I am wondering how fast someone goes while cross-country ski hiking.

Average walking speed is 3.5 miles/h (5.6km/h).

For cross-country skiing, I have found the values 8mph (12.8km/h) for recreational skiers and 15mph for professional racers.

I have done a rough trace of the route they covered, from 2nd Northern to the tent site. This does not include possible detours due to navigation errors, though I did include the attempted crossing at the pass, then turning back to the Auspiya valley and back up to the tent again. Otherwise it's just tracing Lozva then Auspiya:

Total distance: 49.4km.

At average walking speed, it looks like this can be covered in 9 hours?

And skiing is faster than walking, using the 12.8km/h estimate, this could be covered in 4 hours?

In the group diary entry for 31-Jan, it can be read that they are now in deep snow and not following a trail, thus cannot do more than 1.5km/h. Assuming this is somewhere near the pass in the Auspiya valley, for example 7km from the tent site, that distance could still be covered in 5 hours.

According to the same diary, they started on the 28-Jan before noon from 2nd Northern, including that day, it took 5 days to reach the pass.

Counting with 7 hours per day, this is a speed of 1.4km/h, slower than in the deep snow without a trail. But for most of the trip, they were skiing on frozen rivers.

These are all just rough estimates but the speed they achieved seems to be way too slow. Is something wrong with my calculations?