ARE No. L5I20 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WARTIME REPORT ORIGINALLY ISSUED February 19^6 as Advance Eestricted Eeport L5I20 FLIGHT MEASUREMENTS TO DETERMINE EFFECT OF A SPRING-LOADED TAB ON LONGITUDINAL STABILITY OF AN AIRPLANE By Paul A. Hunter and John P. Reeder Langley Memorial Aeronautical Laboratory Langley Field, Va. -'-^W^'^ffl?- %*-««— ,^«.afe- -.,:™^ »-ai«Hl lgS5!BflBR&43B?BMOi-.«.._™,— WASHINGTON NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were pre- viously held under a security status but are now unclassified. Some of these reports were not tech- nicadly edited. All have been reproduced without chsuige in order to expedite general distribution. 210 DOCUMENTS DEPARTMENT Digitized by tlie Internet Arcliive in 2011 witli funding from University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation http://www.archive.org/details/flightmeasuremenOOIang NACA ARR No. L5I20 NATIONAL ADVISORY COI^/IITTEE ^?OIi AEFIONrtlTTICS ADVANCE RESTRICTED REPORT PLIGHT MEASURI3ViENTS TO DETSKIIITE EFFECT OP A SPRINJ-LOADSD ^A3 ON LONGITUDINAL STABILITY OP AN AIRPLANE B.7 ■'^aul A. Hunter and John P. r>.eeder SIP-iyARY In conjunction vv'lth a program of researcli on the general prooleir. of stability of airplanes in "che climbing condition, tests have been -lade of a spring -loaded tab, which is referred to as a "snrlngy tab," Installed on the elevator of a low-wing scout bo'uber . The tab was arrctn^^ed to deflect upward with decrease in ?:t)Qg6, , vifhi ch caused an increase in the pull force required to trim at lov/ speeds and thereby increased the stick-free static longitudinal stability of the airolane. It was found that the springy tab would increase the stick-free stability in all flight conditions, would reduce the danger of inadvertent stalling because of the definite pull force required to stall the airplane with power on, v\fould reduce the effect of center-of -gravi ty position on stick-free static stability, and v.oald have little effect on the elevator stick forces in accelerated flight. Anotlier advantage of the springy tab is that it might be used to provide ahnost any dosired variation of elevator stick force v/ith speed by adjustin;^ the tab hinge -liionent characteristics and the variation of spring moment with tab deflection. Unlike the bungee and the bobweight, the springy tab would provide stxck-free static stability without requiring a "oull force to hold the stick back vvhile taxying. A device similar to the spi'ingy tab i:iay be used on the rudder or ailfjrons to eliminate undesirable trini-force variations with sceed. INTRODUCTION The National Advisory Comniittee for Aeronautics has initiated a -Drograrii of research ^n the general orobleii of KACA ARR rJ'j, L'ST.20 the staloility of airplanes in the climbing condition. In conjunction vie trailing edge of the springy tab in order to adjust the floating angle of the tab, and stops were provided to limit the upv/ard deflection of the springy tab to 21^ and NACA ARR Ilo the downward deflection to 0^. Photographs of the springy- tab installation are given as figures h and 5- Unless otherv/ise noted, the variation of springy-tab hinge i.iocient with springy- tab angle (as measured on the ground) was as shown In figure 6 and the angle of tiie subtab upv/ard from the springy-tab center line was approximately 6.5'~'« The relation between the elevator angle, measured from the stabilizer, and the stick position is shown in figure 7° The friction in the elevator system Is indi- cated in ficure S to be of the order of ±Z~ pounds. The •to 2 airplane was fitted with a bobweight that reLiulred a stick pull force of aoproxinately 5 'oounds. The bob- weight, Wiiich was installed for the tests of the airplane with the original tab and with the springy tab, is a pro- da;ction installation and had no effect on the relative stability c^f the tv/o configurations. Elevator angle, elevator stick force, springy-tab an.