Class E Airspace is the lowest class of controlled airspace. Controlled doesn’t mean visual flight rules (VFR) traffic has to be in radio contact with air traffic control (ATC), but that ATC services are available within the capabilities of radar and radio equipment. Instrument flight rules (IFR) traffic is required to contact ATC for a clearance. This is general-purpose airspace and aircraft flying under VFR can fly more-or-less wherever they want (weather permitting) and IFR traffic operates under positive control by ATC. There are regulations in this airspace but they aren’t onerous, and they’re designed to accommodate the variety of aircraft and activities that can be found here. Although Class E airspace is a single class of airspace, there are tighter regulations above 10,000 feet, where there are no airspeed restrictions (other than the prohibition on supersonic flight over land) compared to lower altitudes where airspeeds are limited to 250 knots.

1.1.  This paper was requested by Germany at the 2015 Conference in Sofia. The purpose of this paper is to look at Class E Airspace: who is responsible for separation and what would the legal implications be in the event of an incident or accident that occurred in Class E Airspace.

1.2.  Airspace is an area of aeronautical knowledge that is commonly poorly demonstrated in practical tests. Even when pupil pilots demonstrate knowledge of the airspace system that meets the minimum standard necessary for issuance of a pilot certificate or rating, it is usually clear that this knowledge level has been achieved by simple memorisation without understanding the underlying concepts.

1.3.  Consequently, it is not surprising that pilots, especially those flying recreational, are often found to be confused about this subject. This observation is supported by the fact that airspace violations remain a major cause of actions taken against offending members of the general aviation community.

2.1. IFATCA Policy

2.1.1. According to the IFATCA Technical & Professional Manual (2015), in 1991 in an attempt to harmonise the categories of airspace, ICAO re-classified the airspace offering seven different types. Since then, no review has taken place with regard to whether this re-classification has created a harmonised situation. There is now evidence to suggest, that there is a lack of harmonisation between neighbouring countries, and that there exists a degree of under and over classification.

2.1.2. IFATCA policy is:

2.2. The ICAO Airspace Classification System

2.2.1.  According to International Civil Aviation Committee Study Guide (2015), on March 12 1990, ICAO adopted the current airspace classification scheme. The classes are fundamentally defined in terms of flight rules and interactions between aircraft and ATC. Generally speaking, the ICAO airspaces allocate the responsibility for avoiding other aircraft, either to ATC or to the aircraft commander.

2.2.2.  The ICAO Airspace Classification System (ICAO Annex 11 to the Convention on International Civil Aviation, Thirteenth Edition July 2001 – “Air Traffic Services” Chapter 2 page 2-4) consists of seven classes of airspace, each specifying minimum Air Traffic Service requirements and the services provided. Classes A, B, C, D & E are Controlled Airspace whilst Classes F & G Airspace is Uncontrolled Airspace.

2.2.3.  In Class E Airspace IFR and VFR flights are permitted, IFR flights are provided with air traffic control service and are separated from other IFR flights. All flights receive traffic information as far as is practical. Class E Airspace shall not be used for control zones.

2.2.4. Where the ATS airspaces adjoin vertically, i.e. one above the other, flights at a common level would comply with requirements of, and be given services applicable to, the less restrictive class of airspace. In applying these criteria, Class B airspace is therefore considered less restrictive than Class A airspace; Class C airspace less restrictive than Class B airspace, etc.

2.3. Separation of Traffic in Class E Airspace

2.6. Weather Minima Practical Example FAA

2.6.1. Consider the aircraft executing the instrument approach in Figure 1. Class E Airspace rules provide separation when it emerges from the cloud at area 1. As the aircraft nears the vicinity of the airport, the floor of Class E Airspace is lowered so that separation protection is maintained when it flies out of the cloud at area 2. If the instrument approach being flown is a non-precision approach, this is the approximate minimum descent altitude. If the aircraft is established on a precision instrument approach (which usually terminates at an altitude of approximately 200 feet AGL), then Class E Airspace is extended to the surface so that the flight is protected when it emerges from the cloud at area 3. The dimensions of the Control Zone, where Class E Airspace exists at the surface, (this is not ICAO compliant) is a 5 statute mile radius from the center of the airport, and vertically from the surface to 14,500 feet MSL. VFR flight within this Control Zone requires, in addition to the normal Class E visibility and cloud clearances, a minimum ceiling of 1,000 feet (ceilings are always expressed in AGL).

2.6.2.  At an altitude of 10,000 feet MSL, there is a fundamental change in airspace rules that necessitates a shift in Class E and Class G airspace visibilities and cloud clearances. Below 10,000 feet MSL, a speed limit of 250 knots is imposed on all aircraft flying in that airspace. Above 10,000 feet MSL, pilots of all aircraft are allowed to operate at any subsonic speed. Since high-performance IFR aircraft are emerging from clouds at much higher airspeeds (Figure 1, area 6), Class E required inflight visibility is increased to 5 statute miles, and cloud clearances are increased to 1000 feet above and below clouds and 1 statute mile horizontally. (Class G visibility and cloud clearances are also increased, although no IFR aircraft should normally be operating in this airspace.)

2.6.3.  The red shaded area (4) represents the Transition Zone and encloses an area in which Class G Airspace extends from the surface up to 700 feet AGL. (Note that transitions zones may contain extensions to accommodate the requirements of instrument approach procedures.) Outside the shaded magenta line, area (5), Class G Airspace extends from the surface to 1,200 feet AGL. Area (3), which is enclosed by a dashed magenta line, depicts Class E airspace that extends all the way to the surface. The presence of this dashed magenta line, formerly called a Control Zone, indicates that this airport offers a precision instrument approach, which normally provides IFR separation down to 200 feet AGL.

