Category AIRCRAF DESIGN

The load on the wheels determine the tire size. Wheel load is the aircraft weight dis­tributed over the number of wheels. The aircraft CG position could vary depending on the extent of payload and fuel-load distribution; therefore, both the forward – most and aftmost CG positions must be considered. (Table 7.4 provides an idea of the A380 load.)

As soon as the preliminary undercarriage information is known from the methodology described in this chapter, aircraft weights and the CG can be estimated through the formal procedure described Chapter 8.

Estimating the aftmost CG with the angle в & 15 coinciding with 40% of the MAC gives a preliminary idea of the main-wheel position relative to the wing. The wing position relative to the fuselage could change when the formal weight and CG estimations are determined after the wing is sized. In that case, the wheel-load calculation must be revised. For transport aircraft design, at this stage, the forward – most CG is 20 to 25% of the MAC ahead of the aftmost CG. For the nontrans­port category, including combat aircraft design, at this stage the forwardmost CG is 15% of the MAC ahead of the aftmost CG. The MTOW rather than the MTOM is used in the computation because the load is a force. (A simplified approach is to divide the main – and nose-wheel loads as 90 and 10% distribution, which has a
reasonable result, but the author recommends making the formal estimation at the beginning.)

Linear distance is represented by l with associated subscripts; R represents reac­tion forces. For more than one wheel, the load would then be divided accordingly. The force balance gives:

MTOW = 2 x Rmain + Rnose (7.1)

To compute the maximum main-wheel load at the aftmost CG position, take the moment about the nose wheel. The moment equilibrium equation becomes:

Ibase x Rmain = Inrearcg x MTOW

or Rmain = (Inrearrg x MTOW)/Ibase (7.2)

The load per strut on the main wheel is:

LM = Rmain/number of struts (7.3)

To compute the maximum nose-wheel load at the forwardmost CG position, take the moment about the main wheel. The moment equilibrium equation becomes:

Ibase x Rnose = Imrorwardjcg x MTOW

or RNOSE = (lM-FORWARD-CG x MTOW)/lBASE (7.4)

The nose wheel typically has one strut.

Ensure that the load at the nose gear is not too high (i. e., no more than 20% of the MTOW) to avoid a high elevator load to rotate the aircraft for liftoff at takeoff. Also, it must not be too low – that is, not less than 8% of the MTOW; otherwise, there could be steering problems.

For more than one wheel per strut, the load per tire is calculated based on what each tire would produce on the same runway pavement stress at the same tire pres­sure as a single wheel. This is the equivalent single wheel load (ESWL) because loads are not shared equally when arranged side by side, unlike tandem arrange­ments. Wheel arrangements determine the ESWL as given here based on statistical means. Readers may consult the references for more details on other types of wheel arrangements.

The tandem twin wheel is:

ESWL = load per strut/2 (7.5)

The side-by-side twin wheel is:

ESWL = load per strut/(1.5 to1.33) (this book uses 1.5) (7.6)

The tandem triple wheel is:

ESWL = load per strut/3 (7.7)

The side-by-side triple wheel is:

ESWL = load per strut/(1.5 to1.33) (this book uses 1.5) (7.8)

Table 7.1. Vertical speed

VVert, = < 12 fps – FAR 23 (semi-empirical formula for exact rate, nl = 3)

VVert, = < 12 fps – FAR 25 (nl = 2)

VVert, = < 10 fps – Military transport (nl = 2)

VVert, = < 13 fps – Military trainer (nl = maximum 5)

VVert, = < 17 fps – Military land-based combat aircraft (nl = maximum 6)

VVert, = < 22 fps – Military naval (aircraft-carrier)-based combat aircraft (nl = 8)

The twin tandem is

ESWL = load per strut/(3 to 2.67) (7.9)

The main-wheel loads are calculated based on the aftmost CG position and the nose – wheel loads are based on the forwardmost CG position. The dynamic load on the wheel is 50% higher than the static load.

