On Sun, 2010-03-07 at 15:15 +0000, Heiko Schulz wrote: > Hi, > > > > > > Hi Guys > > I think you will find on all Boeing aircraft if the > > elevator is out of neutral > > for a set amount of time the horizontal stabilizer runs to > > return the elevator to > > the null position.Hence retriming the aircraft.Hence the > > name stabilizer trim > > I think also you will find that the tab on the elevator is > > not > > a trim tab but moves in the opposite direction to the > > elevator movement. > > The tabs are to support the movements of the control surfaces and in > the case there is no hydraulic pressure anymore. With other words- > when no hydraulic only the small tabs are moved so due to the > aerodynamic forces the whole control surface is moving in the opposite > way. No idea if JSBSim can simulate this. > > Only at older jets, the newer ones has another system for hydraulic backup in > case of emergency.
Seems to me I remember a crash report where a DC10?'s center engine shelled and cut all the hydraulic lines leading to a total loss of hydraulics. Yeah, there it is: http://en.wikipedia.org/wiki/United_Airlines_Flight_232 > The whole stabilizer is the pitch trim. Before start the aircraft has > to be trimmed according to CoG. Without the aircraft would never > rotate at the given Vr. At low weight; low speed, aft CoG and some > more conditions the 737 uses a so called Auto-speedtrim which is twice > as fast as the usual Autotrim and electric trim. > > I was now able to make the Autotrim,(run the elevator to zero-position) > Autospeedtrim is still missing yet. > > My question to JSBSim- folks here: > Is JSBSim able to to simulate the forces of the whole stabilizer trim? > I used the usual trim for the 737-300, but have problems to match the > settings according to the the real one ( I have already found a table > wich shows me the angle of the stab related to the trim settings) > > Cheers > Heiko JSBSim can pretty much simulate anything if you get the math and functions right... So, if I understand correctly, we want to keep the elevator control and elevator trim, then add the ability to rotate the entire horizontal stabilizer? For simplicity break the problem down into two areas: - Flight controls driving the surface positions -- Elevator position (currently): fcs/elevator-pos-rad = (fcs/elevator-cmd-norm + fcs/pitch-trim-cmd-norm) * 0.3 -- Stabilizer position (create a new property or two) fcs/stabilizer-cmd-norm fcs/stabilizer-pos-rad - Aerodynamic effects of surface positions -- Add functions for change in Lift, Drag and Pitch due to Stabilizer position. Ron ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