2.6.4.  Most general aviation airports offer only non-precision instrument approaches. These approaches only allow IFR aircraft to descend to minimum descent altitude that is approximately the same as the top of the transition zone.

2.6.5.  In summary, Class E Airspace rules are more restrictive that those that govern Class G Airspace, but only in terms of required minimum visibilities and cloud clearances necessary to accommodate the separation of IFR and VFR aircraft. There is still no requirement for electronic communication or navigation equipment or its use. The only requirement of this type is the requirement of an altitude- encoding transponder for flight above 20,000 feet MSL.

2.7. What is an airspace infringement?

2.7.1. A flight into a notified airspace that has not been subject to approval by the designated controlling authority of that airspace in accordance with international and national regulations. Such airspace is considered to be:

Controlled airspace, including ICAO airspace classes A to E.

Note: VFR traffic cannot infringe Class E airspace because under ICAO rules neither an ATC clearance nor a radio communication is required to enter or operate within it, unless filed national differences call for one or the other (or both). IFR traffic can infringe Class E airspace when not in receipt of a clearance to enter it.

2.8. Class of Airspace and Air Crew Awareness Limits

2.9.2.  Another aspect of eye functioning that is relevant to visual searching is saccadic eye movement. When they are not tracking a moving target, the eyes do not shift smoothly, they shift in a series of jerky movements or “jumps” called saccades (Figure 2). As a result of saccadic eye movements, it is not possible to make voluntary, smooth eye movements while scanning featureless space.

2.9.3.  Visual acuity is greatest for objects that are directly in front of the eye. But the fovea is a mere two degrees wide, which results in a very narrow high-acuity detection area and leaves as much as 178 degrees of the detection area in the realm of peripheral vision. This is one reason that we often tend to spot traffic or obstacles out of the “corner” of our eye.

2.9.6.  The shaded areas in Figure 4 depict how the visual-detection lobe relates to saccadic eye-movement scans. Compared to near searches, distant searches using central vision must be scanned over a much larger field in a relatively short period of time.

2.9.7.  In Figure 4, the same type of aircraft is shown in the three positions – A, B and C. Aircraft A, in the central field of vision, is likely to be detected. Aircraft B, although it is at the same range as Aircraft A, is outside the visual-detection lobe and unlikely to be detected. Aircraft C is the same number of degrees off the direct line of vision as Aircraft B, but because it is within the visual-detection lobe, it is likely to be detected through peripheral vision.

2.9.8.  Depending on closure rate, crossing angle and routine cockpit distractions, aircraft can seem to appear suddenly, leaving little time to react and avoid a collision.

3.1.  The current ICAO airspace classification scheme was adopted in 1990.

3.2.  No concrete evidence could be found to suggest that there is a lack of harmonisation between neighbouring countries or that there is a degree of over and under classification.

3.3.  IFATCA policy is incorrect stating that Class E airspace is uncontrolled, it is controlled airspace for IFR traffic and uncontrolled for VFR.

3.4.  The ICAO rules pertaining to Class E airspace are clear. As long as ATCO’s comply with these rules the liabilities and responsibilities for separation between IFR and VFR traffic should fall to the pilot in VMC. ATCO’s are not encouraged to give radar headings to IFR traffic to avoid VFR traffic but rather give traffic information, as there might be other VFR traffic in the area that is not known to the ATCO.

4.1.  It is recommended that; IFATCA policy is:

ATS Authorities are urged to co-ordinate and harmonise with all neighbouring states their national airspace classification to permit safe and efficient operating conditions to all airspace users and air traffic controllers. Airspace classification should be appropriate for the traffic operating in the airspace, to avoid over and under classification. As traffic situations change, the classification may have to change accordingly.

With regard to the ICAO classification of airspace, the definition of controlled airspace is the generic term which covers airspaces of class A, B, C and D. Classes E, F and G being uncontrolled. Class E is a special case of uncontrolled airspace in which a limited Separation service will be provided between defined aircraft.

4.2 Be amended to read:

MA’s shall urge ATS Authorities to co-ordinate and harmonise with all neighbouring states their national airspace classification, in accordance with ICAO Annex 11 Appendix 4, to permit safe and efficient operating conditions to all airspace users and air traffic controllers. Airspace classification should be appropriate for the traffic operating in the airspace, to avoid over and under classification. As traffic situations change, the classification may have to change accordingly. Local operational controllers should be involved in the airspace classification process.

and is included in the IFATCA Technical and Professional Manual, ATS3.3 Harmonisation of the airspace classification, Page 3.2.3.4.

Guide to Visual Flight Rules (VFR) in the UK

Airspace Infringements – Background Statistics

Airspace Infringement Risk Airline operators – Airspace Infringement Safety Initiative Workshop – January 2008 – Eurocontrol, HQ, Brussels.

https://www.skybrary.aero/index.php/See_and_Avoid

https://www.westwingsinc.com/AIRSPACE_EXPLAINED.pdf

Flight Safety Digest – Collision Avoidance must go beyond “See and Avoid” to “Search and Detect” – May 1997

Report no F-VG990212 and F-XB990212 concerning the mid-air collision which occurred on 12 February 1999 at Gorniès between an Airbus A320 and a Grob 103 C glider.

International Civil Aviation Committee Study Guide – 2015