Firstly remember this is just one subjective opinion. Please make your own mind up and take responsibility for your own actions!
Spring - Generally from late March until mid May is the best time of year to ski on Ben Nevis (or indeed any Scottish gully). By late spring the gully's should have accumulated snow through out the winter & surfaces should hopefully be stable and consistent. The huge cornices often seen on Ben Nevis will be starting to retreat by about mid April. Conditions on Ben Nevis are surprisingly reliable, and even in a lean year there will be significant snow cover until at least early May. 2000ft vertical descent's have recorded on Ben Nevis as late as mid summers day (21st June!)
Step in crampon's, that attach to your ski boots, and an ice axe are essential. (however 2 axe's will make the climbing much easier!)
It might be a good idea to bring a friend along who has some rope & belay skills - primarily for getting over some of the larger cornices...
As for skis - crank the DIN setting up as far it will go, sharpen your edges, and avoid carvers with a super side cut.
On steep terrain the hour glass shape of more pronounced carving skis can leave less edge in contact with the snow.
Climbing the gully first is strongly recommended - especially on Ben Nevis. Gullys can be surprisngly hard to locate from above, even in good weather.
Climbing first allows you to check out the descent route and avoid potential surprises on the way down
- such as ice climbers ascending, poor snow conditions or rock fall etc.
Do some assessment of the snow pack before setting off & also read the SAIS forecast.
(but remember this can and does change througout the forecast period).
Be aware of the potential cornice collapse from above, particularly in Spring time.
Its courteous not to ski above any climbers who may also be using the gully.
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