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CHAPTER 8 - WEIGHT AND BALANCE

CONTENTS - MAINTENANCE PROCEDURES

Paragraph Chapter/Section Page Number Title Number Number





WEIGHT AND BALANCE

8-1. Purpose ............................................................................ 8-00-00 38-2. General ............................................................................. 8-00-00 38-3. Terminology...................................................................... 8-00-00 3

LEVELING

8-4. Leveling with the use of a Plumb Bob .............................. 8-00-00 58-5. Weighing Procedure ......................................................... 8-00-00 58-6. Preparation Of The Helicopter For Weighing.................... 8-00-00 58-7. Weighing........................................................................... 8-00-00 58-8. Calculations ...................................................................... 8-00-00 78-9. Calculating As-weighed Center of Gravity ........................ 8-00-00 78-10. Calculating Initial Weight Empty and Center of Gravity .... 8-00-00 78-11. Computing an Actual Weight Record — Examples ......... 8-00-00 88-12. Calculating Final Weight Empty Center of Gravity............ 8-00-00 88-13. Use of the weight empty center of gravity limits ............... 8-00-00 88-14. Use of the gross weight flight limits .................................. 8-00-00 148-15. Sample Weighing Procedure............................................ 8-00-00 248-16. Calculating the Lateral Center of Gravity.......................... 8-00-00 248-17. Installation of Ballast......................................................... 8-00-00 248-18. Model 407 Kit Weights...................................................... 8-00-00 28

FIGURES

Figure Page Number Title Number

8-1. Leveling ...................................................................................................... 68-2. Calculating as-weighed center of gravity (Example.................................... 108-3. Weight and balance station diagram .......................................................... 128-4. How to find the correct ballast weight ......................................................... 158-5. Weight empty vs center of gravity .............................................................. 168-6. Gross weight longitudinal center of gravity limits - Standard units ............. 188-7. Completing an actual weight record - Standard units (Example)................ 208-8. Completing an actual weight record - Metric units (Example) .................... 218-9. Ballast installation....................................................................................... 228-10. Actual weight record — Standard unit ........................................................ 268-11. Actual weight record — Metric units ........................................................... 278-12. Actual weight record ................................................................................... 35

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TABLES

Table Page Number Title Number

8-1. Sample weighing using electronic platform scales ..................................... 88-2. Weights for various fuels and oils ............................................................... 98-3. Deriving initial weight empty and center of gravity (example) .................... 118-4. Ballast locations.......................................................................................... 138-5. Deriving final weight empty from initial weight empty (example) ................ 148-6. Sample weighing procedure ....................................................................... 258-7. Kit weights (Standard units)........................................................................ 298-8. Bell 407 with standard skid gear (Standard units) ..................................... 318-9. Kit weights (Metric units) ............................................................................ 328-10. Bell 407 on standard gear .......................................................................... 34

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8-1. PURPOSE

This section gives the procedures that are necessary to find the actual weight empty and the center of gravity (CG) of a helicopter configuration, and to find what changes, if any, are necessary to keep the helicopter within the gross weight flight limits during operation.

8-2. GENERAL

The CG is the balance point of a body and it is used when you calculate the weight and balance for the helicopter. If we compare a helicopter with a pendulum, the suspension point is where the main rotor hub intersects the mast and the pendulum weight is the helicopter. The pendulum weight will stop with its CG directly below the suspension point. For example: a helicopter will fly with its nose up if the CG is aft of the hub/mast intersection. To fly the helicopter in a level manner, the pilot must move the cyclic control stick forward. The more the pilot moves the cyclic control stick forward, the less power there will be for forward speed and the control over the helicopter is decreased. Because this loss of control is unsafe, it is important to keep the helicopter CG within the given gross weight flight limits. This is done in two ways:

1. By changing the location of the helicopter weight empty CG through equipment relocation or by adding or removing ballast, and

2. By deriving the combinations of useful load items which are permitted for each flight.

8-3. TERMINOLOGY

If it is necessary to apply weight and balance control, use the terms that follow:

Weight Empty - the value you get when you add up the weight of the airframe, the power plant, the required equipment, serviceable and special equipment, the fixed ballast, hydraulic fluid, transmission and gearbox oil, fuel that is not usable, and engine oil that is not drainable.

Maximum Gross Weight - the maximum approved take-off weight of the helicopter plus its contents.

Useful Load - the maximum gross weight minus the weight empty. The maximum gross weight includes the pilot, the passengers, the engine oil, fuel, baggage, and cargo.

Center of Gravity (CG) - the point about which all of the moments in all of the axes are exactly equal in magnitude. For balance purposes, think of the weight of an item as being concentrated at the CG of the item.

Weight Empty CG - The center of gravity of the helicopter in it's weight empty condition.

NOTE

When the gross weight flight limits taper, increasing weight empty can cause a previous payload configuration that had been inside limits to have a center of gravity outside limits.

