Originally Posted by
FCeng84
Gums - 737 Max conversion from AOA vane to AOA body is an approximation that uses a scale factor of slightly more than 0.5 plus a small second order term and a constant offset. This is clearly a simplified fit to a non-linear relationship that was designed to be sufficiently accurate over the range of interest. A vane movement of 2 degrees equates to a free stream AOA change of about 1 degree. The sensor base plate has eight holes and a pair of alignment pins that look from pictures I have seen to be located roughly fore / aft along the horizontal line of symmetry of the circular base plate. I do not know the details about whether or not installation is critical with regard to which pin is forward and which pin is aft. I suspect that the same sensor is designed to work on either side of the plane so there must be something in the wiring or signal processing down stream that differentiates between left and right and sorts out whether clockwise motion is positive or negative AOA change.
I'm confused by this. When installing an AOA a reference check is done against the aoa angle and smyd. The quick check uses three points. The upper aoa stop is 100deg, middle is 0 deg and lower stop is -100 deg. These correspond to actual angles as measured at the aoa and as seen on the smyd display. I'm confused as to why a conversion would be needed.
The aoa cannot be installed backwards as it only has 200 degrees of movement. Symd 1 and 2 contain different functionality so I would think the processing of aoa angles is done there with regards to the aoa being in the left or right position.