CONTROL SURFACES

FIELD

J0S013 The embo ments disclosed herein relate generally to testing apparatus, sys ems and methods for obtaining measurements pertaining to aircraft surfaces, ©specialty measurements pertaining to the free play and oackiaah characteristics of aircraft control surfaces.

BACKGROUND

[0002] The free play of m a rcraft ^' s control surfaces physically Introduces decreased rigidity effects into the aeroeiastic system, Such ^' decreased rigidity effects attributable t such free play may in some cases be sufficiently large to cause iirnlt cycle oscillations (LCD) in the surfaces that use surface rigidity to suppress flutter. The ICO can in turn reduce the aircraft fatigue !tfe or, in certain extreme cases cause catastrophic failure, A free pla test is therefore required to be con ucted on an aircraft's control surfaces before an aircraft can be -released for

conducting a Flight Flutter Test (FFT) so that the free pla is characterized and the aircraft safety is warranted >

£0003] Once the free play of a control surface is determined, according to the tVf!L 8870C standard (Incorporated by reference herein!©), other tests are necessary in order to monitor free play evolution do ring the aircraft service life. These other monitoring tests of free play are known as backlash tests which are performed by the manufacturer before aircraft delivery and by the operators during aircraft service life.

{0004] Irs order to guarantee the aircraft safety, both the military and the FAA have published standards that define the amount of free play allowed on different aircraft control surfaces for the aircraft service life, irt addition, these standards provide set points t intervals throughout the aircraft service life in which backlash must be tested..

[δ δ§] ^■ Free play of aircraft control surface can be tested statically or dynamlcsaily. Dynamic free play testing Involves the placement, of acceterometers In or on control surfaces with the surfaces thereafter being vibrated: by shakers or actuators so that the free play cart b© monitored by a computer system- However, this type of dynamic f ee play testing system is generally applied to control surfaces of larger aircraft and allows for the correlation of the vibration frequency and the free play of the control surfaces which is not possible to obtain with smaller and medium sized aircraft One such conventional dynamic free play testing system Is known from U.S. Patent No. 7 _r S33,681 Issued on April 26. 2011 (the entire content of which s expressly incorporated hereinto by reference), CSCiS] Because of the deficiency noted above with respect to dynamic testing,, smaller and medium sized aircraft must have free play statically tested. Currently, however, static testing of the control surfaces is performed by applying a known load to the control surface and then measuring: the corresponding deflection (linear measurement r angular displacement}. I this regard, a typical static free play test is started a zero load and increased to soma percentage of ultimate load. During testing, the moment or applied load is plotted versus displacement i.e., to provide a UD plot For a control surface with no free play and a linear spring stiffness, the UD plot is a straight line wtfii the slope of the line being the measured spring stiffness. As free pla is Introduced into the system, a discontinuity in the curve occurs near the zero load range. For larger displacement values the slo e increases and is more

representative of th effective stif ness without the free play. As hysteresis is introduced into the system, the UD pfot forms a known type of curve. O 7J 1¾e. son veotlonal stafe fm® ptey test method Is --tsmefy _T rel tively conipisM:si!n ^: G¾ tfi ten in dfe os :Eiif si_js. fixed physiesSiy.

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oper&tivefy conneetabie to the aircraft control surface to output a deflect ion measurement signal indicative of the aircraft control surface.

[M11J Each of the attachment assembiies includes am adjustable stem and attachment suction cup ttached to an end of the stem for lacement against 3 surface of the aircraft structure. Additionally or alternatively, the actuator may include an actuator suction cup attached to a terminal arid of the actuator shaft for lacement against a region of the aircraft control surface, A swivel joint may attach each of the attachment and/or actuator suction cups. A vacuum line may be attached operatively to each of the attachment and actuator suction cups and in torn attached to a vacuum source for drawing a vacuum within each of the attachment and actuator suction cups,

|0Q12J According to some embodiments, the dispiacernerit transducer ma inclu e a transducer support extending laterally of t e transducer towards the aircraft structure for mounting t e displacement transducer in an operative position relative to the aircraft control surface. At least on mounting foot may be provided with the transducer sypport for contacting the surface of tie aircraft structure.

