Landing Gear-Design and Analysis Report

Shashank Datthatreya

Table of Content SUMMARY ....................................................................................................................................... 1

THEORETICAL FRAMEWORK ............................................................................................................. 2

Historical Overview of the design of landing gear. ........................................................................ 2

Aircraft with Fixed Landing Gear................................................................................................... 3

Function ....................................................................................................................................... 6

Main landing gears ....................................................................................................................... 6

Auxiliary landing ........................................................................................................................... 6

Classification ................................................................................................................................ 6

Available landing gear .................................................................................................................. 7

Landing gear Problem Statement: .................................................................................................... 8

Material Properties: ..................................................................................................................... 8

CALCULATIONS............................................................................................................................. 9

ANALYSIS OF THE LANDING GEAR USING ANSYS Software .............................................................. 13

ANSYS WORKBENCH................................................................................................................... 19

CONCLUSIONS................................................................................................................................ 24

BIBLIOGRAPH ................................................................................................................................. 25

1

SUMMARY The lift required to balance the weight of the airplane and allow the flight is only obtained when

the acquirer has acquired the relative speed with the air, which may give rise to this stall; for that

the airplane, on the ground and rest, you can fly it is necessary, to gain this speed running on the

ground, either launched or effect of its own propellant, which is the procedure commonly used.,

therefore there is the airplane that give it a mount that allows you to run by land with as little

resistance as possible, both by reasoning as part of the air for that in the less distance you can

reach the required speed. At the same time, for which the airplane can pass from your flight speed

until the rest on the ground in the shortest possible space, it is necessary, also providing them with

a system that allows you to shoot, but slowing their movement as soon as possible, with the safety

of the landing.

In this project will analyze the mechanical elements of the nose landing gear of the commercial

airplane FOKKER100, which is subject to loads with the aim of determining the factors of

concentration of effort, these efforts will be analyzed using traditional methods, and also will be

analyzed using numerical methods in this case by means of the ANSYS software which are shown in

chapter IV.

Finally there will be a comparison of the theoretical results with the computational

software(ANSYS), to perform this comparison we get a vision of the deformations that are

generated on the landing gear to the landing, thanks to the option of analysis the outputs can be

used to improve and optimize the design of the landing gear.

2

THEORETICAL FRAMEWORK

Historical Overview of the design of landing

gear. From the 225 kilograms of the Flyer and the Wright brothers to the lastest Boeing airplane

additions, the Landing Gear has been adapted to the needs of aircraft each time considering speed

and weight.

In the first aircraft it was impossible to connect the structures of the landing gear to the wings due

to the structural fragility of the same, in such a way that prevailed for a long time the so-called

"landing gear in EUV", with landing gear anchored at any part of the structure of the engine, the

only area with sufficient strength to accommodate the landing gear. When it was poly-engines are

the same thing, the landing gear was installed beneath the benches of the motors.

The old aircraft monometer comprised of the landing gear in a very close landing, which further

complicated it and more importantly, exhibited little stability of tread during takeoff and landing.

All the aircraft of World War I had the tip of a landing gear without good brakes and with primitive

systems of cushioning, beams of elastic cords. The landing gear allowed very little load from side to

side so the cracks were the order of the day.

The vertical velocity of contact with the ground typical at the time was 4 or 5 m/s.

The designers of the aircraft of the years 20 knew that the reduction of friction in an airplane in

flight was important to improve the speed and fuel efficiency, as well as maneuverability and

controllability.

In 1927, NACA opened a new tunnel of the research on the propellant (PRT) in the worked Orio al

Serio memorial aeronautical denoting Chinese-mestisos that include Sangley in Virginia. The PRT

was a wind tunnel very large by the time, with a diameter of 20 feet (6.1 meters). It was designed

to allow the testing of a fuselage of integer aeroplane with the engine and the propeller, with a

simple part of the airplane or a model of the scale. The aeronautical engineering at NACA stated

that the landing gear of aircraft faced surrendered to a lot of friction, and the PRT was the first

wind tunnel that allowed that this testing.

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The evidence in the PRT showed immediately that the landing gear contributed up to 40% of

friction of the fuselage, which gave a shock to researchers. It was reviewed that the reduction of

friction produced by landing gear significantly improved the functioning of the airplane in flight.

