Waypoints: New options can save lives

Examples of how ancient technology fails and leads to death continue to pile up. Vacuum pumps and mechanical gyros are two of the weakest systems on our airplanes. Dry pneumatic vacuum pumps literally destroy themselves on purpose, the erosion of their graphite blades a means of lubricating the pump. Does this seem like a positive design feature? Can’t we do better? We can, but for airplanes with hull values of less than $50,000 or so, pilots are understandably reluctant to spend $15,000 to $20,000 on a glass panel upgrade that replaces the mechanical gyros (and thus the need for the vacuum pump) with a solid-state attitude and heading reference system (AHRS).

Mechanical gyros are truly mechanical marvels. The air drawn through the instrument by the vacuum pump causes the gyro to spin at tens of thousands of revolutions per minute—and it does so for hundreds of flight hours, through turbulence and changing attitudes and G loads. But given the complexity and delicate nature of such gyros, it’s no wonder that they eventually fail—often without warning, and sometimes at the worst possible time, when a pilot is in instrument conditions. Sometimes it’s the failure of the vacuum pump itself that leads to the loss of the gyro information—again, usually without warning.

We all learned to fly “partial panel” when in instrument training, and we’re supposed to maintain that skill, but let’s be honest: It’s a tough skill to maintain and when you dust off those skills in actual instrument conditions—often close to the ground on an instrument approach in rain, turbulence, and sometimes darkness—pilots frequently fail at the task. The penalty for failure is severe: loss of control and death for all on board.

These are not hypotheticals. In May 2016, a Beech Bonanza crashed in New York when its 4,000-hour, airline-transport-rated pilot lost control after his vacuum pump failed, leading to gyro failure. He was at 7,000 feet in visual conditions, but his destination was in instrument conditions. Poor handling by air traffic control contributed to him being vectored into instrument conditions, with the predictable loss of control. All three on board died.

In December 2012, the gyros in a Piper Cherokee failed as the pilot was approaching Fayetteville, North Carolina. The pilot maintained control for many minutes, communicating with ATC frequently. At one point he asked to go to his alternate, which was in visual conditions, but a controller offered him a chance to try the approach one more time using no-gyro vectors. In the end the pilot lost control, crashed, and died.

Overhauling a mechanical gyro and replacing a vacuum pump each costs of hundreds of dollars. Both come with warranties of 90 days to maybe a year. Either might serve faithfully for years, depending on usage and environment. But because of their mechanical nature, they will fail. Solid-state AHRS have a much higher mean time between failure, and modern glass displays are very reliable—and expensive.

Thus the need for lower-cost alternatives, which are common in Experimental airplanes. Recognizing the need for more cost-effective solutions, AOPA and others in the industry have been urging the FAA to create new certification pathways to move lower-cost gear used safely on Experimentals into legacy airplanes. Dynon and Garmin both introduced such products in 2016. The Dynon D10 and Garmin G5 solid-state digital attitude indicators both include internal battery backups. And either can be had for about $2,200. In some aircraft, installing one can allow for the removal of the vacuum pump, eliminating an ongoing overhaul or replacement expense for the pump and attitude gyro.

Expect more options this summer, including non-TSOed autopilots. A team is working to develop an STC to install the non-TSOed Pro Pilot model autopilot from Trio Avionics into Cessna 172s and 182s, with more models to come. More details should be available by the Sun ’n Fun International Fly-In and Expo in April.

Cooperation by the FAA and innovation by manufacturers can help drive down costs and improve safety in the legacy fleet—old airplanes with a lot of life left in them.

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