Horizon Sensing Autopilot Query

[faraz99]

guys i m studying horizon sensing ap.and i am getting confused on a question that when one sensor for example right aeliron comes in front of the sun light and the other will on the opposite side of the sun.then what will its behaviour.what will he do in this case.

[vespa]

The infrared thermopiles used in these systems are sensitive only to a very specific range of IR wavelengths corresponding to the range typically emitted by objects of "earthly" temperatures. IR radiation from the sun is largely filtered out and has little to no effect. A little more info is here:
http://www.recherche.enac.fr/paparazzi/wiki/index.php/Theory_of_Operation#Infrared_Sensors

[faraz101]

thanx for the link.
and what effect on the water?

[BarrelRoll]

According to this
http://www.recherche.enac.fr/paparazzi/wiki/index.php/Theory_of_Operation#Infrared_Sensors

"The sensors typically have a 100 degree field of view and produce a somewhat sinusoidal voltage response relative to their angle orientation. as seen in the plot to the right. By combining the data from 3 orthogonal pairs of sensors (X, Y, Z axes) we can compute the exact bank and pitch angles of the aircraft in any weather/terrain conditions..."

What about the case of mountains to the south and plains to the north situation. Would the autopilot think that the real horizon is tilted in the south-north direction?

[vespa]

What about the case of mountains to the south and plains to the north situation. Would the autopilot think that the real horizon is tilted in the south-north direction?

Yes, of course. The effect is virtually identical to that of wind and produces a very small navigation error. It is of little concern.