(5) Each airplane with sea level or altitude engine(s) using fuel
injection systems having metering component on which impact ice may
accumulate has a preheater capable of providing a heat rise of 75° F. with
the engine is operating at 75 percent of its maximum continuous power; and

Bill,

 

Thanks for the great information on the minimum rise for alternate air for Part 23 certified airplanes ( I copied back the part of 23.1093 that pertains to Bendix injected, front servo mounted Lancair 235/320/360s).  From data I recently gathered on my airplane, I am sure that the system John Huft described would meet the minimum.  As a matter of fact, the system is better than alternate air being selected from a cold air source.

 

Now, all we need to know is, what is the maximum rise or absolute induction air temp to prevent detonation if such a system is activated at OATs greater than 30F and greater than 75% power.