Description

Modern aircraft design permits high rates of climb or descent. High vertical rates help to achieve better fuel efficiency and allow for flexible use of airspace. After take off, high climb rates are desirable for noise abatement purposes.

Effects

A high rate of climb or descent can trigger operationally unnecessary (nuisance) Airborne Collision Avoidance System (ACAS) RAs.

A high rate of descent during an approach to land maybe a contributing factor in unstabilised approaches.

While high vertical rates help air traffic controllers in more efficient handling of traffic in their sector (aircraft reach the cleared level quicker), the controllers should be aware that high vertical rates may trigger unwanted TCAS RAs and, consequently, a deviation from the current clearance.

Defences

• Well designed SOPs should guide the pilots how to manage the aircraft in order to benefit from high vertical rates and how to avoid rates that are excessive (e.g. causing unwanted RAs). Most of unwanted RAs caused by high vertical rates can be avoided if the vertical rate is reduced to 1500 feet/min. or less at least 1000 feet before the cleared level.

• Airspace design that avoids simultaneous horizontal and vertical convergence of aircraft.

Contributory Factors

• Inadequate SOPs;

Solutions

• Review and if necessary improve Standard Operating Procedures (SOPs);

• Insist that SOPs are followed;

• Airspace design;

• Controller and pilot training.