Analysing Helicopter Landing Gear Engineering Essay

The Landing cogwheel, an of import portion of a chopper, assists the chopper to land. So, when the chopper is in land status, the landing cogwheel should defy the whole weight of the chopper. Apart from this, it should besides defy the push while set downing operation is on.

The landing cogwheel of a chopper can be of three types:

Skid type

Wheel type

The skid type landing cogwheel is the simplest one and cheaper to fabricate. Some skids allow the chopper to set down even on H2O. If the chopper demand to set down on difficult surfaces ( like track ) on a regular basis, so some particular sorts of “ shoe ” demand to be attached to the skid. The shoe can be replaced upon have oning. The most commercial chopper has the skid type set downing cogwheel.

The wheel type landing cogwheel is small complicated and costlier every bit compared to the skid types but the wheel type set downing gear gives easier land handling and advantageous while unsmooth and crush landing.

In our instance, we have to plan a landing cogwheel suited for set downing on an air trade bearer. The landing status can go truly bad due to the perpendicular gesture of the aircraft bearer. Sing this terrible set downing status I have chosen to travel in front with the wheel type landing cogwheel for this assignment.

I have used ADAMS/View for making the design theoretical accounts, ADAMS/Vibration for running the quiver analysis and ADAMS station processing for analysing and plotting the consequences.

Design of Landing Gear Mechanism

Research on Existing Landing Gear

From the earlier yearss of the air power history, many constructs of the landing cogwheels are used. I will explicate few of them here:

Landing cogwheel with leaf springs: The utilizations of aluminium foliage springs are possible for the really light weight chopper ( around 300kg ) . The design looks attractive.

Fig.1: Showing the construct of aluminium spring landing cogwheel

The construct of the heavy responsibility composite foliage spring is being experimented by some of the commercial aircraft maker including AIRBUS. The chief advantage of foliage spring construct is its decreased portion count.

Landing cogwheel with shock absorber: Most commercial applications use daze absorbers for the design of the landing cogwheels.

Fig.2: Showing a typical daze absorber based set downing gear design

Based on the Numberss and the places of the tyres, this type of landing cogwheels are typically classified in nine constellations as shown in the below figure ( fig.3 ) .

Fig.3: Showing categorizations of daze based landing cogwheel

I have used the “ Twin ” constellation of tyres for each of the landing cogwheels and used sum of three set downing cogwheels in my concluding design. However, before choosing the concluding design, I have studied one construct with two twin constellation set downing cogwheels at rear and one individual constellation set downing cogwheel at forepart every bit good.

Design Inputs

Few of the design inputs were given along with the assignment and for others, either I googled out from the maker ‘s specifications or assumed. All together I have used the undermentioned design inputs:

Weight of the chopper = 5126 Kg

Length of the chopper = 15.16 m

Spacing between the two rear set downing cogwheel = 2.5 m

Spacing between the forepart and the rear set downing gear = 5 m

Young ‘s modulus of steel = 2.7E11 N/m2

Density of steel = 7801 kg/m3

Poisson ‘s ratio of steel = 0.29

Young ‘s modulus of gum elastic = 5E6N/m2

Density of steel = 1100 kg/m3

Poisson ‘s ratio of steel = 0.3

Possible design options

After making the preliminary survey of the bing available designs, two facets had come to my head before continuing farther: one, covering all the assignment undertakings and two, simpleness. I was looking for coming out few design constructs, which are good plenty to cover all the assignment undertakings and simple plenty to complete the assignment in clip. And I came out with the following two constructs:

Design option -1: In this construct, I have used two twin-configured rear landing cogwheels and one single-configured forepart set downing cogwheel.

Fig.4: Showing a existent life illustration of the Design option-1

The three landing cogwheels ( one forepart and two rears ) are connected to a triangular top frame made up of steel. The top steel frame in bend is bolted with the fuselage.

Design option-2: In the 2nd construct, I have used three duplicate set downing cogwheels. One, in forepart and two are at rear. Please non that I have used two wheels ( twin ) in forepart ( in design option-1, I have used a individual nose wheel in forepart ) . The three landing cogwheels are connected with the triangular top frame. The top frame is bolted with the fuselage.

Creations of the ADAM theoretical accounts

ADAMS is a tool, develop by MSC and used extensively for imitating different types of mechanisms. It has different faculties, out of which I have used the ADAMS/View here. I besides used the ADAMS Vibration circuit board for imitating the action of the ocean waves on the stationary chopper on the aircraft bearer.

I have used the “ block ” option for making the base ( aircraft bearer platform ) , “ toroid ” option for making the wheels, the “ nexus ” option to make the axels, “ cylinder ” option to make the top frame ( which will be bolted to the fuselage ) and the “ spring ” option for making the daze absorber springs. Besides, I have made used of the options like “ point ” , “ contacts ” , “ articulation ” , “ force ” , “ input channel ” and “ end product channel ” . How? I will explicate in inside informations small subsequently, while explicating each of the design concepts individually.

Fig.5: Showing MSC ADAMS tools

ADAMS theoretical account for the design option-1

Start ADAMS/View.

In the chief tool chest right click the “ Rigid organic structure ” and snap the “ Point ” to make the points each at the wheel centres, at the three vertex of the frame, at the top left corner of the base.

Again in the chief tool box, right click the “ Rigid organic structure ” saloon and snap the “ Box ” to make the base.

Click on the “ Torus ” of the “ Rigid Body ” saloon to make all the five wheels.

Click on the “ Link ” of the “ stiff organic structure ” saloon to make the three axels.

Click on the “ Cylinder ” of the “ Rigid organic structure ” saloon to make all the three sides of the top frame.

