Lesson 01: ADF: Tracking inbound & outbound QDR interception at station passage teardrop procedure turn

Note: Before beginning with the radionavigation flight instruction, study or review PILOT NOTES X and XI, respectively covering the basic principles of radio and the navigation aids. Answer the associated questionaries in writing. 



1°- Jeppesen charts

JEPPESEN/SANDERSON INC., in short "Jeppesen", is an American private venture publishing the so-called "Jeppesen Manual" which is, in fact, the bible for later IFR operations. Amongst a number of other information, it includes radio navigation charts which, even for VFR pilots, are extremely useful. For those seeking the IR(A), it is strongly recommended to obtain and study the introduction to this manual (see your instructor for further details) .  


2 °- QDM & QDR

Radionavigation is essentially a matter of intercepting and flying along, or tracking, a specific QDM or QDR. A QDM refers to the magnetic track followed by an aircraft flying towards a groundstation. A QDR refers to the magnetic track followed by an aircraft when flying away from it.         


QDM's and QDR's can be obtained and followed either by means of an NDB, of a VOR, of an ILS, a ground radarstation, or even by the rather old fashioned VHF/DF system which you have perhaps used already during your elementary and/or basic I.F. training.      

Assuming that you did so, most probably you did NOT take the wind effect into consideration and you simply steered the successive headings corresponding to the successive QDM's provided by the ATC controller: this is known as homing.        


Although homing allowed you to ultimately reach the station, which at the time was satisfactory, chances are that the wind drifted you away and that you reached the station from a direction which was significantly different from the initial one. During a homing procedure, the aircraft is constantly affected by the wind and keeps drifting away until it faces the wind: it is only at this stage that further QDM's will remain unchanged, as shown in figure 1.


But maybe that, once you noticed that you had always to correct your heading, either to the left, or to the right, you decided to try to maintain the last received QDM unchanged by taking an estimated drift correction: by doing so you applied in fact the basic principle of tracking.  


Tracking means to fly along a specified QDM or QDR, correcting for, and eliminating as much as possible, the wind effects. 



Needless to say that tracking is the basic requirement for radionavigation purposes if you want to stay onto the required route and avoid to end up somewhere you have no business. 


Whether for QDM's or for QDR's, let us clarify the following: the actual QDM or QDR is the one on which you actually are; the predetermined or required QDM or QDR is the one you want to be on. In fact, you seek a situation whereby the "actual" equals the "predetermined". As long as your actual QDM or QDR is within up to 10° from the "predetermined", you must apply the technique pertaining to tracking. If your actual QDM or QDR is more than 10° away of the "predetermined", you must apply the interception method.         


Consider now figure 2: the first case shows an aircraft which was initially on the predetermined QDM 090°, with a heading of 090°, but which drifted off to the right because of a northerly wind and is now on an actual QDM of 085°. The second case shows an aircraft which has drifted off to the left, because of a southerly wind, and is on an actual QDM 095°. It is obvious that, in the first case, in order to rejoin the "predetermined" of 090°, the aircraft must turn to the left while, in the second case, it must turn to the right. This leads to a first rule of the thumb: if the actual QDM is less than the predetermined QDM, the heading must be decreased; if the actual QDM is more than the predetermined QDM, the heading must be increased. This is often expressed under the mnemonic form:    





The question is: less or more than what? And by how much? The answer to the first question is: less or more than the actual QDM! Indeed, assuming that, for instance in the first case, you would steer a lesser heading of 085°, such a small correction is not enough: in fact, doing so is exactly what is done during basic homing.          


So the question remains: by how much? The basic principle of the tracking technique consists of multiplying the angular difference between "actual" and "predetermined" by 3, and applying the result (either to the left or to the right) on the value of the predetermined QDM. Figure 3 shows an aircraft which drifted off from the predetermined QDM 090° to an actual QDM of 080°, In this case we have an angular difference of 090°- 080° = 10°. In order to rejoin the "predetermined", we must alter the heading by 30° to the left, i.e. pick up heading 060°.


Now, what about QDR's? Consider figure 4: here again it shows two cases. In the first one, the aircraft has been drifted off to the right due to a northerly wind, and is now on an actual QDR of 095° instead of the predetermined one of 090°. In the second case, the wind is coming from the South and has drifted the aircraft off on QDR 085° instead of 090°. It is obvious that in the first case a correction must be made to the left, while the second case requires a correction to the right, in order to rejoin the predetermined QDR. This leads to the second rule of the thumb: during tracking outbound, if the actual QDR is more than the required QDR, the heading must be decreased; if the actual QDR is less than the predetermined QDR, the heading must be increased. Or, in mnemonic form:        






Also here, the method of taking three times the angular difference between "actual" and "predetermined" is applicable, and the result should be applied on the predetermined QDR.

