ATR: TAS and Attitude Gyro connection
Here's a question that really bothers me: What's the use of TAS with regards to AHRS, particularly with Attitude Gyro erection. It seems that on the ATR, ATT GYRO automatic erection is subject to the availability of TAS as an input parameter for the AHRS. And if TAS happens not to be suddenly available, Attitude Gyro auto erection would fail, manual erection would have to replace it.
So what's the connection between the two?