Aircraft with Fixed Landing Gear Engineers determined that there were several ways to reduce the friction of the landing gear. The

two methods were more obvious in getting the landing gear on the plane or reset a fixed landing

gear so that produce less friction while still highlighted below a plane.

Getting the landing gear was not exactly a new idea in 20 years. The plane of Wartin, built in 1917,

retractable gear was the Dayton Wright RB-1 1920 and Verville Sperry R-3 retractable gear were

also made in 1922. The majority of the planes they had fixed landing gear on the end of the

underpinnings of the metal because they were easier to designs and relatively lightweight.

When designing an airplane, the engineers established five requirements that were in conflict:

1. Operation

2. Weight

3. Cost

4. Reliability

5. Maintenance

The engineers found a better solution to the requirement of operation that was pulling the landing

gear fully inside the fuselage structure and covered, presenting a smooth surface that did not cause

any friction. But while that is ideal for a point of view of the operation, they determined that this

approach affected the other requirement was that more weight, cost, was less reliable, and

required more maintenance.

4

The Boeing Monomail, which first appeared in 1930, and the Lockheed Orion are generally

regarded as the pioneers in the development of retractable landing gear, proving that it was

practical. But the designer Jack Northrop of the airplane, who was very interested in streamline of

the aircraft to improve operation, produced the Northrop alpha, beta, and gamma with the fixed

landing gears during these 30 years.

This aircraft had aerodynamized covers that extended down the fuselage, with the wheels sticking

out in the background. These were usually referred as the gear "trouser". Although the "trouser"

would not engage produced more friction than gear fully contracted, this remained a landing gear

uncovered substantial excess of the improvement. Remained lighter, cheaper, more reliable, and

easier to maintain than the retractable gear.

But during the 30s, many designers were willing to accept the other disadvantages of retractable

landing gear just to reach a better performance.

Airplane with Retractable landing gear

For the landing gear retractable improvements in the functioning were clearly achievable, since a

retractable landing gear with its engines and machinery associated with more weight than a fixed

gear, so requiring the highest elevation in the airplane and denying some of the advantages of the

low friction of the gear collapsed.

While the contraction of the gear could improve the functioning of the plane, it required a larger

engine and more fuel and not to mention more money.

As the speed of the aircraft continued to expand during the years 30, particularly while the airplane

began to reach speeds of 200 miles per hour (322 kilometers per hour), the growing weight of

retractable gear became less important than reduce friction. Today, the private plane of low speed

still has fixed landing gear due to concerns of the cost and maintenance.

But virtually the largest airplane that had fully retractable landing gear that was designed

presented engineers with a number of problems, particularly mounting them on the airplane

without affecting other parts of the design of the aircraft. The commercial passenger aircraft

large as the 747 and Airbus A340 have enough internal volume so that the landing gear can fit

inside the diameter of the fuselage.

5

Aircraft with landing gear within the diameter of the fuselage

This is an example of a landing gear of tricycle which is used in the latest models of aircraft. This

type of landing gear makes the airplane easier to manage because the gear is steerable at nose.

Aircraft with landing gear of Tricycle

The fixed landing gear consists of two conventional wheels forward of the center of gravity of the

aircraft and a small wheel in the queue on the back. This configuration was nicknamed the

"taildragger."

Aircraft with conventional Landing Gear

The gamma of Northrop had the landing gear with the aerodynamic covers that extended

down the fuselage with the wheels that stuck up out of the structure.

Plane A-17 (1930) Gamma of Northrop

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Function The role of the landing gear is to absorb the loads of landing, up to an acceptable value for the

conditions of resistance of the aircraft structure.

The landing gear consists of two fundamental sets: main and auxiliary.

Main landing gears Supports most of the weight of the aircraft on the ground. Consists of two sets of one or more

wheels, each one at the side of the longitudinal axis of the airplane.

In addition to this wheel or combination of wheels, the main landing gear that includes other

mechanisms with diverse functions in the operation of the landing gear , such as shock absorbers,

brakes, hydraulic hammers, etc.

