This backpack is an updated version of the old Alpha FL 45. Yes, you read that correctly. So why did they shave off 5 liters of capacity? The reality is that the old Alpha FL 45 was a 38-liter pack, extendable to 45L. The extendability of that pack was provided by the full roll-top extension, pulled outside the pack top access, essentially creating a 45L burrito shape. In theory (I didn’t have the old pack to compare) the new FL is, in fact, 40L true capacity without extending the roll-rop. By testing the pack in the mountains, I could fit almost the same gear I usually carry in my HMG Southwest 3400, a 50L pack (+ external pockets). For this reason, I would say the Arc’teryx Alpha FL 40 is, when loaded to the maximum capacity, a 45-48L pack in total.
Organization is key when packing all your gear into the single compartment of the Alpha FL. Arc’teryx provides two small pockets (one internal and one external) for keeping small stuff like snacks, GPS, or sunglasses handy for quick access. But the rest is up to you and your ability to make your gear sit properly inside the pack. It’s fair to admit that the internal and external pockets become unusable if the Alpha is loaded to the extreme.
I found that by using the internal roll-top liner wisely, it is possible to separate the gear you want to keep dry from the wet hardware you just used on the ice wall. My usual set for a day of ice climbing is a puffy jacket, spare gloves, and food that I stock inside the Alpha’s drybag liner, and then climbing hardware, thermos, and goggles in the open compartment (closed with the drawstring). In this way, you have a two-compartment carry.
I’ve been reading quite a lot of customer feedback about the old 45L. Almost everybody complained about the shoulder straps being uncomfortable at heavy loads. But it looks like the Arc’teryx product team improved this issue because I think the pack is very comfortable when used with loads under 16-18kg.
Actually, it’s one of the most comfortable packs for short approaches or spring alpinism. However, I’ve also had the chance to carry a decent amount of winter camping and climbing gear, pushing the limits to about 22-24kg, and I definitely missed the straps of my other “workhorse” packs.
Most of the problem happens when the pack is fully loaded and the drybag liner is fully extended. The height of the lid section matches the length of the straps, creating a very delicate balance between the top part and bottom (which makes it very difficult to lift the pack and wear it).
So, in the end, I would say that this pack is very comfortable until it isn’t. I don’t think Arc’teryx recommends a maximum load but I guess they depend on the user’s common sense to remain under a certain load. The problem starts when an alpinist has the necessity to carry gear for longer approaches—which means full winter camping gear plus climbing gear—but, again, this pack is specifically for fast and light adventures.
I’ve included accessibility to carry gear under comfort considerations. I have to say the crampons and the ice axes strapped into the front of the pack stay very firmly in place and at the same time are very easy to access and unbuckle, simply by releasing a single drawstring. That’s very important when you are in the middle of a climb and want to put away one ice tool quickly without unloading other gear.