Heart of Glass

Instrumentation is the pilot’s connection to their place in the sky. Without it, you might as well be flying blindfolded.

By Chris Buchanan

Images: Aeronautical Aviation

Veteran Concorde Captain John Hutchinson was interviewed on video taking the viewer on a tour of the supersonic airliner’s flight deck. Instrumentation on this highly sophisticated and technologically advanced aircraft was solely analogue – no GPS or navigational aids, no weather radar, just the good old fashioned basic six instruments, plus a bank of engine dials, relaying vital information to the two pilots and flight engineer.

“This is a proper flight deck. None of this poncy glass cockpit rubbish. These are proper instruments with needles and dials,” he quips in his introduction.

If you’re fortunate enough to purchase a new aircraft, the flight deck will most certainly be the “poncy glass cockpit rubbish” Hutchinson refers to with, perhaps, vital analogue instruments as backup – horizon, a compass, air speed and altitude.

Technology has taken what was traditionally relayed on six separate instruments and put all the information on a screen. Poncy it might be for diehard aviators like Hutchinson, but for avionics expert Clinton Carroll, owner of Aeronautical Aviation, it’s helped to make aviation more accessible and, ultimately, much safer.

Navigation and situational awareness, before the advent of GPS, were communicated via air pressure, gyroscopics and radio beacon signals. While air pressure and gyroscopics still play an important role in terms of air speed, altitude, heading and horizon, GPS is now the navigation standard in modern avionics and central to the glass cockpit.

“Traditionally, it was intimidating having these six instruments giving me this information I need to navigate with,” says Carroll. “With the cockpits we’re putting into these aeroplanes now, I can be in the cloud, see nothing out of the window and have rain around me, but I’ve got these (what I like to call) TV screens sitting in front of me and I can see through it all. I can see everything around me that I can’t see through the windshield.”

He says the situational awareness and safety aspects that have come into avionics over the past 20 years are mind blowing. Being able to put 3D terrain onto your artificial horizon in front of you that will change colours and that will give you warnings way before you are close to terrain, is now readily available technology.

From an ease of use and ergonomic advantage, the basic six, that classic instrumentation view, is now a “one screen replaces all”, says Carroll. Redundancy in a standby unit is mandated so you must have, in the event of a screen dying, airspeed, attitude, altitude and direction as backup.

“The advantage, when you’re doing an I.F. scan, to see where you are and what you’re doing, is that it’s all concentrated in one picture in front of your eyes.”

Solid state

After qualifying as an instrument technician, Carroll was fascinated by and specialised in gyroscopics and says the gyroscopes he worked on were the size of a football. These days, he says, the entire unit is housed in a box the size of a matchbox. “We’ve moved from technology with moving parts to solid state and I believe solid state is better because it’s not affected by hard landings or turbulence and its accuracy is in microns. If you were flying one degree left bank on an old artificial horizon, you wouldn’t really notice it. Now with digital equipment, the auto pilot reacts to that half a degree where it only used to react to one-and-a-half degrees.”

For Carroll, solid state means everything is so much more accurate and precise than it used to be.

Another knock-on effect is the reduction of maintenance on aeroplanes. Carroll says these systems are not failing and jokes that he’s doing himself out of business because the avionics no longer have to be repaired. “It’s solid state and the days of an apprentice sitting over a bench and overhauling an instrument are long gone.”

As an example, older, remote gyroscopes would sit in the nose or the floor of the aircraft, moving left and right, feeding outputs through synchros and servos to an indicator. The gyroscopes were then replaced by laser units – a triangulated laser beam measured with speed and wavelengths – feeding outputs in the same way. Now it’s a solid state accelerometer that picks up the smallest of movements, detected by the aircraft’s systems instantly.

Keep the motor running

But modern avionics is not only about situational awareness, it’s also about performance and vital engine information displayed on the system.

“Instead of having an RPM sensor, you pick up on the magnetos themselves giving you a more precise RPM indication,” says Carroll. He’s a big advocate of engine trend systems which, when fitted to an aircraft, can immediately show that the engines have been set up incorrectly. He says the basis of that comes from poor indication, not poor maintenance, with the engines having been set up on old mechanical instrumentation. Extreme digital accuracy gives aeroplanes better performance.

Exhaust gas temperature (EGT) and cylinder head temperature (CHT) are now measured on each cylinder, enabling early detection of individual cylinder problems, prolonging engine life and reducing engine failure through diagnostics.

Out with the old?

Carroll believes pilots need to understand the basics of an old airspeed indicator and of an old altimeter because they will come across that technology sometime in their careers. The glass cockpit is the evolution of the old systems in both sensors and displays but the reality is that your CPL exams still cover gyroscopics and airspeed indicator instrumentation.

In the Aeronautical Aviation apprenticeship programme it all starts with the basics, says Carroll. “Starting with the basics, as we are when we’re born, we need to learn to walk before we can run, I believe the same goes for pilots and for technicians.”

Do you agree with John Hutchinson and think glass cockpits are poncy or are you, like Clinton Carroll, all for technology and the evolution of avionics?