SPORTPLANE BUILDER Tony Bingelis Very few homebuilders know or understand what the term "rig" ("rigging") has to do with airplanes. Most of us do know it is used in reference to things nautical done aboard ships and boats. However, the term is equally applicable to aircraft and the realm of flight. According to my dictionary, when you rig anything, you "construct," "adjust" or "arrange" (it). As a homebuilder you are probably more familiar with your construction manual rigging words like "jigging" and "alignment." Technically speaking, as you assemble your airplane you are, at the same time, also rigging it. Nevertheless, even after you have completed the final assembly, other, smaller, rigging jobs will still have to be completed. PART 1 Rigging Is Not Just For Biplanes Mention rigging an aircraft to most any pilot and he will probably assume you are talking about biplanes and things like the assembly, installation, and adjustment of their landing and flying wires. Could be, but the term "rigging" has broader application than that. All aircraft, not just biplanes, must be rigged properly to fly right... that is, to fly both straight and level... hands off. Let's assume you have just completed the construction of your airplane and are making the final preparations to launch it soon on its first flight. Here is a brief summary of the rigging essentials you have probably had to cope with up to this point. 1. The Structural Checks including: a. The completion of the precise rigging and alignment of each of the aircraft's major fixed structural components (engine, wings, fuselage, landing gear, and tail surfaces) during that long challenging construction phase. b. Verifying the alignment of each of the major components with each other as you assembled them. 2. The Control System Checks including: a. The correct alignment of each movable control surface with the adjacent fixed component (wing, You kit builders may find, to your surprise, that the engine mount furnished is offset a few degrees to the right. This is not a manufacturing error but is intended to reduce the amount of rudder input required - especially at high power settings and low speeds. This drill is rigged to accurately drill the holes for the drag and anti-drag wires in a wood wing... just one of the many alignment challenges which may confront a builder. stabilizer, and vertical fin) to which it is attached. b. Setting and verifying the minimum travel (angular deflection) of each control surface. c. Visually proving to yourself that each of the cockpit controls, which move these surfaces, are properly installed and move the control surfaces in the direction they should move. d. The correct adjustment and safetying of the push-pull tubes, bell cranks, control cables and control stops. SPORT AVIATION 111
After applying careful attention to these rigging essentials you should now have a perfectly rigged airplane at your disposal. What Perfect Rigging Will Get You Although landing gear alignment may not affect the aircraft's in-flight characteristics, wheel misalignment can result in excessive tire wear and skittish runway behavior. Make a ground check of your turn and bank instrument for mounting alignment. Its inclinometer ball should be perfectly centered when the aircraft is leveled laterally. Make a ground check of your turn and bank instrument for mounting alignment. Its inclinometer ball should be perfectly centered when the aircraft is leveled laterally.by standing about 30' in front of an airplane, you can sight along the wing and easily detect a misaligned or warped installation. Apparently, this group attending the fly-in did a fine job of rigging and alignment as they all looked right. A perfectly rigged airplane is in its best aerodynamic configuration and will provide you with the most efficient flight characteristics possible... and it will require the minimum or no additional trim to fly straight and level, hands off, at normal cruise. I can visualize your gleeful reaction after your first couple of flights. "My airplane flew hands off right from the first flight," you say. "How about that? I must have it rigged just right!" Well, that may not be necessarily so, amigo. It is possible for an airplane to be somewhat "out of rig" and still fly hands off. Let's see how that can happen. Even though your wings might be level in flight, the airplane may not be flying (tracking) straight. That is, its nose may be drifting slowly off to the left, or to the right... and yet, there it is flying hands off. If this is so with your airplane, there is apparently a slight rigging problem, a trimming problem... or both. I don't mean to be picky, but I must point out it is not at all uncommon for a first test flight to be proudly declared a "hands off," trouble-free perfect event, when it is only close to it. It is an understandable assumption. However, it is not until after a few more test flights are made that the average builder/pilot is no longer clutching the control stick as hard, and has become a bit more relaxed. So relaxed, in fact, that the euphoria is wearing off and he is becoming more discerning... and, yes, picky. For example, now he may notice that the ball in the turn/bank indicator is skewed off a bit, or that the airplane tends to drift off, ever so slowly into a steepening turn when the control stick is turned loose, or maybe, that the airplane's behavior in some stalls is quite breathtaking because the bird wants to tuck a wing under. After a while, he reluctantly admits to himself that the controls are a bit stiff and, maybe, just maybe, the oil temperature is running kind of low (low?)... and so it goes. I'll admit, there are perfect, gripe- 112 JULY 1994
