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Shmiffy

[MD11X] - AT / AP Logic

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Hi Guys:Given that the threads here descend faster than the MD11 climbs, i hesitate slightly before posting this, but who knows, maybe a response will ensue ;)Having gotten myself a fair few hours in now with the MD11 on Vatsim with ASX running, and mostly transatlantic i have noticed what seem to me to be oddities in the way that the AutoThrottle logic is applied. It could well be that the aircraft is a bit odd in its behaviour in real life, but i suspect that the situation i find myself in is strictly FS Related. As we all know, the Atlantic Winds in FSX, despite HiFi Sims best efforts are a touch...erm... 'unique'. This is mostly due to the FSX weather logic, and the limited reporting stations, coupled with ASX attempting to smooth the winds, and FSX attempting to do the same in the opposite direction.Nonetheless, This issue occasionally occurs during overland flight, and is a tad annoying.It seems to me that when a wind shift occurs, the resulting loss of thrust confuses the pants off of the Autopilot / Autothrottle. While in the real world the AP/AT wouldn't necessarily have to deal with these issues unless some serious windshear occured. In the FS world, this has become a regular occurrence for many users, and often is a cause for some potentially major altitude deviations. Within online flight, this can be somewhat problematic.The solution that the autopilot/autothrottle commands to a serious windshift seems to be that the AP commands the Altitude to remain level, lets assume FL350. Meanwhile, the AutoThrottle spends some time 'thinking' about the increasing loss of airspeed, as the airspeed starts to drop, the aircraft seems to try and maintain FL350 by pitching up, increasing the speed with which the airspeed decays.Meanwhile the AT has noticed this issue, and the throttles get thrown forwards but the CRZ LIM thrust is not enough to fight against the ever increasing pitch. Eventually the MD equivalent of Alpha Floor kicks in, and the AT Ref in the PFD switches to .830 PITCH or the flashing white THRUST message.At this point, the nose comes back down, and a descent begins to start clawing back the speed. In a busy online environment (cross the pond yesterday for instance) this is not only a problem, but a cause for much screaming from other pilots, controllers and so on. ;) I managed at one point to get from FL370 Yesterday to FL348 BEFORE PEOPLE START FLAMING - there was no traffic below or behind for a long way so i let the situation develop to see where it took me, after having PM'd the controller - Anyway, when the speed is beginning to come back, the nose pitches back up to try and recapture the altitude, but the AT still hasn't really given itself enough overhead to cope with the required airspeed increase and a climb, and so the see-saw cycle continues.Eventually, the aircraft will sort itself out, but i find that i have to intervene and up the EPR limit to GA Thrust via the PERF page.There is a workaround for this situation, and that is basic pilotage. As soon as i see the situation start to develop, i disconnect the AP, AT and start flying manually until the winds sort themselves out. Obviously, in the real world, should a situation like that described above occur, manual flight would likely be the solution, but as we all know, this is a sim, and that situation would be extremely unlikely at FL350 with 300 Pax in the back :)While the reaslism built in is incredible. I was wondering ifA) It is only me that is experiencing this.and :( If it is affecting a lot of people, could this perhaps be considered an FS Bug (albeit not something caused by the MD11 Add On itself) and therefore 'some' of the realism should perhaps be 'dialled back' for want of a better term so that the AP/AT is capable of handling the oddities of FSX Weather?Apologies for the long post, i'm sure you appreciate that that took some explaining, perhaps some thoughts from PMDG and other users.For the record, when entering Transatlantic Cruise Flight i now switch to GA Thrust as a matter of course to ensure that the thrust is available if the AP commands it, but as you can appreciate, thats not really something one would expect to have to do.CheersPaul :)


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You are correct, the FSX wind/temp/pressure shifts are very unrealistic and no realistically modelled simulation is going to replace good piloting techniques in these situation.You didn't mention FSUIPC... ASX doesn't do a good job of solving the problem, it should be used with a registered copy of FSUIPC, which is given the job of taming FSX. I use 1deg/kt per 5 seconds to dampen the shifts and the result is as if there were no problem at all.


Dan Downs KCRP

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Hi Dan:Many thanks for the prompt response. I do use FSUIPC4, but my smoothing is set to about 2 Seconds. I Shall try upping that limit now and see how we do.Thanks againPaul


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Hello Paul,Even though i use FS9 and AS6 that problem is present, i have a registered copy of FSUIPC and i use the "wind smoothing" option enabled and set it to a rate where the wind changes 1 degree or knot every 2 seconds....i must say this helps ALOT and you may consider buying a copy of FSUIPC to help that situation as its only available in registered copies. Below 5000ft however i change it to something more realistic to simulate gusts and wind variations better as 1 degree/knot per 2 seconds is a bit low


Bryan Richards

 

"People depend so much on automation that they forget how to get the automation to work." B.W.

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Hi Bryan;I suspect you started posting at about the same time i added my response. See post above ;)But many thanks for the response.CheersPaul


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Hi Paul:>For the record, when entering Transatlantic Cruise Flight i now switch to GA Thrust as a matter of course


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Guest TSE

PaulThis happened to me as well and I noted the AT system to be rather slow in throttling back up again when in "recovery" mode - I found switching to V/S and manually dialing to V/S +-0 for about 30 seconds helps establishing attitude plus the throttles came back up much faster when in V/S mode, I usually can switch back to PROF mode without any further issues.On another note - I'm seeing a heavy wind direction offset (up to 180 degrees from reported direction) if wind smoothing options are enabled in FSUIPC, if I switch off wind smoothing in FSUIPC, wind direction and speed are 100 % accurate according to the ASV6.5 reports.Anybody else having this issue or am I alone ? Any idea what could cause that ?ThanksJoerg

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>Any idea what>could cause that ?It is simple, there is an obvious tradeoff between wind smoothing and having "locally" accurate winds. Experiment with different smoothing parameters to strike the correct balance. And I would look at the ASV wind reports to see whether they look realistic - wind direction can't change 180 deg in a few minutes of flight time unless you are in the middle of a storm.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg


Michael J.

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