Worked-Out Example: Finalizing the Preliminary Civil Aircraft Configuration

It is interesting to observe how the aircraft is gradually taking shape – it is still based on a designer’s past experience but soon will be formally sized to a satisfying rational configuration to offer the best characteristics for the design.

A preliminary three-view diagram of the civil aircraft can now be drawn (Figure 6.14). It will be revised after the remaining aircraft components are positioned and a revised CG location is established. The next iteration is after air­craft sizing in Chapter 11.

At this stage, all aircraft components are ready to be assembled using the building-block concept to generate a preliminary aircraft configuration, as shown in Figure 6.14. The three variants (see Figure 6.8) maintain the same wing, empennage,

and nacelle (some internal structures are lightened or reinforced without affecting manufacturing jigs and tools).

The configuration is similar to the Learjet 45 but it is not the same; there are con­siderable differences in configuration, component weights, and performance. Read­ers may compare the two using the Jane’s All the World’s Aircraft Manual.

Chapter 11 sizes the aircraft to its final dimensions and finalizes the configura­tion based on the aircraft and component mass worked out in Chapter 8. Following is a summary of the worked-out civil aircraft preliminary details (from statistics):

Market Specifications

Upsweep: 10 deg Overall Height (Depth): 178 cm (70 in) Fineness Ratio: 8.6 Span: 15 m, Aspect Ratio: 7.5 Tip Chord, CT: 1.143 m (3.75 ft) Taper Ratio, X: 0.4 Л1 14 deg t/c: 10% 4 Height: 2.13 m (7 ft) AR = 2.08 Tip Chord, CT: 1.54 m (5.05 ft) Taper Ratio, X: 0.6 Л1 = 40 deg 4 t/c: 10%

Payload: 10 Passengers + Baggage: 1,100 lb HSC Mach: 0.74 Initial Climb Rate: 16 miles/s Takeoff Field Length: 1,000 m

Baseline Aircraft Mass (from statistics)

MTOM: 9,500 kg («21,000 lb)

Fuel Mass: 1,200 kg («2,650 lb)

Baseline External Dimensions

Fuselage (determined from passenger capacity)

Length: 15.24 m (50 ft)

Overall Width: 173 cm (68.11 in)

Average Diameter: 175.5 cm (70 in)

Wing (aerofoil 65-410)

Planform (Reference) Area: 30 m2 Root Chord, CR: 2.87 m (9.4 ft)

MAC: 2.132 (7 ft)

Dihedral: 3 deg, Twist: 1 deg (washout)

V-Tail (Aerofoil 64-010)

Planform (Reference) Area: 4.4 m2 (47.34 ft2) Root Chord, CR: 2.57 m (8.43 ft)

MAC: 2.16 (7.1 ft) t/c: 10%

Rudder: 0.75 m2 (8 ft2)

H-Tail (T-tail, aerofoil 64-210 – installed with negative camber)

Planform (Reference) Area: 5.88 m2 (63.3 ft2) Span: 5 m (16.4 ft) AR = 4.42 Root Chord, CR: 1.54 m (5.04 ft) Tip Chord, CT: 0.77 m (2.52 ft)

MAC: 1.19 m (3.9 ft) Taper Ratio, X: 0.5 Л1 = 15 deg

Dihedral: 5 deg Elevator: 1.21 m2 (13 ft2) t/c: 10%

Nacelle

Length: 2.62 m (8.6 ft) Maximum Diameter: 1.074 m (3.52 ft)

Bare Engine (each)

Takeoff Static Thrust at ISA Sea Level: 3,800 lb (17,235 N) per engine with BPR = 5

Engine Dry Weight: 379 kg (836 lb)

Fan Diameter: 0.716 m (28.2 in)

Length: 1.547 m (60.9 in)

Short Variant (all component dimensions except the fuselage length are invariant) Fuselage: Length: 13.47 m (44.2 ft) (see Figure 6.8).

Long Variant (all component dimensions except the fuselage are invariant) Fuselage: Length: 16.37 m (53.7 ft) (see Figure 6.8).