Reply to thread

Message

Hi,

I can only speculate. Overheating would seem like a possiblity, as air-cooled engines have a hard time getting rid of heat at high altitudes. Another possible reason for the power reduction might be a deliberate reduction in engine speed to keep the propeller tip Mach number down, in order to keep compressiblity-induced efficiency losses at a tolerable level.

If the Ha-43 versions in question use water-methanol at the indicated power, it could also be a question of switching anti-detonant injection off above full throttle height, as detonation might not be a serious factor when you can't get full boost pressure up high. The charge cooling effect as well as the calorific value of the alcohol might warrant not switching it off directly upon reaching full-throttle height, but there's probably an altitude above which you'd decide to consider it uneconomic to keep it running.

Regards,

Henning (HoHun)

<blockquote data-quote="HoHun" data-source="post: 635875" data-attributes="member: 32143">Hi,I can only speculate. Overheating would seem like a possiblity, as air-cooled engines have a hard time getting rid of heat at high altitudes. Another possible reason for the power reduction might be a deliberate reduction in engine speed to keep the propeller tip Mach number down, in order to keep compressiblity-induced efficiency losses at a tolerable level.If the Ha-43 versions in question use water-methanol at the indicated power, it could also be a question of switching anti-detonant injection off above full throttle height, as detonation might not be a serious factor when you can't get full boost pressure up high. The charge cooling effect as well as the calorific value of the alcohol might warrant not switching it off directly upon reaching full-throttle height, but there's probably an altitude above which you'd decide to consider it uneconomic to keep it running.Regards,Henning (HoHun)</blockquote>

[QUOTE="HoHun, post: 635875, member: 32143"] Hi, I can only speculate. Overheating would seem like a possiblity, as air-cooled engines have a hard time getting rid of heat at high altitudes. Another possible reason for the power reduction might be a deliberate reduction in engine speed to keep the propeller tip Mach number down, in order to keep compressiblity-induced efficiency losses at a tolerable level. If the Ha-43 versions in question use water-methanol at the indicated power, it could also be a question of switching anti-detonant injection off above full throttle height, as detonation might not be a serious factor when you can't get full boost pressure up high. The charge cooling effect as well as the calorific value of the alcohol might warrant not switching it off directly upon reaching full-throttle height, but there's probably an altitude above which you'd decide to consider it uneconomic to keep it running. Regards, Henning (HoHun) [/QUOTE]

Verification