NoJoe Posted May 22, 2012 Posted May 22, 2012 (edited) Normal mode: Trim input for Nose Up Trim tab moves up Increased airflow hits trim tab, generates downforce on elevator Elevator locked by hydraulic pressure Downforce on elevator transferred to tail Nose moves up Manual Reversion: Trim input for Nose Up Trim tab moves up Increased airflow hits trim tab, generates downforce on elevator Elevator not locked by hydraulic pressure, elevator moves down Increased airflow hits elevator, generates upward force on tail Nose moves down How do you not understand this? Actually that's not quite right; it's more like: Normal mode: Trim input for nose Up Hydraulic "stick-feel" feedback mechanism moves to change the "center" position of the stick (resulting in elevator deflection in the nose up direction) In this mode the trim tab mechanically moves with the elevator, and does not act like a traditional trim tab. Manual Reversion Mode: Trim input for nose up Electrical trim actuators operate to move trim tab down (trim tab is now independent of elevator movement when there is no hydraulic pressure) Aerodynamic forces then move the elevators upward This pushes the tail down, moving the nose up. (operation in the sim right now is reversed compared to this) ^^ That's how I expect it to work, based on how trim tabs operate on real planes, but I don't know for certain if the A-10 does this. That's why I'm very curious to hear from someone who actually works on them. Remember that the normal trim operation and the Manual Reversion trim operation use two independent systems. According to the Dash 1, it appears that the trim tabs only operate as traditional trim tabs when in Manual Reversion mode (via the electrically operated actuators), so it seems like there's no reason for them to be reversed. That's why I feel like the operation is incorrectly reversed in the sim right now. But again, I don't know for certian, and I'm just going off my understanding of the Dash 1, and my understanding of how other planes fly. --NoJoe [EDIT] Added the last line under "Normal mode", above. Edited May 22, 2012 by NoJoe
Snoopy Posted May 22, 2012 Posted May 22, 2012 (edited) Actually I checked and the elevators operate incorrectly in manual reversion as a whole, real life, elevator movement isn't controlled by the trim tabs in manual reversion but in the sim that's what appears to happen. I'm going to do more testing this evening and report on the testers side. Folks...the ONLY trim tabs that are independent in manual reversion are the ailerons. The elevators are not set up the same as the ailerons, in manual reversion the pilot still moves the elevator via cables. Same as the Rudder. PS....I've posted multiple times on this topic, I actually work the A-10 (most here know that so I don't normally post saying as such). ADDED.... Not from the -1 but another training document for real A-10 pilots concerning Manual Reversion Exercise.... 1. Ensure airspeed is between 1800 and 210 KIAS, altitude at 10,000 ft, flaps retracted, trimmed for level flight 2. Move MAN REVERSION switch 3. Pitch Trim. Check the pitch trim prior to maneuvering by actuating the pitch trim in small increments. Do not run the trim as this may result in excessive stick forces or PIOs. 4. Maneuver Guidance. Move throttles slowly when varying power, do not make rapid throttle movements. WARNING: The cumulative effects of rapid throttle movements, failure to use pitch trim, and high-speed maneuvering/dives while in manual reversion could result in stick forces beyond the physical capability of the pilot to recover the aircraft. There are a few additional items but not usefull to this thread. Here is a shortened version of the 1A-10C-1 MANUAL REVERSION FLIGHT CONTROL SYSTEM (MRFCS). The MRFCS is an emergency system for use when dual hydraulic failure is impending or has occurred. The mode is adequate for executing moderate maneuvers. Landing should only be attempted under ideal conditions or when ejection is not possible, since any degradation beyond normal reversion may make landing impossible. When MAN REVERSION (Figure 1-17) is selected, roll control is transferred from the ailerons to the aileron tabs. Selecting MAN REVERSION also closes hydraulic shutoff valves preventing unexpected return to hydraulic powered flight control. Manual reversion trim is provided only in pitch. Pitch (elevator) MRFCS The same components are used for manual and hydraulic pitch control. Electrical control of the two elevator trim tabs is automatically achieved when both hydraulic power sources have dropped below 1,000 to 800 psi. Artificial feel is retained. Yaw (rudder) MRFCS The same components are used for manual and hydraulic pitch control. Roll (aileron) MRFCS When MAN REVERSION is selected, stick commands are disconnected from the aileron actuators and connected to the aileron tabs. In this tab drive mode, the aileron tabs fly the aileron surface to the position commanded by the stick. Edited May 22, 2012 by Snoopy v303d Fighter Group Discord | Virtual 303d Fighter Group Website
Bushmanni Posted May 22, 2012 Posted May 22, 2012 Old thread about MRFCS containing some info from Yo-Yo: http://forums.eagle.ru/showthread.php?t=78625&highlight=mrfcs DCS Finland: Suomalainen DCS yhteisö -- Finnish DCS community -------------------------------------------------- SF Squadron
NoJoe Posted May 22, 2012 Posted May 22, 2012 Ah, Look at the last line in Yo-Yo's post in that other thread: http://forums.eagle.ru/showpost.php?p=1282688&postcount=16 But trim tab is probably reversed... it's a bug. There we go, I think that answers Fox One's concern about trim operation being reversed in MRFCS mode. :) --NoJoe
Snoopy Posted May 22, 2012 Posted May 22, 2012 Ah, Look at the last line in Yo-Yo's post in that other thread: http://forums.eagle.ru/showpost.php?p=1282688&postcount=16 There we go, I think that answers Fox One's concern about trim operation being reversed in MRFCS mode. :) --NoJoe Saw that...but the elevators still operate incorrectly in manual reversion, in the sim they act like the ailerons with only the trim tab moving, that is not correct operation. v303d Fighter Group Discord | Virtual 303d Fighter Group Website
NoJoe Posted May 22, 2012 Posted May 22, 2012 (edited) Saw that...but the elevators still operate incorrectly in manual reversion, in the sim they act like the ailerons with only the trim tab moving, that is not correct operation. Ah yes, that might be another issue, then. Paul, I don't know when you'd be around the Hawg next, but could you ask one of the pilots: When flying in MRFCS mode, if they move the trim hat on the stick to nose up, does the nose move up? Or down? 'Cause it moves down in the sim, and that's the issue Fox One was originally asking about. :D --NoJoe Edited May 22, 2012 by NoJoe
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