[0S13J Systems for determining free play of a moveable aircraft control surface mounted to a stationary aircraft structure for

displacements about hinge axis will include a testing apparatus as briefly described above, and a control system operatively connected to the testing apparatus. The control system thus receives the load arid deflection signals from the load cell and displacement transducer,, respectively, to provide a load versus displacement diagram herefrom and thereby determine free play of the aircraft control surface,

E fi14J The free play of a moveable aircraft control su face mounted to a stationary aircraft structure far displacements about a hinge axis may therefore be determined by posHionally fixing the testing apparatus to a surface of tie stationary aircraft structure sueh trial the act ator shaft and the displacement transducer are in contact with respective regions of the moveable aircraft control surface. T e testing apparatus may be

operaHvely connected to a control system to receive the load and deflec io measuremen signals output by the load cell and the displacement transducer, r s ecti ely, Operating the control s stem will thereby actuate the actuator and thus cause the actuator shaft to apply repetitive toads to the aircraft control surface.. pJ15J Simultaneously w th the actuation of the actuator, the load and displacement measurement data associated with the repetitive appied loads are collected fern the toad and deflection measurement signals output by ihe load cell and the displacement transducer. A load versus displacement curve based on the collected toad and displacement data may be determined rom s«ch collected data. The free play of the aircraft control surface may thereby be determined from Ihe load versus displacement curve,

|0§1S] These and other aspects and adva tages of the rese t Invention will become mom clear after careful consideration is gi en to the following detailed descriplon of the preferred exemplary embodiments thereof..

BRIEF DESCRIPTION Of ACCOMPANYING D AWI GS

£0i1?j The disclosed embodiments of Hie present invention will b better and more completely understood by referring to the following detailed description of exemplary non-1 smiting illustrative embodiments in conjunction with the drawings of which:

[DCH0] FIG, 1 Is a schematic view of a system: according to an embodiment disclosed herein for the static testing of free-play and backlash associated with an aircraft control surface; 30193 FIG. 2 & schematic block flow chart diagram of an operational sequence theft may be em loyed In the system depicted in FSO, 1 ; and S203 FIG, 3 ss art exemplary Load-Defection data plot that may be obtained with the system depicted in FIG 1

DETAILED DESCRIPTION

[O021J Accompanying FIO. 1 schematieal^r depicts a testing s ste 10 for statically testing free play and backlash of an aircraft control surface ACS which is operative^ associated with art aircraft airfoil structure AAS. Specifically,, the aircraft contra surface ACS is capable of controllable deflections about a hinge axis HA relative to the stationary aircraft airfoil structure AAS, in general, the testing system 10 cco di g to the embodiment depicted schematically tn IG, 1 includes an

eiectromechanlcaf testing assembly 10-1 physically and operativeJy attached to the aircraft control surface ACS and the aircraft asrfotl structure MS, and a control system 10*2 operatively connected to the testing assembly 10-1 to control the test parameters and collect the test data,

[0022] The testing assembly 10-1 s provided with a support structure 12 which includes a plurality of attachment assemblies 1 to physically attach the support structure 12 to the aircraft airfoil structure AAS, Each attachment assembly is provided with an attachment suction sup 14a connected to an adjustable stem 1 b by a swivel connector 14c. The adjustable stem 14b is in turn coupled to the support structure 12 to allow ft to be reciprocal linearly adjusted to allow its associated attachment suctton cup 14a to be moved towards or away from the aircraft airfoil structure AAS, The stem 14b ma in some embodiments be th readably connected to the su port structure 12 to allow such adjust bl

8 movements. The swivel connector 12c assists to enstt e proper positioning of the attachment suction cup 14a onto the curved airfoil surface of the aircraft airfoil structure AAS.

[0023] In such a manner therefore the attachment suction cups 14a associated with each of the stem 14b may be mo ed into direct physical contact in a. slightly compressed state with the aircraft airfoil structu e AAS so as to permit the support structure 12 to be mounted in a fixed spaced relationship thereabove.. The attachment suction cups 14a are connected to a vacuum source 6 by vacuum lines 18a which operate to draw vacuum within the cups 1 a to ensure that each is positionaily fixed to the aircraft airfoil structure AAS and thereby provide positional stability to the support structure 12,

[8β24| The support structure 12 supports an electrically operated actuator 18 having a rectiiine rly moveable actuator shaft 8a terminating with an actuator suction cup 18b. The actuator suction cup 18b is connected to the terminal end of the actuator shaft 18a by a swivel joint 18c in a manner similar to the attachment suction cups 14a and support stems 14b to allow a direct fixed connection between the suction cup 18b and the aircraft control surface ACS, The actuator suction cup 18b is likewise operativeiy connected to the vacuum source 16 by the vacuum Sine 16a, A load cell 20 is operativeiy associated w th the actuator shaft 18a of the actuator 18 to sense the defection forces during testing,

