incredibly steep decents and space shuttle take offs

[Jet_Airliner 0]

Forgot to say, that I am not sure that it's actually PMDG issue!Could be weather problem. People who has the same issuePlease try to put "10" in FSUIPC smooth wind changes near aircraft SECOND window and post if it helps.

[Fabo 213]

Ryan: depends on the operator, really. But my best guess it is on the high side of the mark, quite possibly above 100, 150. Remember if you get a BBJ, its quite possibly because you want to save time, before all.

[HighFlyer310 21]

Lets try and keep this "autopilot" thing in perspective here. IRL, pilots have to kick the automatics off all the time to prevent it from doing funky, erratic things with the aircraft. What I see is people seem to be to scared to hand fly the airplane. You cant expect to engage the autopilot before the gear is up and have it be a smooth experience.. thats what your job is for, the pilot. At the very least, on takeoff.. I always hand fly through to accel height, pitch over, trim off the pressure and engage the A/P. Most of the time I hand fly up past 10,000'.. its really not very hard with the F/D doing all the thinking for you. On descent.. remember that you have to give the airplane a head start down, running right into the descent path with the engines spooled to CRZ power is not a good idea... try to initiate the descent 5-6 miles prior to the T/D using the DES NOW feature, it allows the engines to spool down and begin a gradual descent to come up underneath the descent path, instead of diving for it and overshooting.

[Paul Deemer 13]

Okay here is a good example. If you use VNAV for descent with a cost index of 36 its going to descend at 280 knots. If you use some rediculous cost index of 100 or more it's going to descend at 330 knots.So your at Cruise at 36,000 ft doing 260 knots and then it is time to descend. The NGX is gonna dive bomb until you get from 260 knots to 330 knots which is 70 knots faster. But if your at 260 knots and going to descend at 280 knots which is more reasonable then it only going to speed up 20 knots.Just try using a lower cost index like the real world and you will notice an improvement. Just because they use a cost index of 70 to 100 in the MD-11 and 747-400 does not mean this is universal and applies to the 737-NGX as well.

[Fabo 213]

I... don't think. In descent you are in VNAV PTH mode, so the FMC should primarily track pre/computed descent path and only then should it speed up by the way of thrust.

[Paul Deemer 13]

I... don't think. In descent you are in VNAV PTH mode, so the FMC should primarily track pre/computed descent path and only then should it speed up by the way of thrust.

It is not going to use thrust to increase to 330 knots. It is going to descend at whatever angle it needs to to reach 330 knots as quickly as possible. Whether that is how the real bird works or not I do not know but that is how the NGX works. Try it yourself. At 36,000 feet and at the begining of your descent put the throttles in the idle position and if your cost index is 100 or more it is going to start diving until you reach 330 knots, even if it has to go to a 6000 fpm dive. It is not going to increase thrust.

[Jet_Airliner 0]

Okay here is a good example. If you use VNAV for descent with a cost index of 36 its going to descend at 280 knots. If you use some rediculous cost index of 100 or more it's going to descend at 330 knots.So your at Cruise at 36,000 ft doing 260 knots and then it is time to descend. The NGX is gonna dive bomb until you get from 260 knots to 330 knots which is 70 knots faster. But if your at 260 knots and going to descend at 280 knots which is more reasonable then it only going to speed up 20 knots.Just try using a lower cost index like the real world and you will notice an improvement. Just because they use a cost index of 70 to 100 in the MD-11 and 747-400 does not mean this is universal and applies to the 737-NGX as well.

Each flight CI is different, depending on weather (especially depending on wind). Best you can do, is to use fixed speed of 280/.780 for climb and reversed for descent.thats given in ftcm as econ speed as far as i remember.

[Paul Deemer 13]

Each flight CI is different, depending on weather (especially depending on wind). Best you can do, is to use fixed speed of 280/.780 for climb and reversed for descent.thats given in ftcm as econ speed as far as i remember.

That is why I use a cost index of 36. Cause it will always descend at 280 knots exactly.

[RYR738 9]

@ OP.If you are seeing ascents and descents as high as 6000 fpm, then YOU are doing something wrongOR it could have something to do with your control hardware setup.I very rarely see more than 3000 during climbs or 2000 during descents.This has nothing to do with cost index really.( better screenshots would be a big help !! ) Fred.

[rocketfs 2]

Alright since this topic talks about CI - what do BBJ's use? When I fly the -800 I use 1/3 fuel, and usually light payload. I've been doing a CI of 88. And I get these quick/fast climbs/descents. What should I be using? Should I just weigh down the plane more and put a CI of like 30?

Something between 10 and 30 according to this Boeing doc:http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/article_05_3.htmlBert Van Bulck

[ryanbatc 13,035]

@ OP. If you are seeing ascents and descents as high as 6000 fpm, then YOU are doing something wrong OR it could have something to do with your control hardware setup. I very rarely see more than 3000 during climbs or 2000 during descents. This has nothing to do with cost index really. ( better screenshots would be a big help !! ) Fred.

