VOR TRACKING AND VOR APPROACHES

Transcription

1 VOR TRAKING AND VOR APPROAHES Principles Enrute Trcking Since irwys usully run in stright lines between VOR sttins, nd since mny IFR pprches re bsed n VOR sttins, key skill in IFR flying is the bility t trck rdils withut gret effrt. It hs t beme send nture t yu, s yu cn devte yur ttentin simultneusly t the vrius ther tsks tht mke fr sfe cruising flight r sfe pprch. Flying utbund frm VOR is esier thn inbund trcking becuse the frther yu g frm the sttin, the mre widely seprted re the rdils. Ner the VOR the distnce frm the 4 rdil t the 41 rdil (fr exmple) my be nly few feet, but t distnce f miles it is hlf mile. Thus, if yu strt utbund frm the VOR with yur OBS set t the rdil yu wnt t trck, nd the mni needle is slightly ff center, yu hve plenty f time t try ut different heding rrectins until the needle finlly centers. But, s yu'll disver, things hve t be dne much fster flying inbund becuse s yu get clser t the VOR, the needle will mve much mre quickly wy frm the center psitin unless yu pin dwn the crb rrectin fster. In surprisingly shrt time the needle cn mve full scle nd be "pinned t the peg." T trck rdil utbund, yu first hve t intercept it. Usully degrees is gd intercept ngle, but depending upn hw fr yu re frm the rdil, yu my wnt t chse much lrger ngle r smller ne (s smll s few degrees). It's just mtter f simple mmn sense. Yu dn't wnt t spend ll dy intercepting the rdil, but then neither d yu wnt t fly right pst it nd then hve t intercept gin frm the ther side. Fig. 6-1 gives the prcedure, step by step. Suppse yu wnt t intercept nd trck utbund the rdil, nd tht yur psitin is smewht t the right, perhps n the 1 rdil, s in (1). Set up the rdil yu wnt n the OBS, nd turn t tht heding. The indictr will shw FROM, nd yu will be flying pprximtely prllel t the urse yu hve chsen. The needle will then shw yu the

2 VOR Trcking nd VOR Apprches psitin f tht rdil; in this exmple, the needle will pint t the left. Nw, s in (), turn twrd the needle by n munt yu think shuld be gd intercept ngle, sy degrees; yur heding will be 5 nd yu shuld be flying twrd the chsen rdil. Hld yur heding exctly, nd see whether the needle mves twrd the center. If there is n mvement t ll in but sends, increse yur intercept ngle, i.e., turn further left t new heding, perhps t 4. Agin wit, then gin chnge heding if necessry. Of urse, yu wn't exceed 9-degree intercept ngle, becuse tht wuld hve yu flying bck twrd the sttin. 1 Heding X z z Heding 5 Heding 4 Heding 5 Heding S) 6 Heding 5 Intercepting rid trcking utbund. Fig. 6-1 Let's suppse the needle strts t mve fter yur first heding chnge. Wtch its rte f mvement clsely. The whle pint is t intercept the rdil

3 VOR Trcking nd VOR Apprches smthly. Yu dn't wnt t versht nd then mke n brupt turn with excessive bnking t get bck n the rdil gin. S, s the needle mves twrd the center, begin yur turn twrd the heding yu'll eventully wnt, i.e., the urse f the rdil, in this cse degrees. This shuld bring yu t the situtin depicted in (), where yu re n urse, heding, with the needle centered. As sn s yu detect slight but definite mvement f the needle in either directin, mke smll heding rrectin twrd the needle. In (4), right crsswind hs evidently drifted yu t the left. Yur heding is still, but the needle shws yu tht yur chsen urse is nw t yur right. In (5) yu hve mde 1-degree rrectin twrd the needle, s yur heding is nw 9. Sn the needle will center gin. Since heding 9 wuld nw tke yu crss t the ther side f the urse, tke ut hlf f yur rrectin s sn s the needle centers. Nw, s in (6), yur heding is 5, prbbly just right t mpenste fr the crsswind, nd the needle stys centered. Reference heding. If yu d gd jb f hlding yur hedings, nd if yur DG hsn't precessed, the nly cuse f needle devitin will be wind drift. Infrmtin gined in this wy but the previling wind will be useful t yu in flying hlding ptterns, s described in the next chpter. When yu mke heding rrectins, hw lrge shuld they be? Tht depends n hw fr yu re frm the VOR; the frther wy yu re, the lrger the rrectins cn be t mpenste fr given munt f needle devitin. The needle mesures nly the ngulr distnce ff urse, nd given ngulr distnce mens greter ctul distnce, the frther yu re frm the sttin. With DME this prblem bemes very simple; just mke yur initil heding rrectins in degrees equl t yur distnce in miles frm the sttin. If yu knw r cn guess the distnce, yu cn pply the sme rule even withut DME. Otherwise, use tril nd errr. If -degree rrectin strts the needle mving bck t the center t quickly, tke ut hlf the rrectin, nd if 1 degrees is still t much, mke it five degrees. The imprtnt principle is t mke yur rrectins prmptly nd frequently. Dn't wit until the needle is nerly up ginst the peg. The initil im is t stp the needle wherever it is n the scle, i.e., t put n end t the drifting tendency. Nte the heding t which this hppens, fr this reference heding will be the heding yu'll wnt t fly finlly, fter yu're n urse gin. yur reference heding rrect little mre, t center the needle. Finlly, with the needle centered, g bck t yur reference heding t keep it there. The key t this whle exercise is yur bility t fly n bslutely nstnt heding, nd fr this yur DG is the primry ntrl instrument. The mni needle is yur mnitring instrument; it tells yu whether yur nstnt heding is rrect r nt. Dn't "chse the needle," i.e., dn't beme imptient nd mke lrger nd lrger heding chnges twrd the needle, r befre yu relize wht is hppening, the needle will swing pst the center nd yu'll be chsing it n the ther side. Yu might get wy with rugh technique flying utbund, but it will

