TABLE OF CONTENTS
LIST OF FIGURES ................................................................................................................. ii LIST OF TABLES ................................................................................................................... ii ABSTRACT............................................................................................................................ iii CHAPTER 1: INTRODUCTION ............................................................................................ 1 1.1. 1.2. 1.3. 1.4. Introductory of the Title ........................................................................................... 1 Objective and Purpose ............................................................................................. 2 Problem Statement and Problem Solving ................................................................ 3 Limitation of the Project .......................................................................................... 4

CHAPTER 2: LITERITURE REVIEW ................................................................................... 5 2.1. 2.2. Research Theory, Ideology and Concept ................................................................. 5 Previous Research and Proposed Project Comparison........................................... 11

CHAPTER 3: METHODOLOGY ......................................................................................... 12 3.1.0 3.2.0. 3.2.1. 3.2.2. 3.2.3. 3.2.4. 3.2.5 Preface................................................................................................................ 12 Research Method................................................................................................ 13 Finite Element Analysis ..................................................................................... 13 Field Test ........................................................................................................... 14 Data Analysis ..................................................................................................... 14 Aircraft Type Description .................................................................................. 15 Current research progress................................................................................... 18

Bibliography .......................................................................................................................... 19

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LIST OF FIGURES

Figure 1: Electrical braking system on bombardier aircraft.......................................................2 Figure 2: Landing gear primary parameter ................................................................................5 Figure 3: Landing gear design flowchart ...................................................................................7 Figure 4: Configuration of tricycle landing gear........................................................................8 Figure 5: Beechcraft F33A Bonanza using tricycle landing gear ..............................................8 Figure 6: Configuration of tail-gear landing gear ......................................................................9 Figure 7: Bush Hawk-XP in the tail wheel configuration ..........................................................9 Figure 8: Multi- bogey landing gear configuration ..................................................................10 Figure 9: Airbus 380 using multi-bogey landing gear .............................................................10 Figure 10: The main flow of research development ................................................................12 Figure 11: Lufthansa Boeing 737-300 .....................................................................................15 Figure 12: Boeing 737-300 scaled 1in:32ft ..............................................................................17 Figure 13: Scale for Boeing 737-300 .......................................................................................17

LIST OF TABLES
Table 1: Boeing 737-300 description ........................................................................................16 Table 2: Overall Progress for this semester ..............................................................................18

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ABSTRACT
An aircraft is in flight and it is ready to land at the airport. But sometimes, the weather is not always great. The aircraft have to land at the airport even though it is on a rain situation. This will make the runaway became wet and slippery. Thus there will be some difference in handling the aircraft to land. In this research, an analysis will be conducted by simulating the wet and dry runaway surface where the aircraft have to land on it. From this research, an observation can be made on the effectiveness of the landing gear to face these different conditions of the surfaces. This research will analyse what is the difference on the landing gear when an aircraft land on dry surfaces and also land on the wet surfaces. This research will determine the landing gear reaction during touchdown and also the time taken for the landing gear to stop. This research will conduct the analysis with some controlled variable to ensure that the data and result recorded during the analysis is constant. From this research also, a conclusion will be deduced on what is the best condition for an aircraft to land. Either on dry surfaces or dry surfaces, lastly this research will be conducted suitable to many aspects such as budget, research time and also the relevancy of the research itself.

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CHAPTER 1: INTRODUCTION

1.1.

Introductory of the Title Landing of an aircraft is one of the most critical times for an aircraft. It‟s

must be in a right procedure to gain a successful landing. In the aircraft itself, landing gear will be the most important part during landing procedure. In landing gear, there will be many systems such as brake, shock absorber, directional manoeuvre on the runaway and tarmac. The landing gear also must be able to withstand high speed condition, heat, friction and also can maintain stability during run out phase of the landing. Landing gear is the structure that supports an aircraft on the ground and allows it to taxi, take-off, and land. The only aircraft part that will be in contact to the ground is landing gear. So the landing gear must be one of the important parts to fully perform in various condition such as in winter, wet condition, crosswind and dry condition. These landing conditions will give different force acting on the landing gear. This project will analyze the reaction of landing gear during landing and proposing the most efficient condition for the landing gear to land. As we know, the condition of runaway also will be varying during landing. There are sometimes the runaway becomes wet, windy and dry. The length of the runaway also can be the factor to the landing gear whether it should brake faster or not. This brake timing also can be different than the force acted to the landing gear itself. Figure one shows an example of braking system used on the landing gear. This figure uses electrical braking system that has been implemented on bombardier aircraft.

