Experimental equipment for study of landing gear mechanisms.
Key words: equipment, landing gear, tests, kinematical parameters, mechanisms.
Lately, the aerial transport has recorded a significant development. Taking into account the remarkable increase of the service period for the transport aircrafts (over 20 years), one of the base conditions to assure the flight security is the prediction of the damage for the component elements because of the fatigue.
The analysis of the damage distribution at the some of the transport aircrafts with big capacity made on the period of many exploitation years shows that one of the aircrafts systems, which is responsible to the damage of aircrafts, is the landing gear.
The testing of the landing gear is an important part of the design or of problems that must be resolved during the design process of the landing gear. The testing of the aircrafts is made in laboratory or on the aircrafts. The testing on the aircrafts has the following disadvantages: the immobilization of the aircraft determining the increased costs and non-productive time.
For eliminate problems mentioned above, we propose a new approach of the landing gear design. For this, we made a methodology for design, simulation, testing for landing gear that constitutes the object of a research study comprised in the National Research Program. (Bogdan C. et al., 2005; Bogdan M.L. et al., 2007)
For the testing of the landing gear and the validation of the results obtained by virtual prototyping using in design and analysis of the landing gear, we adopt as a technical solution the design and realization of a stand (an invention) which will be presented in this paper.
This stand is designed so that the hydraulic action was be replaced by the electric and mechanical action. To reduce or even eliminate the hydraulic action is the main tendency in the modern aircrafts design because of the well-known inconvenience of the oil using. The stand conception answers perfectly to this tendency.
The equipment presented below permits the making of some tests, for example, the landing drop tests conform to Federal Aviation Regulation. The tests can be made on the landing gear scale model determining to reduce the costs and time.
Also, it offers the possibility to study the landing gear mechanisms by analyzing of the its dynamical behavior, to make a comparative analysis between different kinematical parameters and vibrations variations in some different operating and loading conditions in the retraction and deployment phases.
In addition, it can studied the influence the drop height and supplementary loading attached on the superior platform of the landing gear scale model (additional masses) relative to the different kinematical parameters of landing gear mechanisms.
As further research, we will continue the application of the new methodology of design, analysis and testing of the landing gear for different types of landing gear using the described equipment. (Bogdan M.L. et al., 2007; Otat et al., 2006)
2. THEORETICAL CONSIDERATIONS
The designed stand for the dynamical testing of the main landing gear scale model with twin dual in tandem wheels (figure 1) consists of a base plate made from aluminum alloy on which are fixed two cylindrical, vertical rods made from stainless steel face-harden at the exterior. These rods are used for sliding (raising and descent) of the landing gear scale model. At their superior part, the rods are made rigid by a rotative, cylindrical traverse made from duralumin on which is fixed a tambour with flexible cable from stainless steel for the raising and descent of the main landing gear scale model. The acting of the rotative superior traverse is made manually by a piston rod-crank mechanism that is drawn with a locking mechanism to lock on vertical of the sliding for the main landing gear scale model.
The retraction and the deployment of the landing gear scale model is made electro-mechanically by a gear (having a transmission ratio equal to 80/35=2,285) actuated by an electro-engine with reduction gear type snail-sprocket wheel with: [P.sub.n] = 36W and [U.sub.n] = 24 V.c.c. This electro-engine receives the command by a switch with three positions from command table supplied from a supply source of 220V a.c., 50 Hz. The scale model of the main landing gear is consists of: shock damper/absorber strut/leg, side strut, drag strut, truck beam, two shafts for the sustaining of the twin dual in tandem wheels, torsion links, trunnion. The shock damper is made of the cylinder and piston of the shock damper.
[FIGURE 1 OMITTED]
For the landing impact (drop) tests of the main landing gear scale model that have a mass equal to 8,360 kg this is drawn with two loads that are two cylinders from stainless steel having the masses of 5,580 kg, respective, 2,235 kg.
In the figure 1, the notations have the following significations, thus: 1 base plate of equipment, 2 guiding of landing gear model, 3 translation and rotative joints, 4 shaft, 5 locking device, 6 rotative superior trunnion, 7, 8 acceleration transducers, 9 superior plate of equipment, 10 reduction gear, 11 pivoting trunnion, 12 potentiometer transducer, 13 electric engine, 14 side strut, 15 drag strut, 16 actuator for shock damping, 17 acceleration transducer, 18 torsion mechanism, 19 piston of actuator, 20 inductive transducer, 21 acceleration transducer, 22 axles of landing gear model wheels, 23 truck beam, 24 landing gear model wheels , 25 command panel, 26 acceleration transducer, 27 current transducer, 28 signal conditioner, 29 signal conditioner for inductive transducers, 30 course limiting device, 31 additional load (1), 32 additional load (2). (Bogdan C. et al.,2005; Bogdan M.L. & Bogdan C.,2005 a ;Bogdan M.L. et al., 2007)
3. APPARATUS SYSTEM FOR THE TESTING OF THE LANDING GEAR SCALE MODEL
The parameters measured at landing impact (drop) tests of the main landing gear with twin dual in tandem wheels configuration are the following:
--the linear course at the landing gear drop at the landing, marked Crs (mm),
--the linear velocity or drop velocity of the landing gear at the landing, marked V (m/s),
--the linear acceleration or drop acceleration of the landing gear at the landing, marked Acc (m/[s.sup.2]),
--the acceleration of the vibration for the base plate of the equipment, market [Acc.sub.1] (m/[s.sup.2]),
--the acceleration of the vibration for the landing gear, marked [Acc.sub.2] (m/[s.sup.2]),
--the acceleration of the vibration for the shock damper cylinder, marked [Acc.sub.3] (m/[s.sup.2]),
--the acceleration of the vibration for the superior part of the landing gear, marked [Acc.sub.4] (m/[s.sup.2]).
