A PFD Takes Flight

Avidynes Entegra primary flight display is easy to use and has a stunning display, not to mention a price to match.

For many experienced airline pilots-or at least those whose seniority numbers arent in the high five digits -the glass cockpit has been ho-hum for a while now. The multi-tube glass cockpit debuted during the 1980s and even some aging warhorses like the DC-8 and 727 have been refitted with electronic displays of some sort.

Now its GAs turn. As we reported in the October issue of The Aviation Consumer, at least four companies are well along with development of primary flight displays (PFDs) for light aircraft and a couple of others are expected to soon reveal their own systems.

According to the hype surrounding the introduction of this equipment, PFDs will revolutionize the art of instrument flying and if embraced fully, theyre expected to have a measurable impact on safety, conceivably reducing if not entirely eliminating IMC loss-of-control incidents.

Well believe that when we see it. But we can tell you this: We recently flew Avidynes Entegra PFD in a Cirrus SR22 and if this system represents the future, were intrigued by the shape of things to come. (Well reserve final judgment on this for later; the system is not fielded yet and needs some wringing out by the market before well clear the gantry and launch into unbridled gushiness.)

Entegra: A First
As we reported in the October issue, the S-TEC/Meggitt Magic system beat Avidynes Entegra to market but the Magic isnt a true PFD but rather an electronic rendering of conventional flight instruments. In our view, the difference has a distinction.

True PFDs combine all of the primary flight instruments into a single display, with no need for the pilot to scan elsewhere except for supplemental navigation displays and powerplant monitoring. The Entegra does this.

In the Cirrus iteration-which will be available sometime next year as a $24,500 option-consists of two large flat screens, one directly in front of the pilot, the second occupying the center of the panel. In the Cirrus, the radios and navigators, a pair of Garmin 430s, are installed in a center console by the pilots right forearm.

The left-side screen has the flight display, which consists of a HUD-style attitude indicator topside and an EHSI below. Heading and altitude values can be bugged and the EHSI can be scaled up and down, switched to an arc view and otherwise customized.

The center EX5000 multi-function display has six discreet screens to cover basic navigation, engine monitoring, flightplan/trip, set-up and checklist functions. The EX5000 is also sold separately for installation in aircraft other than the Cirrus. Avidyne retains its line of smaller MFDs, the FlightMax series.

The Entegras two screens are enormous, measuring 8 1/2 by 10 3/4 inches, with pixel dimensions of 800 by 600 and active-matrix displays similar to those used in laptop computers. The screens are so large, in fact, that theres room for little else on the panel.

The required back-up steam gauges- attitude gyro, altimeter and airspeed-are installed on the lower padded lip of the SR22s panel. The SR22 is an all-electric aircraft so all of these conventional instruments are electric, not vacuum. This was deemed a more practical solution for back-up than adding another display, for which theres no room anyway.

The PFD is entirely self-contained, with no remote gyros and only a pitot-static feed and navigation information piped in from the outside world. Its driven by an Avidyne-developed ADAHRS-air data/attitude and heading reference system-which lives in a module about the size of a paper juice box nestled inside the display chassis. Power requirement is 6 to 28 volts DC.

Flying Glass
So much for the technical details. Whats the thing like to fly? In a word, dead easy. (Okay, so thats two words.) But even though we have experience with most of the major GA avionics boxes, getting the Entegra going is somewhat intimidating for the sheer volume of options.

With two GPS sources and two VOR/LOC sources, the variation in set-up and display possibilities is not quite overwhelming, but it takes some non-flying cockpit time to absorb. We were happy to have Avidyne CEO Dan Schwinn and Cirrus demo pilot Jeff Edberg run us through the basics before we took off.

Fortunately-or not, depending on how big a hurry youre in-the Entegra system isnt a kick-the-tires-light-the-fires kind of box. As do all of the ADAHRS weve seen thus far, the system takes a few minutes to initialize after it has been powered up; four minutes to be exact. The wait is required to give the solid-state gyros time to reach thermal equilibrium.

