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Discussion Starter #1
A helicopter was flying over my house just a minute ago, and it got me thinking about turbine engines and jet fighters.... the spin up to 100,000 RPM creating all these forces: air compression, thrust, velocity, and what have you.

Well, remeber the old prop planes of the, the old rotary type? wiki
Rotary engine - WW1
.... Rotary engines have all the cylinders in a circle around the crankcase like a radial engine (see below), but the difference is that the crankshaft is bolted to the airframe, and the propeller is bolted to the engine case. The entire engine rotates with the propeller, providing plenty of airflow for cooling regardless of the aircraft's forward speed. Some of these engines were a two-stroke design, giving them a high specific power and power-to-weight ratio. Unfortunately, the severe gyroscopic effects from the heavy rotating engine made the aircraft very difficult to fly....
So when the pilot wanted to turn left, he forced the plane right.... when he wanted it to go up-left he aimed down-right.... basically counter steering the plane (modern marvels teaches you extra things)....


So with these high-end jets of today producing hells amount of thrust and RPM range.... how much would the gyroscopic forces be at play?
 

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Discussion Starter #2
where's there an aviation forum when you need em ? :huh: :laughing:
 

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So when the pilot wanted to turn left, he forced the plane right.... when he wanted it to go up-left he aimed down-right.... basically counter steering the plane (modern marvels teaches you extra things)....
Umm, no.
 

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Discussion Starter #5
well i do remember it from a modern marvels show.... might not be the exact left to right ratio but basically they were backwards in handling which mae the planes have terribly difficult.... but anyways wrong left to right ration behind, would not the jets have to fight these forces too?
 

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would not the jets have to fight these forces too?
No. The forces that made those planes hard to control were torque and p-factor (which is still a factor in most single-engined propeller aircraft).
 

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From brief reading about p-factor, why would it be any different in a radial engine as opposed to a rotary one? The propeller is the same either way.
 

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Discussion Starter #8
From brief reading about p-factor, why would it be any different in a radial engine as opposed to a rotary one? The propeller is the same either way.

nope its not the rotary you're thinking of , the mazda rotary... its completely different.... the radial engine has the propeller attached to the crank shaft.... the rotary has the propeller attached to the engine, and the whole engine spins with the propeller, all that mass from the engine block spinning totally threw off the plane having adverse gyrscopic handling

what's p-factor.... propellers?
 

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P-factor isn't any different between radial and conventional motors, but the additional torque (or whatever the technical term is for the rotational force from the radial motor) makes the aircraft want to turn even more.

It's not going to be enough to reverse controls or anything like that. Remember, airplanes deflect air to change direction, a rotating engine will do nothing but cause a slight tendency to turn or rotate, especially during significant changes in throttle.
 

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what's p-factor.... propellers?
P-factor is caused by the asymmetrical thrust created by the propeller (primarily), as well as airflow off the propeller which spirals around the fuselage of the airplane and end up hitting the vertical stabilizer (secondary, much less of a factor); causing a turning tendency that is normally counteracted by a small application of rudder in the opposite direction. The force is most notable in situations where you are at high power, and low airspeed (such as initial climb).
 

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Ochoa: I'm completely with ya on the difference between rotary and wankel motors.

Snake: Since p-factor is a function of the propeller, it really shouldn't matter if it is powered by a radial, rotary, jet turbine engine, or a set of hamster wheels chained together. You mention torque, which I understand to mean that the plan tries to roll counter the propeller motion when power is increased, and the other way when power is decreased, this would make sense as well. But I see what ochoa is asking in regards to gyro forces. Assuming the prop spins clockwise, a plain should have a tendancy to dive when yawed (is that a word?) right, and rise when yawed left. Likewise, when diving, the plane should try to roll to one side. I have no idea how sagnificant the effect will be, but it should be there, since the engine is a gyro, and turning the plain does move that gyro's axis.
Ochoa: gyro forces are a variation on momentum, While a jet engine spins very fast, the blades are relatively light, and it is pretty small in diameter (ignore the giant fan on the front) slowing down the points at the edge of the blades.
 

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Vash: not quite. The situation you suggest assumes that the forces act 90* off. That is true in helicopters, but with aircraft props, it's a whole different concept. Assume that a plane has a single blade prop, and the propeller rotates clockwise, as viewed from the cockpit (CCW if looking head-on). The descending blade takes a bigger bite out of the air than the ascending blade, causing it to generate more thrust. This will pull the nose of the aircraft slightly to the left. It is most notable in nose up flight with a high power setting. I know from experience that when you are nose-up in a single-engine prop, at slow speeds (approaching stall) with high power, you have to apply considerably more rudder to counteract p-factor than in straight-and-level flight at cruise power settings.
 

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Adding to the above, torque is most notable with a radial because of the rotational mass.

Also, there really isn't p-factor with a jet because of its compact design and (i would imagine) many more blades, thus reducing the difference in thrust for each one. When you just have one blade to provide the power, you'll notice the difference between that thrust. When you have a hundred blades, I think the difference in thrust provided is much less noticeable, to be practically non-existent. I'm looking into it as we speak, and I may have to call on a couple friends (one flies for airlines, the other is a jet instructor in the AF) to get a definitive answer.
 

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Discussion Starter #14
thats interesting.... the downward prop gets a bigger bite then the ascending blade

i think vash got the message, but i think snake is focusing on the acceleration and decelleration of the prop, the torque.... the helicopter with no rear blade effect
 

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Discussion Starter #15 (Edited)
well this Q poped up in the noggin that simplifies this whole thread to a single question.... would a lesser diameter spinning at high speeds not have as much gyro forces as a large diameter as slower speeds?


snake: my rotary engine is the only thing that holds this gyro question any water, any other type of aircraft engine will probably not seat well, but they too also apply to this at the same time....
 

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The descending blade normally gets a bigger bite due to the angle of attack. That's why it becomes increasingly noticeable in nose-up attitude.

helicopters are an entirely different animal. The complexity of controls is on a much grander scale.

And i still don't think the assertion that controls are reversed for a radial engine bears any truth. Once again, you're talking about a rotating force vs. aerodynamic controls.
 

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Discussion Starter #17 (Edited)
well there two faces that affect the plane and one that doesnt effect.... when the plane rolls there are no gyro affects of any sort, right? but any other direction will have some type of affect?

i shouldn't of even said ^that^, its completely ignoring your experiance and intellengence of avaition :banghead:
 

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I'll have to put some thought into that. In a radial engine, it would seem that is the case. OTOH, in a horizontally opposed motor, it would seem that there may be some resistance (though I don't know if you'd call it gyro, since it's not rotational).

BTW, I'm not a prof. pilot by any means. I've not even logged 200 hours PIC. I'm actually glad you're asking these questions, because it's forcing me to get back into that mindset, which I've been out of for far too long.

:cheers:
 

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Snake:
We gotta separate the aero forces from the gyro ones. If the engine spins, its a gyro, and should respond accordingly. When you turn or pitch the aircraft, you are moving the gyro's axis, and it should generate forces at 90deg to the original. With helicopter, this force will be overpowering, with aircraft it will be much less. Perhaps it is so slight that it can be ignored. Perhaps the heavier rotary engine increased these forces to the point that they became noticable, and that was what was throwing everyone off. Either way, the forces should be there, also they should not reverse the controls, but shift everything 90 deg.

When you are talking about p factor, and the downward blade getting a bigger bite, is this in level flight? or only while there is a change in altitude?
 

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Read some more. I didn't realize that at low speed the plane flies nose up instead of forward. Makes more sense now
 
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