michelip Posted March 19 Posted March 19 It's my understanding that, when AFCS Altitude hold is engaged, the Phantom will continue to climb or descend according to the rate of ascent / descent at the moment of engaging it. I am finding it is very difficult to achieve a zero rate of climb, and even with an error of a few feet per minute, the altitude becomes very inaccurate after a few miles. Is there any way to lock Alt Hold to the aircraft's altitude at the moment of engaging it? Regards, Mich.
OttoSH Posted March 19 Posted March 19 There are two switches for the AFCS: Engange and Altitude hold. When you activate "Engage" the aircraft flies more or less like a fly by wire aircraft. It will hold its roll and pitch attitude and when you have less then 5° bank, it will roll the wings level and hold the heading. If you want it to hold altitude, activate the altitude hold switch. You have to activate it while your vertical speed is lower than 1000ft/min. It holds the altitude the aircraft had in exactly that moment when you activated it. So when you activate it while climbing, the aircraft will continue the climb, level off and descend back down. I find it most easy when i level the aircraft off first and then activate altitude hold. I hope that helps. Otto 1
Cat107 Posted March 19 Posted March 19 (edited) Hi, yeah, it's as @OttoSH wrote, the altitude hold function should hold the altitude at which aircraft was during engagement. So for example when engaged at angels 20 during a climb, it should stop the climb, then descent to angels 20 and then stay around it (with some limited precision). However, this system was designed during 60s and is not as robust and accurate as more modern systems. We put a lot of work into recreating it according to the documentation and trying to replicate its behaviour very realistically and therefore it has similar characteristics to the real one. For example, it may have some trouble when being engaged with high rate of climb/descent or when the aircraft is in a deeper bank or at specific speeds (for example very low near-stall speed or in transonic region). It needs some time to stabilize the altitude when you for example change throttle setting or bank etc. However, I personally I find it pretty solid and I haven't seen many complains about it so far. The way which provides fastest stabilisation is engaging the alt hold mode with near zero vertical speed and quite stabilised airspeed. Also you should check if you are not for example disabling it by moving the stick in pitch axis. Could you maybe provide a track of it struggling to keep the constant altitude? You can also read more about AFCS here: https://f4.manuals.heatblur.se/systems/flight_controls_gear/flight_controls.html Edited March 19 by Cat107 3 1
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