IFR Planning Minimas
There are minimum meteorological conditions that will have to be met for us to select an airport. Depending on the conditions of the day, we will need alternate airports to make sure we can land somewhere.
To find out if weather conditions allow us to select an airport, we will go to the approach charts: each airport usually has more than one approach, and each approach is defined in these charts, where the minimum visibility or cloud ceiling necessary to complete each approach are indicated.
Each operator has its own charts, approved by the competent authority, or hires a chart service. What we want to know at this point, the minimum visibility or cloud ceiling, will be indicated in the approach charts as in the Figures 3.3.1 and 3.3.2. Depending on the aircraft category, the minimums vary. Let us assume we are flying a category B twin-engine pist
Figure 3.3.1. Chart minima. Precision approach.
Figure 3.3.2. Chart minima. Non-precision approach.
As for the minimums, we will have the following:
- Takeoff minima
- Takeoff alternate minima
- Arrival minima
- Airport operating minima
- Arrival alternate minima
TAKEOFF MINIMA
For single engine airplanes, visibility should not be less than 800 m. For multi-engine airplanes, the minima will be the following. Always check the visibility at your aerodrome charts. 3.4
Figure 3.3.3. Takeoff minima for multi engine airplanes.3.4
Multi-engine airplanes unable to attain an altitude of 1500 feet above ground level (AGL) and ensure obstacle clearance in the event of an engine failure will follow a different criteria. These airplanes may be operated under the following take-off conditions, provided they can adhere to the relevant obstacle clearance criteria, assuming an engine failure occurs at the specified altitude. The operator-determined take-off requirements should be established based on the height at which the one-engine-inoperative (OEI) net take-off flight path can be formulated. The minimum Runway Visual Range (RVR) used should not fall below the values outlined in Table below:
Figure 3.3.4.
These values apply for operations that are not approved for low visibility takeoff (LVTO). Low visibility conditions means meteorological conditions with a runway visual range (RVR) of less than 550 m. 3.5
In case the visibility falls below 400m we will require specific approval and the following conditions. 3.5
Figure 3.3.5.
It is possible to perform a take off if the visibility is lower than 125 m but not less than 75 m. The requirements for this are having runway centre line lights spaced 15 m or less and having an approach with at least Cat III requirements.
If we do not have the runway visual range (RVR) value but we have the visibility, we can apply the following table to convert the visibility into RVR.
Figure 3.3.6. Conversion of visibility to RVR.
A visibility conversion to RVR/CMV should not be used to calculate the takeoff minima, for CAT II/III approaches, when there is a reported RVR or for RVR less than 800 m.
According to ICAO Annex 6, Part I, we should not take off from an airport unless the weather is above the minimum required by the operator, and we should not take off or continue through the in-flight re-planning point unless the weather forecasts indicate that at the destination airport or at the alternate airport the weather conditions will be above the minimum established by the operator at the time we expect to operate at the airport..3.6
TAKEOFF ALTERNATE MINIMA
According to EASA AIR OPS we will need to select a takeoff alternate, if the meteorological conditions at the aerodrome of departure are below the operator’s established aerodrome landing minima for that operation or if it would be impossible to return to the aerodrome of departure for other reasons. 3.7
The operator will only select an aerodrome as an alternate takeoff aerodrome when the meteorological forecasts indicate that, from between one hour before to one hour after the estimated time of arrival (ETA) at the aerodrome, the meteorological conditions will be equal to or greater than the RVR or VIS specified in accordance with Aerodrome Operating Minima and for type A or a circling operation, ceiling at or above MDH. 3.8
According to Annex 6, Part I of ICAO, the available information must indicate that, in the estimated time of use, the meteorological conditions will be above the minimums required by the operator. 3.6
For aircraft with two engines, the takeoff alternate should be at a maximum distance of one hour with one engine inoperative cruising speed according to the AFM, ISA still air conditions and actual TOM, or the extended-range twin operations (ETOPS) diversion time up to a maximum of 2 hour flight time at OEI cruising speed according to the AFM, ISA and still air conditions using actual TOM. 3.8
ARRIVAL MINIMA
In order to select the destination airport, the weather forecasts will have to indicate that the RVR or visibility is above that indicated on the approach charts from one hour before to one hour after our ETA. If we expect to make a type A approach, the ceiling will have to be above the minimum descent altitude/height (MDA/H). 3.8
If these conditions are not met or if no meteorological information is available, we can still select the destination airport as long as we select two alternate airports. 3.9
AERODROME OPERATING MINIMA
Depending on the types of approach of each airport, there will be a minimum DA/H or MDA/H that will have to be met, described in the following table.
Figure 3.3.7. Arrival minima.
The final altitude DA/H or MDA/H that is established may be higher than indicated in the table.
Each DA/H or MDA/H final altitude will require visibility to complete the approach. We can find a table that indicates the visibility required for each final altitude and type of airport lighting system in the AMC 5 CAT.OP.MPA.110 on page 885, ANNEX IV of the AIR OPS. 3.10
For ILS approaches, there are several types of approaches that allow us to achieve minimums below 200 ft.
Figure 3.3.8. CAT. 3.11
It is important to note that CAT II and CAT III are LVP (Low Visibility Procedure) and that there are additional training and technical requirements. More information can be found on this on AIR OPS Annex V Part-SPA Subpart E.
In some AFM you may see CAT III referred as CAT III A, CAT III B and CAT III C. This is just the old ICAO designation.
CAT IIIA: a DH lower than 30 m (100 ft) or no DH and an RVR not less than 175 m;
CAT IIIB: a DH lower than 15 m (50 ft) or no DH and an RVR less than 175 m but not less than
50 m; and
CAT IIIC: no DH and no RVR limitations. This is not used in Europe as the minimum visibility required is 75 m.
If we plan to complete a circling approach, the following table shows us the minimum visibility/cloud ceiling required for each category of aircraft.
Figure 3.3.9. Circling minima. 3.12
ARRIVAL ALTERNATE MINIMA
According to Air OPS, all IFR flights should have an alternate aerodrome selected unless the flight time is less than 6 hours (Or in the event of replanning the remaining time does not exceed 4 hours), two separate runways are usable at our destination and the appropriate weather reports and/or weather forecasts indicate that for the period from 1 hour before to 1 hour after the expected time of arrival, the ceiling is at least 2 000 ft (600 m) or circling height + 500 ft (150 m), whichever is greater, and ground visibility is at least 5 km. 3.13
As a rule, we will have to make sure that the weather conditions outlined at the table below will be satisfied from 1 hour prior to 1 hour after our ETA.
Figure 3.3.10. Alternate airport minimas.3.14
In 2023, EASA introduced in the AIR OPS certain conditions that when met, can reduce the meteorological margins needed.
For the first scenario, the operator should utilize a suitable computerized flight-planning system and establish an operational control system that includes ongoing flight monitoring. Additionally, for flights, the duration from takeoff to landing should not exceed 6 hours, or in the case of in-flight re-planning, the remaining flying time to the destination should not exceed 4 hours. Furthermore, a minimum flight crew of two pilots is required. 3.15
Figure 3.3.11. Circling minima. 3.14
If additionally we hold an approval for low-visibility approach operations, the conditions will be the following:
Figure 3.3.12. Circling minima. 3.14