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Figure 1: electrical braking system on bombardier aircraft

1.2.

Objective and Purpose

Below is the list of objectives of this research:

1. Analysing the landing gear condition during touchdown. 2. To record the time of landing gear to stop at the end of the runaway. 3. To propose the most efficient condition for an aircraft to land. There are three main objectives in this research which is firstly, „Analysing the landing gear condition during touchdown‟. This first objective is to analyse the force acting on the landing gear in two conditions. The possibility of the landing gear to skid also will be observed here. The first condition is when the aircraft land on a wet runaway and the second condition is when the aircraft land on dry runaway. From the analysis that will be done later, the result will show whether there will be a difference or not. Theoretically, the efficiency of landing an aircraft on a dry runaway will give the best effect to the landing gear. „To record the time of landing gear to stop at the end of the runaway‟ is the second objective where this is to measure the efficiency of the braking system of an aircraft at the wet and dry runaway condition. Braking system efficiency of an aircraft may be different at the different condition. This will be proven through the testing that will be conducted later. From here we can see whether there has and different efficiency or not. The time for landing gear to stop early theoretically is best on dry condition.
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„To propose the most efficient condition for an aircraft to land‟ is the last objective of this research. This is the main objective after both objectives above has been obtained. From there, a conclusion will be made on which condition that the landing gear will be the most effective either on dry runaway or on wet runaway. Each of condition will give a different result as the internet article taken on 20 th may 2012, 11.44am, it stated that, “Most of the liquids we consider using to "wet" a surface though, are terribly inept at providing boundary lubrication. They have none of the physical properties necessary in boundary lubrication. Wetting does provide a means by which to cool a system as it generates heat through friction. Heat often leads to thermal breakdown of substances. If the "wetting" substance provided a means to transport or dissipate heat then it would be useful.”(1)

1.3.

Problem Statement and Problem Solving

In this research there are some problem statements. The problem statements are as below:

1. Does the wet surface give the less friction to the landing gear? 2. To study and analysis how landing gear reacts when the aircraft land on the wet and dry surface of the runaway.

The problem statement here is, does the wet surface give the less friction to the landing gear? It will be known during the test that will be done later. An article taken on 20th may 2012; 4:23pm state that: “As a tire rolls along a wet runway, it is constantly squeezing the water from the tread. This squeezing action generates water pressures which can lift portions of the tire off the runway and reduce the amount of friction the tire can develop. “(2)

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From this article, it shows that when the runaway is wet, the landing gear will have less amount of friction due to wet condition. Besides that, another problem statement is to study and analysis how landing gear reacts when the aircraft land on the wet and dry surface of the runaway. From earlier research, On the surface runaway, the frictional properties of the surface can be either micro texture or macro texture where micro texture are the small individual particle itself showing the fine scale of the roughness and macro texture represents the whole runaway an it is in the visible roughness. (3)

1.4.

Limitation of the Project

Based on the research there are some limitation than need to be followed. This is to ensure the project research can be finish according to schedule and budget. In this research, there are some limitations that will be use and they also will be the controlled variable. This research will only be done on one landing gear configuration that is tricycle type. This is because these configurations are the most popular type used in the aircraft due to its high stability and visibility. Thus this configuration is selected to be tested in this research. To obtain the steady result, this configuration will be tested using the same aircraft and having the same Maximum Design Landing Weight (MDLW). (4) This variable will be scaled down to a relevant replica size so that it can be easily tested. The surface of the runaway also will be the control subject where the same place will be used to land the model. This has to be control to obtain the steady and fair result. This surface will be in two conditions that are during wet and also dry. The system in the model may not be the same but it still uses the same principle. In example, the braking system may be differing compared to the real aircraft. The real aircraft will have many system to slow down the aircraft such as spoilers, reverse thrusters and also antiskid system. Although there is some difference between the model and the real aircraft, it does not disturb the research because the entire field test will use the same system that originally from the model itself.

