Tuesday, July 10, 2007

Flying in a 'lectronic World, Part II

Virtually all aviation GPS equipment manufacturers have failed to acknowledge that pilots fly aircraft in three dimensions, not just two. Granted, low-altitude IFR en route charts, high-altitude charts, and area charts by their very printed-on-paper nature are two-dimensional. Approach charts provide the third dimension (altitude) in a crude way using a profile view. And on non-precision approaches, IFR-certified GPS units seem to have been specifically designed to provide no vertical navigation at all, not even an awareness of step-down altitudes, which was left up to the pilot. But with the new WAAS-enabled G1000, it looks a new era has begun.

Computing accurate rates of descent or climb is a really good job for a computer, especially in single-pilot operations where the pilot has other things to occupy his or her time and where descending too soon, or too rapidly, can be dangerous. The new G1000 lets you enter a desired altitude for each waypoint in a GPS flight plan along and here's the radical part: A Vertical Descent Indicator (VDI) and Required Vertical Speed Indicator (RVSI) will appear on the primary flight display and actually provide vertical guidance based on your current ground speed. This is something that pilots have needed since the inception of IFR GPS and in most units has only been available in a very rudimentary form, usually limited to just one flight plan waypoint. Not any more.

The G1000 flight plan interface on the Primary Flight Display (PFD) is much more simplified than the Multi-Function Display (MFD). As you're creating your flight plan (or when editing an existing flight plan), you may notice that the MFD's flight plan interface on the new G1000 contains altitude fields. Press the small FMS knob, scroll with the large knob to the field where you want to enter a value, then turn the small FMS knob to start entering an altitude or offset.

An annoying feature is that you enter altitudes one digit at a time, starting with tens of thousands of feet: Turn the small FMS knob to set each digit and scroll to the next digit with the large knob. And when you are done entering a value, press ENTER to save the value. If you press the small FMS knob (which I have seen pilots do thousands of times), you'll jump out of cursor mode without saving anything. This is infuriating if you've just invested several seconds entering an altitude. Garmin perfected the same sort of dumb user interface policy in the 430/530 products. You'd think they would have come up with a simpler, more efficient, and more intuitive way ...

The new G1000 also has an Along Track Offset (or ATK OFST) feature. The name may be counterintuitive, but enter the Flight Plan page, press the small FMS knob, use the big FMS knob to highlight the flight plan waypoint for which you wish to specify an altitude, then press the ATK OFST button. You can now specify a distance from a waypoint and a crossing altitude, which results in the creation of a new waypoint in the flight plan. The name of this feature may be dumb, but the feature itself is quite useful.

The Avidyne CMax chart display is pretty good in that in shows your position on the actual chart (circled in red), but accessing a chart requires a strange sequence of button pushes. And navigating back out of the chart display is equally convoluted.

The G1000's NACO chart display is similar to the electronic charts provided on the Cirrus' Avidyne, but these charts aren't a substitute for paper charts. The G1000 provides a soft key (circled in red on the lower right side of the MFD) that makes it very easy to display these charts from the map view and then quickly return to the map view, but there are several disadvantages. The NACO charts don't show your current position on the approach chart like the CMax displays do. When you display a NACO chart on the G1000, the moving map display goes away as does your terrain awareness and the TIS traffic display. Some of this information can still be displayed in the inset map on the PFD, but that inset map is pretty small.

One of the coolest features of the new G1000 is it's ability, when coupled to the KAP 140 autopilot, to automatically fly course reversal and holding pattern entries. For this to work, the holding pattern must be part of a defined procedure: The G1000 doesn't allow you to specify your own holding pattern like the older GNS480 does. Here is a sequence of photos of the G1000 and KAP 140 autopilot flying the SCK ILS RWY 29R by proceeding direct to the SC LOM, flying a teardrop entry, and finally getting established on the localizer.

If you are flying a GPS or RNAV approach, the G1000 and KAP 140 should automatically fly the course reversal and get you established on the intermediate approach course. You'll have to initiate the descent using the autopilot and I still have not discovered why the KAP 140 will not fly a GPS glide path.

If you're flying a localizer, ILS, or VOR approach, there's a catch. Anytime the nav source is changed when the KAP 140 is engaged in NAV mode, the autopilot will automatically switch from NAV mode to ROL mode (wings level). If you load, say, an ILS approach the G1000 will automatically switch the navigation source from GPS to the VOR/LOC receiver prior to the final approach fix causing the KAP 140 to go into ROL mode. The only indication that the autopilot is no longer tracking a NAV source is the NAV annunciator on the KAP 140 will flash to prompt you to reselect NAV (or approach) mode. The ROL annunciation will display, too, but the autopilot's display is not really in the pilot's primary field of view and there is no aural warning to get your attention. If you don't manually select NAV mode again on the KAP 140, the autopilot will not track the newly selected nav source and you could find yourself flying off course in short order. The new Garmin autopilot may handle the change of nav source without a problem, but did I mention that it is not available on the Cessna 172? I think I did ...

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