^'le, velocity, acceleration, and time were d.eteri:iinej from standard NACA recording instr-'jiiients . Slevctor angles were measured from the stabilizer in all cases. The airspjeed used tiirougli- out, called correct service indicated c.irspeed, is the airspeed that '.vould be ^^aven by a standard aN airspeed meter if it were connected to a pitot-statlc system free from position error and is defined by Vi ^s = ^5.0e fo \/q, wnere V- correct service indicated airspeed, m.iles per hour Tq standard sea-level coriipressibillty correction factor q.^ measured difference between total and static pressures corrected for oitct-static pDsition error. Inches of water The ele vatcr-system mechanical advantage was changed between the time that the tests of tlie airplane with the original tab and the tests of the airplane with the soringy tab '.vere made. 'Une stick forces for the airplane it ■ EACA hliR No. L5i::^0 with the original tab, hov;ever^ have been corrected to correspOiid to the ;r[echanical advantage of the airplane vjith the springy tab installed. RESULTS AITD DISCUSSION Static Longitudinal Stability The first severy.1 flights v-ei-e made to adjust the characteristics of the springy tab to ^ive the desired effects on the static longitudii:ial stability. In these flights, the speed ran^e over vvhich the tab operated vvas found to be too sniall and the fraction in trie tab system, too large. These faults ivere corrected by adjusting the tension in the spring, by adjusting the angle of the subtab, by changing the position of the linic joint on the tab, and by installing ball bearings in all moving joints of the springy-tab system. Unless otherwise noted, the data on static longitudinal stability are from flights made subsequent to these changes. Figures 9(a), 10(a), 11(a) and (b), and 12(a) show the static longitudinal stability characteristics of the airplane at both forward and rearv'/ard center-of -gravity nositions with the soringy tab installed. The test flight conditions are defined in table I. Comparable data pre- viously obtained with the airplane having the original tab locked at zero deflection ar-e shown in fi^,ures 'i{o), 10(b), 11(c) and (d), and 12(fc). The stic]c-free stability characteristics oX' the airnlane with tihe original tab and of the airplane with the springy tab are compared in figure 13 for the climbing and gliding conditions at the rearward center-of -gravity position. The ooints indicated as SDot runs were obtained from shjort records taken while the airplane V'/aa in equilibrirLm in a given flight condi- tion. The points designated continuous runs were read from longer records during which the speed was slowly decreased. The effects of tno springy tab on the static longi- tudinal stability of the airplane as coiiipared with the effects of the original tab (figs. 9 to 15) may be summarized as follows: (1) The springy tab inci'etised the stick-l'ree stability in all flight conditions as manifested by larger negative NACA ARR No. L5l20 slopes of the curves of ^^^vdo^^x o u_n^iv xuJ.^^c ag^c speed. In povver-on fli,_3ht with tlie center-or-gravlty position at approximately 32 percent of the mean aerocy- na-nlc chord - a condition in which the airplane vt'i th the original tab had a large degree of instability tjoth stick fixed and stick free - the vax'iation of stick force Vifith airspeed became stable throughout 'che speed range. In the power-off conditions, for v;hich the airplane vvith the original tab was stable, the null forces required to trim at low speed were Increased by the springy tab to an extent that was considered so;.iev;hat objectionable by the pilots, although the pull force never exceeded ^0 pounds. Some lightening