Flight Model is strange now with this new spoiler phenomenon

[rbringh 50]

Since the last update it's been almost impossible for me to maintain a steady approach speed. Speeds just drop from 110 to 80 with no throttle adjustment. You can hear the props change or something. Is this a result of the new spoiler effect to simulate prop drag? Any others find it difficult to maintain an approach speed?

[UnsealedKarma 52]

There are some posts on that in Twin Otter thread on the MSFS forum including some suggested DIY fixes. The easiest one being editing the aircraft.cfg spoiler value from 60 to 30.

 

 

[echo_oscar 40]

Yeah, its pretty much impossible to get below 110kias pitching level without dropping to flight idle, which deploys the invisible spoiler and causes you to sink like a rock. However as soon as you bump up the power lever you can actually exceed max flap extension in even the most shallow descent. Very hard to fly a stable approach by the numbers. 

[scoobyx 27]

11 hours ago, echo_oscar said:

Yeah, its pretty much impossible to get below 110kias pitching level without dropping to flight idle, which deploys the invisible spoiler and causes you to sink like a rock. However as soon as you bump up the power lever you can actually exceed max flap extension in even the most shallow descent. Very hard to fly a stable approach by the numbers. 

 

agreed. this is definitely a step in the wrong direction regardless of the intention. the silence on the boards is deafening too which is starting to make me less hopeful about future improvements.

[Aerosoft Team [Inactive Account] 51562]

I will ask Alexander to comment on this. At this moment I can only say that our resident real pilots did not report this.

[echo_oscar 40]

No offense but your resident real pilots haven’t caught a lot of bugs or weird behaviors at launch or in your patches. And you threatened the one pilot that helpfully made a mod that fixed them.

[Aerosoft Team [Inactive Account] 51562]

7 minutes ago, echo_oscar said:

No offense but your resident real pilots haven’t caught a lot of bugs or weird behaviors at launch or in your patches. And you threatened the one pilot that helpfully made a mod that fixed them.

 

No offence taken, but I did no such thing. I just asked for files that were copyright violation to be removed and offered him to host the sections of the file that he changed so everybody had access and our copyrights would be respected.  

 

As said I have asked Alexander to comment on this.

[UnsealedKarma 52]

As suggested on the MSFS forum you might want to take a look at the 

prop_mod_zero_lift_drag_cf

setting in the engine.cfg as mentioned in the MSFS documentation.

 

[metzgergva 210]

The invisible spoiler was introduced to simulate the immense drag when the prop is set to high RPM on final. It happens only when you fly with very little TQ, below 5-6 depending on the approach speed. Typically with flaps you are above that like TQ 10-12 on final for a 3 degree final drift down angle.

 

It may also happen when you pull idle on approach without flaps and RPM lever in HIGH position, but that is when operation performing a STOL approach and the additional drag from the prop is simulated by deploying the invisible spoiler to match the dive capability.

 

Now does it slows down the aircraft too much? Difficult to say, but our test pilot agreed on it as it is with the current effectiveness.

 

The prop model will see a further improvement with SU9 and I will certainly do a check on it to adjust if necessary. Until then, for those who are not happy, check your approach procedure and keep RPM low until 500 feet above runway and set it to high when flaps are deployed. Or you follow the tipp in the other forum to change the spoiler angle from 60 to 30 or whatever you think suits you.

 

 

 

 

[rbringh 50]

That was the kind of the response I was expecting. I totally understand the intention. I just don't think the penalty in this case fits the crime. I'm not descending with dead unfeathered props. The hit a brick wall speed drop then the sudden and excessive speed increase with minimal throttle adjustments just seems to defy physics. You may want to add a few more variables (like momentum) into that algorithm. Hey, it's your plane, I'm just a dumb customer.

[scoobyx 27]

Adding to that, a patch or two ago additional changes were made which made the plane way more slippery. This requires absolutely maintaining idle throttle for an extended period of time just to bring the plane into safe flap operating range. Again, it just feels like one step forward and two steps back.

 

I had put the plane in my hangar for quite some time and I just took it out again and it really doesn't feel good at lower speeds.

[metzgergva 210]

I just checked slow down from cruise 140 kts to 100 kts level flight. With low RPM and Idle TQ it takes 25 sec.

Maintaining then 100 kts I get 800 fpm descent rate. This is 1.5x the normal glide angle, enough to control glide slope. The virtual spoiler is not active at all during that phase.

Only when you change to high RPM, it will kick in and reduce speed as desired for slowing down further.

I agree it is difficult to maintain 100 with high RPM, but that is not what you should do on a descent.

