What are the odds? I mean one vacuum pump failing is a relatively uncommon occurrence, so having both of them fail is highly unlikely. Unless you consider the fact that both pumps are probably the same age, have almost the amount of hours on them and were built by the same person. Add to that the fact that once one pump fails the other one has to work twice as hard and the odds of a second red light showing up on the instrument panel go from unlikely to likely.
Climbing out of Riyadh I thought we would never get on top of the thick layer of dust and even though we could sort of see the sky at 13,000 feet everything was so hazy we might as well have been in the clouds. On the clime out the tower kept asking me what my altitude was and if everything was going OK. The day before I’d had some problems with the transponder reporting inaccurate altitudes and now ATC was telling me that it was showing that I was descending instead of climbing and over a thousand feet lower than I really was. I finally managed to coaxed the hot Navajo up to 15,000 feet and leveled off. The autopilot wasn’t working and the artificial horizon on Lee’s side hadn’t worked all trip so I was being treated to a day of hand flying on instruments wearing an oxygen mask, always a treat. About 20 minutes before sunset and shortly after we’d passed Bahrain I noticed that the HSI (DG or electric compass) was showing that I was in a turn. That was confusing, I checked the attitude indicator and confirmed that my wings were level and that the plane was still trimmed up. The HSI still showed that not only was I still in a left turn but that it was increasing. That’s when I noticed the second BRL (big red light) on the instrument panel. Crap, I’d lost my last vacuum pump and with it my attitude indicator. Now the only way I had of keeping the wings level and the airplane in control was the old needle, ball, airspeed method. This is essentially an emergency procedure where the pilot uses the combination of looking at the turn coordinator to see if he’s turning and airspeed to see if he’s climbing or descending. The pilot can back these instruments up with the compass and altimeter. It’s considered an emergency procedure because not only is it extremely hard and demanding but if the pilot somehow loses control of the plane it’s unlikely that he can recover from an unusual attitude using only those instruments. Basically not good.
