Bizjet Aircraft CG Location Example

Table 8.7 and Equations 8.54 and 8.55 are used to locate the CG. SI units are used.

Both the mass and the CG location are slightly different than the preliminary data. This results in the CG angle, в = tan-1 (8.4 -7.44)/1.357 = tan-1 0.7 = 35 deg. This is a satisfactory angle to cover the maximum fuselage-rotation angle at takeoff.

The CG is located almost at the middle of the baseline aircraft length, and the wing is positioned just behind it, which indicates that the CG is in the forward posi­tion. Proper CG positioning can be established after the aircraft neutral point is determined; the forward and aft CG limits can be ascertained by fine-tuning the

Table 8.7. Determination ofBizjet 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 x = 7.44 m

12,752.6 z = 1.357 m

MRM 9,450

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 fine – tuning, especially during flight-testing.

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