When Low Visibility Procedures are activated
The new DFS regulation applies to Berlin Brandenburg, Bremen, Dresden, Düsseldorf, Erfurt-Weimar, Frankfurt, Hamburg, Hanover, Cologne/Bonn, Leipzig/Halle, Munich, Münster/Osnabrück, Nuremberg, Saarbrücken and Stuttgart.
Low Visibility Operations generally refer to approach and takeoff procedures at a visual range of less than 550 meters, approaches with an altitude decision below 200 feet, and roll movements at RVR below 550 meters. However, the DFS activates its Low Visibility Procedures earlier: at the aforementioned airports, they are usually applied from an RVR of 600 meters or less, or at a major cloud base or vertical visibility below 200 feet. The preparation phase even begins at RVR of 1,000 meters or less, or at a cloud base or vertical visibility of 300 feet or less.
During actual LVP, runway and taxiway lighting lines are activated, among other things. At the same time, personnel and vehicles on the runway are reduced to the minimum necessary. The goal is not only to prevent Runway Incursions in poor visibility but also to protect navigation signals required for precision landings from interference.
Pilots recognize active operation by the ATIS message „LOW VISIBILITY PROCEDURES IN OPERATION, CAT II AND III AVAILABLE“. LVTO procedures are then generally also available, provided that no restrictions are published or communicated.
Why aircraft can interfere with the ILS signal
For pilots, the protection of the ILS is one of the most interesting parts of the announcement. An Instrument Landing System is by no means immune to external influences. Large metallic objects such as aircraft or vehicles can reflect the emitted signals and thereby distort the locator in particular.
Therefore, there are so-called Critical and Sensitive Areas around the antennas. The Critical Area is located directly around the facility and is generally kept free during an ILS approach. The larger Sensitive Area is protected especially for CAT-II and CAT-III operations.
At visibility below 1,500 meters or a cloud ceiling, or vertical visibility below 400 feet, ATC also ensures that other aircraft and vehicles no longer interfere with the ILS signal as soon as an aircraft approaches within two nautical miles of the runway threshold.
An allowable exception is interesting: a just landed aircraft may briefly roll through the Critical Area of the locator at appropriately regulated airports. The following approach will then be warned with „EXPECT SHORT-TIME ILS INTERFERENCE“. The aircraft rolling in must leave the area without delay and may not stop there. In the case of active Low Visibility Procedures, the Critical Area must be free no later than when the next approach is still four nautical miles from the point of impact. Otherwise, a missed approach will be advised.
Autoland is not the same as Autoland
For pilots of modern GA aircraft with automatic landing capability, the new notice contains an important clarification. An ILS signal is only fully suitable for autoland when either CAT-III low-visibility procedures are active and there are no corresponding technical restrictions, or ATC, upon request, explicitly provides a protected CAT-III ILS signal.
In the case of exclusive CAT-II operation, the situation is different. The DFS explicitly states that the quality of the ILS signal is not guaranteed to be sufficient for automatic landing from the CAT-II decision height onwards. Therefore, signal interference can occur below the Decision Height.
This does not mean that Autoland would be fundamentally prohibited with a CAT-I or CAT-II signal. Whether this is permissible depends on the aircraft, the AFM, the approval, and the respective operational rules. However, the pilot must take into account that ATC and the airport may not protect the ILS signal under these conditions in the same way as with CAT III.
This point is also relevant in good weather. Pilots can, for example, request a CAT-II or CAT-III signal for training or safety purposes, even though no Low Visibility Procedures are active. The ATC then checks whether signal monitoring, ILS protection zones, and the required spacing can be ensured. If this is not possible, the pilot receives the information „ILS SIGNAL REMAINS CAT I ONLY“.
If a CAT-III signal is required for safety reasons, for example for an automatic landing due to the pilot’s inability to act, ATC should be informed of this as early as possible.
Guided takeoff up to 75 meters RVR
Another focus is the so-called Guided Take-off. In this method, the takeoff run is not controlled exclusively by visible reference points. Instead, the crew uses additional instrument guidance, such as the signal from the ILS-Localizer.
The procedure is intended for extremely low visibility: RVR of no more than 125 meters, but not less than 75 meters is required. The aircraft and crew must be appropriately certified or qualified for this.
The availability is explicitly announced on the ATIS as „CAT III AND GUIDED TAKE-OFF AVAILABLE“. Among other requirements, all RVR measurement values must be available; at least one of them must be at 125, 100, or 75 meters; the value must not be less than 75 meters; and there must be no relevant ILS interference.
The localizer signal is also particularly protected in this system. A subsequent aircraft may only begin its takeoff run if the aircraft that has taken off has flown 1,500 feet AGL or has left certain areas around the localizer. Guided takeoff with GBAS support is currently not permitted under German regulations.
For typical privately operated GA aircraft, this operating mode will hardly play a practical role. However, it illustrates the additional infrastructure and signal quality required when an aircraft cannot be guided along the runway visually alone at extremely low visibility.
Rolls at very low visibility
Another interesting rule concerns the roll. If the RVR falls to 300 meters or less in any area of the flight path, so-called Level 3 procedures are applied in reduced visual flight conditions.
The air traffic control then generally ensures a minimum of 150 meters of longitudinal distance between aircraft or vehicles on runways. For this purpose, depending on the airport, ground radar, sensor loops, follow-me vehicles, illuminated intermediate stop positions, or a spatial separation of movements are used.
The guardrails are of particular importance. A switched-on stop bar must not be rolled over in principle – even if verbal permission to continue rolling appears to authorize it. If a guardrail remains switched on against the permission, the pilot must stop and inform ATC. If the guardrail cannot be technically switched off, it may only be crossed after the procedure provided for, possibly under the guidance of a lead vehicle.
Especially in poor visibility, the red light strip on the roll-out bar serves as an independent safety barrier against runway incursions.
Technical failures can change the category of the flight.
The notice contains detailed tables showing which technical malfunctions lead to a downgrade of an approach procedure.
For example, if the backup transmitter fails on a CAT-III ILS, the system can be downgraded to CAT II. If a CAT II/III critical area cannot be adequately protected, a downgrade to CAT I may be required. In the event of a complete failure of the localizer or glideslope, a different available instrument approach procedure must be used.
RVR, wind and power supply systems also play a role. For example, if all runway lighting is lost during takeoff and landing, CAT I is reduced to nighttime operations; at night, the runway can be closed.
Important for pilots: Not every failure of a ground facility automatically leads to a formal downgrade by ATC. Even if the published category of approach remains in effect, the crew must assess, based on their own operational and licensing requirements, whether the approach is still permissible and whether their own minimum requirements need to be adjusted.
ATC minima and pilot minima are not the same thing
Another point is explicitly clarified in the new NfL: ATC may initiate or authorize an ILS approach regardless of whether the individual wet landing criteria of the pilot or aircraft are met.
Whether it is actually allowed to continue flying until landing is up to the responsibility of the pilot or operator. The airport's available procedures only form the infrastructure side.
Especially in general aviation, this separation is important. An airport can offer CAT III, while aircraft or pilots are only approved for CAT I. Conversely, a CAT-I approval does not guarantee that every automated landing function of the aircraft can be used without restriction until it is deployed.
Conclusion
The DFS regulation, which will be in effect from November 26, 2026, will bring fewer fundamental changes to IFR flying for pilots than a major clarification of procedures in low visibility.
The clear distinction between the approach category and the actually protected quality of the ILS signal is particularly relevant. Anyone who uses Autoland should be aware that a CAT-I or CAT-II ILS is not automatically protected against signal interference until it is activated. This quality is fundamentally not fully guaranteed unless appropriate CAT-III operation is in place or an explicitly provided CAT-III signal is provided by ATC.
Likewise important remain the simple ground rules: in low visibility, larger roll distances apply, ILS protection zones are consistently maintained, and a switched on hold bar means stop – regardless of what the pilot expects based on a previous roll clearance.
The new NfL makes one thing clear above all: In low visibility operations, safety depends not only on modern avionics on the aircraft, but also on the precise coordination between the pilot, air traffic control, airport infrastructure, and the protected navigation signals on the ground.
Source references:
NFL
