Revived "passengers vomiting in VNAV mode" thread

[kabekew 0]

(MODS, I know you deleted my previous thread about this because I didn't 'sign' my post, so I'm going to sign this three times which is hopefully enough -- but really you and I know you deleted it because you don't like bug reports. And that's fine, but first, deleting the bug reports doesn't fix the bug, and secondly we're all loyal users here and just want to improve your product! So please don't see this as an insult to your awesome product -- I'm just trying to be helpful!)The bug is the current autopilot uses pitch exclusively to achieve speed, which is not realistic. In the real world, and the real 738 there is a balance between pitch and throttle. Currently, the PMDG relies way too much on pitch. This means if ATC assigns a slower speed, the current PMDG autopilot will violently pitch up into a 3-4g climb to slow down as fast as possible. To recreate this, climb out at normal FMC speed (probably around 296 kts) around 15,000, then hit spd intv and dial in 280 kts (to simulate ATC instructing you not to exceed 280kts) and notice how the autopilot violently pitches upward. In the real world this would cause passengers to scream and/or vomit.I posted this bug on another thread and it was deleted. And that's fine -- MODS can delete this thread again, but killing the messenger won't fix the bug. I've seen the autopilot violently pitch upward into a 7700fpm climb and that simply is not realistic for any 737.Again, PMDG, you can delete this thread and ban me for reporting this problem, but that will not increase your sales, and by ignoring this issue I think will just turn people away.Please fix this, PMDG! Put in limits in climb/descent rate, and if you're calculating g forces please limit it to something more realistic. The real 737NG does not pull 4g's+ in a climb like the current build sometimes does,(EDIT) also in the climb, the autopilot should never level off to build up speed as it currently does. The minimum climb rate for a jet is 1,000 fpm which is expected by ATC and listed in the AIM.(Signed)Gabriel Keewaydin--Gabe Keewaydin

[davidz 26]

In LVL CH or VNAV, climbs are conducted with power set to the thrust limit and pitch for speed. I'm not sure why you would want to reduce power to reduce speed in a climb - it would be better to convert than kinetic energy into gravitational potential energy and thereafter, using the excess power to increase climb rate. Even in a Cessna 172 would you pitch for speed.

[rsrandazzo 6,353]

Gabe-We appreciate when our customers come here and help us identify things that can be improved or fixed.When you have spent some time here- you will find that this is the case. I'm not sure why- but you seem pretty paranoid that we might ignore someone coming to use with a legitimate issue. We *almost* never do. We do ignore jerks, self-important grandstanders, and anyone who seeks to draw attention to themselves by acting like the back end of a horse.So- my suggestion to you is that you keep the tone of your posts civil, and conversational. Your post above is more intent on being insulting than factual.Your earlier attempt at this thread was deleted in compliance with forum guidelines because you failed 8 times to comply. Ignorance of the rules is not an excuse- but rather than delete BOTH of your threads I elected to leave the other one and throw a warning in there to help you assimilate AND, I thought the conversation was interesting and might lead someplace. (I was right- and rather than telling us that we delete posts that report bugs- perhaps you should thank Ryan for spending his friday evening trying to validate your post... See? No reason to be paranoid here...)So, bottom line: Act like a reasonable person and we'll treat you in kind. Act like a self important pompous putz- and we'll just delete/ignore.Now- as to your post here: Your understanding of VNAV logic and what our VNAV logic is accomplishing are not accurate. (There is always danger in being so specific in your wording...) All the same, I'll have one of the fellows take a look at your report- and if he is able to weed through all of the insults in your post without growing tired- we'll see if we can't figure out why you are seeing something that appears incorrect to you.Who knows- it might actually lead someplace! (See? No reason to be paranoid here....)

[SilvioSilva 4]

That's it!

[martin-w 3,235]

(MODS, I know you deleted my previous thread about this because I didn't 'sign' my post, so I'm going to sign this three times which is hopefully enough -- but really you and I know you deleted it because you don't like bug reports.

Gabe, I'm pretty sure you have something valuable to add to this forum, like your previous topic for example in regard to the FMC peculiarity. I too see that issue and am grateful for your input.However, you need to take a step back, and refrain from accusations. PMDG do have a policy in regard to signed posts. It's existed on this forum for a long time and is nothing to do with the topic of conversation, or bug reports. Do a search and you will see that PMDG are keen to fix bugs when they are identified, and verified.Re the pitch issue...The only pitch issue I have seen, is in the 600/700, in regard to takeoff. If My speed doesn't match the bug speed before I engage the autopilot, then rather than a smooth pitch change when the AP is engaged, I see a sudden jerk up in pitch.

