REG NACA-TN-550-1936 Limitations of the pilot in applying forces to airplane controls.pdf

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1、TECHNICAL NOTES NATIONAL ADVISORY COXMITTEE FOa AERONAUTICS No. ,550 LIYITATIONS OF THE PILOT IN APPLYING FORCES TO AIRPLANE CONTROLS By K. N. Gough and A. P. Beard Langley Memorial Aeronautical Laboratory Washington January 1936 Provided by IHSNot for ResaleNo reproduction or networking permitted w

2、ithout license from IHS-,-,-2 . : NXC.h. TechnicalNbt-o 1%. 550 . , The maximum aflefonforces measured were of the or- der of 90 pounds, maximum elevator 200 pounds, and maxi- mum rudder, 450 pounds. The average-forces applied with the controls in the neutral position for the varfous cock- pit attit

3、udes were of the order of 35, 95, and 400 pounds, respectively, for the-allorons, elevators, and rudder. INTRODUCTION The forces that a pilot might exert on the controls of an afrplane are of interest in connection vith the de- sign of control surfaces and of operating mechanisms, and also in connec

4、tion with studies of controllability and . maneuverabflfty. The approximate physical lfmitations of, the pilot and the magnitude of the forces he can exertas affected by the.positions of the controls relative to his seat with the airplane invarfous attitudes should be known. Pilots are usually,gble

5、to describe the forces required to operate the controls only in such gener.al I terns as “heavyf or “light.“ Thqmsaning of such term.8 is dependent asvarious factors, fqr example, whether the force is a pull or a push, is lateral or longitudinal, and is applied wpith the hands or the feet. . Very ii

6、ttle qualitative information exist8 regarding the relative magnitude of the forces which pilots actual- ly apply or which they regard as satisfactory. The tests reported in reference 1 were concerned witha study of the time required to. apply stick forces of various magni- tudes. In the present inve

7、stigation measur.ements were mado of the maximum forces that could be applied and.,maintainsd for several second,8 on the stick and rudder pedals as nor- mally used for operating the ailerons, the elevators, and the rudder. The influence of the location of control- stick levers, or pedals, relative

8、to the pilot18 seat and of the attitude of the airplane in space was studied. Measufements were also made to determine. the accuracy with which applied forces could be estimated. A cockpit model that could be rotated to any de the longitudinal pull on the stick increases with increasing distance of

9、the stick from the seat and is greater than the push except in rearmost po- sitions; for the range of.positions tested there is a slight increase in ths.force that can be applied as the height of the stick above the seat is increased; there is a pronounced peak in the-partition of rudder force with

10、distance of the rudder pedals frdm the seat: when the pT- lot i6 securely fastened to the seat, the altitude has little effect on the forces that he can apply to the con- trols: -Positions of comfort for the pilot are not neces- sarily ones in which he can apply the most force to the contxols; estim

11、ation of control force8 is most accurate for intermediate forces. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N.A.C.A. Technical Note No. 550 3 simulated, namely, airplane banked to the right 90, afr- plane banked to the left 90, airplane nosed u

12、p 90, air- plane nosed doprn 90, and -airplane -$nverted. The condi- tions under.whfch the. tests si it provides an auxiliary hand grip. The deflec- tion of the beam caused by the application of force is Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-

13、,-4 N.A.C.A. Technical Xote No. 550 transmitted to the strain gage, which has been calibrated for both positive and negative deflection. Two beams, one of 100 and the other of 300 pounds capacity, are used. The loo-pound beam was used to obtain higher accuracy fn measuring small forces. Aileron forc

14、es are measured by rotating the control-force fndicator through 90 from fts position for .mea.sur.ng. elevator .fo.rcle_s_,:_ _. The rudder bar is a piece of oak reinforced with steel covering; it has a straight frontside and fixed pedals mounted 20 inchesapart. Xumdd.zty force6 are7measY urad by.a

15、spring balance of 500 pounds ,capacity, gradu- ated in 5-pound intervals-,.-and fi.tted with a maximum- force indicator. One end of the balance is secured to the fixed structure and- the other to the right tip of the rudder bar 4 inches outboard of the point of application of- the force. Measurement

16、s made at this point are cor- rectcd forthis offset and represent actual effective force applied to the pedals. No variation in the distance between right and left rudder pedals is provided because it is believed that, except forcomfort, there mould be little effect on the rudder force which could b

