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Post by bluestar on Dec 20, 2007 15:16:24 GMT
Dan, NP. Once again today. FL340 steady on..... no problems. Mind you I have real weather set, and it updates every 15 minutes, and we all know how "good" the FS weather engine is.... at the same time I've ticked "Download winds a loft" These changes in winds forces the trim-wheel/AP to work heavily sometimes, but it always recovers. Not quick as a F16, but nice and slow like......a....... well..... like a B707! ;-) I am currently traveling on business and should be back home this evening. I will send you the info you requested. Most likely I have done something wrong, but I've been flying HJG for a long time and this is the first problem I've had with the flight model. One thing that might be causing a problem is ASX, although I'm not sure how. The funny thing about the altitude hold is that it will move very slowly back to the assigned altitude and then just prior to reaching it, the rate of change goes from less than 100 fpm to almost 1000 fpm. Like I say I've probably done something. Thanks for the help. Bill
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Post by bluestar on Dec 27, 2007 22:54:06 GMT
Dan,
Did you get the files I sent to you?
Bill
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Post by aerofoto - HJG Admin on Dec 28, 2007 2:48:34 GMT
Bill .... I think you'll find Dan's on Christmas/New Year leave at the moment.
Could be a week or so before he's able to get back to you properly.
You're in good hands there .... but .... please bear with us OK.
Mark C AKL/NZ
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Post by Tarasdad on Dec 30, 2007 7:13:19 GMT
I can confirm the porpoising issue. You have to be VERY exact in turning on altitude hold. Seemed to work best for me when I approached my cruise altitude at 100 FPM in a descent (go above your planned altitude by 40 feet or so), then selecting 0 FPM at 10 feet above altitude. The resultant drift to 0 would put me exactly on altitude, then I could set the ALT HOLD switch without any fluctuation. Note that the needle on the altimeter seems to "snap" to an exact altitude (in 1000s of feet), and that is the point at which it will hold altitude without surging.
Finicky to do, but possible.
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Post by aerofoto - HJG Admin on Dec 30, 2007 8:22:33 GMT
If I'm understanding "TARASDAD" correctly .... this observation is pretty much in line with my own .... as discussed per one of my original posting much earlier in this thread.
So long as one is " VERY PRECISE" with altitude captures .... capturing altitudes in increments of thousands or hundreds of feet results in perfectly smooth/stable flight.
I narrowed any tendancy for porpoising down to "imprecise" altitude captures .... overunning altitudes by increments of tens of feet or less may result in prescisely what "BLUESTAR" first described.
Dan will likely take a look at "BLUESTAR's" files when he return from leave .... to be double sure there's not potential for other factors to come into play here !
Mark C AKL/NZ
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Post by bluestar on Jan 2, 2008 20:30:57 GMT
Mark,
I took the B707 to FL240 using the autopilot. I stopped the aircraft at FL240 and the VSI was at zero for several seconds before turning on the ALT HLD. After about ten seconds the porpoising started. I'm just about out of ideas.
Bill
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Post by aerofoto - HJG Admin on Jan 2, 2008 20:58:27 GMT
So am I too Bill .... and I do mean that in all due respect of course
I most certainly acknowledge you seem to have a performance issue there, but, what troubles be regarding this is I'm just "NOT" experiencing what you seem to be experiencing .... except under the circumstances described and which I know to avoid.
Dan got back only yesterday .... so .... I going to leave you in his good hands with regard to those files you sent him and hopefully we'll be abl to get to the bottom of all this in due course.
Mark C AKL/NZ
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Post by Dan K. Hansen on Jan 2, 2008 22:06:19 GMT
I will most surely get back to you Bill a.s.a.p. I might already have some suggestions for you based on those files you sent me... maybe also some extra info needed. I'll get back to you via PM unless there is something of interest to Joe Public, there's no reason to pollute the forum with chit-chats as we go.... is that reasonable to you too? If you have access to MSN we might even get the chance to have an online communication while we try to fix your problem. Must find a time that is convenient for us both though.... I'm from Denmark, not sure where in the world you are...
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Post by muletrain on Jan 26, 2008 17:09:30 GMT
I am now able to fly the 320C without this odd porpoise after level-off and setting the AP as described by bluestar. As Mark and Tarasdad state, the altitude capture needs to be precise and with gradual reduction in VSI. I do not engage altitude hold; the aircraft stays level and porpoising does not begin. Don't know if there is any effect (good or bad) but I also imported "vertical_speed_time_constant=999" into the [pitot static system] section of the aircraft.cfg. Since there is no porpoising now and altitude hold is good, I'm happy and done messing about...:-)
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Post by Dan K. Hansen on Jan 27, 2008 23:01:51 GMT
I didn't know you had the same problems Roy, but I'm happy that you don't see them anymore. Personally I haven't seen them at all, and I haven't changed anything in the cfg-file either.
Whether or not your edit has any influence on the problem I'll let the expert to comment.
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Post by bluestar on May 22, 2008 1:02:54 GMT
Dan,
My apologies for not getting back to you sooner about this problem. The only way I was able to cure the porpoises was to use the default FSX B737-800 panel. To get the -800 panel to work with the B707. I took the -800 panel aircraft.cfg file and changed the B707 aircraft.cfg file to match where the autopilot was concerned. I adjusted the fuel flow scalar to where the B707 has the correct range at FL350 and M0.82 while flying at MGW. I also changed the loading from a passenger configuration to a freighter configuration.
This is not an ideal fix for me because I really think George has done an excellent job with his panels.
Bill
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Post by aerofoto - HJG Admin on May 22, 2008 13:27:12 GMT
"BLUESTAR" .... I've just sent you a PM Mark C BOG/CO
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Post by bluestar on May 22, 2008 17:58:55 GMT
Mark,
One of the things I do when flying is try to land with only 30 minutes of fuel. When it is a short flight, the takeoff weight will be well below MGW. Since the FDE is designed at MGW, it is possible my problem may be related to the weights that I use.
Bill
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Post by aerofoto - HJG Admin on May 22, 2008 19:08:47 GMT
YEAH .... it's an interesting point Bill .... which is why I raised it with you privately.
I'm also curious to know what (if anything) on some PC systems might affect the trim setting (such as a crook controll device setting/callibration) .... causing constant but subtle movements .... which might then result in continuous oscillation as the AP constantly endeavours to establish level cruise/flight.
Another thing I'm curious regarding too is whether or not the constant oscillation you've been experiencing is only happening above FL270 (that tends to be a magical FS altitude beyond which strange things can start happening) .... or .... is it ocurring at any FL regardless.
Mark C BOG/CO
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Post by bluestar on May 23, 2008 15:32:37 GMT
Mark,
I tried different weights and altitudes and the plane continues to porpoise. It is not a problem with the FDE because it flys fine with the FSX panel or by hand. It almost has to be a logic problem in the autopilot coding.
An example would be the aircraft would be 80 feet off the preset altitude. The aircraft would slowly drift toward the preset altitude at less than 200 fpm and with very little trim movement. When the altimeter gets to within 20 feet of the preset altitude the trim will move and the rate of change increases to more 500 fpm going past the preset altitude by 80 feet. The trim goes in the wrong direction. If in a descent the trim will move down instead of up to stop the descent.
I do not use FSUIPC, use a Saitek X52 joystick and throttle, FSX SP1 with all setting set to default. There are no problems in FS4.
I'm a Boeing guy, but I may download the DC-8 to see if it is a problem.
Bill
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