L-NAV

This page was last updated: 11/19/08

The Standard of Excellence in Final Glide Computers

L-NAV Demo Program Available

The L-NAV demo is again available. while it is not the latest version, it will give you an idea of how the instrument works. You will need to unzip the file in a temp folder and use your browser the view the demo. See the README.txt file for instructions. Click here to download the file.

The Latest Version 5.8

Note: The same features added to the L-NAV have also been added to the S-NAV.

Below are listed the new features found in V5.8

New Features:

	Achieved L/D over the ground (Slope) is now computed as GPS groundspeed divided by variometer reading. The value is reset upon switching from climb to cruise, and is averaged over the time available. After 30 seconds in cruise, averaging time is fixed at 30 seconds.
	The temperature/altitude page now appears on start-up if there is no outside air temperature probe installed. This reminds the pilot to set the temperature for the day.
	The Home 3 configuration shows component wind final glide altitude & instantaneous Headwind/Tailwind (HW/TW) on the Home screen. This page is now the same as L-NAV Versions 2 - 4. In Version 5.7, choosing Home 3 simply deleted the HW/TW page. Home 1 and Home 2 configurations show Altimeter reading on the instantaneous HW/TW page.
	Utilizing the KISS principle, the non-functional "Quick" wind option has been deleted.
	Thermalling statistics are now based on total energy. This improves accuracy.
	The default Averager configuration has been changed to "Smart". Pilots used to the old, fixed interval averager will notice that accurate results appear sooner upon entering thermals.
	Configuration options have been extended so variables shown at the upper left can be different in cruise and climb modes. See Section 4 for detailed description of choices.
	Variometer scale change (x 1, x 0.5, or x 2) is now done on the rightmost page of the main flying screens. It is now easier to change this value in flight.
	MacCready, bug polar and ballast setting are retained if power is cycled during flight.
	After a flight, MacCready ->0, Bug polar ->100% (Clean), and Ballast -> 0.
	Climb statistics as well as logbook flight time are retained until the next takeoff.
	We fixed a computational error that made the Averager read 2% high.
	The display of instantaneous wind component (HW/TW) is now easier to interpret. It is rounded to the nearest knot, and the trend (+ or -) is shown following the value.

You may download the user's guide at no charge. Please see the Manuals page.

Upgrade Pricing:

If your L-NAV is presently at a version earlier than V5.3 (S-NAV V7.3 / 8.3), the upgrade is $250.00 (U.S.). If your L-NAV is presently at V5.6 or V5.7 (S-NAV V7.5 / 8.5) there is a nominal charge for the ROM. You have the option of doing the upgrade yourself or sending your instrument to the factory. In either case the cost is $75.00 (U.S.).

For further information on upgrading, please see the Upgrade page.

One important feature that is available now is the capability of outside air temperature measurement using an air temperature probe. In version 5.6, it was possible for the pilot to manually enter the outside air temperature into the L-NAV. Outside air temperature is used for the calculation of airspeed. With the addition of the outside air temperature probe, the L-NAV can now measure the actual air temperature to perform important calculations more accurately.

The temperature probe upgrade must be done here at the factory or at a Cambridge Aero Service Dealer. The cost for the hardware upgrade is $236.00 (U.S.). Firmware version 5.7 or later is required and is an additional charge to the hardware upgrade.

L-NAV Version 5.7

Note: The same features added to the L-NAV have also been added to the S-NAV.

Below are listed the new features of this release.

	Configurable HOME Screen.
	Configurable, "Smart" Averager.
	Choice of averaging interval for Slope and Netto calculation.
	Revised speed-to-fly tone patterns when [Sink Tone] is used.
	Improved logic for Spoilers and Landing gear alarms.
	Altimeter screens in both Feet and Meters when metric units are selected.
	Glide altitude graphic display now shows when you are very high or low.
	Measurement of Outside Air Temperature using optional PC board.
	Support for Cambridge Pocket-NAV Graphic display system.
	The ASI zero calibrate screen shows airspeed in selected units (Knots or KPH).

L-NAV Version 5.6

Note: The same features added to the L-NAV have also been added to the S-NAV.

New Features

	Final Glide Around a Turnpoint - Total altitude required for a final glide around a turnpoint to the finish point (when coupled to GPS-NAV)
	Wind Direction and strength - Vector Wind is derived from GPS groundspeed, GPS track, and True Airspeed at different glider headings.
	Speed-to-fly takes wind into account - In a headwind the minimum altitude required to reach a goal will be at a MacCready setting greater than zero.
	Airspeed Calibration - High-resolution wind measurement shows airmass behavior. Measurement accuracy is enhanced by in-flight True Airspeed (TAS) calibration referenced to GPS-based groundspeed.
	Total Energy Final Glide- Required glide altitude takes into account the total energy of the glider (speed can be traded for altitude).
	Thermalling Statistics - Average achieved climb rate in a thermal, total height gained in a thermal, average achieved climb rate in all thermals, percentage of time spent circling, total altitude gained since take-off (or the last reset).
	Temperature at Altitude Entry Screen - Provides for very accurate altitude and True Airspeed data.
	TE Probe Adjustment Screen - Allows for tweaking the amount of total energy compensation (80% - 120%, default = 100%)
	G-Meter Monitor Screen - Shows current G's, minimum G's, maximum G's, and average G's (over 16 seconds). (Optional G-Meter must be installed)
	Display Configurability - Decide which parameter to display in the upper left position on the main screens. Select from Netto (30 second average of the net airmass motion), Slope (30 second average of the achieved glide slope), Track Error (GPS Track - GPS Bearing), or MacCready.
	Goal height is preserved- When Barometric pressure, Temperature units, Polar numbers, or Long/Short wing are configured, behavior is the same as turning power off & on. Changing Units of Measure (NMI, KM, etc.) returns to factory default values for everything but units of measure.

