WEIGHTS FORWARD C.G. LIMIT - REARWARD C.G. LIMIT Weights added anywhere between the C.G. limits will not upset the balance of the aircraft.
-WEIGHT FORWARD C.G. LIMIT -REARWARD C.G. LIMIT Any weights added ahead of the forward C.G. limit would tend to upset the balance around the forward balance limit.
WEIGHT FORWARD C.G. LIMIT •REARWARD C.G. LIMIT Any weights added ait of the rearward C.G. limit would tend to upset the balance around the rearward balance limit.
FIGURE 10-15. Effects of the addition of equipment items on balance.
Moment computations for typical equipment changes are given in figure 10-16 and are also included in the sample weight and balance sheet in figure 10-18.
SAMPLE WEIGHT AND BALANCE REPORT.
Suggested methods of tabulating the various data and computations for determining the c.g., both in the empty weight condition and the fully loaded condition, are given in figures 10-17 and 10-18, respectively, and represent a suggested means of recording this information. The data presented in figure 10-17 have previously been computed in figures 10-10 and 10-11 for the extreme load conditions and figure 10-16 for equipment change, and represents suggested means of recording this information.
INSTALLATION OF BALLAST. Ballast is sometimes permanently installed for c.g.
balance purposes as a result of installation or removal of equipment items and is not used to correct a nose-up or nose-down tendency of an aircraft. It is usually located as far aft or as far forward as possible in order to bring the Par 10-20 Page 10-476
9/8/98
c.g. position within acceptable limits with a minimum of weight increase. Permanent ballast is often lead plate wrapped around and bolted to the fuselage primary structure (e.i., tail-post, longerons, members). Permanent ballast invariably constitutes a concentrated load; therefore, the strength of the local structure and the attachment of the ballast thereto should be investigated for the design loading conditions pertinent to that particular aircraft. Placard permanent ballast with Permanent ballast - do not remove. It is AC 43.13-1B desirable to install permanent ballast by pouring melted lead into the tail-post or longerons due to difficulties that may be encountered in subsequent welding repair operations. It should be noted that the installation of permanent ballast results in an increase of aircraft empty weight. See figure 10-19 for ballast computation. The local strength of the compartment in which the ballast is carried and the effect of the ballast on aircraft weight and balance should be investigated when disposable ballast is carried.
Forward Rearward
- Moments (counterclockwise) + Moments (clockwise) Wheel pants added (+6# at -1") Battery added (+29# at +13") Battery removed (-24# at -29") Landing light removed (-1# at +4") DATUM Weight (#) x Arm (") = Moment ("#) ADDED Item 204 wheel pants + 6 - 1 - 6 Item 302b Battery + 29 + 13 +377
REMOVED Item 302a Battery - 24 -29 +696 Item 303 Landing light - 1 + 4 - 4 This condition is shown properly entered on a sample weight and balance report on Figure 10-18 under Equipment Change.
FIGURE 10-16. Example of moment and weight changes resulting from equipment changes.
MAKE MA-700_MODEL A _SERIAL # 0000_REGISTRATION # N1234 DATUM IS leading edge of wing
COMPUTE AS FOLLOWS IF AIRCRAFT WEIGHED Par 10-22 Page 10-477
Par 10-22 Page 10-478
1. Leveling means: level top longeron between front and rear seats.
2. Main wheel weighing point is located ( “FORWARD) (+ 3 “ AFT) of datum.
3. Actual measured distance from the main weight point centerline to the tail (or nose) point centerline 222 “.
4. Oil over and above “ZERO” tank reading = (a. ---- Gals.) (b. ---- Lbs.) (c. ---- In.)
ACTUAL EMPTY WEIGHT
Weight Point Scale Reading - Tare = Net Weight
5. Right 564 0 564
6. Left 565 0 565
7. Tail 67 27 40
8. Nose ---- ---- -----
9. Total Net Weight X X 1169
CENTER OF GRAVITY AS WEIGHED
10. C.G. relative to main wheel weighing point:
(a) Tail wheel airc. (Item 3, 222) x (Item 7, 40 ) = + 7.6 = C.G.
