Par 8-1 Page 87 CHAPTER 8. ULTRALIGHT AIRFRAME INSPECTION “You can learn 10 things by learning one.” Japanese proverb SECTION 1. DIFFERENCES
8-1. OBJECTIVES. To serve as additional resource for ultralight test pilots and to help the new owner develop a flight-test plan for the ultralight.
8-2. DEFINITION. The term “ultralight” means a fixed wing vehicle powered by a conventional 2- or 4-cycle, gasoline-powered engine, and is operated under 14 CFR part 103. It has one seat and does not exceed 254 pounds, excluding floats and safety devices. In addition, the ultralight can be unpowered, in which case the weight is restricted to 155 pounds. The powered ultralight’s fuel capacity can’t be more than five U.S. gallons. The vehicle should not be able to exceed 55 knots calibrated airspeed at full power and level flight and can’t exceed a power-off stall speed of 24 knots calibrated airspeed.
a. Many in the general aviation community view amateur-built and ultralights as one and the same design category, therefore all flight testing procedures should be identical. While in many cases this assumption is true, there are several major differences between the two designs.
(1) Most ultralights are assembled from complete kits, unlike amateur-built aircraft of which the major portion (51 percent) of the aircraft and its component parts are manufactured by the builder. Most of the kit/ultralight manufacturer’s pilot operating handbooks/flight manuals are usually accurate and address the majority of the information covered in the first eight chapters of this AC. The FAA recommends the POH always be consulted by the new owner prior to flight.
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(2) The changes in ultralight ownership are more frequent than amateur-built and general aviation aircraft ownership. Although the ultralight is “used,” the new owner is usually unfamiliar with its operating characteristics. A comprehensive flight testing/training program should be a high priority safety consideration of the new owner.
(3) New flying skills should be developed. Each ultralight pilot/owner should address the effects smaller size, lighter wing-loading, lower weight, and higher drag designs have on low-speed flight.
b. Due to these differences, the FAA recommends that each new ultralight owner design a FLIGHT-TEST PLAN regardless if the ultralight was bought used, and/or the ultralight has a Flight Manual supplied by the manufacturer. The ultralight FLIGHT-TEST PLAN does not have to be as extensive as the one recommended for amateur-built aircraft but should address all flight conditions and emergencies called out in the ultralight’s flight manual.
c. With these differences in mind, the next three chapters will address problems associated with both NEW and USED ultralight flight testing. Chapter 8 will address pre-test flight inspection, Chapter 9 will cover engine and fuel system operation and inspection, and Chapter 10 will cover ultralight flight testing.
d. In keeping with that professional approach towards flight testing, it is suggested that a FLIGHT-TEST PLAN and other relevant safety recommendations found in chapters 1 through 7 be adopted by the ultralight owner/operator prior to test flying a new or used ultralight.
SECTION 2. THE TEST PILOT “There is always a harder way to flight test an aircraft, but that path does not need to be followed. “ George Kaseote, FAA Test Pilot
8-3. GENERAL. Whether the ultralight is brand new or used, you should properly evaluate it.
A new owner should enlist the services of an experienced ultralight flight instructor.
a. The instructor should test fly the ultralight only after it has been properly assembled, inspected, engine run-in, and taxi tests have been performed. It is not recommended that a “new” pilot and a new/used ultralight “learn” to fly together.
b. The test pilot should be experienced and competent. He/she should have made a minimum of 100 solo flights in similar make, model, and type of ultralight and must follow the FLIGHT-TEST PLAN exactly. The FLIGHT-TEST PLAN should examine the ultralight and its performance capability, beginning with the pre-flight inspection and ending only after the test pilot has explored the ultralight’s published flight envelope as described in the flight manual.
