1、4 b-.* “z . .4 -” ;.: . :2. . - llllllllllllllllllllllllllllllllllllllllllllllllllllllllll3 1176 00083 1868 ., .,.+“.*.,. 4 .,. *. a. . : .“ - ,- -UO* 555By W. H. I!cAvc)yLangley Hermrial Aeronautical Laboratory-.- -Washington :i?e”bruary1936”.Provided by IHSNot for ResaleNo reproduction or networki
2、ng permitted without license from IHS-,-,-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS-TECHI(jAL j$joE;().555 PILOTING TECHNIQUE IOR REUOVERY i?ROM SPINS3y , H, icikVOySUMMARYSystematic flight investigations of the spinningcharacteristics of various airplanes over a period of sev-eral years have give
3、n the pilots engaged in the testing avaried and. extensive experience, From this experiencecertain general rules of procedure have been formulated,particularly for the sequence of operation of the controlsin recovery from spins, and are recommended to the atten-tion of all pilots.INT!RODUCTIONYsOver
4、 a period. of several years the National AdvisoryCommittee for Aeronautics has done a great deal of flighttesting for the purpose of systematically studying thespinning characteristics of various airplanes. Ior exam-ple, over 900 spin tests were made with one airplane whosespinning characteristics w
5、ere vicio72s at times, dependingon the effect of modifications to the tail and to the loaddistribution. From the varied and extensive experiencegained in these flight tests, the pilots en-gaged in thetesting have learned a number of general rules, pertainingparticularly to the routine of control man
6、ipulation forrecovery fron prolonged spins. It is believed that thesegeneral rules will le of interest and value to other pi-lots. Although no method of control manipulation for re-covery can be claimed to be infalliole, it is believedthat the procedure recommended herein should be generallyadopted.
7、PRECAUTIOITS DURING SPIN. A rule of great importance for student pilots or for,4“ any pilot who is not entirely familiar with all the spintraits of a particular airplane, is that during a spin andJ particularly during the last 3 or 4 turns of a prolongedProvided by IHSNot for ResaleNo reproduction o
8、r networking permitted without license from IHS-,-,-2 N,A C.A.”Technical Note No. 555”spin before recovery is attempted. the ailerons should beneutral and the elevator and rudder controls should beheld, all the wa with the S.pine - . -There are two important reasons for the foregoingrecommendation.
9、First, ithas been observed that a muchsnappier” and more forceful reaction on the part of theairplane toward recovery is obtained when the controls aremoved from one extreme to the other Olmiously, havingthe controls already full with the spin gives assurancethat the full range of control deflection
10、 is available forrecoverya Second,” it has been observed” that the above-described application of controls produc”es the steadiestand most uniforti spin cbnditiont!(!hesteady spin is desirable since it has frequentlybeeii definitely demonstrated that an unsteady or oscillat-i“figspin greatly aggrava
11、tes any confused mental conditionthat may be present during a spi maneuver, The likeli-hood of mental confusion and its importance cannot be over-emphasized. It is only necessary to mention that on sev-eral occasions pilots with extensive experience in spins,including the pilots engaged in the N.A.C
12、,A. spinning in-vestigation, have been known to move the controls to posi-tions opposite to those intended because of their mentalconfusion or excited condition-RECOMMENDED USE 01$ CONTROLS FOR SPIN RECOVERYThe recommended operation of the controls for recov-ery from a spin, which presupposes that t
13、he ailerons areheld in neutral throughout the recovery, is as follows:1. Briskly move the rudder to a pos5tion fullagainst the spin.2. After the lapse of appreciable time, say after atlest one-half additional turn has been made, briskly movethe elevator to approximately thq, full down position.3. Ho
14、ld these positions of the controls until recovery is effected-There are a number of “reasong why the rudder movementshould precede” the elevator movement. The effect of thereversed rudder isto check the” rate of rotation and cause.“%Provided by IHSNot for ResaleNo reproduction or networking permitte
15、d without license from IHS-,-,-N.A,C,A. Technical Note, No. .555 3the nose of the airplane to go down. The blanketing ofthe rudder by the elevator is generally less, and hence“the effectiveness of the rudder greater, when the elevatoris up. While the rate of rotation is being checked by therudder, t
16、he elevator becomes increasingly effective in as-sisting recovery. An opposite ,sequence .of operation, thatf.s;one in which the elevator movement precedes the rudder“movement, is decidedly objectionable, because the usual ef-fect of putting the stick forward while the rudder is heldwith the spin is
