Does right thrust, or the lack of it make any difference while hovering?

Mike

YOU BET!!!

Without a little right thrust, you are always fighting it with the rudder. 2 degrees on average, however that may be hard to figure out.

Fly the plane, see how much rudder is needed, lossen the motor and add some thrust and fly it again. Better? Worse? For hovering you may need to fine tune a little at a time. Don't forget about tail weight, you may need some of that too.

mike
for hovering rt. thrust can do wonders! try it...it will certainly help!!
mayur

I am trying to understand the reason for right thrust during a hover. Clearly the airplane will try to spin the opposite direction the propeller is spinning, but why right thrust?

Probably find a good explanation in the heli sections. That's what got me started on this. All helicopters in a stable hover hang at about a 5 degree angle so I figured it would apply here too. I don't remember the reasons. Check the heli posts. I'm just going to start trying 3D with a Somethin Extra and it doesn't have any right thrust.

Mike

Ah, no actually.....the reason a heli hovers with the right skid a little low is because of the tail rotor thrust. The tail rotor thrust tries to push the heli to the left. You cancel this with right cyclic input. The heli 'leans' to the right a little so the tail thrust and cyclic input balance out. Most people doing their first hovers ask why the heli keeps wanting to wander to the left......

Right thurst is required to compenstate for the left turning tendencies of the airplane. Some of the left turning tendencies of an airplane in flight would also apply in a hover.

The left turning tendency of a single engine airplane is due to four things in order of magnitude:

1. Torque - the prop is turning right, the reactive force is the airplane wanting to turn left. In a hover, you are high RPM's. This is also the reason you can do a torque roll.

2. Propeller Factor or P-Factor - in slow flight at a high angle of attack, the descending right blade has a higher level of attack than the ascending left blade. The right blade generates more forward lift than the left blade causing a turn to the left. In an ideal hover the prop would have an ideal angle attack, but it is like balancing a plate on a stick; you are always correcting.

3. Slipstream Effect - In addition to pushing the air, the prop also rotates it in clockwise direction. This swirling air hits the vertical stab on the left side and causes yaw to the left.

4. Gyroscopic Procession - The spinning prop is just like a gyroscope. If you apply a force to a spinning gryo, the gyro resists the force and the reacting force happens 90 from the direction you applied the force. So, when you tip the nose down the resulting effect is is a yaw to the left. This is the least of the four effects.

Hope this helps.

You must have been, or are, a flight instructor. Good explanation.

Your explanations are good but I can only see where #3 applies to a hovering situation.

#1 the reaction force of the prop on the airplane would cause the airplane to roll left, which it does. How would right thrust correct this in a hover?

#2 with the plane hovering the angle of attach of each half of the propeller should be the same not favoring one side of the other.

#4 there will be a gyroscopic effect due to application of rudder and elevator. Applying up elevator will cause a right yaw and down elevator a left yaw. Since I am using both it should be a wash.

Your explanations are clear but I don't see how they apply to a hovering situation.

Thanks

Actually, I am about 15 hours into getting my private pilots license so the information is pretty fresh in my mind. Everything that I have learned so far has really polished my RC flying and my understanding of aerodynamics.

My instructor just said the most feared words of any student pilot, "You know, you are going to solo next week". I got the same knee shakes that you get when you solo in RC.

I used to fly myself. I soloed on a really calm day around dusk when the wind died to about zero. What a great feeling ( a little scary ) when you take off and realize you are the only one in the plane

Have fun flying.

Laser

Never got the feared words. Showed up, went out dual and did two touch and goes and a full stop. The instructor got out and told me give him another. My first thought was you must be nuts! But it worked out great, what a feeling! They know when you're ready, trust them. Good luck and have fun!

Mike

Well all the advice given to this post sounds good on paper ,However in the three years needed to prefect the hovering gig I've found that only the V E R Y overpowered planes Such as the profiles with 91 Satio or to that efect will be a problem. The continuios throttle transition will cause the airplane to torque over to the left. When you get more experence it's a great lesson to remove all the thrust and even set the airplane up a little nose heavy. In other words (remove the tranning wheels). Hope this helps... DAVE

Laser200 and others who explain the P-factor.

I took flying lessons about two years ago, I have about 13-15 hours in a Cessna 150 and soloed two local airports. After ground school I lost interest, maybe I''ll complete it one day.
Anyway, I questioned the P-factor with mmy instructor. It seemed quite silly to me, that on one page, the gyroscopic precession is mentioned and explained, and all that explanation goes out the windoow when the P-factor is explained. GP should also apply to the P-factor, and in stead of yawing the plane left, it should pitch the plane up. I was adviced not to question this when taking the test he he.
Just my two bits.
DKjens

If you want some hands on experience with the P-factor without acually flying a plane just crank up your electric starter and rotate it quickly upwards. You'll be amazed at the yank it has. It is the same priciple of a spinning prop on the front of a plane.

The gyroscopic effect is really amazing. When I raced r/c cars I could actually correct the attitude in the air by hitting the gas or brakes to control pitch and by just turning the wheels to control roll. On a big jump I could correct a 45 degree roll and still land on all fours.

Consider the application of Right Thrust as "Engine TRim" if you will.....That your powered plane has many built in effects to cause it to "go left" RIGHT thrust is to correct for these built in features so that the plane is neutral in all axis when the plane is perpendicular to the ground........Now of course getting the plane straight up and down ....correction for wind and power....wing....all sorts of other things that the pilot must correct
for as variables is the fun part.....Just like a heli hovering...if you're in that sweet spot...it will sit there....BUt that doesn't mean it doesn't need correction to stay there

During your attempt to hover, it will be item number 3 the Slipstream Effect, also known as Corkscrew Effect that is the biggest culprit.

The engine power is very high and the airflow or forward progress of your airplane is nearly non existent. The Corkscrew Effect is VERY pronounced and can be visualized as very tight threads like a screw twisting around the fuselage. Therefore the twisting slipstream does push hard on the rudder from the left side (for American engines that turn clockwise) and therefore the need for the pilot to hold a significant amount of right rudder during the maneuver.

Much of that can be adjusted by fixing right engine thrust. One would probably not put enough right thrust to totally remove the need for some application of right rudder. Most full scale aircraft designer’s attempt having just enough right thrust for the most common flight regime, which is level flight. During climbs and descents the pilot must make the adjustment. That is, hold right rudder during climb and left rudder during descent.

It is also significant that a large amount of air will sneak through the hinge line and rudder authority can be significantly reduced unless the builder applies gap sealing to the hinge line. Simply applying gap seals can effectively be the same as a 20 per cent boost in rudder authority.

By the way, Slipstream or Corkscrew Effect is the predominate torque problem for airplanes and as long as the prop is turning (or not) it is an issue. The other three pales in comparison, and exist briefly during certain phases of flight

The student who did the initial explanation is to be congratulated for learning his lessons well. Good luck in your hover practice ---
Hope this helps.

CFII - Single and Multi Engine Land