(Item 9, 1169)
(b) Nose wheel airc. (Item 3 ----) x (Item 8 ---- ) = = C.G.
(Item 9 ---- )
11. C.G. relative to datum:
(a) Tail wheel airc. (Item 10a, + 7.6) added to (Item 2, + 3) = +10.6” = C.G.
(b) Nose wheel airc. (Item 10b, ) added to (Item 2, ) = = C.G.
COMPUTE IF AIRCRAFT WEIGHED WITH OIL (Item 4) Weight x Arm = Moment Aircraft Less Oil
(9) (4b)
(11) (4c)
Empty Totals (a) X (b)
(b) ------------------- = (c) ------------------“ = Empty weight C.G.
12. (a)
REPAIR AGENCY DATE Name Number
FIGURE 10-17. Sample weight and balance report to determine empty weight center of gravity.
Par 10-22 Page 10-479
EQUIPMENT LIST *Required or Optional Item Numbers as Shown in Aircraft Specification 1 2 101 102 103 104 105 106 201 202 203 301 302(a) 303 401(a) 402 ---- ---- ---- ---- ---- Special Equipment Item Make Model Weight Arm 3 Flares 1-1/2 Min. XYZ 03 25# 105”
Enter above those items included in the empty weight.
WEIGHT AND BALANCE EXTREME CONDITIONS Approved fwd limit 8.5” Approved max. weight 2100# Approved aft limit 21.9” Item FORWARD CHECK REARWARD CHECK Weight X Arm = Moment Weight X Arm = Moment Airo. Empty + 1169 (9 or 12a) + 10.6 (11 or 12c) + 12391 + 1169 (9 or 12a) + 10.6 (11 or 12c) + 12391 Oil + 17 - 49 - 833 + 17 - 49 - 833 Pilot + 170 + 16 + 2720 + 170 + 16 + 2720 Fuel + 83 + 22 + 1826 + 240 + 22 + 5280 Passenger (s) + 340 + 48 + 16320 Baggage + 100 + 75.5 + 7550 TOTAL + 1439 = TW x + 16104 = TM + 2036 = TW x +43428=TM TM = 16104 = +11.2” = TM = 43428 = +21.3” = TW 1439 TW 2036 Most Forward C.G. location Most Rearward C.G. location
LOADING SCHEDULE Gallons of Fuel Number of Passengers Pounds of Baggage
40 2(R) 100
The above includes pilot and capacity oil.
EQUIPMENT CHANGE Computing New C.G.
Item, Make, and Model* Weight X Arm Moment Airc. Empty + 1169 (9 or 12a) + 10.6 (11 or 12c) + 12391 204 added + 6 - 1 - 6 302(b) added + 29 + 13 + 377 302(a) removed - 24 + 29 + 696 303 removed - 1 + 4 - 4 NET TOTALS - 1179 = NW x + 13454 = NM NM = 13454 = +11.4” = New C.G.
NW 1179 *ITEM NUMBERS WHEN LISTED IN PERTIN ENT AIRCRAFT SPECIFICATION MAY BE USED IN LIEU OF “ITEM, MAKE, AND MODEL”.
PREPARED BY________________________________ DATE________________________
FIGURE 10-18. Sample weight and balance report including an equipment change for aircraft fully loaded.
→ D< Desired C.G. location Actual C.G. location Location of ballast to D - Distance in inches desired to move C.G. of airplane. be added W - Weight of airplane as loaded.
X - Distance in inches from point where ballast is to be installed, to the desired location of the new C.G.
B - Weight of ballast required in pounds.
B = D× W Compute the new C.G. of the aircraft with ballast installed.
NOTE: If greater accuracy is desired, repeat the entire formula using the NEW aircraft weight and the NEW C.G. in the second operation.
FIGURE 10-19. Permanent ballast computation formula.