Par 8-4 Page 89 SECTION 3. PRE-FLIGHT AIRFRAME INSPECTION
8-4. GENERAL.
a. Ultralight owners should remember that the lightweight, thin wall tubing design of an ultralight fuselage/wing structure is particularly susceptible to metal fatigue. When aluminum tubing has been stressed beyond its elastic limit, it takes on a chalky white appearance (corrosion) at the point of highest stress. Warpage and deformation are other signs of high stress points and once discovered, the ultralight should be grounded until the damaged is repaired.
b. The tolerance limit of a tube or fitting can be significantly lowered by over-torqueing a bolt. If a bent or damaged support tube or structure is not repaired, the bend or dent will become a crack, and ultimately the crack will become a structural failure.
NOTE: If a used ultralight has been purchased, it is highly recommended that the owner perform a detailed acceptance inspection on the aircraft assisted by an experienced individual who is familiar with the make and model aircraft. It is also recommended that all existing hardware (e.g., nuts, bolts, springs) be replaced with new aviation quality hardware.
c. If possible, remove the fabric envelope and check the airframe structure underneath for dents, cracks, and corrosion. Check the top and bottom of the spars for compression (wrinkled metal) damage. Double check all wings, landing gear, strut, engine, and tail surface attach points for wear, elongated holes, or damage.
d. If any previous repairs are found, check with the manufacturer to see if damage in that area can be repaired and if the repair that was made is airworthy.
8-5. CHECKLIST. Each ultralight FLIGHT-TEST PLAN should include a pre-flight inspection CHECKLIST. The CHECKLIST should include a step-by-step approach to inspection that covers all the manufacturer inspection items as well as the following suggested items starting at the landing gear.
a. Landing Gear. The landing gear is the last part of the lightweight aircraft to leave the earth and the first part to arrive. Since the majority of these aircraft fly from unimproved strips, the stress on the gear is high. The checklist should include inspection items recommended by the manufacturer and inspection for the following:
(1) The condition of the landing gear attach points, and alignment of the landing gear and wheels to the longitudinal axis of the fuselage. If the attach points are misaligned, the landing gear will not track in a straight line and this will affect takeoffs and landings.
(2) Elongated bolt holes, loose Army/Navy (AN) hardware, bent tubing, condition and attachment of wheels, wheel bearings, tire inflation, tire condition and brakes.
(3) Brake condition and operation, including chafing of brake lines/cables against the gear struts.
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(4) Condition and operation of the steerable nose gear, if applicable.
(5) Condition and attachment of the tailwheel/skid, if applicable.
b. Wing Assembly. The vast majority of ultralight aircraft use a man-made sailcloth material stretched over a tubular frame. This type of fabric is susceptible to ultra-violet radiation from the sun. If left unprotected, it can become unairworthy in less than 6 months. The checklist should include the following inspection items:
(1) Ensure the sailcloth has not suffered any tears, or abrasion, due to wear or foreign object damage.
(2) Check the sailcloth for obvious ultraviolet (UV) degrading of fabric strength by examining the condition of the fabric on top of the wing. Compare it to the fabric on the bottom of the wing. If the top wing fabric shows a significant difference in color (faded), the fabric should be tested for strength with a fabric tester (Maule or Quicksilver) to see if it tests within the manufacturer’s serviceable limits. If no minimum service limits are listed, the fabric should test out at 46 pounds, or 70 percent or more, of its original tensile strength, whichever is greater, to be considered airworthy. If the fabric fails the tests, it must be replaced before further flight.
(3) Flying and landing support cables should be checked for tension, routing, attach points, and condition. Scrutinize the swaged cable ends. It is recommended that a red reference mark (nail polish works fine) be painted on each of the cables abutting the swaged end. If the cable is growing (i.e., a gap forming between the swaged end and the painted referenced mark), there is an impending failure of the swaged terminal. Do not fly the aircraft until the cable is replaced.
(4) Flight control cables should be checked for frayed wires and proper routing. Run a rag over all of the flying and landing wires and control cables (wings and tail). If the cloth snags, this may indicate a frayed wire which demands further inspection. If possible, bend the cable to form a “U” and inspect for internal broken wires. Also, check the cable pulleys for wear and operation. Extreme wear patterns on pulleys indicate misrouting and must be corrected prior to flight.
