Managing Flying Risk – Collision avoidance
Avoiding collisions is a fundamentally important aspect of managing flying risk. Effective lookout is the primary method of avoiding collision. Pilots can reduce risk by planning to avoid the situations that can lead to mid-air conflict, by attempting to be predictive (ie following established good practice and protocols), and by understanding the protocols and rules of the air. The following are ‘Collision Avoidance’ rule extracts from Standardised European Rules of the Air (SERA);
An aircraft shall not be operated in such proximity to other aircraft as to create a collision hazard.
The aircraft that has the right-of-way shall maintain its heading and speed. An aircraft that is obliged by the following rules to keep out of the way of another shall avoid passing over, under or in front of the other, unless it passes well clear and takes into account the effect of aircraft wake turbulence.
When two aircraft are approaching head-on or approximately so and there is danger of collision, each shall alter its heading to the right.
When two aircraft are converging at approximately the same level, the aircraft that has the other on its right shall give way, except as follows:
- power-driven heavier-than-air aircraft shall give way to airships, sailplanes and balloons;
- airships shall give way to sailplanes and balloons;
- sailplanes shall give way to balloons;
- power-driven aircraft shall give way to aircraft which are seen to be towing other aircraft or objects.
An aircraft that is being overtaken has the right-of-way and the overtaking aircraft, whether climbing, descending or in horizontal flight, shall keep out of the way of the other aircraft by altering its heading to the right, and no subsequent change in the relative positions of the two aircraft shall absolve the overtaking aircraft from this obligation until it is entirely past and clear.
A sailplane overtaking another sailplane may alter its course to the right or to the left (please note that this is a SERA rule and may not apply outside Europe).
An aircraft in flight, or operating on the ground or water, shall give way to aircraft landing or in the final stages of an approach to land. When two or more heavier-than-air aircraft are approaching an aerodrome or an operating site for the purpose of landing, aircraft at the higher level shall give way to aircraft at the lower level, but the latter shall not take advantage of this rule to cut in front of another which is in the final stages of an approach to land, or to overtake that aircraft. Nevertheless, power-driven heavier-than-air aircraft shall give way to sailplanes.
An aircraft that is aware that another is compelled to land shall give way to that aircraft.
Opposing circuits (also known as mirror circuits) to the same landing area involve gliders and/or tugs potentially approaching each other on the base leg at a relatively high combined speed when the attention of both pilots is inevitably concentrated on positioning their aircraft in relation to the landing area. Opposing circuit traffic will be difficult to detect. As such, opposing circuits to the same landing area represent a potentially significant hazard that pilots need to be aware of.
Traffic and collision warning systems
The BGA encourages the widespread use of traffic and collision-warning systems in gliders, motor gliders and tugs. FLARM is an increasingly popular system. Pilots should make their own decision on equipage based on compatibility with other systems and as to whether such a system is appropriate for their particular operation. Pilots are reminded that whilst electronic collision warning equipment can enhance pilots awareness by providing most useful warnings, such equipment cannot and must not replace a good systematic visual lookout scan, and that it is necessary to avoid any in-cockpit equipment from distracting from the visual lookout scan. Detailed guidance re lookout supported by electronic conspicuity is available here.
To assist pilots in maintaining effective lookout, gliders operating from BGA sites should be equipped with audio variometers and the pilots trained in their use.
The radio can be a very helpful situational awareness tool if used correctly. Planning ahead in terms of frequency selection and the message, using the correct call signs, and using clear, normal language all help to reduce the potential stress and distraction that can be associated with airborne use of radio.
When soaring, pilots must take into consideration other soaring aircraft and the topography. The BGA Soaring Protocol provides guidance.