The L-NAV's Custom display puts all the important information on its Main Screen. Clearly labeled secondary screens simplify data entry. Advances pioneered by the Cambridge S-NAV have been incorporated. These include:

	Digital Altimeter
	Graphic Glide Slope Display
	GPS Compatibility
	Automatic climb/cruise switching based on our "G" meter
	Two Stage Climb Audio based on MacCready Setting
	Climb optimization based on G-Meter and Airspeed
	Elapsed time clock
	Full Function Repeater for 2-seat sailplanes

Cambridge advanced technology makes the L-NAV the most cost effective NAV computer on the world market today. We have manufactured and sold more than 1000 L-NAVs since 1991, and every one of those instruments can be upgraded to this latest version. In fact, this upgrade can be done by the pilot with nothing more than a screwdriver and the upgrade ROM!

GPS Compatibility

The latest versions of the L-NAV work with any GPS which transmits GPRMB and GPRMC sentences of the NMEA 0183 Standard. Of course it is compatible with the Cambridge GPS-NAV.

With no GPS connected, it functions exactly like older versions of the L-NAV. This means that a pilot can buy the L-NAV now and add a GPS later. The L-NAV is the most cost effective way to move into the GPS world.

Why connect a GPS receiver to the L-NAV? First, waypoint names and coordinates are entered by the pilot into the GPS receiver. During the flight the GPS unit sends data to the L-NAV including:

	Distance to the waypoint
	Bearing to the waypoint
	Track of the glider over the ground
	Ground speed of the glider

The L-NAV subtracts the Track from the Bearing. This difference is the Track Error and it is displayed on the L-NAV. When Track Error is zero, the glider is headed directly to the waypoint. Cross winds no longer make navigation difficult!

The L-NAV measures Airspeed and Altitude, and computes True Airspeed. The difference between True Airspeed and Ground Speed (from the GPS) is the wind component in the direction of flight. Wind measured at small Track Error is entered by the pilot into the final glide calculator. The result is a new level of precision in final glides.

Glide Computer with Graphic Glide Display

	Accurate wind estimate using simple waypoint correction (or by connecting a GPS).
	Rapid update shows effect of MacCready and Wind changes. Climb/Cruise decisions on final glide can be made at a glance.
	Simplified Final Glides using Graphic Glide Slope Indicator. Set MacCready to center the indicator; then fly the audio or Graphic speed-to-fly command.
	Digital Altimeter Display with 5 Ft (2 meter) resolution. Useful when you are scratching around in marginal lift.
	Full Function display and control available for 2-seat sailplanes.

Well Damped Audio Variometer with Reliable Probe type Total Energy Compensation:

	Compensation is independent of sailplane static location and behavior.
	Separate, distinct, lift, speed-up, slow-down, and Slow Alarm tones.
	Different tone pattern for lift above and below MacCready setting.
	Configurable steady Sink Tone in Circling Mode
	Configurable audio quiet bands in Cruise Mode.
	Slow Alarm tone (with optional G-Meter). Modern airfoils need good airspeed control for optimum climb performance. The alarm tone is based not only on airspeed, but also on ballast, bank angle, and wing loading due to airmass acceleration.
	Audio over-range to 13 knots on x1 scale. There is no need to change scale for the occasional "super" thermal on an ordinary day.
	The audio tone is clear and distinct, but not harsh. This means better thermal centering with less fatigue.

Automatic Cruise/Climb switching based on G-Meter (Option)

	Most computers try to detect circling flight by looking at airspeed. This doesn't work for Dolphin style flight or circling in rough air. Instead, we combine airspeed and acceleration inputs to detect circling. Our more expensive approach works!
	On standard class ships, automatic switching means reduced mental stress for the pilot. It also means reduced navigational errors.
	On flapped sailplanes, there is no need for tedious or expensive flap switch installation. Also, Dolphin style flight with climb flap settings causes no error in distance measurement.

Specifications:

Size:

3.3" (84 mm height and width, 7.7" (196 mm) depth behind panel;
Fits Standard 3 1/8" (80 mm) instrument panel cutout.
Choice of 3 1/8" (80 mm) or 2 1/4" (58 mm) diameter vario readout.

Weight:

Computer unit: 1.5 lbs. (0.7 Kg), Vario readout: 0.6 lb (0.27 Kg)

Power:

8 to 16 volts at 0.14 to 0.18 Amps depending on audio level

Processor:

80C552 with 64 Kbyte ROM, 32 Kbyte RAM, and 1 Kbyte EPROM

Backup Battery:

Lithium Coin Cell, type BR2325

Datacom:

Industry Standard RS-232 voltages and protocols

Airspeed:

Thermistor flow sensor; Range 0 to 170 kts (0 to 300 km/hr)

Variometer:

Thermistor flow sensor with standard external 0.45 liter flask

Altitude:

Piezoresistive Sensor; Range +26,000 Ft (8,000 meters)

Acceleration:

Solid State based on MEMS Technology; Range ±5g, Resolution 0.01g