Tuesday, April 2, 2019
Analysing Helicopter Landing Gear
Analysing Helicopter set down cant overThe arrive cant over mechanism, an important part of a chop, assists the helicopter to down. So, when the helicopter is in land condition, the set down incline should withstand the whole cant over of the helicopter. Apart from this, it should alike withstand the thrust while set down ope proportionalityn is on.The set down gear of a helicopter can be of collar fountsSkid typeWheel typeThe gaucherie type get gear is the simplest angiotensin-converting enzyme and cheaper to manufacture. Some skids both(prenominal)ow the helicopter to land even on water. If the helicopter need to land on hard surfaces (like runway) regularly, then some supererogatory kinds of shoe need to be attached to the skid. The shoe can be replaced upon wearing. The most commercial helicopter has the skid type come gear.The rhythm type land gear is little complicated and costlier as comp bed to the skid types but the wheel type landing gear gives eas ier ground handling and emolumentous while rough and closet landing.In our case, we gene gait to devise a landing gear suitable for landing on an advertize craft carrier. The landing condition can become really tough due to the vertical motion of the aircraft carrier. Considering this severe landing condition I pack chosen to go ahead with the wheel type landing gear for this engagement.I have use go gameS/ thought for creating the plan models, ADAMS/ thrill for running the vibration analytic thinking and ADAMS post processing for analyzing and bandageting the results. figure of Landing Gear MechanismResearch on Existing Landing GearFrom the earlier days of the aviation history, many concepts of the landing gears be utilize. I will beg off fewer of them hereLanding gear with flick forms The uses of aluminum leaf springs are possible for the very light weight helicopter (around 300kg). The figure of speech go steadys attractive.Fig.1 show the concept of aluminum spring landing gearThe concept of the heavy duty composite leaf spring is being experimented by some of the commercial aircraft manufacturer including AIRBUS. The main advantage of leaf spring concept is its reduced part count.Landing gear with shock absorber Most commercial applications use shock absorbers for the public figure of the landing gears.Fig.2 wake a typical shock absorber based landing gear excogitationBased on the numbers and the positions of the tires, this type of landing gears are typically classified in nine conditions as shown in the to a lower place figure (fig.3).Fig.3 Showing classifications of shock based landing gearI have apply the Twin configuration of tires for apiece of the landing gears and employ total of three landing gears in my concluding object. However, before subscribe toing the final design, I have studied one concept with dickens opposite number configuration landing gears at rear and one single configuration landing gear at front as well. envision Inputs a few(prenominal) of the design inputs were given along with the assignment and for others, either I googled surface from the manufacturers specifications or assumed. All together I have utilise the sideline design inputsWeight of the helicopter = 5126 KgLength of the helicopter = 15.16 mSpacing between the two rear landing gear = 2.5 mSpacing between the front and the rear landing gear = 5 mYoungs modulus of nerve = 2.7E11 N/m2Density of steel = 7801 kg/m3Poissons ratio of steel = 0.29Youngs modulus of rubber = 5E6N/m2Density of steel = 1100 kg/m3Poissons ratio of steel = 0.3Possible design resources later on doing the preliminary study of the existing gettable designs, two aspects had come to my mind before proceeding further one, coating all the assignment tasks and two, simplicity. I was looking for coming turn up few design concepts, which are good enough to cover all the assignment tasks and simple enough to finish the assignment in time. And I came out with the following(a) two conceptsDesign option -1 In this concept, I have used two twin-configured rear landing gears and one single-configured front landing gear.Fig.4 Showing a real life example of the Design option-1The three landing gears (one front and two rears) are connected to a triangular tail endsheesh form made up of steel. The top steel ready in turn is bolted with the fuselage.Design option-2 In the second concept, I have used three twin landing gears. One, in front and two are at rear. Please not that I have used two wheels (twin) in front (in design option-1, I have used a single nose wheel in front). The three landing gears are connected with the triangular top put together. The top frame is bolted with the fuselage.Creations of the ADAM modelsADAMS is a cock, develop by MSC and used extensively for simulating contrary types of mechanisms. It has different modules, out of which I have used the ADAMS/View here. I also used the ADAMS shakiness plu g-in for simulating the action of the ocean waves on the stationary helicopter on the aircraft carrier.I have used the block option for creating the base (aircraft carrier platform), torus option for creating the wheels , the link option to make up the axels, cylinder option to spend a penny the top frame (which will be bolted to the fuselage) and the spring option for creating the shock absorber springs . Also, I have made used of the options like point, contacts, joint, force, input channel and output channel. How? I will explain in details little later, while explaining each of the design concepts separately.Fig.5 Showing MSC ADAMS toolsADAMS model for the design option-1Start ADAMS/View.In the main tool chest right click the Rigid body and click the Point to create the points each at the wheel centers, at the three vertex of the frame, at the top left corner of the base.Again in the