Advanced Pneumatic Start Systems for APUs

Pressurized Air Start System (PASS) technology offers an alternative to conventional electric or hydraulic starting systems for APUs. The major advantage of the PASS system over other systems is that it can provide effective starts at temperatures as low as minus 65F. But what penalty must be paid in order to achieve this benefit of low-temperature operation? In this paper, we review the characteristics of some real-world PASS systems compared to electric or hydraulic systems. We then pose some hypothetical questions that help us generalize the comparisons. From these generalized comparisons, we conclude that the PASS system is usually lighter than alternative approaches, but that work is required to improve the volume of PASS systems. Finally, a comparison among start systems is made in this paper based on our prediction of how these start systems will evolve by 1995.