(5) Check wing leading/trailing edge, wing struts, aileron, flaps, spoiler hinges and attach points for loose rivets, cracks, elongation, and wear. Ensure that all hardware (nuts and bolts) is of aviation quality.
(6) Ensure that the bungee, or return springs for wing spoilers (if applicable), are serviceable, and will keep the spoiler down flat against the top of the wing when not being deployed.
(7) Check the aircraft’s flight controls rigging every time the aircraft is re-assembled.
It is recommended that the cables/rigging for easier assembly be color-coded (e.g., red to red, blue to blue).
(8) Check for corrosion on all metal surfaces. Corrosion on aluminum usually appears as a white powder, rough to the touch. On steel parts, corrosion takes the common form of rust.
Par 8-5 Page 91 Dissimilar metal corrosion occurs when two different types of metal make surface contact. To obtain additional information on corrosion and treating it, refer to the current edition of AC 43-4, Corrosion Control for Aircraft.
(9) Make sure the leading edge of the wing and tail surfaces are clean and free of insects, grass, or mud prior to flight.
c. Fuselage Assembly. The fuselage is the backbone of the lightweight aircraft. All the flight and ground operating stresses encountered by the wings, tail, landing gear, and engine are transferred to the fuselage at the attach points. Exercise extra care when examining these high stress areas because failure of any of these attach points and associated hardware will cause catastrophic structural failure.
(1) Flight controls should be checked for proper operation, travel, and condition of the stops. There should not be any sharp bends in the flight control cables.
(2) Check engine controls for proper operation; they should be free of bends and properly secured. Ensure that all control cables are securely clamped to the fuselage to prevent the cable from slipping, hence not transferring the desired movement to the engine control.
(3) Check the instrument panel for security and instruments for attachment, proper operation, and range/limit markings.
(4) Inspect for bent or damaged structural tubing. If a tube is bent, it must be properly repaired or replaced. Straightening out a bend will only work-harden the tube in the damaged area and hasten the time of failure.
(5) Fiberglass structures should be checked for cracks, delaminations, and holes— especially on the bottom of the fuselage.
(6) Examine the following for security and condition.
• Seat, seat brackets, and seat belt/shoulder harness;
• Attach points, clips/rings, brackets or tangs and other hardware; and
• Safety fasteners such as cotter pins or safety wire.
(7) Check the shoulder/seat belt harness for condition and proper operation.
(8) Check the ballistic parachute hardware and mounting assembly (review information in Chapter 1, Section 3).
d. Tail Surfaces. The tail, or empennage group, contains two of the ultralight’s three primary control surfaces: the rudder (yaw control) and the elevator (pitch control). In two-axis ultralights, the elevators are the only flight controls on the tail. Special attention must be given to the attach points, hardware, and proper operation for both control systems.
(1) Ensure that the primary controls and trim systems, if applicable, have the proper travel, that control cables are properly tensioned, and that all turnbuckles are safetied.
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(2) Examine the control hinges and attach points on the elevator and rudder horn for wear, cracking, and elongation of bolt holes, and security of the rudder and elevator stops.
(3) Check the leading and trailing edges of the flight controls for damage.
(4) Check for wear/UV deterioration to the fabric cover.
Par 9-1 Page 93 CHAPTER 9. ULTRALIGHT ENGINE/FUEL SYSTEM INSPECTION “Do not let ego overcome reason.” Al Hodges, Ultralight pilot, Homestead, FL (1994)
SECTION 1. ENGINE INSPECTION
9-1. OBJECTIVE. To provide the amateur builder/ultralight pilot with a suggested engine and fuel system inspection program in addition to the manufacturer’s checklist items.
a. Engine.
(1) Check the engine mount, vibration isolation mounts, and attach points before each flight.
