Originally Posted by
A Squared
So, once again, for Denti, yes it's surprising that AoA affects groundspeed and I'd be interested to have that explained.
Not Denti, but I've been scratching my head on this too. I cannot see how AOA could be used for groundspeed except
maybe possibly some kind of correction for gyro drift but then surely that's what the accelerometers are for.
Nevertheless, there is a tendency in engineering (I'd say particularly in software, but that may just be because that's what I've done most of) to "improve" by adding complexity and to use every piece of input data just because you can, which is great until some inputs are garbage, which then cascades to all outputs... Normally ADIRU is considered as two halves, more or less independent (think you can switch off the air data half on the 'buses and the inertial half stays on - and groundspeed comes from inertial), but there are connections between the two, and at the end of the day it's a box with a bunch of inputs including AOA and a bunch of outputs including groundspeed, so someone may have found a way to introduce a dependency.
I went looking for details out of interest, I didn't find anything but then one link lead to another and I stumbled across an FAA notice about loss of GPS signal leading to loss of yaw damper and stall warning system fail (among other issues). Just let that sink in for a minute, stall warning
dependent on having GPS signal!
Maybe it's just me, but that notice made me a believer - if someone can design and build
and get certified an aircraft where stall warning is
dependent on having a GPS signal, then I have no problem believing someone managed to get the groundspeed display to depend on AOA.