Managing Flying Risk – Hill, ridge and mountain soaring
Soaring on hills, ridges, and mountains is inherently more hazardous than other types of soaring because of the proximity of the ground. Too many glider pilots, even those with a lot of experience, have had accidents from not adopting the required flying techniques.
Knowledge and training
Safe preparation and pilot behaviour including human factors requires relevant theoretical knowledge, and prior tuition in a two-seat glider to develop the necessary practical skills.
The following publications are recommended reading for all pilots who intend to soar hills, ridges, or mountains:
Pilots visiting an unfamiliar hill, ridge, or mountain site should carefully consider locally prepared guidance on safe operations. A template for such club guidance is included at appendix 1.
Remaining in sight of the surface
Ridges, hills and mountains generate cloud. It is critically important that pilots are aware of the need to remain in sight of the surface at all times and to avoid being enveloped by or flying into cloud when ridge, hill or mountain soaring. This New Zealand summary of an incident involving an instructor and an experienced student pilot who allowed themselves to drift into cloud when ridge soaring is educational.
Knowing when to give up
When ridge or thermo-dynamic lift is so weak that the glider is not climbing, pilots can become overly-optimistic that the conditions will improve. This is a dangerous situation as the pilot will be very tempted to shave off the safety margins in terms of distance from terrain and speed. If the glider isn’t climbing, use your plan B, whether that’s another source of lift or heading towards a landing opportunity.
Thermals drifting across flat slopes can become a lethal trap as a glider pilot who was climbing suddenly finds the glider sinking onto terrain that is flatter than the now achieved (steep) glide angle. If the rate of climb when drifting across a slope is not enough to obviously climb the glider away from the terrain below, revert to plan B.
CAA hill soaring exemption from SERA minimum height rule
Soaring is using the air efficiently and safely in order to maintain height or climb. Hill-soaring (also called ridge soaring or mountain soaring) is flying in rising air alongside hills, ridges and mountains with the aim of soaring efficiently and safely.
The Civil Aviation Authority permits, under an exemption to ‘SERA.3105 Minimum Heights’ and SERA.5005(f) ‘VFR Flight Minimum Height’, a glider to fly below 150 metres (500 feet) above the ground or water or closer than 150 metres (500 feet) to any person, vessel, vehicle or structure if it is hill-soaring. In doing so, pilots must comply with ‘SERA.3101 Negligent or Reckless Operation of Aircraft’, which states that an aircraft shall not be operated in a negligent or reckless manner so as to endanger life or property of others. Public/third-party safety is the absolute priority. It is extremely important that the exemption is only utilised for its intended purpose.
The following protocols should be followed by all pilots. The first three points also help pilots to safely interprete the hill soaring exemption:
- Where reasonably possible, remain 500′ clear of people and property.
- Do not fly lower than necessary to utilise the soaring conditions
- NEVER fly close to, towards or directly over any person on the ground.
- Lookout is always paramount.
- Remain clear of other aircraft. The glider with the ridge on the right has priority.
- Overtake with caution, bearing in mind the other glider could suddenly change direction.
- Make all turns away from the ridge.
- Be aware that when flying with a significant drift angle, FLARM direction indications can be misleading.
- Always have an available safe landing option.