Auxiliary landing It consists of a set of one or more wheels, located in the bow or in the area of tail of the plane,

which completes the function of the tripod.

Classification The Landing Gears are usually classified as:

1. Fixed landing gears.

2. Retractable landing gears.

The landing gears are fixed during the flight they are permanently exposed to the air stream. They

are only used in small aircraft, low-speed where the increase in weight by adding a retract system

adversely influence on the total weight and the gain in speed wouldn't be much the performances.

7

Available landing gear There are two provisions of landing gear:

1. Conventional Landing gear

2. Tricycle Landing Gear

The conventional landing gear: This consists of two pillars of a structure underneath the wing or

fuselage to the height of the wing and a wheel or tail skid.

This type of landing gear has several disadvantages such as:

1. Does not allow good visibility of the pilot.

2. For blocked or detach the empennage has to produce a certain stall so that the plane is in a

horizontal position or the tail wheel in the air.

3. When the plane lands you can run the risk of a poor braking resulting in a summersault.

The steering system is performed by means of the tail skid commanded by cables or you can also

bring about a change in direction by applying the brake in one of the uprights and giving major

power in the case of the twin engine opposite that the brake is applied.

Configuring and nomenclature of the conventional Landing gear

The tricycle landing gear: This consists of two main pillars underneath the wing or fuselage and a

pillar in the nose of the plane. The amount of nose has a steering device.

In fact, all the aircraft have tricycles, but this designation has been generalized for those who carry

the third wheel in the bow, the tricycle landing gear has the same mission as the conventional

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landing gear, but simplifies the technique of the landing and allows pose the aircraft on the ground

in a horizontal position, eliminating the danger of damage, even when brakes are applied during

the landing.

The stability it provides the tricycle landing gear in the landing gear with tail wind or cross wind,

taking the support of the position of center of gravity (v. G. ), in front of the main wheels, and

travel in a straight line on the landing and taking off, are the most important advantages. This

condition is of particular importance for the aircraft to landing or blocked in small airstrips, with

crosswinds.

Landing gear Problem Statement:

Application of Loads as shown in below diagram.

Material Properties: Young’s modulus = 73000 MPa

Poisson’s ratio = 0.33

ANALYSIS OF THE LANDING GEAR of FOKKER100 through traditional methods.

(We have considered the Tricycle Landing Gear type for the analysis.)

9

CALCULATIONS The landing gear comprises of 3 supporting structures to which it is attached; points A,B and C.

The horizontal component V and the vertical component D for the reactions at A, B and C are taken

into consideration.

Using the equilibrium theory, we can get each of the required forces and moments.

As we can calculate the total moment through AB,

MAB = -(15000 + 10000)64 + 24CV = 0

We can now determine CV,

CV = 6666lb

We can get CD acting on both ends as the reaction at C must have a line of action along the

respective line since the member is fixed at both ends.

CD = 66666(24/28) = 57142lb

CD = 66666(36.93/28) = 87900lb

By taking moments about a drag axis through point(A)

MA(D) = -60000 x 9 – 40000 x 29 – 66666 x19 +38(BV) = 0

We can get,

BV = 78070lb

We also know that

V = 0

By this we can obtain AV

V = -78070 + 60000 + 40000 + 66666 – VA = 0

And

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AV = 88596lb.

By taking moments about V-axis through point A

MA(V) = 57142 x 19 – 15000 x 9 – 10000 x 29 – 38.BD = 0

We can get

BD = 17386lb.

Similarly finding AD

D = 07

D = -57142 + 15000 + 10000 + 17386 + AD = 0

Which means,

AD = 14756lb.

Moments about V and D axes through point O give us the results

MO(V) = 5 x 10000 + 14756 x 19 – 17386 x 19 = 0

MO(D) = 20000 x 10 – 88596 x 19 + 78070 x 19 = 0

This brings us to the Oleo-strut reactions to be determined.

The loads applied to the wheels transfer to point(O).

Thus

Total V load at (O) = 60000 + 40000 = 100000

And

Total D load equals 15000 + 10000 = 25000.

These values bring us to the moments about V and D axes through (O), which then will be

MO(V) = (15000 – 10000).10 = 50000 in.lb

And

MO(D) = (60000 – 40000).10 = 200000 in.lb.