In its elementary representation, the undercarriage system acts as a spring-mass sys­tem, shown in Figure 7.12. Shock absorption is accomplished by its main spring and, to a smaller extent, by the tire pneumatics. Both spring and tire deflect under load. The oleo system acts as a damper; that is, it dissipates kinetic energy of vertical velocity. The strut can act as a spring for the lateral load of the ground friction.

The length of the strut is influenced by the extent that its shock absorber is compressed to the maximum. The minimum strut length is when both tire and shock

Figure 7.12. Undercarriage as a spring-mass system

absorber collapse simultaneously, yet provide sufficient ground clearance for flaps fully extended (see Figure 7.8). The most critical situation for flap clearance is when the main wheel has collapsed and the nose wheel is at the fully extended position. (In a practical situation, the nose wheel tire would also remain deflected under load, but the margin of the fully extended position is safer.) The flap trailing edge is at its lowest at aircraft rotation for liftoff. A simultaneous failure of the tire and shock absorber after decision speed V1 (see Chapter 13) would force the pilot to continue with the aircraft rotation and liftoff.

During landing, as lift is depleting with speed reduction, more aircraft weight is reacting at the ground contact, which increases the spring load of the strut. The energy is stored in the spring. On brake application, the kinetic energy of the aircraft is absorbed by the brake pads, increasing temperature. If the limits are crossed with rapid deceleration, a fire hazard exists.

Aircraft designers must ensure that an aircraft can turn in the specified radius within the runway width (Figure 7.10). Turning is achieved by steering the nose wheel (i. e., the maximum nose wheel turn is « 78 deg) activated by the pilot’s foot pedal. There is a slip angle and the effective turn would be approximately 75 deg. Pressing the left pedal would steer the nose wheel to the left and vice versa. The tightest turn is achieved when asymmetric braking and thrust (for a multiengine aircraft) are applied. The braked wheel remains nearly stationary. The center of the turn is slightly away from the braked wheel (see Figure 7.10) and the steered nose wheel guides the turn. The radius of the turn is the distance between the nose wheel and the center of the turn. Checks must be made to verify that the aircraft nose, outer wing tip, and outer H-tail tip are cleared from any obstruction. If the inner wheel were not braked, the turning radius would be higher. Turning is associ­ated with the centrifugal force at the CG and side force at the turning wheels.

A tail wheel aircraft turning poses a special problem for “ground looping,” par­ticularly when the aircraft is still at speed after landing. If the tail of the aircraft swings out more than necessary in an attempt to keep the aircraft straight using pedal-induced turns, then the centrifugal force of the turn could throw the air­craft rear end outward to the point where the forward-momentum component could move outside the wheel track. This results in instability with an uncontrolled ground loop, which can tilt the aircraft to the point of tipping if the over-turn angle в is breeched.

Figure 7.11. Wheel arrangements

7.3 Wheels

As an aircraft weight increases, the runway must bear the reaction and retain integrity to keep the vehicle’s field performance safe. Heavy commercial transport aircraft are intended to operate from a prepared runway (i. e., Types 2 and 3; see Section 7.10) to stay within the pavement strength; the load per wheel is restricted by distributing the total over several wheels. Various arrangements for more than one wheel per strut style are shown in Figure 7.11. Aircraft and undercarriage designers must plan for the number of struts, number of wheels per strut, and tire spacing and pressure (which determine the size) to distribute the load. As the aircraft MTOM increases, so does the number of wheels required, as well as considerations for stow­ing and articulation for retraction.

The fundamental wheel arrangements are single, twin, triple, and quadruple on a bogey. Wheel arrangements higher than a quadruple are not seen. The next level is their placement in a dual row as a single tandem, twin tandem (i. e., four wheels), triple tandem (i. e., six wheels), and so forth. The A380 wheel-arrangement model is shown in Figure 7.11. Figure 7.1 shows the wheel bogey of the world’s largest aircraft (i. e., the Antanov 225) with twin wheels per strut, for a total of seven struts.

