Systems Group Mass

MTOW = 9,500kg (use Equation 8.47),MsYs = 0.11 x 9,500 = 1,045 kg.

8.11.5 Furnishing Group Mass

MTOW = 9,500 kg (use Equation 8.50), Mfur 0.065 x 9,500 = 618 kg

8.11.6 Contingency Group Mass

MTOW = 9,500kg (use Equation 8.52), MCoNT = 0.015 x 9,500 = 143 kg

8.11.7 Crew Mass

There are two flight crew members and no cabin crew. Therefore, Mcrew = 2 x 90 = 180 kg.

8.11.8 Payload Mass

There are ten passengers. Therefore, Mpl = 10 x 90 = 900 kg.

8.11.9 Fuel Mass

The range requirement is 2,000 nm carrying ten passengers. From statistical data given in Table 8.1, take the highest value of 26% of MTOW, Mfuel = 0.26 x 9,500 = 2,470 « 2,500 kg.

8.11.10 Weight Summary

Table 8.5 is the weight summary obtained by using the coursework example worked out thus far. The last column provides the estimation as a result of the graphical solution (in bracket – kg).

This computation requires further iterations to be fine-tuned for better accu­racy. The CG position is established in the next section, when further iterations will yield a better picture.

Variant Aircraft in the Family

For simplification, linear variations are considered, which should be worked out as a coursework exercise.

Table 8.6. Typical values of component CG locations: civil aircraft

Component

CG and typical % of component characteristic length

1.

Fuselage group

45%

2.

Wing group

No slat-30% of MAC With slat – 25% MAC

3.

H-tail group

30%

4.

V-tail group

30%

5.

Undercarriage group

At wheel center (nose and main wheels taken separately)

6.

Nacelle + pylon group

35%

7.

Miscellaneous

As positioned – use similarity

8.

Power plant group

50%

9.

Systems group

As positioned – use similarity (typically 40% of fuselage)

10.

Furnishing group

As positioned – use similarity

11.

Contingencies

As positioned – use similarity

MEM

(do not need to compute CG)

12.

Crew

As positioned – use similarity

OEM

Compute

13.

Payload

As positioned (distribute around CG)

14.

Fuel

As positioned (distribute around CG)

MTOM

Compute

MRM

Compute

Longer Variant. Increase APayload = 400 kg, AFuselage = 300 kg, AFurnish = 200 kg, AFuel = 300 kg, and AOthers = 200 kg. Total increase = +1,400 kg; MTOMLong = 10,900 kg (no structural changes).

Smaller Variant. Decrease APayload = 500 kg, AFuselage = 350 kg, AFurnish = 250 kg, AFuel = 350 kg, and AOthers = 250 kg (lightening of the structures). Total decrease = -1,700 kg; MTOMSmall = 7,800 kg.

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