All aircraft, not just biplanes, must be rigged properly to fly right... that is to fly both straight and level - hands off. free, test flights but most any homebuilt will need a slight adjustment, here and there, to fine tune its performance. Minor rigging and trimming adjustments, therefore, are to be expected. When we refer to an aircraft as being "out-of-rig," we assume its components are not properly aligned due to inaccurate construction, or final assembly. The Not So Perfect Rigging Job The consequence of a serious rigging deficiency is that the total drag of the aircraft will be increased, and its performance will suffer because trim tabs have to be installed. Often, when trim tabs are necessary, they may have to be severely deflected to achieve that elusive hands off condition in flight. There is another concern. In some All Epoxies Are Not Created Equal! PTM&VV Industries introduces AKKOI'OXY. the first epoxy laminating resin lo combine modern non-toxic hardener leclmologx with superior high temperature cured strength. Easy to use. AKKOI'OXY is specially formulated for engine cowlings, wing spars, landing gear legs, and other very high performance applications. Quality Materials For High Performance Composite Parts Manufactured by ITMcUV Industries. Inc. Santa Fc Springs. CA 90670 Call 800-421-1518 SPORT AVIATION 113
Those Final Rigging Checks Do not try to adjust wing incidence and alignment until the aircraft is set in a level attitude. In this airplane (RV-3) the longerons in the cockpit area are used as a level reference. installations, the amount of control travel available may be insufficient to effect the correct response in flight. In other instances, the amount of control travel may be too great, and a sudden deflection of the control surface by the pilot could fail the structure due to the excessive loads (stresses) imposed. It is very important, for this reason, that your airplane be rigged in conformance with the designer's specifications for: angles of incidence, dihedral, wash-in or wash-out, engine thrust line alignment, horizontal tail incidence, the amount of vertical fin offset (if any), and the amount of control travel. Needless to say, your wheels should also be aligned, or you may experience excessive tire wear and, possibly, runway control problems during landing or takeoff. With flaps in an up position, confirm that both flaps are streamlined with the trailing edges of the ailerons. If for any reason you have the flaps rigged slightly up, or down, be sure both are symmetrically adjusted. Let's go back to square one and review some of the last minute rigging checks and adjustments that will help get top performance out of your airplane. Here's what you can do: 1. First, level the airplane laterally and longitudinally. In most homebuilts you can simply lay a long level across the top longerons to level the airplane laterally. Sometimes a level cockpit floor can be used. At any rate, utilize the official leveling point for your aircraft and level it as accurately as you can laterally. Do not attempt to make your final rigging checks until the airplane is in a level attitude. 2. Next perform the following cockpit rigging checks: a. Climb in the airplane. If the lateral level bubble is now slightly off with you in the pilot's seat, have someone let a little air out of the high side tire (remember to reinflate it after you have finished). b. Next, check your turn and bank instrument. Its inclinometer ball should be perfectly centered. Be sure you are looking at the instrument square-on (no parallax error, thank you). If the ball is skewed off to one side, however slightly, loosen the instrument mounting screws and twist the instrument a bit to get the ball perfectly centered. Re-tighten the mounting screws. c. Make the same check for your artificial horizon... if you are so equipped. Note: Most turn and bank instruments and artificial horizons have slightly elongated mounting screw holes which will allow you to twist the instrument slightly to help get the ball centered. If your instrument doesn't have the elongated holes you can elongate the holes in your instrument panel instead with a small round file to accomplish the same thing. However, you had better think twice before you start filing or you might elongate the holes in the wrong direction. No matter how careful you may have been, it is quite possible to have inadvertently mounted one or two instruments in your panel slightly tilted. Naturally, if that happened, it probably happened to the very two instruments that cannot tolerate any lateral deviation. The slightest misalignment of ei- 114 JULY 1994