of the pull force at the stall occurred In cases in which the springy tab reached its maximum deflection a fev/ miles oer hou.r above the stalling speed but stick-force reversal occurred only in the landing condition at the rearward center-of-gravity position. Because the springy tab reached its stop at zero deflec- tion at approximately 2S0 miles per hour, the highest speed of the springy- tab tests, it ivould be expected to have no effect on the stability at higher speeds, (2) The springy tab tended to reach maximum deflec- tion at a speed near the stalling speed for all flight conditions despite the variation of stalling speed with flight condition. The increased dynamic pressure on the tail in power-on conditions probably accounts for the fact that the tab reached its maximum deflection at a lower speed in these conditions. (3) The springy tab reduced the effect of center-of- gravity position on the stick-free static stability. The curves of elevator stick force against airspeed, with the s-oringy tab installed, almost coincide in the low-speed range at the two center-of-gravity positions tested. The increased up-elevator deflections required for trim with the LiOre-forward center-of-gravity positions resulted in smaller upward deflections of the tab because of tne aero- dynai:.lc hinge m.oment , due to elevator deflection, acting, on the tab. (I4.) The stick-fixed static longitudinal stability was sliglitly decreased by the actloiicf the springy tab, as shown by the smaller up-elevator or la.rger down- elevator deflections required for trim ao low speeds with the springy tab in operation. ITACA aRR iv'o. LSI 20 I>7namic Lom'ituc'.inal Stability 'o The results cf the static- stability taeasurer.ients indicated that the airplane with the springy tab installed was stable v/ith the stick free in all flight conditions. For conditions in which a large amount of stic'c-fixed / instability existed, it was considered desirable to investigate whether the airplane with the springy tab installed would tend to return to its triir. speed if the speed were changed slightly and the ontroi stick released, The results of bests made in t.ie cll^nbing cine, gliding conditions in ivhich the stick was released at a speed slightly above the trliri speed are given in figure li+. In the climbing condition (fig. llj.(a)), the airplane did not tend to return to its trim speed but instead the speed increased slightly at I'irst. The stable variation of stick force with speed, in this condition (fig. 9(^)) would give a change in sticl: force of less than 2. povnds for this change in trim soeed. This a^iount of change in stick force is less than the friction in the elevatoi'' control system. The elevator therefore remained essentially fixed during this n-.aneuver and the initial divergence froM the triiTi speed was caused by the stick-fixed instaoility in this flight condition, Svor'e sli-jht up-elevator motion occurred near the end cf the :naneuver and prevented the speed fro^i continuing to increase,' in fact; the speed a-o-carentlv began to decrease slightly o-' •y In the gliding condition (fig. l.v(b)), the airplane initially tended to return to its trir; speed. That this stable tendency was due largely to the action of the SDringy tab rray be seen from the notion of the elevator when the stick r/as released. The airplane also had a small amount of stick-fixed stability in this condition (fig. 10(a)). Some lag in the action of the tab is Indicated in figure lL(b) and may have been caused partly by the small ainount of friction in the tab systen; and partly by the elevator notion. Because the airplane was not in steady flight, the elevator an;-_.les in these tests did not becir the sairie relation to airspeed as in the static-stability tests (fig. 10(a)). The lag in the action of the tab rr.ay have, caused