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CHAPTER 2: LITERITURE REVIEW
2.1. Research Theory, Ideology and Concept

Landing gear is the structure that supports an aircraft on the ground and allows it to taxi, take-off, and land. In fact, landing gear design tends to have several interferences with the aircraft structural design. Landing gear usually includes wheels, but some aircraft are equipped with skis for snow or float for water. Figure 2 illustrates landing gear primary parameters

Figure 2: Landing gear primary parameter

The landing gear is divided into two sections that is main gear or main wheel Secondary gear or secondary wheel. Main gear is the gear which is the closest to the aircraft centre of gravity (cg). Wheel track is the distance between two main gears (left and right) from front view. If a gear is expected to carry high load, it may have more than one wheel.
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There are some aspects to choose the right configuration of an aircraft. This is to ensure that the landing gear configuration can be adapted synchronically to the air design itself. In order to allow landing gear can cooperate with the aircraft design there are some requirement that must be check and they are: 1. Ground clearance requirement 2. Steering requirement 3. Take-off requirement 4. Tip back prevention requirement 5. Overturn prevention requirement 6. Touch-down requirement 7. Landing requirement 8. Static and dynamic load requirement 9. Aircraft structural integrity 10. Ground lateral stability 11. Low cost 12. Low weight 13. Maintainability 14. Manufacturability After all these aspects have been considered, a checklist will be produced to ensure that the selected configuration is function effectively with the design of the aircraft. As the figure 3 below gives the view on how the landing gear is selected to the aircraft. After all the requirement has been go through, the selected configuration will be adapted.

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Figure 3: Landing gear design flowchart

There are many configurations of landing gear that can be used to the aircraft. But for this research, there are three possible configurations that suited to this research that is tricycle, tail-gear and multi-bogey configuration. These three configurations give the best stability for the aircraft to land especially for the commercial aircraft.

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Tricycle is the most widely used landing gear configuration. The wheels aft of the aircraft cg is very close to it (compared with forward gear) and carries much of the aircraft weight and load; thus is referred to as the main wheel. Two main gears are in the same distance from the cg in the x-axis and the same distances in y-axis (left and right sides); thus both are carrying the same load. The forward gear is far from cg (compared with main gear); hence it carries much smaller load. The share of the main gear from the total load is about 80 to 90 percent of the total load, so the nose gear is carrying about 10 to 20 percent. This arrangement is sometimes called nose-gear. Figure 4 and figure 5 show the configuration and example of aircraft using the tricycle landing gear.

Figure 4: Configuration of tricycle landing gear

Figure 5: Beechcraft F33A Bonanza using tricycle landing gear

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Tail-gear landing gear has two main wheels forward of the aircraft cg and a small wheel under the tail. The wheels in front of the aircraft cg is very close to it (compared with aft wheel) and carries much of the aircraft weight and load; thus is referred to as the main wheel. Two main gears are in the same distance from the cg in the x-axis and the same distance in y-axis (in fact left and right sides); thus both are carrying the same load. The aft wheel is far from cg (compared with main gear); hence it carries much smaller load and then is called an auxiliary gear. The share of the main gear from the total load is about 80 to 90 percent of the total load, so the tail gear is carrying about 10 to 20 percent. This configuration of landing gear is referred to as a conventional landing gear, since it was the primary landing gear during the first 50 years of aviation history. Figure 6 and 7 shows the configuration and example of aircraft using tail-gear landing gear.

Figure 6: Configuration of tail-gear landing gear

Figure 7: Bush Hawk-XP in the tail wheel configuration

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As the aircraft gets heavier, number of gears needs to be increased. A landing gear configuration with multiple gears of more than four wheels also improves takeoff and landing safety. These are configuration are called multi-bogey. When multiple wheels are employed in tandem, they are attached to a structural component referred to as “bogey” that is connected to the end of the strut. An aircraft with multibogey landing gear is very stable on the ground and also during taxiing. Among various landing gear arrangement, a multi-bogey is the most expensive, and most complex for manufacturing. When the aircraft weight is beyond 200,000 lb, multiple bogeys each with four to six wheels are used. Large transport aircraft such as Boeing B-747 and Airbus A-380 utilize multi-bogey landing gear. Figure 8 and 9 shows the configuration and example of multi-bogey configuration. (5)

Figure 8: Multi- bogey landing gear configuration

Figure 9: Airbus 380 using multi-bogey landing gear

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2.2.

