump and regulator design ensure simple operation without the need for any electrical systems or backups.

Conventional AVGAS engines have significant regular maintenance costs related to the magnetos, at each annual and every 500-600 hours. These are eliminated in the WAM CITEC design.

The installed weight of the WAM-125BB is approximately 130kgs, with a maximum power output of 125 hp. This combined with the improved fuel consumption and hence range gives favourable useful load figures even against the lightest avgas fuelled engines such as the Rotax, with significant gains against traditional engines such as the Continental O-200 / O-235.

The installed weight of the 4-cyl 167HP, including VP governor and prop is 158kg - under 350lbs. Without the prop, governor, silencer, but including radiators, oil and water etc it is about 138kg - or 10 kg lighter than the dry weight of an IO-360 by comparison.

The WAM-125BB operates with SFC of 240gm/kW hr and lower - breaking the psychological 0.400lb/HP hr limit. This is relatively close to the levels achieved with a more complex DI engine, however with a significant reduction in weight and therefore overall consumption. The initial testing of the 4-cylinder has shown the SFC for the WAM-167BB will be the same or better due to economies of scale, with the same basic cylinder assembly.