Par 1-9 Page 14 SECTION 7. ASSEMBLY AND AIRWORTHINESS INSPECTION “Complacency is one of the major causes of accidents, no matter how well things are going, something can go wrong” Art Scholl
1-9. OBJECTIVE. To determine the airworthiness of the aircraft and its systems.
1-10. GENERAL.
a. If you must reassemble the aircraft after moving it to the airport—take time to do so carefully. This is a critical event because mistakes can easily occur due to the builder’s preoccupation with the impending first flight of the aircraft. One of the most common and deadly mistakes is to reverse the rigging on the ailerons. To prevent errors in reassembling the aircraft, follow the designer’s or kit manufacturer’s instructions, or use a written checklist specifically designed as part of the flight-test plan. At the completion of each major operation, have another expert check the work.
b. After reassembling the aircraft, perform a pre-flight “fitness inspection.” This inspection should be similar to an annual inspection. You should perform the fitness inspection even if the FAA has just issued a special airworthiness certificate for the aircraft. Even if a builder was 99 percent perfect and performed 10,000 tasks building the aircraft, there would still be a hundred items that would need to be found and corrected before the first flight.
1-11. FITNESS INSPECTION—AIRFRAME. A builder-developed comprehensive post assembly checklist should be used, and the results of that inspection should be recorded on the checklist to provide increased assurance that all items of concern have been addressed and the
Par 1-11 Page 15 results documented. The following additional safety checklist items may not be applicable to all amateur-built make and model aircraft, but the FAA presents them here for consideration and review.
a. Control Stick/Wheel. The control stick/wheel should have a free and smooth operation throughout its full range of travel. There should be no binding or contact with the sides of the fuselage, seat, or instrument panel. There should be no free play (slack) in the controls, nor should the controls be tight as to have stick-slip movement.
b. Rudder Pedals. Move the rudder pedals through the full range of travel. The pedal movement should be smooth, and without any binding. The test pilot’s shoes should not catch on exposed metal lines, fixtures, or electrical wire harness.
c. Brakes. Hand and/or toe brake pressure should be firm with no tendency to bleed down or lock up. Spongy brakes that must be “pumped up,” or that show a drop in the brake fluid reservoir level after a few brake applications, indicates a brake fluid or air leak in the system.
d. Main Landing Gear. Ensure that the gear attach points, shimmy damper, bungees, wheels, brakes, and wheel fairings are airworthy. If applicable, check that the tailwheel pivot point is centered and vertical compared to the longitudinal axis of the aircraft. It is critical that the main landing gear alignment toe in/toe out is zero or matches the specifications for fuselage/landing gear alignment called out in the plans. Even one landing gear wheel out of alignment can cause a ground loop.
e. Control Surfaces. Perform rigging checks to ensure that control input for ailerons, rudder, elevators, and trim tabs results in the correct amount of travel and direction of the control movement and that these control surfaces make contact with their stops. Also, ensure that the flaps, if installed, have the proper travel, operate as a single unit, and cannot be extended beyond the maximum extended position. It is important to ensure that the control cable tension is correct by
(1) checking it with a calibrated tensiometer and (2) confirming that all the attachment hardware is secured and turnbuckles are properly safetied.
(1) If the cable tension is less than required by specifications, in-flight air loads will prevent full travel of the control, even if the control has the right amount of deflection and hits all the stops in the cockpit/wing/tail when tested on the ground. With low cable tension, the slack in the cables will absorb the desired control movement input.
(2) While checking cable tension, make sure there is no “free play” in the flight control hinges and rod ends. Free play and loose cable tension combined with control mass imbalance can bring on control surface “flutter.” Do not, however, rig the controls at too high a cable tension. This will cause high wear rate on the pulleys and prevent good control feel, especially at low airspeeds.
f. Instrument Panel.
(1) All the instruments should be properly secured in the panel and have preliminary markings on them. The airspeed indicator and engine tachometer should be marked with the
Par 1-11 Page 16 expected performance range markings. Oil temperature and oil pressure must have the engine manufacturer’s recommended operating range marked. If the markings are on the instrument glass face, paint a white slippage mark on both the glass and on the instrument case to alert the pilot in case the glass/range marks have moved. Attach a temporary placard to the instrument panel with the expected stall, climb, and glide speeds. It is a handy reference in times of emergency.
(2) Angle of attack systems may require in-flight calibration. Information displayed prior to that calibration may not be accurate.
