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(v) The routing of the bridle and harness
(vi) The routing of the activating housing
(vii) The placement of the activating handle in the cockpit
(viii) Incorporation of chute deployment procedures in the in-flight emergency plan and emergency check list
(ix) The deployment time, from activation to full chute opening
(3) If a ballistic chute is installed, the builder should add the appropriate ballistic chute inspection items to the aircraft’s pre-flight inspection check list. The builder also should add the ballistic chute manufacturer’s repack/refitting schedule and maintenance inspections to the flight manual and the conditional annual inspection check list.
SECTION 4. TEST PILOT ‘‘We are looking for a few good Men and Women!’’ Marine Corps advertisement (1991)
1. OBJECTIVE. To select a qualified individual to be the test pilot.
2. GENERAL. The test pilot should be competent in an aircraft of similar configuration, size, weight, and performance as the aircraft to be tested.
If the aircraft’s builder is the test pilot, the costs involved in maintaining pilot competence should be budgeted with the same level of commitment and priority that is assigned to plans and materials to complete the project.
3. TEST PILOT REQUIREMENTS.
a. A test pilot should meet the following minimum qualifications:
(1) Physically fit: Test flying an aircraft is a stressful and strenuous task
(2) No alcohol or drugs in the last 24 hours
(3) Rated, current, and competent in the same category and class as the aircraft being tested
(4) Current medical and biennial or flight review as appropriate, or a current USUA certification and flight review
b. Suggested Test Pilot Flight Time Requirements. The following suggested number of flight hours are only an indication of pilot skill, not an indicator of pilot competence. Each test pilot must assess if their level of competence is adequate or if additional flight training is necessary. If an individual determines they are not qualified to flight test an unproven aircraft, someone who is qualified must be found.
(1) 100 hours solo time before flight testing a kit plane or an aircraft built from a time-proven set of plans
(2) 200 hours solo time before flight testing for a ‘‘one of a kind’’ or a high performance aircraft
(3) A minimum of 50 recent takeoffs and landings in a conventional (tail wheel aircraft) if the aircraft to be tested is a tail dragger
c. The test pilot should:
(1) Be familiar with the airport and the emergency fields in the area
(2) Talk with and, if possible, fly with a pilot in the same kind of aircraft to be tested
(3) Take additional instruction in similar type certificated aircraft. For example, if the aircraft to be tested is a tail dragger, a Bellanca Citabria or Super Cub is appropriate for training. For testing an aircraft with a short wing span, the Grumman American Yankee or Globe Swift is suitable for training.
(4) Be considered competent when they have demonstrated a high level of skill in all planned flight test maneuvers in an aircraft with performance characteristics similar to the test aircraft
(5) Study the ground and in-flight emergency procedures developed for the aircraft and practice them in aircraft with similar flight characteristics
(6) Have logged a minimum of 1 hour of training in recovery from unusual attitudes within 45 days of the first test flight
(7) If appropriate, have logged a minimum of 10 tail wheel take-off and landings within the past 30 days
(8) Study the performance characteristics of the aircraft to be tested. Refer to the designer’s or kit manufacturer’s instructions, articles written by builders of the same make and model aircraft, and study actual or video tape demonstrations of the aircraft.
(9) Review the FAA/National Transportation Safety Board (NTSB)/EAA accident reports for the same make and model aircraft to be aware of problems the aircraft has experienced during previous operations (see appendix 2 for the address).
(10) Memorize the cockpit flight controls, switches, valves, and instruments. A thorough knowledge of the cockpit will result in controlled and coordinated mental and physical reactions during emergencies.
NOTE: The EAA has developed a Flight Advisor Program which offers builders/ pilots assistance in performing a self evaluation of the flight test program and/or selection of the test pilot. To obtain additional information, contact a local EAA Chapter or EAA Headquarters, (414) 426-4800.
SECTION 5. MEDICAL FACTS FOR PILOTS ‘‘If the pilot is unairworthy, so is the airplane!’’ Bill Chana, Aeronautical Engineer
1. OBJECTIVE. To identify some of the well known medical causes for aircraft accidents and to stress the importance of a personal pre-flight checklist in addition to an aircraft pre-flight checklist.
a. Alcohol. FAR Part 91, ‘‘General Operating and Flight Rules,’’ § 91.17 requires that 8 hours must elapse from the last drink to the first flight.