During this time, the airplane cant be taxied or otherwise moved and just as a reminder, the displays are Xd out and an impossible-to-miss flag cautions you to remain still until the system finds itself.

This isnt onerous if youre waiting on a cold engine to warm up but if youre dropping a passenger and want a quick turn, youll have to leave the system running even if the engine is shutdown. Otherwise, when you power it back up, youll have to sit there for another four minutes while it gets happy again.

Since the Cirrus SR22 is an all-electric airplane with two busses and two batteries, its got juice to spare for ground operations with the engine offline. We suspect owners who opt for the Entegra system will put that spare juice to use by routinely turning on the avionics during preflight or running them in hot standby during quick turns.

To avoid gritting your teeth and thrumming your nails on the glareshield while the PFD wakes itself up, a change of habit may be necessary. We would recommend getting clearances and scrolling routes into the GPS while the PFD does its business. As it nears initialization, the Entegra gives a 45-second warning that its about ready and then displays the ADI on top-standard EFIS flying W symbol in white against a blue sky and brown-earth background. A nice detail is a slight whitening hue of blue where the sky meets the brown earth.

As shown in the photos, the screen is split horizontally, with the ADI on top and an EHSI below. The EHSI has white base symbology against a black background and uses other colors-red, green and magenta for other functions, such as active course, the HSIs course indicator and bug indications.

Designers of big-iron glass cockpits have learned that it takes effort to get the colors, symbology and line weights of a PFD just right so that most pilots who use them will find them comfortably readable, without annoying visual glitches.

In our view, Avidyne has gotten this mostly correct in the Entegra. We flew the system in the worst possible scenario-in IMC in the tops of brightly lit clouds-and found that the screen remains clearly readable at maximum brightness. It did pale slightly in bright sun, but not enough to affect readability much.

However, in the Cirrus, the panel is at a greater distance from the pilots eyes than it is in most aircraft. Throughout the flight, we felt a subtle urge to either move closer to the PFD by a foot or six inches or to have the symbols larger and the line weights on course depiction, bugs and numbers to be denser. If this isnt tweaked in some way, we suspect pilots without perfect eyes-and thats most of us-may have some complaints, especially when flying fatigued. We didnt fly the system at night so we cant say if this minor shortcoming is better or worse in the dark.

Those of us used to steam gauges-even sophisticated steam gauges-have grown accustomed to a minimal degree of interoperability between an HSI, GPS navigators and an autopilot. You have to pay attention to whether the HSI is coupled to the GPS or a VOR/LOC source and, if youve got a flight director, you have to tend to setting that up correctly so the command bars make sense. But thats about it.

As the product name perhaps suggests, the Entegra is far more integrated into the navigation/autopilot system than is a standard HSI. This integration is so complete, in fact, that we were happy to have Cirrus pilot Jeff Edenberg in the right seat to run the radios and plug course data into the two Garmin 430s in the SR22s center console.

That left us to fiddle with the Entegras knobs and to puzzle out its considerable featureset. (While we were waiting for the system to initialize, we idly counted the total number of knobs and buttons for the entire avionics suite; it came to 86. Sparse isnt an adjective that comes to mind when describing the control set.)

We wouldnt say the Entegra itself requires intensive training. We found Dan Schwinns 10-minute brief to be a good start but if youre not current and adept with the Garmins and the S-TEC autopilot, the workload can be momentarily overwhelming. Without meaningful input from the navigation system, the Entegra displays only basic attitude information; theres no navigation help.

Avidyne has wisely avoided larding up the Entegra with too many buttons and controls. It has eight keys for primary functions and a pair of knobs on the lower bezel to set course, bug and other numerical values. The knobs have a push-in feature for momentary functions.

On the left side of the screen, the three top-most keys canbe toggled to display numerical output of the two navigators, including frequencies, bearing, distance and ETA to a fix. The third button in this stack is for auxiliary nav input. You can select different values from each of the two navigators, say distance to the airport from one, distance from an off-airport VOR from another. To declutter the screen, you can toggle off these displays entirely.