Notice the mnemonics!!!    






3°- Interpretation of the ADF indications

Before going any further, let us examine the ADF indicator and see how to read it. A first detail we can notice is that the needle is a long one: we will refer to its ends as the needlehead and the needletail.


The dial is divided into 360° and is normally fixed with the 000-180 degree markings aligned with the longitudinal axis of the aircraft (many installations allow the dial to be rotated manually in order to align its indications with the D.G.: we will have a few words about this in a moment but, in the following explanations we will assume a normal fixed dial).


The upper drawing of fig.5, shows that the needlehead is always pointed towards the NDB to which the ADF is tuned. Putting it another way, it indicates the location of the station in relation to the aircraft's longitudinal axis. Although the three aircraft shown are located 270° magnetic from the station, the first one is on a heading of 270° with the needlehead showing 180°, the second one is on a heading of 045° with the needlehead showing 045°, the third one is on a heading of 135° with the needlehead showing 315°. In other words, and this is important, ANY HEADING CHANGE CAUSES THE ADF NEEDLE TO MOVE IN THE OPPOSITE DIRECTION BY THE SAME NUMBER OF DEGREES. This means that if the ADF indication changes, it may be due either to the wind or to an unintentional heading deviation. Due to this latter fact, in order to use the ADF efficiently, it is imperative to be able to keep accurate headings.           


The middle drawing of figure 5 shows that when the needlehead is located in the "northern" part of the dial, it reads QDM's. If it is located in the "southern" part of the dial it reads QDR's.          






To determine the value of the actual QDM or QDR on the ADF, apply the following method:     


1°) Assuming that the needlehead is in sector 1 of the dial (lower part of the drawing in fig.5), the degrees of deviation from the 000° mark must be subtracted from the actual heading shown on the D.G. (or the magnetic compass) in order to obtain the actual QDM. For instance, assuming that the heading reads 240° and that the needlehead reads 340°, i.e. 20° left of the 000° mark, it is said to show - 20°, and the actual QDM is:          


Heading 240° - 20° = QDM 220°  


2°) Assuming that the needlehead is in sector 2 of the dial, the degrees of deviation from the 000° mark must be added to the actual heading in order to obtain the actual QDM. If the heading reads 240° and that the needlehead reads 010°, i.e. 10° right of the 000° mark, it is said to show +10°, and the actual QDM is:      


Heading 240° + 10° = QDM 250° 


3°) Assuming that the needlehead is in sector 3 of the dial, thus reading a QDR, the degrees of deviation from the 180° mark must be added to the actual heading in order to obtain the actual QDR. If the heading reads 240° and that the needlehead reads 200°, i.e. 20° left of the 180° mark, it is said to show +20,° and the actual QDR is:  


Heading 240° + 20° = QDR 260°  


4°) Assuming that the needlehead is in sector 4 of the dial, the degrees of deviation from the 180° mark must be subtracted from the actual heading in order to obtain the actual QDR. If the heading reads 240° and that the needlehead reads 150°, i.e. 30° right of the 180° mark, it is said to show - 30°, and the actual QDR is:        


Heading 240° - 30° = QDR 210°   


Note that, when working in "QDR mode", it is sometimes more convenient to use the needletail instead of the needlehead, and subtract or add the needletail deviations from the 000° mark when it is respectively in sectors 1 or 2 (in the same way as for a QDM), but keeping in mind that the result is a QDR. 


From the previous explanations, it appears that the determination of QDM's or QDR's by means of the ADF implies the use of heading information. As these information are normally provided by the directional gyro, it is not only necessary to be able to fly a heading with great accuracy, it is also essential that the D.G. is correctly aligned with the magnetic heading. PARTICULARLY LATER. WHEN YOU WILL CONDUCT NDB APPROACH PROCEDURES UNDER ACTUAL IMC. POSSIBLY WITH OBSTRUCTIONS OR HIGH GROUND IN THE VICINITY. In addition, it is equally important that the magnetic compass is properly compensated to keep the deviations at a minimum.          


As said before, some ADF's allow to manually rotate the dial and to align it with the aircraft's heading. This allows a direct reading of the QDM or the QDR, very much in the same fashion as a so-called Radio Magnetic Indicator, or RMI. However, an RMI works automatically and does not need manual resetting because it is, in fact, a directional gyro combined with an ADF operated needle. This manual system is an additional workload and is not to be used for IFR purposes.


4°- QDM tracking technique         


Tracking a QDM is expressed as tracking inbound. Referring to fig.6, you notice that QDM 090° is the "predetermined" but that the aircraft, although flying a heading of 090°, happens to be on an actual QDM of 080°: the needlehead shows 350°, i.e. - 10°, thus 090° - 10° = QDM 080°. In order to rejoin the "predetermined", it is necessary to steer less (QDM less/steer less). According to the technique explained previously, you should correct by 3 x 10° = 30° to the left and steer 090°- 30° = 060°.


