Biofuels Could Mean Bigger Rotors

Posted by Graham Warwick at 10/30/2010 3:40 PM CDT

Sikorsky has completed a study of alternative fuels and their impact on rotorcraft design and recommended further research into additives and blends for biodiesel and biobutanol to make them more suitable as replacements for jet fuel.

Supported by the US Army, Sikorsky considered a range of alternative fuel options and selected biodiesel and butanol for further study. Both fuels have lower heat content than JP-8 - 8% less for biodiesel and 22% less for butanol - and the study assessed the impact on design of small, intermediate and large helicopters.

Graphic: Sikorsky

For an intermediate helicopter carrying 16 passengers 250nm at 170kt, using biodiesel in place of JP-8 required 2.6% more fuel capacity, for an 11.2% higher fuel weight, 1.7% heavier empty weight and 3.4% higher gross weight. Rotor diameter increased 1.6% and engine power required 3.7%.

Using butanol required 34.5% more fuel capacity, for a 35.7% higher fuel weight, 6.7% heavier empty weight and 10.3% higher gross weight. Rotor diameter increased 5% and engine power 9.3%.

To reduce the impact, Sikorsky recommends further study into additives and blends for biodiesel and butanol. It also recommends defining a propulsion system architecture, and materials for use in the fuel system and engines, that will work with a range of alternative fuels including 100% synthetic biojet, biodiesel and butanol.