The bottom key toggles through variations of the EHSI display, to include a standard HSI and an arc view, each with or without a course line moving map in the background. The lower left knob sets the scale on the EHSI and when pushed in, momentarily serves as the setting knob for the course indicator.

On the right side, four dedicated keys momentarily activate the lower knob to set the altitude bug, the VSI bug, the heading bug and to set baro. After a few seconds, this control set defaults to the heading bug.

Pushing the knob in when any of the bug-set keys are active instantly synchronizes the bug to whatever the current value is, thus if youre climbing at 600 FPM and want that as the bugged value, punch the VSI bug key, then push the knob in. Or twist it to whatever value you want.

Flight Dynamics
The most noticeable thing about any ADAHRs-driven display is the lack of delay in response and none of the nervousness that mechanical displays sometimes have. As viewed by the pilot, gyro and heading have almost liquid smooth movement thats easy to interpret.

Although we didnt try any unusual attitudes in the SR22 we flew, we asked about the Entegras limits for gyro tumble. We were told that the solid-state rate sensors can handle rate changes of up to 100 degrees per second without going stupid. Avidynes Schwinn says youd pull the wings off the airplane before saturating the rate sensors with high-G maneuvers.

We thought that the tape-style displays for airspeed and altitude would take some getting used to but theyre natural and easy to interpret. From takeoff until landing, we never referred to the lower-lip steam gauges.

In cruise, the tape altitude value seems to encourage chasing because it displays in 20-foot increments and a high-performance aircraft such as the SR22 will drift off pitch that much in a heartbeat. You simply have to learn to ignore it or just let the autopilot worry about it. (Interestingly, the AP drifts nearly that much, too.)

Compared to a conventional AI, the Entegras ADI requires concentration if all its data is to be absorbed. Fortunately, you can easily control the airplane by ignoring most of it but that defeats the level of sophistication youre paying for in these systems. Operational experience will tell if its a good idea to have so much data plastered on the screen at once.

One thing that requires practice is interpreting the Entegras so-called trend lines, which indicate where the aircraft will be in airspeed, altitude, heading and climb rate in six seconds. These appear as small blue bars extending from the numerical display boxes for each of those values.

The longer the bar is, the greater the trend change. So if you see a blue bar off the scale and downward on the altitude indicator, you know at a glance that youve got a high descent rate and you can input the necessary control to respond to it without thinking about it much.

On the heading indicator, the blue trend bar slides around a curved scale with tick marks indicating half-standard and standard-rate turns. Once you know where to look for it, this sort of display is superior to a turn needle, in our view.

Which is a good thing, because the Entegra system has no turn needle. But it does have an electronic ball, which appears at the top of the ADI as a black trapezoid centered in a white triangle; the bar slides out of the triangle to indicate a slip or a skid.

Because the Entegra system is heavily air-data dependent, it gives a constant real-time readout of true airspeed and groundspeed right on the display.

Further, the system continuously displays a wind vector symbol showing the speed and direction of winds aloft. This appears in the upper left or right of the EHSI as a tiny arrow representing wind direction and a number the velocity.

Course, Traffic, Weather
One trend were not sure we like is the effort to display too much information on the EHSI. To a degree, Sandel does this in its SN3308 EHSI but Avidyne has largely avoided it in the Entegra. Still, when course information and approach fixes are all displayed on the EHSI, its sometimes too cluttery to work well. Avidyne has a solution, however, and it works. You select what the EHSI display is showing with the range/view key and/or scale in or out to make the clutter less noticeable. Also, selecting arc view makes the HSI more readable and either arc or HSI can be set to exclude the moving map features.

A better solution yet is to declutter the EHSI and rely on the larger screen of the EX5000 MFD for detailed flightplan data. You also have the advantage of overlaying weather and traffic information on the course depiction. The EX5000 has more than enough real estate to accommodate this data and its far easier to see the details on the big screen than on the EHSI.

Besides weather and traffic, the Entegra is strongly integrated into the autopilot, an S-TEC System 55 in the Cirrus SR22. This takes some getting used to if youre accustomed to flying the autopilot first and then manually setting up an HSIs course indicator or heading bug to conform with what you want the autopilot to do.

