Flying with Xavion in Your Airplane
Once you have set up Xavion, you have done the hard part.
Now let’s fly!
If you want to walk through this manual while actually USING Xavion, you can do it either in your airplane, or (at considerably less cost and risk) in the flight simulator X-Plane!
If running through this manual while using Xavion in a real airplane, then do the following:
If you just have an iPad, then before flight, be sure to MOUNT the iPad in the airplane in a vertical attitude so it is securely fixed to the aircraft in some way. Only then will the motion of the IPAD be the same as the motion of the AIRPLANE, and the indications that result be accurate. MyGoFlight makes excellent mounts. With an iPhone, you may be able to hand-hold it in an emergency, though this is obviously second-best.
To really get the ultimate in power and safety, though, you need a Sagetech Clarity or iLevil ADS-B receiver. These are nice little boxes that give attitude, GPS, ADS-B weather, and traffic to Xavion. Get one of those and simply log Xavion onto the WIFI that it broadcasts. Nothing could be simpler, and the power that results is amazing.
OK, now you are in your airplane or running X-Plane, so let’s start using Xavion!
Hit the PRE-FLIGHT menu button.
Be sure that your airport database is current… let’s not fly to an airport that has been closed!
Grab Low Enroutes, Sectionals, SIDs, STARs, and Approach Plates here. With these, you should not need to run any other EFB App, but instead use Xavion for the entire flight, since your normal-use maps and plates will all be available. BUT, the moment you need a backup PFD and MAP, or even power-off guidance if the engine fails, Xavion will be running, ready to give that guidance!
Hit the FLIGHT CURRENCY menu button.
Here, enter your birthday and the dates of all your various other currency-checks by simply tapping on the silver keys.
Text at the top of the iPad will let you know if you or your airplane are out of currency.
Hit the WEIGHT BALANCE menu button.
If you entered the CG envelope corners and max-loads properly in the setup, then you will see the weight and balance envelope for your airplane. Now simply SWIPE your finger across the load-out buttons to enter weights at each station and your fuel on board. If you did your setup properly, then you will see a line through your CG envelope that shows your weight and balance at current fuel down to zero fuel, so you will see at a glance what your weight and balance will be for the entire flight.
If you do these three things before each flight, then you will know your currency, fuel burn enroute, time-burn enroute, and weight and balance before each flight. This is not bad for ordering fuel, telling your folks on the far end of the trip when you will arrive, and passing a ramp-check with flying colors.
Quickly enter the barometric pressure (for the altimeter to indicate properly if you have some sort of pressure-sensor, such as the the one on an iPhone6, the newer iPadAirs, or an ADS-B receiver! Also enter the winds and temperature. Xavion will obviously need this info to guide you properly. If you have a net connection at the time, by either WIFI or CELLPHONE, then Xavion will grab what weather it can, and it will update that weather by ADS-B as well. See how that weather-collection is going in this screen. Just be sure to always enter the weather manually at the top of the screen, in case Xavion cannot get it wirelessly itself!
Now, back to the main screen and: NAV:
Hit the NAV menu.
This system will guide you anywhere though 3-D Highway In The Sky hoops, and also estimates the time and fuel burn to get somewhere, which is useful for obvious reasons. As well, you can add or delete a few waypoints for your prelim planning, in what seems to me to be the easiest FMS interface that I have ever seen, and in fact the only interface that makes any sense to me at all.
To use this function, hit the D-> button and enter the destination of your choice.
If you have entered your fuel flow and climb rates and cruise speed properly in the setup, then you will see the time and fuel burns for a variety of altitudes to your destination in the ALT menu.
Note the SCORE to the right of each altitude. That score indicates how good each altitude is for conserving time and fuel. If an altitude has a score of 98%, for example, then you know that it is ALMOST as efficient to fly at THAT altitude as the optimum altitude. You can therefore select that altitude (for reasons of pressurization, oxygen, ATC, convenience, etc) and know that you are very close to maximum efficiency. If an altitude has a very low score, however, then you would probably be well advised to avoid because of the extra time and/or fuel burn that will result.
Now, back to the main screen and: AIRPORT PLATES:
If you got the optional Seattle Avionics charts and plates, then you can look up airport diagrams, SIDs, STARs, and approach plates here.
