PA28 Up high
About 6 weeks ago did FL180 in a PA28, The last 4000ft took forever! total sortie time till back on ground 2 hours 10 mins! Both GA pilots but we have a military experience as engineer/atc and did it professional in my view. Briefed on hypoxia (portable oxygen sets, watched each other for any tell tail signs), icing, airspace, emergencies. In the end the fpm was virtuallly nil, we selected flap at one stage to get a little lift!
NM