Par 10-22 Page 10-480
Par 11-1 Page 11-481 LOADING SCHEDULE. The loading schedule should be kept with the aircraft and form a part of the aircraft flight manual. It includes instructions on the proper load distribution such as filling of fuel and oil tanks, passenger seating, restrictions of passenger movement, and distribution of cargo.
Other means of determining safe loading conditions such as the use of a graphical index and load adjuster are
Par 11-1 Page 11-482 acceptable and may be used in lieu of the information in paragraph 10-18.
Compute a separate loading condition when the aircraft is to be loaded in other than the specified conditions shown in the loading schedule.
10-24.10-34. [RESERVED.]
Par 11-1 Page 11-483 CHAPTER 11. AIRCRAFT ELECTRICAL SYSTEMS
SECTION 1. INSPECTION AND CARE OF ELECTRICAL SYSTEMS
GENERAL. The term “electrical system” as used in this AC means those parts of the aircraft that generate, distribute, and use electrical energy, including their support and attachments. The satisfactory performance of an aircraft is dependent upon the continued reliability of the electrical system. Damaged wiring or equipment in an aircraft, regardless of how minor it may appear to be, cannot be tolerated. Reliability of the system is proportional to the amount of maintenance received and the knowledge of those who perform such maintenance. It is, therefore, important that maintenance be accomplished using the best techniques and practices to minimize the possibility of failure. This chapter is not intended to supersede or replace any government specification or specific manufacturer’s instruction regarding electrical system inspection and repair.
INSPECTION AND OPERATION CHECKS.
Frequently Innspect equipment, electrical assemblies, and wiring installations for damage, general condition, and proper functioning to ensure the continued satisfactory operation of the electrical system.
Adjust, repair, overhaul, and test electrical equipment and systems in accordance with the recommendations and procedures in the aircraft and/or component manufacturer’s maintenance instructions. Replace components of the electrical system that are damaged or defective with identical parts, with aircraft manufacturer’s approved equipment, or its equivalent to the original in operating characteristics, mechanical strength, and environmental specifications. A list of suggested problems to look for and checks (Refer to the glossary for a description of the check types) to be performed are:
Damaged, discolored, or overheated equipment, connections, wiring, and installations.
Excessive heat or discoloration at high current carrying connections.
Misalignment of electrically driven equipment.
Poor electrical bonding (broken, disconnected or corroded bonding strap) and grounding, including evidence of corrosion.
Dirty equipment and connections.
Improper, broken, inadequately supported wiring and conduit, loose connections of terminals, and loose ferrules.
Poor mechanical or cold solder joints.
Condition of circuit breaker and fuses.
Insufficient clearance between exposed current carrying parts and ground or poor insulation of exposed terminals.
Broken or missing safety wire, broken bundle lacing, cotter pins, etc.
Operational check of electrically operated equipment such as motors, inverters, generators, batteries, lights, protective devices, etc.
Ensure that ventilation and cooling air passages are clear and unobstructed.
Par 11-8 Page 11-484 (and 11-4) Voltage check of electrical system with portable precision voltmeter.
Condition of electric lamps.
Missing safety shields on exposed high-voltage terminals (i.e., 115/200V ac).
FUNCTIONAL CHECK OF STAND-BY OR EMERGENCY EQUIPMENT. An aircraft should have functional tests performed at regular intervals as prescribed by the manufacturer.
The inspections or functional check periods should be clearly stated in the aircraft maintenance manual, along with the overhaul intervals.
CLEANING AND PRESERVATION. Annual cleaning of electrical equipment to remove dust, dirt, and grime is recommended. Suitable solvents or fine abrasives that will not score the surface or remove the plating may be used to clean the terminals and mating surfaces if they are corroded or dirty. Only cleaning agents that do not leave any type of residue must be used. Components must be cleaned and preserved in accordance with the aircraft handbooks or manufacturer’s instructions.
