The flight model

First of all Happy New Year to everybody. I hope you all had a good start into 2020.

I know this is a simulator and it should be flyable for even the most unexperienced user. However, it was often said that the developers put quite some effort into the flight models, that is why they do not bring a model of an aircraft which is still doing its certification flights or where the test flight data are not available. That said, there is something that I would like to ask the developers to have a look over it. When IF is developing the flight models it is often mentioned that the aircraft is being test flown by some of the staff or users. I am not aware of on how you test the flight characteristics but obviously there are a few points where I personally (I just can talk for myself) would like to ask IF for a more accurate simulation. I am not sure if this is a feature request or a general question. The flight model needs more accuracy when it comes to this point:

The take off without flaps/ slats extended or with a wrong flap setting.

I would like to show you just one example, I took the A350 as it is the newest addition to IF.
Aircraft: A350-900
Airport: SBGR
Airport Elevation: 2,465’ above MSL
Temperature: 30 deg C
Dew Point: 20 deg C
Alt. Setting: 1,013 hPa
Density Altitude: 5045’
Absolute pressure: 926.16 hPa
Relative Density: 86.05%
Wind: Calm
Flap setting: 0
Aircraft weight: 279,753 kgs (47 kgs below MTOW)

As you can see in the pictures below, N1 was set to 93%, Vlof (did not use Vmu) was then 145-147 kts, a positive climb rate of 1865 ft/min while accelerating to around 165 kts could be achieved. Normally we would have been crashed already. But as we are still flying I tried out the worst and banked the aircraft right by 20 degrees and selected gear up. This config change in addition to the bank angle would have caused the right wing to stall immediately. This would have led to a total loss of control.

I think even the most unexperienced user knows that especially heavy aircraft like an fully loaded A350 can not take off without at least the leading edge devices extended. I think here the accuracy of the flight model for this critical phase of every flight needs to be refined.

Everyone who wants to become a pilot should learn from the beginning that taking off with a wrong take off configuration in most cases will have fatal consequences.

And just a note: I was able to take off with every model without selecting flaps.

I don’t understand this post. Is it a feature? If so maybe you could be s tiny bit more concise and drop the backstory.

He is clearly asking for a more accurate flight model… the whole point of the IFC is to READ the posts.


I think the staff or Mods already explained that they haven’t got all accurate data from the A350. But I’m still satisfied with the product. Besides it’s the first version, we haven’t got the cabin view 😁


It’s not a glitch though. Its just how the aircraft physics is simulated. This is a feature request for a reworked and more accurate physics model.

This is something that I fully support. The F-22 which I fly 99% of the time can behave somewhat strangely at times. I would vote but I’m in the position of being an ex Regular with more votes than I technically deserve.


Alright, makes sense now

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I am not sure where to put this. I am not sure on how IF is testing the models. But as i tried to explain, at least, on most models that have lift devices, a take off without slats/ flaps extended should not be possible. I am aware that some passenger aircraft do not have or do not need either flaps or slats extended but non of these aircraft exist in IF.


I completely agree.

However, the main argument I have seen against more accurate flight models/characteristics is that Infinite Flight is a game, and therefore should cater to younger audiences who may not know how to properly control an aircraft.

I believe that logic simply doesn’t work. The fact that I can hop in a 757 and do almost 6,000 feet per minute at regular takeoff thrust and still be maintaining/gaining speed doesn’t make sense. I get that it’s not a true simulator in respects to others (not sure if I’m allowed to mention names), but that doesn’t excuse it necessarily. Oh, and I understand the 757 is outdated. It needs a rework. But odd characteristics are also evident across the board. There are definitely more accurate flight characteristics than others, but it’s a real pain to have to climb at such a high V/S so my plane doesn’t rocket to 250 kts+ under FL100. Sure, I can decrease my thrust significantly but the difference between FLEX thrust and climb thrust is only a few N1% percentages. So again, not too realistic.

