Aeronautical Engineer’s Data Book - part 7 pptx

156 Aeronautical Engineer’s Data Book 10.1.2 Flaps Trailing and leading edge flaps change the effective camber of the wing, thereby increas­ing lift.. 157 Aircraft design and constructio

Table 10.2 Military aircraft data

Model Harrier GR5 F–15 Eagle F–14 B MB–339A Hawk T Mk 1 Mirage 2000–B F–14D Tomcat Euro-fighter 2000 F–117A Stealth

service

Role VTOL attack Tactical fighter Shipboard strike Jet trainer Jet trainer Strike fighter Strike fighter Air combat Strike fighter

wing)

Contractor Hawker Siddeley McDonnel McDonnel Aermacchi British Dassault Breguet Grumman European Lockheed

Power plant 1  RR Pegasus 2  P&W F100 2  P&W F400 1  Piaggio/RR 1  RR Adour 1  SNECMA 2  GE F110–400 2  Eurojet 2  GE F404

turbofan turbofans with turbofans with Viper 632–43 Mk 151 M53–5 turbofan turbofans with EJ200 turbofans

Thrust (per reheat reheat turbojet with reheat reheat

Table 10.2 Continued

Model A–10 Thunderbolt C 130 Hercules C–5A/B Galaxy B–2 Spirit (Stealth) B–52 Stratofortress B–1B Lancer U–2 E–4B TU–95 Bear

service

Role Ground force Heavy transport Strategic airlift Multi-role heavy Heavy bomber Heavy bomber High altitude National Emergency Long-range

aircraft Post

Contractor Fairchild Co Lockheed Lockheed Northrop Boeing Rockwell Lockheed Boeing Tupolev

Power plant 2  GE TF–34 4  Allison T56 4  GE TF–39 4  GE F–118 8  PW J57 4  GE F–101 1  PW J75 4  GE CF6 4  Kuznetsov

Thrust (per 4079 kg (9 065 lb) 3208 kW) 18 450 kg 7847 kg 6187 kg 13 500 kg (29 700 lb) 7650 kg 23 625 kg (52 500 lb) 11 190 kW

engine) 4300 hp (41 000 lb) (17 300 lb) (13 750 lb) with reheat (17 000 lb) (15 000 hp)

Speed (sea level) Ma 0.56 Ma 0.57 Ma 0.72 High subsonic Ma 0.86 Ma 1.2 Ma 0.57 Ma 0.6 870 km/h

156 Aeronautical Engineer’s Data Book

10.1.2 Flaps

Trailing and leading edge flaps change the effective camber of the wing, thereby increas­ing lift Popular trailing edge types are simple, slotted, double slotted and Fowler flaps (Figure 10.3) Leading edge flaps specifically increase lift at increased angle of incidence and tend to

be used in conjunction with trailing edge flaps Popular types are the simple hinged type and slotted type

Advanced design concepts such as the

mission adaptive wing utilize the properties of

modern materials in order to flex to adopt different profiles in flight, so separate flaps and slats are not required Another advanced

concept is the Coanda effect arrangement, in

which turbofan bypass air and exhaust gas is blown onto the upper wing surface, changing the lift characteristics of the wing

10.1.3 Cabin design

Aircraft cabin design is constrained by the need

to provide passenger areas and an underfloor cargo space within the confines of the standard tube-shaped fuselage This shape of fuselage remains the preferred solution; concept designs with passenger areas enclosed inside a ‘flying wing’ type body are not yet technically and commercially feasible Double-deck cabins have been used on a small number of commer­cial designs but give less facility for cargo carry­ing, so such aircraft have to be built as a family, incorporating cargo and ‘stretch’ variants (e.g the Boeing 747) ‘Super-jumbos’ capable of carrying 1000+ passengers are currently at the design study stage

Figure 10.4 shows typical cabin design variants for current airliner models The objec­tive of any cabin design is the optimization of the payload (whether passengers or freight) within the envelope of a given cabin diameter Table 10.1 lists comparisons of passenger and freight capabilities for a selection of other aircraft