ther the turn and bank or the artificial horizon can result in a pesky in-flight trim problem. d. Center the control stick and rudder pedals. Verify that the ailerons, rudder, and elevator are streamlined with the fixed surfaces. e. With the flaps in their up positions confirm that both flaps are streamlined with the trailing edges of the ailerons. If you have the flaps rigged so that their up-position is slightly above the trailing edges of the ailerons, be sure both flaps are so, and are symmetrically rigged. e. Lower the flaps, and visually check that both are going down at the same time and to the same degree. If you have a cockpit flap position indicator check it for accuracy. Readjust it if necessary. Do the same for any external flap position indicator. f. Check aileron operation. Move the control stick to the right. The right aileron should move up and the left one down. Move the stick to the left and the left aileron must go up and the right side down. There should be absolutely no During construction, a close check on alignment is essential. The builder here is using two airfoil templates to align his aileron with the wing. binding or rubbing noises throughout the control stick travel. Aileron stops must effectively limit the amount of control stick travel. g. Check elevator travel. Pull back on the stick and visually verify that the external surfaces actually move up. Feel out the elevator stops. UALITY AIRCRAFT FINISHES SPORT AVIATION 115
You should get full stick and control surface travel in both directions. h. Make similar rudder checks. Left rudder pressure must move the rudder to the left. And, as with the other control surfaces, check out the rudder stops. i. Be sure your cockpit adjustable trim control(s) works in the direction you expect it to work, and that you can obtain the desired amount of trim tab travel. There must be absolutely no binding or rubbing noises throughout the limits of the control stick travel and the same for the rudder pedals. Finally, have somebody hold each of the control surfaces while you wiggle and work the control stick and rudder. There should be little or no play in the controls. Excessive play in any of the control surfaces or trim tabs can result in control surface flutter in flight... a frightening experience nobody needs to experience. More next month. Additional reading - "Biplane Assembly and Rigging Procedures," Sport Aviation, February 1988, page 27. ^ r *&, ^^^IH B^^^^^^^^^^^^^ ^^K H^B^v "jl Lt -A^S- ^^8 fc. iflh^e:.» ^M*^ ^Hnf rim ^9 Hi JI ^^^^^K j^^^^k SH^ * 4^^^^^M Li - Jfi^B^H BOOKS BY TONY -Sportplane Builders (Aircraft Construction Methods, ^90 nanpc'i <K1Q <K JirU pdgcaj - ijl7.7j -Firewall Forward (Engine Installation Methods, 304 pages) -$19.95. -Sportplane Construction Techniques (A Builder's Handbook, 350 pages) - $20.95. Add $2.40 postage and handling for each publication ordered... or order all three for $52.97 plus $6.95 postage and handling. Wisconsin residents add 5% sales tax. The following books by Tony Bingelis are available If you wish to contact the from the EAA Aviation author of this column for ad- Foundation, EAA Aviation ditional information, please Center, Box 3086, Oshkosh, send a SASE to: Wl 54903-3086, 1-800/843- Tony Bingelis 3612. Major credit cards 8509 Greenflint Ln. accepted. Austin, TX 78759 MEMUt ttt-ut'tom-hhi'niu NEVER 4 SURCHARGE WORLDWIDE SHIPPING 116 JULY 1994 THE KIT BUILDER'S "PANEL PACKAGE" VFR / P A R T I A L IFR / FULL IFR Call the Experts In Kit Plane Panel Build-Up. m aam 10 Gulf Coast Avionics offers complete panel build-up and prewiring for kit plane builders. With our experience, knowledge, and technical expertise, we can work with you to deliver a built-up panel to your specifications, ready to install. And we can pre-wire for additional equipment that you might want to add later. Call us today for complete details on the "Panel Package". CALL 813-879-9714-FAX 813-875-4514 O4 4243 N. Westshore Blvd Tampo International Airport " OUR F S t^j? Tampa, Florida 33614 USA 83o l FAX - 5:3 p r ^T* Se Hoblo Espoml E.S.T. CORROSION & AIRCRAFT DON'TMIX! Did you know that many over-thecounter cleaning products actually promote corrosion on aluminum surfaces? There's no need to worry anymore. Give your aircraft what it deserves: ZI-400 AIRCRAFT CLEANING COMPOUND! ZI-4 00 has been proven most recently by the Royal Australian Air Force which deemed it the best of the best cleaners for their P-3 Orion ocean patrol aircraft, and chose it for both its cleaning power and its anti-corrosion action. On aircraft ranging from fighters to corporate jets, ZI-400 concentrate continues to be proven as a safe and cost-effective way toclean all common aircraft surf aces ~ exteriors and interiors machine shop tools, bare metals, painted surfaces, ceramics, plastics, composites, glass, vinyl and various fabrics. Try a gallon! Send check or money order for $25.00 including UPS (CA residents add $1.65 sales tax), or call us for more information: Zelman International Limited 1411 5th St.. Suite 303-SA07 Santa Monica. CA 90401-2441 Tel.: (310) 451-SAFE (7233) Fax: [310) 576-6832