(3) Electronic data collection systems, when installed, must be checked if possible before flight according to the manufacturer’s instructions. Recording of electronic data through flight and engine instruments can be very useful, but only if it is ensured that accurate information is being collected. Therefore, verification of this data prior to flight is important.
g. Behind the Instrument Panel. Very few amateur-built aircraft of the same make and model have the same instrument panel design. Amateur builders should inspect this area to ensure that all line connections are tight, that nothing interferes with control travel, and there are no loose wires or fuel, oil, or hydraulic leaks.
h. Carbon Monoxide (CO). CO leaks also can be performed. Wait until night or put the aircraft in a dark hangar. Climb into the cockpit and have a friend shine a bright flood light close to the firewall. If light leaks into the cockpit, CO can seep in. Mark it and seal it.
i. Engine and Propeller Controls. All controls should be visually inspected, move in the proper direction, and securely mounted. The friction lock on both controls should be checked for operation. Each control should have full movement with at least a ¼-inch of “cushion” at the full travel position. The control cables should be firmly attached to the fuselage along each 24 inches of their runs to prevent whipping of the cable and loss of cable movement at the other end. Control cables with ball sockets should have large area washers on either end of the bolt connection. This will ensure the control will remain connected, even if the ball socket fails and drops out.
j. Static System. The best procedure to check the altimeter for leaks and accuracy is to have the entire static system checked using 14 CFR part 43, appendix E, at an FAA-approved repair station.
1-12. FIELD CHECK. You need two people to accomplish the following field check by which an amateur-builder can detect if the aircraft’s instrument system is leaking:
NOTE: This field check is not an accuracy check. Additionally, you should check the manufacturer’s manuals for the installed pitot-static instruments to ensure that this test method will not damage any associated electronics.
a. Airspeed Check. Slip a long rubber hose over the pitot mast (The FAA recommends surgical tubing). As one person reads the airspeed, the other should very slowly roll up the other end of the tubing. This will apply pressure to the instrument. When the airspeed indicator needle reaches the aircraft’s approximate recommended cruise speed, pinch the hose shut, and hold that
Par 1-12 Page 17 reading. The airspeed needle should remain steady for a minute if the system is sound. A fast drop off will indicate a leak in the instrument, fittings, lines, or the test hose attachment. Never force air in the pitot tube or orally apply suction on a static vent—this action will damage the instruments.
b. Altimeter/Vertical Speed Check.
(1) To check the static side, apply low suction at the end of the static vent port. The easiest way to gain access to the static system is to remove the static line at the static port. If there are two static ports, tape the unused port closed. Next, get two feet of surgical tubing, seal one end, and tightly roll it up. Attach the open end to the static line and slowly unroll the tubing.
This will apply a suction, or low pressure, to the static system.
(2) The altimeter should start to show an increase in altitude. The vertical speed indicator also should indicate a rate of climb. The airspeed may show a small positive indication.
When the altimeter reads about 2,000 feet, stop and pinch off the tube. There will be some initial decrease in altitude and the vertical speed will read zero. The altimeter should then hold the indicated altitude for at least a minute. If altitude is lost, check for leaks.
NOTE: The above airspeed and altimeter field checks are a check of the system for possible leaks, and are not the same as airspeed or static system accuracy tests done by a certificated repair station. The checks do not include the pitot tube and static ports located on the airframe. The FAA recommends the builder not deviate from the designer’s original plans when installing the pitot and static system.
c. Fuel System. Since 1983, more than 70 percent of the engine failures in amateur-built aircraft were caused by fuel system problems. Many times the direct cause of engine failure was dirt and debris in the fuel tank and lines left behind during the manufacturing process.
(1) Before filling the aircraft’s fuel tanks, the amateur-builder should vacuum any manufacturing debris from each tank and wipe them down with a “tack” cloth (available from a paint supply store). Next, the builder should flush the system with aviation grade gasoline several times in order to remove any small or hard to reach debris from the tanks and lines. The builder should also clean the fuel filter/gasolator screen/carburetor finger screen. The amount of time spent “sanitizing” the fuel system will provide big safety benefits for the life of the aircraft.
(2) When filling the tanks, place the aircraft in the straight and level cruise position.
Add fuel in measured amounts to calibrate the fuel tank indicators. While allowing the aircraft to sit for a short time to observe for possible leaks, inspect the fuel tank vents to see if they are open and clear. Check that the fuel tank caps seal properly. If there are no leaks and the fuel system has an electric boost pump, pressurize the system and again check for leaks. The fuel selector, vents, and fuel drains should be properly marked and tested for proper operation.
NOTE: Many amateur-built aircraft take 5 to 8 years to build. During that time, many rubber-based oil and fuel lines and cork gaskets installed early in the building process may have age hardened, cracked, and/or turned brittle.
Par 1-12 Page 18 The builder should carefully inspect these components and replace as necessary to prevent a premature engine failure.
d. Retractable Landing Gear System. If equipped with a retractable landing gear system, whether hydraulic, electrical, or mechanical, the system should function dependably and positively in accordance with the designer’s intent. The builder/pilot should rigorously cycle the retractable landing gear in the appropriate ground setup, using both the normal and emergency landing gear extension system. There should be no hang-ups or binding. If equipped, a function check of the weight on wheel switch and on-board landing gear indicators should also be performed.
e. Safety Belt and Shoulder Harness. You should check these items for condition and proper installation. A review of amateur-built aircraft accidents has disclosed a significant number of accidents in which the seat belt mounting hard points failed. You should check each seat belt and shoulder harness mounting hard point to the designer’s specifications so it will hold the harness and pilot in the aircraft at the ultimate design “G” load specification, both positive and negative, for the aircraft.
f. Avionics and Electrical Checks. Test the avionics systems. Perform an operational check to ensure the radio(s) transmit and receive on all frequencies. Inspect circuit breakers/fuses, microphones, and antennas for security and operation. Test the emergency locator transmitter for proper operation and battery life. Check electrical systems for operation of lights, instruments, and basic navigation/communication performance. You can check other electrical systems, such as generator/alternator output, during engine run-ins, taxi, and flight tests. Check the battery and the battery compartment for security and if applicable, proper venting to the outside of the aircraft. Check the condition of the engine-to-airframe bonding (grounding) wire.
Ensure that all electrical instruments operate properly.
g. Cowling and Panel Checks. Ensure that all inspection panels are in place, the cowling is secured, and cowl flap operation is satisfactory. Inspect the propeller spinner and its backing plate for cracks.
h. Canopy/Door Locks Checks. Ensure the canopy or doors on the aircraft work as intended. Double check the canopy or door lock(s) so the canopy and doors will not open in flight and disturb the airflow over the wings and stall the aircraft. If a canopy jettison system is installed, check for proper operation when the aircraft on the ground and when it is on jacks.
(Jacks will simulate flight loads on the aircraft.)
Par 1-13 Page 19 SECTION 8. WEIGHT AND BALANCE “Never argue with your spouse or a mathematician” Phil Larsh, Accident Prevention Counselor, Colfax IN (1994)
1-13. OBJECTIVE. Discuss the importance of developing accurate weight and balance calculations for both test and recreational flights. You can find additional information on weight and balance in FAA-H-8083-1A, Aircraft Weight and Balance Handbook.
a. Accuracy. A good weight and balance calculation is the keystone of flight testing.
Accurately determining the aircraft’s take-off weight and ensuring that the center of gravity (CG) is within the aircraft’s design for each flight is critical to conducting a safe flight test.
b. Method. An aircraft should be level when weighed, spanwise and fore and aft using the manufacturer’s instructions, and should be in a level flight position. The FAA highly recommends you weigh the aircraft in an enclosed area, using three calibrated scales. The FAA does not recommend bathroom scales because they are not always accurate. Ensure all fuel tanks are empty.
c. A Word about Lateral Balance. Aircraft lateral balance (side to side) is often overlooked, because in most situations it is a matter of loading ballast in the form of cargo or people inside the aircraft that is placed very close to its centerline. The effects on lateral unbalance from difference in ballast weight inside the aircraft are usually minimal.
(1) Aircraft that have fuel in the wings usually have one or more fuel tanks located symmetrical from one wing to the other so lateral balance is not affected. The lateral center of gravity may become important if the fuel load is mismanaged by supplying the engine(s) unevenly from tanks on one side of the aircraft. Care should be taken when fueling the aircraft
Par 1-13 Page 20 evenly so lateral balance is not affected on takeoff unexpectedly. Mismanagement of fuel or uneven fuel loading on aircraft with tip tanks or modified (enlarged or repositioned) fuel tanks can affect the aircraft controllability in all phases of flight.
(2) The airplane is designed so that the primary flight controls (rudder, aileron, and elevator) are streamlined with the non-movable airplane surfaces when the airplane is in a cruising straight-and-level at normal weight and loading configuration. If the airplane is flying out of that basic balanced condition, one or more of the control surfaces is going to have to be held out of its streamlined position by continuous control input. An improperly balanced airplane requires constant control pressures, produces pilot tension and fatigue, distracts the pilot from scanning, and contributes to abrupt and erratic airplane attitude control. The use of inflight adjustable trim tabs and/or autopilot systems can relieve pilot fatigue but can also mask a potential catastrophic controllability problem until it is too late to take corrective action.
(3) Caution should be exercised before undertaking any modification to the aircraft fuel system. Along with fuel flow test, proper fuel line routing, changes in performance in flight maneuvers from changes in the aircraft lateral balance need to be addressed. Phase I flight testing needs to be conducted for any modification that can change the lateral balance of the aircraft.
FIGURE 2. EMPTY WEIGHT CG
ITEMS WEIGH (LBS) ARM (INCHES) MOMENT (IN-LBS) Left Wheel 101 60 6060 Right Wheel 99 60 5940 Tail wheel 42 180 7560 TOTALS 242 80.8 19560 𝑇𝑇𝑇𝑇𝑇 𝑀𝑇𝑀𝑀𝑀𝑇 𝑇𝑇𝑇𝑇𝑇 𝑊𝑀𝑊𝑊𝑊𝑇 = 𝑀𝑀𝐸𝑇𝐸 𝑊𝑀𝑊𝑊𝑊𝑇 𝐶𝑊 OR 19560 242 = 80.8
1-14. DETERMINING EMPTY WEIGHT CG.
a. Sample Aircraft. The sample airplane for determining empty weight is a single seater, with a design empty weight of 253 pounds and a gross weight limit of 500 pounds. The datum line is located at the nose of the aircraft and the CG range is between 69 to 74 inches from the datum.
b. To Work a CG Problem. Figure the empty weight CG first. On a piece of paper, draw four blocks. Title each block from left to right as shown in Figure 3, Takeoff CG.
(1) Under the block titled “Items,” vertically list “left wheel,” “right wheel,” and “nose/tailwheel.”
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(2) Place a calibrated scale under each wheel and record the weight on each gear, in pounds, in the weight block beside the appropriate wheel.
(3) Measure the distance in inches from the datum line, or imaginary point identified by the manufacturer (e.g., nose of the aircraft), to the centerline (C/L) of the three wheels.
Record the distance of each wheel and place it in the “arm” block beside the appropriate wheel See Figure 2, Empty Weight CG.
(4) Multiply the inches (arm) by the weight on each wheel to get the moment (inch-pounds) for each wheel. Add the weight on the three gears and the three moments in inch-pounds and divide the total weight into the total moment. The sum is the “empty weight center of gravity” in inches. In the sample case, the empty weight CG is 80.8.
NOTE: All calculations should be carried out to two decimal places.
FIGURE 3. TAKEOFF CG
ITEMS WEIGHT (LBS) ARM (INCHES) MOMENT (IN-LBS) A/C 242 80.8 19560 Pilot 170 65 11050 Fuel 30 70 2100 TOTALS 442 74 32710 𝑇𝑇𝑇𝑇𝑇 𝑀𝑇𝑀𝑀𝑀𝑇 𝑇𝑇𝑇𝑇𝑇 𝑊𝑀𝑊𝑊𝑊𝑇 = 𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝐶𝑊 OR 32710 442 = 74
1-15. DETERMINING TAKEOFF WEIGHT CG.
a. Since the aircraft’s empty weight and empty weight CG are fixed numbers, the only way an aircraft’s CG can be changed is by adding weight in other locations.
b. For example, in Figure 3, the aircraft’s empty weight has been written in the appropriate blocks. The pilot weighs 170 pounds and fuel—5 gallons—weighs 30 pounds.
c. Again, all measurements are made from the datum to the centerline of the object that has been added. Weight multiplied by inches from the datum equals moment. Add the weights and moments to find the take-off CG for that particular flight.
d. Loaded in this configuration, the aircraft is within the CG flight envelope and is safe to fly.