[rsrandazzo 6,353]

Martin-I've seen this aggressive pitch change in the 600 and 700 as well. Obviously, good operator technique dictates have thing airplane in trim and stable- as you suggest. That being said, we are going to see if we can get some data from the sim to see if the airplane responds as aggressively in this circumstance- perhaps it will lead to adjustment. Perhaps it won't.. hard to say at the moment.

[martin-w 3,235]

Thanks Robert, very much appreciated. By the way, is the following worth investigation...

In the real aircraft gear would give you more drag than that and the engine goes to app idle AFTER 3 green lights, not when gear is commanded down like in the NGX.

Sorry to add to your workload.

[rsrandazzo 6,353]

Martin-No. The drag value is based on official values already...The approach idle was tweaked some in SP1 based upon a review of data from the simulator. Our contacts up at test flight agree with the SP1 version as it stands now. (You will notice I am not taking a position... I am trusting the experts here.)We've gotten feedback from a number of NG crew- and their feedback is rather "goldylocks." (Too little, too much, just right, in even quotients...)

[martin-w 3,235]

Fair enough on the drag value.

[Kimber 8]

I have noticed that the B737NGX can pitch up aggressively sometimes I have started (ish) to work out when it’s most likely to happen so I sometimes switch off VNAV and set the climb speed myself – this is something that I have seen pilots do at the airline I work for, I shall ask them if they do it for the same reason.I guess like so many aircraft the Boeing 737 can have a lot of spare power, especially when there is a lighter load but I do agree there should be something done to stop this fantastic little aircraft from trying to climb like the ‘Space Shuttle’!Kimberly Richmond-Jones

[martin-w 3,235]

I have noticed that the B737NGX can pitch up aggressively sometimes I have started (ish) to work out when it’s most likely to happen so I sometimes switch off VNAV and set the climb speed myself – this is something that I have seen pilots do at the airline I work for, I shall ask them if they do it for the same reason.

When do you find it normally happens Kimberly?Do the pilots at your airline switch to FLCH or VS?If it's climbing too fast, you can always switch to CLB2 of course.

[JC75 22]

Just one observation in this...the minimum rate of climb or descnt. Is my understanding that 500ft is the minimum rate that should always be commanded in order to comply with atc. And thus the autopilot should always command this even when it's pitching up or down to adjust speed. I too have noticed a levelling off on times. From my side of the world I generally always observe a a slow down in climb as acceleration occurs, but not as significant as is seen in the ngx, likewise for descent. So there may be some value in the ops post regarding pitch and speed.

[denver69 0]

I have to agree, just as I was reading this in a VNAV climb. For no real reason it thrust the stick back and the aircraft shot up to 2500 fpm. This seems to happen in turbulence and may be the pitch variant of the roll problem in turbulence. I've got the roll problem fixed with FSUIPC but the reaction in pitch would make all the PAX never want to fly with me again. No wonder why the random load gives me so few!I to would like to get to the bottom of this one.

[Dumont 9]

Original PT/BRCreio que consegui entender o que estão falando, o afundamento, ou levantamento abrupto do nariz quando alteramos VS.Talves seja o caso de iniciar a modificação da atitude de neutra para positiva ou negativa de uma maneira mais progressiva.Bem, me desculpem se não for esse o problema, tenho grandes dificuldades de comunicação, os tradutores nem sempre funcionam como desejamos.Uma certeza eu tenho, nenhum passageiro abriu a porta da cabine para jogar o saco de vomito em mim !Translated by GoogleI believe that I could understand what they are talking, subsidence, or abrupt withdrawal of the nose when we change VS.Maybe the case is starting to change the attitude of neutral to positive or negative in a more progressive.Well, excuse me if this is not the problem, I have great difficulty communicating, the translators do not always work as desired.I have a certainty, no passenger opened the cabin door to throw the bag of vomit on me! João Alfredo

[kjjj11223344 48]

I have noticed this, but in my case it only happens when 1)I have realistic autopilot turned off because I have just cleanly reinstalled the Ngx, and the plane isn't properly trimmed or 2)when I have real weather chosen in FSX and the wind suddenly changes direction (since I don't have fsuipc). But I don't think a real ng would be faced with these condition anyway.