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Independent Parallel New Departures Procedures

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"New rules and procedures...no matter how well-intentioned they might be, too often constrain the adaptive powers of the people interacting and do not necessarily enhance safety." Image: Christian Schnettelker CC BY 2.0

“Stick to the procedures“, “Use standard phraseology“, “Maintain situational awareness“, “Avoid complacency”. Phrases such as these are the watchwords for many managers, including a lot of safety managers in the aviation industry and especially in air traffic control. The implication is that the system is basically safe if everybody behaves and acts accordingly.

As a sharp-end operator in the approach control for one of the busiest airports in Continental Europe (Frankfurt Approach Control) I find this disturbing. It is as if I would go to work every day carelessly undermining the system. Needless to say the opposite is true. I try to deliver the best performance every day, for the good of the system and my own job satisfaction.

Managing heavy air traffic in a dynamic environment can be very fulfilling. One source of this satisfaction is my discretionary space – my room for manoeuvre. To successfully cope with daily challenges, my room for manoeuvre needs to be as large as possible. Only then can I balance efficiency and thoroughness well (trade-offs) and handle traffic in a safe, orderly and fluent way.

Don’t confuse this with ‘whatever-ism’. There are some basic principles, which must never be abandoned. But not everything can be or needs to be ruled right down to the last detail. This approach can have unintended consequences.

Unfortunately this is what happens in the aftermath of a serious incident. Even though the incident might never reoccur because of the uniqueness of the circumstances that contributed to the situation, new rules are implemented to prevent ‘reoccurence’. This is the find-and-fix approach, and it is often implemented in haste.

Whether such rules serve to reassure the public or the management (“We did something”), or if they really do serve safety, is hard to tell. But since the “hastened stroke often goes astray” such quick fixes often curtail the performance and reduce flexibility (performance variability) rather than enhance the system.

The ‘independent parallel new departures procedures’ at Frankfurt Airport is a good example of this. Together with the new runway, the procedures were introduced to ensure the capacity of the two departure runways (25C and 18), which are interdependent with the landing runway 25L. Although the procedures were heavily criticised by many controllers (field experts) from the beginning, the safety assessment concluded that the procedures were basically safe if a VOR were constructed for a certain standard instrument departure (SID) route.

It didn’t take long until a serious incident occurred between a missed approach on RWY25L and a Departure on RWY25C, the latter of which turned exactly (and as designed) into the flight path of the Missed Approach Procedure. Work-as-done did not turn out as imagined, but was as designed.

Eventually, the independent parallel new departures procedures were withdrawn. For the original problem, this a reasonable decision (local rationality), but now created more serious problems. Departure capacity was decreased by the withdrawal of the procedures and a night curfew still existed. The tower controllers now faced the problem to bring all aircraft into the air in a shorter period of time, namely in the final 90 minutes before the airport closes for the night, due to restriction and noise abatement. This demand created pressure. On the departure radar side, this felt like the air being released of a balloon, and we had some “Close-Calls” because of this depletion.

Frequently, new rules are introduced for political or environmental reasons, like noise abatement. After the opening of the new runway at Frankfurt Airport, the public outcry because of the aircraft noise was tremendous. There is a goal conflict between noise and safety, but the pressure from the system environment was on reducing noise.

During the last 12 month, many procedures have been implemented to mitigate the situation and to calm down the public, without necessarily reducing noise. These procedures (resources) actually act as constraints – they constrain my handling of the traffic but, at the same time, capacity must not be reduced. This seemingly simple example illustrates the complexity of the system; procedures to avoid noise over certain areas or during certain times of day had interactions with other parts of the system and affected the flows of work. Ultimately, unexpected phenomena observed later (emergence).

At the sharp end, this dilemma can only be dissolved by removing some constraints and looking for new ‘freedoms’. These freedoms could be more time to evaluate the situation, new workarounds, etc. Here is an example how that works: When I send an aircraft on final to the Tower by using standard phraseology, “Lufthansa A/C one two tree contact Tower on one one niner decimal niner”, this takes including the pilot’s read-back about 8-10 seconds. When I use a much shorter but equally understandable phrase, “DLH A/C one two tree Tower nineteen nine”, I save 2-4 seconds. This does not seem to be much. But if you take into account that there are about 60 aircraft per hour during an average inbound rush this adds up to 2-4 minutes – a lot of time for a thorough traffic analysis.

This is only one example of how ‘cutting a corner’ can help to cope with a complex and dynamic environment. And looking at the (very low) number of incidents we have, we are not too bad at coping.

I avoid saying ‘safe’ or ‘safety’ here because in my view safety is different from absence of serious incidents. Safety is rather implicitly present because aviation and especially air traffic control is not a system that is designed and works ‘as designed’ but which functions well because of the day-to-day interactions involving human beings, who all try to cope the best they can.

And in the end it is because of this permanent interaction that progress and safety evolves. New rules and procedures on the other hand, no matter how well-intentioned they might be, too often constrain the adaptive powers of the people interacting and do not necessarily enhance safety.

Despite this, it goes without saying that I am responsible and, if you will, accountable for my actions and decisions within my radius of operation (just culture). And you can rest assured that I am the worst critic of my actions and decisions and, like my colleagues, I will always FEEL responsible for the outcome.

Andreas Conrad

Supervisor ACC Langen

DFS, Germany


Source: EUROCONTROL (2014). Systems Thinking for Safety: A White Paper. Brussels.