Any thoughts on this FM behaviour?

[BitMaster]

To answer your actual question, you have partially answered it yourself. It is the drag force the wing needs to overcome once in motion. The faster you role the more air resistance your induce exponentially, mixed with a dozen of other aerodynamic effects that hinder the change of position of the airframe in the air stream it is moving in. Anything in motion wants to stay exactly that way, change any axis movement and you will encounter a certain resistance, defined by mass and force vector inherited and applied. Also the airstream around the airframe is ultra complex and constantly changing while it is moving around its axis rolling there is a constant force that tries to stop the airframe from moving. Centre aileron and it will almost instantly stop rolling, do that with your Roller Skaters and you know how much force that airstream applies to the AC while stopping it from rolling around. You have to constantly fight this force when rolling, and the faster you role you add self induced drag through rolling around so that you quickly have applied all aileron force you have and may achieve only 270°/sec whereas Extra 300s and Edge 540s can almost role twice as fast, less mass and less wingspan...

 

It is like how fast can you run ?

 

With or without my Rucksack ? AT Sea Level or in Nepal ? Bare foot or Nike ? Hungry and exhausted or well slept before ? there is no real simple answer as there are many many factors involved the change the outcome.

[Kurfürst]

Thanks for the quick aero lesson BitMaster! :)

[Yo-Yo]

Thanks YoYo!

 

Out of curiousity, what defines max roll rate? I understand what assists it, but what gives the limit, i.e. what stops the airplane from rolling even faster when it reaches to max rolling angular speed? Air resistance of wings themselves that is from the wings moving perpendicular to the rolling plane, or some lift equilibrium (since roll is from changed lift, negative and positive of the two wings from aileron displacement as I understan) I cannot seem to figure out...

 

You are right. Initially ailerons create increased and decreased lift at corresponding wingtips (I mean the parts of the wings that have ailerons). THen the plane begins to roll, and wingtips go up and down. The additional velocity (up and down) vector added to the plane own velocity (draw the vector triangle) changes AoA of wingtips, so the AoA of the rising wingtip decreases and vica versa. So, rolling angular velocity begins to diminish AoA increment/decrement caused with ailerons. When both differencies are equal to zero - it's the maximal rolling velocity.

 

Additionally, there is the second factor - AoS acting for or against roll - so, the instant roll rate can accelerate or decelerate during the full 360 degrees roll. THat's why some reports operate MAXIMAL INSTANT ROLL RATE instead of 360/time_of_roll.

[leafer]

I am trying to stay chill... but all these "must" , 'too big" begin to be annoying... we use ACCURATE data for this drag - sometimes from WT tests, sometimes from indirect tests, like MP for the P-51 at full flaps and gear down configuration at certain sink rate or in level flight for the certain mass, etc.

 

And please, do not compare DCS to another sims as reference - if you drive me angry I will begin to show sooo great flaws in these models, though it is not very polite.

 

I never thought I'd see the day Yo-Yo said "chill". :D

[Kwiatek]

I have some additions: power-to-weight has not so much sense in looping because gliders have it = 0 and perform loops easily. THe main trap while looping is to avoid two limits - max speed and max g-load - completing a loop. If you pull regarding relatively low g-limit, the speed can overcome its limit.

 

 

Yep but even glider which have power to weight= 0 ratio need required speed to make correct loop ( i know a little about these casue i fly gliders and aerobatics too :) ). So if glider need e.x. 180 kph to make a loop you dont do it with e.x. 120 kph casue you will stall on the top.

 

In our cases ( videos from BOS or DCS) with such low speed after take off and also some drag ( gears, flaps) i think power to weight ratio is quite important. It decide if plane with such low initial speed would be able to do loop or no :)

[iFoxRomeo]

Keep it rollin´

 

[Solty]

 

[Yo-Yo]

Yep but even glider which have power to weight= 0 ratio need required speed to make correct loop ( i know a little about these casue i fly gliders and aerobatics too :) ). So if glider need e.x. 180 kph to make a loop you dont do it with e.x. 120 kph casue you will stall on the top.

 

In our cases ( videos from BOS or DCS) with such low speed after take off and also some drag ( gears, flaps) i think power to weight ratio is quite important. It decide if plane with such low initial speed would be able to do loop or no :)

 

Absolutely right for this case.

[bongodriver]

Keep it rollin´

 

 

 

Truly a magnificent sight to behold, very significant event which the pilot basically exploited the simple trade off of speed and altitude to pull a 1g manoeuvre that all aircraft can technically do (it only becomes critical if you make a mess of it)

 

But of course on certain forums this is not such a significant feat, a low level full aerobatic routine from take off in a He111 performed by any amateur sim pilot is a matter of routine.

[Kwiatek]

Expecially if He-111 could do a near straight roll ( repat level flight roll) right after take off :P

 

I think He-111 IRL probably could make barrel roll ( like in video with Beoing 707) but could not stand a normal roll ( in level flight) even at higher speeds.