Hi, I see you're a rw pilot.I have issues like the OP. I realize I must be doing something incorrectly. Just don't know what it is lol.Here's how I enter stuff in the FMS:Payload normally 4000 rear 3000 front. About 10-20 pax. Fuel 1/3 cause I do flights less than 300 miles normally. takeoff flaps 5, and I usually get really low V2, like 135-145. So in my speed window I enter v2+20, so anywhere from 155-165. For the autopilot, I "arm" VNAV and LNAV on the ground. When I takeoff I engage CMD A around 500 AGL and that's when the thing just rockets skyward. Eventually it slows as I retract my flaps (maybe I'm doing this too early??). I usually retract flaps as I pass the airspeeds on the tape. But then it skyrockets again (mainly between +4000 to +6000 fpm) until it reaches 10,000 ft, where the climb slow to gain airspeed, then the cycle repeats.

[Paul Deemer 13]

When a full load is 162 pax in the 737-800 why would you only take 10 to 20? That's why you are climbing like a Rocket! Probably why the real world pilots on here are not seeing what some of you are seeing because it would never even occur to them to take off that light.I fly the 737-800 Winglets model exclusively. On the average even if I am doing a 45 min flight from KIAH (Houston) to KAUS (Austin) I have 140 to 162 pax on board and around 11,400 lbs cargo and make the trip between 17,000 and 18,000 ft depending on which direction of flight. At Max capacity of 162 each passenger can bring 2 bags weighing 35 lbs each.As for the Space Shuttle Title of this thread: The 757-200 is notorious for being overpowered. That is why they use it down at SLLP at 13,225 feet. If you took off with 10 to 20 pax in a 757-200 you actually could take off at the same angle as the Space Shuttle. Here is the proof!

So why are you suprised that a 737-800 with 20 pax and 7,000 lbs cargo is climbing at 6,000 fpm? Load it up to the max and you notice a significant change in behavior.

[Paul Deemer 13]

If you are seeing ascents and descents as high as 6000 fpm, then YOU are doing something wrong

Fred I know what they are doing cause it happened to me before. You can reproduce it easy.Set a Cost index of 100 so you get a 330 knot descent rate. With VNAV on at 36,000 feet at your TD the plane will start doing 5,000 to 6000 fpm until it reaches 330 knots. I think the issue is people setting their cost index too high and at 330 knots no wonder they can't slow down.

[michal 44]

because it would never even occur to them to take off that light.

No, they take off with whatever cargo is thrown at them (within legal limits), if for example they reposition aircraft to a neighboring airport you bet they will be flying very light.But one thing pros know is how to handle the aircraft within its full design envelope.

[NM5K 1]

Okay here is a good example. If you use VNAV for descent with a cost index of 36 its going to descend at 280 knots. If you use some rediculous cost index of 100 or more it's going to descend at 330 knots.So your at Cruise at 36,000 ft doing 260 knots and then it is time to descend. The NGX is gonna dive bomb until you get from 260 knots to 330 knots which is 70 knots faster. But if your at 260 knots and going to descend at 280 knots which is more reasonable then it only going to speed up 20 knots.Just try using a lower cost index like the real world and you will notice an improvement. Just because they use a cost index of 70 to 100 in the MD-11 and 747-400 does not mean this is universal and applies to the 737-NGX as well.

That seems a bit weird though.. It should descend at the mach speed at a fairly normal,but likely brisk rate until it merges with the 330 knots. I'm not sure what the mach speedwould be at FL360 at 260 knots.. Mach .76-78 or so??I've flown a few flights with pretty high CI, and didn't really have any problems with itdiving like a rock. The descents were pretty normal, just fast speeds.If you are at FL360, the plane will be using mach speed, not IAS. And if you start adescent, it should act about the same as any other descent. Just faster.. It's notgoing to be running mach speed and suddenly decide to switch to IAS before it'stime.. Which at a high CI, will be in the mid to upper 20k ft range.Also, if the CI is that high, the mach speed will be pretty high too.. mach .79-80 range..It's gonna hold that mach speed until it see's the 330 knots, and then it will switch.Lately, I've quit running the high CI's, and have been using a more real world numberaround 35 or so.. 40 is about as high as I've been going lately.Anyway, I never saw anything really unusual using a high CI.. Just faster speeds.I get some pretty good climb rates with the 600 BBJ I run. It's loaded pretty lightand it's not unusual to climb out at 4000+ fpm in the earlier parts of the climb.But I don't see those high rates when running a loaded down Southwest flight.It's all in the weight as far as the high climb rates.I run the light 600 BBJ a lot at night when all the scheduled airline flights arekaput, and most of the big company pilots are in hotel rooms asleep. :/Even if I load a lot of furniture onto the plane, it's still pretty light withless than 30 people on board. Often I'll have less than 15 pax..Climbs like a scalded house cat. :)BTW.. Is that *the* Capt Billy Bob that is on u-toob?Your video's are a hoot.. :)