There are three wheel positions, as shown in Figure 7.8. The application logic for the various types of aircraft is the same. The three positions are as follows:

1. Normal Position. This is when the aircraft is on the ground and the under­carriage carries the aircraft weight with tires deflected and the spring com­pressed.

2. Free Position. When an aircraft is airborne, the undercarriage spring is then relieved of aircraft weight and extends to its free position at its maximum length. Stowage space is based on the undercarriage in a free but articulated position.

3. Failed/Collapsed Position. This is the abnormal case when the spring/oleo col­lapsed as a result of structural failure, as well as tires deflated with loss of air pressure. This is the minimum undercarriage length.

The failed position of the aircraft on the ground is the most critical design driver in determining the normal length of the undercarriage strut. Following are design considerations for the failed positions:

1. Nose Wheel Failed. The nose will drop down and the length of the collapsed nose wheel should still prevent the propeller from hitting the ground with adequate clearance.

2. Main Wheel Failed. There are two scenarios:

(a) When one side fails, the wing tilts to one side and it must not touch the ground.

(b) If both sides collapse (the most critical situation is when the aircraft rotates for liftoff at the end of the takeoff ground run), it must be ensured that the fully extended flap trailing edges have adequate ground clearance.

Figure 7.9 depicts an important design consideration for fuselage clearance angle y , at aircraft rotation for liftoff, when the CG should not go behind the wheel contact point. Both civil and military aircraft types are shown in the figure. The angle в is the angle between the vertical and the line joining the wheel contact point with the ground and the aircraft CG. Ensure that в is greater than y; otherwise, the CG position will go behind the wheel contact point. Keep в greater than or equal to 15 deg. The fuselage clearance angle, y, must be between 12 and 16 deg to reach CLmax at aircraft rotation. The fuselage upsweep angle for clearance is discussed in Section 4.7.3 and it is revised here after the undercarriage layout is completed. Figure 7.9 corresponds to the worked-out examples.

A tire expands as the fabric stretches during service. It also expands on account of heat generated during ground operations. It keeps spinning (further enlargement occurs due to centrifugal force of spinning) within the stowage space immediately after retraction. Stowage space within an aircraft should be of the minimum volume occupied by the retracted undercarriage with some clearance to avoid any interfer­ence that may occur. Enough cavity space should be inside the aircraft structure to accommodate tire expansions. Stowage space is dictated by the articulated mech­anism for retraction from its unloaded free position. Semi-empirical relations gov­ern the clearance gap to accommodate retraction. As mentioned previously, this book assumes that aircraft designers are in a position to offer proper stowage space with adequate clearances. This book does not discuss stowage-space computation. For thin-wing combat aircraft, stowage must be within the tightly packed fuselage, where space is limited.

Unless there is a breakthrough innovation (typically associated with unconven­tional new designs beyond the scope of this book) on retraction kinematics, the state-of-the-art undercarriage design has been established to maximize compact­ness. This book addresses articulation in its simplest form. The author recommends using CAD animation to check retraction kinematics and storage space during the second-term coursework.

Retraction is required for aircraft operating at more than 150 to 200 knots. A rapid increase in drag starts building up for speeds of more than 150 knots. There are basically three situations, as shown in Figure 7.6:

1. No Retraction. The fixed undercarriage is primarily for smaller aircraft or larger aircraft that have a high wing and are operating at low speed (e. g., the Twin Otter and the Shorts 330).

2. Partial Retraction (Kneeling Position). A large wheel bogey with restricted stowage space would have to sacrifice full retraction; however, partial retrac­tion helps considerably to reduce drag.

