Re: 112 Hot Shot
Reducing power to 26 squared (or the "oft heard" 25 squared) reduces your climb power dramatically, resulting in longer times to climb, and more time with the engine at it's worst "heat producing" stage.
25 Squared gives you only 78% of your engine's maximum power. Similarly, 26 Squared reduces power to about 85% of max HP. And since rate of climb is a direct function of the available power ABOVE what is required to cruise at that airspeed, you could be cutting your ROC by a significant factor. You spend longer at a high power setting to get to cruise altitude, and you spend more time climbing at reduced airspeed before establishing cruise. The end result is that you reach cruise altitude later, further toward your destination, and you wind up burning more fuel for the flight.
The APS guys recommend full power climbs all the way to cruising altitude, possibly with RPM reduced to 2500 at 1000 AGL if you're near a noise-sensitive area (and where in the US would you NOT be near a noise-sensitive area?)... Reducing from 2700 to 2500 RPM costs you appx 5% power, while significantly reducing the noise signature. They also recommend that you lean every few thousand feet to maintain the "target EGT" (next paragraph explains) established for your engine. You don't have to fixate on this, just wait until it drops 50-100 degrees, and lean it back to the target.
"Target EGT" is basically the EGT that you read from your EGT gauge when you apply full power (max MP and max RPM) at sea level in your airplane. Let's assume for the sake of discussion that this was 1350. As you climb, the EGT will slowly fall as the mixture becomes overly rich (thinner air). Leaning the mixture to regain your 1350 "target EGT" will keep you well on the rich side of peak, but also keep the engine producing close to maximum power. This is not a "super precision" exercise, so if you're at 500 MSL at your home airport, it is probably good enough.
This technique also solves the problem of knowing how much leaning is required at high-altitude airports, such as the one described earlier in this thread. If you lean the engine prior to takeoff to attain the target EGT (1350 in our hypothetical situation), your engine would be producing very close to the maximum power available at that airport under those conditions.
(If your airplane has a TIT gauge, you can use TIT instead of EGT for this "target" figure, and lean to the target TIT.)