17、e applied. Holes are provided along the rudder-bar mount to allow fore-and-aft variation of location. A large turnbuckle connected to the spring balance keeps the rudder bar nor- mal to the longitudinalaxis when the rudder posftion fs varied. Three safety belts corn-parable with the most bulky acrob

18、atic harness likely to be used secured the pilot in the seat. These belts consisted of the usual thigh belt; a.chest belt just beneath the armpits; and an acrobatic shoulder harness of four straps, two anchore.d to the back of the seat and passing over the pilots shoulders, and two anchored to the s

19、ides of the seat-near the front, all four meeting at a point near the lower part of the pi- lots chest where they were secured by a quick-release pin. These belts, particularly the chest strap, restrict- ed the reach of.ths pilot but tended to standardize the results. The subdects used in these test

20、s wore the Commfttees two test pilots. Their principal physical dimension.8 are given in table II. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ET.8;C.A. Technical ,l?ote Jo 550 5 METHODS L . The investigation was divided into four parts. The firs

21、t part concerned the measurement of maximum aileron and elevator forces that the pilots could apply with a normal-length stick in various lochtions covering practi- cally the entire horizontal plane with the cockpit in a level attitude. Similar measurements were made to deter- mine the variation of

22、maximum stick force with height of stick relative to the seat. A stick height such that the center of the hand grip was 8 inches above the seat was chosen from experience by the pilots as a normal-length stick; 6 inches more and 6 inches less than normal length were used as the variations. For these

23、 measurements, as. well as for those of arts 2 and 4, the rudder bar was located at a station chosen by the pilot as being the most comfortable for a footrest; however, every precau- tion was taken to insure that no assistance was received from it, and it was believed not to have influenced the resu

24、lts because of the firm anchorage of the pilots body to the seat. In the second part, measurements were maa8 in a sim- ilar manner with the stick at the chosen normal height and itk the cockpit model in the following attitudes; level, nosed downward 90, nosed upward 90, rolled 90b to the right, roll

25、ed 90 to the left, and inverted, The first part of the measurements indicated that investiga- tion for more than one stick height was not warranted; also that the lateral range of stick location could be reduced to 16 inches without sacrificing completeness. For measurements made in attitudes other

26、than normal the pilot was not required to remain in strained positions for periods longer than 2 or 3 minutes. The third part of the measurements was made to de- termine the effect of seat height, horizontal distance of the rudder bar from the seat, and attitude of the cockpit on the maximum horizon

27、tal or effective force that could be applied to the rudder. Measurements of rudder force with the rudder pedal located atvarious points along the longitudinal axis and with the seat.at the lower. extreme of its travel were made in each of the six attitudes . tested in the secon-d part. Similar measu

28、rements. yere made in the normal attitude with the seat full up. For each individual measurement the linkage containing the . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 2T.A.C.A. T.echnical Note No. 550 ., . . . spring scale was adjusted so.$h

29、af When the spring was 8x- tended the-rudder pedal was approximat.ely normal to the longitudinal axis of the cockpft. Exh;erience gained in previous flight tests Suggested the desirability of determining the .accuracy with which pilots can est+nata Stick forces normally encountered. Although interes

30、t in,.such infor.mation is limit-ed chiefly to test pil0t.S. .sUc,h measurements of-.Limited scope were mad8 and they constitute the fourthpart of-the measure- ments. Thelocatioh of tho normal-length stick was varied along the piane of symmetry and attqmptg Were made to ap- ply forces of. predet,erm

31、ined magnitude. An observer noted the forces actually agplied. The subject under test was not allowed to know the agreement of 8StimatQS until the complati,on of the measurements. Two attitudes only, nor- mal and facing downward, wore. considered; the face-down- ward.aftitude is of vertical.dives. i

32、nterest chiefly in connection with , ACCURBCY bioasurements of elevator forceware believed to be accurate to L3 poundsi aileron measurements, in that a spring heam.of one-tiiird t$e cnpqty of!-tg 58 useg for elavator measurements vas used pith the aamo strain diai, are accurate to +l pound, Rudder f

33、orces are estimated to be accurate to 230 pounds even though the.scale of t.he spring balance used was graduated in 5-pound intervals The accuracy is probably no greater because the point of application of the force may easily have varied as much as l/4 inch due to the necessity of rigidlysecuring t