Most Forward Gross Weight - the sum of the empty weight, the maximum crew weight, the engine oil, and all of the useful load items which result in the most forward CG.

Most Aft Gross Weight - the sum of the empty weight, the minimum crew weight, the engine oil, and all of the useful load items which result in the most aft CG.

Weight Empty CG Limits - a range of weight empty CG based on the standard fuel and passenger loading. A helicopter that is ballasted within this range will not go outside the gross weight flight limits with standard loading.

Gross Weight Flight Limits - the center of gravity range plotted against gross weight within which the helicopter meets the requirements of the Federal Aviation Regulations under which it is certified.

Datum - the intersection of the vertical, lateral, and the horizontal planes from which all measurements are taken for balance purposes. The distance to the CG of an item is measured from the datum in terms of Fuselage Station (FS), Buttline (BL) and Waterline (WL) (Figure 8-6).

WEIGHT AND BALANCE

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Arm - the distance from the datum to the CG of an item. The longitudinal arm is the fuselage station, the lateral arm is the buttline, and the vertical arm is the waterline. The algebraic sign convention is plus (+) for an object that is aft of the datum, above the datum, and to the right of the datum (when looking forward). The minus sign (-) is used when parts are forward of the datum, below the datum and to the left of the datum when looking forward.

Moment - the result when you multiply the weight of an item and the arm of the item.

Unusable Fuel - whichever is the greater: the amount of fuel remaining in the system when, in the worst attitude in which flight is maintained, the fuel pump cavitates, or when the fuel gage reads zero.

Minimum Fuel - for weight and balance purposes, this is the same as unusable fuel.

Undrainable Fuel/Oil - the fuel and oil remaining in their respective system after the draining procedures are completed.

Tare Weight - for mechanical scales, the weight of chocks, blocks, stands, etc. that are used during weighing. This weight is included in the scale readings. For electronic scales, consult the scale manufacturer's data.

As-Weighed Weight - the weight of the helicopter configuration on the scales. This should be as close to weight empty as possible.

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8-4. LEVELING WITH THE USE OF A PLUMB BOB

A level plate (4, Figure 8-1) is located in the baggage bay at Fuselage Station 170.10 and Buttline -8.40. A slotted level plate (1) is located directly above the level plate (4) on the underside of the engine pan. To level the helicopter, do the steps that follow:

1. Remove the access panel in the baggage bay roof.

2. Hang a plumb bob (6, Detail A) from the small hole in the slotted level plate (1). Hang it in such a manner that the plumb bob (6) is just above the level plate (4) in the baggage bay.

CAUTION

MAKE SURE THE HELICOPTER IS ON A HARD AND LEVEL SURFACE BEFORE YOU PUT IT ON THE JACKS. IF YOU DO NOT DO THIS, THE HELICOPTER CAN FALL ON ITS SIDE AND DAMAGE CAN OCCUR.

3. Put the helicopter on a hard and level surface in an enclosed hangar.

4. Put three jacks (3) under the helicopter at the permanent jack and tie down fittings. The two forward jack fittings (5) are located at Fuselage Station 55.16 and the aft fitting (2) is located at Fuselage Station 204.92 (Chapter 7). If you have not completed the steps 1 and 2 above, do them now.

5. Adjust the aft jack (3) at the aft jack fitting (2) until the helicopter is almost level.

NOTE

When you make the helicopter level for the weight check, the landing gear skids must be clear of the floor.

6. Adjust all three jacks (3) evenly until the helicopter is level. The helicopter is level when the

point of the plumb bob (6) is directly over the intersection of the cross on the level plate (4).

8-5. WEIGHING PROCEDURE

8-6. PREPARATION OF THE HELICOPTER FOR WEIGHING

Before you weigh the helicopter, make sure that the configuration is as near the weight empty as possible. Do the steps that follow:

1. Remove, as much as possible, dirt, grease, moisture, and any equipment that is not required for weighing from the helicopter.

2. Make sure that the baggage compartment is empty.

3. Put all of the kits and the required equipment for weighing in their proper locations.

4. Make sure that the transmission, gearbox, and hydraulic reservoirs are full (Chapter 12).

5. Make sure the engine oil system is either fully drained or topped up to the full mark.

NOTE

The weight empty configuration is the weight of the basic helicopter plus the weight of the kits, special equipment, fixed ballast, transmission and gearbox oil, hydraulic fluid, unusable fuel, and undrainable oil.

6. Drain the fuel system (Chapter 12).

8-7. WEIGHING

1. Do not weigh the helicopter outdoors or in an open building because wind, flapping rotors, and body sway may seriously affect the accuracy of the scale readings.

LEVELING

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Figure 8-1. Leveling

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NOTE

If you use electronic platform scales, always align the jackpoint on the center of the scale. Do not cross the scale coax wire on the ground or put any weight on the cable.

2. If you use electronic loadcells, make sure that the loadcells and the adapters are tightened to the pads of the jacks that are used to raise the helicopter. Put the load cells in position on the jacks. Do the warm-up recommended by the scale manufacturer. Refer to the instructions supplied by the manufacturer and adjust each load cell to zero.