157 Aircraft design and construction

Plain flap Split flap

S

S

Shroud lip Shroud

Shroud

Airflow through slot Fowler flap Single slotted flap

δf Foreflap Mainflap Double slotted flap

High velocity air stream sticks to surface and changes the lift characteristic

shape

Airfoil 'flexes' to change

Upper surface blowing

'Mission adaptive' wing

Fig 10.3 Types of flaps

10.1.4 Ground service capability

Fuselage design is influenced by the ground servicing needs of an aircraft Ground servicing represents commercial ‘downtime’ so it is essential to ensure that as many as possible of the ground servicing activities can be carried

158 Aeronautical Engineer’s Data Book

148 in

49.2 in 56.3 in 155.5 in

1.8 ft

19 in

84 in 2.1 ft

Typical A320 cabin layouts

Fig 10.4 Civil airliner cabin variants

out simultaneously, i.e the service vehicles and facilities do not get in each others’ way Figure 10.5 shows a general arrangement

10.1.5 Fuselage construction

Most aircraft have either a monocoque or monocoque fuselage design and use their outer skin as an integral structural or load carrying member A monocoque (single shell) structure

semi-is a thin walled tube or shell which may have stiffening bulkheads or formers installed

159 Aircraft design and construction

Electrical

power

Bulk cargo belt loader Fuel truck Galley/cabin

service

Bulk cargo train Lavatory

Galley/cabin service

service Tow

tractor

Portable Passenger boarding

Lavatory water truckbridge

service Engine Ground air

air start conditioning

Fig 10.5 Airliner ground services

within The stresses in the fuselage are trans­mitted primarily by the shell As the shell diameter increases to form the internal cavity necessary for a fuselage, the weight-to-strength ratio changes, and longitudinal stiffeners are added This progression leads to the semi-monocoque fuselage design which depends primarily on its bulkheads, frames and formers for vertical strength, and longerons and stringers for longitudinal strength Light general aviation aircraft nearly all have

‘stressed-skin’ construction The metal skin exterior is riveted, or bolted and riveted, to the finished fuselage frame, with the skin carrying some of the overall loading The skin is quite strong in both tension and shear and, if stiff­ened by other members, can also carry limited compressive load

10.1.6 Wing construction

General aviation aircraft wings are normally either strut braced or full cantilever type, depending on whether external bracing is used

to help transmit loads from the wings to the fuselage Full cantilever wings must resist all

Table 10.3 Indicative material properties: metallic alloys

R m MN/m 2 F tu ksi R m MN/m 2 F tu ksi E GN/m 2 E t psi  10 6  kg/m 3 e w lb/in 3

Table 10.4 Indicative material properties: composites

Table 10.5 General stainless steels – basic data

Stainless steels are commonly referred to by their AISI equivalent classification (where applicable)

AISI Other classifications Type 2 Yield F ty [(R e ) MPa] Ultimate [(R m ) MPa] E(%) HRB %C %Cr % others 1

164 Aeronautical Engineer’s Data Book

loads with their own internal structure Small, low speed aircraft have straight, almost rectan­gular, wings For these wings, the main load is

in the bending of the wing as it transmits load

to the fuselage, and this bending load is carried primarily by the spars, which act as the main structural members of the wing assembly Ribs are used to give aerodynamic shape to the wing profile

10.2 Materials of construction

The main structural materials of construction used in aircraft manufacture are based on steel, aluminium, titanium and composites Modern composites such as carbon fibre are in increasing use as their mechanical and temper­ature properties improve Tables 10.3 and 10.4 show indicative information on the properties

of some materials used Advanced composites can match the properties of alloys of aluminium and titanium but are approxi­mately half their weight Composite material specifications and performance data are manufacturer specific, and are highly variable depending on the method of formation and lamination Composite components in themselves are costly to manufacture but overall savings are generally feasible because they can be made in complex shapes and sections (i.e there are fewer components needing welding, rivets etc.) Some aircraft now have entire parts of their primary struc­ture made of carbon fibre composite Stainless steel is used for some smaller and engine components Table 10.5 gives basic data on constituents and properties

