Originally Posted by
Brit312
Surges were not an uncommon or common event on Concorde, but when they happened - as they usually affected both engines on that side - the aircraft would lurch /yaw and everybody on board would know about it...
It was determined in a very early stage, that an engine surge or engine failure at supersonic speed would produce a very abrupt, inacceptable, and possibly dangerous, amount of yaw.
So the prototypes were equipped with "autorudder" computers. They used pressure sensors in the engines to detect engine failures, and they would then kick in a "pre-dosed" amount of rudder, that would then be "washed-out" gradually while the pilot dealt with the issue and added rudder trim.
They were manufactured by SFENA, and since I was their flight test support at Fairford, they became automatically my "babies".
The computers (analog, big boxes, the same size as the autopilots or air intake computers) were extremely reliable (we had only two passive faults during the entire flying career of 002).
Unfortunately the same could not be said of the pressure sensors, and since it was always easier to "pull" a computer than a pressure sensor, we found a computer on the bench every few weeks, which then had to be taken through a full test spec and sent back with "no fault found", before anybody was willing to look at the sensors.
Luckily a better solution was found, using a lateral accelerometer, and from the preprod aircraft onwards, each big separate autorudder computer was replaced by a single board tucked away in the autostab computer.
Since the function was always "on", there was no separate autorudder engage switch. Many years later, I discovered that several airline Concorde pilots did not even know the function existed....
CJ