The Small Bleed-Off Gas-Turbine Engine

The need for a small bleed-off gas-turbine engine arose when the large turbojet and turboprop aircraft engines were introduced into military service. The problem of starting turbojet and turboprop aircraft engines became more acute as the starting power requirements began to exceed the practical weight and size limits of electric starters. As a result, development of a pneumatic starting system was undertaken. To make the low-pressure air starter practical, it was necessary to have a small, lightweight source of compressed air. The small gas-turbine bleed-off compressor unit was developed for this purpose. This paper describes the development procedure and details of this type engine as it now stands. So far only a few thousand units have been produced, but cost reductions are expected as use for these small gas-turbine engines increases.