3. Full Retraction. Stowage space must be provided for a wheel bogey (i. e., for higher-speed aircraft).

fuselage bottom

AJT retraction kinematics

Figure 7.7. Undercarriage stowage space and retraction

Provision for stowage must be made early in the conceptual design phase. Only the space provision, after consultation with structural and undercarriage designers, is sufficient at this early stage of the project. Typical extended and retracted posi­tions of civil and military type aircraft are shown in Figure 7.7. Following are areas where the undercarriage can be stowed:

1. In the Wing. If wing thickness is sufficient, then a maximum of twin wheels can be retracted. Provision for the wing recess is made as early as possible in the design phase. For a thinner wing, if the strut is mounted on the wing, it can go through the wing recess and the wheel to reach the fuselage stowage space (e. g., Learjet 45; although it has a single wheel, the wing thickness does not have sufficient space).

2. In the Fuselage. This is the dominant pattern for a large undercarriage because the fuselage underbelly could provide generous stowage space. If not, then it can be kept outside encased by a fairing that appears as a bulge (e. g., Antanov 225). For fighter aircraft with a very thin wing, the entire undercarriage is mounted on and retracted within the fuselage (e. g., the F104). The coursework example is a high-wing aircraft (see Figure 7.7) and the undercarriage is stowed in the fuselage.

3. In an under-the-Wing Nacelle. High-wing turboprop aircraft have a long strut; therefore, stowing the undercarriage in the nacelle (see Figure 10.19) slung under the wing reduces the strut length (e. g., the Fokker27 and Saab340).

Once the gear is extended, it must be locked to avoid an inadvertent collapse. A schematic retraction path of an AJT also is shown in Figure 7.7. Retraction kine­matics is not addressed in this book. It is assumed that during the conceptual design phase, designers have succeeded in retraction within the stowage space provided by

the aircraft engineers. See the references for more details on undercarriage retrac­tion kinematics.

The position of the aircraft CG is a most important consideration when laying out wheel locations relative to an aircraft. Basically, the undercarriage consists of wheels on struts attached to aircraft points. The geometric parameters in placing wheels relative to the aircraft CG position are shown in Figure 7.3, along with the basic nomenclature of related parameters. The geometric definitions are as follows:

Wheel Base: The distance between the front and rear wheel axles in the vertical plane of symmetry

Wheel Tread or Wheel Track: The distance between the main wheels in the lat­eral plane of the aircraft

The wheel base and wheel track determine the aircraft turning radius (see Sec­tion 7.7) on the ground. The forwardmost aircraft CG position relative to the wheel base and wheel track determines the aircraft over-turn characteristics. The over­turn angle, в, is the maximum angle for a tilted aircraft with the CG on top of a main wheel; beyond that, the aircraft would turn over on its side. Determination of the angle в is shown in Figure 7.3. Over-turn tipping is not exactly around the X-axis (i. e., sideways) when a low-wing aircraft could have a wing tip touching the ground before в is reached. The tipping occurs about the axis joining the nose-wheel and main-wheel ground contact point, when the wing LE is likely to hit the ground.

Figure 7.3. Aircraft CG position rela­tive to the undercarriage layout

It is better to maintain a lower angle в to avoid an aircraft turning over; the value depends on the airfield surface, and the tendency increases with higher sideways ground friction. For simplification yet still representative, typical values used in this book follow (see the references for more details). For a paved runway, keep the angle в less than 60 deg; for an unprepared field, it should be less than 50 deg. There are aircraft with в = 35. Most of the aircraft have a в between 40 and 50 deg.

An aircraft also can tip backwards if its rearmost CG goes behind the main wheel of a tricycle-type undercarriage; it can tip forward if its CG is in front of the main wheels of a tail-wheeled aircraft (Figure 7.4).

Definitions of the related parameters concerning wheel and strut provided in Figure 7.5 are more pertinent to the nose wheel ahead of the aircraft CG. These are not critical items at the conceptual design phase and can be omitted from the coursework. In the industry, these parameters are considered at an early stage.

1. Caster or Rake Angle. Angle between the spindle axis and the vertical line from the ground contact point of the swivel axis.

