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I have been having some pretty major issues with take-off performance ever since I switched from FSX Aerosoft A320 to P3D v4.5 Aerosoft A320 Pro (about 3 months now). The problem in a nutshell seems to be the thrust performance during take-off roll and initial climb. The problems seem to have subsided a bit now ever since I moved from using the onboard load planner to the A3XX Fuel Planner app, but this is not the whole story I think.

 

When first moving to P3D and A320 Pro I followed all steps and used onboard planner.  Frequently I would get A-prot and even stall on departure. Sometimes this would involve noticeable decel/accel during the roll. Even moving to TOGA would not save the take-off.  Now I only use the Fuel Planner app and I don't have the A-prot or stall problem but the take-off roll is much much longer than I ever had in previous A320s, or the rolls I see on Youtube videos of the FSLabs A320, or real life, or A320 proper sims that I have flown a few times many years ago.  I use almost all the runway at EGLL and LFPG for example (derated to 67 degrees but still I don't think the roll should be so long).

 

Can I ask for some help on what data/tests/logging I should collect to share with this group to help me work out the problem?  Could it be something to do with having the FSX version and not properly uninstalling it, maybe some old data files affecting the thrust performance or making the aircraft think it is heavier?

 

Thanks in advance.

 

 

 

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Couple of things.

 

Our Fuel Planner does not take into account many different things, so I strongly advise you to use Simbrief.  I created a Simbrief profile for the A330 and I'm running late on doing the same thing for our smaller buses by I think I can get those done by Friday of this week (they've been on my list to do for some time).  Still, the basic Simbrief profile isn't bad.

 

You can read more about this in the following thread, which I recommend you monitor for updates:

 

 

 

Something else.  If you have both the A318/A319 and the A320/A321 then what you actually have is 7 different aircraft, each with it's own different performance.  If you only have the A320/A321 then you have 4 different aircraft.  This is due to having two entirely different types of engines, the CFM engines and the IAE engines.  Just as in real life, the CFM engines spool up faster while the IAE engines take quite a bit longer.  This may account for what you are experiencing, or it could be a load issue - too difficult to say.  What I can tell  you is that I don't have any issues whatsoever and the takeoff rolls seem just fine to me and our real world Airbus pilots on the test team. 

 

37 minutes ago, BAW242 said:

Can I ask for some help on what data/tests/logging I should collect to share with this group to help me work out the problem?

 

This would be an abject lesson in engineering, and while that's not something that we really cover with customers,  you can do this:

 

Pick an airport with long runway (as close to 10,000ft as possible), use the A320 with CFM engines (and later do the same thing with the A320 IAE engines), load 120 PAX, 2K Cargo, and whatever fuel you wish (just ensure it's the same with both engine types), record your calculated V-Speeds and ALL the information from the AS Fuel Planner, then start the aircraft at the runway in the same position for both flights, and then note exactly where on the runway VR is called/calculated and also where the aircraft lifted off when you applied back pressure on the stick.  The field the distance between where the Aircraft started from and where VR was called an where the aircraft lifted off.  Making a video would be VERY helpful.   The compare this to the performance data for the actual aircraft (can usually be found via an Internet search).  Warning, some math will be involved, but math is FUN!

 

37 minutes ago, BAW242 said:

Could it be something to do with having the FSX version and not properly uninstalling it, maybe some old data files affecting the thrust performance or making the aircraft think it is heavier?

 

 

I understand your thinking, however given the many differences this is not possible.

 

 

 

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Thanks Dave I will do that and take a couple of videos.

 

I do use Simbrief (a bespoke AS A320 series set of profiles would be awesome), and also have been putting numbers into this >> A320 Take-Off Performance Calculator website to cross check, and the v-speeds are broadly in line between the website and AS A320. It seems to be more about acceleration/thrust to get to the speeds. I forgot to add in my original post that initial climb performance also seems poorer than I remember in all previous A320 models,  often very slow to get away from the ground, then under 1000 fpm intially, usually leveling out for a while after AA to accelerate whereas I remember previous models used to continue to climb through the accel (maybe this is just a better model now and my technique is poor!). There is no problem after intial climb, or any other phase of flight, just take-off/initial climb.

 

 

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OK, interesting tests, I don't normally use the CFM versions at all, and noticed better accel performance from that one vs IAE, more like what I was used to on previous models, off the ground in much shorter distance (2,700' less), but didn't seem to want to unstick at V2 (took +9 kts).

The IAE continued to feel a bit sluggish and took longer to get airborne, but did so at lower (correct computed) speed and climbed slower.

I started both from LFPG 08L full length.

 

I will Google perf data to check what it should be roughly (and dust off my 1990s aeronautical engineering degree lecture notes to try and remember the maths!)

 

David

 

CFM 

ZFW/ZFWCG 56.1/35.1

Vs 139/146/147

Take off roll to unstick took 40 seconds, unstick seemed to be at 156kts (took these times from Flight Analysis chart in P3D and may not be 100% accurate as I was just scrolling the analysis chart looking for time and speed that altitude started to rise).

Unstick seemed to be just around W4 (4787' from THR) rapid exit maybe 1/3 between that and W5 (6903')  so maybe total roll 5300' if we take 200' off as I started on the piano keys?

