Its all software - on modern airplanes many computers "know" what mode the aircraft - IE how does the flight lock computer "know" - how does the pressurization computer "know" - IE they infer it from a combination of variables such as squat switchs, prox switches ( PSEU stuff ) - altitude, throttle lever position, wheel speed etc.. Working out the failure effects is even more problematic - I saw a 757 RAT deploy at Atlanta while 50 aircrafts were qued up waiting for microburst storm cells to clear - many aircrafts had one or both engines shut down - the advancing jets ahead of the 757 with engines shut down apparently generated pitot pressure giving the summation of enviromental effects that indicated to the RAT control logic to deloy - IE airspeed, both engines shut down, the air-gnd logic was on the power bus affected by the shutdown engine - same has been the experiance for flight lock computers =- particularly since they are dispatch critical - you cannot have any screwy logic issues with flight locks ..But to answer your question - there is some logic that infers taxi .. Dunlop, ABSC and Boeing have patents on the taxi-brake inhibit - you can look them up & read about the issues on
www.delphion.com -