Previous Research and Proposed Project Comparison

Few ideas in this research may come from other source such as other research, websites, magazines journals and also manuals. These source become references in order to conduct this research. The main idea for this research is to be done is from data collected by Flight Safety Foundation in their “Approach and Landing Accident Reduction (ALAR) Tool Kit”. In this journal, the test for landing an aircraft in contaminated and wet runaway has been done. This journal show the statistical data of factor and effect of some element such as braking action, hydroplaning, directional control and landing distances of the aircraft on various state of wet and contaminated runaway. The other main source of this research is from Flight Operation Engineering research. The research is done in Performance Engineer Operation Course conducted for Boeing commercial airplanes on September 2009. The course is about “Takeoff/Landing on Wet, Contaminated and Slippery Runways” explains the detail such as the requirement in air legislation for takeoff and landing where it stated that; “Wet runway is part of AFM certification basis (FAR25.109 as Amendment 25-92)” (3) Also it stated that for landing in slippery runaway; “FAR dispatch requirements on a slippery runway is 1.15*FAR dry runway requirement (same as FAR Wet)” (3) For this research, the test will be conduct in a small scale with the controlled environment, the test that will be done only will show and simulate the difference of an aircraft landing on two different runaway conditions. The wind factor also has to be neglect in this research in order to produce a steady result. Besides that, this test will be done on the same type of surface but with two different of surface condition. Therefore, there are some similarities in this research with the previous research but it will be done in more simple technique and less complexity.

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CHAPTER 3: METHODOLOGY
3.1.0 Preface

In this project, a research will be conducted on landing gear to analyze the land on the different surface condition. We will know the difference of landing gear reaction land on the different surface condition. By using the scaled model, it can simulate how the real aeroplane reacts in the real situation. In this research also, we can see which condition is the best for the landing gear to react. Basically the methodology of this project consists in four major parts: I. II. III. IV. Select a model of aircraft and scaling it to an appropriate scale. Conducting the test on wet and dry surface condition. Comparing both results. Making conclusion.

Selecting an aircraft

Scale to reasonable size

Finite Element Analysis

Field testing

Compare the results

Making conclusions

Figure 10: The main flow of research development

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3.2.0.

Research Method

To complete the research, some method has to be followed. In this research, after selecting and scaling the aircraft (see figure 10), there are two important steps that should be done before comparing the results. These are performing finite element analysis and also field testing. Each of the tests should give a pair of result defined as theoretical result and field result. After both of this method is done, the pair of results will be compared. After that, the theoretical a field results will be compared each other. Lastly a conclusion can be made through the data collected from these two tests

3.2.1.

Finite Element Analysis

Finite element analysis is a test that uses software to test the performance, reliability and also the force experience to an object that have been analyzed and scaled it from the exact part of an aircraft. It is also called as reverse engineering as it came from the an existing part and yet to be tested without damaging the part itself. “Finite element analysis (FEA) has become commonplace in recent years, and is now the basis of a multibillion dollar per year industry. Numerical solutions to even very complicated stress problems can now be obtained routinely using FEA, and the method is so important that even introductory treatments of Mechanics of Materials { such as these modules { should outline its principal features.” (6)

This analysis came from an integral equation. It has been programmed to software to make it much more practical and easier to key in the data. The dataset that has been keyed in is used as input to the finite element code itself, which constructs and solves a system of linear or nonlinear algebraic equations:

Kabub = fa

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The u and f are the displacements and externally applied forces at the nodal points. The formation of the K matrix is dependent on the type of problem being attacked, and this module will outline the approach for truss and linear elastic stress analyses. Commercial codes will have very large element libraries, with elements appropriate to a wide range of problem types. One of FEA's principal advantages is that many problem types can be addressed with the same code by specifying the appropriate element types from the library.

3.2.2.

Field Test

After the FEA has been done, the field test will be conducted by using the scaled model of aircraft to simulate practically how the landing gear react when aircraft landing on two different conditions. On this test, the landing gear will be visually observed by the time of the landing gear “touched” the surface until the landing gear stopped. The model also will be equipped with a simple braking system and it will simulate the time taken of an aircraft to brake until it stops. In order to obtain a precise result, this test will be repeated five times. The data will be recorded and analyzed. After the test with dry and condition runaway, the result will be compared and a conclusion on which surface condition gives an effective stopping time to the aircraft.

3.2.3.

Data Analysis

From FEA and field test, the data then will be analyse and compared. Those data obtained will be used and generated in graph. The tabulated data is then will be observed and any of the difference between the data can be seen clearly. From the data collection, the time of aircraft to stop, rate of deceleration and the physical reaction of the landing gear will be compared between data gained from FEA and the data from field test. After that, a conclusion can be made on which condition of surface that the aircraft stops faster. Either on wet surface or on dry surface the aircraft will stop faster.