3. Make sure that each of the scale calibrations have a zero reading before you do each weighing procedure.

4. If you will weigh the helicopter on portable scales, put the scales in position on level ground. Put a scale under each jack point. Align the jackpoint on the center of the scale. Use the jacks to make the helicopter level in the longitudinal and lateral directions (Paragraph 8-4).

CAUTION

MAKE SURE THAT THE LANDING GEAR SKIDS DO NOT TOUCH THE WEIGH SCALES OR THE FLOOR. IF THEY TOUCH, THE SCALES WILL NOT BE BALANCED CORRECTLY.

5. Balance each scale and make a note of the readings. If you are using electronic scales, find the weight on each cell from the digital counter. Refer to the instructions given by the manufacturer.

6. Remove the helicopter from the jacks (Chapter 7). On each scale, weigh the weight tare. This includes the applicable jack, blocks, and any other equipment that you had in position between the helicopter and the scale. Subtract this weight tare from the first scale reading to get the net weights.

7. If you use electronic scales, remove the helicopter from the jacks (Chapter 7). Make sure that the load cells do not touch the jack points. Examine

each digital counter to find the difference from zero. Subtract these numbers from the first scale readings (when you subtract a negative number, you add it) to get the three net weights.

8. Add the individual weights to get the “As-Weighed” Weight. Refer to Table 8-1.

In some cases, tare weight can be negative after removing weight from electronic scales. This example shows this situation.

8-8. CALCULATIONS

8-9. CALCULATING AS-WEIGHED CENTER OF GRAVITY

1. The distance from Fuselage Station 0.00 to the centers of the forward jack fittings (5, Figure 8-1) is called the forward arm, A. (Figure 8-3). The distance from Fuselage Station 0.00 to the center of the aft jack fitting (2, Figure 8-1) is called the aft arm, B (Figure 8-3). The forward arm is 55.16 inches (1401 mm) long and the aft arm is 204.92 inches (5205 mm) long.

2. Multiply the sum of the net weights of the forward scales by the forward arm. The result is called the forward moment and the units are in inch-pounds (millimeter-kilograms).

3. Multiply the net weight of the aft scale by the aft arm. The result is called the aft moment and the units are in inch-pounds (millimeter-kilograms).

4. Add the forward and the aft moments. Divide this sum by the As-Weighed Weight. The result is the As-weighed helicopter CG in inches (millimeters) aft of FS 0.00. Refer to Figure 8-2

8-10. CALCULATING INITIAL WEIGHT EMPTY AND CENTER OF GRAVITY

1. Before you find the ballast requirements, you must compute the initial weight empty from the As- weighed weight. Balance calculations are based on the Weight Empty condition. Start with the As-Weighted weight, the CG, the moment, and do the steps that follow:

a. Add the weight of all the Empty Weight items that are not on the helicopter when it was weighed. Some examples are:

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• unusable fuel,• undrainable engine oil,• transmission oil, and• gearbox oils.

b. Subtract the weight of all of the non Weight Empty items on the helicopter when it was weighed, such as: the plumb bob, the engine oil, the undrainable fuel, etc.

2. Table 8-2 lists the density weights and quantities that must be used for weight and balance calculations. The fuel quantities are for a standard day. If a helicopter has to be weighed with full tanks (this is not recommended), do a specific gravity check to find the correct weight of fuel on board.

3. Table 8-3 shows a typical calculation for deriving the initial weight empty and the CG.

8-11. COMPUTING AN ACTUAL WEIGHT RECORD — EXAMPLES

For these examples, the helicopter has no weight empty equipment missing, the fuel system is drained, the engine oil system is full, and the helicopter was leveled with a plumb bob. The helicopter was serviced with JP-5 fuel and MIL-L-23699 oil.

All changes made to the As-Weighed condition must be shown on the Actual Weight Record (Figure 8-7and Figure 8-8).

8-12. CALCULATING FINAL WEIGHT EMPTY CENTER OF GRAVITY

The final Weight Empty CG may be found by two procedures: use the weight empty CG limits (Figure 8-5) or use the gross weight flight limits (Figure 8-6).

Both procedures are shown in the sections that follows:

8-13. Use of the weight empty center of gravity limits

When a helicopter has a standard fuel system and a standard seating arrangement, use the weight empty CG limits (Figure 8-5) as a guide to correctly ballast the helicopter.

1. If the initial weight empty and CG are within the weight empty CG limit lines (Figure 8-5), the initial weight empty is the final weight empty. Write this value down on the Actual Weight Record form that is included in the flight manual.

2. If the computed center of gravity is outside the limits, the required center of gravity is found by moving horizontally to the nearest limit and reading the value at this point. If the limit lines are not vertical, the required CG that you use should be inside the limit line to allow for the increase in weight because of the addition of the ballast.

a. If the CG is aft of the limit and if the mid tailboom ballast is already installed, remove the ballast and calculate the initial weight empty and CG again before you calculate the required ballast.

b. If the CG is forward of the limit line and if the nose ballast is already installed, remove the ballast and calculate the initial weight empty and CG again before you calculate the required ballast.

