Originally posted by RR_NDB ...
So the question? Why they used redundancy? The reason i call it "ridiculous" is because the use of n identical and non adequate AS sensors failing simultaneously is absolutely useless.
The pertinent points that need consideration are:-
- In the reported UAS instances they all involved a common mode problem associated with short term malfunction and/or disagreement between the airspeeds provided by three pitots.
- The UAS lasted for periods measured in seconds and not multiple minutes.
- All aircraft were in Normal Law in stable cruise.
Bearing the above in mind, the aircraft successfully measured numerous other parameters and applied them to allow the autopilot and autothrust to progress the flight according to parameters entered into the FMS. All these parameters are reflected in the aircraft's
Total Energy component, and it is not beyond any software programer to deduce the KTAS/KCAS from the TE.
So why not provide a
Normal 2 Law that implements itself in a non latching manner when UAS becomes an issue. This Law would provide a continually updated
pseudo KCAS based on all the other environmental data available, including inertial data, and allow the aircraft to maintain stable flight.
Notify the crew and allow them to monitor the situation and ensure that a return to Normal Law occurred when pitot derived airspeeds had stabilized. The object is to remove the "
startle factor" and ensure a smooth transition in flight laws to cover what is normally a short period of unreliable airspeed.