10.2.1 Corrosion

It is important to minimize corrosion in aeronautical structures and engines Galvanic corrosion occurs when dissimilar metals are in contact in a conducting medium Table 10.6 shows the relative potentials of pure metals

165 Aircraft design and construction

Table 10.6 The electrochemical series

Lithium (Li) – Volts

Metals higher in the table become cathodic and are protected by the (anodic) metals below them in the table

10.3 Helicopter design

10.3.1 Lift and propulsion

Helicopters differ from fixed wing aircraft in that both lift and propulsion are provided by a single item: the rotor Each main rotor blade acts as slender wing with the airflow producing

a high reduction in pressure above the front of the blades, thereby producing lift Although of high aspect ratio, the blades are proportion­ately thicker than those of fixed wing aircraft, and are often of symmetric profile Figure 10.6 shows the principle of helicopter airfoil opera­tion

10.3.2 Configuration

Figure 10.7 shows the four main configurations used The most common is the single main and tail rotor type in which the torque of the main rotor drive is counteracted by the lateral force produced by a horizontal-axis tail rotor Twin tandem rotor machines use intermeshing, counter-rotating rotors with their axes tilted off the vertical to eliminate any torque imparted to the helicopter fuselage In all designs, lift force

is transmitted through the blade roots via the

166 Aeronautical Engineer’s Data Book

Tip-path plane Tip-path plane

Axis of rotation

Fig 10.6 Helicopter principles: lift and propulsion

rotor hub into the main drive shaft, so the helicopter effectively hangs on this shaft

10.3.3 Forward speed

The performance of standard helicopters is constrained by fixed design features of the rotat­ing rotor blades In forward flight, the ‘retreat­ing’ blade suffers reversed flow, causing it to lose lift and stall when the forward speed of the helicopter reaches a certain value In addition the tip speed of the advancing blades suffers shock-stalls as the blades approach sonic veloc­ity, again causing lift problems This effectively limits the practical forward speed of helicopters

to a maximum of about 310 km/h (192 mph)

10.3.4 Fuel consumption

Helicopters require a higher installed power per unit of weight than fixed wing aircraft A large proportion of the power is needed simply

167 Aircraft design and construction

Single main and tail rotor

(general purpose helicopter)

Fig 10.7 Helicopter configurations

to overcome the force of gravity, and overall specific fuel consumption (sfc) is high Figure 10.8 shows how sfc is gradually being reduced

in commercial helicopter designs

168 Aeronautical Engineer’s Data Book

10.4 Helicopter design studies

Helicopter design studies follow the general pattern shown in Figure 10.9 The basis of the procedure is to start with estimates of gross weight and installed power based on existing helicopter designs First estimates also have to

be made for disc loading and forward flight drag The procedure is then interative (as with the fixed wing design study outlined in Chapter 9) until a design is achieved that satisfies all the design requirements

169 Aircraft design and construction

Estimate Estimate gross weight power

Mission time Fuel capacity

Compare

Payload and crew weights

Check gross weight

First estimate of disc loading

Main rotor tip speed

Check First estimate of forward flight drag

Speed and climb performance requirements Installed

power

Select engine(s)

Recalculate fuel requirement

Fig 10.9 Helicopter design studies: the basic steps

10.4.1 Helicopter operational profile

For military helicopters, the operational profile

is frequently termed mission capability The

relatively short range and low endurance of a helicopter, compared to fixed wing aircraft, means that the desired mission profile has a significant influence on the design Figure 10.10 shows a typical military mission profile

Table 10.7 Helicopter comparisons

service

991 kW (1328 hp)

708 kW (952 hp)

1044 kW (1400 hp)

1160 kW (1556 hp)

1634 kW (2190 hp)

3536 kg (7795 lb)

2529 kg (5575 lb)

