Front (Nose Cone) and Aft-End Closure

The tear-drop-shaped streamlined closure of the fuselage at both ends of the con­stant midsection keeps the nose cone blunter than the gradually tapered aft cone, as shown in Figure 4.15.

Figure 4.14. Passenger number versus fuselage length (courtesy of MacMasters)

Figure 4.15 illustrates the front fuselage closure (i. e., nose cone) length, Lf, enclosing the flight deck (i. e., pilot cockpit), followed by the constant-section pay­load (passengers, in this case) shell. Being in a favorable pressure gradient of the flow, it is blunter than the aft closure. The aft-fuselage closure (tail cone) length, La, encloses the rear pressure bulkhead with a gradual closure in an adverse pressure gradient and has some degree of upsweep. In the center, the rotated cross-sectional view of the fuselage is shown.

average diameter, Dave = (H + W)/2

front-fuselage closure ratio, Fcf = Lf/Dave (also known as the (4.2)

nose fineness ratio)

aft-fuselage closure ratio, Fca = La/Dave

Figure 4.16 shows several examples of current types of commercial transport aircraft designs. Statistical values for the front – and aft-fuselage closure are summa­rized in Table 4.3.

The front-end closure of bigger aircraft appears to be blunter than on smaller aircraft because the nose cone is sufficiently spacious to accommodate pilot posi­tioning and instrumentation. A kink appears in the windscreen mould lines of the

Aircraft

L(m)

D(m)

H-(m)

W – (m)

H/W Lf/D

La/D

UA

CA

A300-600 (TA, TF, LW)

53.62

5.64

5.64

5.64

1

2.60

3.103

5

9

A310-300 (TA, TF, LW)

46.66

5.64

5.64

5.64

1

1.60

3.40

5

11

A320-200 (TA, TF, Lw)

37.57

3.96

3.96

3.96

1

1.50

3.40

4

8

A330-300 (TA, TF, LW)

59.00

5.64

5.64

5.64

1

1.82

3.64

8

11

A340-600 (TA, TF, LW)

59.39

5.64

5.64

5.64

1

1.60

3.32

8

9

A380 (TA, TF, LW)

70.40

7.78

8.41

7.14

1.50

3.91

5

11

Boeing 737 (TA, TF, LW)

31.28

3.95

4.11

3.79

1.10

2.80

7

15

Boeing 747 (TA, TF, Lw)

68.63

7.30

8.10

6.50

1.31

3.31

5

11

Boeing 757 (TA, TF, Lw)

46.96

4.05

4.00

4.10

1.64

2.91

6

13

Boeing 767 (TA, TF, LW)

47.24

5.03

5.03

5.03

1

1.17

2.67

7

15

Boeing 777 (TA, TF, LW)

63.73

6.20

6.20

6.20

1

1.23

2.85

7

13

MD11 (TA, TF, LW)

58.65

6.02

6.02

6.02

1

1.45

2.82

5

13

Tupolev 204 (TA, TF, LW)

46.10

3.95

3.80

4.10

1.46

2.96

5

9

Fokker 100 (TA, TF, LW)

32.50

3.30

3.05

3.49

1.42

3.42

2

10

Dornier 728 (TA, TF, LW)

27.03

2.56

2.05

3.25

1.34

2.60

5

13

Dornier 328 (RA, TF, LW)

20.92

2.42

2.425

2.415

1.27

2.64

5

10

Dash8 Q400 (RA, TP, HW)

25.68

2.07

2.03

2.11

1.71

3.22

4

9

Bae RJ85 (RA, TP, HW)

28.55

3.56

3.56

3.56

1

1.46

2.62

4

12

Skyvan (RA, TP, HW)

12.22

square

2.20

2.20

0.95

2.00

9

0

Cessna 560 (BJ, TF, LW)

15.79

5.64

5.64

5.64

1

2.05

2.91

2

8

Learjet 31A (BJ, TF, LW)

x

5.64

1.63

1.63

2.17

3.64

2

5

Cessna 750 (BJ, TF, LW)

21.00

1.80

1.80

1.80

1

2.00

3.00

7

15

Cessna 525 (BJ, TF, LW)

14.00

1.60

1.60

1.60

1

2.00

2.56

7

13

Learjet 45 (BJ, TF, LW)

5.64

1.75

1.72

1.91

2.86

8

4

Learjet 60 (BJ, TF, Lw)

17.02

3.96

1.96

1.96

1

1.91

2.82

2

5

CRJ 700 (RA, TF, LW)

2.69

2.69

2.69

1

1.60

3.15

5

12

ERJ 140 (RA, TF, LW)

26.58

2.00

2.89

3

14

ERJ 170 (RA, TF, LW)

29.90

3.15

3.35

2.95

1.56

2.67

3

13

C17 (MT, TF, HW)

49.50

6.85

6.85

6.85

1

0.85

3.41

10

12

C130 (MT, TF, HW)

34.37

4.33

4.34

4.32

0.95

2.56

9

12

Table 4.3. Fuselage closure parameters

Notes:

TA – Transport aircraft RA – Regional aircraft BJ – Business jet MT – Military transport TF-Turbofan TP-Turboprop

LW – Low wing HW – High wing L – Fuselage length D – Fuselage diameter

H – Fuselage height W – Fuselage width Lf – Front-closure length Lf – Aft-closure length UA – Upsweep angle, deg CA – Closure angle, deg

fuselage to fit flat glasses on a curved fuselage body; flat surfaces permit wiper instal­lation and are less costly to manufacture. Some small aircraft have curved wind­screens that permit smooth fuselage mould lines.

The aft-end closure is shallower to minimize airflow separation when the bound­ary layer becomes thicker. All fuselages have some upsweep for aircraft rotational clearances at takeoff. The difference in shaping is minor and is a result of the designer’s choice. Designers must configure a satisfactory geometry with attention to all operation and structural requirements (e. g., pilot vision polar [see Section 4.7.4], pressure bulkhead positions, and various doors). Table 4.4 lists typical guide­lines for the fuselage front – and aft-end closure ratios; the range represents current statistical values.

Table 4.4. Fuselage front – and aft-closure ratios (no rear door)

Seating

Front-fuselage closure

Aft-fuselage closure

Aft-closure

abreast

ratio, Fcf

ratio, Fca

angle (deg)

<3

^1.7 to 2

^2.6 to 3.5

^5 to 10

4 to 6

^1.5 to 1.75

^2.5 to 3.75

^8 to 14

>7

^1.5

^2.5 to 3.75

^10 to 15

A finer aft-closure angle is desired; however, for larger aircraft, the angle increases to keep the length (Lf) to an acceptable level to reduce weight and cost.

There are special designs that may not fall in this generalized table. Designers may exercise their own judgment in making a suitable streamline shape to allow for an upsweep to clear for aircraft rotation at takeoff.

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