Right after I posted my last blog on the problems with aging mechanical instruments, I received more than a few emails telling me that I was wrong. Thanks for that, by the way.
Well, truth be told, I was about half-wrong. In many instances, issues with mechanical instruments aren’t the fault of the units themselves but are symptoms of a bigger problem: the aircraft’s vacuum system.
Failures of aging engine-driven vacuum pumps and the related plumbing are the root cause of way too many problems with everything from attitude indicators to autopilots. In case you’re new to avionics and instruments, attitude indicators, turn coordinators, and heading indicators are all vacuum-driven instruments.
If the aircraft has an attitude-based autopilot, it’s getting its information from the same vacuum-driven instruments. So, when the vacuum system or instruments go south, the autopilot does too. If there’s one thing that makes any instrument pilot’s blood run cold, it’s the thought of a vacuum system failure in IFR conditions. That’s what nightmares are made of.
Thankfully, in today’s world of solid-state avionics, it’s a lot easier and more affordable than ever to replace all of your legacy vacuum-driven instruments with digital units. One caveat being if your aircraft has a pneumatic de-icing system, you may well be stuck with the engine-driven vacuum system. But at least you can eliminate it as a cause of instrument issues.
New-generation digital units like the Aspen Evolution, Garmin G5s, and GI 275s, among others, are quick and cost-effective replacements for your legacy mechanical instruments. In fact, if you sit down and do a cost analysis, when you factor in the price of troubleshooting, repairing, and/or replacing your aging vacuum pump and plumbing, it’ll probably cost you less, in the long run, to change it all out for solid-state instruments.
You’ll not only save a lot in ongoing vacuum pump maintenance; you’ll be adding untold amounts of safety, capabilities, and reliability to your aircraft.
But what about your autopilot, you ask? No problem. Many of the units have built-in, or at least optional, attitude and heading reference systems (AHRS), which will provide the information the autopilot needs to keep the blue side up.
Or, if you really want to take a step into the 21st century, there are plenty of new-generation digital autopilots to choose from. Check out my earlier blog: Oh, b’gosh; we’re not at Oshkosh.
I know when you think about removing a complete vacuum system, it can be a bit overwhelming. If you have any questions, feel free to give me a call at, 863.709.9714 (x 112). If I don’t have the answer, we have a great staff of engineers who know exactly the best solution for you and your aircraft.
Until next time, fly safely and have fun,