Now, back to the main screen and: GLIDE/PATH/PROFILE MAP:
Hit this button to cycle through the various map zoom modes, zooming to the gliding-range, flight path, or profile view, which is shockingly similar to the glide-path cone that the Space Shuttle pilots would use to bring the Orbiter home without power.
Go here to set the various preferences and observe diagnostics as well.
This is the “red button”.
Xavion is CONSTANTLY running simulations of power-off glides from your current position (and altitude and heading and speed) down to EVERY runway that it thinks is within gliding range, and showing you what it thinks is the best option for a power-off landing as a series of white hoops. This is PLANNING the power-off approach about ONE SECOND (!) in advance! Then, when you hit the “FLY HOOPS” button, Xavion locks down the currently-best idea it has for a power-off approach, and the hoops turn magenta and will no longer move or update. At that point, your approach to the runway has been planned and locked down: You need only fly it.
OK you have explored the menus so now let’s look at the PFD and map.
The airspeed is on the left, of course, and it is GPS derived. So, really, this is GROUND speed, but with a twist: Xavion estimates the air density at your location using a standard atmosphere based on your (GPS-derived) altitude, and lowers the indicated airspeed according to what a real airspeed indicator would indicate in that thinner air. So, this is not exactly ground-speed, but is instead “GPS-derived indicated airspeed”, or, if you prefer, “ground-speed corrected for estimated air density”, or, if you prefer, “indicated ground-speed”. Whatever you might call it, it is the closest to indicated airspeed that we could get without tapping into the pitot-static system of your airplane, but instead go off of the iPad’s internal sensors or externally-mounted GPS alone.
GPS-derived altitude is clearly on the right. This will always indicate differently than your pressure-based altimeter, since the pressure LAPSE-RATE of the Earth’s atmosphere is always in flux, so the pressure-based altimeters are constantly in error. (Since they are all in error by the same amount, though, at any given time and location, airplanes do not crash into each other due to errors in indicated altitude).
Vertical speed to the left of the altimeter is clear, and is simply based on the rate of change of GPS-derived altitude, and will indicate quite close to your pressure-based vertical speed indicator.
The magnetic track is at the bottom of the PFD, and is also quite accurate if you are moving at a good clip with a functioning GPS. If you are motionless with a functioning GPS to TELL Xavion that you are motionless, then that indicator will revert to the magnetic compass heading since there is no defined track if you are not moving. Be aware that the iPad and Levil compass can easily be off by 90 degrees (!) in the cockpit, perhaps due to the magnetic fields created by the various electrical systems therein.
Up top you should see the slip indicator, which indicates quite accurately the slip of the airplane. The ball in in a physical turn-coordinator simply reacts to sideways accelerations of the airplane, and the accelerometers of the iPad do this nearly perfectly, so the slip indicator will function very accurately if the iPad is mounted in a level vertical attitude in the aircraft.
Then, wandering somewhere about the middle of the screen, you will see a little circle with some lines that look like wings and a tail sticking out of it. That is the VELOCITY VECTOR. That is the thing that indicates where you are GOING. This is a little bit different than that horizon, which indicates where you are POINTING. Now, since the magnetometer in the iPad is VERY unreliable because of its unfortunate location in the middle of an electronic device in the middle of a cockpit filled with other electronic devices, all of which create magnetic fields, we do NOT really know your heading in flight. Because of this, we use the TRACK, NOT THE HEADING, for all heading displays (both synthetic vision and the compass rose). The only time we use the (highly in-accurate) magnetic compass in the iPad is when we are NOT moving at all! As soon as we start moving, we can derive a GPS-based track which is much more accurate than the heading so we use that. For this reason, the velocity vector should always be very close to the center of the display laterally, since both it, and the synthetic vision imagery, indicate what direction we are GOING, not what what direction we are POINTING. (The velocity vector may indicate off to the side a bit during maneuvering, since the synthetic vision imagery also takes cues from the gyros in the iPad or iPhone).
And, behind all that, of course, you see the artificial horizon with synthetic vision, which is awfully handy to stay right side up and avoid the ground if all of the other instruments in your airplane fail in flight.
Below that, we see the map. In flight, you will notice that the map is largely empty black space, with an area of the map shaded in color… perhaps dimmer color near the edges. The area that you see in color is the gliding range of your aircraft, assuming no wind, if you entered the gliding performance of the aircraft properly in the setup process. The area colored brightly is the area you can glide to with the propeller in the cruise position. The more dimly-colored area outside of that, if present, is the area that you can reach with the prop feathered, assuming a variable-pitch prop and no wind.
So now, if the engine fails, or you are considering the possibility of an engine failure, you can tell AT A GLANCE what airports are within gliding range! Simply look for the airports that fall within the colored area of the map! As well, look at the COLORS of the airports themselves. GREEN airports are ones that Xavion believes you can glide down to and land at safely (based on its internal flight simulations of power-off landings that is is CONSTANTLY running as you fly), yellow airports are ones where the outcome is not at all so optimistic (due to short or narrow runways, or the runways being at the ragged edge of gliding distance), and red airports are ones that Xavion thinks you are simply not so likely to be able to reach power-off.
And, finally, if you are in flight within gliding range of a runway (with a bit of extra altitude to maneuver onto a stable final approach) then you will see a PATH leading from your craft to that runway. This will be displayed on the map as a path that you can follow, and as HOOPS on the PFD that you can fly through. If you have entered the glide ratios of your airplane properly in the setup menus, then these hoops will come down at a glide ratio that is halfway between your best and worst glide. (Best glide is flaps up, best glide speed. Worst glide is flaps full down, at max full flap extension speed).
Xavion is designed to bring you down at neither best glide, nor worst glide, but instead at a glide ration exactly halfway between those two glide ratios. We shall henceforth refer to this as NOMINAL GLIDE.
Remember, when the Space Shuttle would effectively have an engine failure over Japan, the pilots flying it did NOT try to go to BEST glide speed and aim for the NEAREST airport. That would have implied a 250-knot indicated glide to Tokyo! Instead, they took a PRE-PLANNED NOMINAL GLIDE THAT WAS NEITHER THE BEST NOR THE WORST GLIDE THAT THE SPACE SHUTTLE COULD DELIVER, BUT WAS INSTEAD ABOUT HALFWAY IN BETWEEN THEM. That way, if things did not go as planned, the Orbiter could move to BEST glide if things went worse than planned, or pop the speedbrakes and S-turn and move to WORST glide if the ship wound up HIGH on energy. More conventional gliders operate the same way if they are being properly flown. They do NOT aim for the landing target at BEST glide condition… this would leave no room for error and result in coming up short half the time. Instead, a properly-planned approach is flown at halfway between the best and worst glide that the glider can manage, so if thermals or wind are different then predicted, the pilot may simply use more or less speedbrakes or flaps to maintain that PLANNED approach. Xavion understands this, and works in just the same way: It PLANS an approach that is RIGHT BETWEEN best and worst glide, so if you have more or less energy than planned, you can simply raise or lower the flaps (or feather or firewall the prop, or pop or retract the gear or speedbrakes, or S-turn or not) to keep the airplane in the hoops for the entire descent to the runway.
So, as you follow the hoops down after hitting “the red button”, you have 3 possibilities for managing the descent:
- Everything goes just as planned: Leave the prop, gear, and speedbrakes in cruise configuration and put the flaps down about halfway. Follow the hoops.
- You wind up LOW on energy due to headwinds or downdrafts: Go for BEST glide speed, flaps up… the better-than-nominal glide may let you re-acquire the hoops to follow down.
- You wind up HIGH on energy due to tailwinds or updrafts: Go more for WORST glide speed, flaps FULL DOWN.. the worse-than-nominal glide may let you re-acquire the hoops to follow down.
So this is how you manage your energy as you follow the hoops down to the runway threshold: EXPECT to run power-off at about half flaps (just like the Space Shuttle coming in with its speedbrake deployed, or a conventional glider coming in with its speedbrakes 50% extended), but be ready to clean up the airplane if a headwind or downdrafts begin to push you below the hoops. Conversely, be ready to extend the flaps all the way, lower the gear, extend the speedbrakes, or S-turn to bleed off energy if tailwinds or updrafts have you ABOVE the hoops.
Looking at the hoops to see if you are above or below them will instantly show you whether you are high or low. If low, consider cleaning up the airplane and going for best glide. If high, then consider s-turning, running your turns a bit wide, or maybe adding drag to the airplane with prop, flaps, speedbrakes, or landing gear. Practice this at least a few times in X-Plane or in the real airplane so you are prepared to follow the hoops if you ever need to, if you want to do the training now to let you fly more safely later!