Managing Flying Risk – Safe thermal soaring

Thermal soaring has been enjoyed by birds and their predecessors for millions of years and by soaring pilots in the past 100 years. We’re still learning and our eyes are not yet positioned on the side of our heads. We are not designed for flight.

As soon as there is more than one glider in the thermal at a similar level, the challenges for the pilots  increase significantly. The primary risk from flying in a thermal with others is mid air collision. This information signposts to existing safe thermal soaring guidance.


Lookout is the primary method of collision avoidance in class G airspace. 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 develop a robust scanning technique.
  • Ears – communicate by listening, and where appropriate, talking on the radio to enhance situational awareness.
  • 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.
  • Insight – review your understanding of operations in class G airspace, rules of the air and procedures. Be aware of and follow the Soaring Protocol.
  • Advertise – if available, make your presence known with FLARM. If cruising for extended periods of time, move around a bit to improve your visual conspicuity – and if flying a TMG, cruise at an odd altitude.
  • Prioritise – time share cockpit tasks to avoid distractions compromising your lookout.

Read more about lookout supported by electronic conspicuity here.

Soaring protocol

The BGA Soaring Protocol offers tried and tested guidance on joining and staying in a thermal with others.

Sharing a thermal

This short video ‘thermalling etiquette’ provides helpful guidance on how to fly safely in a busy thermal. (Bill Palmer)

This short ‘thermalling with others’ video provides further practical guidance on the practicalities of ensuring safe spacing in thermals. (Mike Fox)


The BGA recommends that gliders are equipped with an audio variometer and pilots are trained in their use.

The BGA encourages the widespread use of electronic conspicuity 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.

Most glider pilots fly with an emergency parachute. As gliders tend to fly close to other gliders, that’s a reasonable precaution. Parachutes have saved glider pilot’s lives.

Read more about in-flight equipment including radio here.


The BGA Gliding Syllabus highlights the need for awareness of safe practical conduct prior to a pilots first solo soaring attempt.

Human Factors including Competitiveness

The human inside us can lead to competitiveness (need to climb quicker) or frustration (that pilot isn’t turning tight enough) eventually resulting in a pilot taking a high risk action such as turning inside another or flying too close to another glider. It is very important that at all times we remain focused on safe flying techniques. If a thermal gets too busy, carefully leave the thermal before your stress levels increase.


FLARM works by calculating and broadcasting its own future flight path to nearby aircraft. At the same time, it receives the future flight path from surrounding aircraft. An intelligent motion prediction algorithm calculates a collision risk for each aircraft based on an integrated risk model. When a collision is imminent, the pilots are alerted with the relative position of the intruder, enabling them to avoid a collision.

Each FLARM system determines its position and altitude with a sensitive GPS receiver. Based on speed, acceleration, track, turn radius, wind, altitude, vertical speed, aircraft type, and other parameters, a precise projected flight path can be calculated. The flight path, together with additional information such as a unique identification number, is encoded before being broadcast over an encrypted radio channel twice per second.

A busy thermal can involve several FLARM-equipped manoeuvring gliders that may, if close to each other, momentarily trigger a collision warning. These occasional warnings can become normalised and result in pilots becoming complacent about FLARM warnings when thermalling. If a pilot is experiencing FLARM warnings, it means that a hazardous projected flight path has been identified.

It is important to understand how FLARM works and to understand the FLARM aural and display information that is provided to the pilot. Making sure any FLARM display is easily accessible as part of a lookout/attitude/instruments scan cycle is helpful.