Par 1-15 Page 22 FIGURE 4. ADDITIONAL EQUIPMENT ADDED
ITEMS WEIGHT (LBS) ARM (INCHES) MOMENT (IN-LBS) A/C 242 80.8 19560 Pilot 170 65 11050 Fuel 30 70 2100 S/B 15 75 1125 Strobe 1.5 179 268.5 Fuel 1.5 55 82.5 TOTALS 460 74.3 34186 𝑇𝑇𝑇𝑇𝑇 𝑀𝑇𝑀𝑀𝑀𝑇 𝑇𝑇𝑇𝑇𝑇 𝑊𝑀𝑊𝑊𝑊𝑇 = 𝑇𝐴𝐴𝑇𝐴𝑇𝐴𝐴𝑇𝐴 𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑊𝑇𝐴𝑊ℎ𝐴 𝐶𝑊 OR 34186 460 = 74.3
1-16. ADDING ADDITIONAL EQUIPMENT.
a. During flight testing, a strobe battery and handheld radio are added. The battery/battery box weight is 15 pounds and the location is 75 inches aft of the datum. The strobe assembly weight is 1.5 pounds and is located 179 inches aft of the datum. The radio’s weight is
1.5 pounds and is located 55 inches aft of the datum. See Figure 4, Additional Equipment Added.
b. In the sample problem, the previous figures for takeoff weight and moment are still accurate, hence those numbers have been listed in the appropriate blocks.
(1) Add the battery, strobe, and radio data in the appropriate locations and calculate the totals. At 465 pounds, the aircraft is still 35 pounds under its design gross weight limit of 500 pounds but is out of balance because the CG has moved 0.3 inches further aft (74.3 inches) than the allowable rear CG limit of 74 inches.
(2) Since the aircraft is out of balance with an aft CG, it is no longer 100 percent stable in pitch and would be dangerous to fly. In most cases, it is not the amount of weight added to the aircraft that can cause a major safety problem but its location.
(3) To bring this aircraft back into the safe CG range, the battery would have to be moved 9 inches forward or 66 inches from the datum line. Another alternative is to install 8 pounds of ballast in the nose, 20 inches from the datum.
(4) If the sample aircraft exceeded the designer’s gross weight limit, such as with a 300-pound pilot instead of the CG limit, its climb, stall, and performance capability would be poor and the possibility for in-flight structural failure would be high.
Par 1-16 Page 23 NOTE: In the sample weight and balance, positive numbers were chosen by placing the datum line on the nose of the aircraft. Some manufacturers prefer to use a datum located somewhere between the aircraft’s nose and the leading edge of the wing.
(5) This kind of datum will set up a system of positive arms, or items located aft of the datum, and negative arms—items located forward of the datum.
(6) When working a weight and balance problem with negative and positive moments, subtract the sum of all negative moments from the sum of all positive moments to reach a “total moment” for the aircraft.
Par 1-17 Page 24 SECTION 9. PAPERWORK “It is harder to write a lie in a logbook than tell one, because your eyes see it and your fingers feel it.” Bob Moorman, Ultralight Instructor (1994)
1-17. OBJECTIVE. Have the proper documentation and paperwork to conduct the flight test.
a. Weight and Balance. The weight and balance for the aircraft should be carefully done. The gross weight and CG range should be determined prior to every flight. An equipment list should be developed and maintained to identify the appliances and articles installed in the aircraft at the time of weighing for certification. It should also be kept current as installed equipment changes from additions or removals.
b. Airworthiness/Registration/Operating Limitations/Placards/Weight and Balance. Must be on board, or the aircraft is not legal for operation.
c. Checklists. In addition to the assembly/airworthiness inspection previously discussed in Chapter 1, Section 7, the builder should prepare the following checklists:
(1) Preflight;
(2) Before starting;
(3) Starting the engine;
(4) Before takeoff;
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(5) Takeoff/cruise;
(6) Descent/before landing;
(7) After landing;
(8) Securing the aircraft; and
(9) Emergency procedures.
NOTE: A checklist to cover the above procedures may seem a tedious task, but it may only be the size of a 5x8-card similar to a checklist for a Cessna 150 or a Piper Cherokee.
NOTE: The amateur builder should anticipate several revisions to the checklists.
d. Flight Manual. It is imperative that a flight manual describing the anticipated performance of the aircraft be written by the aircraft builder/kit manufacturer. The manual will be revised several times during the flight-test phase until it accurately reports the aircraft’s performance, as well as limitations, normal and emergency procedures, and descriptions of those systems installed.
e. Maintenance Records (Logbooks). Operators of amateur-built aircraft must maintain a record of the annual condition inspection in accordance with their operating limitations. The FAA recommends that owners record all inspections and maintenance performed in the aircraft’s logbooks. This will create a history of the aircraft’s maintenance and will be invaluable in spotting trends.