2. Caster Length. Perpendicular distance from wheel contact point to ground and spindle axis.

3. Trail. Distance from wheel contact point to ground and spindle-axis contact point to ground.

4. Offset. Perpendicular distance from wheel axis and spindle axis.

5. Loaded Radius. Distance from wheel axis to ground contact point under static loading.

6. Rolling Radius. Distance from wheel axis to ground contact point under dynamic loading.

Wheel alignment and wheel camber (i. e., the tilt from being vertical) are impor­tant issues for wheel positioning, which can be omitted from the coursework prelim­inary aircraft layout.

The undercarriage has an attachment point to the aircraft and can have more than one strut (i. e., support point). Chart 7.1 classifies various types in an elementary way, as if each support point has one strut with one wheel, with designations similar to a common bicycle. For example, the Airbus 380 aircraft has five support points (i. e., one nose wheel, two fuselage-mounted wheels, and two wing-mounted wheels) (see Figure 7.11) and many wheels and struts.

A nose wheel-type tricycle undercarriage is, by far, the dominant type, which is the type addressed in this book. The tail wheel type (i. e., fixed undercarriage) causes less drag, which can increase aircraft speed by 2 to 3%. However, on the ground, the raised nose impairs forward visibility and is more prone to “ground looping”

(described in Section 7.7). Currently, tail wheels are adapted for some lighter air­craft.

The simplest form of undercarriage was the earliest rigid axle type not in use any longer. Some form of shock absorber is favored nowadays. Struts with shock absorbers also are designed in many variations, as shown in Figure 7.2. When one strut has more than one wheel, it is seen as a bogey, as shown in the figure. There is a range of bogey designs not included in the figure.

7.1 Overview

Chapter 6 illustrates how to arrive at a preliminary aircraft configuration of a new project starting from scratch, with the expectancy of satisfying the market specifica­tion. To progress further, the next task is to lay out the undercarriage (also known as the landing gear) position relative to the aircraft CG, which is accurately estab­lished in Chapter 8. This chapter addresses the undercarriage quite extensively but not the detailed design; rather, it focuses on those aspects related to undercarriage layout and sizing during the conceptual study phase. More details on undercarriage design are in the cited references.

This chapter first introduces the undercarriage to serve vehicle ground handling, followed by basic definitions, terminologies, and information used in the design process and integration with an aircraft. Finally, methodologies for layout of the undercarriage and tire sizing are presented to complete the aircraft configuration generated thus far. Considerable attention is required to lay out the undercarriage position and to determine tire size and geometric details to avoid hazards dur­ing operation. This book limits the topic to the fundamentals to the extent of the requirements for positioning the undercarriage and sizing the wheels and tires. These fundamentals are shown schematically in the three-view aircraft drawings. Relevant information on wheel tires is also presented in this chapter.

The undercarriage is a complex and heavy item and, therefore, expensive to manufacture. It should be made right the first time. Aircraft designers should know the operational basics, leaving the details to those who specialize in the undercar­riage as a system that is integrated with an aircraft as a subsystem. Aircraft designers consult with undercarriage specialists during the conceptual stage.

The location of the aircraft CG is important in laying out the undercarriage. Ini­tially, the CG position is guessed from statistics and past experience. Once the basics of the undercarriage are explained, Chapter 8 addresses aircraft weight estimation and CG location. An iterative assessment follows to revise the undercarriage posi­tioning due to the differences, between the guessed and estimated CG location. The final iteration occurs after the aircraft is sized in Chapter 11.

The undercarriage, as a major component, creates a considerable amount of drag in its extended position during flight. Therefore, its retraction within the aircraft mould lines is necessary to minimize drag. Evolution shows that early designs of a tail-dragging type of undercarriage virtually disappeared and have been replaced by the nose-wheel tricycle type. It is interesting that the first nose wheel – design undercarriage appeared in 1908 on a Curtiss aircraft. The blowout of tires during takeoff and landing is dangerous; the Concorde crash due to a tire bursting is extremely rare but designers must learn from that situation.

