Should you pull through P&W Wasp Junior Engines before engine start?
Query on Pratt & Whitney Wasp Junior 985 radial engines as fitted to the Beaver and the RAAF CAC Winjeel trainer.
Is there a technical requirement to ensure the propeller is pulled through several revolutions prior to starting the engine? Although pulling through certain radial engines before start to ensure no hydraulic lock, has been a feature for many decades (Convair 440, DC3 come to mind) I vaguely recall a warning against this practice based on the fact the fulcrum arm caused by someone heaving on a prop blade against a hydraulic lock has sufficient power to bend a con-rod or otherwise cause internal damage.
On the other hand the starter motor clutch has slippage so that if it encounters a hydraulic lock as it tries to rotate the engine the clutch simply slips beyond a certain torque and so prevents possible internal damage to the engine. On that basis a manual pulling through of the engine is unnecessary and potentially damaging to engine components.
The info I need is specific to the P&W Wasp Junior 985 radial engine. Appreciate facts and any website link that is reliable info.