The full set of infringement occurrence narratives is included on this page: Infringement occurrences

Infringement of the Class A London Terminal Control Area

Date 19 June 2020
Aircraft Category Fixed-wing SEP
Type of Flight Recreational
Airspace / Class LTMA / Class A

Met information

  • METAR EGLL 191450Z AUTO 21014KT 9999 SCT033 SCT039 BKN046 19/11 Q1015 NOSIG=

Air traffic control

The Air Traffic Controller (Farnborough LARS West) reported providing air traffic services to five aircraft with a low to medium workload. The controller noticed an Airspace Infringement Warning (AIW) alert activate 3NM east of Wycombe Air Park/Booker aerodrome (Figure 1).

The AIW was associated with an aircraft squawking the Farnborough Frequency Monitoring Code (FMC) of 4572 indicating 3,300 feet where the base of the London Terminal Control Area (LTMA) is 2,500 feet (Figure 2).

The controller called the pilot who immediately replied. The pilot was then advised that the base of controlled airspace in their location was 2,500 feet. The pilot replied staying that they were descending.  At the same time the Heathrow Special VFR controller called the Farnborough West controller to alert them of the event and was told that the subject aircraft was descending. On leaving controlled airspace, the controller obtained a level check from the pilot and verified that the aircraft’s MODE C was accurate.

Chart showing where the AIW alert activated, east of Wycombe Air Park/Booker aerodrome

Figure 1 An AIW alert activated east of Wycombe Air Park/Booker aerodrome


Chart showing that the base of the London Terminal Control Area (LTMA) is 2,500 feet

Figure 2 The base of the London Terminal Control Area (LTMA) is 2,500 feet


The pilot reported that they had planned a VFR cross country flight from Dunkeswell aerodrome in Devon to Earl’s Colne in Essex. It was the pilot’s first lengthy cross-country flight since the UK had entered the first COVID-19 lockdown in March 2020. The weather was reported as CAVOK and the route planned to be flown was:

  • Dunkeswell – Frome – Welford Discussed aerodrome – overhead Wycombe Air Park/Booker aerodrome  – overhead Elstree aerodrome – LAM/ overhead Stapleford aerodrome – west of Chelmsford VRP – Earl’s Colne aerodrome (Figure 3).

The route had been planned on a VFR moving map to route to the north of the London CTR/TMZ and was one that the pilot had flown many times.

Chart showing the planned route

Figure 3 The planned VFR route

As the weather conditions were good the pilot wanted to fly as high as possible to maximise the views from the cockpit.  They flew at 2,500 feet until Welsford (7NM southwest of the Compton VOR (CPT)) when they commenced a gradual climb to 3,300 feet, reaching that altitude overhead Wycombe Air Park/Booker aerodrome.  The pilot commented that when using their VFR moving map, there were so many different alerts, most of which they felt were unnecessary, which led to them to habitually cancelling the warnings.

The pilot also stated that they used a personally prepared Flight Preparation checklist comprising five sections:

  1. Departure airfield;
  2. Arrival airfield;
  3. En-route;
  4. Flight plan (VFR only); and
  5. Survival/equipment.

In that list, “Altitudes” was included in the En-Route section only.  After the occurrence, the pilot has added “Planned Altitudes” item to the “Flight Plan” (VFR Only) section. A copy of the checklist used at the time of the occurrence is at Table 1.

In addition, as soon as they were made aware of the occurrence, they submitted a detailed report and carried out effective post-flight analysis which resulted in revisions being made to their own check list to mitigate the risk of a recurrence.

Copy of the pilot's flight preparation checklist

Table 1 Flight preparation checklist

Findings and Causal Factors

The pilot had formulated a sound primary plan relating to the route. However, insufficient consideration was given to the vertical portion of the route. The pilot’s own admission was that the planning of the flight was rushed and therefore incomplete. An essential aspect of planning is incorporating effective Threat and Error Management.

When planning it is good practice to break down the route into sectors/segments between waypoints. One of the threats which will affect many flights is airspace, whether that be controlled airspace, ATZ, TMZ /RMZ, restricted or prohibited airspace, danger areas, glider sites, parachute sites or minor aerodromes.

A threat that frequently emerges when using VFR moving maps and ‘rubber-banding’ the route between waypoints is that detailed analysis of what lies between the waypoints can be easily missed. By reviewing each sector/segment in detail, you can assess the lateral route and then plan for the maximum altitude to be flown (the lower limit of vertical controlled airspace less 200 feet if possible as part of Take 2) along with minimum safe altitudes.

If using a paper chart, it is good practice to write the maximum planned altitude alongside the MSA calculation or annotate it on your PLOG. If the route is too complex, or unachievable vertically, you may need to consider changing the track. Once those sectors/segments are finalised, it is then a good idea to insert additional waypoints along the route to indicate points at which a descent or climb can commence, in order to pass under a CTA or perhaps under lowering ‘steps’ in a TMA,  or where  it is possible to climb higher as the CTA/TMA ‘steps up’; remember to incorporate the Take 2 guidance into these points.

In addition, as the pilot had flown the route “many times”, there may have been an element of inadvertent complacency leading to a loss of situational awareness. The human factor of complacency has been equated with over confidence, a state of confidence plus contentment, low index of suspicion and unjustified assumption of satisfactory system state. In addition, when using a VFR moving map as the sole source of navigation, the pilot in essence becomes a system monitor.  In 1998 Dr Tony Kern (author of books on human performance, including the ‘Plane of Excellence’ and the trilogy of ‘Redefining Airmanship’, ‘Flight Discipline’, and ‘Darker Shades of Blue’) explained that ‘‘as pilots perform duties as system monitors they will be lulled into complacency and lose situational awareness”. This may be categorised as automation-induced complacency.

Another threat that was not managed in this occurrence was the pilot’s incomplete reaction to the aural and visual alerts that the VFR moving map was providing.  In many airspace infringements where the pilot was using a VFR moving map they had succumbed to alert fatigue.

The pilot commented that along the route “combine all the different alerts received on [the  moving map] (sic), most of them are perhaps a little too sensitive, resulting in multiple warnings that are unnecessary, leading to a habitual cancelling of the warning.” A typical human reaction is to think “yes I know that” or “that does not apply to me” with many of the alerts. The more frequent that happens, the rapid ‘cancellation’ of an alert takes place to ‘clean-up’ the display; inevitably, the one alert that was needed to break the chain alerting to the LTMA controlled airspace ahead was missed. This is an example of a gradual process by which the unacceptable becomes acceptable in the absence of adverse consequences; this is known as normalisation of deviance.

Post-flight analysis comment

This is another example of an airspace infringement occurring due to lapses in effective planning and ineffective use of a VFR moving map. A number of Human Factors and Threats and Errors led to this event. They always exist, often in the latent form, but they have the potential to emerge and develop into an incident or accident.

In this occurrence, the pilot is to be commended for their use of a VFR moving map and a Frequency Monitoring Code (FMC). The pilot decided, based on the prevailing meteorological conditions, that an air traffic service was not required. But by using an FMC the pilot enabled the expedient  resolution of the occurrence to which they too responded promptly.

ANSPs with an FMC encourage pilots to ensure the appropriate codes are displayed with the correct frequency monitored when an air traffic service is not required within the  published geographical area.

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The full set of infringement occurrence narratives is included on this page: Infringement occurrences 

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