Originally Posted by
Owain Glyndwr
@infrequently flier
Well obviously the certificating authorities (all ten of them together IIRC) thought so!
Yes, and that is what the BEA more or less said - the behaviour is not compliant with the regs, but it is ok (implied) because the certification authorities said so, based on special conditions.
I found it slightly odd that they put the onus on the opinion of the certifiers rather than say something more definite like "it is ok because it complies with special condition XY which replaces regulation Z", and it was that that had me going off looking for the actual special conditions when I read it.
Er - which other bit?
I highlighted the bold bit simply to emphasise that the stick force vs speed characteristics described in the FAA document rrr cited are not relevant to A330 certification
My bad - I confess I skipped the detail from rrr's post because my understanding is that anything in that section of the regs is inapplicable because the whole section is replaced by the special condition - unsuprisingly because it is all around positive static longitudinal stability, which the fbw 'bus does not have.
The bit of the special conditions that got my attention was this:
Control laws that result in neutral static stability throughout most of operational flight envelope may be accepted in principle subject to:
- adequate speed control without excessive pilot workload
- acceptable high and low speed protection
ALT2B is, however, neutral stability and
without speed protections, is it not ? BEA seems to think so, at least to my reading of 2.2.5 in the report (p186-7 in English pdf). Condensing a bit:
Protections are lost.
...
When there are no protections ... <behaviour> ... judged to be acceptable by the certification authorities by taking into account special conditions and interpretation material material; i.e. that the presence of flight envelope protections makes neutral longitudinal static stability acceptable.
I've substituted "; i.e. that" for ". Indeed" at the end there, because it is one sentence in the original French and I think the intended sense is that they are specifying what the special condition
is.
So, essentially, the behaviour of the a/c
without protections was accepted by the certification authorities
because of the protections. Now I thought that was a rather odd statement and possibly a veiled criticism of said certification authorities, but maybe I am the only one who reads it that way.