17、 an increase in the rate of rotation.,.,. Slow and cautious movement of the controls during re-covery is to be avoided. In certain cases it hasheenfound that, witih a SIOW and cautious reversal of the rud-der and elevator, spinning will continue indefinitely;whereas brisk operation of these controls
18、 would have ef-fected recovery. “, ,. EHERGENCY MEASURES,. , .,., .,. .,The comparative effectiveness of rudder and elevator1 control during a spin recovery will be foundto vary to ahigh degree.It.is quite possible for a condition to ex-ist wherein the elevator will prove to be a more positive cotit
19、rol than the rudder. Even in this event, however, achange in the sequence of control movement is unnecessaryand is not recommended4. , .,The advfsa%ility of;using ailerons as an.additionalmeans of recov.ery.”is debatable. It is,suggested, however,that the use of ailerons relative to the individual a
20、ir-plane be studied, inasmuch as on some airplanes they aidappreciably in recovery, provide,d:.that the proper displace-ment is used. The proper displacemefit may %e eitheragainst or with the spin, depending on the particular air-plane. ,.,It is not uncommon fors ad-sp,inning airplane”to .make at le
21、ast 5 turns before the recovery control appears :.to give any satisfactory results. ,1or such airplanesthere is always a strong temptation on the part of a pi-lot to try some other ,control manipulation when the one originally applied pr:oduces no apparent effect in a shorttime . It is extremely imp
22、ortant-that such impatience beavoided. The time element itself is likely to be greatlyoverestimated because of mental confusion. Experience hasshown that it is advisable to judge the lapse of time lY.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4
23、H.A. C,A. Te,chnica I Note Ho. 555,. ,the number ,of turns made,. In the event., then, of a vi-cious spin, a rule,ofgreat importance is to hold the con-trols applieil foi ibcoi.ery.for. at least 5 tuins before at-tempting any-,other measure to ,promote,recovery. ,.Use of the thr,ottlein an attemp”t
24、to recover from ahad spin, alt-nough effective, at, times, ii very poor prac-tice and generally should be constd.ered a-sa measure to betried .only as a.last. resort; In,a.prolonged spin consid-erable. difficulty, usually is experienced in keeping the,engifi-eturning over at idling speeds, a frequen
25、t resultbeing a dead stick before the termination of the spin. If,“power is used to attempt a recovery, i.t is Usually attend-ed.by a violent vibration originating” in the propellerblades, , .In recent years several instances haye been reportedwherein, as an emergency measure, pilots have stood up i
26、ntheir seats with tile result.that the air-plane recoveredfrom the spin. There appe”ars to be no reason why the air-plane recovers under these conditions unless it is because$he controls are free. In order to obtain informationconcer,n$ag this point, a number o,f tests of a single-seat,pursuit-type
27、airplane were, carried out in which the con=trols were released by the pilot after a steady spin hadbeen attained. The pilot remained in his normal positionduring these spins, noting the movement of the controlsand observing the spin, In A number of cases the airplanerecovered with the controls free
28、, although the recoverieswith this airplane were not particularly satisfactory evenwhen the controls were manipulated in the most effectivemannert GENERAL pRECAUTIONSIt is desired to stress the importance of obtaining areasonably safe altitude before a spin is started and eventhen proceeding cautiou
29、sly. Overestimation of oners abil-ity, unfamiliarity with an airplanes spinning and recoverycharacteristics, “and the ha%it of starting spins at low al-titudes make a vicious combination that has caused manyfatal accidents. If tests of an airplane whose spinningcharacteristics are doubtful are being
30、 conducted., it isrecommended that an altitude Qf at least 10,000 feet-beobtained before starting a“spin.f,W*.x.:.,*8Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N.A.C:A. Technical Note o 555 54.m-.-“The first few turns of a spin constitute a tran
31、sitionperiod from straight flight to the final st,eady spin, dur-ing -which recovery is likely to grow progressively moredifficult. In spin tests of a strange airplane it is ad-visa%le to make use o.fthis period for trials of the easeof recovery at various stages of the spin. In the firsttrial, for
32、example, attempt the recovery after 1/4 turnand in succeeding trials recover after, say, 1/2, 3/4, 1,1-1/2, 2, 3, etc. turns. It is quite possible that ifthis procedure is followed dangerous characteristics willbe detected before serious trouble is encounteredJudgment as to whether the final spin wi