Lastly, (I know, bit of a long reply) the A350 was a highly anticipated aircraft that was in development for what I can assume close to a year. Overall the lack of proper flight characteristics really is a downside.


Of course, many older planes have incorrect physics.

However, the new planes are developed and tested so the physics are perfect (or as close as it gets).

For example, this real-world B747, C-130 and A35K pilot has said that IF simulates physics close to perfectly.


Or does it? The 757 is vastly overpowered. It’s also an older model that needs adjusting but perf/weight were right back then.


The F-22 and other fighters are special beasts to program in IF. Who knows how they even fly for real, without the computers controlling all the inputs? I had to approximate things based on videos because we’re not going to find much flight manuals for fighters with detailed flight model characteristics.


The flight model is in constant evolution, it’s something we’ve been communicating for a long time. We put focus on “normal” flight configurations because often times, there’s very little data on abnormal situations like a no flaps takeoff at this high density altitude and MTOW.
Would the A350 even let you take off this weight, not flaps 2, at a density alt of 5000+ ft?

I don’t know… if anyone has data though on how a 350 behaves at MTOW, density alt of 5000ft, slats only takeoff (and whatever kind of warning messages the A350 will be flashing as well), feel free to send it my way :)
I’ve spend a bit of time adjusting the stall speeds according to what I’ve found in the data I was given.

In order to accomplish this, I would need:

  • Stall speed at 5000ft or Sea Level at ISA+15 in clean config at MTOW
  • Attitude achieved before the stall
  • N1 required to stay just above stall speed

And when I mean data, I mean hard facts from test flight, FCOM, actual pilot testimony, not “it feels like it should behave this way” or “it doesn’t feel right”, because if I change the flight model of a plane to accommodate for this, I’m sure in a few weeks, someone else will comment that it’s not behaving how they think it should feel.

One that comes out often is how an airliner shouldn’t be able to do a roll. That’s until people get reminded that in the 60’s or 70’s, a 707 was rolled during a demo flight :)

We’re always trying to strike balance between realism and accuracy. Our focus has always mostly been on normal range of flight because that’s what documented and verifiable. I’m always happy to be proven wrong on the flight model, but only with cold hard facts :)


Yes, I’m not disputing that fact. I said it needs a rework. The 757 itself may have a good climb rate in real life but I don’t think it’s as great as Infinite Flight.

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It’s the fact that you can push the 757 engines in Infinite flight up to 119% N1, but when thrust us kept below 105% N1, it flies slightly more conventionally.

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MaxSez: I’m not an aeronautical engineer nor am I qualified to jot here about IF flight modeling. @Lufthansa061 has the tickets, real time experience, education and RT Big Fat Trash Haulers hours to add a significant amount of credibility to his Feature. I view his observations as food for thought for the Developers, not an invitation too the great unwashed to ruminate. @Laura comment smooths the edges & provides expert feedback on the complexity of there task. As you are all aware aircraft manufacturers routinely choose not to publish proprietary material until an airframe has had a shakedown and sufficient data collection to unseal the production archive.
Bottom line. Like Lufthansa I never seen or heard about an Airliner launch w/o Flaps and in some cases slates except in an accident report. IF has an AOK flight envelope for me at present. I expect perfection one step at a time. This Topic Get My Vote, it just sets the stage for our future.
G’Day, MaxSends


Ooh and if we could get a realistic yaw effect from the rudder it would be absolutely fantastic

I agree with you @Noam_Bechhofer. Physics in the sim could be worked on more.

I love the physics just fine actually. I can’t find much (if anything) wrong with them.

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Neither can I. The C172 feels perfect, and I know some real-world pilots and have flown right-seat on GA

I understand that, and it’s mostly fine. There’s just certain things it should be able to do that it won’t. I completely understand that it’s effectively impossible to get accurate real world data for the F-22 (maybe start an espionage division).

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