AF 447 Thread No. 7

[RR_NDB]

Graceful Degradation of the "effective aircraft"

Hello PJ2,

Thank you for your very good answer. Sincere and constructive.

Concerning this segment:

Designers cannot reasonably be expected to anticipate everything that will occur in an aircraft either by mechanical incident or crew action so it must be designed to fail gracefully as some have pointed out here, and this airplane failed gracefully - a loss of speed information does not necessarily result in a loss of control or loss of the aircraft. I don't think it is at all reasonable to expect that a designer will, in the course of such anticipatory processes, design against all outcomes that may or may not obtain in a fully-developed high altitude stall by line crews.

I would like to comment something now (and think and elaborate later):

It seems very, very important to have ALWAYS available a basic set of resources in order to allow the very basic need to just aviate when facing extreme conditions. This is mandatory for a "Graceful Degradation" of the "effective aircraft" (A/C+PF/PM). The incomplete factual information we have suggests the crew may not had this may be adding to the difficult conditions they entered (by their own errors, e.g. "entering WX", lack of perception after AP and A/THR quit leading ultimately to stall, etc.). IMHO the interface design (a real challenge due the complexity of the Systems) may be improved (using lessons from this case) if the HF study being developed and the analysis shows that. The AoA indication may be a result of this process. I am not expecting the need (or possibility) of a major redesign or change in Airbus SAS FBW "protections philosophy", obviously.

Crew confusion must be examined very closely in both Phase 2 and 3. Post-pitch-up the PM was confused by the initial two very short stall warnings for example. Who knows how that may have influenced subsequent perceptions and input?

Important facts that were "important inputs" to the crew (and their perception).

It remains a concern as a former transport pilot that potentially irreversible actions were swiftly, unilaterally taken without adhering to SOPs, CRM communications standards and the handling of abnormals. Cockpit discipline and TEM (Threat/Error Management) processes are drilled into crews in each simulator session and are causes for failure of the ride if not executed to high standards. These processes intervene to prevent rushed actions while providing a basis for calm, measured and coordinated responses by both crew members. This isn't some elusive ideal, this is the normal standard by which transport aircraft are flown, so any unexpected divergence from this standard requires explanations and a willingness to closely examine crew actions where the data supports that kind of an approach. That is why I seem focused on the crew.

Well put, i agree with you. This "organizational aspect" is paramount.

I must admit your "focus" seems correct.

Please, regard my "man machine emphasis" as a very important input to the crew "output". (e.g. the stall warning system below 60kts, etc.). And very probably to be considered as a "contributing factor" in the final report.

Despite having a "technically oriented mind" () i learned very early the importance of the "organizational aspects", certainly with "higher hierarchy".