The first con cepts for a n ew EMA l ayout re sembled the V-1 32 / V-131 R atm ospheric test vehicle fla p  actuato rs. They we re based o n a linear ball scre w EMA in the  aft fuselag e, but mounte d remotely from  the flap, and drove the flap through a four-bar link age. Only the fin al link rod would penetrate the fus elage  skin and atta ch to  the flap  at the same location a s the original design (Figu re 4). Seve ral variants were   explore d, trading EMA size, po wer, l ocation, an d minimizin g rotat ion of th e final link rod relative to the  fusela ge lo wer skin or the flap. Initially, it wa s hoped that isolatin g the EMA it self fro m the flap bea ring  would elimina te the proble m of designin g a linear bal l screw to ope rate und er a sub stantial b endin g load  and th at pe netrating  the l ower skin with just a simple link rod would in crease the space available fo r the  thermal seal and re duce th e insul ation requireme nt for the lowe r rod. 

      SKINANCHOR POINTS EMA  ROCKER ARM  LOWER ARM SEAL FLAPSKIN EMA SUPPO RT BEAM SEAL        Figure 3.   Original lin ear EMA concept.                     Figure 4.  A conceptual 4-bar d esign 

Unfortu nately , the vari ous factors did not trad e very well. Reducing the amou nt of rotation require d from   the flap bea ring in crease d the amou nt of movement  relative to the ski n and thus in creased seal   compl exity. Redu cing the amount of mov ement relativ e to the  skin increased the amount  of rotation at th e  beari ng. M ost of the  configuration s drove the fin al link rod to a more disadvanta geou s angle with the  flap,   which increased the load s on the flap  bea ring and the fla p hinge b earings to pote ntially unacceptabl e  levels. Anoth er configuration minimized  the rotati on at the flap bearing a nd ke pt a better angle between   the link an d flap, but drove  the EMA power requirements quite high and pu shed it so far up and aft as to   be of serious concern  to the ove rall ve hicle center of gravity. Additionally, this g reatly complicate d the  thermal  seal. Estimates ulti mately indi cated that all of  the config urations would  involve a significant weight  growth, possi bly even double the or iginal desi gn. Stabilizing the comp lex actuator and l inkage t rain  again st out -of-plane  load s woul d have  introd uced addition al co mplexity and  weig ht, whi ch was not  accou nted fo r in the conceptual d esigns and whi ch may not hav e bee n achie vable. Finally , most of the  layouts resulted in a li nk rod size suitable for the bendi ng lo ads and relati ve motion th at actually  exace rbated the therm al seal de sign p roblem. Ultim ately, the four-b ar lin kage concepts fail ed to add ress  the ba sic problem of  requiring large rotations bet ween the actuator lin kage and the fla p through  the highfriction CSi C beari ng. 

New Design  

Eventually, it became apparent th at ba rring a breakthrough in high-temp erature be aring technolo gy, the  best chance for success required an actu ator co ncept that el iminated th e nee d for relative rotation   betwe en the final actuato r link and the fl ap. Simplifica tion of the relative motion betwe en the actuato r and  the fusel age l ower skin was necessary i n order to develop a reali stic therm al seal de sign using availa ble  techn ology. T here also re mained th e requireme nt for any  new actuator de sign to be comp atible with th e  existing fusel age an d flap stru ctures. 

Actuator L ayout  The mo st ob vious m ethod of achi eving  the first two goals was to shift the center of rotation  of the EMA   from in side the fuselag e to an axi s coinciding with the  axis of rotatio n of the  flap, but with out re quirin g any  380