the instability of the long-period oscillation shown in this figure, Tiie sta- bility cf the oscillation for the airplane with the original tab was not investigated. Since the character- istics of the long-period oscillation have been shown by orevious investigations to have no correlation -with the IJACA ARR No, L5I20 7 handling qualities of an airolane, the oscillation shown in figure 1J4 ( b ) is not believed to be objectionable. The failure of the sDringy tab to cause the airplane to tend to return to its trim speed v;hen disturbed, in flight conditions in virhich the airpla.ne was verj unstable v;ith stick fixed, indicates that this device cannot over- coir.e a deficiency in sti c'.c-f ixed stability, ct least not Vifith the sane amount of friction as was present in the control systeirj during these tests. The oil^r-'ts did not consider the character j, sties oi" the airplane to be satis- factory for any flight condition in .\?hlch it was unstable with stick fixed,- although they believed that the control characteristics were iriinroved by the springy tab. One advantage of the 3T)ringy tab is the reduced danger of inadvertent stalling. v;ith the springy tao in operation, a definite pull force was required to stall the airplane; whereas, v;ith the original tab, a large oush force v/as required to prevent the stall in power-on conditions . Accelerated. Plight stick force and spi^lngy- tab angle with norii'.al acceleration in turns at 196 miles per hour is shown in figure I5 . Comparable oata for the airplane v.'ith the original tab are given in figure 16 . The springy tab aopeared to have little effect on the elevator stick forces in accelerated flight. For the springy-tab system, the test results showed a slightly lower slope of the curve of elevator stick force with noriral acceleration at rearward, center-of -gravi ty posi- tions, as -nay be seen by cornoaring figures IS and 16. The effect of the tab on the force per g norinal accelera- tion would be expected to be greater with the rcore-forward center-of -gravity iicsitions because a larger change in elevator angle would be required to produce a glvon accel- eration and a greater tendency for the tab to I'loat down would exist. The slight friction in the tab systein may have caused the flight measurements to differ fron the expected tendency. 8 FaCA aRR No. L5I20 Take-offs Time histories of take-offs of the aii-plane with a forward center-of-gravity position are given in figui'^es 17(a) and (b) for the springy-tab installation and for the original tab installation, respectively. The tirne history of a take-off with a rearv/ard center-of- gravity position and the sprine,y~tab installation is given in figure 17(c). j.'ith the springy tab, the airplane v^as said to ev.hibit a tendency tov/ard automatic take-off. Several of the pilots stated that at the start of the take-off the elevator moved down and then at an airspeed of about 80 miles oer hour moved uo of its o'iVj. accord and pulled the airplane off the ground. The action of the springy tab that -orocuced this tendency i;.ay be seen in figures 17(a) and' I7 ( c ) , At the start of the take-off the springy tab '.vas at its maxiriium up deflection, which produced a dov/n-elovator no veirient ; at about ^-J iriles per hour, the springy tab started to nove dovvn and thereby permitted the elevator to rove up. CoinT:>arison of the elevator stick forces for the springy-tab installation (fig. 17(a)) with those of the airplane v;ith the original tab (fig. 17(b)) shows the forces required for the air- plane with the springy tab to be less than those for the airplane v;ith the original tab. Apprcxiiiately one-half as much push force was required vilt'n the springy tab to lift the tail off the ground although the cov/n-elevator deflections were greater v/ith this