Scanning the Glass

In a conventional cockpit, the pilot can scan the inverted V (below)--attitude indicator, vertical speed indicator, and turn coordinator--to determine trend of motion. In the glass cockpit, the PFD's trend indicators provide that information.

"Technology simplifies that which was complex and complicates that which was simple." I don't know the origin of that statement, but its truth cannot be denied. This relates to a question that I am frequently asked: "Will my instrument scan work in a glass cockpit?" Most pilots now have an awareness of glass-cockpit technology because of the numerous advertisements, articles, and light airplanes produced with that equipment.

In 1960 I was taught elementary instrument flying using the needle, ball, and airspeed method. In 1965 the U.S. Army taught me the U.S. Air Force method of primary and supporting instruments. This method, supported by the FAA, is currently taught in most general aviation flight training programs. When the Air Force and the U.S. Navy transitioned to jets, however, the control and performance method was taught.

In 1980, I developed a four-step scan procedure to eliminate the frustration that was experienced by students and instrument-rated pilots who did not fly full time. All of these scan techniques evolved as technology evolved. Even so, they still contain a certain degree of commonality that is directly applicable to the glass cockpit.

My first exposure to this technology occurred when The Boeing Company introduced the Boeing 737-300 and 737-500. I'd been flying conventional-cockpit Boeing 737-200s, and when assigned to a one-week training class for the new airplanes, my immediate thought was, Happy days are here again, because this will be a one-week party. I only have two instruments to scan, the primary flight display (PDF) and the multifunction display (MFD). I'll spend most of my time enjoying extended happy hours at the local watering hole.

That party never occurred, because the equipment change was frustrating, to say the least. Scanning analog instruments, which I'd been doing for years, was routine, and it was very easy to note undesired trends and make the appropriate corrections. In fact, a lot of eye movement was not necessary. I could easily monitor the entire six-pack--the six primary flight instruments--which were always in my field of vision.

This was impossible in the glass cockpit. I had to read specific numbers and interpret colors. Initially, my deeply instilled scan habits were of no use, but they did resurface after I had completed the training program unscathed and flown the airplanes for a few months. It takes time to become accustomed to the new technology, but new indicators such as trend vectors for airspeed, altitude, and heading are very useful. These snakes (lines or arcs) come out of their hole in the ground (the related readout) and expand and contract to show what that indication will be in six seconds, based on what the airplane is currently doing.

My scan system, like most others, is directly applicable to the glass cockpit, but it becomes simplified--which is always good news for any procedure.

Step one is attitude, power, and trim. You set the appropriate attitude and power for the maneuver in question and rough trim the elevator as necessary to minimize control forces. Everyone who teaches or has taught instrument flying knows that this is the first step. Obviously, it is directly transferable to the glass cockpit.

Step two consists of two parts in a conventional cockpit, or one part in a glass cockpit. You scan the inverted-V, which consists of the attitude indicator, vertical speed indicator, and turn coordinator, to determine trend of motion. Is the airplane flying straight or turning; is it climbing, descending, or flying level? This is qualitative information. You're not concerned with numbers, only whether or not the airplane is doing what you've asked it to do during step one. This part is directly transferable to the glass cockpit. However, instead of a turn coordinator, the glass cockpit has a trend indicator--one of those useful snakes--that indicates rate of turn.

The second part of step two requires you to validate the attitude indicator while scanning the inverted-V. In a conventional cockpit, you compare the electrical system's bank information (turn coordinator) with the vacuum system's bank information (attitude indicator). If both agree, all is well. If not, you must check bank information that is generated by another system to resolve that disagreement. The Earth's magnetic field and the magnetic compass can resolve it; however, you could also check the vacuum system gauge, and, if the system is working, use the heading indicator to resolve the disagreement.

At the same time you are comparing the static air system's pitch information (vertical speed indicator) with the vacuum system's pitch information (attitude indicator). If both agree, all is well. If not, you must check pitch information that is generated by another system. Your only option is to use the alternate static air system and the altimeter. You cannot use the vertical speed indicator, because it may be the problem.