In the past, aircraft manufacturers handled the undercarriage design in a verti­cally integrated factory setup. Today, its complexity has created specialized orga­nizations (e. g., Messier of France and Dowty of the United Kingdom) that are dedicated to undercarriage design, thereby making its management and integration more efficient and resulting in better designs. However, for smaller aircraft in the class of club and private use, manufacturers can make their own undercarriages, and most of them are of the fixed type.

7.1.1 What Is to Be Learned?

This chapter covers the following topics:

Introduction to the undercarriage as a system and its functions Types of undercarriage

Undercarriage layout relative to the CG, nomenclature, and def­initions

Undercarriage retraction and stowage issues Undercarriage design drivers and considerations Undercarriage performance on the ground – turning of an air­craft

Types of wheel arrangements

Load on wheels, shock absorber, and deflection

Runway pavement types

Tire nomenclature, designation, and types

Tire friction with ground, rolling, and braking coefficients

Undercarriage layout methodologies

Worked-out examples

Miscellaneous considerations

Undercarriage and tire data

7.1.2 Coursework Content

Readers will make a comprehensive layout of the nose wheel-type tricycle under­carriage and position it to fit the aircraft configured in Chapter 6. The first task is to ensure that the layout is safe and satisfies all of its functionality. The wheel and tire are then sized to complete the layout. This section requires computational work when the aircraft CG position is still unknown. The author recommends that readers prepare spreadsheets for repeated calculations because iterations will ensue after the CG is established and the aircraft is sized.

7.2 Introduction

The undercarriage, also known as the landing gear, is an essential aircraft compo­nent for the following functions: (1) support the aircraft when in place or towed, (2) taxi and steer on the ground using an aircraft’s own power, (3) the takeoff run, and (4) landing and braking on the runway. For these reasons, the author prefers the term undercarriage rather than landing gear because the functions encompass more than mere landings. Once an aircraft is airborne, the undercarriage becomes redun­dant – an appendage that causes drag that can be minimized through retraction.

The undercarriage is seen as a subsystem consisting of a strong support spin­dle (i. e., strut) with a heavy-duty shock absorber to tackle heavy landings due to a rapid descent, whether inadvertently or on the short runway length of an aircraft – carrier ship. The undercarriage has a steering mechanism with shimmy control (i. e., control of dynamic instability; wheel oscillation about the support shaft and strut axis). The wheels have heavy-duty brakes that cause the temperature to reach high levels, resulting in a potential fire hazard. Heavy braking requires heavy-duty tires, which wear out quickly and are frequently replaced with new ones. Most undercar­riages are designed to retract; the longer ones have articulated folding kinematics at retraction. The undercarriage retraction mechanism has hydraulic actuation; smaller aircraft may get by with an electrical motor drive.

The undercarriage is a complex system – the main undercarriage of the world’s largest aircraft (i. e., Antanov 225) is shown in Figure 7.1 (note the relative size of the people in the photograph). It is a bogey system (see Section 7.3) carrying 7 struts (i. e., support shafts with shock absorbers) per side, each carrying 2 wheels for a total of 32 wheels when the 4 nose wheels are added (2 x 2 x 7 + 4 = 32).

The undercarriage stowage bay within the aircraft is compactly sized to the extent that articulation allows. The stowage bay is located in the wing and/or the fuselage, or sometimes in the wing-mounted nacelles, depending on the realistic details of the design considered by aircraft designers at the conceptual stage. It is a challenging task for structural designers to establish a satisfactory design that inte­grates all the relationships and functionality of the undercarriage with the airframe. The author recommends keeping the undercarriage layout design as simple as pos­sible for better reliability and maintainability without using too much of the articu­lation and/or stowage space in an aircraft. Reference 7.4 provides more details.