34、he rudder pedal to the rud.der.bar. Perhaps the.factorwarrantinp most consideration in connection with-accuracy is that of obtaining tho same degr,ec of exertfdn from a subject under the several con- ditions of test. This factor is; of course, dependent on the subjects ability to duplicatethe effort

35、 expended. The agreement of.the tr8n.dS shown by each of the two pi- lots indicates that such aconsidcration had not caused errOneOUS COnClUSiOnS to be reached in the88 tests. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. N.A.C,A. Technical Rote

36、No. 550 7 RDSULTS AND DISCUSSION . - .: ._- _, , : . . ._,. . . r . .; . . . . . . ,.- . . . . . 1 ._ : , . .- ,-The res-itlfs dfmessurements to det$rmine:.the maximum stick forctis,fhat ,laterill and.longitudinal position of the. stick:.dithfn the cocwif; and attitude relative to the gravitational

37、force, are presented in.figures 3 to 13, inclusive. Figures 3 to 9 are constructed in isometric form because it is-believed-that this method allowss rig- id interpretation of the variation ofthe -relative magni- tudesof the: Bti lateral location is measured along lines upward to the left; elevator f

38、orces are plot- ted on vertical lines; aileron forces-originating at the same point are plotted along lines.fepresenting :lateral displacement; solid,envefope lines.connect. extremities of muI.1 forces for bothelevator and aileron; dashed lines - join push forces; vectors of all aileron forcss are s

39、hown; vectors of both the elevator push and pull forces at the same point are shocm. Yith.one exception, the,longitudi- nal ran.ge.ofstick location covers 18 inches and the.lat- eralrnnge covers 16 inches (8 incheson either side of the plane of symnotry). The one exception (fig. 4) cover.s a lateral

40、-range of 24 inches in 4-inch steps. As previ- ously stated, it was decided that such detail was not war- ranted in subsequent measurements. . Figure 3 shows the effect of the height of the grip above the seat on the magnitude of the force.that can be applied to the control stick Et will be noticed

41、that the forces applied with the center of the hand grip 14 inches abovethe seat throughout the range of stick loca- tion investigated are generally greater than those applied with the normal 8-inch grip position, which are in turn groatcr than those with the grip 2. inches above the seat. Figures 3

42、 and 4 both show the effect of lateral and longi- tudinal positions of the stick (corresponding to positions when deflected) on the-force that can be ,applied to it. with the cockpit mode1in.a level attitude. It .wilL be seen that elevator pull forces are greater than push forces except in the rearm

43、ost positions, that pull forces inorease with distance as long as the stick can be reached, and that push increases with distance to the point where Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 N.A.C.A. Technical Mote Bo. 550 l - the arm is stra

44、ight, after which it decreases, Unfortu- nately, pull on the stick is a mfnimun at the rearmost position, the positfon used to get the tail of an air- plane down in a landing. During the tes-ts it was noted that comfortable positions of the pilots arm and hand wera not associated with the positio.ns

45、 in whfch maximum force could Be:appliad. Lateral forces that can bo.applied.to the stick (corresponding to aileron movements) are a maximum for the rsarmost positions ,anddecre.ase yith distance and with lateral deflection of.the stick. Push forces (cor- responding to up loft ,ailcron for a right-h

46、andodpilot) are greater than pull for,ces at corresponding positions of tho stick. The remainder of the measurements of maxfmum stick forces weremade to deter-mi.ne the,effect of cockpit model attitude. Results of.measurements made with the cockpi.t model rolled 90.to the right areshov-n in figure 5

47、. It will be seen thatthe.variatiQn .of forces is generally the same as with,:the cockpit modal-in a level attitude, except-that forsdSs ahich:can be exerted to the left of neutral areless and.thos for pi- lot B at 35 inches. With the seat raised 6 inches verti- cally, pilot A pushed a maximum of 29

48、0 pounds at 32 inches and pilot B pushed a maximum of 330 pounds at 33 inches. It is thus seen t-hat a vertical seat adjustment of 6 inches was responsihle for a difference in maximum effec- tive force of 100 to 140 pounds and caused the maximum to occur from 2 to 4 inches nearer the seat with the s

49、eat UP. The lower half of figure 14 shows the effect of cock- pit-model attitude on the maximum force that can be ap, plied. A comparison of the results obtained with the two pilots indicates that attitude has little effect on oi- ther the fore-and-aft location or the magnitude of the maximum force. It is interesting to note