Naval Helicopter Landing Gear Engineering Essay

Naval Helicopter Landing accessorytrain Engineering EssayThe arrive power train, is a structure (or mechanism) attached to the fuselage (or the body) of the aircraft, helps the aircraft during land, take-off and backdrop handling operations. The landing sky plays important role absorbing the scold (or thrust) while landing and thus ensure lower densification related injuries and veridical damages. For achieving this crush worthiness require optimum design of the springs of the landing adapts.I confound started the process of the optimum design of the landing gear mechanism through with(predicate) theoretical hand calculations. afterward I established a base design through hand calculation I shifted to the ADAMS tool. The ADAMS tool seemed to be rattling powerful for achieving the optimum mechanism design solution through number of iterations.For the sake of simplicity, I have considered non-retractable type of landing gear for this study. Also, I have considered using only helical compression spring and no torsion spring for this design study.Reoceanrch on Naval Helicopter Landing GearThe naval helicopters operate in much severe landing conditions comp ard to the commercial helicopters. Hence, while designing the naval helicopter landing gear all(a) the prerequisite landing conditions should be taken care. In this sulfurtion I am going to discuss round the types of landing gear and few practical examples about the usage of the landing gears.History and evolutionThe first cycleed landing gear appeared in Santos-Dumonts No.14 bis on 1906 soon after the Wright brothers famous flight.Initially, the landing gear used to have bungee as infract absorbing elements.The Ford trimotor landing gear, which used rubber discs and rebound cables, was the predecessor of the modern days shock absorbing landing gear.During World War-II, the shock absorbing landing gear had developed further. Use of the spring and lever came into the landing gear system design. After the world war, the landing gear design matured further to give modern days sophisticated landing gear system.Types of Landing Gears All of the landing gear used in helicopters can be broadly classified in three categoriesTail tugger Landing Gear Two main(prenominal) gears are placed under the mid of the fuselage and one tail gear is placed under the tail of the helicopter for the tail dragger landing gear arrangement. This type of landing gears are used in older helicopters (e.g. Seahawk)Tri Cycle Landing Gear In this configuration, there are one nose wheel and two main gears at the mid of the fuselage. Most of the modern helicopter has this landing gear configuration.Tandem Landing Gear Large aircrafts use triune wheels in line for each of the landing gears and this configuration is known as Tandem.Examples about the usage of the landing gears in naval helicoptersLanding Gear for Seahawk S70B The Seahawk is an US naval aircraft manufactured by Sikorsky Aircraft in Stratfor d, Connecticut.Fig.1 Showing a Seahawk in operation (Image source http//www.naval-technology.com/projects/seahawk/seahawk2.html)The chopper has energy absorbing two-wheel tail dragger type of landing gear arrangements. The landing gear design is much simpler compared to the other naval helicopters.Boeing Vertol CH-46 Sea Knight Sea Knight is a devil dog transport helicopter, manufactured by Boeing Vertol.Fig.2 Showing a Sea Knight(Image source http//en.wikipedia.org/wiki/FileUSMC_CH-46.jpg)The Sea knight has tricycle type of landing gear system. Each of the landing gear has twin wheels.Sikorsky SH-3 Sea King The Sea King is an anti-submarine amphibian helicopter manufactured by Sikorsky. It is fitted with retractable type spark advance dragger landing gear arrangement.MH-53E Sea Dragon This is a three engine powered large navy helicopter designed for heavy lifting and airborne Mine Countermeasures (AMCM). It is fitted with twin-wheel tricycle configuration of landing gear system.D evelopment of the Landing Gear MechanismThe landing gear mechanism should be strong bounteous to withstand the specified stringent landing conditions of this assignment. I am planning to develop a landing gear mechanism using two stunt woman understructure landing gears and a nose landing gear. All the landing gear will use helical compression springs only.Fig.3 Top view of the landing gear arrangements for the conceptAs the above figure shows, the concept will have the effect of gravity somewhere in in the midst of the front and the rear landing gears.Selection of the proper compression spring is the key to the success of the mechanism. Hence I have started with the hand calculation to arrive at the prior spring design parameters.Hand CalculationTotal mass = 5126 kgHence, Sprung mass on each spring = 1025.2 kgFor zero initial velocitySay, max. Deformation of spring =35 mmSo, spring rate K = 292.9142857 N/mmFor prevalent landingInitial velocity of helicopter = 0.5 m/secSpring rate k = 292.9142857 N/mmNow, using the formulae 0.5*m*v2=0.5*k*x2 max twisting of the springs =0.935414347 mmFor hard landingInitial velocity of helicopter = 3 m/secInitial velocity of pull down = 3 m/secSo, Relative velocity between the helicopter and the aggrandize = 6 m/secSpring rate k =292.9142857 N/mmSo, Max optical aberration of the springs = 11.22 mmFor crush landingInitial velocity of helicopter = 15 m/secSpring