Undercarriage

2-point 3-point З-point 4-point 5-point

(bicycle) (tailwheel) (tricycle)

Harrier Piper Cub Learjet45 A380

Chart 7.1. Undercarriage types (land-based)

A large aircraft is heavy enough to damage a metal runway; therefore, its weight is distributed over many wheels on a bogey system, which itself has articulation for retraction. The undercarriage mass can encompass as much as 7% (typically 4 to 5%) of the MTOM for large aircraft, it can weigh up to 3 tons with a corresponding cost of up to 5% of the aircraft total price, and the drag can be 10 to 20% of the total aircraft drag, depending on the size – smaller aircraft have a higher percentage of drag. For small, low-speed aircraft with a low-cost fixed undercarriage without a streamlined shroud, the drag could be as high as nearly a third of the total aircraft drag.

The undercarriage design should be based on the most critical configuration in the family of derivative aircraft offered. Generally, it is the longest one and there­fore the heaviest, requiring the longest strut to clear the aft fuselage at maximum rotation. For the smaller version of the family, minor modifications assist in weight savings, yet retain a considerable amount of component commonality that reduces cost. In general, tires are the same size for all variants.

Other special types of undercarriages are not addressed herein. Today, all “fly­ing boats” are amphibians with a retractable undercarriage. Undercarriage types are classified in the next section. Section 7.15 provides statistics. The Harrier VTOL/STOL and B52 aircraft have a bicycle-type undercarriage. These are diffi­cult decisions for designers because there are no easier options other than the bicy­cle type, which requires an outrigger support wheel to prevent the wing from tipping at the sides. Aircraft with skids are intended for application on snow (the skids are mounted on or replace the wheels) or for gliders operating on grass fields. Some “tail-draggers” get by with using a skid instead of a tail wheel. Special designs use takeoff carts to get airborne; however, landing is another matter.

This extended section of the book can be found on the Web at www. cambridge .org/Kundu and gives a brief overview of today’s military aircraft shapes and their layout arrangements, as shown in the following charts and figures.

Figure 6.15. Falcon F16 fuselage cross-section and layout Figure 6.16. Flight deck (cockpit) layout – military aircraft Figure 6.17. USAF F18 details showing internal structural layout and armament load

Chart 6.2. Phase I, conceptual study: methodology to freezing military aircraft configuration

6.7 Worked-Out Example – Configuring Military Advanced Jet Trainer

This extended section of the book can be found on the Web at www. cambridge .org/Kundu and presents details of worked-out examples of the Advanced Jet

Trainer (AJT). The section is divided into subsections, with a step-by-step discus­sion of workflow. Associated figures and table are listed.

6.12.1 Use of Statistics in the Class of Military Trainer Aircraft

This extended subsection, on the Web at www. cambridge. org/Kundu, includes the following figures.

Figure 6.18. Military trainer aircraft – MTOM

Figure 6.19. Military trainer aircraft wing area and engine size

6.12.2 Worked-Out Example – Advanced Jet Trainer Aircraft (AJT) – Fuselage

This extended subsection, on the Web at www. cambridge. org/Kundu, includes the following figures and table.

Figure 6.20. AJT fuselage layout Figure 6.21. AJT and its CAS variant Table 6.3. Flap setting versus CLmax

6.12.3 Miscellaneous Considerations – Military Design

This subsection, on the Web at www. cambridge. org/Kundu, describes intake, exhaust, and CG position of the AJT.

6.8 Variant CAS Design

This extended section of the book can be found on the Web at www. cambridge .org/Kundu and develops presents details of a worked-out example of a VAS vari­ant of the Advanced Jet Trainer. The section is divided into subsections, each with a step-by-step discussion of workflow, as shown below by their titles. Associated figures are listed.

6.13.1 Summary of the Worked-Out Military Aircraft Preliminary Details

This subsection, on the Web at www. cambridge. org/Kundu, summarizes in tabu­lated form the AJT and the CAS variant configurations and some resulting geomet­ric and weights details.