Table 8-1. Sample weighing using electronic platform scales

SCALE LOCATION SCALE READING TARE WEIGHT NET WEIGHT

(LBS) (KG) (LBS) (KG) (LBS) (KG)

Fwd Left 679.2 308.1 2.2 1.0 677.0 307.1

Fwd Right 692.7 314.2 -3.3 -1.5 696.0 315.70

Aft 1523.0 690.8 4.0 1.8 1519.0 689.0

As Weighed 2894.9 1313.1 2.9 1.3 2892.0 1311.8

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Table 8-2. Weights for various fuels and oils

FUEL OIL DENSITY

LBS/GAL (KG/L)

JP-4 (Jet B) 6.5 0.779JP-5 (Jet A) 6.8 0.815

JP-8 6.8 0.815DOD-L-85734 8.4 1.007MIL-L-7808 7.7 0.923MIL-L-23699 8.4 1.007

UNUSABLE FUEL

FUEL WEIGHT CG MOMENT

(LBS) (KG) (INCHES) (MM) (IN-LBS) (MM-KG/100)

JP-4 17.2 7.8 114.6 2911 1971 227.1JP-5 18.0 8.2 114.6 2911 2063 238.7JP-8 18.0 8.2 114.6 2911 2063 238.7

TRAPPED/UNDRAINABLE FUELJP-4 4.5 2.0 110.6 2809 498 56.2JP-5 4.7 2.1 110.6 2809 520 59.0JP-8 4.7 2.1 110.6 2809 520 59.0

UNDRAINABLE ENGINE OILDOD-L-85734 1.6 0.7 192 4877 307 34.1MIL-L-7808 1.4 0.6 192 4877 269 29.3MIL-L-23699 1.6 0.7 192 4877 307 34.1

USABLE ENGINE OILDOD-L-85734 13.0 5.9 205 5207 2665 307.2MIL-L-7808 11.9 5.4 205 5207 2440 281.2MIL-L-23699 13.0 5.9 205 5207 2665 307.2

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Figure 8-2. Calculating as-weighed center of gravity (Example)

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Table 8-3. Deriving initial weight empty and center of gravity (example)

ITEM WEIGHT CG MOMENT


As-weighed 2892.0 1311.8 133.82 3399 387008 44587.9

Remove:

Engine Oil -13.0 -5.9 205.0 5207 -2665 -307.2

Plumb Bob -0.3 -0.1 170.1 4321 -51 -4.3

Undrain-able Fuel

-4.7 -2.1 110.6 2809 -520 -59.0

Add:

Unusable Fuel

18.0 8.2 114.6 2911 2063 238.7

Initial Weight Empty

2892.0 1311.9 133.41 3389 385835 44456.1

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Figure 8-3. Weight and balance station diagram

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NOTE

Do not install ballast in both the nose and the mid tailboom locations at the same time.

c. If the CG is aft of the limit and if the nose ballast is already installed (or if the CG is forward of the limit and if the mid tailboom ballast is already installed) calculate the additional ballast that will be required.

NOTE

When a helicopter has a unique loading configuration that is not standard, such as the crew or the passenger weights, the baggage compartment loading, or other variations, use the gross weight flight limits to calculate the ballast.

d. Calculate the required ballast using the formula that follows:

NOTE

To avoid interference with the controls the mid tailboom ballast must be applied as shown in paragraph 8-17.

3. To find the exact ballast, you may have to do more than one calculation because the ballast weight is limited at each location. To find the correct ballast weight, refer to Figure 8-4.

4. Once you find the correct ballast, calculate the final Empty Weight shown in Table 8-5.

Ballast = (weight empty) (required CG — calculated CG)

ballast CG — required CG

Table 8-4. Ballast locations

MAXIMUM BALLAST LONGITUDINAL CG LATERAL CG

(LBS) (KG) FS (INCHES) FS (MM) BL (INCHES) BL (MM)

Note 1 23.5 10.7 14.3 363 -4.8 -122

32 14.5 15.6 396 -2.5 -64

32 14.5 15.6 396 4.5 114

Note 2 12 5.4 303.4 7706 0.0 0

Note 2 12 5.4 313.4 7960 0.0 0

Note 2 1 0.5 299.3 7602 0.0 0

Note 2 1 0.5 307.5 7811 0.0 0

Note 2 1 0.5 309.3 7856 0.0 0

Note 2 1 0.5 317.5 8065 0.0 0

Note 1: Cannot be used when a 28 ampere hour battery kit is installed.

Note 2: Maximum total tailboom ballast is 20 lbs (9 Kg). Maximum ballast stack height is 0.5 inches (12.7 mm).

