Operational Ceiling for Aircraft

[el cid again]

After reviewing data, the following rules of thumb seem to work fairly well: [Modified after conversion of many planes and testing]

The Optimum Operating Altitude of an aircraft is a function of its engine type and its service ceiling. [The service ceiling is the altitude at which an aircraft climbs only 100 feet per minute, or 30 meters per minute. Above this altitude the danger of a stall is excessive. When approaching this altitude, an aircraft's performance declines, and it is not truly maneuverable in a military sense unless significantly below that altitude.]

OOA for ordinary piston engines: 60% of Service Celiing
OOA for turbosupercharged piston engines: 80% of Service Ceiling.
OOA for jet and rocket engines: 90% of Service Ceiling.

My proposed rule of thumb for Operational Ceiling is "halfway between OOA and Service Ceiling." On that basis, the OC becomes:

OC for ordinary piston engines: 80% of Service Ceiling
OC for turbosupercharged piston engines: 90% of Service Ceiling.
OC for jet or rocket engines: 95% of Service Ceiling.

This almost works. No such simplistic models can get the data right for all cases. In this case, I use the initial raid on Clark AAF as the standard. The 75mm AAA has a reach of 22,600 feet. The bombers came in at 25,000 feet. By these rules of thumb, the bombers cannot quite reach 25,000 feet. But the G4s and Ki-21s can come in above the AAA, although the G3s cannot (they miss fy a few feet). I do not demand perfection of rules of thumb - just that they be generally correct and close - and these seem to be. Under these rules, the Frank can barely exceed 34,000 feet and be combat effective - which is correct. [It was an 'unpleasant surprise' for B-29s operating at 32,000 feet]. And a B-17 can only reach about 29,600 feet - in practical terms - 4/5 of its service ceiling. There are some fighters that reach this altitude - and some that don't - many have practical (what I am calling operational) ceilings in the range 24,000-29,000 feet. Similarly, some heavy AAA can reach these altitudes - mainly 4.7, 5 and 5.26 inch guns - and most of the 75s and 76s cannot. And of course flying this high makes the chances of a bomb hit go way down. But SOME planes can try to come in above the defenses in SOME situations. Other planes lack the performance to do so. As it should be. And a Ki-46 operating at full altitude is very hard to intercept - few fighters are effective way up there.