DESCENT MANAGEMENT
Good descent management is a key factor in operating the aircraft efficiently. It is also an area which has the potential to cause problems for pilots converting to type, particularly if their experience has been attained only on smaller aircraft (with less momentum) or turboprops (which can usually descend and decelerate better).
If we firstly compare energy of an Airbus 320 compared to a small aircraft. Kinetic energy can be measured in terms of ½ × mass × velocity ²
Airbus 320 at a typical descent speed of 270kts at Max landing weight:
66 Tonnes at 270kts = 2,405,700 units of kinetic energy
A typical light aircraft descending at 100kts:
1 Tonne × 100kts = 5,000 units of kinetic energy.
As can be seen from the above calculation, the airbus has approximately 480× the kinetic energy of a light aircraft in the descent. This energy (or momentum) manifests itself in the descent and deceleration to approach and needs to be handled carefully.
It is often commented on that "the aircraft doesn't go down and slow down!", although this comment isn't strictly correct, it does perhaps demonstrate the importance of proper descent planning and management.