Test flying an aircraft, however, places additional mental and physical demands on the pilot. The FAA strongly recommends a minimum of 24 hours between the last drink and the test flight. This is because small amounts of alcohol in the blood stream can affect judgement, reaction time, and decrease a pilot’s tolerance to hypoxia.
b. Anesthetics. Local and dental anesthetic can affect a pilots performance in many adverse ways.
It is recommended that a minimum of 48 hours elapse from the time of anesthesia to the time the pilot climbs into the cockpit.
c. Blood Donations. Do not fly for 3 weeks after donating blood. The body needs approximately three weeks for a complete physiological recovery.
Although the physical affects may not be noticeable at sea level, they will become apparent when flying at higher altitudes.
d. Carbon Monoxide (CO). CO is a colorless, odorless, tasteless gas that is always present in engine exhaust fumes. Carbon monoxide prevents oxygen absorption by the blood, and exposure to the gas creates vision problems, headaches, disorientation, and blurred thinking (see chapter 1, section 7, paragraph 3 (g) for testing the aircraft for CO contamination).
e. Drugs. Similar to alcohol, drugs will reduce or impair judgement and affect reflexes and hand/ eye coordination. It is a given that the use/abuse of illegal drugs is dangerous and against the law.
Prescription drugs and over-the-counter remedies, however, also may be dangerous when combined with flying. The FAA recommends all pilots who must take medication consult with an Aviation Medical Examiner (AME) to understand the medication’s affects on their ability to think and react while in the cockpit.
f. Ear and Sinus Pain.
(1) Ear and sinus pain is usually caused by the eardrum or sinuses failing to equalize the air pressure during a descent. The blocked ears and sinuses can be caused by a head cold. The pain can be considerable and is most noticeable during
8 5/24/95AC 90-89A descents. For ear blockages try yawning, swallowing, or chewing gum which may give some relief. The Valsalva procedure can be effective: pinch the nose, close the mouth, and try to force air through the nostrils.
(2) If ear blockage occurs during flight, try climbing back to a higher altitude (lower air pressure) until the pain lessens. Then begin a gradual rate of descent, allowing the ears and sinuses time to adapt to the increasing pressure.
(3) After landing, nasal sprays will give some sinus pain relief. To relieve ear pain, try wetting paper towels with hot water, put the towels in the bottom of a plastic or dixie cup and then hold the cups over the ears. The warmth will help ease the inflamed tissues and reduce the pain. If pain continues, see a doctor.
NOTE: The best way to avoid this problem is not to fly with a head cold, upper respiratory infection, or nasal allergic condition. Be advised that some nasal and oral decongestants could be ineffective at altitude and have side effects such as drowsiness that can significantly impair pilot performance.
Again, consult with an Aviation Medical Examiner to understand the affects of medication before flying.
g. Fatigue. Fly only when healthy, fit, and alert. Mental and physical fatigue will generally slow down a pilot’s reaction time, affect decision making, and attention span. Lack of sleep is the most common cause of fatigue, but family and business problems can create mental fatigue which can have the same effects on the pilot as lack of sleep.
h. Flicker Vertigo. Light, when flashing at a frequency between 4 to 29 cycles per second, can cause a dangerous physiological condition in some people called flicker vertigo. These conditions range from nausea and dizziness to unconsciousness, or even reactions similar to an epileptic fit. When heading into the sun, a propeller cutting the light may produce this flashing effect. Avoid flicker vertigo, especially when the engine is throttled back for landing. To alleviate this when the propeller is causing the problem, frequently change engine revolutions per minute (rpm). When flying at night and the rotating beacon is creating flicker vertigo, turn it off.
i. Underwater Diving. Never fly immediately after SCUBA diving. Always allow 24 hours to elapse before flying as a pilot or a passenger in order to give the body sufficient time to rid itself of excessive nitrogen absorbed during diving.
j. Stress. Stress from the pressures of a job and everyday living can impair a pilot’s performance, often in subtle ways. A test pilot may further increase the stress level by setting unreasonable test flying schedules in order to meet an arbitrary ‘‘be done by date.’’ Stress also may impair judgement, inducing the pilot to take unwarranted risks, such as flying into deteriorating weather conditions or flying when fatigued to meet a self imposed deadline.
