BDizzle Posted April 14, 2011 Share Posted April 14, 2011 Can someone explain the TD valve brake to a dummie? I read the line or two about it in the -1 but I can't visualize where it fits and how exactly it works. Quote Link to comment Share on other sites More sharing options...
NATOPS1 Posted April 14, 2011 Share Posted April 14, 2011 Only a dummie if you dont ask... and think you know... The brake keeps the TD metering valve needle "locked in place" (Same fuel correction). With the throttle above crossover 65 degrees (66 for real) and with the TD switch in AUTO fuel correction occurs. Placing the TD switch in "LOCKED" ("LOCKS") this corrected fuel bypass. As the throttle is moved to either increase or decrease power the "LOCKED Correction" remains the same, as the brake is "LOCKED". If there is a TIT increase above 1077, the brake will release and the metering valve needle will reduce fuel to limit the TIT Quote Link to comment Share on other sites More sharing options...
BDizzle Posted April 14, 2011 Author Share Posted April 14, 2011 It's energized released, correct? So when I'm flying around in auto the brake is energized released, when I go to locked it deenergizes to hold bypass, then is reenergized released in null? And the little motor in there simply isn't strong enough to overcome the brake? Quote Link to comment Share on other sites More sharing options...
pjvr99 Posted April 15, 2011 Share Posted April 15, 2011 ..... the little motor in there simply isn't strong enough to overcome the brake? That's the operating theory, but every once in a while, the TD brake lock test passes, but fails TD system check by losing TIT and fuel flow when the switch is moved from AUTO to LOCKED with the anti icing on. Even though the brake may indicate LOCKED, the valve may still slip away to the NULL position ...... Quote Link to comment Share on other sites More sharing options...
NATOPS1 Posted April 15, 2011 Share Posted April 15, 2011 It's energized released, correct? So when I'm flying around in auto the brake is energized released, when I go to locked it deenergizes to hold bypass, then is reenergized released in null? And the little motor in there simply isn't strong enough to overcome the brake? Yes, Auto-- Energized released so the motor can position the needle as required. Locked-- De-energized (spring applied) engaged. Motor cannot move needle. (Yes, "little motor in there simply isn't strong enough to overcome the brake.") If TIT gets to 1077 the brake will be energized (released) and the needle will move as required to limit TIT. Null-- The DC side works (brake energized released) but there is NO ac power for the Amp to drive the motor. Quote Link to comment Share on other sites More sharing options...
tenten Posted April 15, 2011 Share Posted April 15, 2011 As brothers mentioned with some details. Location: The solenoid operated brake (TD valve brake) is a part of the TD Valve Unit (the brake is located within the TD motor-generator shaft) Function: Used to lock (stop) the movement of the motor shaft which control the Bypass Control Needle Valve (Null orifice) when switch selected to LOCKED. Operation: In Null and Auto the brake is energized to release (against spring load) and to let the motor shaft free to take the proper position. The LOCKED position (which normally selected with throttles above x-over to maintain a specified corrected position) the solenoid operated brake will be de-energized thus bushed mechanically by the spring action to lock the motor shaft ; and will remain locked until signalled (energized) by TD amp if an over temperature occurred (+1077C) or switch repositioned to Auto or Null. Quote Link to comment Share on other sites More sharing options...
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