Leveling off in my 737

[selkan]

Hi Pete, firstly, you may recal I recently posted about 'jitters' with my PFC Yoke. You were quite right, it was a worn out Potentiometer. I contacted PFC who sent me a new one, and have fitted today. Tested and all is now S M O O T H. So just a word of thanks for pointing me in the right direction.

If I may, I just wondered if you have any experience of the following. I have latest FSUIPC/Wide Server/Client, and latest PFCFSX.dll This probably has nothing to do with your Drivers, but getting any sense out of Microsoft is, well, difficult to say the least. It is simply when leveling off in my 737 sim (using default 737-800), I get quite a lot of ups and downs as I level off; i.e. say I want to level off at 35,000ft. The plane starts to level off at about 34,600, then at about 34,800 I can get a sudden climb of about 1000/12000 ft Per Minute before she will then level off. All in all quite a few ups and downs. On the decent, leveling off is much smoother. I should mention all of this is using the PFC MCP and Flight Plane set in the FMC.

Hope you don't mind me asking you this here, but thought you might have some direct experience and possible answers.

Regards, Steven

[Pete Dowson]

It is simply when leveling off in my 737 sim (using default 737-800), I get quite a lot of ups and downs as I level off; i.e. say I want to level off at 35,000ft. The plane starts to level off at about 34,600, then at about 34,800 I can get a sudden climb of about 1000/12000 ft Per Minute before she will then level off. All in all quite a few ups and downs.

Well the default models are pretty bad in any case. After initially trying the default 738 when I first got FSX I abandoned it as pretty hopeless. I currently use the PMDG FS2004 one transplanted to FSX (without its panels ,etc, as I use Project Magenta).

Is it YOU levelling off you are talking about, or the autopilot? I assume you mean the A/P as it is 100% normal for a 737 to be on A/P. However, if it is you, manually flying, then it may simply be the trim is too coarse. Trimming is all important.

In general, you or A/P, the other normal problem causing overshoot is too high a climb speed for the weight -- the momentum is greater than the autopilot can cope with. And that default 738 is ridiculously overpowered in the first place. It climbs far too fast -- at FL350 climb rates are quite low because of the thin air. Don't forget, also, that the A/P you are using was really designed for a Cessna. The fiddle factors to make it attempt to control heavier planes are just thatr, fiddle factors. This is why decent third party add-on aircraft like PMDG, LevelD and even Ariane replace the autopilot with their own. Using Project Magenta I am of course also not using FSX's A/P.

On the decent, leveling off is much smoother. I should mention all of this is using the PFC MCP and Flight Plane set in the FMC.

Oh. What is the PFC MCP connected to? In other words, what autopilot are you using?

Regards

Pete

[selkan]

Hi Pete, thanks for response. Yes, I am using the Auto Pilot when I am leveling off. This is dictated by the flight plan already set up in my PFC FMC.

I am using the PFC MCP/autopilot, (hardware). This is connected directly to my main Server P.C. running projectmagenta MCP program. (USB)

Thanks, Steven

[Pete Dowson]

I am using the PFC MCP/autopilot, (hardware). This is connected directly to my main Server P.C. running projectmagenta MCP program. (USB)

Your question, then, should probably be directed to Project Magenta support, as it is their autopilot making this mistake. However, I can guess that the answer will more or less be as I have already told you. The FSX 738 is a poor model. What will make it behave worse with PM's MCP is not using a tailored Aircraft characteristics definition in the FMC folders -- have you got one designed for the way that aircraft performs? I've not seen one. The best data for the PM FMC/MCP seems to be for the PMDG model.

You may wish to visit the PM (unofficial) forums http://www.mycockpit.org/forums/forumdisplay.php?s=884 .

Regards

Pete

[selkan]

Hi Pete, you have beaten me too it; woke up in night, cold sweat, realizing I had stated something quite wrong in my last post. I said my MCP was connected to my Main Server P.C. via a USB cable. You probably guessed as much, but it is connected to a Serier Com Port, which is then detailed/set in the MCP ini file. Just to put the record straight for anyone else reading all this.

Actually, I do have a specific aircraft characteristics definition file set up in my FMC/CDU Folder. I seem to remember it was by someone called Steve Ryling. I believe some years ago Projectmagenta gave me a link to his 'files'. I expect you may have heard of him?

Anyway, thanks Pete, and I will drop a line to Projectmagenta to see what they say.

Regards, Steven

[Pete Dowson]

Actually, I do have a specific aircraft characteristics definition file set up in my FMC/CDU Folder. I seem to remember it was by someone called Steve Ryling. I believe some years ago Projectmagenta gave me a link to his 'files'. I expect you may have heard of him?

Yes, but all of Steve's data files were made in 2003 and were applicable to assorted add-on aircraft at the time. I'm actually using Bob Scott's PMDG 737-700 file, which specifically matches the PMDG 700 I am flying. That's important -- match the data to the performance characteristics of the aircraft you are actually flying!

The problem, as I keep explaining, is that the default 737-800 in FSX is a poor (read "bad") model. No one has made a proper data file for it to fly in PM as far as I know -- probably because it isn't worth it, it is such a bad aircraft.

Anyway, thanks Pete, and I will drop a line to Projectmagenta to see what they say.

Well, probably the best they can do is to try to advise what bits of the file to change, or more likely to alter some stuff in the default Aircraft.CFG file. Really you need specialist advice from an FS aircraft modeller, someone who knows about these things. There's no one in PM who models aircraft, though Thomas Richter, who was associated with PM for a while, is quite good in this area.

The advice you may get is to find a better FSX aircraft to fly. None of the default ones for sure (except maybe the GA props). That's my advice too -- as you'll have seen in each of my replies.

Regards

Pete

[selkan]

Thanks Pete, all very helpful stuff.

Regards, Steven