Easy Access Rules for Aircrew ANNEX I (Part-FCL)

(Regulation (EU) No 1178/2011)

SUBPART D – COMMERCIAL PILOT LICENCE – CPL

SUBJECT 061 – NAVIGATION – GENERAL NAVIGATION

ED Decision 2020/018/R

Mental dead reckoning (MDR)

Where the term ‘mental dead reckoning’ (MDR) is used within a Learning Objective (LO), the applicable technique which will be used for the European Central
Question Bank (ECQB) questions is based on the methods shown below.
Examination questions will state that an MDR technique is required to produce the solution. If other techniques (e.g. trigonometry) are used to determine
the answer, then the determined answer may be incorrect.
MDR crosswind component (XWC)
The XWC can be calculated using a ‘clock code rule’, where each 15° of wind angle is represented by 1/4 of an hour — meaning 1/4 the wind strength.
The XWC can be estimated using the values from the table below:
Wind angle 15° 30° 45° 60°
% of wind speed 25 50 75 100
(Wind angle (WA) is the angle between the wind vector and the track/runway direction to the nearest 10°)

Example:
RWY 04 and surface wind from tower is 085°/20 kt. What is the XWC?
WA = 45°
XWC = (0.75) × 20
= 15 kt

MDR headwind component (HWC)/tailwind component (TWC)

The H/TWC can be estimated using the values from the following table:
90° – wind angle 10° 20° 30° 40° 50° 60°
% of wind speed 0.2 0.3 0.5 0.6 0.8 0.9

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 Easy Access Rules for Aircrew ANNEX I (Part-FCL)
(Regulation (EU) No 1178/2011)
SUBPART D – COMMERCIAL PILOT LICENCE – CPL

To assist recall, an aid is shown below:

90° – wind angle 10° 20° 30° 40° 50° 60°
Aid 1 1 2 2 3 3
% of wind speed 0.2 0.3 0.5 0.6 0.8 0.9

Example:
RWY 04 and surface wind from tower is 080°/20 kt. What is the HWC?
WA = 40°
90° – WA = 50°
HWC = (0.8) × 20
= 16 kt

Alternately, for XWC and TWC/HWC MDR calculations, the values in the following table can be used, assuming XWC = wind velocity × sine WA and TWC/HWC = wind
velocity × cosine WA:

Wind angle 0° 10° 20° 30° 40° 50° 60° 70° 80° 90°
Sine 0 0.2 0.3 0.5 0.6 0.8 0.9 0.9 1 1
Aid 0 1 1 2 2 3 3 2 2 1

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 Easy Access Rules for Aircrew ANNEX I (Part-FCL)
(Regulation (EU) No 1178/2011)
SUBPART D – COMMERCIAL PILOT LICENCE – CPL

MDR triangle of velocities (TOV)

Heading is determined by calculating the XWC as previously described, then applying the 1:60 rule to the TOV as follows:

Wind vector

Track and Heading and

ground speed TAS vector
vector

WCA

This MDR technique works for the relatively small WCAs which are typical for medium to high TAS values (the ground speed (GS) therefore can be assumed
to be equal to the TAS for application of the 1:60 rule).

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 Easy Access Rules for Aircrew ANNEX I (Part-FCL)
(Regulation (EU) No 1178/2011)
SUBPART D – COMMERCIAL PILOT LICENCE – CPL

Example 1:
Planned track = 070° (T)
TAS = 400 kt
WV = 100° (T)/40 kt
WA = 30°
XWC = (0.5) × 40
= 20 kt

20 kt

≈ 400 kt

3°

Heading required = 073° (T)

GS is determined by using the headwind/tailwind example previously explained.
WA = 30°
90° – 30° = 60°
HWC = (0.9) × 40
= 36 kt
GS = 400 – 36 = 364 kt

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 Easy Access Rules for Aircrew ANNEX I (Part-FCL)
(Regulation (EU) No 1178/2011)
SUBPART D – COMMERCIAL PILOT LICENCE – CPL

Example 2:
Planned track = 327° (T)
TAS = 240 kt
WV = 210° (T)/70 kt
WA = 60°
XWC = (0.9) × 7
= 63 kt

63 kt

≈ 240 kt

16°

WCA = 16°
Heading required = 311° (T)
GS is determined by using the headwind/tailwind example previously explained.
WA = 60°
90° – 60° = 30°
TWC = (0.5) × 70
= 35 kt
GS = 240 + 35 = 275 kt

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 Easy Access Rules for Aircrew ANNEX I (Part-FCL)
(Regulation (EU) No 1178/2011)
SUBPART D – COMMERCIAL PILOT LICENCE – CPL

VFR navigation (061 02 00 00)

The techniques referred to within the LOs are based on the methods as described below.

Mental dead reckoning (MDR) off-track corrections

Based on the 1:60 rule
1 NM of cross-track error (XTE) for every 60 NM along track from waypoint = 1° of track error angle (TKE).

1 NM of XTE for every 60 NM along track to waypoint = 1° of closing angle (CA).

Change of heading required to regain track in same distance as covered from waypoint to position off track = 2 × TKE.

Change of heading required to reach next waypoint from position off track = TKE + CA.

Example 1:
Planned heading is 162° (T), and after 40 NM along track the aircraft position is fixed 2 NM right of planned track. What heading is required to regain track in
approximately the same time as has taken to the fix position?
TKE = 3°
Heading required = 156° (T)

Example 2:
Planned heading is 317° (T), and after 22 NM along track the aircraft position is fixed 3.5 NM left of planned track. What heading is required to fly direct to
the next waypoint which is another 45 NM down track?
TKE = 10°, CA = 5°
Heading required = 332° (T)

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 Easy Access Rules for Aircrew ANNEX I (Part-FCL)
(Regulation (EU) No 1178/2011)
SUBPART D – COMMERCIAL PILOT LICENCE – CPL

Mental dead reckoning (MDR) estimated time of arrival (ETA) calculations

Round the GS to the nearest NM/min, and then make the same percentage adjustment for the distance.

Example:
Distance to go = 42 NM
GS = 132 kt

GS rounded to 120 kt = 2 NM/min

Percentage change = 10 %
Distance = 42 – 10 % = 38 NM
Time = 38 / 2 = 19 min

Unsure-of-position procedure
As soon as the position of the aircraft is in doubt:
1. note the time;
2. communicate if in contact with an air traffic control (ATC) unit to request assistance;
3. consider using any radio-navigation aids that may be available to give position information (do not become distracted from flying the aircraft safely);
4. if short of fuel or near controlled airspace, and not in contact with ATC, set 121.5 MHz and make a PAN call;
5. if that is not necessary, check the directional indicator (DI) and compass are still synchronised and continue to fly straight and level and on route plan
heading;
6. estimate the distance travelled since the last known position;
7. compare the ground with your estimated position on the map (look at the terrain for hills and valleys or line features such as a motorway, railway, river
or coastline);
8. once the position has been re-established, keep checking the heading (and look out for other aircraft) and continue the flight by updating the estimated
position regularly while looking for unique features such as a lake, wood, built-up area, mast, or a combination of roads, rivers and railways.

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