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Eurocontrol request for flight plan adherence

Eurocontrol’s Network Manager has reported that there has been an increase in the number of ATC flight plans which have been planned to include so called ‘YoYo’ profiles, that is, a descent of 2,000–10,000 feet followed by a climb of similar magnitude to achieve a possible number of objectives. Eurocontrol is facilitating an initiative to reduce YoYo filing and the downstream consequences.

YoYo profiles appear in ATC flight plans for various reasons, but are hardly ever flown. When the ATC flight plan is not followed, Air Traffic Flow Management may fail in its objective to prevent ATC overload. While work is ongoing to reduce YoYo filing, pilots should be aware of the potential consequence of not flying YoYos that are in the flight plan. Optimum flight levels provided by FMS do not consider important constraints that were built in the ATC flight plan. If ATC insists not flying filed YoYos, pilots are requested to report this to their company.

The reasons for including these profiles in flight plans range from software issues and airspace constraints to wind component optimisation and avoidance of Flow Management regulations. YoYo profiles over 2,000ft are filed for 200–300 flights/day, although some operators file them more than others. 1,000ft YoYo-profiles are often due to flight level orientation rules for the routes.

There are various issues with these YoYo profiles. The main one is that YoYo profiles are hardly ever flown, which causes downstream predictability issues and unanticipated traffic. ATC flight plan route and level information is used for Flow Management purposes, to protect ATCOs from a demand more than they can safely handle. If required, the demand is limited through flow measures such as departure delay (ATFM slot). If tactical deviations from filed flight plans puts flights in a different ATC sector than assumed by ATFM, then the protection may fail and result in ATCO over-delivery/overloads. This is particularly the case with YoYo profiles that are not flown.

It is possible that ATC, despite the filed YoYo profile, keeps the flight at the cruising level, therefore deviating from the flight plan. A reason for this may be that ATCOs (currently) often do not have the means to see the filed YoYo descent, nor know the exact downstream impact of such deviation from the flight planned level. Work is ongoing to improve this, and some ANSPs implement system changes that provide ATCOs easier access to filed flight levels. Also pilots may request to stay at cruising level, to optimise fuel consumption. Even the ATCO may prefer this, given the often higher complexity and workload associated with climbing/descending flights in their sector. But as said, this is without realising the downstream consequence.

YoYo profiles are considered by some as flight planning techniques to overcome specific flight planning issues, not necessarily related to what is expected to be flown. This perception is negative for performance, not realising the use of the filed flight plan, such as protecting ATC against over demand.

Europe is facing significant capacity issues. With traffic further increasing, 2018 delay figures are increasing as well. Eurocontrol Network Manager facilitates a series of initiatives (4ACCs, FRA, First Rotation Optimisation trial) to tackle the problems, under which the activities to reduce YoYo filing and their predictability consequences.

Although only a few per cent of flights every day have 2,000ft+ YoYo profiles (200–300 out of daily ~32,000), they do have a big impact where they occur. Particularly in busy airspace, where regulations are often needed and where capacity is needed most, unanticipated (uncounted) additional flights in already busy sectors reduces the ATC trust in ATFM protection. This usually results on lower planned capacity, requiring more ATFM regulations, that is, more delay.

ANSPs have raised the YoYo issue many times over the last years, but aircraft operators and ATC pointing fingers at each other has allowed the issue, and associated loss of performance, to continue.

What can pilots do about it?

Identify YoYo profiles in your ATC flight plan. Question your dispatcher why these profiles exist. If to avoid ATFM regulation, then request ATC to fly the profile. Be aware that the ATCO may not be aware of the YoYo descent due to current ATC system limitations, so advise ATC of the descent. ATC may also reject the descent request due to traffic complexity. Many ANSPs are working on addressing this system limitation. When using FMS information to find optimum flight levels, realise that the FMS doesn’t give you the ATFM information which is built into the filed ATC flight plan. The FMS doesn’t know that a more optimum level may result in entering airspace where the ATCO is already working at full capacity, while the flight plan includes the measures to prevent that. For YoYo profiles as a result of ATC flight planning restrictions, report to your company if ATC usually ignores that YoYo profile and keeps you at cruising level. This will be used to align ATC flight planning restrictions with actual day-to-day constraints.

Please contact russell.dudley@eraa.org for more information about YoYo flight plans.