Gentlemen,Why does the FMC recommend a cruise altitude that is unatainable? For instance, KBNA-KMEM. Granted this is a very short route and probably not realistic, but still I would have thought the FMC would account for this short distance. My second question then is what method is used to determine a plausible crz alt?Thanks,Steve Harwood

I think this is actually the way it works in real life. This cruise altitude recommendation is base on weight mostly, with minor computed mods from temp, and a few other items.However, I dont think that cruise distance even enters this calc in the FMC.Others more familiar, I am sure, will speak up here also.

The TRIP ALT?, its based on what the aircraft can reach and cruise for 1 minute level flight. This is advisory only and provides a means for selecting an appropriate cruise ALT (Lower). It can be optimistic as it does not factor in ALT restrictions on the legs page.

>The TRIP ALT?, its based on what the aircraft can reach and>cruise for 1 minute level flight. This is advisory only and>provides a means for selecting an appropriate cruise ALT>(Lower). It can be optimistic as it does not factor in ALT>restrictions on the legs page.Yes, the FMC does factor any altitude and airspeed constraints on the LEG's page when calculating a CRZ ALT altitude. How? Enter the route with all waypoint constraints first.Then enter all data on the PERF INIT page except a CRZ ALT. The FMC will then offer a TRIP altitude based on your planned route with any waypoint restraints considered. Floyd

>Gentlemen,>>Why does the FMC recommend a cruise altitude that is>unatainable? For instance, KBNA-KMEM. Granted this is a very>short route and probably not realistic, but still I would have>thought the FMC would account for this short distance.> My second question then is what method is used to determine>a plausible crz alt?>>Thanks,>Steve HarwoodSteve,I loaded the FMC with KBNA direct to KMEM, 179 NM. With a -800, 144,000lbs, Cost Index 50, the FMC calculated a TRIP altitude of 29,500 feet with no waypoint contraints.Why do you say your "FMC recommended a CRZ ALT that is unatainable?"The FMC does account for short flights.How are you loading your FMC? A 737 will fly a 179 nm trip very nicely.Floyd

I frequently fly from EHAM to EBBR which is only 100 NM. I love short flights! The cruize alt I choose for this flight is 13000. If I'm not mistaken the TRIP alt usually is something like 15xxx. I usually don't have time for long flights and I don't like to use time accel, so... I wonder how short 737 flights are or can be IRL. Or do they use others planes for such short flights?

I usually make flights domestic in Sweden and those are sometimes very short but still flown with the 737. For instance, a favourite route of mine is ESSA-ESNU and that is less than 100 nm. I still fly at altitudes at or above 30000 feet. Total flight time for that route is less than an hour.

30000ft CRZ for a trip less than 100NM ?Wow !Quite a steep climb, a very very very very short CRZ (I think just the time to tell passengers: "folks, just reached our crusing altitude and just starting our descent" !) and a steep descent ! And maybe a longer flight time than required, if flying at a lower altitude...I flew many short hops (with fs9) in inter-Hawaiaan environment with Aloha's 737-700 and normally cruise altitude was about 14-18k ft, except for the longest sectors that was around FL240/250...I used rw flight plans for these flights.

And now for something completely different... Where did you get those rw plans? I'd like to get some rw plans too! Specially for Europe (starting from EHAM and going no further than 200 NM).

30000' and 100 miles? I fly to LA from KOAK and SWA does not even go that high and that is 400+ and takes about 45-1 hour I guess your NG is a super duper dee duper one ;-).Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/Animation1.gifCaution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

Hi Steve,To help you (and others) out a bit. I thought I'd attach the table for the short trip cruise alt for the -700 with B22 engines.http://forums.avsim.net/user_files/91185.gifThis table is interesting. It will tell you that you reach FL410 for one minute if your cruise distance is more than 225nm. It will also tell you that you will reach FL300 for 1 minute at a route distance of 125nm. This of course is without any corrections at all. And then you have an OPTIMAL height of course which is another animal.So granted that. You don't need no "super dee duper" NG ;-) to reach pretty high on the short legs. Even if FL300 for 100nm seems a bit optimistic. At least for the -700. I would guess you could attain FL300 in 100nm with the -600 though. But looking at a 400+ nm trip I would say FL300 is at least what you shold have. Then of course you have ATC restrictions to take into account... When lightly loaded, as it probably would be because of the little fuel loaded for the trip, the aircraft would have a good climb profile given an unrestricted climb.This is where the differences between the different types in the NG series becomes evident. You can't really talk about the NG when talking performance. As all of them are different shapes and weights they will all have their own performance envelope. So stating the type would be great when we are talking perrformance. ;-)Cheers,

Ok Gentlemen,Thanks for all the replies and the chart. That will be helpfull.Apparently I am doing something wrong so I will try to post some pics.The FMC is telling me crz alt is FL316, the legs page shows FL288. I can see when the computations are done why this could be but as you can see below (I hope I haven't messed the pics up) I get a disconnect 400 ft short of altitude and 15 miles short. I ain't too proud to say I have screwed something up..ThanksSteve Harwood

It's better to show us a screen shot of the CRZ page and PERF INIT page of the same flight.Floyd

Floyd, Here they are. I hope this helps, Thanks.Steve

>Ok Gentlemen,>Thanks for all the replies and the chart. That will be>helpfull.>Apparently I am doing something wrong so I will try to post>some pics.>>The FMC is telling me crz alt is FL316, the legs page shows>FL288. I can see when the computations are done why this could>be but as you can see below (I hope I haven't messed the pics>up) I get a disconnect 400 ft short of altitude and 15 miles>short. >>I ain't too proud to say I have screwed something up..>>Thanks>Steve Harwood> The FMC is showing what you programed into the CRZ ALT - i.e FL316. The second picture show the MCP at 280' so there is no way for it to climb to 316. I wish you would expand the ND a bit more so we could see T/D etc..Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/Animation1.gifCaution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |