hi, when i create a flightplan which includes a sid and star, when im nearing the descent rcd4 and vatsim always tell me to descend to flxxx which is approx. 40 -50 miles prior to the tod in the nd.if i dont fly with atc and descend at the calculated tod i usually end up busting the altitude or have to descend steeply.i dont know why this happens ive tried exporting flightplans from fsbuild but still have the same problem,when pilots program their fmc with a arrival do they put a runway in as well, ihave been doing this so maybe this is where im going wrong. any help please, jim mcpherson

Jim, what do you mean by a steep descent? The rate of descent varies considerable with altitude due to the nature of altitude and groundspeed (the higher you are the faster you go in the thin air). Initial rates of descent in the FL30's can be up to 3000fpm and this is normal. Down below FL180 they will taper off to about 1200-1800 fpm.Back to ATC. Real world ATC has different controllers working hi, med and low airspace and the guy in hi sector will want you down below FL330 so he can hand you off to the mid sector and this may happen earlier than your TOD. Also in the real world, ATC will often clear you for a descent at pilot's discretion (the simulations ignore this), which means you don't have to descend until either you want or they prod you into a 'start descent now' request. So, if you want to play with RC or vatsim, then you gotta follow those clearances regardless of where your TOD lies.You can always press the 'start descent now' button and she will descent at about 1000 fpm until running in to the vertical path. If the guy at vatsim wants you lower he will tell you.

Jim, what do you mean by a steep descent? The rate of descent varies considerable with altitude due to the nature of altitude and groundspeed (the higher you are the faster you go in the thin air). Initial rates of descent in the FL30's can be up to 3000fpm and this is normal. Down below FL180 they will taper off to about 1200-1800 fpm.Back to ATC. Real world ATC has different controllers working hi, med and low airspace and the guy in hi sector will want you down below FL330 so he can hand you off to the mid sector and this may happen earlier than your TOD. Also in the real world, ATC will often clear you for a descent at pilot's discretion (the simulations ignore this), which means you don't have to descend until either you want or they prod you into a 'start descent now' request. So, if you want to play with RC or vatsim, then you gotta follow those clearances regardless of where your TOD lies.You can always press the 'start descent now' button and she will descent at about 1000 fpm until running in to the vertical path. If the guy at vatsim wants you lower he will tell you.

hi dan, i was descending down from fl240 at 2000fpm so i guess this is not too fast, i thought the fmc tod was the best way to plan your descent but using level change i sometimes could not make the altitude constraints. thanks, jim mcpherson

Level change pulls throttles to idle and you descend at the FMS determined speed.Using MCP SPD and V/S will give you more control over the descent and you can use the green banana to judge if you are over or under desired target.Yeah, 2000 fpm is not much in a jet above FL180.

I haven't used RCV4 for a while (testing V5) but as I recall if you have the comms and control of the aircraft, the latter a must for PMDG, there might be a pilot's discretion option in the first or second page of the menu.Another consideration is that RC will assign a crossing restriction at 11,000 (or FL110 non-FAA) or 12,000 (or FL12,000) except where it is too low for terrain at a forty mile radius from destination. I place using the FIX page and entering the destination ICAO and /40 a range ring around destination during preflight FMC prep. I then start down when directed at first with FLCHG and then watching the "bannanas" insure they don't cross the range ring. I use V/S as necessary keeping an eye on IAS and N1 to stay as close to idle and FMC speeds to insure maximum efficiency.The FMC TOD is predicated on a constant descent approach to the airport. The last I read some time ago was that the FAA was leaving this feasibility to individual airport site ATC managers. While ATC will cooperate in attempting to assist airlines in fuel efficiency, they do not want to five up the tool of vertical separation in dense areas and close in want established floors to accomplish that. These floors are also used as hand-off windows for ARTCC to TRACON control transfer.

hi, when i create a flightplan which includes a sid and star, when im nearing the descent rcd4 and vatsim always tell me to descend to flxxx which is approx. 40 -50 miles prior to the tod in the nd.if i dont fly with atc and descend at the calculated tod i usually end up busting the altitude or have to descend steeply.i dont know why this happens ive tried exporting flightplans from fsbuild but still have the same problem,when pilots program their fmc with a arrival do they put a runway in as well, ihave been doing this so maybe this is where im going wrong. any help please, jim mcpherson

Jim,Are you following the Vertical Deviation cues? If you are starting down 40-50 miles early, once you've started the descent it should say 9999' low, and then you should meet it at some point in the descent if you're descending too shallowly.Ideally, you leave the plane in VNAV and let the FMC start the plane down at the TOD. If ATC starts you down early, use the "Descend Now" button. Like Dan said, that'll put you in a 1000fpm descent until you meet VNAV PATH and that's the most efficient path.Are you getting "steep descent after XXXXX" or "unable next alt" messages?As for selecting runways/approaches my current company wants us to pull up the destination ATIS and load the STAR, transition, and approach before we leave the gate; my previous employer wanted whatever you were filed for and maybe the STAR, but we didn't load the runway until we were briefing the approach.Have fun.