Approach should be flown in low RPM, de-accelerate by setting flaps 10 and then 20 and fly about 80 kts. Maintain 80 to 500 ft AGL, then switch to high RPM and keep TQ around 20-25 for final approach speed.

 

We plan to give you an update once SU9 is fully tested and availble.

 

 

 

[scoobyx 27]

Thanks, @metzgergva. I'll give that a shot later. Appreciate the detailed explanation.

[rbringh 50]

Thanks for the detailed explanation. The method you recommend is close to what I have been doing. Delaying the RPM increase did help.

Again, Thanks.

[Aerosoft Team [Inactive Account] 51562]

18 hours ago, scoobyx said:

really doesn't feel good at lower speeds

 

Also when flown as Alexander (and real pilots) advise you to do? Or do you have any information that indicates the aircraft should not flown like that?

[UnsealedKarma 52]

9 hours ago, metzgergva said:

Maintain 80 to 500 ft AGL, then switch to high RPM and keep TQ around 20-25 for final approach speed.

Thank you. Seem to align the real POH although 500 ft AGL is set as the minimum for full increase.

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[Aerosoft Team [Inactive Account] 51562]

1 hour ago, UnsealedKarma said:

Thank you. Seem to align the real POH although 500 ft AGL is set as the minimum for full increase.

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Not on my system right now, is this something missing in the manual?

[Transair27 90]

10 hours ago, rbringh said:

Thanks for the detailed explanation. The method you recommend is close to what I have been doing. Delaying the RPM increase did help.

Again, Thanks.

how does this procedure work then in a steep approach such as TFFJ St Barts?

[rbringh 50]

3 minutes ago, Transair27 said:

how does this procedure work then in a steep approach such as TFFJ St Barts?

 

For me ...not really. Fly it everyday with the Otter, Kodiak and Embraer Bandeirante. They all do it but the Otter is the most unpredictable.

[Transair27 90]

3 hours ago, rbringh said:

 

For me ...not really. Fly it everyday with the Otter, Kodiak and Embraer Bandeirante. They all do it but the Otter is the most unpredictable.

yes I have quite a bit of trouble exercising the throttles to maintain 80 kts or so given the steep approach.  Reducing throttle invites the 'spoiler' effect, with poor consequences!

[metzgergva 210]

As said before we are fine-tuning that behaviour for SU9.

 

[scoobyx 27]

17 hours ago, Mathijs Kok said:

 

Also when flown as Alexander (and real pilots) advise you to do? Or do you have any information that indicates the aircraft should not flown like that?

No info or real life experience flying the Twin Otter from me.

 

I got the plane on launch day and it's gone from being easy to control during the approach and landing phases (almost benign) to being quite difficult.

 

Using Alexander's specific values definitely works better but it still feels like there's no room for error. I was pushing the prop levers forward during my descent earlier than 500' agl (which, to be fair, I've been doing since I purchased the plane with great success).

 

Since I don't have real life experience in the plane I'll stop providing feedback on flight performance here. The one thing I'll ask is the next time your team introduces something that dramatically changes the plane's behavior or that's going to require precise settings to keep the plane in the air, please publish those in the patch notes or something. These abrupt changes to the flight model are not fun to deal with. There was zero chance of me figuring out how to mitigate the invisible drag chute without Andrew's input.

[UnsealedKarma 52]

23 hours ago, Mathijs Kok said:

Not on my system right now, is this something missing in the manual?

Hmm. The manual (see screenshot below) does mention full prop increase at 500 ft AGL or IFR minimums. It’s not mentioned specifically, but you could say that it’s implied the part before 500 ft should be at less than full increase.

Btw, the text indicates two different speeds indicated for a 10 deg flaps approach. Comparing to the POH 94 knots is without flaps.

 

As mentioned above, I think you should take a look at the new variables in engine.cfg introduced with the new prop modelling in SU8. Specifically prop_mod_lift_drag_cf and especially prop_mod_zero_lift_drag_cf for beta. I haven’t played with these myself, but they could offer a potentially more elegant solution to the missing prop drag than the on/off invisible spoiler. The default value for prop_mod_zero_lift_drag_cf is 0.01 - a value that seems very close to zero. I wonder if a higher value might give the desired high rpm prop drag effect.

 

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[metzgergva 210]

That‘s what I plan to do. There might be other reasons why the prop does not break enough. We are all learning to understand the new prop model. 

[Aerosoft Team [Inactive Account] 51562]

On 4/21/2022 at 12:01 PM, scoobyx said:

I got the plane on launch day and it's gone from being easy to control during the approach and landing phases (almost benign) to being quite difficult.

 

Mmmmm, but we knew at the start we needed to add less drag for the shape and more for the props.