Quote:
Originally Posted by Fly_Unity  You would probaly get a better Fuel and time econamy if you climb at around 100 KTS 25/25, vs the 88kts-full/2700 |
What's time economy? Assuming that's the quickest trip, that will occur at the highest power settings, assuming it doesn't make you stop for fuel.
As for fuel economy, it's unlikely that the 25/2500 is optimal for any particular trip, except for coincidence. As the aircraft approaches its absolute ceiling for any particular power setting, the time to climb rises exponentially. Without running any numbers, it seems intuitive that there is a point where less fuel would be burned to climb at a higher power setting and actually arrive at the cruise altitude whereupon the aircraft could accelerate to cruise speed and complete the trip in less time.
Even prior to that point, the increased fuel burn rate is at least partially offset by smaller amount of time spent in climb and a sooner and quicker acceleration to cruise speed. An additonal factor in FT operation is the appropriate leaning for climb, once it's possible to do that, generally less than 75% power. At low altitudes, the power enrichment system can dramatically increase fuel flows for a given power setting.
The "piper recommended" 25/2500 is, most likely, purely arbitrary and not something the engineers calculated. I mean, how likely is it that the "best" power setting would work out to something so symmetrical and beautiful as 25/2500? These kind of suggested power settings generally state it's for the best combination of forward visibility, engine cooling, fuel flow, forward speed, but there really is no way to objectively optimize that diverse set of criteria. The right configuration will depend on the pilot value judgements.