Rob,

I agree with your comments. MTBF for vacuum pumps seems to be about 500 hours
per the Parker SB's and SDR info.

As to TCAS and midairs-- there are about 10-20 midairs a year. Half of those
occur in the pattern on final approach at less than 500' AGL. TCAS is not
going to prevent those.

Assess your risk-- flysmart.

Jeff Edwards