CHAPTER 7 PRE-FLIGHT CHECKLIST

BEFORE GOING TO THE FLYING FIELD

Even though your new model looks complete and seems to be ready to fly, resist the temptation to rush out to the flying field and put it in the air prematurely. There are still several important items you must check out before the airplane is actually ready to fly. Always keep in mind that a model, engine, or radio that is not prepared and working properly on the ground before takeoff will not improve in the air — IT WILL GET WORSE! There is no point in attempting to fly until everything is 100% correct. Using the following pre-flight checklist will greatly improve your chances of success.

( ) CHECK THE BALANCE POINT
Always balance your model with the fuel tank empty. The correct balance point for your airplane should be clearly indicated on the plans or in the kit instructions. Carefully mark the balance point on the bottom of each wing. Pick up the model using only your fingertips at the marks. If properly balanced, the model should stay level after you pick it up.

If the tail hangs down (tail heavy), it means that the model's "center of gravity" is behind the desired balance point and you will have to add weight to the nose. However, before adding new weight, check to see if you can move the battery pack and/or receiver farther forward in the nose of the model. You may be able to make the model balance properly simply by shifting these radio components as far forward as possible. This is the most efficient way of balancing a model, without adding any new weight. If shifting the radio gear forward doesn't work in your installation, then you will have to add new weight. Be sure that any weights are fastened or glued securely, and as far forward as possible for maximum effect. Remember, trying to fly with the C.G. too far back is much more dangerous than the slight increase in wing loading caused by adding weight to the nose. You must make the model balance as per the plans! A tail heavy airplane can be totally unstable and uncontrollable.

If the nose keeps dropping down when you pick up the model at the prescribed balance point, then the model is nose heavy and you must add or shift weight towards the rear of the airplane. Keep in mind that a slightly nose heavy airplane is safer to fly than a tail heavy one, so if anything, err towards the nose heavy side for your first test flights. In general, having the center of gravity ahead of the prescribed balance point will make the airplane more stable, but if carried too far will make it react sluggishly to controls and restrict its aerobatic capability. Your best bet for good flight performance is to balance your model exactly where the designer prescribes.

In addition to the fore-and-aft balancing procedures described above, the performance of an airplane in some aerobatic maneuvers will be improved if it is also balanced "spanwise". For example, if one wing is heavier than the other it can affect stalls and loop tracking. Check the spanwise balance of the complete model assembled with the wing in place. Pick up the model by the engine crankshaft at the front and under the center of the fuselage at the rear. Inset weight (small finishing nails work well) into the lighter wingtip until the model is balanced.

WHY MODELS MUST BE INDIVIDUALLY BALANCED
Every model airplane will turn out a little different. Balsa wood varies in weight and so do model engines. The form of muffler you use, the size and placement of your radio equipment, and the amount of finish you apply can also affect the final balance of the model. Don't feel that whatever C.G. the model builds out to is "good enough". Check carefully and make whatever adjustments are required. If your model is properly balanced it should fly with only minor trim changes.

( ) CHECK FOR PROPER ALIGNMENT
When building a model airplane you should always strive to make it as straight and perfectly aligned as possible. Straight models always fly better! Proper alignment starts with a straight and true building board and continues through every phase of construction. Before taking the new model out for its first flight, take one more look to make sure nothing is drastically askew. Bolt or rubber band the wing in place and view the aircraft from the front and from above, and compare to the drawings shown at right.

( ) CHECK FOR WARPS
A warped or twisted wing panel will make the model constantly want to turn, and a bad warp may make the model snap roll on takeoff or landing approach. Check for warps by sighting the wing from directly behind at a distance of 3-4 feet. Position your eyes so that when you are looking directly at the trailing edge, it appears to be about halfway between the top and bottom wing surfaces. If the trailing edge swoops up or down towards the tip, you probably have a warp that needs correcting (see note about "WINGTIP WASHOUT" for possible exceptions). Also check for warps in tail surfaces by carefully sighting them from a distance.

GENERAL ALIGNMENT DIAGRAM

VIEWED FROM REAR

VIEWED FROM REAR WING THICKNESS EXAGGERATED FOR CLARITY	TRAILING EDGE
GOOD WING PANEL	WARPED WING PANEL
EACH WING PANEL HAS AN EQUAL AMOUNT OF BUILT-IN WASHOUT
Warps can be difficult to see, but it's important to carefully check for them just the same. Check before covering and after because the application of covering material can induce a warp, especially if it is shrunk unevenly. The top wing in this diagram is straight on one side and warped on the other. Obviously, only the warped side needs to be corrected. The lower wing was designed with built-in washout. Since the washout is equal on both sides, no correction is needed.