Careful on rainy days!
- 5 days ago
- 4 min read
The first information I remember reading about flying paragliders in the rain were the general warnings from the DHV in the 1990s. At the time, pilots were advised to avoid rain because of reduced visibility and the possibility of water collecting along the trailing edge of the wing.
I also recall that around 2010, in the manuals for the GIN Boomerang 7 and GIN Boomerang GTO, Gin began warning pilots about altered flying characteristics and stall behaviour of the new generation of high-performance wings when flown wet.
Up until then, most pilots believed that flying in rain was simply unpleasant. Rain hurts when it hits your face, visibility is reduced, and "flying the glider dry" afterwards was generally considered an acceptable solution.
Changes in glider design and materials have since introduced new challenges. Reports began to emerge of modern wings entering deep stalls after becoming wet.
In 2017, Cross Country Magazine published an article explaining the issue in detail. The article is still available online and is well worth reading, so there is no need for me to repeat it all here.
The short version is this:
Water can accumulate inside and in the trailing edge of the wing, but the more significant effect appears to come from water droplets forming on modern sailcloth. Today's fabrics are smoother and more water-repellent than older materials, which tended to absorb moisture rather than allowing droplets to bead on the surface.
These droplets alter the airflow over the aerofoil. The boundary layer becomes disturbed, lift decreases, drag increases, and the stall point moves closer. The wing may stall with less brake input than expected. Modern designs with higher aspect ratios, reduced passive stability, and more aggressive profiles appear to be more susceptible to these effects.
Once a wet wing has entered a deep stall, it can be relatively easy to transition into a full stall if incorrect inputs are made.
What to Remember
Rule No. 1: Avoid flying in rain or1 in cloud that may get your glider wet.
Winter weather often makes us more tempted to squeeze in a flight between showers. Unfortunately, this can increase the risk.
We've observed that winter showers can build more quickly than many pilots expect. While summer air can hold more moisture before condensation occurs, winter air often reaches saturation rapidly. Showers can develop quickly and spread in size, particularly when incoming air is forced upwards by terrain such as the cliff you are flying along.
By the time the rain arrives, escaping it may no longer be easy.
Always maintain a safety margin that allows you to land before your wing becomes wet.
If You Get Caught in the Rain
If you misread the conditions and find yourself flying a wet glider, give yourself the best possible chance of getting down safely.
Land as soon as possible.
Keep your airspeed high and your angle of attack low. Fly at trim speed and consider using some speed bar.
Avoid anything that may further disturb the airflow. Most manufacturers advise against using big ears on a wet wing, as they may increase the risk of a deep stall.
Deep Stall
Getting into a deep stall or parachutal stall is the risk. Such stall occurs when the airflow no longer remains attached to the wing in the normal way. The wing stops generating efficient lift and loses its forward speed. The internal pressure is reduced.
You are not in free fall because the wing still creates drag, behaving more like a round parachute than an aircraft wing.
Looking up, the canopy may still appear somewhat inflated and largely in shape, unlike a full stall. However, it often looks soft, wrinkled, and lacking internal pressure. The sink rate in deep stalls is too high to land safely, often 6-8m/s. You have no directional control and no forward speed.
Recovery
The key to recovering from a deep stall is airspeed.
Years ago, pilots were commonly taught to push the A-risers forward. Current teaching more commonly recommends applying speed bar smoothly and symmetrically while keeping your hands fully up and avoiding any brake input.
The objective is to reduce the angle of attack, regain airflow over the wing, and restore normal flight.
Training
The illustrations accompanying this article are taken from an article on stalls and flying incidents that I wrote for Airbornemore than 20 years ago. Both glider design and flying techniques have changed considerably since then.
Full stall recovery is taught differently today, so always follow the guidance of your SIV instructor.
More importantly, stalls, stall-point exploration, and recovery techniques should only be practised under professional supervision during an SIV course.
Most coastal sites simply do not provide sufficient altitude to practise safely and still allow time for recovery if things go wrong.
SIV courses provide:
Professional instruction
Radio guidance
Continuous monitoring
Safety boats
Life jackets
Water landings designed for training
Modern paragliders are significantly more dynamic than the wings many older pilots learned on. Reactions can be faster, more powerful, and less forgiving than experienced pilots of older paragliders—or parachutists transitioning into the sport—may expect.
Fly safe and stay dry.
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