Correcting the heading by 30° to the left means that the needlehead, which indicated - 10°, will move by 30° to the right, and show +20°. At this stage, the aircraft is still on QDM 080° as, indeed, heading 060° + 20° ADF = QDM 080°.        


As the aircraft travels on heading 060 ° and approaches the predetermined QDM of 090°, the needlehead will move further to the right. The "predetermined" is reached at the moment that the needlehead shows +30°. Indeed:


Heading 060° + 30° ADF = QDM 090°    


Having rejoined the "predetermined", it is obvious that if we resume heading 090°, the aircraft will drift off again to the right. Thus, the next step is to determine an adequate drift correction in order to remain on QDM 090°. To this purpose, the initial correction to the left, which in this case was 30°, is to be reduced by half, thus 15°. In other words, you turn now to the right and steer heading 075°, thus using a drift correction of 15° (see fig.7). Note that by turning to the right by 15°, you cause the needlehead to move to the left by 15°: the end result is heading 075° + 15° ADF = QDM 090°. Note also that the needlehead indicates in fact the amount of drift correction. 


You must now maintain heading 075° as accurately as possible in order to make out whether the drift correction of 15° is adequate or not. Assuming that the needlehead stays steady at + 15°, then you are very lucky: the drift correction is satisfactory and QDM 090° remains unchanged. However, it is more likely that you will be faced with one of the two following cases:      




1°) The drift correction of 15° to the left turns out to be insufficient, and the aircraft drifts off again to the right (see fig. 8, A, B, C and D): this is indicated by the needlehead moving back to the 000° mark despite the fact that the heading is still 075°. Let us assume that you notice the needlehead at +9° instead of the required +15° (A). The actual QDM is now: heading 075° + 9° ADF = 084°. QDM less/steer less: you must turn left once more to rejoin the "predetermined". The angular difference between" actual" and "predetermined" is 6°, the normal correction to be applied is thus 3 x 6° = 18° to the left. Another way which is often used on ADF is to use the "opening" of the needle as reference, thus +9° in this case, multiply it by 3, i.e. turn left by 27°: this simplifies the calculations and expedites the return to the "predetermined". For all practical purposes, and particularly if you are still far away from the station, say 5 nms or more, you may as well pick up the same correction as before, i.e. heading 60° to return towards the "predetermined".


So, turning again to heading 060°, thus 15° to the left, causes the needlehead to move 15° to the right and to show +24° (B), i.e. still QDM 084°.          


The needlehead moves further right as the aircraft approaches again the "predetermined" and, just as was the case before, the aircraft will be back on QDM 090° when the ADF shows +30° (C).     


Once back on the "predetermined", considering that the first drift correction of - 15° was insufficient, you must take more, say - 20°, i.e. a heading of 070° (D).  


2°) The second case is illustrated in figure 9: the initial drift correction of

-15° proves to be too much and the aircraft starts to drift off against the wind. This is indicated by the needlehead moving now further to the right, away from the 000° mark. Let us assume that, although maintaining heading 075°, you notice the needlehead at +22° instead of the initial +15°. The actual QDM is now:


Heading 075° + 22° ADF = 097° 


QDM more/steer more: you should now make a correction to the right and, as the angular difference is 7, by 3 x 7° = 21° i.e. heading 111° (obviously, in this case you would not use the needle "opening" as reference, as this would imply a correction to the right of 66)°. However, as in this case you drifted off AGAINST THE WIND, applying a correction to the right might easily cause the aircraft to pass through the "predetermined" because of the resulting tailwind component, particularly at short distance from the beacon. To avoid this, the best way is to steer parallel to the "predetermined", thus to return to heading 090°, and let the wind do the job: turning to the right by 15° causes the needlehead to move by 15° to the left and show +7° instead of the earlier +22°. At this very moment the actual QDM is still: heading 090° + 7° ADF = 097°. By maintaining heading 090°, the wind will cause the aircraft to drift to the right, back to the "predetermined": the needlehead will gradually move further to the left until it reads 000° at which moment the aircraft is again on QDM 090°. As the previous drift correction of -15° proved to be too much, a smaller drift correction should be taken, for instance 10° to the left, thus flying heading 080° with +10° on the ADF. 




