By Peter Conant
The first time I lost my attitude indicator (AI) was on a practice ILS approach in IMC with an instructor soon after I had passed my instrument flight test. I was suddenly seeing the instruments wandering away with absolutely no clue as to what I should do. Chasing the indicator, trying to get back to level flight, watching the turn coordinator going crazy — I was in way over my head. It was a supremely frightening experience, watching helplessly while the airplane entered a spiral dive and plunged toward the Earth.
My instructor calmly turned off the simulator and said, “Your scan should always include the vacuum pump. Gyro instruments only work with vacuum and you completely missed it when I failed the pump.” Feeling rather stupid, it was nonetheless a lesson I have never forgotten.
I still fly older planes with individual round “steam” gauges and, I am proud to say, not once have I forgotten to notice the vacuum gauge, even in VMC conditions. Some 20 years ago, I was helping ferry a Cherokee Six from Massachusetts to Greece and lost the AI for real en route to Marathon from Corfu. In VMC conditions this is not much of a problem, except the sight of the indicator heeled over at a 50-degree bank was hard to ignore. I placed a 3-by-5 card to cover the indicator to remove it from my scan, and we rumbled along north of Athens to complete our final flight of a seven-leg journey.
Another partial panel failure for real happened while departing Montgomery County Airpark, Maryland, in an old Cherokee Six en route to Norwood, Massachusetts. I was in and out of clouds for most of the climb when the directional gyro (DG) started spinning. There was no doubt this was an instrument failure, looking like a blender set on high speed, and I had a hard time ignoring it (no 3-by-5s). I thought about turning around, but then reasoned that I had a compass and also a Northstar M3 GPS for course guidance. The M3 does not have a moving map, but I was reasonably experienced with comparing the digital readout of “direct track” to the “actual track.” I never notified ATC about the situation and, as it turned out, never needed to. Descending through the clouds with no DG was a little out of the ordinary, though.
One of my first instructors once told me, “Humans made these instruments and they will break at some point.” As we all know, the failure rate for TAA glass-panel cockpits with no moving parts is of course much better, and the instruments themselves are easier to read. Who doesn’t love a full-screen attitude indicator? I now have a Garmin 696 portable unit that I fly with everywhere. The 696 has an electronically generated panel, and I display it above the moving map. I don’t think it has AHRS (attitude and heading reference system) capability, but I’m happy for the backup. I’ve also yet to hook up the 696 to my Garmin GDL-39, which should give me traffic and weather. I was reading the other day that the GDL-39 “3D” has an AHRS function but maybe not for the 696. I’ll be reporting on that combination in the future. Right now, I think glass cockpits are great and will be looking to upgrade my 1969 Beagle B260 geared twin-engine leviathan as money and time permit. But I’ll be glad to have those backup “legacy gauges” on the copilot’s side and monitor the vacuum indicator over there.
So, how do you prepare yourself for a glass-panel failure? What can you expect to fail? Do you practice with parts of the PFD covered, or you just simply assume the entire screen would go dark? We can safely say that there is no vacuum gauge to be included in your scan anymore, but humans still made these instruments and they may still break at some point.
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