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 Post subject: Impossible landing
PostPosted: Sun Oct 07, 2018 9:43 pm 
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Joined: Fri Oct 05, 2018 5:35 pm
Posts: 21
Hello,
So I had a bad flight today... :?
Attached are the logs and the flight plan.
Using latest version 3.9.0 I've created a flight plan from KSTL to KMDW (NATCA3 SPI DCT PHEEB ENDEE4) where the last way-point was 38NM away from KMDW (no STAR defined, wanted to be vectored).
I was getting the feeling there was going to be an issue when I was cleared to descend from FL240 when I was only 90NM from KMDW. Eventually I got vectored to the FAF when I am at an altitude of 9,000 feet and at a speed of 280 kts (unable to slow down obviously). I was using the decent rate defined in my 737 preset (-2000 FPM).

Beside this issue I also encountered an issue related to the destination airport weather - tuning to the ATIS prior to TOD I got clear skies in KMDW however the actual weather when arriving was an overcast at 600 ft (which was actually the real weather after verifying online)!! I am using ASP4 as weather engine.

Thanks,


Attachments:
KSTLKMDW_FSX_07Oct18.rar [909 Bytes]
Not downloaded yet
Logs.rar [602.5 KiB]
Downloaded 2 times
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 Post subject: Re: Impossible landing
PostPosted: Mon Oct 08, 2018 10:30 am 
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Joined: Fri Oct 05, 2018 5:35 pm
Posts: 21
Appreciate if someone can initially just let me know if the logs I sent are sufficient? I did not have any debugging options on...but saw some files in the folder got updated during this flight so some logging was indeed working.
Also, please let me know if something in my setup was wrong as I do not want to continue creating flights if they are not handled successfully in the end run.
The only workaround I can think of right now is increasing the descend rate significantly but this would be unrealistic...

Thank you


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 Post subject: Re: Impossible landing
PostPosted: Mon Oct 08, 2018 11:00 am 
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Joined: Sun May 05, 2013 2:22 am
Posts: 476
I took a quick look at the logs. Your flight plan was fine; in fact I flew KSTL-KMDW with exactly this flight plan a few months ago. Your last waypoint (STKNY) is 29 miles out which is fine, and PF3 has 9000 for the altitude at that point which is as expected for about 30 nm out. The only thing I see is that you initially were descending from cruise at about 1400 fpm and later increased your descent rate. I think you probably did not descend fast enough and likely had a tailwind, which increases the rate at which you must descend to hit your crossing altitudes. At MMEGG the altitude on the PF3 waypoint profile page is FL190 and you were at about FL220; at ENDEE the altitude on the waypoint page is 14000 and you were at about FL180. You were still at about 15000 at STKNY. One thing you can do is have the PF3 Display utility running during the flight (pf3_display.exe which is located in your PF3\PF3_Displayer folder). After PF3 is connected, the utility will show the next waypoint and the crossing altitude for the waypoint as listed on your flight plan profile page. If you have a tailwind you will probably need to descend at a steeper rate than planned in order to hit the crossing altitudes. Also, you can change the waypoint altitudes if necessary before the flight (hover your cursor over the waypoint names on the flight plan page and the distances will appear, which will help if you want to make adjustments).

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 Post subject: Re: Impossible landing
PostPosted: Mon Oct 08, 2018 11:01 am 
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Joined: Mon Feb 08, 2016 9:29 pm
Posts: 363
I am away from my PC these days, so cannot look at your logs.

Nevertheless some thoughts:

Regarding ATIS: The sim's weather report which PF3 uses via FSUIPC is only reliable around about 50nm. If you are further away from the destination ATIS will most probably be wrong.
Try to search this forum for more details, it has been explained several times.
So better use the Active Sky weather report.

Regarding your descent:
If you feel ATC does not descend you in time you can always ask for a lower altitude. If necessary do that when you passed your calculated TOD (which PF3 does not know of).
Apart from that I don't see that 24000 ft in 90 nm should be a problem for a 737. The profile setting does not mean that you should keep that descent rate all the time. It's just an average value for internal calculations.
Rather start your descent steeper. You can always decrease your descent rate as appropriate later. The other way round you might run out if distance.