Determining the correct drift correction, whether in QDM or in QDR, is a matter of "trial and error": you might have to repeat the above procedures several times before you come to the adequate value. A number of things must be kept in mind when tracking a QDM, particularly by means of the ADF (although most of these items are applicable as well to other navaid types) :         


1°) It must be remembered that the distance between the various QDM's becomes smaller and smaller as you are approaching the station where they all meet at one single point (see fig.10). Because of this, when you are far away from the station, you may easily have the impression that a large drift correction is required because the ADP needle seems to be steady, but is in fact very slowly moving, degree by degree. However, as you come closer to the station, because of the reducing distance between the QDM's, this tendency becomes more apparent. As the drift correction seemed satisfactory at an earlier stage, one might become somewhat reluctant to reduce it and, instead of passing overhead the station, one passes significantly besides it.


2°) Another possible error, typical for the ADF, and often a result from the preceding, is likely to happen in the very close vicinity of the groundstation: the pilot suddenly notices that the needle moves significantly to one side, but does not realize that the aircraft is in fact about to pass slightly sideways of the station; although he should simply pick-up an average heading to correct the situation, he starts to "run behind the needle" instead, steering headings which deviate more and more from the original QDM value and might as well end up turning around the station. 


3°) In order to avoid the events described in 1° and 2°, always try to keep the drift correction as little as possible: in ADF language, try to keep the "opening" of the needlehead as small as possible. Think about this: assuming that your groundspeed is 120 kts, and that the wind blows at 90° of the track with a velocity of 120 kts as well, the resulting drift angle would be . . . only 45°. In other words, drift corrections of more than 10°, i.e. an "opening" of the ADP needle of more than 10° to maintain a specified QDM is quite a lot, and chances are that you will notice the need to reduce the "opening" when coming closer to the station. Furthermore, always verify that the heading you are steering is a reasonable one!!


4°) Assuming that you know that the wind is coming, say from the left, you may be sure that in the process of tracking a specific QDM, if the ADF needlehead is showing 000° or, even worse, showing left of the 000° mark, you will irremediably drift off to the right: if the wind is coming from the left, you must take a drift correction to the left, and the ADF needlehead must show TO THE RIGHT, possibly only one or two degrees but, let us emphasize it once more: TO THE RIGHT!    




5°) When you are coming very close to the station, say less than 2 nms, the tracking procedure as explained above becomes somewhat inappropriate and is likely to cause the aircraft to pass significantly sideways of the station: steer directly to the beacon as shown by the ADF needlehead, verifying however that the resulting heading remains a reasonable one, possibly maintaining a very small drift correction, until the needle boldly swings one way or the other when passing the station. Be aware that an ADF needle swinging slowly by ±180° indicates that the aircraft is passing besides the station (a situation which might be very questionable during later NDB approaches).


6°) Finally, remember that when flying on instruments, the ADF (as well as any other navaid for that matter) must be added to the basic instrument scanning. Keep in mind however that navaids provide only an information as to your position in relation to a specific QDM (or QDR), and tell you whether to maintain your heading, or to correct it one way or the other, and by how much. The pilot must mentally register this information, and revert immediately to the basic flight instruments for appropriate action. Never keep staring at the ADF indicator (or at any other navaid): include it at a fast rate in the instrument scanning (particularly when close to the station), but BANISH FIXATION!!!        


5°- QDR tracking technique          


Tracking a QDR is known as tracking outbound. The tracking technique is the same as for a QDM, except that you are now flying away from the station. Here again, if you are drifted off, the angular difference between the "actual" and the "predetermined" is multiplied by three to obtain the amount of correction that you must apply, to the left or to the right, to the value of the "predetermined".     


As the space between the QDR's increases with distance, tracking outbound is somewhat easier than when flying towards the station. Nonetheless, as you will perhaps notice yourself during the training, there is a marked tendency to correct to the wrong side when working QDR's on the ADF, a tendency which is practically non-existent when working in QDM. This is due to the fact that, in "QDR mode", the movements of the ADF needle may be a little confusing. Let us consider figure 11:        


1°) The upper drawing shows the predetermined QDR 090° and the aircraft on heading 090°, but drifted off on the actual QDR 100°. The needlehead, which is always pointed towards the station, shows +10°; the needletail, being deflected to the right, also shows +10°, and one tends easily - but wrongly - to correct towards it, as for a QDM.          


2°) The middle drawing shows what happens when the aircraft is steered towards the correcting heading of 060° : although the turn is made to the left, the needletail moves to the right. And this is probably an additional confusing factor: having practiced QDM tracking previously, whereby corrections are made towards the needlehead, corrections are now to be made away from . . . the needletail. Thus, by correcting 30° to the left, one sees the needletail, which was already deviated to the right, move 30° further to the right which induces an impression of turning to the wrong side. At any rate, both the needlehead and the needletail show +40°, i.e. heading 060° + 40° ADF = QDR 100°. To help you turning to the correct side, remember: QDR MORE/STEER LESS or QDR LESS/STEER MORE!!!           