NOTE: If slippage marks are painted across the bolt heads, engine mount, and fuselage at the time the mount bolts are torqued, a break in the paint will give advance warning the mount is coming loose. (Again, red nail polish works adequately.)
(2) Check all hose clamps for tightness.
(3) Check for fuel and oil leaks.
(4) Check air filter for condition and attachment
(5) Ensure that all spark plugs are the correct ones, properly torqued. Check that the ignition wires, caps, and plug cap restraints on inverted engines are secured and safetied. Ensure that the kill switch, if applicable, is within easy reach and works as advertised.
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(6) Check that the carburetor and the throttle cable are secured and both operate freely from idle stop to full power stop.
(7) Check carburetor boots for cracks that will suck air and may create a lean mixture, high CHT and EGT, and possible engine failure.
(8) Check the fuel on/off valve, fuel filter, and crossover valve for proper operation and position.
(9) Drain the fuel system of water and sediment.
(10) Ensure that the fuel tank is secured, full, and if applicable, contains the proper mix (ratio) of fuel and oil.
b. Exhaust System.
(1) On most 2-cycle engines, the exhaust system is tuned to the engine in order to have the proper amount of back pressure. Sometimes, due to installation demands, the exhaust system must be modified. If modifications are necessary, contact the engine manufacturer before incorporating any exhaust systems changes.
(2) The exhaust system should be mounted on vibration-damping elements and be safety wired. The exhaust system ball-joints should not be mounted under a tension load and they should be lubricated with an anti-seize, heat resistant grease to allow the ball joints to move freely. Some exhaust systems use springs to keep pressure (compression) on the ball-joints. If the engine is so equipped, run a piece of safety wire through the spring and secure it to the exhaust system. This would prevent a broken spring from coming loose and hitting the propeller in a pusher configuration or hitting the top of the wing or tail in a tractor design.
(3) Another approach to prevent propeller damage from broken springs is to lay a bead of high temperature silicon length-wise across the spring. If a spring does break during flight, the silicon bead will hold some or all of the broken pieces of spring material in place until the aircraft lands.
c. Fan Cooling.
(1) It is particularly important that installations of fan cooled engines with enclosed cowlings are designed so that the hot cooling air exits the cowl and cannot recirculate back into the cooling fan intake. If there are any doubts, tests should be carried out by measuring the temperature of the air entering the cooling fan.
(2) In most cases, it is unlikely there will be a problem with cooling belt tension on a new engine. On older engines, however, the belt may have bedded down in the V of the pulley causing a significant reduction in belt tension. If corrosion is present on a pulley, the belt wear rate will be rapid. During the visual inspection of the fan cooling belt and pulley, look for evidence of wear and corrosion on the pulleys.
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d. Reduction Drive.
(1) A large percentage of engines used on lightweight aircraft are 2-cycle air cooled engines fitted with an rpm reduction drive. The reduction drive is usually a bolt-on unit which drops the high 2-cycle engine rpm down to a propeller rpm that is more efficient.
(2) To check tension on most V belts on the reduction drive, grab the belt and twist.
The belt should allow no more than a half a turn.
(3) Ensure that the reduction gearbox is filled with oil to the proper level in accordance with the manufacturer’s instructions and drain plug/filter is safetied.
(4) Grasp the propeller (switch off and spark plugs disconnected) approximately half way down each blade. Try first to move the prop in an up and down motion. Pull away from the aircraft and then push in the opposite direction. No appreciable bearing slop should be detected in the reduction gear bearings.
(5) Eccentricity of the driving or driven pulley will cause variations of belt tension with rotation, possibly leading to rapid failure of the belt and engine or propeller shaft bearings.
Remove the spark plugs and rotate the engine slowly by hand for several turns in small steps (approximately 45 degrees of engine rotation per step). There should be no noticeable change in belt tension at any position. Any noticeable change must be investigated further (e.g., by measuring the run out of the engine pulley and propeller shaft pulley with a dial indicator).