4 VOR Trcking nd VOR Apprches never wrk flying inbund, when ever smller nd mre delicte heding chnges re needed s yu pprch the VOR. Wht's new in this exercise is tht yu hve t include the mni needle in yur scn. Very likely, yu'll be s busy t first trying t keep it centered tht yu'll ncentrte n yur heding t the detriment f ltitude. The trick is t include mre nd mre instruments in yur scn, withut neglecting ny ne. Just s yu did befre the VOR trcking prblem mplicted mtters, yu must py especil ttentin t rrecting ltitude devitins while they re smll, using prmpt but very slight yke pressure. When yu re well estblished n the rdil, flying utbund, mke stndrd-rte turn nd intercept the sme rdil inbund. IFR students hve lt f truble with the ncept f trcking rdil inbund, becuse they frget tht the urse will be the reciprcl f the rdil. Thus, trcking the rdil inbund mens flying urse f 6 degrees. The OBS must be set fr 6, nd the indictr will shw TO. In ll VOR nvigtin, the OBS setting must rrespnd pprximtely with yur heding, s shwn n the DG, whether yu re flying t the sttin (the indictr will shw TO) r frm the sttin (the indictr will shw FROM). If this rule is fllwed withut exceptin, yu will lwys mke rrectins by flying twrd the needle. The nly time this principle is nt pertive is in flying the bck urse f lclizer, where yu hve n chice but t fly with "reverse sensing," i.e., t mke rrectins wy frm the needle. Trcking inbund, yu'll ntice s yu get clser t the VOR hw much mre sensitive the needle bemes. Yur hedings will hve t be held with perfect ccurcy, nd yur heding rrectins will beme smller nd smller-1 degrees, then five degrees, then tw degrees, eventully even ne degree. Refuse t ccept needle tht's ff center. Mke tiny heding chnge, then wit just lng enugh (5-1 sends when yu're very clse t the VOR) t see if tht did the trick. If nt, mke nther tiny chnge. The im in inbund trcking is t crss the VOR with the needle bslutely centered. At the very lst mment, s yu crss the "ne f nfusin" right ver the sttin, yu'll regnize the sudden errtic swings f the needle. Dn't try t chse it. Just hld yur lst heding until the indictr flips frm TO t FROM. When yu crss VOR, the rule is TURN, TIME, TWIST, THROTTLE, TALK, in tht rder. Strt the turn t yur utbund heding lwys fly the irplne first nd, s yu d s, nte the time; then reset the OBS, if necessry, fr yur utbund urse, the rdil yu wnt t intercept. (The "thrttle" element enters the picture if yu re slwing t hlding speed r beginning descent, s yu might d n n pprch; prcticing enrute trcking will nt entil chnges f pwer setting.) When the irplne is well in hnd, reprt t AT ("tlk").

5 VOR Trcking nd VOR Apprches Prctice Find VOR (let's cll it Mystic) where yu cn sfely exercise few thusnd feet bve. Pick n ltitude (e.g., 4 ft.) nd hld it exctly. Trim the irplne nd set the pwer t mfrtble cruise setting. Nw rtte the OBS until the needle centers with the indictr shwing FROM. This tells yu wht rdil yu re n. Nw yur check pilt shuld cll ut mmnd t intercept nerby rdil. Suppse yur OBS shws 15. He might sy: "45 Juliet intercept nd trck utbund the Mystic 16 rdil." Yu cknwledge: "45 Juliet utbund the Mystic 16," nd immeditely strt turn t 16. While yu re turning, set up 16 n yur OBS. Since yu were n the 15 rdil, the 16 rdil is t yur right, nd the needle will nw pint t the right. Therefre, dn't rll ut f yur turn t 16, but rther t n intercept heding such s 17, 1, 19 r even greter, depending upn the circumstnces. Then yu fllw the interceptin prcedures lredy described. Once yu re estblished utbund, yur check pilt shuld bserve yu fr but three minutes, especilly rting yur bility t keep the needle centered nd hld ltitude t the sme time. Then he shuld unexpectedly cll ut mmnd t turn nd intercept the sme r different rdil inbund. Fr exmple: "45 Juliet turn left, intercept nd trck inbund the 14 rdil." It's ging t tke yu full minute t turn bck twrd the VOR, s strt ding it immeditely. Students re ften uncertin but exctly wht they re ging t d, nd nsequently d nthing. It's wrse t g blundering ff int the bndcks fter AT tells yu t g smewhere else thn it is t strt mplying prmptly even if yu hven't gt it ll wrked ut in yur hed. S in this cse strt the stndrd-rte left turn s sn s yu cknwledge. Als during the turn remember t reset yur OBS t the reciprcl f the rdil yu wnt t trck inbund, in this cse t. By the time yur heding is ming rund twrd, yur needle will be giving yu gd guidnce fr the intercept. Nw yu ntinue ll the wy t the VOR, pretending, if yu like, tht this is VOR pprch, with the VOR right n the field. If yur needle isn't centered s yu crss the VOR, yur chnce f mpleting the pprch sfely is very pr. Befre yu rech the VOR, yur check pilt shuld cll ut new rdil t trck utbund. Then s yu crss the VOR, yu strt yur turn, nte the time, reset the OBS, nd reprt: "45 Juliet t Mystic, ne-three, 4, turning t 1" (r whtever; "ne three" here is the time, in minutes pst the hur, when yu crssed the VOR).

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