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Post by geoffco on Oct 8, 2010 15:16:11 GMT
Hi,
I have been testing out the new Boeing 717-200 and have encountered an interesting problem. In order to get moving on the ground (and keep rolling thereafter), I seem to need 55-60% N1 which is a bit excessive I think! Perhaps this is normal, I am not a real 717 pilot, but I suggest that it is not... Has anyone else seen this issue?
I have checked that this is not a brakes setting issue and I have repeated it a different airports. This is certainly something in the .air file, because when I try using the .air file from the old JCA model then everything is fine... I am not too confident with editing .air flies but I had a quick look with AirEd and cannot see any obvious difference with the JCA version - and no entries like 'ground drag' or 'rolling resistance' etc... Someone who knows these things can probably suggest what is wrong.
Please advise a solution if there is one.
Thanks,
Geoff
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Post by aerofoto - HJG Admin on Oct 8, 2010 15:42:47 GMT
A similar issue arose with our DC9 series aircraft too .... and has been attributed to "FS GROUND FRICTION" issues .... which affects some aircraft in FS more than others Durinmg our own pre-release testing/experimentation/development of our DC9's .... we found that if we got the ground thrust/taxiing component right then we also ended up with an aircraft that was "MUCH TOO EXCITED" once it got airborne. For this reason we concentrated upon trying to get resonably accurate airborne performance .... possibly at a slight disadvantage to initial ground roll agility. The same possibly applies to our "Super-Modern DC9-30" too  .... i.e. B717-200  One thing I've observed (with the DC9's in this case) is that it does, for the reason stated (FS ground friction issues) require abnormal power to start moving/taxing these aiurcraft .... BUT .... once they start moving at a reasonable ground taxi speed then things aren't too bad. Have a look at the following thread/link on this very same subject .... and which we do acknowledge but can't yet resolve .... tonymadgehjg.proboards.com/index.cgi?board=chat&action=display&thread=2814Mark C AKL/NZ |
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Post by geoffco on Oct 8, 2010 16:27:52 GMT
Thanks for the response...
I understand why you have settled on this compromise, but is there really no middle ground? Some settings where the airborne characteristics are a little more 'eager' but where the taxi power needed to get going is still high, but perhaps less than 50%..? The 55-60% N1 to get rolling and 45-50% to keep going (at 15 kts) just feels too high, considering that a derated TO thrust might only be 85% N1.
Would you be able to tell me the main settings in the .air file that effect this? I have been trying to work it out (by comparing to the JCA file which is conversely too 'eager' on the ground) but not really getting anywhere... would really like to find a compromise between the two air files...
Thanks,
Geoff
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Post by Dan K. Hansen on Oct 8, 2010 18:04:17 GMT
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Post by botamern on Oct 8, 2010 18:57:58 GMT
Using the default 777-300 panel I am holding taxi speed at about 41% N1 and accelerating at about 44%. It does take more than that to overcome the friction from a complete stop, but once moving I rarely show an N1out of the low 40s.
Nick
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Post by aerofoto - HJG Admin on Oct 8, 2010 21:03:19 GMT
I concurr with Nick on this .... because that's pretty much what I'm seeing too with our DC9's and with our current DC9 panel range.
"THAT" being/meaning .... a bit more power than is realistic "IS" required to start moving (to overcome that natural FS ground friction) .... but once moving at a reasonable pace .... then not too much power being required in order to maintain a decent rolling speed
"IF" folk are taxiing very heavy .... then a bit more power again "might" be required.
Mark C
AKL/NZ
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Post by Dan K. Hansen on Oct 8, 2010 21:14:52 GMT
Goeff actually haven't told us which panel he's using .... only that he has apparently tried a different .air file ... (I wonder why that didn't crash, og maybe FSX is more strict in having the right files connected .... another air file than the original, would probably bring FSX to its knee, although I haven't tried it ...)
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Post by geoffco on Oct 8, 2010 22:00:39 GMT
Goeff actually haven't told us which panel he's using .... only that he has apparently tried a different .air file ... (I wonder why that didn't crash, og maybe FSX is more strict in having the right files connected .... another air file than the original, would probably bring FSX to its knee, although I haven't tried it ...) I'm using a heavily modified version of the VANS Aircraft Company's panel, as I believe it to be the most realistic 717 panel currently available... The N1 should, however, not be a function of the panel however since it is read directly as an output variable from FS9 (it certainly in in this panel as I have reworked some XML code in the same gauge). The alternative .air file I used was also for a 717 aircraft, in fact it was for Nick's previous one, distributed by JCA. However, as far as I have seen, having the wrong .air file will not crash FS9 (as long as the sim= reference is correct) but it might now fly properly unless it is a closely related aircraft. The comments above regarding the sim1.dll modifications are interesting, and I might have a look at this when I have time after the weekend... I will report any findings. Geoff |
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Post by Dan K. Hansen on Oct 8, 2010 22:39:16 GMT
Thanks, and have a nice weekend.
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Post by geoffco on Oct 12, 2010 10:09:15 GMT
Hi again.
After some digging around, I found a modified sim1.dll to try out, but it had only been modified for skid-friction so it didn't help too much. Next, I actually hecked it a bit myself and reduced the roll-friction on concrete, asphalt and tarmac. I am still not settled on the value I want to stick with but now am able to get the 717 rolling, at MTOW, with a short push at 50% N1 and then hold around 15 kts groundspeed with 30-40% N1 -> Much more satisfying! Happy with this aspect now.
I think I have come accross another problem with the low thrust though... When performing a takeoff, I find that I cannot rotate properly at the correct (real world) Vr speed. I still need to test this though and will report back...
Cheers,
Geoff
EDIT: I am happy to share the hex valuse / offsets I have set in the sim1.dll file if anyone is interested. Once I have finished playing around with them, I will post the final values here.
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Post by Dan K. Hansen on Oct 12, 2010 10:31:52 GMT
Thank you very much for your feed-back here, much appreciated....
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Post by BillA on Oct 12, 2010 13:30:53 GMT
Yes, good find and please keep us informed
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Post by geoffco on Oct 12, 2010 19:12:29 GMT
Hi,
After a couple more takeoffs I definately feel we are underpowered for takeoff. I only had a 46000kg TOW and still my rotate speed was at Vr+15 wrt the published data...
Did any of you see anything like this in the pre-testing? Is it somehow a symptom of my messing with the sim1.dll - I can't see how but I still wonder...
Geoff
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Post by Dan K. Hansen on Oct 12, 2010 20:24:40 GMT
You are taking off against the wind right? |
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Post by geoffco on Oct 12, 2010 20:28:37 GMT
Yes ;D
(and testing with calm conditions also)
Geoff
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.... i.e. B717-200 