SECTION 2. FUEL SYSTEMS
9-2. GENERAL. Many problems with lightweight aircraft engines can be directly traced to the type of fuel used. Many states allow automotive fuels to be sold containing 10 percent alcohol without requiring a label stating so. Alcohol can cause serious problems in aircraft engines so first ensure that the fuel source is a reliable one.
a. Test for Alcohol in Automotive Fuel. Take a thin glass jar, mark it one inch from the bottom of the jar with tape or indelible ink, and fill the jar with water up to that mark. Fill the jar to the top with a sample of the fuel to be tested. There is a clear separation between the water and the fuel. Put the lid on the jar and shake. Let it settle for about a minute and check. If the water line is now above the first mark, the fuel has alcohol in it. Try another source for fuel and do another test.
b. Fuel Primer System. Perform a careful inspection of fuel primer bulbs fitted in suction lines because they deteriorate over time and are a possible source of air leaks, resulting in a lean mixture. Primer bulbs with plastic one-way valves have been known to break loose and completely block the fuel in the fuel line. Positioning the fuel line so the fuel flows upward through the primer bulb will help minimize the possibility of this problem occurring. A permanently fitted fuel pressure gage is recommended because it can check fuel system operation during engine break-in and fuel flow during extreme angles of attack.
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c. Filters, Fuel Lines, and Throttles.
(1) Finger screens in fuel tanks should be checked every 10 hours for debris or varnish build up from fuel. Nylon mesh fuel filters are preferred with 2-cycle engines. Paper element filters should be avoided because they may severely and invisibly restrict the fuel flow.
This is due to a reaction between water and oil detergents. The fuel filter should be distinctly located, between the fuel pump and the carburetors, to facilitate pre-flight inspection and avoid the possibility of air leaks on the suction side.
(2) Check plastic fuel lines for age hardness, discoloration, and over all condition.
Fuel line attach points should be checked before each flight. Always clamp a fuel line at the inlet and outlet. A slip-on line might slip off in flight. Leave a little slack in the fuel lines to minimize cracking from vibration.
(3) If the 2-cycle engine has two carburetors, make sure the throttles are exactly synchronized. If not, one carburetor will run rich while the other runs lean, causing cylinder overheating and a possibility of the piston seizing or being holed.
d. Causes of High Fuel Consumption.
(1) Dirty air filter causes a rich mixture.
(2) Propeller is not matched to the engine.
(3) Carburetor float improperly adjusted.
(4) Fuel pressure set too high.
(5) Wrong carburetor jets installed.
(6) Defective float valve.
(7) Extreme vibration (propeller/engine) that keeps float valve open.
Par 10-1 Page 97 CHAPTER 10. ULTRALIGHT TEST FLYING RECOMMENDATIONS “Hurrying is a visible sign of worry.” Arnold H. Glascow
SECTION 1. THREE RECOMMENDATIONS
10-1. OBJECTIVE. To list additional items applicable to ultralights that will need to be addressed in the FLIGHT-TEST PLAN
10-2. RECOMMENDATIONS.
a. Even if the builder/owner or pilot is a B747 airline captain with 20,000 hours in type, the pilot should NOT climb into an ultralight without first receiving flight instruction from a ultralight flight instructor. This sometimes can be done in a two-seat aircraft that is of similar design as the single seat ultralight. The two-seat aircraft will be registered as either special light sport aircraft (SLSA) or an experimental light sport aircraft (ELSA). The ELSA will need a Letter of Deviation Authority (LODA) to be used for flight training. Both SLSA and ELSA will require a properly rated CFI to give the flight training. Ultralights by their very nature are highly susceptible to winds above 15 mph. All ultralight aircraft test flights should be conducted in light or no-wind conditions.
b. Even more so than America’s top fighter pilots, ultralight pilots must manage airspeed. Due to its small speed range between stall and full power; high drag and low weight, airspeed should become the single most important concern of the ultralight pilot.