9 SECTION 6. TRANSPORTING THE AIRCRAFT TO THE AIRPORT ‘‘Best laid plans of mice and men are often stuck in traffic.’’ Ben Owen, EAA Executive Director (1994)
1. OBJECTIVE. To reduce damaging the aircraft in transit. The following suggestions may prevent this from happening:
a. Use a truck or flat bed truck/trailer large enough to accommodate the aircraft and the additional support equipment.
b. If the aircraft wings are removable , build padded jigs, cradles, or fixtures to hold and support them during the trip to the airport.
c. Secure the fixtures to the truck/trailer , then secure the wings to the fixture.
d. Use two or more ropes at each tie down point.
e. Use heavy moving pads used for household moves to protect wings and fuselage. Most rent-atruck firms offer them for rental.
f. During the planning stage, obtain applicable permits and follow the local ordinances for transporting an oversized load. Ask the local police if they can provide an escort to the airport.
g. Brief the moving crew thoroughly before loading and unloading the aircraft.
h. Ensure the designated driver has recent experience driving a truck/trailer and is familiar with the roads to the airport.
10 5/24/95AC 90-89A 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. OBJECTIVE. To determine the airworthiness of the aircraft and its systems.
2. GENERAL.
a. If the aircraft must be reassembled after being moved to the airport -- take time to do so carefully. This is a critical event because mistakes can easily be made 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 check list specifically designed as part of the FLIGHT TEST PLAN. At the completion of each major operation, have another expert check the work.
b. When the aircraft is reassembled, perform a pre-flight ‘‘fitness inspection.’’ This inspection should be similar in scope and detail to an annual inspection. The fitness inspection should be accomplished even if the aircraft has just been issued a special airworthiness certificate by the FAA. 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.
3. FITNESS INSPECTION - AIRFRAME.
The following additional safety check list items may not be applicable to all amateur-built make and model aircraft, but are presented 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 freeplay (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 with no binding. The test pilot should ensure that their shoes will 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 show a drop in the level of brake fluid in the reservoir after a few brake applications, indicate a brake fluid or air leak in the system.
d. Main landing gear: Ensure that the gear attach points, shimmy dampener, bungees, wheels, brakes, and wheel fairings are airworthy. If applicable, check that the tail wheel pivot point is centered and vertical in relation 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 contact with the stops is made. 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 checking it with a calibrated tensiometer and confirming that all the attachment hardware is secured and safetywired.
(1) If the cable tension is less than the specifications require, the ‘‘in flight’’ air loads during flight 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 desired control movement input will be absorbed by the slack in the cables.
(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 sets the stage for the onset of 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: All the instruments should be properly secured in the panel and have preliminary markings on them. Airspeed indicator and engine tachometer should be marked with the 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.
g. Behind the instrument panel: Very few amateur-built aircraft of the same make and model have the same instrument panel design. Each amateur-builder 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: Carbon Monoxide 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 fire-wall. If light leaks into the cockpit, carbon monoxide can seep in. Mark it and seal it.
i. Engine and propeller controls: All controls should be visually inspected, positive in operation, and securely mounted. The friction lock on both controls should be checked for operation. Each control should have full movement with at least a 1⁄4 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 in accordance with FAR Part 43, appendix E, at an FAA-approved repair station.
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4. FIELD CHECK. Two people are needed to accomplish the following field check that will enable an amateur-builder to detect if the aircraft’s instrument system is leaking: (Note: This field check is not an accuracy check.)
a. Airspeed check: Slip a long rubber hose over the pitot mast (surgical tubing is recommended).
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 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 will cause damage to 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 approximately 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.
