Chris, we had the Smiths fms in our A306 and the mode was known as Profile.It would only allow one altitude constraint and when it reached the descent point it commenced a 285kt descent at idle thrust. Keeping it on the path was down to you by varying thrust. The prediction of whether you were going to be high or low at the constraint was shown as long or short but was quite accurate. There was no development in the 17 years we had it ,and the airline binned it a few years ago for the Sperry.I remember being told that the Smiths boffins all went to Honeywell to improve their fms.
The Sperry we have now ignores all of the altitude constraints in the fms on departure and it flies quite a crude descent path. Invariably it will sit about 10k slow of the descent speed and if you make it recompute the path and it realises it is low it will try and climb the aircraft to meet the path!The majority of my colleagues rely on LVL/CH or V/S.
Last edited by tubby linton; 28th February 2013 at 17:13.
Reason: Extra info.