rate k = 292.9142857 N/mmSo, Max deformation of the springs =28.06 mmSince, the deformation values from the hand calculation are well below 30 mm with the spring rate of 292 N/mm. So, I think it is good to go ahead with these values and check the acceleration results and vibration results by creating the ADAMS model.Developing ADAMS ModelThe ADAMS models of the landing gear mechanism are formd by the ADAMS/View. I have come out with two ADAMS design based on the already discussed mechanism concept. The following steps are followed to create each of the ADAMS modelsUnit Setting I choose to use the units as Length Millimeters, Mass Kg, Force Newton, Time Second, Angle Degree, and Frequency Hertz. Following undifferentiated units are important for getting accurate results.Gravity Setting I activated the gravity.Points Points are the basic building block of the whole mechanism.Box This excerpt was used for creating the deck.Torus All the wheels were created using the torus option.Link The structure and the axels were created using the link options.Translational Spring Damper This option was utilized for creating all the helical compression springs of the designs.Contact The contact option was used for simulating the contacts between the deck and the wheels.Revolute articulatio The joints between the wheels and the axels were created using the revolute joint option of ADAMS.Translational Joint For simulating the vertical phone line speed of the helicopter and vertical speed of the deck it was required to create transitional joints between the structure and space and between deck and space.ADAMS Mechanism Design-1Fig.4 ADAMS model of the design option-1.Fig.5 ADAMS point table for the design option-1.ADAMS Mechanism Design-2Fig.6 ADAMS model of the design option-2Fig.7 ADAMS point table for the design option-2The basic difference between the design opton-1 and the design option-2 is in the height of the design. After reviewing the initial displacement results (which I will present in the next section) of the option-1, I have unflinching to increase the height, as for the specified scrutiny condition the structure is hitting the deck for design option-1.Result Comparison for Option-1 and Option-2Fig.8 Deflection plot of land of the structure for crush landing conditionThe above plot is cover the comparison of the deflection of the top frame (structure connected to the fuselage), it shows that the option-1 has much higher deflection. The deflection value for the option-1 is tied(p) higher than the clearanc e between the structure and the deck. Means, for option-1, the structure will hit the ground for extreme condition. So, Option-2 is a better design.Testing ADAMS model in different Landing ConditionsDifferent landing conditions specified for this assignment is simulated in ADAMS for the design option-2.Normal landing Here the vertical descent speed of 0.5 m/sec is applied at the translational joint between the structure and space. Result is shown belowFig.9 Normal landing acceleration plotThe result for the normal landing test for the design option-2 is showing that the maximum acceleration is 6.8 m/sec2.Hard Landing For the hard landing test, I applied vertical descent speed of 3m/sec at the joint between the structure and space and vertical deck speed of 3m/sec at the joint between the deck and space. Here is the resultFig.10 Hard landing acceleration plotThe above plot is showing that the maximum acceleration value for the hard landing test of the design option-2 is 19.3 m/sec2 .Crush Landing In order to simulate the crush landing condition, I applied the vertical approach speed of 15 m/sec at the joint between the structure and space, keeping the deck stationary.The result of the crush landing test is shown belowFig.11 Acceleration plot for the crush landing testThe above plot is showing that the maximum acceleration value for the crush landing test is 206.6m/sec2.Running Vibration analytic thinking in ADAMSThe naval helicopter will be kept in landed condition over the aircraft carrier. The aircraft carrier will be oscillating always under the influence of the sea waves. The purpose of the vibration analysis is to find out the resonating frequency of the landing gear mechanism under the sea oscillation.For simulating the sea wave oscillation, I created five kinetic actuators placed at the centre of each of the axels and placed one output channel at the centre of gravity of the top structure.Frequency response analysis The frequency response analysis (FR A) shows the amplification of acceleration for each frequency values. The FRA plot for the design option-2 is shown belowFig.12 Frequency response plot for the design option-2The FRA plot above is showing a pick at 2.5 Hz. The pick is the resonating frequency of the landing gear mechanism.Results of the Different ADAMS AnalysisMaximum acceleration for normal landing = 6.8 m/sec2.Maximum acceleration for hard landing = 19.3 m/sec2.Maximum acceleration for crush landing = 206.6 m/sec2.Resonating frequency of the mechanism = 2.5 Hz.ConclusionThe conceptual design of the naval landing gear is simulated using ADAMS for the specified landing conditions. The results from the simulation are showing that the maximum acceleration values are well below the specified maximum limit for this assignment. The ADAMS vibration simulation is showing the resonating frequency for the mechanism as 2.5 Hz.