Reserve deployment on Wether Fell

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dm64
Posts: 54
Joined: Wed Oct 05, 2011 4:17 pm

Reserve deployment on Wether Fell

Post by dm64 » Sat Jan 19, 2019 11:50 am

There was a reserve deployment on Wether Fell in December. Happily, the pilot landed safely and walked away without injury. However the incident highlights the importance of maintaining your reserve in good condition and being prepared to use it.

Although reserve deployments are rare, especially in the UK, it can happen … even on a site such as Wether Fell that may appear quite benign and you are perfectly familiar with. Regardless of the why or the where, if you are unfortunate enough to have to throw your reserve, it needs to deploy quickly and effectively. A big part of ensuring that happens is a regular repack and to that end most clubs organise an annual repack event. If you have not already done so, now is the time to repack your reserve to be ready for the new flying season.

At the time of the incident, the pilot was about 300’ above the hill and experiencing a layer of shear turbulence. Without warning, the wing was knocked back and immediately depressurised. At the same time the pilot swung forward and as the wing depressurised he felt a few moments of weightlessness as he went into freefall. When the wing repressurised it was in front and below him with a 360 degree twist in the risers. He immediately realised the situation was unrecoverable given the height and threw his reserve. Thankfully he landed without injury, rolling down a steeper part of the embankment a little before coming to a stop. As he was unable to kill his reserve - each time it came down it re-inflated again - he kited it back up the slope until a colleague, who had witnessed the incident and landed, came to help.

All of the pilots I spoke with who were on Wether Fell that day reported the same conditions. Wind was quite light on launch with a strong shear layer about 300’ above the hill. This was possibly caused by wave bouncing off a layer of cold, stable air that had pooled in the valley overnight, effectively presenting itself as a solid surface to the change of wind higher up. There are a number of points we can take from this incident:

Do not hesitate to deploy your reserve
The pilot did not hesitate to deploy his reserve. Given how low he was, a few seconds hesitation and the outcome could have been very different.
Sadly, there are many cases of serious accident and worse where there was time to deploy the reserve but for some reason the pilot did not do so. Although we think of the reserve as our last line of defence, it should not be our last thought in the event we may need it. An incident like this can be hugely disorientating and it is very easy to get so focused on recovering the wing that we forget how much height we are losing.

I’ve experienced this first hand during my first SIV course. The particular manoeuvre for the flight was a spiral dive which I felt reasonably comfortable attempting as I had done some before so I decided to commit fully to the manoeuvre and enter the dive aggressively with a lot of weight shift and a strong pull on the inner control. Within one or two 360s I found myself in a situation I was not familiar with – there was less g-force than expected and I seemed to be flying backwards through the air, not forwards. I was not particularly concerned - I had plenty of height and working under the assumption that it was a spiral dive I felt confident I could exit when required. It was only when the instructor came across the radio and said I was in a SAT that it made some sense. Ahhh, so this is what a SAT is – I had heard about it before but didn’t really understand what it was or the mechanics of it. I had probably done four or five 360s at this point when I decided to come out of it. I let up on the inside control a little as I was used to doing when exiting a spiral dive. But nothing happened. So I let up a little bit more – again nothing. Hmmm … I tried a little weight shift to the outside – again nothing. Finally I let up completely on the inside control, weight shift and a strong pull to the outside and I eventually came out. I had just enough height above the lake to make it to shore and land. The rescue boat was already beneath me. Reviewing the video footage afterwards I counted thirteen 360 degree turns before disappearing behind the tree line along the edge of the lake. And although I do not remember hearing him at the time, the instructor was repeatedly telling me to throw my reserve. We had a laugh about it in the pub afterwards but my instructor made it clear how serious a mistake I had made in getting so focused on recovery that I forgot to monitor my height.

The point is this: recovering the wing should be secondary to landing safely. If in any doubt about your height above the ground throw your reserve. Without a lot of experience and training in recovery from such dramatic scenarios it is impossible to judge how much height you may need – if in doubt, get it out!!!

Rehearse pulling your reserve and visualize
Speaking with the pilot about the incident he told me he rehearses pulling his reserve on every flight, reaching down to touch the handle and simulate pulling it out. Visualization is a powerful technique which can improve our chances of reacting in the correct way when we need to. As a result, the pilot had no issue locating the reserve handle and deploying without needing to search for it. Fumbling around for the handle while you are being tossed around in your harness can lose precious seconds.

Regular repack
Talking with an eye witness the reserve deployed quickly and efficiently. Maintaining your reserve in good condition with a regular repack is an important factor in this.

Where was the Pilot error?
A common theme in analysis of events like this is pilot error. I had a good discussion with both the pilot himself and another who witnessed it first hand and we could not come up with an explanation that could be attributed to pilot error. In fact the very opposite, I believe the pilot reacted very well by deploying without hesitation. The pilot is experienced and was current at the time. The technique to control your wing when knocked back violently is to wait for the surge then apply whatever amount of control input is needed to catch it. But this depends on a surge. In this case, the wing was knocked back and fully depressurised in one movement – once depressurised, there is nothing to control. Conditions on launch were light so there was no indication to suggest launching was a bad idea. Other pilots were flying at the time and although all reported rough conditions at the shear layer, none experienced such an extreme event.

In the end all we could do was chalk it up to bad luck which is a little disconcerting. Finding the ‘pilot error’ can be like a comfort blanket – as long as we do not make the same mistake we can avoid the situation. But the truth is Free Flight is an adventure sport with an inherent risk. There is certainly much we can do to minimize this risk but it cannot be eliminated. So remain vigilant and avoid the trap of complacency.

Winter flying
Finally I’d like to mention the particular risks involved in flying during Winter. This has been written about before and should not be new to us. However, where safety is concerned, there is no harm in repeating the message. During the Winter months the airmass is a lot colder than during Spring or Summer. Colder air is naturally denser and heavier than warmer air and for a given wind strength, the cold dense air will have a lot more momentum than a similar wind in a warm air mass. In short, the wind and associated turbulence in Winter will have more punch to it than the same wind strength during Summer. An analogy is the difference between rolling a football and a bowling ball – because the bowling ball is heavier, it takes more energy to get it rolling at the same speed as the football. Ask yourself this: which do you think would have a greater impact hitting your wing – the football or the bowling ball?

As always, fly safe
David May
DHPC Safety Officer

tramp
Posts: 131
Joined: Sat Mar 25, 2017 10:30 pm

Re: Reserve deployment on Wether Fell

Post by tramp » Sat Jan 19, 2019 9:15 pm

Sounds like a close call! Glad the pilot walked away.

Not so sure about the air density bit.

Density of air at 15 degC = 1.225 kgm^3
Density of air at 0 degC = 1.292 kgm^3

(https://en.wikipedia.org/wiki/Density_of_air#Dry_air)

If I've got my sums right (?) that's about 5% change in density.

The difference between winter and the rest of the year might just be down to the kind of days that are flyable in winter - stable with inversions, wind shear layers and steep wind gradients, and no thermals to break it all down.

Martin Baxter
Posts: 1478
Joined: Thu Mar 20, 2008 12:18 pm

Re: Reserve deployment on Wether Fell

Post by Martin Baxter » Mon Jan 21, 2019 12:03 pm

Thanks David. Excellent write up and a very timely reminder for all of us.

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