If you ask a roomful of pilots how many have suffered a vacuum pump failure usually one third to one half raise their hands. When asked how many have had things go South in IMC the number is much smaller but still significant. Anyone who has ever had to fly partial panel in the clouds will not soon forget the experience.
If you’d like to hear how the story unfolded for a pilot down in Florida recently, watch this real pilot story. You’ll see first hand what worked well and what the pilot would have done differently. We are all “supposed” to be able to fly partial panel approaches under Part 91 ( personal) flight operations. However, I find it intriguing that the airlines and most corporate flight departments who operate with two person crews that fly more in a month than some of us do in a year, don’t put their eggs into that high-risk proficiency basket.
Their aircraft are all equipped with backup systems that pretty much eliminate all the heroics associated with a single point failure. Dry vacuum pumps are not especially reliable and even when the mandatory replacement schedules are adhered to religiously that is still no guarantee, as the real pilot story above shows.
Here’s the real solution if you fly much IMC or at night: invest in a backup power source and/or some alternate instrumentation. This does not relieve you of the responsibility to practice partial panel occasionally but it’s very comforting to know that if and when it happens to you, the belt and suspenders on a flight-critical system will be far superior than depending on the weakest link. If you like to learn more on the strengths and weaknesses of your vacuum system go to http://flash.aopa.org/asf/pneumatic_systems/.
A. Don’t do much IMC or night, so not an issue
B. I have a back up system
C. Backup is not needed – you’re supposed to be able to fly partial panel