What Do I Mean By Straight And Level?
If you have been reading this blog for a while, you have seen the phrase “straight and level flight”. So, I think we need to talk in some detail about this aspect of RC flying. Straight and level flight is somewhat self-explanatory, but to understand what it is all about and how to go about achieving it you need to understand some of the terminology of the subject.
You may not be familiar with the terms of pitch, roll, and yaw as it applies to RC airplanes. Pitch refers to the nose up and down attitude of the RC model. It is affected by the CG or center of gravity of the plane and by the up and down movement of the elevator control surfaces. The Roll axis is around the center line of the fuselage. The roll is affected by the left and right “bank” of the airplane controlled by the movement of the ailerons. And the yaw is the nose left and nose right movement of the plane controlled by the action of the rudder control surface. These are the actions of the RC airplane that determine the direction and the attitude of the model’s flight.
Basically, if your RC plane is flying ‘hands off”, that is, with no control action being applied and it isn’t drifting to the left or right and it is not drifting up or down you are flying straight and level. That sounds simple enough, but achieving straight and level flight begins with the design and building of the model. Whether you are building a kit or assembling an ARF or RTF, you still have to be aware of what it takes to have a model that will fly straight and level when you are flying “hands-off”.
Why is it so important?
If your radio controlled model will fly straight and level, it will be much easier to control and your aerobatic maneuvers will be much smoother and more precise. Also, flying and landing the RC plane will be easier and look better. It makes flying a lot more fun if you don’t have to constantly make in-flight adjustments. If a model is not properly balanced, that is, the center of gravity is too far forward or back, the airplane is impossible to fly and that may result in a serious crash. Or, at least the radio controlled airplane that isn’t properly set up, will fly so badly that you may become discouraged and give up without learning how to fly. A smooth flying, easy to handle model is a real pleasure to fly and that is especially important for beginners.
How is straight and level flight achieved?
It has to start with the building or assembling stage. Actually, it really starts with the initial design. The best advice I have to offer is to be sure to closely follow the manufacturers instructions. Several things in the construction of a radio controlled model airplane can adversely affect the quality of flight. The completed model aircraft must be balanced as specified by the manufacturer.
Of most importance is the front to rear balance or the CG. The CG or center of gravity of the model will be specified in the assembly instructions. Sometimes it is possible to correct the CG by moving the radio equipment forward or to the rear to help achieve the correct balance. Other times it may be necessary to add some weight to either the nose or tail. Either way, you need to get the RC model plane to balance where the manufacturer says it needs to balance. Adjustments to the side to side balance can be made by adding weight to the wingtips where it is needed.
Also, in the building of a kit, it is important to avoid misalignment of the various parts and sub-assemblies. Where the vertical stabilizer meets the horizontal stabilizer, use a small machinist’s square or the 90 degree corner of a drafting triangle to ensure the two surfaces are perpendicular to each other. You need to give special attention to the alignment of the ailerons, rudder, and the elevator to the top and bottom surfaces of their non-movable counterparts. I know that there is trim adjustment within the radio system, but the closer you can get to perfect with the mechanical adjustments, the easier it will be to trim the plane in flight and the better it will perform.
In some models, it is necessary to add some right thrust to the engine. Here again, follow the instructions and you will be okay. The few degrees of right thrust is to compensate for the counter torque of the engine. This helps to maintain the correct yaw of the model. Some model and engine combinations require some down thrust as well as right thrust. This helps with the pitch of the RC model airplane.
Total ready-to-fly weight will also have an effect on the flight characteristics. Once again, I emphasize the importance of strictly following the included instructions.
This post is starting to get too long and involved, so I will stop here and continue with straight and level flight of the RC model airplane in the next post. Until then read this material completely and see if you can come up with some questions on what we have been discussing so far. Remember, you may submit your questions to me by email to firstname.lastname@example.org .
This is the OldManFlier and I will see you next time.