Even as the year-by-year changes and feature one-up-manship in electronic flight instruments seem to have gone from a shout to a murmur, there’s still some fire left in this fight.
Notably, Dynon has watched Garmin make big headlines with its Smart Glide (and Emergency Autoland), and had ideas of its own, hence the Emergency Glide functions rolled out in the latest 17.1 software. With this free upgrade, Dynon HDX users (as well as those with select Advanced Flight Systems EFISes) get a utility that can help spare precious brain cells in the event of a total loss of engine power.
Engine failure 101
In short, Dynon’s Emergency Glide system will take over for the pilot insofar as setting the airplane up for a preset best-glide indicated airspeed, which is really the first thing on your power-loss checklist, right? From there, Emergency Glide scans the area around the airplane to determine if there are airports within gliding distance.
It does an active calculation based on speed, sink rate, actual winds and terrain. There’s a 1000-foot buffer in the altitude calculation so that you don’t get too close to the rocks; more on this later.
To get this functionality, you need to be running at least a Dynon HDX system—it is not offered for the Classic or Touch models—or one of the later AFS systems. You need a two-axis Dynon or AFS autopilot. There are a few other requirements, including an up-to-date database and the airplane’s best-glide speed entered into the setup menu. Moreover, you have to have the autopilot’s “expert” mode enabled, but this is what most do and there’s no cost involved, just a setting. Finally, you have to have the nearest-airport filter properly configured for your airplane, unless you want to try landing on a helipad or at a seaplane base.
Easy upgrade
I’ve been flying for several months with a two-screen Dynon HDX and most of the company’s external modules—ARINC convertor, knob panel, autopilot control panels and ADS-B In receiver—as well as a two-axis Dynon autopilot. Updating the software took but a few minutes and it didn’t break a thing—early success! In fact, there’s no outward indication you have the extra features.
Until, that is, you press and hold the NRST key. Doing so brings up a notification on the primary flight display: HOLD TO ENABLE EMERGENCY GLIDE. Continue holding the button and the mode engages. The first thing it does is engage the autopilot in pitch and roll regardless of the previous autopilot mode. Then it syncs the indicated airspeed (IAS) bug with the preprogrammed best-glide speed and sets the AP to hold that value. Depending on how much power you still have available, the autopilot might well pitch up to capture IAS hold but in my experience it does so quite gradually. Once captured, the AP will hold this IAS value plus or minus about 3 knots. (This could be an artifact of how my system is configured and/or the airplane’s responses.)
So that’s pitch, and it’s the right way to go—quickly getting the airplane to its best-glide speed and holding it there while you troubleshoot. If that’s all the system did, it would be valuable as a way to manage energy and relieve the pilot of some workload.
Of course, this was the easy part of the programming. Much harder is calculating where the airplane might end up. Dynon’s approach is reasonably conservative. It needs to see an airport within the predicted glide circle that’s reachable given the existing winds and not blocked by terrain. This last feature depends on a 1000-foot buffer and worked well in my tests. Emergency Glide will not point you at a nearer airport if there’s terrain in the way; instead, it’ll aim you for an airport farther away but not blocked. That may mean it’s out of glide range for your aircraft. But I can see the logic: Better to put down somewhere short of that field than try to stretch the glide into rising terrain.
Two outcomes are possible once you engage Emergency Glide. Either the system sees a viable airport or it doesn’t. In the second case, you get a NO VALID AIRPORT annunciation and the autopilot defaults to a track lateral mode that syncs with the current heading when Emergency Glide is enabled.
But if it does detect an airport within gliding range, it sets the candidate as a direct-to waypoint, the autopilot to GPS NAV, calculates a vertical profile to the target—which might be at or well below the current flight path if the airport is quite near—and sets the altitude bug for field elevation. Moreover, if you have a Dynon or AFS comm radio, the feature will preprogram the needed frequencies. In my case, with the Dynon HDX talking to a Garmin GTR 200, it loads the target airport’s Unicom or tower frequency into the standby slot.
At the same time the airplane is pitching to maintain best-glide speed, the Emergency Glide feature begins turning it toward the target airport with an EMERGENCY GLIDE ACTIVE notation right above the flight director on the PFD. All of this takes but a few seconds, giving the pilot a chance to begin troubleshooting while the airplane is headed in a good general direction at a speed that prolongs the descent.
Let’s say you have not discovered a tank run dry or some other fixable reason the engine went quiet. The Emergency Glide feature keeps doing its thing. If you have altitude to spare, about a minute before reaching the airport, the system will annunciate NEARING AIRPORT TAKE CONTROL. It doesn’t kick the autopilot off at this point but is warning you that you’re close and it’s time for the pilot to begin setting up for the landing. But if you arrive with sufficient altitude and have crossed the midpoint of the airport, Emergency Glide will change to CIRCLING APT mode, which is simply that it sets up a 20-degree left turn. Dynon notes that because this is a roll-only mode it’s no longer taking wind into account so you could drift away from the airport. Presumably, though, you’ve got a bead on the best place to put down and can manage that on your own.
Of note is that should the airport originally designated become untenable—perhaps the winds have changed or atmospheric conditions have created more sink—Emergency Glide will return to track-only mode with IAS hold. It’s clearly annunciated on the PFD but it’s worth understanding that it could change modes on you. You can exit Emergency Glide at any time by changing autopilot modes or disconnecting the AP by the usual means.
Fly the plane
This system has worthy goals but what the Dynon system can’t do—and the company is explicit that it doesn’t—includes advanced functions like lining up for a particular runway or even committing the landing. The pilot remains on the hook for configuration control and the hopefully successful touchdown.
But there’s little doubt that Emergency Glide is a valuable tool to give the pilot some breathing room to troubleshoot in the air and have the controlled descent handled by the EFIS. The altitude saved or energy preserved by quick actions of the Emergency Glide feature could make the difference between getting back to a runway or putting it down somewhere a lot less hospitable.