3°) The lower drawing shows that, as the aircraft travels towards the "predetermined" on heading 060°, the needlehead and the needletail move back to a smaller "opening" and, once they reach +30°, the aircraft is back on the QDR 090°: at this moment, as for the QDM, the initial correction of 30° is to be reduced by half, i.e. +15° in an attempt to stay onto the "predetermined" (fig.12).     


The remainder of the QDR tracking technique is exactly the same as for the QDM's: the initial drift correction of +15° may be too small and must be readjusted, as shown on figure 13 A, B, C and D, or may be too large as shown on figure 14. Study carefully these drawings and note the movements of the ADF needle, as compared to the QDM tracking.           


Remember that, when flying away from the station, the distance between the QDR'S becomes larger and larger. Assuming that you have applied too much correction and that the aircraft has drifted off against the wind, it can take quite some time to rejoin the "predetermined" by flying parallel to it. In this case, it might be advisable to speed up things a little, particularly on longer stretches between two NDB' s, and to apply a correction into the wind, taking care however not to overshoot the required QDR.     


6°- Intercepting a QDR at station passage


Figure 15 shows an aircraft approaching the NDB on QDM 090° with the intention to intercept and fly along QDR 150°. As soon as the station is passed, the aircraft must obviously turn to the right. If a heading of 1500 in steered, it is equally obvious that the aircraft will fly parallel to the predetermined QDR of 150° (at least under no wind conditions). Thus an additional correction (you will often hear the term an "attack") must be taken in order to join the required QDR. The recommended technique is to consider about 1/3 of the angular difference between the QDM and the required QDR. In this case, the difference is 60°, 1/3 of 60 is 20, thus a correction, or an attack, of 200 should be taken on the predetermined QDR, i.e. heading 170°.


Note that by turning 80° to the right (from heading 090° to heading 170°), the needlehead, which was pointing to the rear, will swing by 800 to the right (or, if you prefer to use the needletail which was pointing forward, it will swing by 80° to the left) .          




At any rate, once the aircraft is established on the interception heading of 170°1 the needlehead will gradually move back towards the 180° mark as the successive intermediate QDR's are crossed (or the needletail will gradually move towards the 000° mark).           


The required QDR is reached when the needlehead (or the needletail) reaches the - 20° position, as indeed:          


Heading 170° - 200 = QDR 150°  


As soon as the required QDR is reached, heading 150° (plus or minus a possible estimated drift correction) is to be taken and further QDR tracking is to be conducted as previously explained.           


The 1/3 of the angular value technique works very well under no wind conditions, but one must realize that the presence of wind may dictate a larger "attack", or possibly no "attack" at all. If we take the example of figure 15, a strong wind from the West may require more than 20° to join the required QDR, particularly if it must be joined quickly as is the case in the procedure turn (discussed hereafter) . On the other hand, assuming a strong wind from the East, it may be sufficient to steer heading 1500 and let the aircraft drift off towards the "predetermined".


For those who are concerned about the 1/3rd mental calculation, don't worry too much: this 1/3rd rule is mainly to emphasize the fact that, upon passing a station, rather small "attacks", varying from just a few degrees to 30° if a 90° direction change is involved, are to be used to intercept the QDR.          


During a navigation flight, when flying from one NDB to another, the recommended procedure is to first intercept and track the required QDR from the beacon which has just been passed and, after a while, selecting the next beacon and proceed further in QDM tracking. This provides an additional means to verify that the next station has been correctly selected: you have had the opportunity to determine the required drift correction in QDR, consequently you know which deflection the needlehead should show when proceeding in QDM . . . . . and you will not fly towards a wrong NDB which you might have selected by mistake and which might be located in the same area. At any rate, in this concern, NEVER FAIL TO CHECK THE CALLSIGN OF ANY SELECTED NAVAID!


7°- Teardrop procedure turn          


Procedure turns are used to operate course reversals, i.e. to turn back and return to the station via the opposite track. They are very often used during instrument approach procedures, and may also be useful at other occasions whereby it is necessary to retrace one's steps, even for VFR purposes, for instance in case of poor weather conditions ahead. During this first lesson we will study the so-called teardrop procedure turn, of which two examples are shown in fig.16.         




In the first example the aircraft is flying along QDR 090° and is to return to the station on QDM 270° by means of a teardrop procedure turn by the left, meaning that the initial deviation from the "outbound" course is carried out to the left. The course reversal is to be carried out as follows:          


1°) First of all, notice the QDR which you are following and make sure that you are aware of the value of the reverse course. This is very easy if no wind correction is required: simply read the opposite heading on the D.G. (or possibly on the VOR/CDI). To calculate a reversed direction, use the following method:   


Actual QDR + 200° - 20 required QDM   


Actual QDR - 200° + 20 required QDM   


In this example (which of course does not need to be calculated, everyone knows that the opposite of 090° is 270°) we could say: 090° + 200° = 290° - 20 = 270°. However, the reverse of 228°, for instance, is best calculated by first subtracting 200°, i.e.:     


228° - 200 = 028° + 20 = 048°       


2°) As the teardrop procedure turn is to be carried out by the left after your current heading by 30° to the left, using a rate 1 turn;       


3°) Start the stopwatch upon rollout and, under no wind conditions, maintain the heading for 1 minute


4°) When the required time is passed, start a rate 1 turn, this time by the right, and roll out to track QDM 270°.


In the second example, where the teardrop procedure turn is carried overhead the station, instead of merely turning by 30° to the left, you must intercept the QDR offset by 30° (in this example it would be QDR 060°). This is done by using the method described above, under the heading" Intercepting a QDR at station passage". However, as you should be established on the QDR 060° within one minute, it may be advisable to increase the "attack" somewhat, as compared to the 1/3rd method, especially if the wind (in this example) would come from a westerly direction.


Still in relation with the procedure turn over the station, the stopwatch should be started when the heading passes through the predetermined ODR, in this case heading 060° moving towards the required interception heading of 050° (1/3rd of the angular difference) or, assuming that a significant wind blows from an easterly direction, and that no "attack" is required, upon rollout.       


The final interception of the required QDM is carried out in a similar way, but remember that this time you are very close to the station and that the ADF needlehead is likely to move very quickly.           


Be careful if you overshoot the required QDM and that you would pick-up heading 300° (an "attack" of 30°) to re-intercept it: it might be more advisable to proceed directly to the beacon, as explained earlier for the QDM tracking at close quarters.        


8°- Wind effects during the teardrop procedure turn    


It is obvious that the wind effects are likely to seriously affect the pattern of the manoeuvre. We mentioned already the need to "force" somewhat on the "attack" of the outbound part under certain wind conditions. As far as the teardrop procedure turn is concerned, the major point to be kept in mind is the duration of the outbound part: if you suspect a head- or tailwind component during this phase, increase or decrease the basic one minute timing by l second for each estimated 1 kts of wind component. Although this is only an approximation, it will help you to avoid flying too far "outbound" in case of tailwind (and possibly end up somewhere you are not supposed to be), or to significantly overshoot the reversed track when on your way back. Note incidentally that, for procedure turns related to an instrument approach system, a maximum allowable true airspeed (usually higher than the normal cruising speed of light training aircraft) is often published.    


Furthermore, the teardrop version brings along the concept of the so-called 60° check (see fig.17). Assuming no wind conditions, and that the manoeuvre is carried out correctly, the teardrop procedure turn will end with the aircraft's longitudinal axis being exactly aligned with the required QDM. However, as soon as wind is coming into the game, such a perfect outcome becomes rather questionable. The 60° check allows the pilot to observe the evolution of the procedure turn, and to timely take corrective action to intercept the required QDM.


The 60° check consists of verifying the position of the ADF needlehead at the moment that the heading is 60° away from the value of the required QDM. In the examples shown in fig.16, a turn to the right is carried out to intercept QDM 270°: the 60° check is thus to be carried out when passing 270° - 60°, i.e. heading 210°. Referring now to figure 17:


1°) If, upon passing heading 210°1 the ADF needlehead shows an "opening" of about 60°, considering the fact that the heading has still to increase by 60° the needle will be practically reading 000° by the time the heading reaches 270°, which corresponds with QDM 270° (note that a similar additional check at 30° "opening" may be used as well);        




2°) If the "opening" is significantly more than 60°, it indicates that the aircraft is going to overshoot the required QDM. And indeed, by the time that the heading reaches 270°, the needle will still show a deviation to the right. Do not react impulsively by increasing the bank angle in an attempt to avoid it! The rate 1 turn must be normally continued beyond the value of the required QDM in order to roll out on a suitable "attack" to re-intercept it. Usually the amount of "attack" should correspond to an ADF "opening" of 30° to the opposite side in order to ensure rejoining the "predetermined" (in this case, the moment of roll out is in fact dictated by the ADF, rather than by the D.G.). At this stage, verify the actual QDM and, if you notice that you are within 10° of the "predetermined", adjust the heading to 300° (3 x 10° on the "predetermined") and complete the normal tracking procedure as mentioned above (assuming that you notice that you are away of the "predetermined" by more than 10°, refer to the method described under 3° below). However, if the procedure turn is carried out over the station, as you are very close to the beacon, it might be more advisable to proceed directly to it in case of overshoot, and to intercept the subsequent QDR.           


3°) If on the other hand, the "opening" is significantly less than 60°, the aircraft is undershooting the required QDM. If the rate 1 turn is continued normally until heading 270° is reached, the needle will pass through the 000° mark and show a deviation to the left. This must be avoided by discontinuing the turn, so as to stop the ADF needlehead at an "opening" of 30 ° to 40° (depending on the importance of the undershoot), from where the required QDM 270° can be intercepted. Assume for instance that. upon reaching heading 210° (as shown in fig. 17), the ADF needlehead shows an opening of +30°: the QDM is thus 240° (210° + 30°). This is clearly an undershoot and you should act as follows:         


- roll out on heading 210° and maintain it;         


- the ADF needlehead will now gradually move from +30° to +40°, at which moment the actual QDM will be 2.1.0° + 4.0°, i.e. 250°;         


- turn to the right by 10° to heading 220°: the ADF needlehead will move to the left and show again +30°, i.e. still QDM 2.50° (2.20° + 30°);      


- maintaining: now heading: 220° will cause the ADF needlehead to move again from +30° to +40°; the QDM is now 260° (22.0° + 4.0°);      


- QDM 260° is 10° away from the "predetermined" QDM of 270°; you are now in tracking condition: pick heading 240° up, i.e. an "attack" of 30° in the "predetermined": this involves a heading change of 20° to the right, causing the ADF needlehead to move by 20° to the left, i.e. from +40° to +20°. Once on heading 240°, the needlehead will gradually move towards +30°, i.e. towards QDM 270°.


Be aware that the original over- or undershoot of the predetermined QDM is most probably due to a tail- or headwind component during the outbound part of the procedure turn. In other words, you may expect a crosswind component when finally established on QDM 270°: consequently. DO NOT ROLL OUT EXACTLY ON HEADING 270°, as this would cause the aircraft to drift off, BUT MAINTAIN A SLIGHT CORRECTION AGAINST THE WIND SO THAT THE ADF NEEDLEHEAD. SHOWS AN INITIAL "OPENING" OR 5° TO 10° ("opening" which, of course depending on the circumstances, might need to be subsequently corrected). QDM interceptions will be discussed further in lesson 03.  


Although the following is material for the later IFR training, assuming that you are performing an instrument approach whereby a procedure turn (sometimes referred to as a base turn) is involved, it is usually necessary to notify the ATC that you are "beacon outbound" when in the process of intercepting or tracking the required QDR. Remember that the radiotransmissions are always the last of your priorities which can be memorized as:        




- TURN: initiate the rate 1 turn;     


- TIME: start the stopwatch when passing through the heading corresponding to the required QDR or, if no attack is needed, upon rollout.     


- TRACK: see that you are established on the required QDR, or at least that you have a satisfactory "attack";           


- TALK: report to the ATC.  


9°- Questionary


01.- QDM MORE/STEER MORE, QDM LESS/STEER LESS: steer more or less than what?


02.- QDR MORE/STEER LESS, QDR LESS/STEER MORE: steer more or less than what?


03.- Draw a circle whose centre represents the location of an NDB, and graduate it in 360°. To develop your spatial orientation ability, draw lines to or from the centre representing: QDR 060°, QDM 310°, QDR 120°, QDM 070°, QDM 350°.


In questions 04 to 08 state whether the ADF shows a QDM or a QDR and its associated value:           


04.- Heading is 120°. ADF needlehead shows 20° left of 000°, thus: __________°          


05.- Heading is 300°. ADF needlehead shows 15° right of 000°, thus: __________°       


06.- Heading is 240°. ADF needlehead shows 20° left of 180°, thus: __________°          


07.- Heading is 060°. ADF needlehead shows 10° right of 180°, thus: __________°       


08.- Heading is 155°. ADF needletail shows 10° right of 000°, thus: __________°           


09. Predetermined QDM is 155°. Heading is 155°. ADF needlehead shows 3° left of 000°. Actual QDM is _____°. You should steer heading _____° to rejoin QPM 155°.


10.- Predetermined QDR is 208°. Heading is 208°. ADF needletail shows 5° right of 000°. Actual QDR is _____°. You should steer heading _____° to rejoin QDR 208°.        


11.- Assuming that you are flying along QDR 180° under no wind conditions, you need to perform a teardrop procedure turn, by the right. Head is _____° for duration of _____.


12. - You estimate a headwind component of 25 kts during the outbound part of a procedure turn. The timing should be _____.


13.- You estimate a taiIwind component of 35 kts during the outbound part of a procedure turn. The timing should be _____.


14.- You are approaching an NDB on QDM 135° under no wind conditions. Upon station passage, you must intercept QDR 165°. To this purpose you should steer heading _____°. You will reach QDR 165 when the ADF needletail shows _____°.           


15.- You pass overhead one NDB and must proceed to another one           located at a considerable distance. It is recommended: a) to first establish outbound on the required QDR before selecting the second NDB, b) to select the second NDB immediately at station passage.