For example, if youre flying a conventional autopilot in cruise and wish to climb on autopilot, youd release altitude hold first then either command pitch up or dial in a specific climb rate in an autopilot equipped to do that.

In the Entegra, most of this happens on the PFD. You bug in the target altitude and the climb rate, then punch the altitude and VS buttons on the autopilot simultaneously.

The autopilot does the rest, including capturing the target altitude and automatically slowing the climb rate as you approach it. (The blue altitude trend line gives graphical confirmation of this.) Using the two-button method described here, the autopilot defaults to a 500 FPM climb or descent. At any time, you can bug in another climb rate and the autopilot will fly it.

We flew an ILS with the Entegra with a combination of autopilot and hand flying. With the EX5000, position awareness is a no-brainer; the course is drawn in large and colorful detail and youd have to be snoozing to lose your place. Using the trend indicators and tape airspeed values, hand flying an approach is also easier than it is with conventional gauges.

Although we didnt particularly care for the localizer and glideslope representation-small, somewhat vague white needles for both-scanning and flying the approach presented no problems. The more we used them, the more we liked the trend indicators for controlling speed and descent rate.

The real workload on an approach is not the PFFD but the Garmins down in the center stack. In our view, thats not a great place to have them with this system in use.

Although theyre readily at hand, looking down to set them up is a considerable distraction from scanning the PFD and MFD. This requires significant head and eye movement at a point where thats the last thing you want to do.

Obviously, theres no room for the navigators in the panel, where we think they belong, so in our dream panel of the future, the MFD will have some kind of touch screen function to run remotely mounted navcomms. After all, with the MFD, you dont really need the 430s relatively stingy moving maps.

Cutting through the hype, are these PFDs really the wave of the future? Or will they end up being just expensive toys for a very few rich pilots who can afford to live on the bleeding edge?

Based on our experience with the Entegra, we think the PFD revolution is inevitable. We commend Avidyne for bringing to market a well-thought-out and relatively mature product with few significant warts. Avidynes Schwinn told us the Entegra has, at most, a 10-minute learning curve and while we found that to be a bit of an exaggeration, an hour of flying with it would get all but the densest pilots up to speed.

For the time being, PFDs of this class will be largely the domain of new higher-end aircraft, such as the Cirrus SR22 and probably Raytheon/Beechcraft products.

At about $60,000 retail, the Entegra will still find buyers among owners of upper end aircraft to whom a $100,000 avionics upgrade is affordable. Weve seen enough of these to realize theres a market out there for big-dollar upgrades.

Although this aftermarket isnt a priority with Avidyne, theyve pledged to support vendors interested in pursuing the necessary STCs. We dont think it will be long before an enterprising shop sees a business in this type of upgrade.

In the longer term, were told that the price of ADAHRS-driven PFDs will probably decline somewhat in the future, although we dont expect them to ever be cheap. (Cheap is less than $10,000.)

Were not yet prepared to crown Avidyne the winner in the PFD race, even though the Entegra is impressive. Chelton expects to have something to show next year and Garmin also has a project in development. There should be plenty of competition in this field.

As well there should be. In our view, theres no question that a PFD simplifies instrument scanning although not necessarily the overall task of instrument flying. Youll still have to know how to keep the airplane upright and on heading while working the radios and the navigation.

A PFD helps the overall process. But at this juncture, it doesnt mean that every average Joe is suddenly a seasoned instrument pilot. If youre waiting for that, itll be a while.

Also With This Article
Click here to view “Checklist.”
Click here to view “Entegra at a Glance.”
Click here to view “How ADAHRS Works.”
Click here to view “Avidynes EMax Engine Monitor.”

Contact- Avidyne Corporation, 55 Old Bedford Road, Lincoln, MA 01773; 800-284-3963; www.avidyne.com. Cirrus Design Corporation, 4515 Taylor Circle, Duluth, MN 55811; 218-727-2737; www.cirrusdesign.com.