Use the “ Merge two organic structures ” of the “ stiff organic structure ” saloon to unify all the three sides of the top frame into one.

Under Joint saloon, choice Revolute to link the wheels with the several axels.

Under Forces saloon, choice Translational Spring-Damper to link the axels and the several vertices of the triangular top frame.

Create skiding articulations between the base and back land and between the top frame and back land.

Under Forces saloon, choice Contact to make the contact between the wheels and base.

Finally, the design option-1 ADAMS theoretical account should look like below:

Fig.6: demoing the ADAMS theoretical account of design option-1

ADAMS theoretical account for the design option-2

Following the similar process as described for making the ADAMS theoretical account for design option-1, I have created the Design option-2 ( with twin in forepart ) . The ADAMS theoretical account of the design option-2 expressions like below:

Fig.7: Showing the ADAMS theoretical account of design option-2

Comparisons of the design options

After completing the ADAMS theoretical account for both the design constructs, I run the “ Normal landing ” analysis on both design option theoretical accounts. The informations used for the “ Normal landing ” analysis for both the design options are as below:

Vertical descent velocity of the top frame = 0.5 m/sec

Vertical upward velocity of the base = 0 m/sec

Spring Stiffness coefficient= 30 N/mm

Jumping muffling coefficient =1 Ns/mm

Jumping preload = 17000 N

I got the undermentioned consequences:

Fig.8: Showing the acceleration secret plan of the top triangular frame for Design option-1 and the Design option-2.

The above secret plan ( fig.8 ) is demoing that the acceleration of the top frame for the design option-1 is higher than that for the design option-2.

Fig.9: Showing the Z-direction reaction force secret plan of the joint between the top frame and the back land ( infinite ) for Design option-1 and the Design option-2.

The above secret plan ( fig.9 ) is demoing that the design concept-1 is bring forthing tonss of Z- way force, the force that can impact the stableness of the chopper.

So, on the footing of the above analysis, I have chosen the Design option-2 for farther survey.

Consequences and Calculations

Spring Calculations

Sprung mass = 5126 kilogram

Maximum acceptable acceleration = 0.3 m/s2

Preload on each spring = 5126* ( 9.81+0.3 ) /3 = 17274 N

Dynamic Analysis Consequences

Normal landing

Normal set downing analysis is performed based on the undermentioned conditions:

Vertical descent velocity of the top frame = 0.5 m/sec

Vertical upward velocity of the base = 0 m/sec

Spring Stiffness coefficient= 30 N/mm, 50 N/mm, 70 N/mm

Jumping muffling coefficient =1 Ns/mm

Jumping preload = 17274 N

Fig.10: Showing normal landing analysis of the design option-2 for different spring rate

Hard landing

Hard landing analysis is performed based on the undermentioned conditions:

Vertical descent velocity of the top frame = 3 m/sec

Vertical upward velocity of the base = 3 m/sec

Spring Stiffness coefficient= 30 N/mm, 50 N/mm, 70 N/mm

Jumping muffling coefficient =1 Ns/mm

Jumping preload = 17274 N

Fig.11: Showing difficult set downing analysis of the design option-2 for different spring rate

Crush landing

Crush set downing analysis is performed based on the undermentioned conditions:

Vertical attack velocity of the top frame = 15 m/sec

Vertical upward velocity of the base = 0 m/sec

Spring Stiffness coefficient= 30 N/mm, 50 N/mm, 70 N/mm

Jumping muffling coefficient =1 Ns/mm

Jumping preload = 17274 N

Fig.12: Showing crush set downing analysis of the design option-2 for different spring rate

The credence standard of the above analysis are as follow:

Normal landing: Minimal acceleration

Difficult landing: 50 m/sec2

Crush landing: 300 m/sec2

In order to carry through all the credence standard, I have chosen the spring stiffness as 30 N/mm and continue further for the quiver analysis.

Vibration Analysis Results

Fig.13: Showing frequence response of the design option-2

The choice of the frequence response curve is bespeaking the resonance frequence, which is around 2.5 Hz for our instance.

Fig.14: Showing PSD secret plan of the design option-2

The above secret plan is demoing the familial power from all the inputs used in the analysis as a map of the frequence. Again, the choice ( 2.5 Hz ) is demoing the resonating frequence here.

Discussion

Undertaking 1

For the Task-1, I have developed two design options ( as shown in subdivision 3.1 and 3.2 ) and compare the two design options on the footing of normal set downing analysis ( subdivision 3.3 ) . The consequence has shown that the design option-2 is better in footings of acceleration and z-direction reaction force. Hence I have selected the design option-2 for the farther survey.

Undertaking 2

For the task-2, I have run the normal, difficult and crush landing analysis ( subdivision 4.2 ) on the design option-2 for different spring stiffness and take the best spring stiffness to guarantee that all the credence standard is met.

Undertaking 3

For Task-3, I run the quiver analysis for the design option-2 ( section-4.3 ) and happen out the resonating frequence for the mechanism on response to the sea moving ridge.

Undertaking 4

For the task-4, I have discussed ( subdivision 3 ) how I have used the ADAMS/View for making the ADAMS theoretical account and besides, I have discussed how I simulate the mechanism.

Decision

The accent is given to come out with a simple but moderately good landing cogwheel mechanism, which will be able to go through all the trial conditions specified in the assignment. The manus computations are used for choosing the spring preload nevertheless, the choice of the spring stiffness is done on the footing of hit and test.

ADAMS/View and ADAMS Vibration circuit board are used for the whole analysis for acquiring the quick and easy explainable consequences.

I believe that the design of the mechanism can be farther improved by integrating the tortuosity springs along with the compaction springs.

July 14, 2017