Global Model Technology Base

All aircraft arc evaluated with the same analysis routines. All aircraft arc designed with the same level of structural, aerodynamic and propulsion technology. This level is based on that achieved by a supersonic transports that can be produced in 2005. The most important pans are:

Aerodynamics

Skin friction is based on fully turbulent How w ith characteristic sand grain roughness. It is not likely that laminar flow can bring a real advantage to the SCT before 2005 Unresolved issues are the absence of experimental facilities, the high-Re numbers, the wave drag penalty incurred due to the required low-cross flow pressure distributions and the weight – and space penalty due to the suction equipment. Тік – inviscid flow drag is based on the theoretical minimum potential drag for a given distribution of lift and volume. This drag is then corrected based on the actual achieved drag levels in the detailed design This correction factor therefore reflects the potential drag improvement that is still achievable. Factors of 1.1 • 1.2 for the volume dependent wave drag and the the litt dependent wave drag arc typical for a high performance design (371) de­scribes the 1992 status of the aerodynamic global model and its corresponding intermediate mod­el applied to the design of an ofw. Ref. (373) also show s an example of its application to an arrow wing aircraft.

Structures

Structural calculations are based on a mix of composite materials and metallic alloys. DA expe­rience shows that intermediate carbon fibers with BMI resins achieve strain levels in excess of 0.5 % resulting in weight savings over conventional primary structures in excess of 25 Я-. The airframe life was specified to be over 75.000 hours with 50,000 supersonic flying hours and 25,000 pressure cycles. A minimum skin thickness of 2 mm was specified to minimize foreign object damage. An overview of SCT structures and materials technology can be found in Erman – ni’s publication 1361]. Weight is calculated with shell-theory [371] describes the 1992 status of the structural model. Reference (359] presents the intermediate model applied to the design of an arrow wing fuselage.

Propulsion

A turbofan engine with mixing and a variable throat area was used. Polytropic component effi­ciencies arc typical of a future generation: between 90 and 935& for the compressor, fan and tur­bine. The maximum turbine entry’ temperature was limited to 1800 К and the maximum pressure ratio to 50. iNoisc suppression of up to 14 dB is allow ed, but a penalty in thrust and weight is paid.

Economy – Objective Function

Since aircraft cost is used to compare the various configurations, the cost model is one of the most important. The DA economic model represents the cost structure of a curopcan airline. The objective function ihat is used throughout this study is total operating cost relative to a subsonic reference. In some cases this operating cost was corrected for the expected increase in ticket pnee to account for the block lime savings. The influence of the cost of development on sales price is included. Therefore, this study compares the relative operating cost of various aircraft for the same mission, permitting comparisons of one concept with respect to the other.

The influence on the right objective function selection on the relative “goodness" of an aircraft is clearly demonstrated by Table 3. Assume a fully loaded 250 passenger aircraft designed for a range of 9000 km with cost calculated for a reference range of 6000 km. W’e con­sider five types of aircraft 3 symmetric wing bodies designed for Mach 2. (a). 1.6 (b)and 0.85 (c) respectively and an oblique flying wing designed for Mach 2.0 (d) and 1.6 (e) and an oblique wing body designed for Mach 1.6 <f) Based on DOC and M. aircraft c (subsonic) is the best

to

followed by e. d. b. a and f. Including ІОСЧ and the expected increase of revenue the Oblique Flying Wings d. c are the best followed by a. b. c and f. This comparison clearly shows the necessity to agree on a common objective function.

Type

DOC

TOC

TOC-Д Rev

a: M 2 0 SWB

286

366

622

4.72

b: M 1 6 SWB

266

3.46

6.03

4.74

с: M 0.8 SWB

139

2.54

5.19

5.03

d: M 2.0 OFW

251

3.28

5.79

4.28

с: M 1.6 OFW

238

3.17

5.71

4 41

f: M 1.6 OWB

323

4.14

6.79

5.50

Table 3 Effect of objective on goodness

Technology Standard

Supersonic aircraft are assumed to have some technologies that are not required for subsonic aircraft:

• Flutter mode control load alleviation, which would allow increased sweep with thin wings.

• Active stability and control for all supersonic aircraft. Both the symmetric and asymmetric configuration have similar stability margins and have their neutral point at the MZFW center of gravity location.

• Powcrplant variable geometry inlet and nozzle design.

• Improved navigational and environmental control systems.

To obtain a good impression about the impact of the sons of technologies proposed for the supersonic transport they were applied to a A340 design. We took the A340 specification and optiniiz. cd the configuration with the same models, requirements, technology factors and constraints as applied to the 2005 supersonic transport. Table 4 shows the results of this study. The first column shows the actual A340 data. Ref (371) is a single point optimization of an air­craft with the A340 mission and technology[8]. These difference between the optimized and the datum A340 are well outside the spectrum of the accuracy of the global method. Ref. [373] is the same specification with the 2005 supersonic technology. The dropped by 31 In the

last column the cabin standard and the range arc reduced to SCT specification. This SCT stand­ard is 10 % first class (40" pitch). 30 % business (36" pitch) and the rest economy (32" pitch).

A340-date

Ref. 1

Ref. 2

SCT

L/D

200

19.7

19.7

19.2

s. fx.

0.59

0.58

0.58

0.58

DEM (t)

127

125

80

71.9

271

275

189

155

Range (km)

13900

15000

15000

11000

Cabin

A340

A 340

A 340

SCT

Structure

Alu

Alu

CF

CF

Table 4 Technolog} Standard

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