 

IAE

Same weights/CG/speeds

ZFW/ZFWCG 56.1/35.1

Vs 139/146/147

Roll took 57 seconds and unstick speed 148kts

Unstick seemed to be about 2/3 way between W5 (6903') and W6 (8743') intersections so let's say 8200' or 8000' if we take off 200' for piano keys?)

 

 

Prepar3D Screenshot 2020.06.03 - 11.39.22.41.png

Prepar3D Screenshot 2020.06.03 - 12.03.14.03.png

Desktop Screenshot 2020.06.03 - 11.27.03.21.png

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Excellent work!   When I have time, it's what I love to do (seriously)!!!  I went crazy with the Dash 8 Q400 Turbo Prop spool times and thrust v speed stuff back in the day (and it's a 2-stage turbo prop with calculations and displayed data to match).  Anyway... seems like another lifetime ago.

 

Looking your data over, I agree with you that everything looks to be within expectations.  Also, the way that the IAE engines work (compare the CFM/IAE engine displays in the aircraft sometime) make them seem more sluggish compared to the CFMs, though I'm sure you know that's not what is actually happening.  Still I believe them modeled correctly.

 

Speaking generally (and not about you), there is more than a tendency for flight simmers to expect faster aircraft / engine performance, and well, all sorts of other things, and developers often get worn out and worn down answering questions and having customers demand changes when their product experience didn't match their other flight sim experience and/or expectations.  So, and don't shoot the messenger here, developers have learned to make things less realistic for this reason.  We did not do this with our Airbus engine performance, we used the real life engine performance tables and for me I think they are very close to being correct, for a flight simulator that is.

 

Love to have you come over the talk with me sometime.  If  you have time and would like to, feel free to catch me on our Discord Server where we have some great Connected Flight Deck/Shared Cockpit and group flights, not to mention some awesome conversations and even instructor lead classes!  See HERE for more information.

 

Best wishes!

 

Dave

 

 

 

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Thanks Dave I will look up your ‘discord’ (as an aside, things have changed a fair bit since I left simming/vatsim 10 years ago, I now find myself accidentally featuring on ‘twitch’ videos from other online pilots!).

 

re. The IAE vs CFM I knew they would be different but I am still amazed that the roll would be 2700’ and 17 seconds longer for same airframe / config / weights / speeds. I will see if I can do more digging (may take the lazy option and contact a couple of old buddies I know who were flight performance and powerplant engineers for an IAE operator and RR!).

 

dave 

 

 

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4 hours ago, BAW242 said:

Thanks Dave I will look up your ‘discord’ (as an aside, things have changed a fair bit since I left simming/vatsim 10 years ago, I now find myself accidentally featuring on ‘twitch’ videos from other online pilots!).

 

re. The IAE vs CFM I knew they would be different but I am still amazed that the roll would be 2700’ and 17 seconds longer for same airframe / config / weights / speeds. I will see if I can do more digging (may take the lazy option and contact a couple of old buddies I know who were flight performance and powerplant engineers for an IAE operator and RR!).

 

dave 

 

 

 

It's not only how different the engines are, it's also how the systems are programmed... the IAE's are more fuel efficent and overall a bit quieter on the takeoff roll because they purposely take more runway to bring the aircraft up to speed.  Given this, it's not suprising that the IAE consumed more available runway.   Remember, the Airbus FMGS takes into account runway length in calculating takeoff performance, you so you can test this by using the same load out and flying off a runway with a shorter lenth or doing an Intersection departure but remember to remove the distance behind you (the difference in runway length) in the MCDU.

 

Looking forward to speaking with you!

 

 

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Same here. IRL as passenger, i timed some trips with both versions of Airbus A320 from Vueling at  take-off roll and the difference was less than 2 sec (same routes ). In fact if you look at the speed trend from both models, you´ll have the explanation. 

 

Best.

 

Miquel.

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15 minutes ago, miquelpp said:

Same here. IRL as passenger, i timed some trips with both versions of Airbus A320 from Vueling at  take-off roll and the difference was less than 2 sec (same routes ). In fact if you look at the speed trend from both models, you´ll have the explanation. 

 

Best.

 

Miquel.

 

Yes, but please remember that as a PAX, you have no idea how the flight was programmed and often you don't know if it's an intersection or full length departure.  Too many variables for a PAX to be able to tell.

 

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Maybe you are right, but i fly 6-7 times a month  to Palma, Madrid and Málaga  from Barcelona. Flight was usually full, 3 versions IAE, CFM and NEO. Not big differences . i takes about 40 sec to take-off to sall models.  

Hi, show you a video from my mobile. This is the A320 IAE...this footage is mine.

 

Best

 

https://photos.app.goo.gl/zat5mbSH6ca1BWCW6

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41 minutes ago, miquelpp said:

Maybe you are right, but i fly 6-7 times a month  to Palma, Madrid and Málaga  from Barcelona. Flight was usually full, 3 versions IAE, CFM and NEO. Not big differences . i takes about 40 sec to take-off to sall models.  

Hi, show you a video from my mobile. This is the A320 IAE...this footage is mine.

 

Best

 

https://photos.app.goo.gl/zat5mbSH6ca1BWCW6

 

No need my friend, I understand.

 

Thanks for the input!

 

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