installation. Trim-I^orce Changes All pilots who flew the airplane with the springy tab comiriented on the apnarently large trim-force change with power. This and other trim-force changes are com- pared in table II with those for the d.lrplane with the original tab for speeds of 120 and 100 iiiles per hoi-ir. These data were obtained by trimming the airolane first in the climbing condition and making successive changes in configuration and then trimming in the landing condi- tion and making successive changes in coiif iguration, with records taken after each change. The oull forces required to maintain trir.i. on closing the throttle with the flups up were considerably larger >with the springy tab installed (table II). The push forces required, however, on applying full pom-er v^rith the flaps down were smaller with the springy tab installed. The aj-riount of trir,i-tab deflection for trim is greater by the amount required to offset the NACA ARR Mo . L'^l20 Q effect of the springy tab at trim speed. The niinlmur,i speed at which the airplane v/ith the springy tab could be trimTied, v/hen the inaxiir.u.n trim-tab deflection is used in the landing condition (fig. 11(a)) at either center-of- gravity position and in the a-ooroach condition (fig. 11(b)) at the forward center-cf -gravity position, was rkther high, particularly in the landing condition. As shov/n in figiare 11(a), a force of 22 pounds was required for triTi in the landing condition at 100 niles per hour, so the trim forces shov/n in table II for trJ.s condition do not correspond to trir^-force changes fn.-. a trir;ir;ied condition. The data given for the airolane v;ith the original tab trirnraed at 100 miles oer hour in the landing condition were obtained ''o^j interpolation frorr. unoublished data for an airplane of the sa;';e tyoe as that of this investigation because data for the airolane vvith the original tab ^^ere not available. Gor.iparison of Springy Tab with Other Devices Providing Stick-Free Stability In a discussion of the springy tab, it ?nlght be approTDriate to comoare it v;ith other devices used to iraprovo stick-free static longitudinal stability.' One device used for this purpose is a spring in the control systen that exerts a r.ioiuent which tends to depress the elevator. Although this device, called the bungee, ".vill increase the stick-free stability/, it has disadvantages; A pull force raust be exerted by the pilot to hold the stick back while taxylng and the high push forces that may be required in high-speed flight a'ouIc result in excessive accelerations if the stick were released in an out-of-trim dive. The same disadvantages apply to a bob- weight except that it produces an additional increase of stick force v/ith an increase in nox^nal acceleration, which would prevent excessive accelerations in this ;::aneuver. The springy tab vv'ill not cause any appreciable pull force while taxylng because the dynariic pressure CiXi the tab at taxying speeds is low. in addition, the springy tab will not cause large push forces at. high speed isecause it will then be deflected to its neutral position. Another advantage of the springy tab ever the bungee or bobweight is that the stick-force characteristics may be adjusted to obtain aL.iost any desired elevator stick- force variation with soeed. This adjustirient may be 10 h.XA a:;R 1-0, L5I20 accorrpli shed by changing the aerodynamic characteriEtlcs of the tab, the spring :nonient at zero tab csf lection, aud. the variation of the momont e:':erted. by the spring with tab deflection. A force increr^'ent of almost any value can be applied at any part of the speed range of the air- plane. The variation of hinge rao.uent V/lth deflection for the initial springy-tab configuration is shown in figure l3 . The static longitudinal stability characteristics of the airplane v/ith the initial springy- tab configuration before the changes indicated on page h. .'vere made are shown in figure 19. A con.parison of figure I9 with figure 9(^i shov/s bi'ie wide variation of elevator stick-force charac- teristics obtained v/ith the sprxngy tab for the cha.n^e in hinge- moment oetween that shov/n in figure iG anc that shown in figure 6. It should be n.'