@PA 18 151:
If ALT 2 had latched, which appears to be the case, would that prevent a further change to Abnormal Attitude Law?
Clearly NO!
As is advertised: This law ensures that the flight control law will never hinder aicraft recovery, after the recovery (within the abnormal att. values) autotrim becomes available again.
A
first unknown factor is time, how long should an exceedance of one of the trigger values be present to engage this law or revert to ALT 2 again.
Didn't find it yet.
@MR O:
presume those conditions for abnormal law are all 'or's'. However, if the a/c already knew that speed was less than necessary for valid AoA would the logic still take the value and change law ?
They are 'OR'.
Yes, but only if not NCD, @ 2:11:40 stall warning sounded, so there must at least 1 valid speed.
The 2nd unknown factor:
AOAsw is generated by highest AOA value while FCPC uses median (3 ADR) or Average(2 ADR) values. 1 ADR was already outvoted.
If average then didn't exceed the 'abnormal' value it would not enter abnormal law.
Could 2 AOA vanes generate such different values?
In this stall condition, "roll
oscillations that
sometimes reached 40 degrees" and disturbed airflow airflow around fuselage I don't know.
The question was why didn't THS followed SS ND command.
The only 2 reasons this could be justified are the
sort term ND orders or
entering Abnormal Law.
I agree that enhancements have still to be made, several are already introduced before or currently in design.
- 'BUSS' - however only to be used FL <250. (because UAS above FL250 is considered transient)
- AOA valid at CAS > 30 Kts (i.s.o. 60 Knots)
- Pitot tubes (change of supplier)
- Experiments with combined AOA/Pitot vanes.
- QRH
- Training UAS, use of GS.
- CRM / TEM
If crew demand is an AOA indicator and/or THS whooler it should be provided asap.
Other demands e.g. change of law philosophy, protections, RH PFD indication on FDR will require a lot more R&D.