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5. Write down the ballast weight requirements on the helicopter Actual Weight Record (Figure 8-7 and Figure 8-8). When ballast is removed from the As-Weighed weight (step a. or b.), it must be shown on the Actual Weight Record. If part of the removed ballast is added again, add the entries together to show the total weight that was removed from each location.

6. Install and secure the required ballast (Paragraph 8-9).

8-14. Use of the gross weight flight limits

When a helicopter has a custom configuration such that the empty weight is more than the maximum empty weight on the chart (Figure 8-5), or the fuel system or the seating arrangement is not standard, use the gross weight flight limits to calculate the required ballast (Figure 8-6). Then the most forward and the most aft useful loads are calculated for the configuration. Examples of the steps that follow are given at the end of this section.

1. Use the procedures in Paragraphs 8-9 and 8-10and find the initial weight empty and CG.

2. Find the combination of useful load items (fuel, crew, passengers, baggage and cargo) which, when added to the initial weight empty, results in the most forward CG.

a. Include all items with a CG that is forward of the flight limit.

b. Exclude all items with a CG that is aft of the flight limit, except those items that are required for flight, such as engine oil.

c. Exclude most items that have a CG within the flight limit except those that are required for flight. Also, because the upper forward flight limit decreases, the items with a CG close to the flight limit should be checked to see if adding them will result in a gross weight CG that is outside the upper limit.

d. The sum of the weights and the moments for these items is known as the most forward useful load, and must be shown on the Actual Weight Record (Figure 8-10 and Figure 8-11).

3. Find the combination of useful load items which, when added to the initial weight empty, results in the most aft CG.

Table 8-5. Deriving final weight empty from initial weight empty (example)



Initial Weight Empty (from Table 8.3)

2892.0 1311.9 133.41 3389 385835 44456.1

Add:

Ballast @ FS 14.3 (363)

23.5 10.7 14.3 363 336 38.8

Ballast @ FS 15.6 (396)

18.0 8.2 15.6 396 281 32.5

Final Weight Empty

2933.5 1330.8 131.7 3346 386452 44527.4

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Figure 8-4. How to find the correct ballast weight

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Figure 8-5. Weight empty vs center of gravity (Sheet 1 of 2)

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Figure 8-5. Weight empty vs. center of gravity (Sheet 2)

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Figure 8-6. Gross weight longitudinal center of gravity limits - Standard units (Sheet 1 of 2)

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Figure 8-6. Gross weight longitudinal center of gravity limits - Standard units (sheet 2)

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Figure 8-7. Completing an actual weight record - Standard units (Example)

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Figure 8-8. Completing an actual weight record - Metric units (Example)

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Figure 8-9. Ballast installation

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a. Include all items with a CG that is aft of the flight limit.

b. Exclude all items with a CG that is forward of the forward flight limit, except those items that are required for flight, such as minimum crew weight.

c. Exclude most items that have a CG within the flight limit, except those that are required for flight.

d. The sum of the weights and the moments for these items is known as the most aft useful load, and must be shown on the Actual Weight Record (Figure 8-10 and Figure 8-11).

4. Add the most forward weight and moment to the initial empty weight and moment. The result is known as the most forward gross weight.

5. Add the most aft weight and moment to the initial empty weight and moment. The result is known as the most aft gross weight.

6. Compare the most forward gross weight and the most aft gross weight to the gross weight flight limits (Figure 8-6).

7. If either the most forward or most aft gross weight CG is outside the gross weight flight limits, find the ballast requirements as follows:

a. If the aft CG is outside the flight limits and if the mid tailboom ballast is already installed, remove the ballast. Calculate the most forward and the most aft gross weight CGs again. Then calculate the required ballast.

b. If the forward CG is outside the flight limits and if the nose ballast is already installed, remove the ballast. Calculate the most forward and the most aft gross weight CGs again. Then calculate the required ballast.

NOTE


c. If the aft CG is outside the flight limits and if the nose ballast is already installed, or if the forward CG is outside the flight limits and if the mid tailboom

ballast is already installed, calculate the required addi-tional ballast.

NOTE

The required CG is at the intersection of the gross weight and the appropriate gross weight limit line. If the limit lines are not vertical, the required CG that you use should be inside the limit line to show the increase in weight because of the addition of the ballast.

d. Calculate the required ballast. Use the formula that follows:

NOTE

To avoid interference with the controls, the mid-tailboom ballast must be applied as shown in paragraph 8-17.

1. If the most forward gross weight and the most aft gross weight CG are both outside the gross flight limits, change one of the useful load combinations in order to move the applicable gross weight CG on or inside the limit. Calculate the required ballast according to Step 7. Write down the useful load limitations on the Actual Weight Record (Figure 8-10and Figure 8-11).

2. If the required ballast is more than the maximum that is permitted, do one of the steps that follow:

a. Change the empty weight configuration to move the empty weight CG closer to the flight limit until the required ballast is equal to or less than the maximum that is permitted, or

b. Adjust the useful load combination to decrease the required ballast to the maximum that is permitted or less. Write down the useful load limitations on the Actual Weight Record (Figure 8-10and Figure 8-11).