Avoid using emery cloth to polish commutators or slip rings because particles may cause shorting and burning. Be sure that protective finishes are not scored or damaged when cleaning. Ensure that metal-to-metal electrically bonded surfaces are treated at the interface with a suitable anti-corrosive conductive coating, and that the joint is sealed around the edges by restoring the original primer and paint finish. Connections that must withstand a highly corrosive environment may be encapsulated with an approved sealant in order to prevent corrosion.
CAUTION: Turn power off before cleaning.
BATTERY ELECTROLYTE CORROSION.
Corrosion found on or near lead-acid batteries can be removed mechanically with a stiff bristle brush and then chemically neutralized with a 10 percent sodium bicarbonate and water solution. For Nickel Cadmium (NiCad) batteries, a 3 percent solution of acetic acid can be used to neutralize the electrolyte. After neutralizing, the battery should be washed with clean water and thoroughly dried.
ADJUSTMENT AND REPAIR. Accomplish adjustments to items of equipment such as regulators, alternators, generators, contactors, control devices, inverters, and relays at a location outside the aircraft, and on a test stand or test bench where all necessary instruments and test equipment are at hand.
Follow the adjustment and repair procedures outlined by the equipment or aircraft manufacturer. Replacement or repair must be accomplished as a part of routine maintenance.
Adjustment of a replacement voltage regulator is likely since there will always be a difference in impedance between the manufacturer’s test equipment and the aircraft’s electrical system.
INSULATION OF ELECTRICAL EQUIPMENT. In some cases, electrical equipment is connected into a heavy current circuit, perhaps as a control device or relay. Such equipment is normally insulated from the mounting structure since grounding the frame of the equipment may result in a serious ground fault in the event of equipment internal failure. Stranded 18 or 20 AWG wire should be used as a grounding strap to avoid shock hazard to equipment and personnel. If the end connection is used for shock hazard, the ground wire must be large enough to carry the highest possible current (0.1 to 0.2 ohms max.).
Par 11-8 Page 11-485 (and 11-4) BUS BARS. Annually check bus bars for general condition, cleanliness, and security of all attachments and terminals. Grease, corrosion, or dirt on any electrical junction may cause the connections to overheat and eventually fail. Bus bars that exhibit corrosion, even in limited amounts, should be disassembled, cleaned and brightened, and reinstalled.
11-9.11-14. [RESERVED.]
Par 11-15 Page 11-486
SECTION 2. STORAGE BATTERIES
GENERAL. Aircraft batteries may be used for many functions, e.g., ground power, emergency power, improving DC bus stability, and fault-clearing. Most small private aircraft use lead-acid batteries. Most commercial and military aircraft use NiCad batteries. However, other types are becoming available such as gel cell and sealed lead-acid batteries. The battery best suited for a particular application will depend on the relative importance of several characteristics, such as weight, cost, volume, service or shelf life, discharge rate, maintenance, and charging rate. Any change of battery type may be considered a major alteration.
Storage batteries are usually identified by the material used for the plates. All battery types possess different characteristics and, therefore, must be maintained in accordance with the manufacturer’s recommendations..
WARNING: It is extremely dangerous to store or service lead-acid and NiCad batteries in the same area.
Introduction of acid electrolytes into alkaline electrolyte will destroy the NiCad and vice-versa.
BATTERY CHARGING. Operation of storage batteries beyond their ambient temperature or charging voltage limits can result in excessive cell temperatures leading to electrolyte boiling, rapid deterioration of the cells, and battery failure. The relationship between maximum charging voltage and the number of cells in the battery is also significant. This will determine (for a given ambient temperature and state of charge) the rate at which energy is absorbed as heat within the battery. For lead-acid batteries, the voltage per cell must not exceed 2.35 volts.
In the case of NiCad batteries, the charging voltage limit varies with design and construction. Values of
1.4 and 1.5 volts per cell are generally used. In all cases, follow the recommendations of the battery manufacturer.