2755 kg (6073 lb)

3300 kg (7275 lb)

4550 kg (10 030 lb)

6400 kg (14 110 lb)

4100 kg (9039 lb)

4310 kg (9500 lb)

5800 kg (12 787 lb)

10 800 kg (23 810 lb

280 km/h (174 mph)

259 km/h (161 mph)

277 km/h (172 mph

280 km/h (174 mph)

310 km/h (193 mph)

366 m/min (1200 ft/min)

637 m/min (2090 ft/min)

375 m/min (1230 ft/min)

600 m/min (1970 ft/min)

600 m/min (1970 ft/min)

Mil Mi–26 Heavy transport

helicopter

1979 2 Lotaren

turboshaft

8504 kW (11 400 hp)

28 200 kg (62 169 lb)

49 500 kg (10 9127 lb)

295 km/h (183 mph)

9242 kg (20 378 lb)

20 866 kg (46 000 lb)

306 km/h (190 mph)

878 m/min (2880 ft/min) Bell/Boeing

14 800 kg (32 628 lb)

VTOL:

21546 kg (47 500 lb) STOL:

629 km/h (391 mph)

–

24 948 kg (5500 lb) EH101 Merlin Multi-role

helicopter

1987 3 GE turboshaft 1522 kW

(2040 hp)

9072 kg (20 000 lb)

14 600 kg (32 188 lb)

309 km/h (192 mph)

–

Cruise to target zone

Section 11

Airport design and compatibility

Airports play an important role in the civil and military aeronautical industries They are part

of the key infrastructure of these industries and, because of their long construction times and high costs, act as one of the major fixed

constraints on the design of aircraft

11.1 Basics of airport design

11.1.1 The airport design process

The process of airport design is a complex compromise between multiple physical, commercial and environmental considerations Physical facilities needed include runways, taxiways, aprons and strips, which are used for the landing and take-off of aircraft, for the manoeuvring and positioning of aircraft on the ground, and for the parking of aircraft for loading and discharge of passengers and cargo Lighting and radio navigation are essential for the safe landing and take-off of aircraft These are supplemented by airfield markings, signals, and air traffic control facilities Support facili­ties on the airside include meteorology, fire and rescue, power and other utilities, mainte­nance, and airport maintenance Landside facilities are the passenger and cargo terminals and the infrastructure system, which includes parking, roads, public transport facilities, and loading and unloading areas At all stages of

the design process, the issue of aircraft compat­

ibility is of prime importance – an airport must

be suitable for the aircraft that will use it, and vice versa

174 Aeronautical Engineer’s Data Book

11.1.2 Airport site selection

The airport site selection process includes several stages of activity Table 11.1 shows the main ‘first stage balance factors’

Table 11.1 Airport site selection: ‘first stage balance factors’

• Flat area of land (up to • Should not impinge on 3000* acres for a large areas of natural beauty facility) • Sufficiently far away

• Sufficiently close to

population centres to

allow passenger access

from urban centres to minimize the adverse effects of noise etc

*Note: Some large international airports exceed this figure (e.g Jeddah, Saudi Arabia and Charles de Gaulle, Paris)

11.1.3 Operational requirements – ‘rules of thumb’

There is a large variation in the appearance and layout of airport sites but all follow basic ‘rules

of thumb’:

• The location and orientation of the runways are primarily decided by the requirement to avoid obstacles during take-off and landing procedures 15 km is used as a nominal

‘design’ distance

• Runway configuration is chosen so that they will have manageable crosswind compo­nents (for the types of aircraft being used) for at least 95% of operational time

• The number of runways available for use at

any moment determines the operational

capacity of the airport Figure 11.1 shows

common runway layouts Crosswind facility

is achieved by using either a ‘crossed’ or

‘open or closed vee’ layout

• Operational capacity can be reduced under IFR (Instrument Flying Rules) weather conditions when it may not be permissible

to use some combinations of runways simul­taneously unless there is sufficient separa­tion (nominally 1500+ metres)