Gliding Descent to Save Fuel

[Bergerie1]

Constant Descent Approaches (CDAs)

CDAs are nothing new; we have been doing them for years. They are no more than descents from TOD at idle power to the start of the approach. And while we are at it, let’s kill stone dead the idea of glide approaches to touch down in commercial operations! The CDAs that SAS and others have been doing all require the aircraft to be stable (Vref+ the correct increment, gear down, landing flap, and power set) at or before 1000ft agl. The problem is how do you do this in a complex and busy ATC environment without reducing the overall capacity of the system?

Recently, several new technologies have been tested in simulations and line operations. The first is ADS-B which uses the Mode S transponder to broadcast information on the aircraft’s position and intent. ADS-B ‘Out’ can provide ATC with better information than current radar. If ADS-B ‘In’ is fitted as well, the aircraft can receive this same information and display it in the cockpit. Page 37 to 41 in the Flight Safety Document on this website will explain more:-
http://www.flightsafety.org/asw/jul09/asw_jul09.pdf

The FAA in their work on NextGen and the Europeans in the SESAR Joint Undertaking are working towards the same ends. The current problem is that ATC do not know what the aircraft is doing and the pilot does not know where he/she is fitting into the traffic pattern. Modern FMS has much better information of the aircraft’s position and projected trajectory than anything ATC can conjure up. So, if this can be data-linked to ATC it would become possible for them to fit aircraft much more elegantly into the overall system and thereby improve safety, reduce workload and improve economy. Equally, if the pilots could see where they are in relation to other traffic in the descent and approach pattern, they could have certain tasks delegated to them by ATC, e.g. to follow in the stream at a constant distance or time interval from preceding aircraft. Eurocontrol and other research bodies have done extensive simulations using active line pilots and active controllers and have proved it can work. Also, UPS at Louisville in Kentucky have been using the system in line operations. See the presentation 6 at the ASAS Global Network Forum in this website:-
http://groups.google.com/group/asas-global-network?hl=en

I have also flown similar systems in simulations at NLR’s facilities in Amsterdam and can vouch for their potential. So, let’s remove the concern about glide approaches and see how the whole ATM system could be improved to increase safety, capacity, economy, and reduce environmental emissions.