3. Write down the ballast weight requirements on the helicopter Actual Weight Record (Figure 8-10 and Figure 8-11). When the ballast is removed from the

Ballast = (gross weight) (required CG — computed CG)

ballast CG — required CG

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As-Weighed weight (Step a. or b.), it must show on the Actual Weight Record. If part of the removed ballast is added again, put the entries together to show the weight removed from each location.

4. Install the required ballast (Paragraph 8-17).

8-15. SAMPLE WEIGHING PROCEDURE

For this example, the helicopter is unpainted, the fuel system is drained and the engine oil system is full. The helicopter was serviced with JP-5 fuel and MIL-L-23699 oil. The helicopter is configured for night rescue. The helicopter has litters installed, but does not have the searchlight and a receiver/transmitter box. Refer to Table 8-6 and Figure 8-10. For the metric equivalent of the example, refer to Figure 8-11.

The most forward gross weight and the most aft gross weight are both inside the gross weight flight limits. The initial weight empty is the final weight empty. Write down all the data on the Actual Weight Record (Figure 8-10 and Figure 8-11).

8-16. CALCULATING THE LATERAL CENTER OF GRAVITY

1. The centerline of the helicopter is Buttline 0.00. The moment arms to the left hand side (when looking forward) are negative (-) and the moment arms to the right hand side are positive (+). The forward jack fittings are located at BL - 16.82 (- 427 mm) and at BL 16.82 (427 mm). The aft jack fitting is on the centerline (BL 0.00).

NOTE

Left hand moment will be negative.

2. On each forward scale, multiply the net weight by its arm to get the left hand and the right hand moments for the helicopter. Do not calculate the lateral moment for the aft scale because the lateral moment for the aft scale is always zero.

3. Add the left hand and right hand moments together. Divide this total by the As-Weighed weight. The result is the As-Weighed helicopter lateral CG in inches (millimeters) to the left hand side or right hand side of Buttline 0.00.

4. Write down these calculations on the Actual Weight Record Form (Figure 8-7 through Figure 8-11).

5. As the empty weight is calculated (Paragraph 8-10 and Paragraph 8-12), write down the lateral arms and moments on the Actual Weight Record.

6. Do not ballast for lateral CG, Refer to BHT-407-FM. For the seating limitations to maintain the helicopter within the lateral gross weight flight limits.

8-17. INSTALLATION OF BALLAST

Ballast weights are manufactured from lead sheets and vary in thickness from 0.0625 inch (1.58 mm) to 0.25 inch (6.35 mm). Each ballast weight has the value of its weight stamped on it. Ballast weights may require special support assemblies, brackets, or hardware to be installed. Refer to Figure 8-9 for the ballast installation. Ballast weights may be modified to meet the ballast requirements without excess weight as shown on Figure 8-9.

1. Find the amount of ballast to be added or removed at each location (Paragraph 8-8).

NOTE


2. Find the number of each size of ballast weight that is required to get the correct weight at each location.

a. In the battery compartment at FS 14.3 (363mm), the total weight of the ballast installation is 23.5 pounds (10.7 Kg) if the 17 ampere hour battery is installed. If the 28 ampere hour battery kit is installed, this ballast location cannot be used. Refer to the 407 Illustrated parts breakdown (IPB) for the nominal weights of the ballast.

b. In the landing light compartment at FS 15.6 (396 mm), the total weight of the ballast installation is 64 pounds (29.1 Kg), accommodating 32 pounds (14.5 Kg) in both left hand and right hand installations. Refer to 407 IPB for the nominal weights of the ballast. For weight adjustment, holes that are not greater than 2.5 inches (63.5 mm) in diameter may be drilled 3.0 inches

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Table 8-6. Sample weighing procedure


(LBS) (INCHES) (IN-LBS)As-Weighed 3270.0 129.6 423793

Remove: Engine oil -13.0 205 -2665 Plumb bob -0.3 170.1 -51

Undrainable fuel -4.7 110.6 -520Add:

Unusable fuel 18.0 114.6 2063 Paint 16.7 167.0 2789

SX-16C searchlight 36.0 13.1 472 800 MHz R/T 6.8 200.0 1360

Initial Weight Empty 3329.5 128.3 427241FIRST, CALCULATE THE MOST FORWARD USEFUL LOAD

Pilot 170.0 65.0 11050Passenger (Mid) 170.0 91.0 15470Litter Patients (2) 340.0 108.0 36720

Engine Oil 13.0 205.0 2665Fuel (74.8 gallons) JP-5 508.6 116.0 58998Most FWD useful load 1201.6 104.0 124903

SECOND, CALCULATE THE MOST AFT USEFUL LOADPilot 170.0 65.0 11050

Engine oil 13.0 205.0 2665Fuel (28.4 gallons) JP-5 193.1 137.0 26455

Most aft useful load 376.1 106.8 40170THIRD, CALCULATE THE MOST FORWARD GROSS WEIGHT AND MOST AFT GROSS WEIGHT

Initial weight empty 3329.5 128.3 427241Most FWD useful load 1201.6 104.0 124903

Most FWD gross weight 4531.1 121.9 552143

Initial weight empty 3329.5 128.3 427241Most aft useful load 376.1 106.8 40170

Most aft gross weight 3705.6 126.1 467410

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Figure 8-10. Actual weight record — Standard unit

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Figure 8-11. Actual weight record — Metric units

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(76.2 mm) from the top edge and 4.5 inches (114.3 mm) from the forward edge.

