OPTIMAL

New Rotorcraft Procedures: SNIops

The University of Liverpool is working within the OPTIMAL work package that is developing new rotorcraft procedures, paying special attention to the context of airports allowing Simultaneous Non Interfering (SNI), IFR (Instrument Flight Rules) rotorcraft operations. The new SNI procedures for rotorcraft are aimed at incorporating steep and/or curved and segmented trajectories. The benefit of these is the smaller noise footprints resulting from the higher altitudes of flights over population zones adjacent to airports and also the lower noise emissions of rotorcraft in steep approaches (greater than 6°).

Important for the development of future SNI operations are the safety issues associated with interactions between rotorcraft and fixed-wing wake vortices in these new scenarios. It is well known that these vortices are a potential risk to conventional fixed-wing traffic but what are the risks to rotorcraft? Longitudinal separation rules have been in place for conventional traffic on the same approach path for many years but what about simultaneous, laterally separated rotorcraft traffic? These questions raise even more fundamental questions related to the SNI concept for rotorcraft.

The work required to answer these questions represents a significant undertaking, especially b) which relies heavily on being able to predict the complex motion and decay of the vortices after they are generated. Part a) also requires a further breakdown, as the question of measuring severity of an encounter has yet to be defined. In addition, the question arises to whether the severity of an encounter and the ability to overcome an encounter can be linked to the handling qualities of the encountering rotorcraft.

The University of Liverpool is contributing to the project by building upon past research in the modelling and simulation of rotorcraft vortex wake encounters. It is developing methods that will eventually allow the definition of the safety boundaries in terms of where rotorcraft SNI operations can take place and for defining the flight envelopes for different rotorcraft types. The important factors for such a study will include the wind speed and direction, the vortex generating aircraft (e.g., Airbus 310, Boeing 737), the encountering rotorcraft type and the rotorcraft’s trajectory (approach, hover, take-off).