Your connection with the sky

Sailplane instrument panels

When airplane pilots first encounter a glider instrument panel it can be a jaw dropping experience. Not because of its complexity but its simplicity. Training gliders may have nothing more than an altimeter, ASI, variometer and compass. Instructors will point out that the view outside and a bit of red yarn taped to the canopy are your most important instruments.The bit of yarn is a "Yaw String" that takes the place of a ball slip/skid indicator. It tells a pilot the controls are "coordinated" and the fuselage is perfectly aligned with the airflow, therefore producing absolutely minimum drag - critically important for maximizing performance.

Of course, the panel can get more complicated than that. Owners of high performance gliders will equip them with a bewildering array of gadgets limited only by panel space, battery capacity and the owner's wallet. 760 channel radios and GPS are standard with transponders, though not required, becoming common. "Glass Cockpits" with moving map displays are becoming available.

The most important electronic instrument is the "Total Energy (TE) Vario" with a "Speed to Fly" (STF) display. (Think Vertical Speed Indicator [VSI] on steroids.) This instrument displays data the pilot needs to extract maximum energy from the atmosphere and use it efficiently in both cruise and climb mode. In effect, it shows the rate at which the gliders' energy state is changing with time.

A VSI merely displays vertical speed averaged over a minute - not fast enough or informative enough for finding and using thermals. Sailplanes are extremely efficient aerodynamically, so airspeed can be exchanged for height and height for speed with tiny pressures on the stick. An unsteady hand on the stick can make simple vertical speed readings unusable. The TE vario sums the potential energy of height and the kinetic energy of speed and shows the rate at which that sum is changing - i.e. whether the glider is gaining or losing energy displayed as vertical speed in Knots. This provides a very fast response yet relatively high "signal to noise ratio" when trying to find the core of a bumpy thermal.

The STF function of the TE vario displays a "Fly Faster" or "Fly Slower" command - slower in rising air and faster in sinking air to minimize height loss and maximize average speed in a straight glide. Just how much faster or slower depends on four things; the glider's polar curve, the expected strength of the next thermal, the ballast on board and the bugs contaminating the wing leading edge. TE/STF data is so important that the information is also presented as a complex audio tone so a pilot can be looking outside and still manage the gliders' energy state - critical when sharing a thermal with other gliders.

PDA's running special software with GPS input provide moving map displays. These maps show the usual stuff like special use airspace and airports. Some have a feature called glide footprint or an "Amoeba" named for the way it looks. The "Amoeba" is an outline drawn on the moving map showing the maximum distance a glider can go in all directions with consideration for wind and terrain elevations. Airports within the "Amoeba" are reachable, those outside are not. It follows the glider as it moves changing shape as conditions change. This display answers the questions, "Where am I and where can I go from here?"

Since the computer receives GPS data and thermal strength information it can keep track of the strongest parts of a thermal and suggest maneuvering solutions for centering the strongest lift. At greater range, an even more impressive trick is a database compiled from years of glider flights with coordinates of ground features which have generated thermals on previous flights. The software uses the current wind, sun angle and glider altitude to predict where the glide path is likely to intersect a thermal column.

The trend is to combine these data in a large LCD "Glass cockpit". Until very recently, LCD screens bright enough to be useful in direct sunlight consumed too much power for a glider's small battery. I think we are on the cusp of a radical change in panel technology similar to that seen in airplanes.

Everybody likes MS Flight Simulator. Next time, special sailplane simulators that let you race pilots all over the world via the Internet.

4 Responses to “Sailplane instrument panels”

  1. Jack McCombs Says:
    May 4th, 2009 at 7:11 pm

    I'm a life member of SSA and have over 1,200 hours of glider time (albeit in the distant past), and I read Soaring Magazine faithfully every month. Yet, I never heard of some of the features available to soaring pilots via specialized avionics today. This is a much better "quick and dirty" description of available soaring avionics, than anything I've ever read in Soaring Magazine. Thanks!

  2. For more details and images of a "typical" cockpit (if there is one) see http://en.wikipedia.org/wiki/File:Glider_Cockpit.JPG.

    Enjoy, John DeRosa

  3. There are a few more avionics in a glider now than when I first went up. The gps is the one I think that I would of made most use of.

  4. Glider flying has always appealed to me. I have never really worked out how pilots find thermals. none the less it is amazing. There is some great stuff on glider flying on YouTube " day in the life of a pilot"

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