This paper presents the results of Phase II of the Hydrogen Enrichment for Aircraft Piston Engines Program. The overall program, and specifically the Phase I results, have been discussed by Menard et. al.
The hydrogen generator flight model and the engine were installed in the flight configuration of the flight test stand. Fuel economy measurements and limited emission measurements were obtained on the flight test stand, in order to spot check the dynamometer results and the potential for reduced emissions. It has become evident that with proper timing, one can run the engine ultralean (fuel/air ratios as low as 0.05) with gasoline only during a steady-state operation without sacrificing performance (except for critical altitude). Under such conditions, fuel economy improvements of up to 20% have been obtained. The emission measurements conducted so far appear to indicate that, if these techniques can be implemented during taxi, idle, and approach, it may be possible to meet the Federal Emissions Standards.