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Vacuum Failures Can Hurt Or What I Learned Reading ASRS Reports

by H. Dean Chamberlain
Reprinted with permission from FAA Aviation News

Are you prepared for a vacuum failure? If you were asking yourself what is a vacuum failure, I would guess you are not ready for one. Recently, in reviewing material about new technology aircraft and their various types of electronic display panels, I wondered how many of today's pilots practice flying the new "glass cockpit" aircraft using their backup instruments. This led to the question about how many pilots of traditional aircraft practice flying needle, ball, and airspeed.

Do we even need to practice flying with backup instruments? Or is this one of those instrument flying skills that is going the way of knowing how to fly a non-directional beacon (NDB) approach in today's world of GPS approaches and multi-panel displays? Based upon some of the information I received from one of the leading makers of vacuum-related equipment, this company says that, in my words, flying with anything less than dual vacuum systems is a hazardous operation. The fact that thousands of pilots have flown thousands of hours for decades with only one vacuum system would dispute this idea. So the issue then may be one of product liability rather than operational necessity. But, I would also bet that many of those pilots flying single vacuum systems were like an old U.S. Air Force colonel I once knew. When he wanted to practice instrument flying with a safety pilot, his idea of practice was to fly using only needle, ball, and airspeed. For him, if he ever had a real vacuum failure and had to use his backup system of needle, ball, and airspeed, this would not be an emergency situation for him, but rather just another opportunity to practice his basic instrument skills.

But whether you fly an aircraft with one or two vacuum systems or have one of the various alternative vacuum backup systems or have an electrically powered artificial horizon as a backup, the question remains, are you proficient in the use of whatever instrument backup system you have onboard your aircraft? Can you fly your backup system to approach minimums for your airport of intended landing or do you give yourself a way out by setting higher personal minimums for yourself?

I wanted to see what pilots had to say about vacuum system failures, so I used the Internet to search National Aeronautics and Space Administration's (NASA) Aviation Safety Reporting System (ASRS). I was surprised at the results my search request for "Title 14 Code of Federal Aviation Regulations part 91 general aviation aircraft failures in instrument metrological conditions" produced. While I was expecting to find a few reports dealing with vacuum pump failures, I found more reports about electrical failures, generator failures, and more surprising, autopilot failures resulting in altitude deviations, tracking problems, and loss of control.

In reading the narratives describing the reported incidents, there seemed to be two common themes repeated throughout the many reports. First, some of the pilots were slow in detecting the loss of navigation equipment or control equipment, which compounded the problem. The second group, as noted in one report, failed to see the "big picture" of the incident. In one case, once the aircraft situation was under control, rather than land in visual conditions when able, the pilots continued their flight in IMC conditions to their home airport. In the report, it was said their continued flight was a result of "get-homeitis" rather than based upon good decision-making.

In summarizing a few of the reports, it is important to always fly the aircraft when something happens. Having a backup handheld radio or GPS can keep you communicating and navigating when your electrical system dies. Being able to quickly detect equipment failures by having a good instrument scan may keep you in control of your aircraft. When flying single-pilot or at night or when weather conditions are down to minimums, you need to have a good divert plan and have your backup gear out and ready to use. Finally, I think good judgment is important when dealing with any emergency situation. Flying past a nearby acceptable landing site in visual metrological conditions while you are in the clouds dealing with an in-flight emergency may not be the best example of good decision making.