CAUTION

TO AVOID CONTROLS INTERFERENCE, LIMIT THE MAXIMUM STACK HEIGHT OF THE BALLAST IN THE MID-TAILBOOM LOCATION TO 0.5 INCH (12.7MM).

c. In the mid-tailboom location, the not-to-exceed weights are as follows: 12.0 pounds (5.4 Kg) at FS 303.4 (7706 mm), 12.0 pounds (5.4 Kg) at FS 313.4 (7960 mm) with a total not-to-exceed weight of 20.0

pounds (9.1 Kg) The maximum stack height is 0.5 inch (12.7 mm). Refer to the 407 IPB for the nominal weights of the ballast. For weight adjustment, holes that are no greater than 0.75 inch (19 mm) in diameter may be drilled in the plates.

3. When you install the ballast weights, make sure that the plates are aligned as shown in Figure 8-9. The length of the bolts (6) and (9) is given by the total thickness of weights that are installed. Tighten the bolts (6) and (9) to the standard torque.

8-18. MODEL 407 KIT WEIGHTS

Refer to Table 8-7 (Standard units) and Table 8-9(Metric units) for various Bell Helicopter kit weights.

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Table 8-7. Kit weights (Standard units)

NOMENCLATUREKIT NUMBER

WEIGHT CHANGE

LONG CG (INCHES)

LONG MOMENTS (LB. INS.)

LAT. CG (INS)

LAT. MOMENT (LB. INS.)

Snow baffles206-706-208-103

5.2 130.5 678.6 0.0 0.0

Partical separator206-706-212-119

13.2 141.8 1871.8 1.0 13.2

Cargo hook206-706-341-109

16.7 121.0 2020.7 0.0 0.0

Cargo hook provisions206-706-341-111

3.7 102.9 380.7 -3.5 -13.0

Rotor brake206-706-502-103

9.9 120.9 1196.9 0.1 1.0

VHF/ADF provisions407-705-001-101

3.9 72.5 282.8 0.2 0.8

VHF equipment KX155407-705-001-103

9.8 64.4 631.1 1.4 13.7


8.6 67.4 579.6 1.4 12.0

ADF equipment KR87407-705-001-107

8.9 103.2 918.5 0.5 4.5

Transponder provision (KT76)407-705-001-109

0.9 52.2 47.0 -6.2 -5.6

Transponder eq KT76407-705-001-111

3.0 43.6 130.8 1.3 3.9


0.6 44.4 26.6 0.0 0.0


4.0 40.6 162.4 0.4 1.6

GPS provision KLN89407-705-001-117

3.1 45.6 141.4 0.2 0.6

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GPS equipment KLN89407-705-001-119

6.5 39.5 256.8 0.8 5.2

OMNI (with CDI)407-705-001-121

3.4 141.7 481.8 -1.7 -5.8

VHF provisions KY196407-705-001-123

1.6 99.3 158.9 -1.0 -1.6

VHF equipment KY196407-705-001-125

3.6 62.0 223.2 0.9 3.2

Avionic master switch407-705-001-127

0.6 59.8 35.9 0.4 0.2

KCS55 provision407-705-002-101

4.0 98.1 392.4 -0.7 -2.8

KCS55 equipment407-705-002-103

7.6 164.8 1252.5 -2.7 -20.5

KCS55/GPS provisions407-705-002-105

4.3 93.0 399.9 -0.6 -2.6

KCS55/GPS equip-ment407-705-002-107

8.5 151.0 1283.5 -2.6 -22.1

Cargo restraint407-705-201-101

1.4 85.1 119.1 -0.6 -0.8

Encoding altimeter407-706-001-101

0.7 40.4 28.3 9.9 6.9

Flight instruments407-706-003-101

9.3 37.9 352.5 7.4 68.8

28 amp hour battery407-706-004-101

24.7 15.8 390.3 1.0 24.7

Emergency locator transmitter407-706-005-101

3.8 38.1 114.8 -3.3 -12.5

High skid gear407-706-007-101(includes Flitesteps)

34.5 113.0 3898.5 0.0 0.0

Table 8-7. Kit weights (Standard units) (Cont.)