(3) IMPORTANT: The above airspeed and altimeter field checks should not be considered the equivalent of airspeed or static system accuracy tests as certified by a certificated repair station, but a check of the system for possible leaks. These checks do not take into consideration 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 the aircraft’s fuel tanks are filled, 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 system should be flushed with aviation grade gasoline several times in order to remove any small or hard to reach debris from the tanks and lines. The fuel filter/gasolator screen/carburetor finger screen should also be cleaned. The amount of time spent ‘‘sanitizing’’ the fuel system will provide big safety dividends 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 that were installed early in the building process may have age hardened, cracked, and/or turned brittle. The builder should carefully inspect these components and replace as necessary to prevent a premature engine failure.
d. Hydraulic system: The hydraulic system should function dependably and positively in accordance with the designer’s intent. Retractable landing gear should be rigorously cycled on the ground, using both the normal and emergency landing gear extension system.
e. Safety belt and shoulder harness: These items should be checked 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
13 failed. Each seat belt and shoulder harness mounting hard point should be built to the designer’s specifications to ensure that 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 ELT for proper operation and battery life. Electrical systems can be checked for operation of lights, instruments, and basic nav/comm performance.
Other electrical systems, such as generator/alternator output can be checked during the engine run-ins, taxi, and flight tests. Check the battery and the battery compartment for security and if applicable, ensure that the battery is properly vented 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 advertised. 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.)
14 5/24/95AC 90-89A SECTION 8. WEIGHT AND BALANCE ‘‘Never argue with your spouse or a mathematician’’ Phil Larsh, Accident Prevention Counselor, Colfax IN (1994)
1. OBJECTIVE. To discuss the importance of developing an accurate weight and balance calculations for both test and recreational flights. Additional information on weight and balance can be found in AC 91-23A, Pilot’s Weight and Balance Handbook.
a. 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. An aircraft should be level when weighed, spanwise and fore and aft in accordance with the manufacturer’s instructions, and should be in the level flight position. It is highly recommended that the weighing be done in an enclosed area, using three calibrated scales. Bathroom scales are not recommended because they are not always accurate.
ITEMS WEIGHT (LBS) ARM (INCHES) MOMENT (IN-LBS) Left Wheel Right Wheel Tail Wheel TOTALS 101 99 42 242 60 60 180
80.8 6060 5940 7560 19560 TOTAL MOMENT = Empty weight CG or 19560 = 80.8 TOTAL WEIGHT 242 FIGURE 2. EMPTY WEIGHT CG
2. DETERMINING EMPTY WEIGHT CG.
a. The sample airplane for determining empty weight is a single seater, which the kit manufacturer’s 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.
(1) Under the block titled item, vertically list ‘‘left wheel,’’ ‘‘right wheel,’’ and ‘‘nose/tail wheel.’’
(2) Place a calibrated scale under each wheel and record the weight on each gear, in pounds, in the weight block along side the appropriate wheel.
This process is done with an empty fuel tank.
(3) Measure in inches the distance from the datum line, or imaginary point identified by the manufacturer (e.g., nose of the aircraft), to the center line (C/L) of the three wheels. Record the distance of each wheel and place it in the moment arm block beside the appropriate wheel (see figure 2).
(4) Multiply the number of inches (arm) by the weight on each wheel to get the moment (inchpounds) 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.
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ITEMS WEIGHT (LBS) ARM (INCHES) MOMENT (IN-LBS) A/C Pilot Fuel TOTALS 242 170 30 442
80.8 65 70 74 19560 11050 2100 32710 TOTAL MOMENT = Takeoff CG or 32710 = 74 TOTAL WEIGHT 442 FIGURE 3. TAKE-OFF CG
3. DETERMINING TAKE-OFF 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 center line 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.
ITEMS WEIGHT (LBS) ARM (INCHES) MOMENT (IN-LBS) A/C S/B Pilot Strobe Fuel Fuel TOTALS 242 15 170
1.5 30
1.5 460
80.8 75 65 179 70 55
74.3 19560 1125 11050
268.5 2100
82.5 34186 TOTAL MOMENT = Alteration Takeoff Weight CG or 34186 = 74.3 TOTAL WEIGHT 460 FIGURE 4. ADDITIONAL EQUIPMENT ADDED
4. ADDING ADDITIONAL EQUIPMENT.
a. During flight testing, a strobe battery and hand held 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).
b. In the sample problem, the previous figures for take-off weight and moment are still accurate, hence those numbers have been listed in the appropriate blocks.
(1) Add the battery, strobe, and radio numbers 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 .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 (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 (e.g., 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.
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 (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.