Text Box: WARBIRD NOTES #28    19 Apr 99      (10)       INERTIA vs DIRECT CRANKING STARTERSComments and thoughts I’ve received about “hydraulic lock” has raised some questions about the “pulling through” by hand vs “bumping” or “turning through” with the aircraft starter.  As we all realize by now, strong personalities (given to equally strong statements) exist on both sides of the fence on this perpetual argument.  And both Warbird Notes that I’d written on this subject only seemed to add further discussion.  They’ve also provoked the inevitable recitations of procedures used by the various operators.  I discussed this in Warbird Notes #9 (Hydraulic Lock - - - Revisited), which was itself written in response to the loud arguments that Warbird Notes #1 (Hydraulic Lock) had caused!  And, as in so many things, their arguments all contain certain elements of truth (both anecdotal and documented) offered as justifications.


If we take a look at the way an “inertia” type starter works and then an equal look at the way a “direct” drive does the same job, we’ll find that xxxxx.  


yet to write:


A great deal of concern has been expressed over whether “bumping’” the starter causes – or could cause – welding of the electrical contacts within the starter’s actuating mechanism. 


     We also get into the question of how to properly actuate the starter switches to “bump” the propeller through.


     The actual (or at least the first) inertia starter was one of the type I have on my Stearman.  Insert a crank in a receptacle on the side of the cowling and start cranking to build up the speed of the flywheel.  Faster and faster, airplane rocking more and more on the gear, the cranker-person exhausted and ready to drop, after a crescendo of whining noise is reached, remove the crank and pull the T-handle to engage the starter.


R. Sohn   ©    1999

 Back to the Warbird Notes Index Page