Can anyone answer my question about using the trim tab on a PA28 following an elevator jam? Would it be necessary to maintain a higher approach speed to ensure trim tab authority?
As IO540 says, in the event of an elevator jam, trim works in the opposite sense - trim down to go up, up to go down. I can explain it to myself, but not to anyone else!
The trim tab will work as a mini-elevator, but the sense will be reversed.
Based on fooling about in a sim (i.e, taken with a grain of salt, but useful nonetheless), rudder and elevator control authority will depend on speed to a certain extent, but mainly on propwash - carrying a bit extra power will help. As G says though, a control failure should be easily survivable, depending on the position of the control at the time of the jam - but even with jammed ailerons at half deflection (full deflection is almost never reached except on an aerobatic aircraft or in a serious sideslip), rudder should be able to overcome the problem. Even with a total jam (elevator & trim) the aircraft will probably be controllable with power and flap, unless it's trimmed for some very high or low speed.
Does anyone know if POHs usually give rudder crossover speeds?
Edit: I've seen that turboprop accident - horrifying, I thought it was a fake until looking more closely. It was just out of heavy maint I think - you can't see the controls move at any point during the "wingover", and can only imagine what the pilots were thinking before impact
