rgbrock1;
Quote:
Not all UAS scenarios are as obvious as AF447. The high altitude / ice particle scenario is a relatively recent addition to the family.
Why? Surely aircraft have been flying at such altitudes for quite some time now. What has changed? 5th Apr 2012 11:57
Perhaps I can help. In climbing through FL200 or so (IIRC), in a B767-200, captain flying, I noticed my CAS gradually decreasing - no EICAS messages, no Master Cautions; what would have been a normal 320kt climb speed, (again IIRC), had decreased gradually to around 250kts - the rate of climb had not increased and I glanced over to the captain's ASI and it read 320kts or so. It was very subtle. We took the reading off the standby ASI and it agreed with the right-side ASI, so we used that ASI. About that time the amber "Rudder ratio" EICAS caution annunciated and an aileron lockout (again, IIRC) annunciated. As the left-side ASI approached 350kts we expected an overspeed warning but it did not occur. We continued the climb and leveled off at flight plan altitude with the right side reading equal to the standby and the left-side pegged on the stop. The right-side autopilot engaged and we continued to destination. On approach, as the air warmed the left-side ASI indication returned to normal. We wrote it up. This was around 1985/86. I never saw it again.
I've thought of that often - what if we had lost all speed indications? There were no pitch-power tables at the time but we could have used the FOM Long-range cruise numbers to keep us safe and monitored pitch, comparing it with past experience. We'd have probably continued; it was night, winter conditions at departure - destination was daylight and a bit warmer. I doubt if ours was the only such experience.
The difficulty with automation is GIGO - if the info isn't available to the flight crew, what's the automation using? The notion of "historical figures" has been broached, (as in, what's the airplane been doing over the past ten minutes") but that's what pilots do anyway, and supplementing such awareness gradually destroys such awareness.
A few have hit upon a very good point - if we fix this, then what will be the next cause? Or do we teach airmanship sufficiently to keep the aircraft safe? While cadet programs teach technical competence, do they teach one how to be "a pilot"?