U.S. Department of Transportation Federal Aviation Administration Rodney E. Slater, Secretary of Transportation Jane F. Garvey, FAA Administrator Thomas E. McSweeny, Associate Administrator for Regulation and Certification L. Nicholas Lacey, Director, Flight Standards Service Michael L. Henry, Manager, General Aviation and Commercial Division Phyllis Anne Duncan, Editor Louise C. Oertly, Senior Associate Editor H. Dean Chamberlain, Forum Editor A. Mario Toscano, Associate Editor/Designer The FAA's Flight Standards Service, General Aviation and Commercial Division, Publications Branch, AFS-805, Washington, DC 20591; telephone (202) 267-8212, FAX (202) 267-9463; publishes FAA AVIATION NEWS in the interest of flight safety. The magazine promotes aviation safety by calling the attention of airmen to current technical, regulatory, and procedural matters affecting the safe operation of aircraft. Although based on current FAA policy and rule interpretations, all printed material herein is advisory or informational in nature and should not be construed to have regulatory effect. The FAA does not officially endorse any goods, services, materials, or products of manufacturers that may be mentioned. Certain details of accidents described herein may have been altered to protect the privacy of those involved. The Office of Management and Budget has approved the use of funds for the printing of FAA AVIATION NEWS. SUBSCRIPTION SERVICES The Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402-9371, sells FAA AVIATION NEWS on subscription. Use the self-mailer form in the center of this magazine to subscribe. CHANGE OF ADDRESS OR SUBSCRIPTION PROBLEMS Send your label with correspondence to Sup Doc, Attn: Chief, Mail List Branch, Mail Stop: SSOM, Washington, DC 20402-9373. Or call GPO Customer Service at (202) 512-1800/6; FAX: (202) 512-2168. To keep subscription prices down, the Government Printing Office mails subscribers only one renewal notice. You can tell when your subscription ends by checking the date on the second line of your mailing label. To be sure that your service continues without interruption, please return your renewal notice promptly. 19 MedicalStuff: Fiber in Your Diet BACK COVER Editor's Runway ****3-DIGIT 342 FAN SMITH212J JUN96 R 1 423S JOHN SMITH 212 MAIN ST FORESTVILLE MD 20747 http://www faa gov/avr/news/newshome htm A DOT/FAA FLIGHT STANDARDS SAFETY PUBLICATION You should check the push-pull access hole to the wing for bird droppings. If there is even the slightest evidence that a bird was there even a piece of straw-you can almost bet that a nest the size of a two-bedroom condominium is inside the wing. Please make sure no birds have set up housekeeping inside the wing for two major reasons. Obviously, the first reason is nest material may foul the flight control cables and bellcranks, and the second reason is that bird droppings are very acidic and corrosion inside a wing is very difficult to treat. Next check the leading edge and wing tip for damage. Usually leading edges of wings show a little "hangar rash" which is mechanic speak for scrapes, dents, and dings usually found on the very outboard of the wing. While it is important to check for damage and cracks in the hangar rash area, it is even more important to check the rear spar attach point where the wing is attached to the fuselage for severe damage. so? If you think of the wing as a lever, a little movement on one end (e.g. hangar rash area) will multiply the force on the rear spar attach point many times. Check the rear spar area for pulled or loose rivets or creased or bent skin. Take your time, and look carefully. This kind of damage is very, very expensive to repair because of the man-hours involved. How One neat trick I learned as a mechanic is how to check the aileron rigging without jacking and leveling. First of all this trick only works on highor low-wing aircraft without interconnected flight controls, so Ercoupe or Tripacer owners have to do the check the hard way. First open the cockpit door and ensure that the aileron trim is neutral and the flaps are in the up position. Next go to either wing and pinch both the aileron trailing edge and the flap trailing edge together so they are in the cruise configuration. Next look at the control yokes in the cockpit. They should be level with the horizon. Now, look at the aileron on the opposite wing. The aileron trailing edge should be in line with the flap trailing edge. If the control yoke shows more than five degrees of bank or if the opposite aileron is either up or down 3/8 of an inch, the ailerons are out of rig and most likely the cause is the cable tension is less than what it is suppose to be. Wheels, Struts, and Brakes Aircraft wheels are usually the last things to leave the ground and the first to arrive-if every thing works as advertised. First thing to check is the tires' condition. FAA policy states that a tire is unairwor Bad wheel alignment equals bad landings. thy if there is cord showing or if the sidewall is cracked. Remember FAA sets minimum standards. My own personal standard is, if there are cracks or no tread, replace the tire. Why? On a 600 X 6 four-ply tire, when you have no tread you have only 1/4 inch of rubber left between you and a blow out. If you find the tire is worn on one side, the wheel alignment toe in or out is off. This is corrected by adding or subtracting washers to the torque links. However the alignment process takes a couple hours (jacking, leveling, and using a jig) so the labor cost is high to correct the problem. Make sure that the dust cover or hubcap is on the wheel. You