The pitch situation is not as critical as the bank situation, because failure to detect a conflict with bank information can quickly lead to a graveyard spiral. In that case, the airplane gets into a steep bank, airspeed quickly increases, and the improperly trained pilot hauls back on the yoke and overstresses the airplane.

In the glass cockpit, validating the attitude indicator in the manner I just described is not necessary, because all such airplanes have a standby attitude indicator. That makes it very easy to determine if a pitch or bank problem exists. Many glass-cockpit airplanes are all-electric, but those airplanes usually have at least three power sources for the PFD. Some glass-cockpit airplanes, however, still use a vacuum system for the standby attitude indicator.

I heard that someone once tried to certify a glass-cockpit airplane without a standby attitude indicator. That may happen as technology advances, but it doesn't make sense today. The airliners that I flew had two PFDs and a standby attitude indicator. Yes, they were all electric, but those airplanes had multiple power sources--as do today's all-electric light planes.

Step three of my scan requires you to look at the primary instruments. Now, you are looking at the numbers, quantitative information. There are always three such instruments, one each for pitch, bank, and power. This step is directly transferable to the glass cockpit.

I cannot deviate too far from commonly used terminology, but the term primary instruments is a joke. There is nothing primary about them. Pilots who make these instruments their first priority are making a horrendous instrument flying error. These instruments are tertiary, the third priority, plain and simple. Most instrument training manuals contain tables listing the primary instruments for various maneuvers. That's nice for explaining the concept, but memorizing that information is not required. Keep it simple. Just ask yourself what numbers you are trying to maintain based on air traffic control's instructions, your charts, or your own personal desires. Do that, and you'll automatically be looking at the primary instruments.

Step four of my four-step scan procedure requires a circular scan where you monitor all instrument indications using a circular scan pattern and fine-trim the airplane for hands-off flight. This is the scan that you use whenever the airplane is in stabilized flight, which, except for training, is 90 percent of the time. This step is directly transferable to the glass cockpit; however, it slows down somewhat because of the digital presentations.

When I started the airline's glass-cockpit class, our fleet manager greeted us with this statement: "My pilots are going to know every aspect of this equipment." And that, my friends, was an incredibly stupid philosophy, as the airline soon found out. You must master this equipment one step at a time, starting with a basic understanding that will allow you to fly the airplane safely.

I spent several years as a check airman, a title that has many variations in the airline industry. At my airline, check airmen checked nothing. That function was performed by management pilots. We did the flight training for new captains and first officers after they completed simulator training at our training center.

My philosophy was this: The first training priority was to ensure that the new pilot was comfortable hand-flying the airplane and understood its personality--the tricks of the trade for optimum performance, so to speak--before we worked on automation and the glass cockpit's supplemental capabilities. I quickly developed a critical rule that everyone must follow when using this equipment: When hand-flying the airplane, you can only use the PFD and the MFD's moving map. Nothing else! I have flown three different types of glass-cockpit light airplanes, and I can assure you that the foregoing rule is absolutely applicable. To use any other glass-cockpit element, the autopilot must be engaged.

Please observe that I'm relating what occurred with a two-pilot crew. That should alert you to the critical importance of the autopilot rule in a single-pilot cockpit, and the pilot of a glass-cockpit aircraft must be the master of the autopilot. So, welcome to the future as a general aviation instrument pilot. Here are your new proficiency requirements: instrument flying, hand flying, autopilot operation, and glass cockpit utilization.

If you fly only once or twice a month with this equipment, you have compromised flight; you must fly frequently to stay proficient. Fortunately, interactive computer simulation programs for using the glass cockpit's features are available. Such must-have training aids are a tremendous asset for maintaining that proficiency element.

Ralph Butcher, a retired United Airlines captain, is the chief flight instructor at a California flight school. He has been flying since 1959 and has 25,000 hours in fixed- and rotary-wing aircraft. Visit his Web site.

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