Keeping straight on takeoff

  • F-18, it starts to deviate from a straight line, then whatever I do with the rudder pedals tends to overcorrect it, leading to an oscillation. Often results in a crash.


    An F/A-18 would not wobble along length axe. That is not how it is built.
    Diverting the discussion to nose wheel steering functions tends to overwrite this key issue brought up by users.


    Loss of lateral control of aerofly's F/A-18 is based on incorrect (incomplete) modelling. That simple.


    Background: Physics data available to and used by game developers are limited in a way
    assumptions or pretty-flight-modelling gets to the top.


    Steveiy, Lowering pedal sensitivity in the game settings may compensate a bit (all presets are way too nervous),
    but don't hesitate to encourage the dev team to rectify F/A-18 physics over time.


  • Hello Almnudler,


    Your satement is a bit misleading, the physics engine of the Aerofly FS 2 is outstanding, its probably too good and creates (for some users) unexpected behavior but still physically accurate behavior based on the parameters we throw at it. We could have set parameters unfavorably though, but this is not the issue of the physics engine! The physics engine of the Aerofly FS 2 is correct in regards of the laws of physics (actio = reaction, forces, inertia, gyroscopic effects,...)


    The real issue in the F18 lies in the front wheel steering or a combination together with the main gear dampeing. As you can see in your last screenshot the front wheel is pointing towards the runway, I think the link between the front wheel and front gear is just too weak and therefore the front gear is somewhat castering.
    And also if you demand a 45deg deflection by giving full rudder deflection, the result will be quite violent in the real world and in the sim. The fact that the deflections are too high for takeoff and landing have been discussed here before, that, again, is not an issue with the physics engine itself.


    Of course the real F18 can wobble along the x-axis, there is nothing that prevents that physically. There is one sping/damber system on the left gear and one on the right gear, there you have your oscillating system. Give it some side force and the one side will compress more than the other side, remove the side force and the system will swing back to neutral, keep its momentum, swing through to the other side and repeat as many times as you want if the dampening is low.
    Any car, any airplane with two wheels left and right does that and the Aerofly FS 2 modelles that very accuratly in terms of physics. You can't stop it unless you sense the side acceleration and give the damper on the outboard curve side more pressure and as far as I know there very few if any cars that have that, I've not heard of any airplane that does have something like that.


    What we or even you yourself can do is open the .tmd file of the F18 and try to increase the main gear spring stiffness and front gear steering stiffness, that should reduce the amount of the swaying left/right. If you never taxi on the ground you might as well change the servo steering P1 value to 0.0, then the steering will be disabled for now.


    Cheers,
    Jan



    [/QUOTE]
    [HR][/HR]
    @Almnudler: Generally when there is an issue (like this one or the F18 trim) can you please not make assumptions where our overall roadmap is headed? Thank you :)
    Other people on the internet read your opinions and get the feeling that everything is wrong when in fact only a detail was beeing discussed.
    Just because me or someone in our team makes a small mistake (like me forgetting that there are indeed users that want to use analog trim) this does not mean that we are drifting away from a realistic simulation or that it is the end of the world. It is great if you report the bug or explain the issue to us but it certainly does not hep us when you repeatedly draw conclusions about our development based on few observations. Best is to report a bug and document the observations as detailled as possible, leaving out any emotions.
    I know for a fact that everyone in our team tries to gather as much information about the real wold aircraft as humanly possible and is always concerned about creating a realistic and authentic looking and feeling simulation. We are human beings that will make mistakes, some values are not available to the public (like the spring constances of the F18 main landing gear) so we might have to guess or evolve them; and there is a huge number of users with a wide range of experience to consider, different hardware setups with all kinds of limitations that we have to keep in mind (also mobile/desktop differences). So we will continue to aim for a realistic simulation for all of our users.

  • your quote on human beings impresses me, and i can only praise your attitude.
    my comments tend to get straight once issues seem to remain unsolved, sorry for that.


    Please continue your fabulous work and aim for max realism.
    I am positive you will find the correct mass balance code.
    Hopefully carrier operations will be implemented too.

  • If the nosewheel can deflect 5 or 10deg it's not locked. On the DR400 it's basically a fully automated switch between low and hi. (...)