^teG that a large increase in stick-free stability in the low-speed range, where adverse effects of power are usually grec^test, may be obtained without -^reatly affecting the stabilit-y ut higher speeds by the use of a variation of soring i.iornent with tab deflection in which the soring nioraent that tends to nove the tab upward increases for the larger up-tab deflections . Be call se a springy tab vnay be used to adjust the control-force variation with sooed. within wide li-aits, it can be usee on the rudder or ailerons to eliminate undesirable trim-force changes with speed. CONCLUSIOITS ■^ro'i flight tests to deterri'.ine the effect of a spring-loaded cab on the longitudinal stability charac- teristics of a low-wing scout bojr.ber, the following con- clusions were reached; 1. Compared with the original tab installation the springy tab increased the stick-free stability in all flight conditions as ir.anifested by the larger negative slopes of the curves of elevator stick force against air- speed. In the cll;nbing condition at a rearward ctntci"- of -gravity position - a condition in which the airplane with the original tab shovi/ed stick-free instability throughout the speed range - the airolane with the tab e::hibited satisfactory stic'c-f orce variati m wit}:i speed. NAG A ARR No. L5l20 11 2. The pilots did no'i consider the characteristics of the airplane to be satisfactory for any flight condi- tion in v/hi ch it was unstable with stick fixed; although they believed thc.t the control characteriscics were improved by the springy tab. J. The springy tab reduced the danger of inadvertent stalling because of the definite pull I'orce required to stall the airplane with pov;er on. ii. . The springy tab may be used to provide almost any desired variation cf elevator stick force with speed by adjusting the tab hinge -iiuraent characteristics and the variation of spring mon.ent v/ith tab deflection. 5. The springy tab tended to reach maximum deflection at a speed near the stalling speed for all flight condi- tions despite the variation of stalling speed with flight condition. 6. The springy tab reduced the effect of center-of- gravity position on stick-free static stability. 7. The stick-fixed static longitudinal stabilit;;/' v/as slightly decreased by the action of the springy tab. 8. The springy tab had little effect on the elevator stick forces in accelerated flight. 9. Pull forces required to naintaln trim on closing the tlirottle with flaps up were considerably larger with the springy tab installed than with the original configu- ration. The push forces required, however, on applying full power with flaps dcwn were smaller with the springy tab installed. 10. The springy tab would provide stick-free static stability without requiring a pull force to hold the stick back ^vhil? taxying, as v^oul"^ oe ::'equired by the bungee and rhe bobweight. 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P. D, 1^ a. a a a a o o 3 iH rH <-l H O O O o o o O O H »H o o o u ~ o u O n o c « » a » c a c c c o P. B o » E a a a « aaa> » » TJ d k TJ t4 s ^^^sss^.