Insufficient information?
On other threads it has been mentioned (many times) that the primary trigger for the B737 Max MCAS debacle was cost-driven avoidance of extra pilot training for this system.
It brought to mind another 'insufficient information' situation from a few years ago before I retired. On our non-FADEC RB211 B757s it was my habit to manually tweak the throttles (autothrottle engaged) to match the N1s as long as the resulting EPRs were closely matched. This reduced the 'beating' wah-wah-wah noise and thereby improved cabin ambience.
On our FADEC CF6-80C2 B767s I noticed early on that the N1s were always exactly synchronised, even if there was slight throttle displacement (no EPR gauges). A bit of experimenting showed that if one displaced one of the throttles the N1s would fluctuate for a few seconds and then re-sync. If the throttle discrepancy was increased the N1s would still re-sync until the displacement exceeded a certain limit, after which the N1s would de-sync to match the individual throttle settings. Aligning the throttles again would restore auto-sync.
There was no info about this behaviour in any of our manuals. A request to Boeing for info confirmed the behaviour and gave details of the sync range. IIRC the auto-sync was activated - with the signal determined by the leading throttle position - when the N1 demands of the two throttles were within 5% of each other.
My judgement was that this snippet of info was important enough to warrant informing pilots about but apparently others were not of the same opinion - it was perhaps considered 'not necessary to know' stuff rather than 'nice to know' or 'need to know' or 'must know'.
MCAS was surely a 'must know' item. I wonder in these cost-obsessive times whether other significant items are in the wrong categories.
Last edited by Discorde; 1st May 2022 at 15:57.