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3.2.4. Aircraft Type Description

The main subject of this research is the aircraft Boeing 737-300. It is a commercial aircraft that having a narrow body type of airliner and served for short and medium range flight. Short range aircraft means that the aircraft flying hour to complete one journey is between one to four hour journey ranges while medium range aircraft means that the aircraft flying hours is between four to seven hours ranges. (7) “The 737-300 is the first of the three member second generation CFM56 powered 737 family, which also comes with the stretched 737-400 and shortened 737-500. The success of the second generation Boeing 737 family pushed sales of the mark to over 3000, a record for a commercial jetliner.” (8) “The 737-300 flew for the first time on February 24 1984, while first deliveries were from November 1984. Since that time well over 1000 737-300s have been sold and it forms the backbone of many airlines' short haul fleets.” (8) The Boeing 737 was originated from United State of America. It was manufactured by Boeing Company. Figure 11 will show the pictorial view of the 737-300 aircraft and the Table 1 will state the details and description of the aircraft.

Figure 11: Lufthansa Boeing 737-300

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Table 1: Boeing 737-300 description

Descriptions  Powerplant    Performance    Weight    Dimension   

Details Two 89.0kN (20,000lb) CFM International CFM563B1 turbofans. optionally CFM563B2s. Max cruising speed 908km/h (491kt), long range cruising speed 794km/h (429kt). Range with 128 passengers and standard fuel 3362km (1815nm), range with 128 pax and max fuel 4973km (2685nm). High gross weight version max range 6300km (3400nm) with 140 passengers. Operating empty 32,881kg (72,490lb) standard (124,500lb). High gross weight option 62,823kg max takeoff 56,740kg two 97.9kN (22,000lb)

(138,500lb). Wings span 28.88m (94ft 9in). Length 33.40m (109ft 7in). Height 11.13m (36ft 6in). Wing area 105.4m2 (1135sq ft). Typical two class seating for 128 (eight premium class four abreast and 120 economy class six abreast). Capacity     Production  Standard one class seating for 141 at six abreast and 81cm (31in) pitch. Max seating for 149 at 76cm (30in) pitch. Grand total 737 orders stand at over 4236, Over 1104 are for the 300. Approximately 1070 737-300s were in service at late 1998.
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This aircraft model scaled down into relevant scale. The suggested scale is 1 inch = 32feet and size of Boeing 737-300 as figure 12 with scale (Figure 13).

Figure 12: Boeing 737-300 scaled 1in:32ft

Figure 13: Scale for Boeing 737-300

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3.2.5

Current research progress

For this semester, the research will be done until methodology only. The analysis and test will be only done next semester. Table shows the overall progress for this semester.

Table 2: Overall Progress for this semester

SEMESTER 1 2012/2013 NO TASK WEEK

1
1 Background studies Project understanding Work planning Problem identification Chapter 1 Chapter 2 Parameters & 7 Material Properties determination Chapter 3: 8 Forming of Research Methodology

2 x x

3 x x

4 x x

5 x x

6 x x

7 x x

8

9

10 11 12 13 14 15 16 17 18

x

2

x x x

x x x

x x x x x x x x x x x x x x x x x x x x

3

4 5 6

x

x

x

x

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Bibliography
1. Davidson. Wet vs. Dry Friction. webphysics. [Online] [Cited: sunday 5, 2012.] http://webphysics.davidson.edu/faculty/dmb/PY430/Friction/wetDry.htm. 2. idea from boeing company. smartcockpit.com. [Online] 2001. [Cited: 20 5, 2012.] http://www.smartcockpit.com/data/pdfs/flightops/flyingtechnique/Slippery_Runways .pdf. 3. BOEING. Flight Operation Engineering. Takeoff/Landing on Wet, Contaminated and Slippery Runways. 2008, p. 20. 4. Wikimedia Foundation. Aircraft gross weight. Wikipedia. [Online] Creative Commons Attribution-ShareAlike License, 19 March, 2012. [Cited: 20 May, 2012.] http://en.wikipedia.org/wiki/Aircraft_gross_weight. 5. Landing Gear Design. Sadraey, Mohammad. 9, s.l. : Daniel Webster College. 6. Finite Element Analysis. Roylance, David. 2001, p. 1. 7. Plymspotter(Dan). Airliners.net. www.airliners.net. [Online] 1 July, 2007. [Cited: 21 May, 2012.] http://www.airliners.net/aviationforums/general_aviation/read.main/3489073/. 8. Airliners.net. Airliners.net. www.airliner.net. [Online] [Cited: 21 May, 2012.] http://www.airliners.net/aircraft-data/stats.main?id=92.

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