^l O ,H|rM ggpca o • g- CO c ~* u c c c c C •H U E C c ^ o •D a & O. i » » » » TD OJ S » > a a aa 4J 3* ==ssss s 3°" s s O t3 P DO o o © -H 3 3 C T) n n -H O n *i <;-, ^H «-. tM m -p OJ « U %-. V © ►< ." O O O o ;< +^ o o U 4 o. eov, a 60S-, of a CO fc. t* t* UCO r^ X t. rH COCDCOCO U C T3 O hTv © ® © 03 rr\ f>J ■o o © rvj tC\tr\rr\K\ © 00 « '-' ^° k fe s » r-1 • O » » a © O C O S.Z8.S. O CO o o S ^ wnr\ V( ^lA a. CU w4 (• r t« *^ -— *» 4-1 s o C « « o s o E rH O o © •o TD o © •a a o t^t^t^t^ © Qh ^ a ft-, t-t m > c x; T3 0) W 3 l-i 0) £1 E o XI o CO bo C I o x: o 0) t3 cy3 I bo NACA ARR No. L5I20 Fig. 3 to Fig. 3 NACA ARR No. L5I20 Q> X> Q) -f-J (1) -IP ^Th u. c- <: CS^ c: »>- o JO V ■+-1 n i5 (b M \J > K « 2 !5 o l< -< P < *^ Z UJ o t: o o ■H 00 m (D r do a f-i h P. CD (U «H o B a u bO bO NACA ARR No. L5I20 Fig. 4 e CO •H C cd o > > bD 0) C -H — ( 0) U a, t3 a u > o o CO cd E CO ■H c cd x: • +J E bD ■H (d (M 1 Li >> o bo. bO •H u a CD «-l^ /6 _o- 8 4 NATIONAL ADVISORY COMMITTEE FOft AERONAUTICS n o 4 8/2^ Springy-tab angle, deg Up Figure 6.- Variation of springy-tab hinge moment with springy -tab angle (as measured on the ground). Fig. 7 NACA ARR No. L5I20 3a p. 0) T3 i-H tiD cO M O > r-i 20 lO o JO c o ^?o /l / / ) / / / / / / / / / / / / / NATIONAL ADVISORY COMMITTEE FOfi AERONAUTICS ) 8 Forward o stick position, in. 8 /2 Back Figure 7.- Variation of elevator angle, n.easured from the stabilizer, with stick position for the test airplane. NACA ARR No. L5I20 Fig. 8 O a u >- I- 52 o > ^ -J 9 < z o ho (U T3 0) r-l bO C o ■p > (L) r— t w CD ^ +J • (i> ^--^ > T) O C fc: d o O M -P fciD Tl 0) CD x: M +j •H d C cr o (D u Ti a> (U M o 3 ^^ w O cti tM M' M >. O i-H +J & a o > rH (t» CO w M O 1 4J • CTl 150 > 0) 0) iH ^( 0) :=! bD Fig. 9a NACA ARR No. L5I20 ho C oJ (-• O > Max. up deflection, 28 -B-S =© u e.g. position Elevator (percent M.A.C.)trim tab 32.0 26. S 2.9°, nose up 6.1 , nose up Spot Cont inuous runs runs Gf □ nf Max. down deflection, 1^ bo T3 c od XI (fl +j I >i M C ■H a en Correct service indicated airspeed, mph (a) Airplane with springy tab installed on elevator. Figure 9.- Static longitudinal stability characteristics in the climbing condition. NACA ARR No. L5I20 Fig. 9b w e.g. position Elevator (percent M.A.C.) trim tab Spot Continuous runs runs 31.^ l.'+O'"'^^® down o Q^ 2U.5 2.U. ,nose up id nr D. bO T3 bO C tC ^^ o m > I— I w i-V^ 10 *.. G-B— 9 ■B — B — { -B 5 — ' —a ijr^ a«r^ © -© e c ■i u 10 ^ NATIONAL ADVISORY COMMITTEE FM AERONAUTICS 20 / — Max. down deflection, 2i 80 /20 I60 200 240 EBO 3a0 Correct service indicated airspeed, mph (b) A'irplane with original tab on elevator locked. Figure 9.- Concluded. Fig. 10a NACA ARR No. L5I20 5 ^o <0 o u o 0) T3 bO C Id o n) > D i-H 401- e.g. position Elevator (percent M.A.C?) trim tab o 31.7 5.7o,nose up 2b.' 9.2 ,nose up Spot Continuous runs runs O □ d 10 o "^ag Ua X. up den ectic n. ■^& ^ S — a— =e— G V — B — c -G -G ^ 1 G> Q ■o 5- 20 bo c a! £1 m <-> I >. bo G •H a /o o / *. ^j ^^ 'w^ ^ \ ^ \ NATIONAL ADVISORY COMMITTEE FM AERONAUTICS Qs S ^.. ^^ "^ f=^= =a© -G 80 120 160 ZOO 2m 280 Correct service indicated airspeed, mph (a) Airplane with springy tab installed on elevator. Figure 10.- Static longitudinal stability characteristics in the gliding condition. NACA ARR No. L5I20 Fig. 10b 0) o ^( o 0) i-H W e.g. position Elevator (percent M.A.C.) trim tab Spot Continuous runs runs 30.9 0.9Q,nose up o 5.0 ,nose up □ 120 leO 2D0 240 2^0 Correct service indicated airspeed, mph 3Z0 (b) Airplane with original tab on elevator locked. Figure 10.- Concluded. NACA ARR No. L5I20 e.g. position Elevator (percent M.A.C.) trim tab ,0 bv. \ N. \: ^. Spot Continuous runs runs ^ 15.0^, nose 15.2 ,nose 12.9° nose 15.0 ,nose up up up up O a O eflection, 2S — y — Max. down deflection, 15 A A- -A— 4 -Cr- til) (D o, •a l=> c ai a) += I >» bo c; •f~i hi D. to '^n W B^ ^ p^ ^. /o i ) n ^ \ % ^^ ^. s NATIONAL ADVISORY COMMITTEE F0« AERONAUTICS 60 100 140 60 100 140 Correct service indicated airspeed, mph (a) Landing condition; springy tab installed on elevator. (b) Approach condition; springy tab installed on elevator. Figure 11.