BATTERY FREEZING. Discharged lead-acid batteries exposed to cold temperatures are subject to plate damage due to freezing of the electrolyte. To prevent freezing damage, maintain each cell’s specific gravity at 1.275, or for sealed lead-acid batteries check “open” circuit voltage. (See table 11-1.) NiCad battery electrolyte is not as susceptible to freezing because no appreciable chemical change takes place between the charged and discharged states. However, the electrolyte will freeze at approximately minus 75 °F.
NOTE: Only a load check will determine overall battery condition.
TABLE 11-1. Lead-acid battery electrolyte freezing points.
Specific
Freeze point State of Charge (SOC) for sealed lead-acid batteries at 70° Gravity C. F. SOC 12 volt 24 volt
1.300 -70 -95 100% 12.9 25.8
1.275 -62 -80 75% 12.7 25.4
1.250 -52 -62 50% 12.4 24.8
1.225 -37 -35 25% 12.0 24.0
1.200 -26 -16
1.175 -20 -4
1.150 -15 +5
1.125 -10 +13
1.100 -8 +19
TEMPERATURE CORRECTION. U.S.
manufactured lead-acid batteries are considered fully charged when the specific gravity reading is between 1.275 and 1.300. A 1/3 discharged battery reads about 1.240 and a 2/3 discharged battery will show a specific gravity reading of about 1.200, when tested by a hydrometer and the electrolyte temperature is 80 ºF. However, to determine precise specific gravity readings, a temperature correction (see table 11-2) should be applied to the
Par 11-15 Page 11-487 hydrometer indication. As an example, a hydrometer reading of 1.260 and the temperature of the electrolyte at 40 °F, the corrected specific gravity reading of the electrolyte is 1.244.
TABLE 11-2. Sulfuric acid temperature correction.
Electrolyte Temperature
Points to be subtracted or added to °C °F specific gravity readings 60 55 49 43 38 33 27 23 15 10 5 -2 -7 -13 -18 -23 -28 -35 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 -10 -20 -30 +24 +20 +16 +12 +8 +4 0 -4 -8 -12 -16 -20 -24 -28 -32 -36 -40 -44
BATTERY MAINTENANCE.
Battery inspection and maintenance procedures vary with the type of chemical technology and the type of physical construction. Always follow the battery manufacturer’s approved procedures. Battery performance at any time in a given application will depend upon the battery’s age, state of health, state of charge, and mechanical integrity.
Age. To determine the life and age of the battery, record the install date of the battery on the battery.
During normal battery maintenance, battery age must be documented either in the aircraft maintenance log or in the shop maintenance log.
State of Health. Lead-acid battery state of health may be determined by duration of service interval (in the case of vented batteries), by environmental factors (such as excessive heat or cold), and by observed electrolyte leakage (as evidenced by corrosion of wiring and connectors or accumulation of powdered salts). If the battery needs to be refilled often, with no evidence of external leakage, this may indicate a poor state of the battery, the batte ry charging system, or an over charge condition.
Use a hydrometer to determine the specific gravity of the battery electrolyte, which is the weight of the electrolyte compared to the weight of pure water.
Take care to ensure the electrolyte is returned to the cell from which it was extracted. When a specific gravity difference of 0.050 or more exists between cells of a battery, the battery is approaching the end of its useful life and replacement should be considered.
Electrolyte level may be adjusted by the addition of distilled water.
State of Charge. Battery state of charge will be determined by the cumulative effect of charging and discharging the battery. In a normal electrical charging system the battery’s generator or alternator restores a battery to full charge during a flight of one hour to ninety minutes.
Mechanical Integrity. Proper mechanical integrity involves the absence of any physical damage as well as assurance that hardware is correctly installed and the battery is properly connected. Battery and battery compartment venting system tubes, nipples and attachments, when required, provide a means of avoiding the potential buildup of explosive gases, and should be checked periodically to ensure that they are securely connected and orie nted in accord ance with the maintenance manual’s installation procedures. Always follow procedures approved for the specific aircraft and battery system to ensure that the battery system is capable of delivering specified performance.