£0025] A linear displacement transducer 22 is provided with a lateral transducer support structure 22a with mounting feet 22b, 22c which allow for operativeiy positioning relative to ie moveable aircraft control surface ACS. In such a manner, the linear displacement transducer is f¾ed to the stationary aircraft airfoil structure AAS to allow the transducer 22 to be placed in operative contact with a portion of the moveable aircraft control surface ACS. The extent of angular detection of the moveable aircraft, control surface ACS relative to the stationary aircraft airfoil ^' structure AAS during testing ^' will therefor© be sensed by the linear displacement twsducec 22.

[§026] The control s stem 10-2 includes a conventional personal computer 24 having suitable non-volatile memory which may include data storage media, a data entry keyboard and a display. A dat conditioner 26 Is provided to collect the angular deflection data and the force data sensed by the load cell 20 and the linear displacement transducer 22 and transmitted thereto. The data conditioner 26 Is operative^ connected to the computer 24 so the conditioned dais may e stored and/or further manipulated thereby, A servo-dnver 28 operatively interconnects the transducer 18 and the computer 24. 0027] Accompanying FIG. 2 Is a block diag m de cting an exemplary operational procedure for conducting a free play and backlash test using the system how I FIG. 1. In this regard, It will be observed In block 100 that the test will Initially be set up for the particular moveable aircraft control syrface ACS being tested and involves the initial positioning of the testing assem ly 10-1 relative to the moveable aircraft control surface ACS and the stationary aircraft airfoil structure AAS. Once the testing assembly 10-1 has been properly positioned, the vacuum system including the vacuum source 6 Is operated in step 102 to thereb positlonally fix the testing assembly 10-1 relative to both the moveable aircraft control surface ACS and the stationary aircraft airfoil structure AAS,

£002-83 After setting up the tes in step 100, data from the load point arms of the hinge axis of the aircraft control surfac ACS is Input into the computer 24 in ste 1 4. The computer 24 comprises software stored in its nonvolatile memory that manages the test and computes the free play. The computer 24 also allows the parameters {toad and displacement) to be set to zero in step 106 before the start of the actual free play test. Following step 108, the f ee pla test may be started in step 08. In this reg rd, the computer 24 e ecutes a loading command vta the servo-driver 28 and the data acquisition for three subsequent repe&tioos s obtained via the data conditioner 26, The loading command thus causes the transducer 18 to operate so that compression- and tension, forces are sequentially exerted onto the moveable aircraft control surface ACS t>y means of the actuator shaft 18a and #*e suction cup 8b< The resistance forces acting in response to these compression and tens ton forces are ifius sensed ¾f the ansdycar 20 and acquired slmuftaneousiy with the

.deinmen ^ &Q29] According to one embodiment, after the t ird repetitive loading and data acquisition cycle is completed, the computer 24

'automatically stops the test end the data acquisition In step 110.

However, -at any time during testing the loading and data acquisition cycles may be stopped in step 110a should there be a need.

Data is saved from the test in step 112 and a load versus deflsc&on (UD) curve is obtained as depicted in accompanying FIG> 3,. The L D curve or parts -of the L/D curve are then selected in step 114 by fitting a tangent line to each of the associated upper end lower curve parts associated with each of the tension and compression force cycles. Free play may tften be computed oy algorithms stored in the computer 24, specifically b computing the difference of the derivatives of tie upper . {tensile loading - Free Play A) and tower (compression loading - Free Play 8) loading curves as shown in FIG, 3. The free play for the tested aircraft control surface ACS is considered to be the greatest value obtained from the calculation nd Is thereby input as the ^" free play test result in step 116. [0031] F tSow ^" ir¾g the detem ination of the free p!ay test resuSt, the vacuum s stem, Inclu ing the vacuum source 16, may be turned off in step 11B nd the testing as em ly 10-1 removed from the aircraft airfoil structure AAS and the aircraft control surface ACS and reattached to other simi ar structures for testing.

[0632} it will be understood that the description provided herein is pre&entty considered to be the most practical and preferred embodiments of the invention. Thus, the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover variou

modifications and equivalent arrangements included within the spirit and scope thereof.