Flying GA (unpressurised) aircraft at higher altitudes
Hi,
recently I've been doing some longer navigation flights, and for convenience with regard to terrain/airspace, chosen flight levels such as 115, 105, or 095, depending on direction. I've noticed that after some time in cruise I started to yawn, lose incentive to proactively scan the surroundings, and just wanted to get comfy in my seat.
At first I thought it was isolated but after arriving at my destination airports somewhat tired every time, I figured it might have something to do with altitude. I've lived my whole life near sea level so I might not be accustomed to prolonged stays at reduced oxygen levels.
I've read some reports on here of people using supplemental oxygen from FL080 or FL050 at night... Is it really necessary? What's your take on it, any similar experiences or suggestions?