main tool box, right click the Rigid body deflect and click the encase to create the base.Cl ick on the Torus of the Rigid Body bar to create all the five wheels.Click on the Link of the buckram body bar to create the three axels.Click on the cylinder of the Rigid body bar to create all the three sides of the top frame.Use the Merge two bodies of the rigid body bar to blend all the three sides of the top frame into one.Under Joint bar, grant Revolute to connect the wheels with the individual axels.Under Forces bar, select Translational rally-Damper to connect the axels and the respective vertices of the triangular top frame.Create sliding joints between the base and back ground and between the top frame and back ground.Under Forces bar, select Contact to create the contact between the wheels and base.Finally, the design option-1 ADAMS model should look like belowFig.6 showing the ADAMS model of design option-1ADAMS model for the design option-2Following the similar procedure as described for creating the ADAMS model for design option-1, I have created the Design optio n-2 (with twin in front). The ADAMS model of the design option-2 looks like belowFig.7 Showing the ADAMS model of design option-2Comparisons of the design optionsAfter finishing the ADAMS model for both the design concepts, I run the average landing epitome on both design option models. The info used for the Normal landing summary for both the design options are as below good descent facilitate of the top frame = 0.5 m/sec perpendicular upwardly speed of the base = 0 m/secSpring hardness coefficient= 30 N/mmSpring damping coefficient =1 Ns/mmSpring preload = 17000 NI got the following resultsFig.8 Showing the acceleration temporary hookup of the top triangular frame for Design option-1 and the Design option-2.The higher up plot (fig.8) is showing 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- counseling reply force plot of the joint between the top frame and the back ground (space) for Design option-1 and the Design option-2.The above plot (fig.9) is showing that the design concept-1 is producing lots of Z- direction force, the force that can affect the stability of the helicopter.So, on the founding of the above analysis, I have chosen the Design option-2 for further study.Results and CalculationsSpring CalculationsSprung circumstances = 5126 kgMaximum acceptable acceleration = 0.3 m/s2Preload on each spring = 5126*(9.81+0.3)/3 = 17274 NDynamic Analysis ResultsNormal landingNormal landing analysis is performed based on the following conditionsVertical descent speed of the top frame = 0.5 m/secVertical upward speed of the base = 0 m/secSpring Stiffness coefficient= 30 N/mm, 50 N/mm, 70 N/mmSpring damping coefficient =1 Ns/mmSpring preload = 17274 NFig.10 Showing normal landing analysis of the design option-2 for different spring rateHard landingHard landing analysis is performed based on the following conditionsVertical descent speed of the top frame = 3 m/secVertical upward speed of the base = 3 m/secSpring Stiffness coefficient= 30 N/mm, 50 N/mm, 70 N/mmSpring damping coefficient =1 Ns/mmSpring preload = 17274 NFig.11 Showing hard landing analysis of the design option-2 for different spring rate squash landingCrush landing analysis is performed based on the following conditionsVertical approach speed of the top frame = 15 m/secVertical upward speed of the base = 0 m/secSpring Stiffness coefficient= 30 N/mm, 50 N/mm, 70 N/mmSpring damping coefficient =1 Ns/mmSpring preload = 17274 NFig.12 Showing crush landing analysis of the design option-2 for different spring rateThe acceptance criteria of the above analysis are as followNormal landing Minimum accelerationHard landing 50 m/sec2Crush landing 300 m/sec2In order to fulfill all the acceptance criteria, I have chosen the spring stiffness as 30 N/mm and proceed further for the vibration analysis.Vibration Analysis ResultsFig.13 Showing frequence response of the design option-2The nibble of the fr equency response curve is indicating the resonance frequency, which is around 2.5 Hz for our case.Fig.14 Showing PSD plot of the design option-2The above plot is showing the transmitted power from all the inputs used in the analysis as a function of the frequency. Again, the pick (2.5 Hz) is showing the resonating frequency here.Discussion childbed 1For the Task-1 , I have developed two design options (as shown in section 3.1 and 3.2) and match the two design options on the basis of normal landing analysis (section 3.3). The result has shown that the design option-2 is better in terms of acceleration and z-direction reaction force. Hence I have selected the design option-2 for the further study.Task 2For the task-2 , I have run the normal, hard and crush landing analysis (section 4.2) on the design option-2 for different spring stiffness and choose the high hat spring stiffness to ensure that all the acceptance criteria is met.Task 3For Task-3, I run the vibration analysis for the design option-2 (section-4.3) and find out the resonating frequency for the mechanism on response to the sea wave.Task 4For the task-4, I have discussed (section 3) how I have used the ADAMS/View for creating the ADAMS model and also, I have discussed how I simulate the mechanism.ConclusionThe wildness is given to come out with a simple but sensibly good landing gear mechanism, which will be able to run away all the test conditions specified in the assignment. The hand calculations are used for selecting the spring preload however, the selection of the spring stiffness is done on the basis of hit and trial.ADAMS/View and ADAMS Vibration plug-in are used for the whole analysis for getting the quick and easily interpretable results.I believe that the design of the mechanism can be further improved by incorporating the complication springs along with the compression springs.