    I'm afraid we're just playing with words. There's no low or high, it's simply a lock that prevent the wheel from steering any further.
    Low would mean the deflection is progressive over the rudder pedal range, simply with a reduced ratio. It's not the case... Try steering the aircraft with the lock not released, applying a little pedal or full pedal gives exactly the same result : the same, limited wheel deflection. In that sense it's a lock, simply with some play.
    As you say, the slight wheel deflection is enough to keep the aircraft on track without oversteering...


    Cheers
    Antoine

    Config : i7 6900K - 20MB currently set at 3.20GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • Well in the upcoming Aerofly FS 2 dr400 aircraft we have modelled that locking (for all aircraft with front wheel steering actually)


    Thanks for the info. I'm really fond of AFS and there are really good things coming up. The most demanding aspects of the simulator are already there and prove to be yet nicely efficient : the graphical engine. I'm pretty confident systems simulation will grow up with the sim. BTW, looking at our beloved other Flight sims, state of the art editors like A2A hardly use native systems modelling, but they more and more integrate proprietary external routines to render aircraft behaviours... When the aircraft SDK allows it, I don't see any reason why it could not be the same with AFS2 whenever some system is not natively featured (or not detailed enough)...


    Cheers
    Antoine

    Config : i7 6900K - 20MB currently set at 3.20GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • @OP,
    Make sure you look through the topic on this forum about exponential control. Jan provides some great detail on how to edit the tmd file for any given aircraft so as to make the control sensitivity just what suits you best. Our joysticks do not have the same physical feel as the real aircraft and so we have to adjust.


    Dave

  • 1.I'm afraid we're just playing with words. There's no low or high, it's simply a lock that prevent the wheel from steering any further.
    2.Low would mean the deflection is progressive over the rudder pedal range, simply with a reduced ratio. It's not the case... Try steering the aircraft with the lock not released, applying a little pedal or full pedal gives exactly the same result : the same, limited wheel deflection.
    3.In that sense it's a lock, simply with some play.


    1. No playing with words, if it intentionally moves 5 or 10deg it's simply not locked
    2. No, it's rather the opposite. If the pedal range would as limited as the nosewheel steering it could be considered locked.
    If you have the full pedal movement range but the steering is limited than it's exactly that. A limited deflection or low gain/mode.
    3. If a locked steering has a play of 5 or 10deg the plane would be grounded immediately ;)


    Jet-Pack (IPACS)
    Every flightsim developer claims to have the best flight dynamics but so far I don't see a significant difference when flying.
    Fact is that the MB339 doesn't snap or spin at all and the Extra can do things in a spin that are impossible for any airplane IRL.
    Also the F-4U was infamous for the large torque moment and a quite a few were lost in go-around accidents when the pilots at low speed applied full power and the Corsair simply rolled on its back. On the Aerofly version there's almost no noticable torque moment.
    As the thread is also about the F/A-18, the CG on the Aerofly F/A-18 seems to be too far aft because you can keep the nose up after landing way too long.
    Most carrier planes have the main gear further aft than normal planes and the nosewheel slams down after touchdown for that reason.
    That's the reason why the F/A-18 landing gear is so complex and failure prone because the point where it's mounted is at the same position where it was on the original land based YF-17, only that on the YF-17 it was a simple straight leg.
    So they had to add this large trailing link on the F/A-18 to get the main wheels much further aft.
    Concerning CG; seems to be too far aft on the 747 as well because during take off the nosewheel strut starts to extend at 30kts and the nosewheel lifts off the runway at 50kts with full aft yoke.


    Almdudler, appart from the too soft suspension on the F/A-18 and the CG location I don't see anything wrong physics wise concerning ground handling.
    What airplane response would you expect with full thrust, full nose down and full aileron input???


  • Almdudler, appart from the too soft suspension on the F/A-18 and the CG location I don't see anything wrong physics wise concerning ground handling.
    What airplane response would you expect with full thrust, full nose down and full aileron input???


    Suspension does not seem wrong, CG neither.
    Once they put some payload on and lock the nose wheel, i could analyse and tell more.

  • Take a look at the various RW videos about F/A-18 landings, especially crosswind landings and you will see the suspension is way too soft.
    What does CGI (except computer generated imagery) stand for?
    So at first you are saying basic physics are wrong and now you say that you can't tell what's wrong?
    If you want a 'locked' nosewheel simply don't touch the rudder.