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 Post subject: Re: Impossible landing
PostPosted: Mon Oct 08, 2018 12:02 pm 
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Joined: Fri Oct 05, 2018 5:35 pm
Posts: 21
Quote:
I took a quick look at the logs. Your flight plan was fine; in fact I flew KSTL-KMDW with exactly this flight plan a few months ago. Your last waypoint (STKNY) is 29 miles out which is fine, and PF3 has 9000 for the altitude at that point which is as expected for about 30 nm out. The only thing I see is that you initially were descending from cruise at about 1400 fpm and later increased your descent rate. I think you probably did not descend fast enough and likely had a tailwind, which increases the rate at which you must descend to hit your crossing altitudes. At MMEGG the altitude on the PF3 waypoint profile page is FL190 and you were at about FL220; at ENDEE the altitude on the waypoint page is 14000 and you were at about FL180. You were still at about 15000 at STKNY. One thing you can do is have the PF3 Display utility running during the flight (pf3_display.exe which is located in your PF3\PF3_Displayer folder). After PF3 is connected, the utility will show the next waypoint and the crossing altitude for the waypoint as listed on your flight plan profile page. If you have a tailwind you will probably need to descend at a steeper rate than planned in order to hit the crossing altitudes. Also, you can change the waypoint altitudes if necessary before the flight (hover your cursor over the waypoint names on the flight plan page and the distances will appear, which will help if you want to make adjustments).
Thanks Dan however I am pretty sure I changed the descend rate to -2,000 relatively early after noticing I did not set it correctly. From the logs it makes sense I got a 6,000 feet delta?
Do you have a preset you recommend to use for airliners (737,A320 etc..) which works best with PF3?

Thanks for the explanation
Quote:
I am away from my PC these days, so cannot look at your logs.

Nevertheless some thoughts:

Regarding ATIS: The sim's weather report which PF3 uses via FSUIPC is only reliable around about 50nm. If you are further away from the destination ATIS will most probably be wrong.
Try to search this forum for more details, it has been explained several times.
So better use the Active Sky weather report.

Regarding your descent:
If you feel ATC does not descend you in time you can always ask for a lower altitude. If necessary do that when you passed your calculated TOD (which PF3 does not know of).
Apart from that I don't see that 24000 ft in 90 nm should be a problem for a 737. The profile setting does not mean that you should keep that descent rate all the time. It's just an average value for internal calculations.
Rather start your descent steeper. You can always decrease your descent rate as appropriate later. The other way round you might run out if distance.
Thanks this makes sense! By active sky weather report you mean tuning to Active sky built in ATIS frequency?

Regarding the descend rate - I was actually cleared to descend from FL260 to FL240 right in TOD when I got the automatic simulation pause (btw I note the descend clearance happens exactly on TOD pause every flight) but when leveling off at FL240 there were no further instruction to descend for a significant amount of time which I think was a waste of time due to the steep descend profile required manually afterwards.


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 Post subject: Re: Impossible landing
PostPosted: Mon Oct 08, 2018 12:22 pm 
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Joined: Mon Feb 08, 2016 9:29 pm
Posts: 363
I use the WX-Gauge that comes with Active Sky. The Active Sky ATIS frequency should also work.

Instead of considering the wait for a further descent a waste of time, imagine it is needed for traffic separation. There is some randomization built in so you might get different step descents every flight. See it as a simulation of traffic separation. If you notice you won't get down in time request a lower altitude.

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 Post subject: Re: Impossible landing
PostPosted: Mon Oct 08, 2018 3:11 pm 
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Joined: Tue Dec 24, 2013 1:27 pm
Posts: 930
In addition to above things: If your approach does not work for any reason (even if it is caused by ATC), declare a missed approach / go-around, just like in real-life.

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