33、ll prove tobe uncontrollable should not be based solely on the atti-tude of the airplane. Uncontrollable spins are not neces-sarily flat spins, The effecti.ven.ess of the controls af-ter the correct displacement has been made is probablygenerally less for flat spins than steep ones; but theforce req
34、uired to move tne controls may be a vital factorand, as explained in the following paragraphs, controlforces are dependent on various items that are not relatedto the spinning attitude.The magnitude of the control forces required for theproper movement of control surfaces during spin recover-ies wil
35、l te found to vary over a wide range. Althoughseveral conditions regulate the forces required for dis-placement of the controls, the most, important factors ap-pear to be the size and eight of the airplane and thearea of the control surfaces. In certain cases, forceshave been experienced which requi
36、ro tho maximum physicaleffort of the pilot to force the controls to the desiredpositions. It is recommended that the pilot carefullycheck his position in the cockpit to assure himself thathe can apply maximum force on the controls lecause theposition assumed. by the pilot in holding full rudder whil
37、ethe stick is %eing pushed forward is, at best, awkward.Discrepancies in rigging will, as a general rue, af-fect the spinning characteristics to a greater or lesserdegree according to the particular type of airplane in-volved. In general, ailairplane will spin differently ina right than in.a left sp
38、in, owing to the asymmetry in therigging provided to overcome propeller torque and slip-stream effects for normal flight. Thus it is possiblethat a type of airplane that has een found to be satis-factory in spins may lecome unsatisfactory if improperlyrigged. It is also possible that an airplane ma
39、have.-.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 N.A.C,A Technical: “Note .No,.-555satisfactory spirining characteristics for a spin in onedirection andun.satis”factory charaoteri.sties for a spin inthe opposite.didectiofi.,.Chailges in “w”ei
40、ghtand. center-of-gravity position arelikely to cau%e h”anges in the spinning characteristic sAlthough it Wotild I)e”verydifficult topredict the effecto.fe.definite ,cerlter-of-gravi-typosition on the epinningcharacteristics”, it is recommended, that t,he spinning ofairplanes w“tthabnormal center-of
41、-gravity positions be re-stricted Onep”aint to bear in”mi.nd is that with thecenter-of-gravity position well aft it is usually easy toattain the stall “nece”ssaryfor a spin entry; whereas, ifthe reverse .contfition of loading exists, considerale dif-ficulty in stalling the airplane iill,be experienc
42、ed andit may be necessary tause power in order to start a spin.The position of the wheels on airplanes with retract-able landing gears “is”likely to influence the spinningcharacterl.st.tcs .qnitienoticeably. Considerable data o%-tained on several types now inservice show that both thespin and recove
43、ry are adversely affected when th wheelsare down ,Bomb Iokds on the wingsusually have the effect ofmaking the spi,n recovery more “sluggish. The effect ofbombs is more evident on airplanes that normally spin withone wing tip well down, and ther-e is a possibility that abomb load on such an airplane
44、would prove adverse to re-covery. ,. .(KINCLUS1ONSIn conclusion, it seems advisable to restate briefly,for emphasis, the following general rules:1, During a spin, particularly during the last 3 or.4 turns of a prolonged spin, before recovery is attempted,the ailerons should be neutral and the elevat
45、or and ruddercontrols should be held all the way with the spin.2. When applying controls for recovery, the ruddershould be briskly moved to a position full against thespin and later, after &t least one-half additional turn ismade”, the elevator should be.briskly moved to the fullclown positiou.t.a71
46、 II.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-T N,A,C.A. Technical Note No. 555 7* 3. In the event of a vicious spin, the applied con-trols for recovery should be held for at least 5 turnsbefore attempting any other measure for promoting recov-
47、ery.4. Deliberate spins should be started at an altitudeof at least 10,OCO feet.5. When any doubt exists regarding the recoverycharacteristics of an airplane , a familiarization methodconsisting of trials of recoveries at various stages ofthe transition from straight flight to a steady spinshould be
48、 employed.Too much confidence should not be placed in these orany other rules, however, for no method of recovery can beregarded as infallible for all airplanes.Langley Memorial Aeronautical Laboratory,National Advisory Committee for Aeronautics$Langley l?ield, Vs., January 16, 1936, .*,.JF”Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