Edited October 29, 2014 by Kwiatek

[Demon_]

If the DCS aircrafts don't have a satisfying flight model and so... Who is better?

Edited October 29, 2014 by Demon_

[bongodriver]

No sim is perfect, but DCS is the better.

[KRI3G]

No sim is perfect, but DCS is the better.

 

Agreed. :thumbup:

[airdoc]

Keep it rollin´

 

That's a very interesting video iFR, thanks.

 

Regarding the topic, i think that there are probably many maneuvers that someone can pull in an aircraft in a SIM that seem counter-intuitive, because IRL nobody would attempt them due to the high risk of crashing. No sane mustang pilot (or any warbird pilot) would ever try to perform a loop right after take-off and certainly no He-111 pilot would try a barrel roll at any altitude.

 

The fact that these maneuvers haven't been performed IRL can't be taken as proof that the FM is incorrect.

 

If a 4-engine beast such as a Lancaster can perform a barrel roll in the hands of a seasoned test pilot IRL (Alex Henshaw is the only pilot known to have successfully performed a barrel roll in a Lanc), then i 'd think that most other aircraft would be able to perform this in a SIM (and after a few dozen test crashes).

 

http://www.bcar.org.uk/avro-lancaster

[Solty]

Indeed. This is also the reason why many people try to fly without half of a wing. In war condition that would make 99% of pilots bail. But in simulators people fight to the very end. Especially when server counts crashed planes... Not killed pilots.

[Kwiatek]

I think some dont understand difference between roll and barrel roll.

 

If plane - expecially heavy ( bomber) could do barell roll it doesn't mean that it could do clasical straight roll expecially right after take off.

 

It is a huge difference in reality.

[Yo-Yo]

I think some dont understand difference between roll and barrel roll.

 

If plane - expecially heavy ( bomber) could do barell roll it doesn't mean that it could do clasical straight roll expecially right after take off.

 

It is a huge difference in reality.

 

 

You are right. THere are three main factors that can prevent from this roll: slow roll rate that causes lack of side force and adverse sideslip decelerating roll rate.

[airdoc]

I think some dont understand difference between roll and barrel roll.

 

If plane - expecially heavy ( bomber) could do barell roll it doesn't mean that it could do clasical straight roll expecially right after take off.

 

It is a huge difference in reality.

 

 

Actually, as counter-intuitive as it sounds, the Lancaster could also perform a slow roll, since you 're pointing out the difference with the barrel roll.

 

Check this pilot's account from 3:10 onwards :

 

(I think that the pilot in the video is referring to Henshaw again, who has done various rolls and other prohibited maneuvers in a Lanc)

 

I think that you are missing my point though.

All I 'm saying is that comparing maneuvers performed in a SIM to RL maneuvers that have never been performed due to the high risk should not be used as an argument that the sim FM is wrong.

Edited October 30, 2014 by airdoc

[Yo-Yo]

Both maneuvers require a lot of space in height to be successful.

[bongodriver]

All I 'm saying is that comparing maneuvers performed in a SIM to RL maneuvers that have never been performed due to the high risk should not be used as an argument that the sim FM is wrong.

 

when the sim's FM is demonstrating the ability to routinely do such things that in reality are avoided because of likely death then yes it does demonstrate an FM is wrong.

[Luzifer]

when the sim's FM is demonstrating the ability to routinely do such things that in reality are avoided because of likely death then yes it does demonstrate an FM is wrong.

 

Things like jumping in a high performance tail-dragger fighter without previous piloting experience? How does that make the FM wrong? I mean, what you're saying boils down to "crashing a plane in a flight simulator doesn't kill the player in real life, therefore the FM is wrong".

[bongodriver]

Things like jumping in a high performance tail-dragger fighter without previous piloting experience? How does that make the FM wrong? I mean, what you're saying boils down to "crashing a plane in a flight simulator doesn't kill the player in real life, therefore the FM is wrong".

 

Maybe in your world it means that, but what I am actually saying is that if the sim in question is making a low level full aerobatic routine in a medium bomber so easy that an internet pilot can do it any time they like yet real world test pilots wouldn't attempt it because the odds are almost certain death then the FM is wrong.

[Solty]

What bomber. Weren't we talking about Dcs 51 and 190.

[bongodriver]

There has been a He-111 contamination.

[NineLine]

Maybe in your world it means that, but what I am actually saying is that if the sim in question is making a low level full aerobatic routine in a medium bomber so easy that an internet pilot can do it any time they like yet real world test pilots wouldn't attempt it because the odds are almost certain death then the FM is wrong.

 

Maybe, might be other factors like the Damage model not being correct, or other things. Also because a manoeuvre is deemed too dangerous to do, doesn't mean it will result in pilot death every time a pilot would attempt it. But unnecessary risk could result it death and loss of the aircraft so its not recommended.

Edited October 30, 2014 by NineLine