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We can get TE by considering moments about the axis OE

MOE = -50000 + TE = 0

Hence,

TE = 50000 in.lb

Taking moments about D axis through point D

MD(D) = 200000 – 28.ES = 0

get us,

ES = 7143lb.

Moments about D axis through point G are as follows

MG(D) = 200000 – 100000 x 17 – 66666 x 17 + 34.DFV = 0

Now,

DFV = 77451lb.

So at both ends,

DFS = 77451(17/28) = 47023lb

DF = 77451 (32.72/28) = 90503lb

we know V = 0

moments into consideration as follows

V = 100000 – 77451 + 66666 – DGV = 0,

gives us:

DGV = 89215

So at both ends,

DGS = 89215 . (17/28) = 54164lb

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DG = 89215(32.23/28) = 104190lb

Moments about S axis through point D are

MD(S) = -25000 x 35 + 28.ED = 0

gives us the unknown component

ED = 32143lb

Moments about D-axis through point (O)

MO(D) = 20000 + 54164 x 36 – 7143 x 64

= 200000 + 1949904 – 1692828 – 457150 = 0

MO(S) = 32143 x 64 – 57142 x 36 = 0

Top member AB gives reaction forces as follows

Taking moments about D-axis through point A,

MA(D) = -89215 x 2 – 77451 x 36 – 38.BV = 0

We get,

BV = 78070lb.

Also,

V = 0,

V = 89215 + 77451 – 78070 – AV = 0

which means,

AV = 88596lb.

Moments about V-axis through point A

MV(D) = 50000 + 32143 x 19 -38.BD = 0

Which means,

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BD = 17386

Similarly we know

D = 0

D = 17386 – 32143 + AD = 0

We obtain the last unknown component, AD

AD = 14757lb

The landing is considered as a free body while performing the stated numerical calculations. We

obtain 4 reaction forces resulting from the given applied forces.

Verification of the obtained reaction forces is done on the software ANSYS. This is discussed in the

following sections.

ANALYSIS OF THE LANDING GEAR USING

ANSYS Software Development in the finite element (ANSYS software) is carried out in three different steps, the first

step is called pre-processor which is to develop modeling and the creation of the finite element

mesh, the second step is the restriction and implementation of the load, and the last is the solution

in which the results are displayed also known as post-processor.

The implementation and utilization of the software shows the places which have the highest

deformation and effort in the structure.

ANSYS APDL

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The following steps are done in ANSYS APDL for the process of 2-D analysis of the Landing Gear

structure:

1. Type of Analysis selection

Specified in the program the kind of analysis that will be analyzed (structural type)

2. Element Type Selection

The material elements assigned for the structural analysis ,in this case LINK180 and BEAM188

are used. The main strut will try to bend and compress when load is acted upon, this part will

thus be modeled as a Beam. The rest of the 2 struts will face compression and tension, which

can be analyzed as a Link.

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3. Real Constraints

Real conslanding gearts for the LINK element is done before proceeding

4. Engineering Data

Material Properties as mentioned in the problem are input for the respective elements.

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5. 2-D model(free body diagram)

The modeling of the simplified structure of the landing gear is done.

6. Sections

Sections of the structure for the purpose of meshing are defined

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7. Meshing

Meshing is done, giving the inputs of element sizes.

8. Loads and Solution

Restriction and applications of the load is processed. After the Remote Forces are applied after

the Displacement support is given, the solution is done.

18

For the determination of the efforts by finite element of the steel tube, the General Prostproc , Plot

Results and contour plot features are used.

Deformation is analyzed as shown

19

ANSYS WORKBENCH The following steps are done in ANSYS WorkBench to determine the reaction forces on a 3-D

component of the Landing Gear structure.

Material Properties

Geometry modeling (Modeling done in CATIA software and imported in ANSYS Workbench for

analysis)

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Meshing

Fine meshing done on the relevant edges, sides and contacts.