Jim,Are you following the Vertical Deviation cues? If you are starting down 40-50 miles early, once you've started the descent it should say 9999' low, and then you should meet it at some point in the descent if you're descending too shallowly.Ideally, you leave the plane in VNAV and let the FMC start the plane down at the TOD. If ATC starts you down early, use the "Descend Now" button. Like Dan said, that'll put you in a 1000fpm descent until you meet VNAV PATH and that's the most efficient path.Are you getting "steep descent after XXXXX" or "unable next alt" messages?As for selecting runways/approaches my current company wants us to pull up the destination ATIS and load the STAR, transition, and approach before we leave the gate; my previous employer wanted whatever you were filed for and maybe the STAR, but we didn't load the runway until we were briefing the approach.Have fun.

hi, the first constraint on the star is d10 tla expect to cross max fl180, this is programed in the fmc as 18000b i meet the constraint ok. then according to the star tartn expect to cross at 7000, but the fmc has calculated that i wiil cross tartn at 9000 so i change that to 7000 and then i get fmc message des path unachievable. when the star says expect to cross at 7000 must you adhere to that or will it be ok to cross at 9000. my flight is egbb depart runway15 trent3e sid to egph tweed1a arrival thanks jim mcpherson

Depending on the distance between D10 TLA and TARTN. A normal descent would have those two altitudes about 44nm apart. If they are close you need to cross D10 TLA lower, which is okay since it is an AT OR BELOW constraint. The 737 FMS is not very good at conditionals, and you should determine your preferred altittude at D10 TLA.I would delete the 18000B, and see what altitude the FMS calculates for crossing that fix to be at 7000 at TARTN. Odds are it is much lower than 18000 and you don't need a constraint there at all.

hi, the first constraint on the star is d10 tla expect to cross max fl180, this is programed in the fmc as 18000b i meet the constraint ok. then according to the star tartn expect to cross at 7000, but the fmc has calculated that i wiil cross tartn at 9000 so i change that to 7000 and then i get fmc message des path unachievable. when the star says expect to cross at 7000 must you adhere to that or will it be ok to cross at 9000. my flight is egbb depart runway15 trent3e sid to egph tweed1a arrival thanks jim mcpherson

Jim,I think I'm looking at the latest version of the arrival, and I don't see Tweed1A having a TLA/-10 restriction, but maybe we're looking at different charts.When are you putting those restrictions in the FMC? If you start monkeying with them near TOD or after the plane starts down, you are setting yourself up for problems. If you have all the restrictions in place before, say top of climb, the FMC will start you down based on the "most restrictive" restriction. In other words, if there's nothing preventing you from going to 7000' (other restrictions) it doesn't make sense that the plane can't do it.As far as 7000' or 9000', it's whatever ATC gives you. See the note from the STAR:DESCENT PLANNINGPilots should plan for possible descentclearance as detailed in the table aboveand in addition should anticipateclearance to Minimum holding Level (FLequivalent 7000) by the entry fix(TARTN).ACTUAL DESCENT CLEARANCE WILLBE AS DIRECTED BY ATC.Make sure that you've got your crossing restrictions in early. You really shouldn't be getting that DES PATH UNACHIEVABLE message.

Jim,I think I'm looking at the latest version of the arrival, and I don't see Tweed1A having a TLA/-10 restriction, but maybe we're looking at different charts.When are you putting those restrictions in the FMC? If you start monkeying with them near TOD or after the plane starts down, you are setting yourself up for problems. If you have all the restrictions in place before, say top of climb, the FMC will start you down based on the "most restrictive" restriction. In other words, if there's nothing preventing you from going to 7000' (other restrictions) it doesn't make sense that the plane can't do it.As far as 7000' or 9000', it's whatever ATC gives you. See the note from the STAR:DESCENT PLANNINGPilots should plan for possible descentclearance as detailed in the table aboveand in addition should anticipateclearance to Minimum holding Level (FLequivalent 7000) by the entry fix(TARTN).ACTUAL DESCENT CLEARANCE WILLBE AS DIRECTED BY ATC.Make sure that you've got your crossing restrictions in early. You really shouldn't be getting that DES PATH UNACHIEVABLE message.

hi, sorry my mistake i meant tara30 not tla10. i set up the above flight again, but did not use atc so i could use the fmc tod, i included a destination runway with a r/way ext. of 15 miles, the 18000b was selected and tartn at 7000 also selected but still got a des path unachievable, between waypoint tla10 and the next waypoint i had to descend 10000ft in a distance of 22 miles . so i started again and changed 18000b to 12000b and tartn at 7000ft i was able to complete the flight. is this normal that you have to alter the altitude and speeds to fly the star. i downloaded the flightplan from vroute, i also used fsbuild but again had to change the alt. and speeds to do the flight. i will try another flight tomorrow . thanks, jim mcpherson

hi, sorry my mistake i meant tara30 not tla10. i set up the above flight again, but did not use atc so i could use the fmc tod, i included a destination runway with a r/way ext. of 15 miles, the 18000b was selected and tartn at 7000 also selected but still got a des path unachievable, between waypoint tla10 and the next waypoint i had to descend 10000ft in a distance of 22 miles . so i started again and changed 18000b to 12000b and tartn at 7000ft i was able to complete the flight. is this normal that you have to alter the altitude and speeds to fly the star. i downloaded the flightplan from vroute, i also used fsbuild but again had to change the alt. and speeds to do the flight. i will try another flight tomorrow . thanks, jim mcpherson

Normally, I don't alter the stars. Sometimes I'll alter the speeds near the end of the STAR or at the beginning of the approach so I have a more comfortable speed (e.g. 200kts at the IAF).I'm not sure why the FMC would be able to do 12000B but not 18000B. Doesn't really make sense.If you check out the DESC page, the V/R (or is it VSR? - I forget) cue tells you the the Vertical Speed Required at your current ground speed to make the selected restriction. If that or the Vertical Deviation are too high, the computer is going to say Path Unachievable. Check those out.I think someone mentioned that if you delete the restriction, the altitude that the FMC predicts you'd be at pops up in small font. That should also be something reasonable.The TARTN/-30 18000B is an odd restriction, since that'll actually put you at ESKDO/-5. I don't think the FMC will let you select TARTN/-30 since it's before the ESKDO fix (and that's why you'd need to select ESKDO/-5).