High Altitude Flame Out
I fly a Cessna Citation.
41000ft is the maximum allowed altitude according to the limitation chapter of the AFM. The AFM says that altitudes are pressure altitudes unless otherwise stated, so 41000ft means FL410.
Although there is nothing more about that in the operation manual of the company, some experienced captains say that the limit is a density altitude. So when the forecast says that at FL410 the density altitude will be above 41000ft, they don't plan for FL410. Another limitation is ambient temperature (ISA+35 at seal level decreasing to ISA+23 above FL360), but even when far from the limit, they don't plan a level above 41000ft density altitude. They say that engines could flame out. They explain why, and of course I understand that there is an ambient density threshold below which the fuel won't burn, but I suppose that within the AFM limitations the ambient pressure remains far from that threshold.
I pointed out that neither the AFM nor the operation manual mention it, but they know better, and I dare not insist before having other opinions about that.
Last edited by 172510; 24th July 2022 at 17:38.
Reason: typos