  • This one looks more promising: https://www.youtube.com/watch?v=7GQULamPdBI
    You can see that the airplane has a stiffer gear than we currently model but you can also see A LOT of aileron input used on roll out. I don't know if that is the pilots input or if the f18 flight controller compensates any roll on the ground there.
    And you also see a tiny bit of tilting left right, but again mostly corrected due to the aileron deflections... Also note the full up elevator on landing...


    So maybe we can do a combination of changes to make the F18 in the Aerofly FS 2 less tilt sensible. First of all the nose gear deflection should of course be reduced, then the main landing gear swing needs be stiffer. Maybe I can add a little roll compensation on the ground to the flight controller, that adds a bit of aileron when ever the aircraft tilts on the ground. Maybe move the CG forward a tiny bit so that the front gear is harder to hold up...

  • very nice video Jan. Gladly this fellow took some additional fuel tanks with him for all these go 'rounds lol.


    i think we can agree, the gear construction (with some electronic support) won't let the mainframe tilt laterally (tolerance of some degrees).
    The USN would not have purchased anything that would, right? (Imagine the explosive consequences on carriers ...)


    still trying to find one of my own ones, showing that finnish tango twist 180 degrees on spot around own length axe (best thing i ever had on celluloid, unfortunately more than 12 year ago)

  • a combination of changes to make the F18 in the Aerofly FS 2 less tilt sensible. First of all the nose gear deflection should of course be reduced, then the main landing gear swing needs be stiffer. Maybe I can add a little roll compensation on the ground to the flight controller, that adds a bit of aileron when ever the aircraft tilts on the ground. Maybe move the CG forward a tiny bit so that the front gear is harder to hold up...


    fully agree.


    if you prefer keeping it simple, how about a bank limit on ground? (F/A-18 WOG only)
    Fly-by-wire pushes counterforce to the one suspension of the lowering wingside to avoid loss of lateral stability.
    Let me know.


    Tilt forward could be increased (pitch play/front wheel suspension), e.g. WOG fullstop from 10-15kts +10 degrees down.


    How about replacing the sounds? have you found a way?

  • 1.bbrz, provide me your videolink please, showing an F/A-18 tilting laterally.
    2.i think we can agree, the gear construction (with some electronic support) won't let the mainframe tilt laterally (tolerance of some degrees).


    1.??? See point 2.
    2.The 'gear construction' has nothing to do with lateral tilt, nor is there any 'electronic support'...it's simply the fact that on the Aerofly Hornet the suspension is too weak/soft.


    BTW, the Hornet manual states that the NWS is the most effective means of directional control during take off and landing because the rudder isn't effective below 75-85kts.

  • if you prefer keeping it simple, how about a bank limit on ground? (F/A-18 WOG only)
    Fly-by-wire pushes counterforce to the banking suspension.


    Why would you want to add a phantasy feature if it's sufficient to strengthen the suspension?

  • Very interesting to see all this technical discussion. Clearly lots of potential to tweak the sim, which to me says there is a very clear and well defined data model.


    Just one thing I want to respond to:


    If you want a 'locked' nosewheel simply don't touch the rudder.


    This doesn't work for me. If I turn 90 degrees onto the runway then brake to a standstill, the current F-18 continues to oscillate about its yaw axis for several seconds, even though it's not rolling. So even if I'm lined up dead straight, the nosewheel will end up with a small random offset, with the result that my takeoff run will begin to veer off. Often the offset is so small that I'm going quite fast before I realise I have to correct.


    I've gotten quite good at keeping it straight, but really I'd like to demo this to friends and let them experience the afterburner takeoff and climb out. I can't really do that ATM because lacking familiarity they will likely veer off the runway and/or crash.

  • @ jetpack:


    Hi Jan, ich habe 2 Fragen und 1 Hinweis:


    1. Wie habt Ihr das Gewicht z.B. bei der F/A-18 verteilt (auf den Gesamtkörper)? und wo kann ich diese Werte sehen?
    2. Wo genau sind die Parameter für die Auswirkung der Pedaleingabe auf die Rollbewegung der Längsachse? (also der Nebeneffekt von lateraler Verschiebung auf das seitliche Abkippen, welches ich normalerweise mit dem Seitensteuer gegenkompensieren würde).
    3. Meine Sensitivity Einstellungen für Pedale und Joystick sind weit unterhalb 30%, um einigermassen realistisch fliegen zu können.
    Die Default-Werte bleiben ein Thema.


    Danke schon mal für die infos, ich glaube, wir können da noch was rausholen.