Update by Charles Kirwan-Taylor, Corporate Affairs & Sustainability Director

8 February 2016

Charles Kirwan-TaylorThis week has seen a great deal of activity in respect of Route 4. As mentioned in my previous blog, we have recently conducted simulator trials to test the suitability of the Route 4 modification in a variety of scenarios including variances to speed, aircraft weight and meteorological conditions.

During the evaluation process of the simulation exercises it became evident that there is not going to be a single solution to Route 4 that will deliver the required outcome for local communities that would be acceptable to airlines and air traffic control. Reasons for this include the non-standard nature of potential operating procedures required to bring all traffic in all conditions within the confines of Route 4, together with the increased Air Traffic Control and pilot workload that would be required to enable this. This is consistent with our previous experience of this route, as prior to the implementation of P-RNAV, there have been long standing difficulties with aircraft track-keeping which were exacerbated in periods of strong south-westerly winds. These are the same issues that have led to the difficulties which are currently experienced on this route. 

We have evaluated carefully the simulator results and the associated accuracy of track-keeping to decide upon an solution that should deliver the best possible outcome for the communities on the ground and airlines alike. 

The solution we have decided upon is two-fold.

First, we will submit a SID modification to Route 4 that will implement a speed restriction on the turn of 220 knots. It is anticipated that in most weather conditions, this speed restriction and the SID modification will ensure aircraft remain within, but close to the edges of the Noise Preferential Route associated with Route 4. We submitted the Airspace Change Request to implement these changes on 4 February 2016 to the Aeronautical Information Service, in advance of their 5 February deadline for these changes to come into effect on 26 May 2016.

While this modification will be an improvement for the majority of the time, we and our partners are of the opinion that this would still not give the effect we want during periods of strong south-westerly winds where ‘ballooning’ to the north-west of Route 4 would remain a possibility. To address this we are investigating introducing an additional SID to be used in periods of strong south-westerly winds. It is anticipated that this procedure is likely to require a speed restriction of 190 knots such that the aircraft would fly slower and in a different configuration to the 220 knot solution as detailed above. We do need to do further work to evaluate the feasibility of this route which will include discussions with the airlines, Air Traffic Control and our airspace designers. Consequently we are not be in a position to submit this as an Airspace Change Request at the same time as the 220 knot solution but will work to develop this as an alternative option over the next several weeks.

In simple terms, this means that we should be in a position to adopt a new route in May which will offer a closer conformity to what we had intended, and which in most weather conditions will take more of the air traffic back inside the NPR. At the same time we will develop and submit another proposal for use in periods of high wind, which we intend will be adopted perhaps two months later. This should then have the effect of bringing an even greater proportion of traffic inside the NPR, consistent with our original objectives in this modification exercise.

In arriving at this overall solution, and in bringing at least a partial solution to this issue into view before the summer, we've had a great deal of help from the CAA, NATS and our airline partners and we're very grateful for their assistance.

The chart below shows our progress against the tasks that we've set: