IFR traffic in airspace E: controlled but not separated
Airspace E is a controlled airspace that is used by both VFR and IFR pilots. The term „controlled“ is often misleading. Although IFR traffic is under the control of air traffic control, there is no active separation between IFR and VFR aircraft. There is neither a radio obligation for visual aircraft nor an obligation to obtain clearance from air traffic control.
IFR aircraft in airspace E also only receive traffic information, insofar as this is available. However, pilots are solely responsible for maintaining safe distances. Even large commercial aircraft must avoid potential collisions through visual airspace observation - a fact that is problematic in view of high speeds and limited visibility.
Vertical structure and high traffic density
In Germany, airspace E generally begins at 2500 feet above ground level and extends up to flight level 100, in the Alps sometimes up to FL130. Around commercial airports, however, the lower limit is often significantly lowered, sometimes to 1700 or even 1000 feet AGL. It is precisely at these altitudes that many VFR flights take place, for example when motorised aircraft are cruising or gliders and microlights are flying cross-country.
In addition, airspace E is used by almost all categories of aircraft: slow gliders, general aviation motorised aircraft, fast turboprops and commercial aircraft climbing or descending. The permitted maximum speed of 250 knots below FL100 theoretically creates more reaction time, but still means approach speeds that make visual avoidance considerably more difficult.
When speed and visibility become a problem
A key safety problem in Airspace E is the combination of high speed and limited visibility. While pilots of smaller aircraft usually have good all-round visibility, this is significantly restricted from a commercial aircraft. Cockpit geometry, seat position and wing arrangement reduce the field of vision, especially downwards.
Situations in which IFR traffic penetrates a cloud cover while descending are particularly critical. If there is a VFR aircraft immediately below close to the cloud base, it can be practically invisible to the IFR crew - and conversely, the visual pilot has hardly any time to react. The geometric approach is often so fast that an evasive manoeuvre is no longer possible.
Cloud clearances and visibility minima as a safety barrier
The increased cloud clearances and visibility minima in airspace E are a direct consequence of these risks. Below FL100, vertical distances of 1000 feet and horizontal distances of 1.5 kilometres apply with a flight visibility of at least five kilometres. These requirements are not a formality, but represent a central safety barrier.
Gliders in particular, which fly close to the cloud base in good thermals, are effectively invisible to IFR traffic when they break through the cloud cover. Another complicating factor is that many gliders do not carry a transponder. Collision warning systems in commercial aircraft can therefore neither detect nor take account of such aircraft.
Technical limits of traffic monitoring
Air traffic control also reaches its technical limits in airspace E. Aircraft without transponders only appear on the radar as unspecific primary targets, without altitude or identification information. Under these circumstances, targeted traffic information or warnings are only possible to a limited extent.
The real risk of collision is repeatedly demonstrated by dangerous approaches, particularly in the vicinity of large commercial airports. These incidents make it clear that Airspace E is not „uncritical“ airspace, but an area with an increased risk when several factors come together unfavourably.
Avoidance rules instead of right of way
In airspace E, the general avoidance rules apply without restriction. IFR traffic has no right of way over VFR traffic. Both sides are equally obliged to avoid collisions. For IFR crews, this means explicitly including the airspace structure and possible conflict zones in the approach briefing.
Proven measures include reduced speed, consistent visual airspace observation, switching on all external lighting and a strict focus on flight-related tasks in the cockpit. Below FL100, professional crews deliberately refrain from unnecessary conversations in order to focus all their attention on the traffic outside.
Local knowledge as a decisive factor
An additional risk factor is a lack of local knowledge. Not all IFR approach charts show the surrounding airspace structure in detail. If a crew is not aware that they are outside the control zone in airspace E, this can lead to a false sense of security.
For VFR pilots, the reverse applies: even if there is no formal right of way, defensive flying is crucial. Generous avoidance, sufficient distance from approach and departure routes and early recognition of potential conflicts significantly increase safety. In addition, visual flyers should consistently switch on lights in the vicinity of commercial airports in order to be better recognised.
Transponder operation and traffic information
The continuous operation of a transponder is a key safety factor. Only in this way can collision warning systems in IFR aircraft generate warnings and avoidance recommendations in good time. Equipping with ADS-B-Out additionally increases visibility and improves the traffic situation for all parties involved.
It can also be useful to contact the flight information service. Even if there is no separation, traffic information can help to recognise critical situations at an early stage. However, the prerequisite always remains consistent compliance with the prescribed cloud clearances and visibility minima.
Airspace E in the vicinity of commercial airports
Airspace E is particularly critical where control zones are not extended laterally or upwards by class C or D airspace and no transponder mandatory zone exists. In such areas, IFR approach and departure traffic and VFR cross-country traffic meet directly.
It is precisely here that airspace E requires increased attention and discipline. Those who are aware of its special features and fly defensively reduce the risk significantly. Those who regard it as „uncomplicated“, on the other hand, quickly find themselves in situations where seconds can make the difference between safety and danger.
Source references:
Aviation magazine