16.- What is the purpose of the 600 check?      


17.- You reach an NDB on a track of 230°. You must perform a teardrop procedure turn by the right. You are in the left turn to intercept the reversed track of _____°. Which heading should you have when the ADF needlehead shows - 60°?    


18.- See question 17. You have 60° to turn and the ADF needlehead shows - 80°. This shows: a) an overshoot, b) an undershoot.


19.- See question 17. You have 60° to turn and the ADF needlehead shows - 50°. This shows: a) an overshoot, h) an undershoot.       




As you trained basic I.F. on the simulator, you are now accustomed to it and the instructor will probably start this session      by putting, you at once in flight, at a specified altitude and heading, and at normal cruising speed.        


Remember that any time an NDB, or other navigational aid for that matter is selected, YOU MUST IDENTIFY ITS MORSE CODE. This will in fact be the very first exercise: while flying accurately on a constant heading, constant altitude and constant airspeed, select the correct frequency on the ADF, select the audio panel as required, verify that the volume is adequate, and identify the station's Morse code. And remember, if the NDB is of the Al type, you must select "BFO", and return to "ADF" after proper identification. Don't haggle too long with these proceedings: divide your attention between the ADF manipulations and, which is essential at all times, flying the aircraft. Never let your attention be diverted from the basic I.F. for more than three seconds: if you notice that one of the flight parameters (altitude, speed, heading, or power setting) is significantly erroneous, correct it first, then carry on with the ADF setting.      


Once you have properly selected and identified the NDB, you will be instructed to proceed directly to the station. When the ADF needlehead shows 000°, note the heading: this will be your actual QDM. For this attempt to tracking first inbound, a no wind conditions will be used. All you have to do is to accurately maintain the heading. Remember that any change in heading causes the needlehead to deviate to the opposite side and may give the impression that you are drifted off by (at this stage inexistent) wind.   


Assuming that you followed the heading correctly, station passage will be identified by a positive 180° swing of the needle.           


Proceed further in tracking outbound, maintaining the same direction. After the swing of the needle has occurred, give it a few seconds to settle: if your heading hold was accurate, it will do so almost immediately on the 180° mark.


After a short while the instructor will instruct you to perform a teardrop procedure turn by the right or by the left and to track inbound again. You will then be required to intercept an offset QDR (offset by no more than 90°).        


A second teardrop procedure turn will lead you back to the station where a teardrop overhead will be carried out. When again established outbound, the instructor will notify you that he has now introduced a wind component: up to you to determine if the wind is coming from the left or from the right. 


Note: Assuming plain head- or tailwind, no drift correction is required (only the groundspeed will be influenced). This means that, the slightest error in heading hold, whether to the left or to the right will respectively induce a drift either way. For instance, assuming a plain headwind while tracking 270°. If your heading happens to be less than 270° you will notice a drift to the left, on the other hand, if your heading happens to be more than 270° you will drift off to the right: this can be a little confusing before it is realized that no drift correction whatsoever is required.      


Once you have been able to determine the general direction of the wind, another teardrop procedure turn will be requested, followed by inbound tracking, still with the same wind, and again a teardrop procedure turn shall be carried out upon station passage.     


As far as tracking inbound is concerned, remember to reduce the opening of the ADF needlehead to the minimum possible as you come closer to the station, and to verify that the heading you steer remains a reasonable one. Also remember that, if the wind is coming from the left, the drift correction must be made to the left and the ADF needlehead must show to the right, were it only one or two degrees, and vice-versa.





Similar exercises will be carried out for the duration of the time remaining, possibly including partial panel operation.      



This flight session, as well as all the subsequent ones will be           conducted mainly with the EVRD, and/or possibly in IMC conditions if these prevail. If the latter is the case, think about possible carburettor icing. 


The exercises studied in the simulator will be repeated in actual flight, preferably using an A2 NDB to avoid ADF needle unsteadiness and, as far as I.F. is concerned, in full panel. Obviously, the wind conditions being ever present, prepare yourself to cope with them. 


Conditions permitting the takeoff will be carried out on instruments. Once airborne, the EVRD should not be removed unless operating in solid IMC. The initial part of the flight will be used to review some basic I.F. exercises, either in full or partial panel, as the instructor sees fit. It is also during this part of the flight that you will be requested to select and identity the beacon on which the further exercises will be conducted.


Assuming VMC conditions, the return to base may include either a practice forced landing, a spot landing or a precautionary landing (see ELEMENTARY FLIGHT TRAINING MANUAL). Alternatively, and particularly if IMC prevails, the instructor will "nurse" you through an NDB approach, thus combining the previous exercises with the necessary descents, speed reductions and checklists (note that the full study of instrument approaches is part of the IFR flight training phase).     



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