see many aircraft without them. However, the owners of these aircraft would be surprised to learn that when the wheel bearing fails because of dirt or water contamination one of two things would happen. First, either the wheel bearing disintegrates and the wheel leaves the axle passing nicely over the retaining nut. Or secondly, the wheel bearing simply seizes and locks up the wheel and takes the airplane and the wide-eyed pilot on a great simulation of Mr. Toad's wild ride. While I am not sure which one would happen first, I am sure both events will be equally memorable. Since you are already down on your hands and knees, take a look at the hydraulic strut. If the strut has a little evidence of rust on it, borrow a 10power magnifying glass and take a look at what is causing that rust. You will find initially the chrome surface was damaged, usually by a stone that cracked the chrome strut plating. On closer inspection you will find the chrome plating is splitting open because the steel strut is rusting and the rust is pushing the chrome plating outwards. Since chrome is very hard, thin, and brittle material the chrome splits and forms thin, very sharp slivers. Each sliver is as sharp as a knife. Depending on how advance the rust is and how hard your next landing is, when the hydraulic strut is fully collapsed those tiny knives will cut the struts quad or "O" ring and the strut will start leaking. Just re-plating a landing gear strut starts around $600, so keep that in mind when you are buying an airplane. Contrary to popular belief, or your last flight instructor's tongue in cheek comment, the nose wheel is not designed to shimmy and soft field takeoffs and landings are not the rule. Nose wheel shimmy is commonly caused by a defective shimmy dampener. It is usually out of fluid. But the shimmy can also be caused by worn or lose torque links or hardware, worn strut bearing inside the main strut housing, or the tire is out of balance. While the many causes of nose wheel shimmy are known, all are expensive to repair. So pay strict attention to any shimmy problems on take off and landing when you do the test flight. Aircraft brakes are a compromise between stopping power and weight, so now you know the answer to the question: "Why are runways so long?" Your standard GA aircraft has steel brake disk and the brake pads are riveted lining. If the disks are pitted, rusted, or grooved, the disks are bad. Next, inspect the brake linings. What is not widely known is that only 60% of a new brake lining is usable. The other 40% makes up the material that the rivets use to hold the entire lining pad in place. Once you wear the lining past the 60% mark, the brass rivet heads get shorn off and the lining falls away instantly turning your brakes into grinding wheels. If the wheel pant is not in the way, one way you can check the thickness of the brake lining is to lay a common paper match on the visible end of the brake lining. If you see more braking lining than match, go fly. No brake lining, more match, brakes are close to the 60% mark. Engine and Propeller Here is another mechanic's trick you can use to impress your friends. You can determine if the engine's hard rubber isolation mounts need to be changed without taking the cowling off. First make sure the paint trim on the fuselage and the engine cowling match up. This match paint check is just to make sure the cowling is on right. Without moving the propeller, measure the distance between the top of the propeller spinner and the cowling. Next measure the distance between the bottom of the spinner and the cowling. If the distance is greater at the top by a 1/4 to 3/8 of an inch compared to the bottom measurement, the engine mounts are sagging inside the cowling. How so? Since the cowling is attached to the fuselage, not to the engine, when the top two engine mounts begin to wear, they stretch, because of the weight of the engine acting on them. At the same time, the bottom two-engine mounts are being compressed, so the engine drops inside the cowling. The amount of sagging is what you are really measuring between the spinner and the cowling. The engine mounts usually last between 500 to 1,000 hours and cost approximately $500 plus labor to replace. After you get the cowling off, I recommend removing one bottom spark plug from each cylinder for safety reasons and mark the cylinder they came from. Next, carefully examine the propeller spinner backing plate for cracks. Dual exhaust pipes should never touch. The spinner plate takes a lot of punishment when pilots push on the spinner in order to back the aircraft into its parking space. Also check the spinner for cracks and repairs. Most manufacturers do not allow spinners to be repaired. Quite frankly, if you ever experienced the noise and accompanying jolt of a spinner leaving the airplane in cruise flight, you would agree with me that a spinner is one of those airplane parts that you replace and never repair. Now we want to check the "track" of the propeller. With one spark plug removed from each cylinder and the aircraft on level ground, place a large wooden block or a tool box that is at least a couple inches higher off the ground than the propeller blade tip. next to the propeller tip so they both just touch. Next rotate the propeller slowly in the direction of rotation. We want to see if the next blade "tracks" through the same point of the arc and touches the block. Both blades should be within 1/16" plus or minus from one another. If the difference is greater that an 1/16" than the blade is out of track. An out of track propeller will cause |