Sizing

Use Advanced Size Function Off

Relevance Center Fine

Element Size Default

Initial Size Seed Active Assembly

Smoothing High

Transition Fast

Span Angle Center Medium

Minimum Edge Length 2.54e-004 m

Inflation

Use Automatic Inflation None

Inflation Option Smooth Transition

Transition Ratio 0.272

Maximum Layers 5

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Growth Rate 1.2

Inflation Algorithm Pre

View Advanced Options No

Patch Conforming Options

Triangle Surface Mesher Program Controlled

Loads and Constraints

Remote force applied on wheel-1

Remote force applied on wheel-2

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Applied forces on each component tabulated below:

Object Name

Displacement Remote

Displacement

Remote Displacement

2

Remote Displacement

3

Remote Force

Remote Force 2

State Fully Defined

Scope

Scoping Method

Geometry Selection

Geometry 4 Faces 1 Face 2 Faces

Coordinate System

Global Coordinate System

X Coordinate

1.0773 m -5.2505e-020

m 4.2071e-006

m 4.1831e-005

m 4.4498e-010

m

Y Coordinate

-1.2803 m 0.4826 m -0.4826 m 0.254 m -0.254 m

Z Coordinate

-0.15569 m -3.81e-002 m -1.5878 m

Location Defined

Definition

Type Displacement Remote Displacement Remote Force

Define By Components Components

Coordinate System

Global Coordinate

System

X Component

0. m (ramped) -44482 N (ramped)

-66723 N (ramped)

Y Component

0. m (ramped) 0. N (ramped)

Z Component

0. m (ramped)

Free 0. m (ramped) 1.7793e+005 N (ramped)

2.6689e+005 N (ramped)

Static structural analysis solution

Total Deformation Plot

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Equavalent Stress

Forces and reaction forces at each component tabulated

Definition

Type Force Reaction Moment Reaction

Location Method

Boundary Condition

Boundary Condition

Displacement Remote

Displacement Remote

Displacement 2 Remote

Displacement 3 Remote

Displacement

Results

X Axis 2.0148e+005

N -46201 N -26692 N -17385 N 0. N·m

Y Axis 302.09 N 1486.1 N -1.1393e+005 N 1.1215e+005 N 0. N·m

Z Axis 2.684e+005 N 0. N -3.3476e+005 N -3.7846e+005 N 57829 N·m

Total 3.3561e+005

N 46225 N 3.5462e+005 N 3.9511e+005 N 57829 N·m

The results obtained showed that the structural analysis done on structure of materials Alluminium

allow and structural steel can verify the results obtained from numerical approach, which are

identical.

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CONCLUSIONS

The method of finite elements has acquired a great importance in the solution of engineering problems,

physicists, etc. , as previously it was virtually impossible to resolve cases by traditional mathematical

methods. In this one would have to model a structure through prototypes which are proving physically

until you find the best design. This circumstance forced to perform prototypes, testing and making

results in high cost in both economic and development time.

The Finite Element model allows you to perform a mathematical calculation of the real system, easier

and more economical to change than a prototype. However, it should never cease to be a method of

calculating approximate due to the basic assumptions of the method. The finite element is used in the

design and improvement of products and industrial applications, as well as in the simulation of physical

and biological systems complex.

The calculations are performed on a mesh of points (called nodes), which serve to turn a basis for

domain in finite elements. The generation of the mesh is usually performed with special programs called

mesh generators, at an earlier stage in the calculations is called pre-process. In accordance with these

relationships of connectivity relates the value of a set of unknown variables defined in each node and

called degrees of freedom. The set of relationships between the value of a given variable between the

nodes can be written in the form of a system of linear equations, the number of equations of the system

is proportional to the number of nodes.

The result of the stresses and deformations vary due to the shielding already that if you reduce the

value tends to be less accurate and by increasing the amount of prominent the result tends to be more

exact.

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BIBLIOGRAPH

Analysis and Design of Flight Vehicle structures, E. F. Bruhn

Aircraft Design, A Conceptual Approach, Raymer

Aircraft landing gear design principles and principles, 1988 Nnorman S Currey

Design and Construction of ultra-light planes, Beaujon Herbert

Fundamentals of aerodynamics / John D. Anderson, Jr. 3Ed. Boston, Mcgraw-hill, c2001.

Aircraft structures for Engineering Students, Megson, Fourth Edition, 2006