‘Trust your instruments’

Pilots have no choice but to rely on the gauges if we want to stay right-side up in the clouds and find our destinations in low visibility. But we also know the vacuum systems that have traditionally powered our attitude instruments are failure prone—and the mechanical instruments themselves have limitations that make them unreliable in extreme pitch and roll excursions. That’s why we’ve come up with elaborate instrument cross-checks and put so much emphasis on partial-panel training.

Now, a new generation of digital, all-in-one attitude instruments has arrived that promises to truly be worthy of pilots’ trust. The AOPA Extra 300L (see “Teachable Moments”) recently had its electro-mechanical gyros replaced by digital Garmin GI 275s at Southeast Aero, and the results are much deeper than the colorful synthetic vision image.

To put these new all-in-one attitude instruments to a strenuous, real-world test, we papered over the airplane’s front canopy so that the front-seat pilot (me) had no view of the outside world at all. Then Richard McSpadden, head of the AOPA Air Safety Institute, put the Extra in a series of progressively more extreme upsets while flying in the unobstructed rear seat.

“Close your eyes and I’m going to put the airplane in an unusual attitude,” McSpadden said. Then, a moment later, “Your airplane.”

Truthfully, I didn’t close my eyes because I was already in a cave of my own making. But the recoveries from nose-low and nose-high attitudes with bank angles of 90 degrees or so were remarkably straightforward.

The GI 275 even draws a picture with a trail of bright red arrows pointing the way to level flight. There’s no real scan involved, either, since airspeed, altitude, and heading all are displayed on the same instrument.

Then McSpadden got more aggressive with pitch attitudes approaching vertical and bank angles in excess of 120 degrees. Still, the GI 275 showed the way back to level flight every time, and my only real decision was whether to fix the pitch or roll problem first. (Personally, in nose-high attitudes, I prefer to let the nose come down to the horizon first and then correct the bank angle.)

During our preflight briefing, we’d decided that if the upset recoveries went well, I’d attempt some basic aerobatic maneuvers under the hood.

Aileron rolls in each direction were a simple flick of the wrist, and the GI 275s weren’t bothered by the Extra’s unusually quick roll rate.

Next, I tried a series of “over-the-top” maneuvers—loops and half-Cuban eights. They looked good on the GI 275, but McSpadden said they were sloppy, with headings straying as much as 20 degrees by the end of each maneuver. The only novel part of flying the figures was that it required intentionally disregarding the GI 275’s recovery arrows, and those things are so prominent and insistent that they gave me a momentary pause before overruling them.

The final under-the-hood maneuver was an upright spin. At idle power, full aft stick, and full left rudder, the Extra obediently tucked into a spin and the GI 275 displayed a 70-degree nose-down pitch attitude and rotation. Opposite rudder and forward stick stopped the rotation after about three turns, and I held the Extra in a nearly vertical dive for a few seconds as airspeed increased, then initiated a normal recovery.

The GI 275 isn’t going to replace a sighting device for competition aerobatic pilots. Looking outside is still more immediate and accurate than interpreting an instrument. But the GI 275 stayed oriented throughout 360 degrees of pitch and roll and showed the way to level flight.

GI 275s are widely used as primary and standby attitude indicators, and some come with backup batteries that keep them going without ship’s power. They rely on GPS for heading information, so it’s likely that sustained inverted flight would block the GPS antenna from reading the satellites that let it know its position. But the instruments didn’t seem to mind having their satellite reception compromised for a few seconds at a time.

As Garmin’s GI 275, less sophisticated G5s, and other solid-state attitude instruments made by other manufacturers get more broadly installed throughout the general aviation fleet, IFR flight training is likely to change. Turn coordinators seem totally obsolete, for example, and using them (along with vertical speed indicators and altimeters) to identify and recover from upsets in the clouds seems to belong to a bygone era.

That old truism about trusting your instruments, however, is becoming truer than ever.

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