Any one noticed an increase in precession with a three blade prop? My Skywagon (w/ Black Mac) wants to head for the woods with full power, modest rudder, tail coming up and a 15 knot crosswind. Yes, no, maybe?

I can see your gyroscopic procession argument. Tail goes up, force pushing top of prop, action 90 deg in direction of rotation, increases lt turn tendency. Is my remedial physics correct. I know my spelling cant be. My nose dragger 206 82inch 3 blade pulls hard to the left with out the gyroscopic action.

If you increase the mass of the gyro, the precession should increase, I think. That's why Cessna put a right rudder pedal in there, though.

MTV

Thinking here again, somebody please stop me if I'm wrong, The engine rotates to the right, gyroscopic action 90 degrees in the direction of the engine rotation, so 90 degrees to the right calling for left rudder on tail rise and then when the plane is level torque effect takes over calling for right rudder on climb.
This is why it's easy to get caught behind if you go for the left rudder correction first and too slowly and then aggravate your own problem because all of a sudden the tail is up and the plane is level and then you rotate but are now on the wrong rudder. The gyro effect is no longer needing compensation after tail rise but now you need right rudder after rotation for climb but you are not quick enough to switch.

If you let it fly off without lifting the tail there won't be any gyroscopic precession effect to compensate for because you are not changing the plane of the gyroscopes rotation and therefore no 90 degree to the right pull. Right rudder is all you will need.

TJ Carr wrote:Any one noticed an increase in precession with a three blade prop? My Skywagon (w/ Black Mac) wants to head for the woods with full power, modest rudder, tail coming up and a 15 knot crosswind. Yes, no, maybe?

Heavier prop=more precession, methinks. Number of blades just contributes to the weight.

But what do I know, I studied history

I was thinking that the additional weight did contribute to the precession... that's what it seems, anyway.

Dirtstrip,

Nope, you've got it precisely backwards. Think of it this way: When you raise the tail, you are effectively pushing the gyroscope (the propeller disc) at it's topmost point, and tilting the prop disc forward at the top, aft at the bottom. So, if you apply a force at the TOP of the prop disc, the precession effect acts 90 degrees in the plane of rotation (the prop disc), causing the prop disc to precess to the left.

This must be countered by application of right rudder. Compounding this effect is torque and P-factor, both of which also cause a turn to the left.

MTV

You are right! On rotation, not tail lift, it is to the right and not as strong as the forces of torque and other left turn tendencies which help to counter it. You sent me back to my basics on this one but it was the tricycle gear demo at rotation that I had recalled. Is it too late to edit?
I am still good with flying it off without raising the tail to eliminate gyroscopic effect.

I've definitely experienced the increased severity of left turning tendency while making pitch attitude changes on the ground. Lifting tail at full rpm in a taildragger is the worst of the gyroscopic precession, but also while landing using the "tailwheel low wheeling landing" method.

Even at lower rpm, the pitch attitude change of lifting the tail to "stick it on" causes a pronounced left turn, which is even harder to deal with in my experience, as the airspeed and control authority are degrading at that moment. At least at full rpm you have strong prop blast over the tail.

I can only imagine that the effect would be enhanced with a long 3-blade prop.

1SeventyZ wrote: but also while landing using the "tailwheel low wheeling landing" method.

My technique for avoiding precession when doing those is to not give it forward stick when I touch the ground, and instead bounce "gracefully" into the air and then transition to a regular wheel landing on the next touch... I call this advanced technique "The Mary Katherine Gallagher."

Oregon180 wrote:My technique for avoiding precession when doing those is to not give it forward stick when I touch the ground, and instead bounce "gracefully" into the air and then transition to a regular wheel landing on the next touch... I call this advanced technique "The Mary Katherine Gallagher."

Bwahaha! I have that move perfected.

I hate it when you guys start talking about complicated physics shit, it confuses me.
No matter what prop, airplane, or wind I've never had one depart the runway in like 37,000 takeoff's though. But sometimes I've had the pedal at the stop giving brake taps while saying "oh,shit" right before she broke ground and crabbed into the wind.
What I remember the most about precession is don't pitch up during retreating blade stall in a helicopter in cruise, it can chop off the tailboom. Reduce the collective instead.

On a Skywagon floatplane with the 88" prop the precession is very apparent because there is no tailwheel to keep it straight. When I start a takeoff run on floats the plane is pointed to the right of the takeoff path and I apply full right rudder until I'm pretty well on the step and have better rudder authority due to airspeed and not just prop blast.

With an 88" prop haven't noticed too much of a swing but size 15s come in handy...haven't flown a 3 blade version.

It can happen - two died in this C185 in Zambia a week or so ago...

lowflyin'G3 wrote:I hate it when you guys start talking about complicated physics shit, it confuses me.
No matter what prop, airplane, or wind I've never had one depart the runway in like 37,000 takeoff's though.

Yeah, but you're like...really good and stuff.

Zane,
Appreciate the thought but not so good I can't break something too. Just real lucky!

Kiwi,
You know who owns that 185? I wouldn't mind buying that Sorensen belly tank, boom assembly and whatever is left of the crunched pump. I know there are a few of those over in Africa, not so many here in the states. Lemme know.
I would think it better to jam them both on and flip her over before crunching in like that. Should've been in an Ag Truck, hopper woulda taken the hit not the soft bodies. I wonder if the engine is physically IN the front seats, looks like it could be.

Precession, Schmreesession that's what I say. Steer the bitch, whatever it takes!

lowflyin'G3 wrote:Precession, Schmreesession that's what I say. Steer the bitch, whatever it takes!

Fuckin' A

Gump

lowflyin'G3 wrote...You know who owns that 185? I wouldn't mind buying that Sorensen belly tank, boom assembly and whatever is left of the crunched pump

yeah...human nature being what it is I think many 180/185 drivers were eying it up for spares...those tail feathers look in good shape too...

Don't have any contacts down there but know 'a friend of a friend' - will make discrete enquiries about the tank for you...