Product Tip of the Month

Product Tip of the Month

April 2001

Model 540 Optical Tracker

Troubleshooting Bad Data

Required Ambient Light Conditions

The tracker will work well in nearly all daylight conditions. Blue sky is ideal, but cloudy and overcast skies are acceptable. Dark skies produced by heavy rain clouds may be too dark to produce an acceptable contrast. Twilight is generally not enough light for the tracker.

Always remember to point the aircraft away from buildings and hangars when collecting ground and hover track data. Dark colored backgrounds can impede proper operation.

The Optical Tracker works from the principle of recognizing the darker color of the blades against a lighter colored sky, as they pass across the two light sensitive diodes inside of the tracker. With this in mind, certain light conditions are more favorable when collecting track data.

The following conditions can cause false signals in the optical tracker:

High sun with a clear blue sky. This condition can cause sharp blade shadows across the canopy.

Dust, dirt or scratches on the windshield area where the tracker is being aimed. The shadows of the blades on the dust particles at certain orientations to the sun can produce false signals.

If either of these conditions exist, try flying the aircraft at a different heading, preferably 90 degrees to the sun. If the problem continues, a polarized filter can be used. The front of the tracker is threaded to accept a standard 40mm polarized filter commonly used for 35mm cameras.

LED Check and Proper Aiming

To properly aim the tracker, point the tracker lens parallel to the main rotor blades then rotate the tracker smoothly up towards the rotating rotor disc while observing the LEDs on the back of the tracker. Note that the three green LEDs illuminate. Continue to rotate the tracker further upwards until the top three red LED’s illuminate, this verifies that there is enough light for the tracker to operate properly.

If the top three red LEDs are verified, slowly rotate the tracker down until the three green LED’s are illuminated. Hold the tracker steady in this position and pull the trigger one time. Hold the tracker steady with the three green LEDs illuminated until the amber light extinguishes. You may then lower the tracker. The data acquisition is complete and will be displayed on the analyzer screen.

Tail Rotors and Propellers

While Tail Rotors and Propellers may require track verification, we do not recommend the Model 540 Optical Tracker for those applications. If you are in this situation, we advise the use of a strobe and reflective tape. Due to the color contrast theory with the tracker, it is unlikely that the tracker will operate or diagnose track splits correctly. It is also unlikely that you can operate the tracker per the instructions above because the orientation of tail rotors and propellers makes it nearly impossible to have a blue sky backdrop.

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