Airport CDM - expert solutions for Collaborative Decision Making

Continuous Descent Approach

Current ‘two-stage’ Instrument Landing System (ILS) intercepts often lead to a segment of level flight between the two stages. The use of a continuous descent technique during intermediate and final approach will benefit the environment by:

Reducing fuel consumption
Lowering CO2 and other emissions
Minimising noise for communities beneath the approach ‘footprint’ area

Under revised operational principles Air Traffic Control will endeavour to keep arriving aircraft as high as possible for as long as possible in order to reduce fuel burn and minimise the impact of noise (a reduction of up to 5dBA in noise levels and approximately 25% in footprint size are achievable). Dependent on ATC speed restrictions and wherever safe and feasible, aircrew are further encouraged to adopt minimum flap settings and to avoid early deployment of landing gear, both of which would otherwise increase drag and airframe noise. Whenever safe to do so, aircrew are also requested to avoid the use of reverse thrust on landing, thereby further reducing the aircraft’s noise footprint once on the ground.

Many airlines and airports are reporting on their successful use of CDA, although the benefits of its adoption are often cancelled out by other factors: for example an airport or ground handler may be unable to react promptly to an aircraft’s ‘early’ arrival. This may cause the inbound aircraft to be held on the taxiway (due to no gate being available), or indeed to reach the parking stand only to find that the ground handler’s resources are stretched and ground power cannot be connected immediately, which then necessitates excessive running of engines or the aircraft’s Auxiliary Power Unit (APU).

More accurate information on inbound arrival times, coupled with full sharing of information and precise timings on departing flights, will serve to maximise the use of an airport’s infrastructure and the resources of its ground handlers, successfully forging a link between CDA and CDM.