Ecolifter Conceptual Configuration Design and Parameter Analysis

Journal of Beijing Institute of Technology ,2003 , Vol. 12 ,No.2Ecolifter Conceptual Configuration Design andParameter AnalysisTANG Sheng-jing( 唐胜景)( School of Mechatronics Engineering , Beiing Institute of Technology , Beijing 100081 , China)Abstract : In the phase of conceptually designing , the Ecolifter with three lift surface configuration , the infu-ences of aircraft geometric parameters and configuration such as wing geomtric parameters , canard parameters ,aircraft center of gravity and engine positions and so on，on flight dynamic stability are discussed with the inte-grated analysis method. On the basis of the analysis of flight dynamic stability , the suitable wing geometric pa-rameters are given and the improved aircraft configuration is proposed.Key words : aircraft design ; transport plane ; flight dynamicsCLC number :V211.92Document code :AArticle ID : 1004-0579 2003 )02-0149-05The Ecolifter121, a new type of transportplane ,is studied by the ACRT( i.e. Air Cargo Re>8.0° ,the root in spiral mode is getting posi-at first. According to the computation results , the ef-tive. .fects of a variation of the wing dihedral angle on theTab.2 Root variation in spiral mode with wing twist angledynamic stability in longitudinal motion are not sig-e,(°)-1.8 -3.8(ref. ) - 5.8-8.0nificant. But due to the variation of the wing dihedralroot in spiral mode -0.001 70 - 0.001 20 -0.000 60 - 0.00002angle , aerodynamic derivatives in lateral-directionalmotion, the sideforce due to sideslip derivative , theAs can be seen for these two wing parameters , inrolling moment due to sideslip derivative( called dihe-airplane design it is necessary to consider the require-dral effect ), the rolling moment due to roll ratements of dynamic stability as it is proposed for the in-derivative and the rolling moment due to yaw ratetegrated conceptual design in this project. And the ef-derivative are changed. Therefore ，variations of thefects of these parameters on flight dynamic stabilty ,wing dihedral angle influence the characteristic equa-especially in lateral-directional motion should be ana-tions in lateral-directional motion. The effects of thelyzed. On the basis of flight dynamic stability ，forwing dihedral angle on the roots in roll and Dutch rollparameters of wing dihedral angle ，the magnitudemodes are relatively small. But the root locus in spiralshould be larger than F=4.3° . And wing twist anglemode changes significantly with the variation of theshould be |e1<8.0°.wing dihedral angle as shown in Tab.1. With an in-3Fffertf. of Configuration on Dy-crease of the wing dihedral angle T from 4.0° tc中国煤化工6.0°，the roots in spiral mode are changed fromYHCNMHG0.00054 to - 0.002 90. It means that ,as F=6.0°The dynamic stability of the ecolifter referenceis larger than the reference datum of T= 5.0° , themodel has been analyzed6-81. If the configuration is .dynamic stability in spiral mode becomes larger. Con-changed，the dynamic stability will be affected.一150一TANG Sheng-jing(唐胜景)/ Ecolifter Conceptual Con. figuratio Design and Parameter AnalysisConsidering the variations of configuration of Ecol-namic center position , there are almost no effects ofifter , such as the parameters of canard , airplane cen-the canard area on the dynamic stability in lateral-di -ter of gravity , and engine positions and so on , therectional motion.dynamic stability in longitudinal and lateral-direction-The effects of the airplane center of gravity onal motion have been discussed.the dynamic stability are discussed , with the move-The ecclifter reference configuration is a three-ment of the airplane center of gravity towards thelift-surface airplane with a canard-wing- tail combina-wing aerodynamic center from 0.050c to0.220 c( ction. With the variations of canard aerodynamic cen-is the wing mean aerodynamic chord ) , due to the de-ter position and canard area , the reference configura-crease of the static longitudinal stability |Cm| andtion will be changed. The characteristics of the sys-tem construction will be varied. Those variations willdCL, the root locus in short period mode of longi-influence the dynamic stability of the airplane system.tudinal motion tends towards the Im axis , and ζ isWith the variations of the canard aerodynamic centerincreased quickly , but con is decreased. At the sameposition , the upwash at the canard changes , and thetime , the airplane center of gravity movement affectsairplane center of gravity varies too , which will resultthe dynamic stability in phugoid mode. But , on thein the variation of aerodynamic parameters , especiallydynamic stability of lateral- directional motion , the ef-stability and control derivatives in longitudinal mo-fects of the airplane center of gravity are not obvious.tion. Thus , the dynamic stability and behavior pa-The roots in short period mode are changingrameters will be affected by the movement of canardfrom complex roots to two large real rootsif Xr{ Xrefaerodynamic center position.is the distance between CG and leading edge of wingIn short period mode of longitudinal motion , theat c )is over 0.250c. And the roots in phugoid modeinfluences of the canard aerodynamic center positionchange from negative real parts to positive real parts ifon the dynamic stability are obvious. The dynamicXref is moved over 0.265c , which leads to instabilitystability becomes smaller , with a smaller damping ra-in phugoid mode. From the point of view of prelimi-tio, and a bigger undamped natural frequency wn，nary design , the airplane center of gravity CG shouldwith the movement of canard aerodynamic centerbein front of a. c. ( aerodynamic center ), in otherbackward relative to the airplane nose point in shortwords , the aft CG limit is determined by the locationperiod mode. Contrarily ,it is relatively small for theofa.c. With respect to dynamic stability，especiallymovement of canard aerodynamic center to affect thefor freighter aircraft , the airplane center of gravitydynamic stability in phugoid mode. In lateral- direc-should be taken under special consideration.tional motion ,it is not evident.Unlike the engine reference positions , two en-Like the variations of canard aerodynamic centergines are fixed above the wing , and other two engineswith the dynamic stability , the effects of canard areaon the fuselage. Compared to the engine reference po-on the dynamic stability are very apparent in shortsition，with two engines on the fuselage moving to-period mode of longitudinal motion , the dynamic sta-wards the nose point , the roots in longitudinal motionbility tends to become larger with an increase of themove away from the Im axis , and the dynamic stabil-canard area from0.810 Sc to 1.210 S6 Sc is the ca-ity gets smaller. And this leads to a smaller dampingnard reference area ) , in addition , damping ratio ζ isratio , the larger undamped natural frequency , com-increased from 0.697 to 0.821，but the undampedpare中国煤化工position. In phugoidnatural frequency wn is decreased from 1.490 tomocHC N M H Gatio and undamped nat-1.320. In phugiod mode , the root locus changes onlyural frequency are opposed to those in short periodsubtly. That is to say , ζ，wn vary slightly with themode. In lateral-directional motion , the roots in spi-variation of canard area. Similar to the canard aerody-ral mode are unchanged ，in roll and Dutch roll一151一Journal of Beijing Institute of Technology ,2003 , Vol. 12 ,No.2modes , the root locus tends to the Im axis with ansign integration , dynamic stability improvements areengine position moving aft.discussed below.Assuming that the canard aerodynamic center4Example for Improvement of Dy-position moves 2 m backwards , and the canard areanamic Stabilitydecreases by 0.810Sc , with an engine position givenAt a cruise Mach number of0.7 in FL 310 ,the .as Xe = 48 m, and an airplane center of gravitydynamic stability is analyzed for the ecolifter referencechanged to 0.103c through a weight adjustment forconfiguration. The reference configuration system irthe main deck containers , the dynamic stability willlongitudinal and lateral-directional motion is stable.be changed. The effects of those parameters on theHowever ,a quickly convergent damping ratioof ζ=dynamic stability in lateral -directional are relatively0.751 is quite high , which is not good for control.small. But the effects of those parameters on the dy-Therefore , having assessed the effects of airplane panamic stabilty in longitudinal motion are remarkable.rameters on the dynamic stability , the following paThus, the comparisons of the dynamic stabilty inrameter combination is proposed. On the basis oflongitudinal motion between reference configurationthese research results in section 3 ,in the view of de-and combined parameter variation are listed in Tab.3.Tab.3 Comparisons of longitudinal dynamic stability between reference and variationmode .caseeigenvalueζw,/(rad s-1)reference- 1.057 4土i0.929 60.7511.410 0short period modevaried parameters- 1.0578士i1.26030.6431.650 0-0.003 2土i0.079 60.0400.079 7phugoid modevariedparameters-0.0034士i0.079 70.0430.0798The change of those airplane parameters influ-tion from the point of view of dynamic stability is giv-ences directly the airplane system quality. As seen inen. In this configuration , the position of the canardTab.3 ,in short period mode of longitudinal motion ,aerodynamic center is moved backward for 2 m andthe damping ratio ζ is decreased from 0.751 for thethe canard area is reduced to 0.810Sc ithe engine po-reference to 0.643 for the parameter variation. Thesition is changed ，instead of locating all 4 enginesundamped natural frequency Con is increased fromabove the wing ,2 are located above the wing and be1.4100 to 1.650 0. That means , the varied parame-tween the engine positions in the reference layout ,ters influence the dynamic stability behaviors of theand the other 2 are fuselage mounted. This improve-reference configuration system , resulting in a lowerment is beneficial to the airplane control performance ,damping ratio , a higher undamped natural frequency ,as control response becomes quicker and the large air-a shorter period of oscillation , but with a larger am-plane is easier to control. Therefore , the referenceplitude , and a more oscillatory transitional process forsystem quality of dynamic stability has been im-the response to a control input signal. Therefore , theproved , resulting in an airplane system that meets thereference system quality of the dynamic stability hasrequirements for a novel cargo aircraft.been improved.In phugoid mode , the effects of these parameter5 Summaryvariations on dynamic stability are not so significant ,中国煤化工ntegrated research apbut dynamic stability tends to become a bit larger. Inproa.MYHC N M H G, including mass , aero-addition , the effects on the dynamic stability of later-dynamics and dynamic stability is proposed for air-al- directional motion are very small.plane parameter selection and the improvement of dy-As a result of this thesis , an improved configura-namic stability.一152一TANG Sheng-jing(唐胜景)/ Ecolifter Conceptual Con. figuratio Design and Parameter AnalysisWith this method ，analyses of configurationAcknowledgementsvariations have been investigated by changing the pThe author would like to thank Prof. Dr. Drameters in the phase of airplane conceptual design.Schmitt for his instructions during the research work ,The analysis tool established for this study allows anand Prof. Dr. O. Wagner for his help during the re-easy parameter variation and thus a quick configura-search on dynamic stability.tion reassessment. On the basis of these sensitivityanalyses with regard to dynamic stability in an inte-References :grated conceptual design , an improved configuration[1 ] Schmitt D , Roeder J. The Ecolifter : A new concept for ahas been developed and the reasonable weight distri-dedicated advanced cargo transpor[ A] ICAS. Proceed-bution with the cargo containers arrangement hasings of the 21st ICAS Congres[ C] Melbourne : ICAS ,1998.been proposed.As aerodynamic and structural constraints are[2] Metzger R , Schmitt D. Ecolifter- -Ein Luftfrachtkonzeptzur Entlastung des bodengebundenen GiuterverkehrsC A]very often in conflict and as performance and handlingDGLR. DGLR-Jahrbuch 2001[ C] Hamburg : DGLR ,qualities are of high importance in aircraft preliminary2001.design , with the approach outlined in this thesis , dif-[3] Tang Shenging. 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