HiWhen you came up with the bugfix list for SU2 I asked Randy if the altitude constraint feature will be included. His answer was no. I had a look at the list again and something is not clear for me. I know it might sound offensive but please don't get me wrong:What is the real reason for PMDG not to include this feature in the "final" update for the 600/700? There are so many new things added which are nice but the plane would also fly without it. For those who use the FMC often it is important to use the "basic" features of it. I mean that things which are often used in real live flying should be available in a functional FMC. and the altitude constraints are indeed used very often, especially for SID/STAR.There are alot of comments about that in the flightxpress forum (german) and I just don't want to believe that PMDG is keeping that back only to have something to sell the 800/900 more often with. Was it technically impossible for SU2? Was there just not enough time left?I'm just curious about that. I really don't want to put anyone down! I love the PMDG 737NG (even without altitude constraints ;-) )Thanks for your answers...Martin

Martin-I second this. Using "soft" constraints was a very useful feature in one of the other products. I was under the impression that they were used in real life quite extensively. Curious to see the answer.Mike Smith

Hi MikeWhat do you mean exactly with "soft" constraints? Do you mean just to check if the calculated altitude in the FMC for the waipoint is within the altitude limits?It's just because in real life you aren't allowed to change any part of the SID or the STAR by yourself. Or at least that is the procedure I know...Thanks for the answer anywayMartin

>It's just because in real life you aren't allowed to change>any part of the SID or the STAR by yourself. Or at least that>is the procedure I know...It is normal to have to alter the SID. Sometimes the FMC will produce a route discontinuity on the standard SID as it loads it!It is vital to remove all hard altitudes on the SID. This allows the profile to be flown by ALT SEL, in case you are cleared to higher than the standard SID profile.Every STAR is altered to reflect what you think you're going to fly, to allow VNAV to show a sensible profile. Of course it needs one hard speed/altitude to be able to work properly.Andrew

Martin-I was told that when you enter something like "at or above 12000" or "at or below 12000" this is known as a soft constraint. I was under the impression from pilots I've talked to that this is a very standard method. PSS incorporated it into their FMCs for the 747 and 777 that I have and I found it to be a great tool. I think if you look at some procedures you will see the phrases "at or above" and "at or below". Mike Smith

No use, it will not be in SU2. I wish they were but can only look forward to the 800-900 for this and other things currently not modelled on the FMC. But don't think that there are not ways to accomplish the same resultwithout the feature, there is. Even without this modelled we still have a much more advanced FMC than any other add on to date.... [h4]Best Wishes,Randy J. Smithhttp://img.villagephotos.com/p/2003-5/196432/winglets_lg.jpg

>What do you mean exactly with "soft" constraints? A soft constraint is a point in space (e.g, a FIX) that cannot be predetermined.For example: Consider a procedure where you are instructed to fly runway heading (assume hdg 010) until 4000 THEN turn left hdg 200 and intercept the XYZ R-135.The FMC cannot predetermine at what point you will reach 4000 feet as it is a function of v/s. Likewise, the FMC cannot predetermine the HDG 200 track to intercept the R-135 as that is a function of rate-of-turn and groundspeed. Finally, the FMC cannot predetermine at what point you will actually intercept R-135 until you roll out on the heading of 200.In this example, the ground track (MAGENTA line on the ND) cannot be precisely determined prior to executing the procedure. The ground track must be updated on-the-fly (so to speak ;-) ) as the pilot manuevers the aircraft.Edit: This does not preclude the interpretation of "soft constraint" as described in another post from the perspective of the pilot. This is the issue with 'soft constraint' from the perspective of the developer of the FMC s/w! ;-) .-michael

It would require rewriting major sections of the VNAV code to implement this so the PMDG team decided to wait until 800/900 for this. Unless everyone wants to wait into next year for SU2, which I highly doubt, it'll be a little while longer for this feature. Don't worry though - VNAV works *incredibly* well now and if ATC tells you to cross a fix at a certain altitude it will nail it. You can insert your own altitudes for the at or above/below ones and just have it fly an approximation of what it would do if it was modelling the soft constraints. Believe me guys, this isn't a feature that I'm desperately missing flying the SU2 NG around - would I like it to be there, of course, but it's not something that is terribly vital compared to some of the other fixes and additions made in SU2. (wait till you see the FMC DEP/ARR pages now for instance!)Ryan

Hello EveryoneFirst I'd like to thank you all for your comments. When I read the -600/700 fix list I thought it is worse than it actually is. If I read your posts correctly, it means that if I enter a "hard" altitude the plane will be exactly on that altitude at that fix (like it always were and as it should be ;-) ). but if I enter an altitude at or above/below the FMC will disregard it and see it as a "soft" constraint. I think we can live with that till the -800/900 is available. :-)I thought it was something else that made PMDG not to include it in SU2 but if they would have had to rewrite the VNAV code I think it is the best way to go and to wait for the -800/900.Thanks again to all of you...RegardsMartin