timc Posted October 18, 2010 Posted October 18, 2010 Does anyone know if the manual reversion system can be tested with both hydraulic systems still active (ie engines running and all fine)? I switched to MR earlier without having any hydraulic failures to prompt it (ie, I was testing) and the hydraulic pressure wound down to zero (expected) then the aircraft pitched up and down voilently (not expected). I was anticipating a nose down attitude after about 4 secs after switching to MR but not the oscillations. The airbrakes were opening and closing like crazy and once I had stabilised this I couldn't bank or pitch the aircraft. Pitch trim still worked - as it sets out in the manual. Any thoughts?
CrashEd Posted October 18, 2010 Posted October 18, 2010 This may (or may not) help: http://forums.eagle.ru/showthread.php?t=59540
Headspace Posted October 18, 2010 Posted October 18, 2010 In my testing, the pitch down occurs as expected but the oscillations start once you put any significant pressure forward or aft on the elevator. I'm currently trying to figure out what's causing the oscillations--whether it's intended function of the sim or if it's supposed to be your pilot guy pulling back and forth as hard as he can as you put control inputs in and inducing the oscillation.
timc Posted October 18, 2010 Author Posted October 18, 2010 This may (or may not) help: http://forums.eagle.ru/showthread.php?t=59540 Thanks. I'd had a look at that and whilst it is good for explaining how the trim and MR systems work, it doesnt help explain the pitch oscillations or the speed brake flapping.
BlueRidgeDx Posted October 18, 2010 Posted October 18, 2010 I haven't tried the MRFCS in DCS yet, however there are a few clues as to how it should operate in the various docs. The stick moving in uncommanded directions is likely a result of aerodynamic forces acting on the control tabs, which then act on the stick. Without hydraulics, there isn't any SAS either, and there is no damping of the natural phugoid oscillations that result from pitch/power changes. Out-of-trim situations exacerbate the problem, and PIO's are likely. The speedbrake flapping is inexplicable since hydraulic power shouldn't be available to operate them cyclically. To ease transitions into and out of MRFCS, establish level flight with airspeed between 180 and 210 knots, ensure the flaps are retracted, and trim for level flight. Transitioning to MRFCS with the flaps extended results in extremely high stick forces, and level flight might not be achievable. "They've got us surrounded again - those poor bastards!" - Lt. Col. Creighton Abrams
Headspace Posted October 18, 2010 Posted October 18, 2010 The speedbrake flapping is inexplicable since hydraulic power shouldn't be available to operate them cyclically. That's what I was thinking. timc, did you have the emergency speedbrake retract switch on as well?
timc Posted October 19, 2010 Author Posted October 19, 2010 That's what I was thinking. timc, did you have the emergency speedbrake retract switch on as well? No, I had ensured flaps were up and speedbrake was retractd (but not via emergency retract). I had wondered if the oscillations were PIO or possibly as a result of overspeed for the MR condition. I'll try again and see what I get.
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