27th February 2024

Circuit traffic conflict

Initial Report

I was leading a formation of aircraft from [Airfield 1] to [Airfield 2] in order to participate in an event day. We had planned an 0830Z departure but, as is often the case on a summer morning, there was patchy fog and low cloud first thing in the morning, which delayed departure. This added a little time pressure for the transit itself, but our preparation and pre-flight formation briefing for the transit was conducted in a thorough and unrushed manner.

I had planned an East-West routing [in constrained airspace] and my route took us through a portion of [Airfield 3] ATZ. Transiting at 1300ft due to the remaining low cloud, I called [Airfield 3] just over 5mins from the ATZ, was passed airfield information and told to keep a good lookout because they were very busy. I called on entering the ATZ, continuing to keep a good lookout. As we neared the western edge of the ATZ I was preparing to call that we were clear, (and thinking that we were well clear of the circuit), when I spotted an aircraft ahead, passing right-to-left at the same height. I turned the formation slightly right to pass behind, only to realise that there was a further aircraft passing right-to-left behind the first one. That aircraft passed behind us. It was only at that point that I realised that rather than being clear of what I thought was a RH circuit on the runway in use, we had actually flown through the circuit pattern for a LH circuit.

Overall, this was a fall-down in my TEM (Threat and Error Management) for the flight. I had briefed the low but improving cloud base enroute as a threat which could channel transiting aircraft to similar heights, but had failed to appreciate the specific threat around [Airfield 3]. This is a route that I have used many times before, but have usually found the airfield to be quiet for an ATZ transit at that time of day, even at the height in question. I should have planned a slightly more southerly route to remain clear of the ATZ and circuit pattern – significantly more southern routings, well away from the ATZ, are often not viable due to extensive built up areas.  I also did not build a clear mental picture of the likely traffic within the ATZ, and mis-appreciated both the circuit direction and that fact that the circuit for the runway in use that day runs very close to the ATZ boundary. I also should have used the comment from the A/G operator regarding current business and circuit height as a prompt to amend my plan and to remain clear.

The main two factors here were complacency, having used this route many times previously with no issue, and awareness, in that I had failed to build a correct mental picture of the threat and the circuit pattern.

CHIRP Comment

CHIRP commends the pilot for their altruistic self-critical comments which represent the finest traditions of an honest debrief that will hopefully provide food for thought for others – this report is a fine example of a frank and honest description of an event that we can all learn from. The reporter has covered the main lessons to be learnt themselves, although it’s not clear whether the A/G operator had reported the circuit direction and they missed it or whether they had simply said that the circuit was busy. Either way, as the reporter comments, it would have been better to have routed further from the airfield if possible because aircraft using the airfield would have been operating under the expectation that the ATZ was theirs to use as they needed. That being said, one might hope that the A/G operator would have broadcast to those in the circuit that a formation was transiting the ATZ so that they could also make allowances in their pattern if possible to accommodate the sometimes unwieldy nature of formation routing, especially since the circuit pattern also extended close to the ATZ boundary at the airfield concerned.

We also commend the reporter for actively taking time to consider TEM before the flight. Although they’re pretty hard on themselves for not fully appreciating the threat that the ATZ represented in the conditions at the time, it’s clear that they had at least thought about it and had taken some steps to mitigate the risks. The strength of TEM is that it arms you with pre-planned options so that you not only avoid unnecessary risks where possible but you’re also not overtaken by events when things might start to go wrong, therefore increasing your capacity to act.

Key Issues relating to this report

Dirty Dozen Human Factors

The following ‘Dirty Dozen’ Human Factors elements were a key part of the CHIRP discussions about this report and are intended to provide food for thought when considering aspects that might be pertinent in similar circumstances.

Pressure – additional responsibilities as a formation leader.

Awareness – circuit direction not assimilated or sought.

Communication – did not communicate/assimilate the circuit direction and potential for conflict.

Complacency – assumption that the circuit was in the other direction as previously experienced.

  • Awareness
  • Communication
  • Complacency
  • Pressure

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