Lesson 03: ADF: Transition from QDM to another tansition from one QDR to an offset QDM

A. - BRIEFING

1°.- spatial orientation

In the previous lesson, we mentioned the need for so-called spatial orientation. This means that, besides the use of the mnemonics QDM LESS/STEER LESS, QDM MORE/STEER MORE, QDR LESS/STEER MORE, QDR MORE/STEER LESS, it is also necessary to be able to visualize the position of the aircraft in relation to a ground station. It is indeed a fact that, although these mnemonics can be very useful 1 they can also induce errors if we don't pay attention. Let us take an example: assuming that you are on QDM 070°, and that you are requested to intercept QDM 360°, QDM LESS/STEER LESS makes you turning to the left when a turn to the right is required. In fact, the mnemonic system is mainly useful for tracking, but for interceptions it is often preferable to rely on visualization.

Spatial orientation, as such, implies that you can form a clear picture of a specific situation in your mind, and act accordingly without being confused. For most individuals, spatial orientation becomes easier when using one of the indicators in the cockpit, for instance the attitude indicator (see fig.20) Imagine that the instrument is divided in 360° and that its centre is the location of the groundstation. Remember also that a QDM is oriented TOWARDS the station, thus towards the centre of the instrument and, assuming that a QOR is involved, it is oriented AWAY FROM the station, thus away from the centre of the instrument towards its edge, Going back to the example above I you can easily imagine the tracks 070° and 360° going towards the centre (as both are QDM's), which evidently confirms that a turn to the right is needed (see also question 03 in lesson 01).

 

2°.- Transition from one QDM to another

 

Whenever you must proceed from one QDM to another, and that you have determined in which direction to turn, the next question is which heading to take. To this purpose, the following method, is recommended :

 

 

 

1°) If there is difference more than 30° between the "actual" and the "predetermined", an "attack" of 60° should be taken on the "actual";

 

2°) If the difference between the II actual" and the "predetermined" is more than 10°, up to 30°, an "attack" of 30° should be taken on the "actual";          

 

3°) If the difference between the "actual" and the "predetermined" is 10° or less, an "attack" of three times the angular difference should be taken on the "predetermined". Note that, in this case, you are in the process of tracking, which was discussed in lesson 01.   

 

2 PAGES DE SCHEMAS

 

Figure 21 shows an aircraft departing QDM 090° to intercept QDM 360° (which, incidentally, is also QDM 000°): 

 

1°) We know that we must turn to the right, and that there is more than 30° between "actual" and "predetermined". Consequently, we must steer 090° + 60° = heading 150° (A);      

 

2°) Turning by 60° to the right causes the ADF needlehead to swing by 60° to the left. Thus, at that very moment we have heading 150° - 60° = still QDM 090° (A);         

 

3°) As the aircraft proceeds on heading 150°, the ADF deflects further to the left: when it shows - 70°, we have heading 150° - 70° = QDM 080°. Still more than 30° away: we take an "attack" of 60° on the new "actual", i.e. we steer 080° + 60° = heading 140° or, in other words, we turn 10° to the left (B). This causes the ADF to show again - 60°;  

 

4°) As the aircraft proceeds on heading 140°, the ADF deflects further to the left: when it shows - 70°, we have heading 140° - 70° = QDM 070°. Still more than 30° away: we take an "attack" of 60° on the new "actual", i.e. we steer 070° + 60° = heading 130°, thus another 10° to the left (C). This causes the ADF to show again - 60°;      

 

5°) etc.: every time the ADF shows - 70°, we bring it back to - 60° by correcting the heading by 10° (points D, E and F) ;           

 

6°) At point F, we are on QDM 040°, still more than 30° away, and we steer heading 100° to bring the ADF back to - 60°;          

 

7°) As the aircraft proceeds on heading 100°, the ADF deflects further to the left: when it shows - 70°, we have heading 100° - 70° = QDM 030°, which is 300 away from the "predetermined" : at this stage we reduce the "attack" to 30° on the "actual'", Consequently we steer 030° + 030° = heading 060°, which means a heading change of 40° and causes the ADF to move back by 40° and show - 30° (G);     

 

8°) As the aircraft proceeds on heading 060°, the ADF deflects towards - 40°, showing QDM 020°, thus more than 10° away; we steer now heading 050°, which brings the ADF back to -30° (H);           

 

9°) As the aircraft proceeds on heading 050°, the ADF deflects towards

-40°, showing QDM 0100/ which is 10° away from the "predetermined" (I). We are now within the normal tracking requirements and take an "attack" of 30° on the "predetermined", i.e. heading 030° (I): this causes the ADF to swing towards -20° and the final QDM 000° will be reached when the ADF shows -30° (J).

 

Remarks regarding the 60° check

 

Coming back to the 60° check (see page RN 15), and considering the example of figure 17, another way to handle the 60° check is as follows:     

 

a) Assuming that, up-on passing heading 210°, the ADF needle shows an opening of 90°. It does not simply show that you overshot the predetermined, but it also shows that you are on QDM 300° (210 + 90), i.e. you overshot the predetermined by 30°. According to the method explained in this lesson, you should continue the turn and roll out on an interception heading of 330°.     

 

b) Conversely, assuming that the ADF needle shows an opening of only 20° when passing heading 210°, this means that you are on QOM 230° (210 + 20), i.e. you undershoot the predetermined by 40°. According to the method explained in this lesson, this calls for an interception heading of 60 ° on the actual QDM, i.e. heading 170° . . . . . which you passed already significantly. However, as you are fairly close to the station, turning to the left now to pick up heading 170° is probably a bit too much to be good. The best way is to roll out immediately on heading 210°, and maintaining it while closely watching the ADF needle (without staring at it!!!) moving to an opening of +30°, i.e. QDM 240° (you are now 30° away from the predetermined and heading 210° is fine) In order to complete the interception, maintain heading 210° until the ADF shows +40°, thence:    

 

- ADF +40°, QDM is 250°: - steer heading 220° 

- ADF goes back to +30°     

 

- ADF +40°, QDM is 260° : - steer heading 240°.          

- ADF goes back to +20° . . . . .       

 

. . . you are now within 10° of the predetermined, in tracking conditions.    

 

 

3°.- Transition from a QDR to an offset QDM     

Switching from one QDM to another or, as we discussed in lesson 02, from one QDR to another, are manoeuvres which can be required in normal operations. Departing a QDR and coming back to the station via an offset QDM is a purely academic exercise whose sole purpose it is to further develop one's spatial orientation capability. Figure 22 shows an aircraft departing QDR 120° in order to intercept QDM 260°. This manoeuvre is carried out in exactly the same way as the previous QDM to QDM transition, the only problem being to determine the direction of the initial turn and the heading on which it must be stopped:        

 

1°) To determine the direction of the initial turn, visualize the actual QDR on one of your fligl1t instruments as explained before, and do the same for the required QDM: this will clearly show that the turn is to be executed to the left;       

 

2°) Determine the angle between the actual QDR and the required QDM. To this purpose, you can convert the actual QDR into QDM: 120° + 200 = 320° - 20° = QDM 300°. As the difference between the actual and the predetermined QDM is more than 30°, you must take an "attack" of 60° on the actual QDM. Thus, as you are turning to the left, you must roll out on 300° + 60°, i.e. heading 360 ° (or 000°).

 

Note: To determine which initial heading you are to take, once you have determined that the turn is to be made to the left and verified the angular difference involved, you might as well imagine the aircraft flying along QDM 300°, and in this case ADD 60° to find heading 360° (or 000°)

 

3°) When established on heading 360° (000°), the ADF needlehead will show - 60° . . . . .  and you are on your way.  

 

In this example, with the heading 360° (000°), the ADF will deflect towards - 700, at which moment you reach QDM 290° and are 30° away from the "predetermined": this requires only 30° of "at tack" on the "actual", i.e. heading 320°. The remainder of the exercise is to be completed as for the previous one. 

 

Note: The reason for using. "attacks" on the actual when moving from one QDM to another, and reducing the attacks as the "predetermined" is approached instead of an "attack" directly on the "predetermined" as is the case when moving from one QDR to another, can be seen in figure 23:

 

- Aircraft A is on QDM 310°: assuming a 60° "attack" on the "predetermined" 000°/360°, this would produce a heading of 300° leading the aircraft very close to the station with a 60° "opening" upon reaching the "predetermined" (or 50° "opening" when within 10° of it). Considering the very short remaining distance to the station, this would be a problem to establish the aircraft properly on the "predetermined". 60° on the "actual", i.e. heading 250° is thus more appropriate. 

 

 

1 PAGE DE SCHEMAS

 

- Aircraft B is on QOM 330°, i.e. 30° away from the "predetermined" where the "attack" is to be reduced to 30° (this is simply to "dampen" the interception procedure required in normal operations. Departing a QDR and coming back to the station via an offset QDM is a purely academic exercise whose sole purpose it is to further develop one's spatial orientation capability. Figure 22 shows an aircraft departing QDR 120 ° in order to intercept QDM 260°. This manoeuvre is carried out in exactly the same way as the Previous QDM to QDM transition, the only problem being to determine the direction of the initial turn and the heading on which it must be stopped:      

 

1°) To determine the direction of the initial turn,            visualize the actual QDR on one of your flight instruments as explained before, and do the same for the required QDM: this will clearly show that the turn is to be executed to the left;

 

2°) Determine the angle between the actual QDR and the required QOM. To this purpose, you can convert the actual QDR into QDM: 120° + 200 = 320° - 20° = QDM 300°. As the difference between the actual and the predetermined QD.M is more than 30°, you must take an "attack" of 60° on the actual QDM. Thus, as you are turning to the left, you must roll out on 300° + 60°, i.e. heading 360° (or 000°) .

 

3°) When established on heading 360° (000°), the ADF needlehead will show - 60° . . . . . and you are on your way.  

 

In this example, with the heading 360° (000°), the ADF will deflect towards -70°, at which moment you reach QDM 290° and are 30° away from the "predetermined": this requires only 30° of    "attack" on the "actual", i.e. heading 320°. The remainder of the exercise is to be completed as for the previous one. 

 

Note: The reason for using "attacks" on the actual when moving from one QDM to another, and reducing the attacks as the "predetermined" is approached, instead of an "attack" directly on the "predetermined" as is the case when moving from one QDR to another, can be seen in figure 23:           

 

- Aircraft A is on QRM 3100: assuming a 600 "attack" on the "predetermined" 000°/360°, this would produce a heading of 300° leading the aircraft very close to the station with a 60° "opening" upon reaching the "predetermined"         (or 50° "opening" when within 10° of it). Considering the very short remaining distance to the station, this would be a problem to establish the aircraft properly the "predetermined". 60° on the "actual", i.e. heading 250° is thus more appropriate. 

 

- Aircraft B is on QDM 330°, i.e. 30° away from the "predetermined" where the "attack" is to be reduced to 30° (this is simply to "dampen" the interception procedure somewhat). However, 30° on the "predetermined" would give way to a heading of 330°, i.e. no "attack" at all. This case clearly shows why the "attack" is to be taken on the "actual".

1 PAGE DE SCHEMAS

 

- Aircraft C is on QDM 350°, i.e. 10° away from the "predetermined", thus in the last stage of the interception where, according to the tracking theory, 30° "attack" is taken onto the "predetermined" instead of on the "actual''. 

 

4°- Questionary"      

 

Find mentally the direction of the initial turn and heading to be steered then crosscheck on paper:

01.- You are established on QJ2M 220°. You must intercept QDM 270°. Turn to the _____ on heading _____°.

 

02.- You are established on QQM 130°. You must intercept QDM 040°. Turn to the _____ on heading _____°.

 

03.- You axe established on QQM 030°. You must intercept QDM 350°. Turn to the _____ on heading _____°          

 

04. - You are. established on QDM 010°. You must intercept QDM 340°. Turn to the _____ on heading _____°.

 

05. - You are established on QDM 160°. You must intercept QDM 190°. Turn to the _____ on heading _____°.         

 

06. - You are established on QDM 330°. You must intercept QDM 340°. Turn to the _____ on heading _____°.         

 

07. - You are established on QDM 160°. You must intercept QDR 220°. Turn to the _____ on heading _____°.

 

08. - You are established on QDM 040°. You must intercept QDR 050°. Turn to the _____ on heading _____°.         

 

09. - You are established on QDM 130°. You must intercept: QDM 240°. Turn to the _____ on heading _____°.         

 

10. - You are established on QDM 130°. You must intercept QDM 240°. Turn to the _____ on heading _____°.         

 

11.- You are established on QDM 260°. You must intercept QDM 170°. Turn to the _____ on heading _____°.

 

12.- You are established on QDM 260°. You must intercept QDM 170°. Turn to the _____ on heading _____°.         

 

13. - You are established on QPM 040°. You must intercept QDM 340°. Turn to the _____ on heading _____°.         

 

14. - You are in partial panel, established on QDM 080°. You must intercept QDM 000°. Turn to the _____ on heading _____°. As far as the magnetic compass is concerned, which execution is required to pick up this heading? And to stay on it?

 

15.- You are in partial panel, established on QDM 190°. You must intercept QDM 230°. Turn to the _____ on heading _____°. As far as the magnetic compass is concerned, which precaution is required to pick up this heading? And to stay on it?         

 

16.- You are in partial panel, established on QDM 330°. You must intercept QDR 030°. Turn to the _____ on heading _____°. Which precaution is required to pick up this heading? Once established on the interception heading, you must reduce speed. How does the magnetic compass react? Which precaution are you to take in this concern?       

 

B.- SIMULATOR TRAINING

You will be immediately positioned in flight, at normal cruising speed and at a specified altitude, at a reasonable distance from an NDB, and established on a specified QDM.

 

The instructor will then instruct you to intercept QDM XXX°, usually 50° to 60° away from the "actual". Take the time to think it over. Visualize the problem on one of the instruments. Do not    rely too much on the QDM LESS/STEER LESS - QDM MORE/STEER MORE method. Be extremely cautious when the "actual" and the "predetermined" are located each side of North.     

 

The instructor will reposition you two or more times to enable you to practice similar exercises with various QDM's: at least one of these should be carried out completely, until the interception of the predetermined QDM, the remainder may be executed only partly, and discontinued after the first stages of the process (such a procedure can be rather lengthy when carried out in          full, especially when far away from the station).       

 

During the last part of this session you will be established on           a specific QDM, from which you will have to intercept a QDM. It is especially the initiation of this manoeuvre which is important: turning in the correct direction and taking the correct initial heading, the subsequent part, being the same as in the previous exercises. Also this manoeuvre can be repeated by repositioning without undue loss of time. Partial panel, should be practiced at least once during these last exercises. In this latter case, keep in mind the magnetic compass' turning and acceleration/deceleration errors: in this concern, it may also be useful to remember the theory' of timed turns (see "Basic Instrument Flying").      

 

Remember that precise basic I.F. remains, as always, the most important requirement. You will perhaps experience some difficulties at this stage, pondering on what you are instructed to do and, at the same time keeping the flight parameters (altitude, speed and heading) as steady as possible until you have made out the required way of action. Don't be overly worried! Things will probably go a lot smoother during the associated flight session. At any rate, try to relax! As said before, take your time! It is not because you are instructed to intercept this or that QDM that you must react immediately! And don't get tense at the control wheel (or the rudder)! Remember that if the aircraft is properly trimmed, it flies practically hands off.          

 

C. -  FLIGHT TRAINING     

 

- Takeoff on instruments, climb initially at Vx, then further at Vy, using climb power, after takeoff checklist.     

 

- Maintain runway axis using available locators; if no locators are available, use an estimated drift correction until instructed to proceed to an available NDB.  

 

- While climbing, or when established in normal cruise, intercept QDR AAA; don't forget the cruise checklist;      

 

- When established on QDR AAA, increase airspeed to maximum, using full power maintaining altitude and correct tracking; trim properly (the purpose of this speed increase is mainly to gain some time in order to position the aircraft at a suitable distance for the subsequent exercises);   

 

- When at a suitable distance from the beacon, reduce to circuit speed and, when this speed is reached and the aircraft properly trimmed, procedure turn by the left or by the right (the procedure turn can be anyone of the three possibilities: teardrop, standard or 80°/260°);

 

- When inbound to the beacon intercept QDM BBB;   

 

- When passing the beacon, intercept QDR CCC and resume normal cruising speed;   

 

- When established on QDR CCC, intercept QDM DDD.

 

Similar exercises should be continued on various QDM's and QDR's for the remaining time of the session. The exercises may be combined with climbs and descents, both at 500 ft/min {see vertical S exercise in basic I.F.).        

 

One interception exercise should be carried out in partial panel.     

 

Learn to spread your wings
Our partners Sign in
Flying Group Jeppesen  
Email address
Password