Apparatus system for measurement and processing of all parameters mentioned above includes: accelerometers, transducers of linear and angular course, charge amplifiers, Tensometric Bridge, numerical acquisition of data interface and computer Notebook with software for acquisition and processing TestPoint-Keithley.
Test Point is a programming medium with a high performance, which achieves acquisition of data, numerical analysis, matricial calculus, processing of signals and graphical representation. The limits in the using of TestPoint are due to the performances of calculus system used. For graphical representation is used a proper graphics with two sliders can represent in Cartesian coordinates until 6 traces associated after necessity to one of four ordinates. For the processing of the signals, it is achieved a calculus program under the programming medium TESTPOINT.
This soft offers the possibility to make the following sequence of the operations: the effective values determination of the all parameters mentioned above for whole length of the testing period and the graphical representation of the experimentally determined specific features. It can be represent one or many parameters measured variations on the same graphic.
The graphics has two object-sliders to select the inferior and superior limits of the representation domain and other two object-sliders for the movement of the sliders. Data associated to traces in the slider position are displayed in a suitable display number associated by color with suitable traces. The tension signals supplied by the transducers of course charge amplifiers and tens metric bridge are applied to entering of numerical acquisition of data interface DAS 1602, where they are converted in numerical signals. The acquisition installment is 10000tests/s/channel, every recording contains 20000 samples. The numerical acquisition of data interface is used to realize the numerical conversion of electrical signals applied to the entering and to transfer these signals to computer for numerical processing. It is used a numerical acquisition of data interface type DAS 1602, made by Keithley, which has the following characteristics: number of entering channels: 8 differential/16 single End and overall frequency of sample: 100 KHz.
The course is determined considering as the reference point -the superior point of the drop. The transducer course is linear zed by soft using an interpolation table. The drop velocity is determined by the numerical derivation of the drop course. The drop acceleration is determined by the numerical derivation of the drop velocity. (Bogdan C. et al.,2005; Bogdan M.L. & Bogdan C.,2005 a,b)
The equipment presented in this paper is an innovation in the landing gear testing and design field. This equipment permits to measure of some kinematical parameters of the mechanisms, vibrations of some elements from landing gear structure for landing drop tests.
These parameters are measured and analyzed in some different operating and loading conditions in the retraction and deployment phases. The equipment can use for different types of landing gear.
Bogdan, C. ; Tempea, I. & Bogdan, M. L. , (2005). The Determination of the Kinematics of the Landing Gear, Proceedings of the Ninth International Symposium on Theory of Machines and Mechanisms SYROM 2005, pp. 429-434, ISBN 973-718-289-8, 973-718-290-1, Bucharest, September 2005, Printech Publishing House, Bucharest
Bogdan, M.L. & Bogdan, C. (2005). About Kinematics of the Landing Gear Assembly, Annals of the University of Craiova, "Mechanics" series, vol.I, nr.1, 2005, pp.5-10, ISSN 1223-5296
Bogdan, M.L. & Bogdan, C. (2005). Mechanics. Dynamics and Mechanical Vibrations. (in Romanian), "Universitaria" Publishing House, ISBN 973-742-329-1, ISBN 978-973742-329-0, Craiova, Romania
Bogdan, M.L.; Gherghina, G. & Popa, D. (2007). Aspects concerning Virtual Prototyping of Some Mechanisms from Landing Gear, 11th European Automotive Congress, 30 May-1 June 2007, Budapest, Hungary, Book of Abstracts, pp.228, Available from: http://www.diamondcongress.hu/eaec2007/binx/EAEC_Booklet_FINAL.pdf Accessed: 2007-07-10
Otat, V.; Dinca, L & Simniceanu, L. (2006). Aircraft landing run at the Asymmetric Braking, The 5th International Conference on Advanced Engineering Design, Prague, Czech Republic, June, 2006 (CD-ROM)
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|Author:||Bogdan, Constantin; Bogdan, Mihaela Liana; Simniceanu, Loreta; Dinca, Liviu|
|Publication:||Annals of DAAAM & Proceedings|
|Date:||Jan 1, 2007|
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