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Aircraft Weight and Center of Gravity Estimation

 

Table 8.7. Determination of Bizjet CG location

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Item Group

 

Mass (kg)

X (m)

Moment

Z (m)

Moment

 

 

 

 

 

 

 

 

 

 

Fuselage

 

930

6.8

4,284

1.6

1,488

 

 

Wing

 

864

7.8

6,739.2

1

864

 

 

H-tail

 

124

14

1,736

8

992

 

 

V-tail

 

63

15

945

3

189

 

 

Undercarriage (nose)

110

1.2

132

0.4

44

 

 

Undercarriage (main)

270

8.4

2,268

0.5

135

 

 

Nacelle/pylon

 

212

10.2

2,346

2.1

460

 

 

Miscellaneous

 

 

 

 

 

 

 

 

Power plant

 

1,060

11

11,660

1.9

2,014

 

 

Systems

 

1,045

6.5

6,792.5

1

1,045

 

 

Furnishing

 

618

6

3,708

2

1,236

 

 

Contingencies

 

143

3

429

1.2

171.6

 

 

MEM

5,457

 

 

 

 

 

 

 

Crew

 

180

3

540

1.4

252

 

 

Consumable

 

119

4.25

505

1.5

152

 

 

OEM

5,800

 

 

 

 

 

 

 

Payload

 

1,100

6

6,600

1.1

1,210

 

 

Fuel

 

2,500

8.5

21,250

1

2,500

 

 

Total moment at MTOM

9,400

 

69,934.7

 

12,752.6

 

 

MRM

9,450

 

x¯ = 7.44 m

z¯ = 1.357 m

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

component positions. Determining the aircraft neutral point is not addressed in this book, but it is approximately 50 to 55% of the wing MAC. Therefore, in this case, only small changes may be required to fine-tune the aircraft CG limits. Changing the wing position may be problematic, but a small degree of engine repositioning can be effective. Relocating heavy onboard items is easy and effective for last-minute finetuning, especially during flight-testing.

8.12.2 First Iteration to Fine Tune CG Position Relative to Aircraft and Components

The preliminary aircraft configuration begins in Chapter 6 with a guesstimated MTOM, engine size, and CG position. It is unlikely that the computed aircraft mass as worked out in this chapter will match the estimated mass. In fact, the example shows that it is lighter, with a more accurate CG position; therefore, this replaces the estimated values in Chapter 6.

In principle, the aircraft configuration must be revised at this stage of progress as the first iteration. Final sizing is accomplished in Chapter 11, when iteration is required. Coursework may require only one iteration cycle of computation.

8.13 Rapid Mass Estimation Method – Military Aircraft

This extended section presents the military aircraft rapid mass estimation method in terms of mass fraction (in percentage) of maximum take-off mass (Mi /MTOM),

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