WEIGHT CHANGE

LONG CG (INCHES)


LAT. CG (INS)


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Table 8-8. Weight and balance calculation for Bell 407 with standard skid gear (Standard units) — Example

Pop out floats407-706-008-101(includes Floatsteps)

237.9 104.7 24908.1 0.1 23.8

L/G fairings407-706-010-101

11.8 114.9 1355.8 0.0 0.0

Sliding window407-706-301-103

2.4 116.1 278.6 0.0 0.0

Dual controls407-706-702-101

10.4 48.8 507.5 -13.3 -138.3

DESCRIPTION WEIGHT(LBS)

CENTER OF GRAVITY

(INCH)

LONGITUDINAL MOMENT

LATERAL MOMENT

Helicopter Empty Weight 2391.3 129.8 310390.7 265

High skid, 407-706-007-101, weight change

34.5 113.0 3898.5 0

New helicopter empty weight 2425.8 129.6 314289.2 265

Table 8-7. Kit weights (Standard units) (Cont.)


WEIGHT CHANGE

LONG CG (INCHES)


LAT. CG (INS)


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Table 8-9. Kit weights (Metric units)


WEIGHT CHANGE

(KG)

LONG CG (MM)

LONG MOMENTS

(KG.MM/100)

LAT. CG (MM)

LAT. MOMENT

(KG.MM/100)

Snow baffles206-706-208-103

2.4 3315 79.6 0.0 0.0

Partical separator206-706-212-119

6.0 3602 216.1 25 1.5

Cargo hook206-706-341-109

7.6 3073 233.5 0.0 0.0

Cargo hook provisions206-706-341-111

1.7 2614 44.4 -89 -1.5

Rotor brake206-706-502-103

4.5 3071 138.2 3 0.1

VHF/ADF provisions407-705-001-101

1.8 1842 33.2 5 0.1


4.4 1636 72.0 36 1.6


3.9 1712 66.8 36 1.4

ADF equipment KR87407-705-001-107

4.0 2621 104.8 13 0.5


0.4 1326 5.3 -157 -0.6


1.4 1107 15.5 33 0.5


0.3 1128 3.4 0.0 0.0


1.8 1031 18.6 10 0.2

GPS provision KLN89407-705-001-117

1.4 1158 16.2 5 0.1

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GPS equipment KLN89407-705-001-119

2.9 1003 29.1 20 0.6

OMNI (with CDI)407-705-001-121

1.5 3599 54.0 -43 -0.6

VHF provisions KY196407-705-001-123

0.7 2522 17.7 -25 -0.2

VHF equipment KY196407-705-001-125

1.6 1575 25.2 23 0.4

Avionic master switch407-705-001-127

0.3 1519 4.6 10 0.0

KCS55 provision407-705-002-101

1.8 2492 44.9 -18 -0.3

KCS55 equipment407-705-002-103

3.4 4186 142.3 -69 -2.3

KCS55/GPS provisions407-705-002-105

2.0 2362 47.2 -15 -0.3

KCS55/GPSequipment407-705-002-107

3.9 3835 149.6 -66 -2.6

Cargo restraint407-705-201-101

0.6 2162 13.0 -15 -0.1

Encoding altimeter407-706-001-101

0.3 1026 3.1 251 0.8

Flight instruments407-706-003-101

4.2 963 40.4 188 7.9

28 amp hour battery407-706-004-101

11.2 401 44.9 25 2.8

Emergency locator transmitter407-706-005-101

1.7 968 16.5 -84 -1.4

High skid gear407-706-007-101(includes Flitesteps)

15.6 2870 447.7 0.0 0.0

Table 8-9. Kit weights (Metric units) (Cont.)


WEIGHT CHANGE

(KG)

LONG CG (MM)

LONG MOMENTS

(KG.MM/100)

LAT. CG (MM)

LAT. MOMENT

(KG.MM/100)

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Table 8-10. Weight and balance calculation for Bell 407 with standard skid gear (Metric units) — Example

Pop out floats407-706-008-101(includes Floatsteps)

107.9 2659 2869.1 3 3.2

L/G fairings407-706-010-101

5.4 2949 159.2 0.0 0.0

Sliding window407-706-301-103

1.1 2936 32.3 0.0 0.0

Dual controls407-706-702-101

4.7 1240 58.3 -338 -15.9

DESCRIPTION WEIGHT(KG)

CENTER OF GRAVITY

(MM)

LONGITUDINAL MOMENT

(MMKG/100)

LATERAL MOMENT

(KG.MM/100)

Helicopter Empty Weight 1084.7 3297 35762.6 27.1

High skid, 407-706-007-101, weight change

15.6 2870 447.7 0.0

New helicopter empty weight 1100.3 3291 36210.3 27.1

Table 8-9. Kit weights (Metric units) (Cont.)


WEIGHT CHANGE

(KG)

LONG CG (MM)

LONG MOMENTS

(KG.MM/100)

LAT. CG (MM)

LAT. MOMENT

(KG.MM/100)

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Figure 8-12. Actual weight record (Sheet 1 of 7)

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Figure 8-12. Actual weight record (Sheet 2)

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Documents

407-MM-CH08