Collision avoidance
Avoiding collisions is a fundamentally important aspect of managing flying risk.
Lookout
Lookout is the primary method of collision avoidance in class G airspace. It is important to recognise that the limitations of the human eye means that effective lookout requires technique supported by other attributes available to pilots.
You can help to keep yourself and others safe by making the most of the following six attributes that are available to pilots;
Eyes – lookout for at least 80% of the time – and use a robust scanning technique, e.g ‘lookout, attitude, instruments’. Be aware that it is very tempting for pilots to spend most of their lookout time in the circuit focussed on the landing area. Maintaining a scan cycle that looks for potential threats is very important.
Ears – communicate by listening, and where appropriate, talking on the radio to enhance situational awareness. Clear and accurate circuit calls (e.g. ‘…downwind, left-hand, runway 03’ and ‘…final, runway 03’) are valuable aids to others situational awareness. In addition to setting the correct frequency and volume, you will need to have a charged battery. Consider fitting freshly charged batteries at some point during a long day of club glider flying.
Advertise – make your presence known with FLARM. Again, you will need to have a charged battery.
Foresight – fly defensively, with vigilance, courtesy, and consideration for others (good airmanship!). Try to be predictable, particularly in the circuit and in thermals, on a ridge, etc. So called ‘hangar flights’ can present increased risk as they invariably result in an unusual circuit and unfamiliar landing area.
Insight – standard circuit and site-specific procedures are designed to assist situational awareness and provide orderly, well-spaced, non-conflicting movement of gliders and aircraft. Review your understanding of site-specific operations, airspace rules, rules of the air and procedures. Consider how you might modify your circuit if you encounter other traffic or obstructions in the landing area. Be aware of and follow the Soaring Protocol.
Prioritise – be organised with cockpit tasks to avoid distractions compromising your lookout.
These UKAB videos illustrate all six points.
The circuit can present increased risk
Pilots flying in the circuit can be busy and spend a significant part of their lookout time assessing height, position and angle to the landing area. Situational awareness can be improved by hearing about the location of others in the circuit.
Clubs are strongly encouraged to:
- develop well thought-through local circuit procedures designed to avoid collision risk.
- maintain circuit discipline, i.e. adherence to procedures
- not operate aircraft whose airframes restrict visibility without taking such limitations into account in circuit procedures.
- where agreed as part of club procedures, require pilots operating on their site to make appropriate circuit position calls. At most airfields, pilots are expected to report when on the downwind leg and on final approach to land. In some situations, other calls such as ‘base leg’ may be advisable.
Pilots are strongly encouraged to make appropriate circuit position calls. At most airfields, pilots are expected to report when on the downwind leg and on final approach to land. In some situations, other calls such as ‘base leg’ may be advisable. When joining the circuit, be clear about your intentions.
Instructors are strongly encouraged to familiarise student pilots with use of radio at an appropriate point during pre-solo training.
Owners of aircraft at BGA club sites are strongly encouraged to equip with radio. It is recognised that aircraft exist that cannot be equipped.
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 a popular traffic and collision warning system and particularly so within gliding where there is widespread adoption. All aircraft owners operating at BGA club sites are encouraged to equip with FLARM.
Pilots are reminded that whilst electronic collision warning equipment such as FLARM enhances pilots awareness by providing most useful warnings, such equipment is designed to supplement and 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 technology is available here.
Radio
The radio is 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.
Pilot radio licence guidance is available here.
Radio requirements information including BGA allocated frequency use is available here.
Audio Variometers
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.
Read more about in-flight equipment here.
Flashers
LED conspicuity flashers (screened flashing lights mounted on the canopy coaming, or embedded in the glider fin) are growing in popularity. Like landing lights, they are likely to be effective in head-on situations.
There are a couple of limitations to the effectiveness of canopy flashers. They have a limited angle of view in order to concentrate the beam for a high intensity (e.g. 18 deg horizontally for the main beam); and even that intensity isn’t always significant against bright daylight. They are likely to be effective in head-on situations. Most collisions are at other angles.
It is important that the flasher doesn’t limit the pilot’s field of view, that the installation is airworthy/secure, and that it doesn’t interfere with canopy jettison (most of the currently available flashers seem to offer appropriate connectors).
This video may be of interest.
Opposing circuits
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.
Soaring
When soaring, pilots must take into consideration other soaring aircraft and the topography. The BGA Soaring Protocol provides guidance.
This video by Mike Fox demonstrates important points about sharing a thermal with other gliders.
The rules
The following are ‘Collision Avoidance’ rule extracts from Standardised European Rules of the Air (SERA);
Proximity
An aircraft shall not be operated in such proximity to other aircraft as to create a collision hazard.
Right-of-way
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.
Approaching head-on
When two aircraft are approaching head-on or approximately so and there is danger of collision, each shall alter its heading to the right.
Converging
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.
Overtaking
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.
Sailplanes overtaking
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).
Landing
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.
Emergency landing
An aircraft that is aware that another is compelled to land shall give way to that aircraft.
Useful links
CAA Safety Sense leaflet – Radiotelephony
Drone midair conflict awareness
