Xavion App Guides Engine-out Airplanes To Nearest Runway

 - March 4, 2013, 2:35 AM

If your engine or engines suddenly quit, could you glide safely to the end of a runway? If that does happen, an iPad/iPhone app called Xavion can help point the way to a safe landing in any weather.

Xavion is the latest product from X-Plane simulator developer Austin Meyer’s Laminar Research. The company tested Xavion extensively on X-Plane and used the simulations to hone the program’s algorithms. A side benefit is that you can run Xavion on X-Plane to practice before trying it in a real airplane.

Taking the time to set up Xavion properly helps the system deliver better results. You can set up multiple aircraft, each with weight-and-balance, glide speed and ratio and other parameters. Xavion includes a tracker for pilot and annual inspection currency as well as a weight-and-balance calculator with graphical envelope. The iPad or iPhone must be affixed vertically in the airplane and not on a moving yoke.

Xavion’s sensor inputs include GPS and the iPad/iPhone’s gyros and accelerometers. While Xavion will work with the internal Apple GPS in 3G/4G devices, an external GPS provides better results. Xavion also works with external AHRS units made by Levil Technology.

The Xavion presentation shows a moving map on the bottom and on top a synthetic vision view overlaid with “airspeed” indicator, vertical speed, GPS-derived altitude, slip indicator, artificial horizon and magnetic track. The airspeed is not real airspeed because Xavion has no access to air data. Laminar Research uses standard atmosphere lookups to correct the GPS groundspeed for local air density.

During flight, Xavion constantly performs calculations to determine the path to a safe runway end in case the engine quits. The moving map shows the location of the airplane, and the area that is within gliding range is brightly colored. Black areas are unreachable. Airports are color-coded: green airports are safely reachable in a glide; yellow airports might have problems such as short or narrow runways or near the edge of maximum gliding distance; and red airports are unreachable.

Hands On

After trying Xavion on X-Plane, I tested the app in a Piper Warrior along with a safety pilot. The first test was at 5,500 feet msl north of Rialto Airport in southern California. The airport was within the bright area on Xavion’s moving map. After chopping the power, I pushed the red emergency button on Xavion and it immediately drew a magenta path to the end of Runway 24 at Rialto. On the upper PFD section, Xavion displayed magenta hoops to follow. Xavion recommended a glide speed of 86 knots, which is faster than the Warrior’s 76-knot best glide speed. The reason for this is that Xavion targets a nominal glide speed, halfway between best glide and max flap extension speed with flaps down. Nominal glide speed leaves room for error, stronger winds, thermals and so on.

On the right side of the moving map, Xavion displays an energy meter, to show the pilot the energy state. Too much energy close to the runway might require adding drag (flaps, speed brakes, landing gear). Low energy might mean that drag was added too early and needs to be removed. But flying at the nominal glide speed should help pilots avoid entering the low-energy area.

The second test started at more than 4,000 feet, again north of Rialto. In both tests, we arrived near the end of Runway 24 with plenty of excess energy and easily made the landing without adding power. I did the testing with an iPhone 5, although it’s obvious that the larger screen of an iPad (2 or later) or iPad Mini would work better. I found the energy gauge to be a little flaky, but this may be due to using the internal GPS. On my iPhone 5, the airports didn’t seem to be properly color-coded. Xavion sells for $99.99, and its maker says the most recent version operates at up to 40,000 feet and for aircraft weighing up to 99,999 pounds.