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Maximum Danger in the Circuit

Risk / Threat Assessment and Management (in the Circuit)

Other than crashing just after take-off, in an unsuitable area, what is the greatest threat to you and your aircraft when flying in the circuit? Have you considered this risk and has your instructor ever mentioned this during your briefings?

I run a flight school at an uncontrolled grass strip in the southeast of England, surrounded by several busy airports with their patches of controlled airspace. Imagine a narrow corridor of open airspace between 4 major airports, with a motorway and a river and a large well-known bridge, which is used as a VRP and a line feature by pilots wishing to avoid the controlled airspaces. Now imagine my home airfield placed in the vicinity, but not marked by an Aerodrome Traffic Zone with its 2 mile radius of blue dots.

Our usual arrival procedure is for inbound aircraft to join overhead at 1400 feet on the QNH of the nearby commercial airport to stay below its CTA. On a good flying day, with CAVOK conditions, I see many scores of aircraft pass overhead our field at a safe height and distance without causing noise nuisance and without affecting our arrivals or departures or circuit traffic.

Lets come back to my question of which is the greatest threat when flying in the circuit. Along with this question, a pilot might not have considered some errors she might make and how she might manage these errors, thus further increasing the dangers.

A good briefing for circuit training will include the flying aspects, the orientation of the circuit, weather conditions, emergency situations on the ground and in the air, personal physical fitness and fatigue during multiple take offs and landings which require intense concentration from the student and instructor.

Consider the circuit orientation; when flying a left hand circuit, the (student) pilot’s vision will be greatly obscured by the left wing when turning left. In a right hand circuit, the pilots vision is obscured by the right wing and by the space occupied by the occupant in the right seat, causing loss of sight of the runway, especially when turning from down-wind on to base leg.

Weather may deteriorate in terms of visibility and turbulence, so consideration must be given to options of concluding the flight before the onset of poor weather or diverting to a safer airfield to avoid poor weather.

Emergency situations on the ground are generally easier to manage than emergencies in the air. I consider an engine stoppage with no fire the easiest emergency to manage in the circuit because the only choice we have is to land back on the runway. The variations on the theme of this kind of an emergency can add many scenarios, which may make the emergency into a disaster; but that is not the point of this article.

Personal fatigue for the pilot can be a serious threat due to the concentration and accuracy required to execute a good landing. It is important to land before the onset of fatigue, which may force the pilot to make poor judgement calls and poor handling resulting in a poor landing.

When flying the circuit at an uncontrolled airfield, the biggest danger, in my opinion, is mid-air collision. The (student) pilot workload is high. One may be joining the circuit at an unfamiliar airfield. Or we may be in the circuit with many other aircraft of various speeds and have to manage distance and time separation from aircraft in front of us to avoid wake turbulence and to keep sufficient distance behind to allow the aircraft in front to reduce speed to land and vacate the runway before we land.

Now imagine that the cloud base is just above circuit height, but visibility is good and the air is smooth. It is a weekend and every one is out to enjoy flying on the only good day of the week so far.

We have a pilot aware unit “senses” other transponder-equipped aircraft if it’s antenna can see the other transponder antenna. But this does not preclude the pilot from keeping a very good look out for other traffic.

In this instance, I was in the circuit, with a student who was concentrating on flying an accurate circuit. We were at 1000 feet AAL about 200 feet below the cloud base. I was keeping a very good lookout. When flying, one cannot hear another flying machine zoom overhead about 50 feet to 100 feet. I caught sight of the helicopter just as it passed overhead us. We did not feel the anticipated downwash, probably because it was flying faster than our own speed of 90 knots. My student did not see it when I pointed it out, due to his concentration on the circuit tasks he was practising and the helicopter whizzed into the clouds and disappeared.

On the second training sortie the same day, with the same cloud base at 1200 feet AAL, I was more aware of the risk of a near miss or potential mid air collision. Guess what, there was another near miss. This time with a low wing aircraft flying along the motorway, at 1000 feet AAL, same as our circuit height. His low wing and our high wing meant that we were in each other’s blind spots. Fortunately it was a near miss and not a collision.

What was the error I made during the second circuit-training sortie? I kept to our normal circuit height despite having had a near miss with the helicopter that was staying in VMC below cloud base just as we were. On the second sortie I should have made our circuit height 500’ due to cloud base at 1200 feet, with the knowledge that other aircraft would probably fly over our circuit pattern at just below cloud base, as it is open airspace.

Well, I am pleased to say I live to fly another day with a lesson learnt about “Risk / Threat Assessment and Error Management”.

Deepak Mahajan


London Airsports Centre


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