I am changing acronyms starting with this post. Previously I was calling this an SAS for “Stability Augmentation System” but someone pointed out that this is technically more of a CAS for “Command Augmentation System”.
SAS implies a direct connection between pilot input and control surface deflection with some additional stability augmentation mixed in. CAS implies that a flight computer is translating pilot inputs into a “request” and the flight computer then tries to satisfy that request, but there is no immediate direct mapping between stick deflection and control surface deflection.
1. We added some additional logic to slowly roll the wings to perfect level if the pilot puts the bank angle within +/- 10 degrees of level. It’s really hard to get it exact from a ground perspective, so the idea is to let the pilot get in the ball park and the system will take over and finish the job. Auto-leveling will only kick in after the pilot centers the stick so it doesn’t fight the pilot if the pilot is intending to bank the aircraft.
ATI has been developing a number of flight control system building blocks and we have been testing them on my Senior Telemeaster airframe. This week I decided to connect them up to create a simple SAS (stability augmentation system.)
Briefly, when flying with an SAS, the pilot is still 100% in manual control over the airplane, however we have inserted a flight computer in between the pilot control inputs and the control surface actuators. Rather than the pilot’s stick commands directly moving the control surfaces, the pilot stick commands are translated to roll and … Read the rest... >>
One of the most challenging aspects of autopilot setup is tuning the gains for a particular airframe. When the gains are tuned poorly, the aircraft my oscillate excessively, it may lag way behind the target pitch angle or roll angle or velocity, it may never reach the target values. Poorly tuned gains could destroy an airframe in a worst case scenario, but often people just live with non-optimal gains that aren’t great but work well enough to get the aircraft around the sky. It’s hard to know what gains to tune and why and a person could … Read the rest... >>