- Static longitudinal characteristics. NACA ARR No. L5I20 Fig. llc,d w 73 M O Id > 4) rH w :§• IC- a GO e.g. position Elevator (percent U.A.C.) trim tab Spot Continuous runs runs 26.2 25.7 15.0 ,nose up □ ef g.7°, nose up A A" Max. up deflection, 2g v- NATIONAL ADVISORY COMMITTEE FOt AERONAUTICS ^. ^3fe4 A r, —A i /oo w 60 100 140 Correct service indicated airspeed, mph (c) Landing condition; original tab on elevator locked. (d) Approach condition; original tab on elevator locked. Figure 11.- Concluded- Fig. 12a NACA ARR No. L5I20 ^ (U o o u o > 0) bo 01 •a c o 0) > w 2a e.g. position Elevator (percent M.A.C.) trim tab 30. S 9.0°, nose up 26.5 12.5 ,nose up Spot Cont inuous runs runs G cr □ P §- o o o /o Max. up ueixeuu. "Max. down deflection, 15° NATIONAL ADVISORY COMMITTEE FM AERONAUTICS /40 Correct service indicated airspeed, rnph (a) Airplane with springy tab installed on elevator. Figure 12 . - static longitudinal stability characteristics in the wave-off condition. NACA ARR No. L5I20 Fig. 12b 20, (U 1— 1 o :3 (H p- o CO ^1 o 43 +J CO tti 3 s P^. 20- g q e.g. position Elevator Spot Continuous (percent M.A.C.)trim tab runs runs 25.6 k.b ,nose up h G^ bD § O +^ ni > a; 10 s o o / Max. up deflection, 2S &-«- -a — B NATrONAL ADVISORY COMMITTEE FOR AERONAUTICS Max. down deflection, 15 _l I I I I 10 40 60 120 leo Correct service indicated airspeed, mph (b) Airplane with original tab on elevator locked. Figure 12.- Concluded. Fig. 13 NACA ARR No. L5I20 (a) Climbing condition e.g. position Elevator (percent M,A.C.")trim tab 32.0 -^ "° 31.7 31-'^ -• o 30.9 0.9 , nose up Spot Continuous runs runs 2. 9°, nose up © ex. 5,7° nose up E B^ l,k ., nose down <^ ^ A A } } Elevator with springy tab installed Elevator with original tab locked 0) o o o (0 o +3 > i-H 320 Correct service indicated airspeed, mph Figure I3.- Comparison of stick-free static longitudinal stability characteristics of airplane with springy tab installed and of airplane with original tab locked. NACA ARR No. L5I20 Fig. 14a %\ SlOr Static tab angles _y — ' — - — — cd (u (u qci iO on 1 1 O V p. EVi --•CO /80 /40 NATIONAL ADVISORY COMMITTEE FM AEDONtUTICS _ _- V, rim i^ le 24 Time, sec 32 40 48 56 (a) Climbing condition; center of gravity at JO.J percent mean aerodynamic chord; springy tab installed on elevator. Figure l'*.- Time history of motion following stick release at speed slightly above trim. Fig. 14b NACA ARR No. L5I20 O C j.iziz^ cor.; :ti-r.; cer.'er o; gravity 31; JO. 2 pToer.t Crar. aer:xlyna=ir crori; scringy tai ir.s"alle3 or. elevator. "anclucied. NACA ARR No. L5I20 Fig. 15 o o o o > CO IH o ■)-> > r-f w 30.0 0.2°, nose down O 25.7 1.7°, nose up □ NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Normal acceleration, g Figure 16.- Variation of elevator stick force. with normal acceleration in turns at 196 Tiles per hour. Airplane with original tao on elevator locked. NACA ARR No. L5I20 Fig. 17a zn \ 10 \ \ V — n /c \ /^ n V / ^ - v k / in \ / 20 20l K ~\, / i \ ^/\ V ^ 4-> a> . •H u CO a l_w 24 .k . / ao / / / / le /' 12 / / / / 6 / / / 4 < NATIONAL ADVISORY COHHITTEE FOR AERONAUTICS n o 8 12 16 20 Springy-tab angle, deg Up Figure IS.- Variation of springy-tab hinge moment with springy-tab angle as measured on the ground for the initial springy-tab configuration. NACA ARR No. L5I20 Fig. 19 o u o M o -H (0 M O Id > rH 2a ■3 1 Reported trim o^ i^ 7 % A o » •a Max. u?) deflection, 2g •a bo a I CO Max. down deflection, 15 e.g. position Elevator Spot Continuous (percent M.A.C.)trim tab rune rxins 2.3 .nose up O NATIONAL ADVISORY COMMITTEE FM AEMNAUTICS -O O^ 200 240 o- 280 Correct service indicated airspeed, mph Figure 19.- Static longitudinal stability characteristics in the climbing condition with the initial springy-tab configuration. UNIVERSITY OF FLORIOA 3 1262 08103 3101 UNIVERSITY OF FLORIDA DOCUMENTS DEPARTMENT 120 MARSTON SCIENCE UBRARY P.O. BOX 11 7011 GAINESVILLE. FL 32611-7011 USA