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Optimising the engine size to the multi-engine helicopter's needs is a difficult process which has traditionally been carried out through the mechanism of the engine rating structure. However, the rating structure has many limitations and does not allow the best potential use of the engine to be realised in service. The introduction of the micro-processor based Engine Monitoring System permits a re-evaluation of the rating structure and also the presentation of limitations to the pilots. By using EMS it should be possible to achieve a better relationship between the demonstrated capability of the engine as shown in the Qualification Programme and the authorised release for in-service use. This may be regarded as a first step to be followed later by a change of the qualification test to a more representative form with the EMS giving a more tangible link between bench test and customer operation.

The Texas Project was a multi-year study of aftermarket conversions of a variety of light-duty vehicles to CNG or LPG. One aspect of this project was to examine the factors that influence the economics of fleet conversions to these alternative fuels. The present analysis did not include longer-term effects (such as possible increases in exhaust system life or increases in tire wear). Additionally, assumptions were required to estimate the costs of repairs to the alternative fuel system and engine. Other factors considered include conversion cost, fuel prices, annual alternative fuel tax (as applied for the state of Texas), annual miles accumulated, and the percent miles traveled while using the alternative fuel for dual fuel conversions.