Good question. There are several ways to start up a radial engine, but here an inertia starter is used. Someone cranks a flywheel that spins, then the starter is engaged using the inertia power from the flywheel to start the engine. This flywheel could also be spun with an electric motor, but hand crank is more traditional and was common during WWII to start this type of engine.
Actually, it's pull ring rather than a push button. That engages the clutch between the spinning flywheel and the engine gearset. The clutch makes the loud whine. This airplane has no electric system.
My very first ag seat, over sixty years ago, was in a machine very similar to this one, with an inertial starter, exactly like this. Someone asked how it worked. Note that I'm not a mechanic, but basically, what you're doing with the cranking is manually turning a heavy flywheel at the rear of the engine, inside the airplane, behind the engine, that is geared to the engine crankshaft, but through a manually operated clutch. The whirring noise is just gearing and bearing noise from the flywheel. (Which I always thought was an impressive sound!!) The 'clutch' remains disengaged .... until you pull the start/engage handle. All this works in the reverse function of an automotive clutch. When you pull the T-handle out, the clutch engages and transfers the spinning flywheel inertial energy to the engine crank shaft, thereby providing rotating energy to the engine crankshaft, and (hopefully!) starting the engine. When the T-handle is released, the clutch disengages, and the flywhell just spins down and remains inactive for flight ops. But ... thing is, the disadvantage is that you're still hauling the weight of the fly wheel around with you. Fly wheel/inertial starters may work well, but the payload penalty was a negative for crop dusting ops. And yes! To do this safely, you DO, or should have a helping hand. These starters ARE heavy, but beats the hell out of propping a larger engine. And you will notice ... the helper, WAS careful to stow the crank in the baggage bin/aft fuselage!! Won't do to be off base and not have the handle with you!! LOL
How do you set timing? Do you have a given rpm range to dump the starter clutch at where there is enough ignition advance for the motor to start? Amazing video
Ok, two things I don't like here. One is that the pilot engaged the starter before the cranker walked away. That's dangerous. Second, it seems like the engine was kicking back because the timing was advanced too far on startup. Please correct me if I am wrong. I like to learn about these sorts of things.
know nothing of the timing, but it's the cranker who started the engine, there's a pull ring next to the crank that engages the clutch to start the engine, you can see him reach into the compartment and pull it just before it starts.
Stearman has an old engine and a big engine. Perhaps the aircraft you're referencing was smaller displacement and therefore the flywheel didn't have to be as heavy to get the motor to turn over?
