Well, I have to admit that I'm surprised at all this 'incorrect' FMS data, as these should be the latest and greatest wonderboxes...however, 37 years ago one rather advanced/automated wide-body airplane entered service, and when equipped with the Hamilton Sundstrand FMS units unfailingly (at least in my 29 years of operation) presented an accurate picture of the optimum desired cruising altitude, without the glitches mentioned earlier on this thread.
Let's see, it had inputs for...
pressure altitude
TAT/SAT
takeoff weight
actual fuel consumption
distance to destination
cruising mach number....
along with many others, and provided accurate step climb/optimum cruise altitude data, that was right on the money, every time.
The airplane was manufactured by Lockheed, and it is called the TriStar.
And yes, it still works as advertised, even today, for the few remaining operators of this truly remarkable airplane.
