This is just my $0.02, but wouldn't P-factor cause a much more significant asymmetric load on the hub than any of us could impose?

I worked for a flight school back in the day and we frequently relocated planes by pulling on the prop near the hub. Most of the pulling occurred on fixed pitch props as the constant speed propeller airplanes were too heavy to move without help. Over the course of three years and thousands of hours, we never saw any issues with oil leakage on hubs or crankshaft damage.

OK, I'll admit this makes no sense to me. Hot mags and all--how did pulling at the prop hub cause the engine to start?

Another case of weekend warriors overthinking the simplest of things.

Most aircraft POH or AFM Have a section on "Handling/Service/Maintenance" that should address proper way of moving/towing. I would comply with the Manufacturer's recommendations. If there are none published, I would contact the Engine manufacturer and obtain guidance from them. I suspect that they would not recommend pulling on the prop hub for obvious liability reasons.

Thanks to all who replied with cogent thoughts on both sides of the coin.

Easy. If there's residual fuel vapor in a cylinder (sucked in by the last intake stroke as the engine slowed and stopped) and the crank position stopped on the compression stroke just short of where the mag get's triggered for the next power stroke.

A slight nudge pushes the piston "over the top" of the compression stroke, allowing the compressed fuel/air mixture to expand and turn the crank while also triggering the mag to generate a spark.

Best case, you get one power stroke which would be like getting hit once with s sword. Worst case, the engines starts which would be like getting hit with a Cuisinart (plus the airplane could depart the area).

A basic understanding of engines and metallurgy tells me that you can't hurt the engine by pulling on the prop and I seriously doubt you could hurt a prop hub although that might depend on the design. You could bend a blade. But I wouldn't do it regardless because of the risk of damage to ME if the engine were to fire (even one stroke).

It's not the same thing, Rick. The thread is about grabbing each blade near the root and pulling/pushing the airplane forward and back. This does not spin the propeller.

If the engine is at the right point (ie right at the top of the compression stroke on any of the cylinders) it would only take the tiniest movement to push it over the top. These engines are like firearms...don't ever point them at anything you don't intend to shoot, ie don't stick anything in the prop disc that you can't live without.

Another angle to this question?

I always thought the concern was the fore/aft movement of the crankshaft in some engines. Something to do with the bearings or messing up the nose oil seal. In flight, the shaft is of course full forward against thrust bearings, so pulling shouldn't hurt, but pushing may?

Idle in flight would be like pushing, but prop is turning as designed?

Is this really even a thread worth discussing? Moving aircraft by pushing/pulling on the prop has been a common practice for literally decades.

Use some common sense and pull towards the hub with no sudden jerky movements and it will be 100% fine.